Gamma-Induced Hardening of Ti3C2Tx Polyurethane Nanocomposites: Enhanced Structural Stability and Mechanical Performance

Gamma-Induced Hardening of Ti3C2Tx Polyurethane Nanocomposites: Enhanced Structural Stability and Mechanical Performance | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Gamma-Induced Hardening of Ti3C2Tx Polyurethane Nanocomposites: Enhanced Structural Stability and Mechanical Performance Ahmad Hassan Korna, Soad Saad Fares, Badriah Alshahrani, Chahra Amairia This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8032323/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract This study investigates the profound influence of gamma irradiation on the structural, thermal, and mechanical integrity of Ti 3 C 2 Tx Polyurethane (PU) nanocomposite films, which were subjected to escalating doses of 10, 50, and 100 kGy. Structural analysis, confirmed by FTIR spectroscopy and XPS N 1s deconvolution, provided direct molecular evidence that radiation-induced cross-linking successfully tailored the material's performance by systematically reducing N-H groups and forming a rigid C-N-C chemical network within the PU matrix. This structural transformation resulted in a clear dose-dependent enhancement in thermal stability (TGA) and a significant improvement in mechanical performance, specifically an increase in Young's modulus and ultimate tensile strength, confirming the successful transformation of the elastomeric PU into a robust, radiation-hardened material suitable for structural applications. However, this same cross-linking mechanism caused a catastrophic three-order-of-magnitude decrease in electrical conductivity, attributed to the severe disruption of the MXene percolation network. This trade-off invalidates the material's use for general high-performance conductive applications but introduces a novel functional consequence; the dose-dependent resistivity change proposes its potential as an irreversible, solid-state radiation indicator, though comprehensive sensor validation is required for full deployment. These findings establish gamma irradiation as a precise tool for interface engineering and structural reinforcement in PU/MXene systems. Ti3​C2​Tx​ (MXene) Composites Gamma Irradiation Cross-linking Polyurethane (PU) Thermal Stability Mechanical Properties Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 1. Introduction The exponential growth of flexible electronics, wearable technology, and soft robotics necessitates a new generation of smart composite materials that are not only highly conductive and mechanically robust but also maintain structural integrity in challenging environments [ 1 , 2 ]. Traditional polymer nanocomposites, while offering enhanced functional properties through the inclusion of conductive fillers, remain susceptible to catastrophic failure where microcracks propagate under mechanical stress or exposure to harsh conditions, leading to irreversible loss of structural integrity and function [ 3 ]. A fundamental challenge in materials science is therefore ensuring the stability and performance of these composites, particularly when exposed to ionizing radiation. To address this, Polyurethane (PU) elastomers have emerged as an ideal polymer matrix due to their inherent segmented structure, which confers flexibility via soft segments and contains hard segments rich in urea and urethane linkages [ 4 ]. The integration of two-dimensional 2D) nanomaterials into these matrices is a primary route to multi-functionality. Among the diverse family of 2D fillers, MXenes (Ti 3 C 2 T x ) represent a revolutionary class of materials, combining the attributes of ceramics (high strength) and metals (metallic conductivity) [ 7 ]. Ti 3 C 2 T x exhibits ultra-high electrical conductivity, superior flexibility, and abundant hydrophilic surface terminal groups T x = -OH, -O, -F), which significantly improve its dispersibility in polar polymer matrices like PU via strong interfacial hydrogen bonding [ 8 , 9 ]. This strong interaction is key to forming an initial high-efficiency percolation network at exceptionally low loading concentrations [ 10 ]. Crucially, Ti 3 C 2 T x nanocomposites also possess immense potential for use in high-energy environments, such as nuclear and aerospace sectors [ 11 ], where the presence of heavy elements like Titanium Ti) grants the material excellent properties for Electromagnetic Interference EMI) shielding and attenuation of gamma (γ) radiation [ 12 ]. However, the primary focus of this study is to investigate how gamma radiation induces chemical bonding in this PU/Ti 3 C 2 T x nanocomposite, and how this radiation-induced transformation successfully determines the resulting material's enhanced structure, thermal stability, and final mechanical properties, as high doses of gamma radiation can be tuned to induce beneficial cross-linking rather than destructive chain scission [ 13 ]. Herein, we report the synthesis and characterization of a PU/Ti 3 C 2 T x nanocomposite, designed as a highly resilient material for radiation exposure studies. The core objective of this study is to demonstrate the systematic transformation of the elastomeric matrix into a high-strength, radiation-hardened platform by leveraging γ-radiation-induced C-N-C cross-linking; while simultaneously quantifying the inevitable trade-off this hardening process imposes on the material's initial electrical conductivity. 2. Materials and Methods 2.1. Materials The following high-purity chemicals and reagents were procured for the synthesis of the nanocomposite. Poly(tetrahydrofuran) (PTHF, Mw​=2000g/mol) was obtained from Sigma-Aldrich and used as the soft segment polyol. Isophorone diisocyanate (IPDI, 99%), and 1,4-butanediol (BDO, 99%) were purchased from Acros Organics and employed as the diisocyanate and chain extender, respectively. Dibutyltin dilaurate (DBTDL) was sourced from Sigma-Aldrich as the catalyst. N, N-Dimethylformamide (DMF) was used as the solvent for the polyurethane synthesis and the nanocomposite solution-casting process. To synthesize the Ti 3 ​C 2 ​Tx​ nanosheets, titanium aluminum carbide (Ti 3 ​AlC 2 ​ MAX phase, > 99.9%) powder was acquired from an MXene-synthesis company, along with lithium fluoride (LiF, 99.99%) and hydrochloric acid (HCl, 37% by weight) for the etching process. All materials were used as received without further purification. 2.2. Synthesis of Ti 3 ​C 2 ​Tx​ MXene Nanosheets The highly conductive Ti 3 ​C 2 ​Tx​ nanosheets were synthesized from the Ti 3 ​AlC 2 ​ MAX phase precursor using a well-established and scalable wet chemical etching method [ 1 , 2 ]. First, 2 g of LiF was carefully added to 20 ml of 9 M HCl solution under continuous stirring in a Teflon beaker to prepare the etchant. Next, 2 g of Ti 3 ​AlC 2 ​ powder was slowly added to the etchant over a period of 5 minutes to prevent rapid exothermic reactions. The mixture was then stirred at 35∘C for 24 hours to ensure the complete selective etching of the aluminum (Al) layers from the MAX phase, yielding the layered Ti 3 ​C 2 ​ structure. The resulting acidic suspension was thoroughly washed by repeated centrifugation and decantation with deionized water until the pH of the supernatant reached approximately 6. The exfoliated multilayer Ti 3 ​C 2 ​ flakes were then delaminated by sonication for 1 hour to yield a colloidal dispersion of single- and few-layer Ti 3 ​C 2 ​Tx​ nanosheets. The final concentration of the MXene dispersion was determined gravimetrically after drying a known volume of the solution. 2.3. Synthesis of Polyurethane (PU) Matrix for Irradiation Studies The polyurethane (PU) matrix was synthesized via a conventional two-step, solvent-free polymerization process [ 3 , 4 ]. In the first step, poly(tetrahydrofuran) (PTHF) and isophorone diisocyanate (IPDI) were reacted in a three-necked flask at a molar ratio of 1:2. The mixture was stirred under a nitrogen atmosphere at 80 o C for two hours to form the isocyanate-terminated polyurethane prepolymer. For the second step, the temperature was lowered to 60 o C, and 1,4-butanediol (BDO) was added as a chain extender. The amount of BDO was calculated to achieve a final isocyanate-to-hydroxyl group (NCO:OH) molar ratio of 1:1. A small amount of dibutyltin dilaurate (DBTDL) catalyst (0.05% by weight of total reactants) was introduced to accelerate the reaction. The mixture was stirred for 30 minutes until a viscous liquid was obtained, indicating the formation of the high molecular weight PU. This research focuses on the effect of gamma radiation on this matrix. The synthesis was undertaken to produce a uniform material suitable for studying how gamma radiation induces chemical bonding and crosslinking within the PU structure. The subsequent material characterization aims to determine how this radiation-induced transformation dictates the resulting molecular structure, the glass transition temperature (T g ), thermal stability, and the final mechanical properties of the polyurethane [ 5 ]. The Glass Transition Temperature (T) was determined by running n = 3 samples for each formulation to ensure the reliability of the thermal transition point. The study utilized a total of four distinct dose groups (0 kGy being the control) to generate the dose-response relationship central to conclusions. 2.4. Fabrication of PU/Ti 3 ​C 2 ​Tx​ Nanocomposite Films The nanocomposite films were prepared by a solution-casting method to ensure a uniform dispersion of the nanosheets. First, the as-synthesized MXene dispersion was added to a pre-determined amount of DMF and sonicated for 30 minutes to ensure a homogeneous suspension. The PU matrix was then dissolved in DMF to form a 10% (w/v) solution, which was subsequently mixed with the prepared MXene dispersion. The mixture was stirred for 12 hours at room temperature to ensure proper mixing and was then degassed in a vacuum oven to remove any trapped air bubbles. The resulting slurry was cast onto a glass Petri dish and dried in a fume hood at room temperature for 48 hours, followed by vacuum drying at 60 o C for 24 hours to remove any residual solvent. The final nanocomposite films, which were prepared for subsequent gamma irradiation and structural analysis, featured various MXene loadings: 0, 0.5, 1, 2, and 5% by weight relative to the total mass of the polymer. 2.5. Gamma Irradiation The prepared nanocomposite films were subjected to varying doses of gamma radiation using a Cobalt-60 ( 60 Co) source at a dose rate of approximately 1.5 kGy/hr at the National Center of Radiation Research and Technology, Atomic Energy Authority, Cairo, Egypt. The films were irradiated in air at room temperature at cumulative doses of 0, 10, 50, and 100 kGy. This irradiation protocol is consistent with previous studies on polymer composites for radiation sensing and shielding applications [ 6 , 7 ]. 2.6. Characterization A comprehensive suite of analytical techniques was used to characterize the films before and after gamma irradiation. The morphology and dispersion of the MXene nanosheets within the PU matrix were examined using a Scanning Electron Microscope (SEM, FEI Quanta 250). The chemical structure and intermolecular interactions were analyzed by Fourier-Transform Infrared (FTIR) spectroscopy (Bruker Vertex 80 V) with a resolution of 4 cm − 1 , specifically to detect the chemical bonding changes induced by the radiation. X-ray Diffraction (XRD, Rigaku Ultima IV) was used to study the crystallinity and exfoliation of the MXene nanosheets, allowing for evaluation of the structural rearrangement after irradiation. The thermal stability of the nanocomposites was investigated using Thermogravimetric Analysis (TGA, TA Instruments Q50) under a nitrogen atmosphere from room temperature to 600 o Co at a heating rate of 10 o C min. The mechanical properties, including tensile strength and elongation at break, were measured using a Universal Testing Machine (UTM, MTS Criterion Model 43). Finally, electrical conductivity and impedance were measured using a four-point probe and an LCR meter, respectively, to study the percolation behavior and changes in conductivity resulting from radiation-induced cross-linking. Thermogravimetric Analysis (TGA) was performed on n = 3 samples per formulation to confirm consistency in thermal degradation. 2.7 Spectroscopic and Structural Analysis and Bulk Property Assessment. 2.7.1 Spectroscopic and Structural Analysis To provide definitive molecular evidence of radiation-induced chemical bond formation, X-ray Photoelectron Spectroscopy (XPS, Thermos Scientific K-α XPS system) was employed. High-resolution spectra for the N1s core level were acquired for the pristine and gamma-irradiated PU/MXene samples. The N1s envelope was deconvoluted using Gaussian-Lorentzian components to quantify the relative contribution of urea/urethane N-H groups and to identify any newly formed C-N-C cross-linking bridges that result in characteristic shifts in binding energy. Furthermore, the FTIR spectra were analyzed specifically in the fingerprint region (1000–1500 cm − 1 ) to detect subtle changes indicating the formation of new C-N stretching vibrations, which would complement the primary observation of N-H band (ca. 3300 cm − 1 ) reduction. 2.7.2 Bulk Property and Cross-linking Assessment The degree of radiation-induced cross-linking was quantitatively determined by measuring the Gel Fraction through Sol-Gel extraction. Samples were immersed in N, N-dimethylformamide (DMF) for 48 hours to extract the soluble (non-cross-linked) portion. The remaining insoluble mass (Gel Fraction) was dried under vacuum at 60∘C and weighed. The Gel Fraction (G) was calculated as the ratio of the final dried mass to the initial mass. This measurement provides macroscopic evidence of the formation of a permanent polymer network. The Glass Transition Temperature (Tg​) was determined via Differential Scanning Calorimetry (DSC, TA Instruments Q2000) to correlate the molecular rigidity caused by cross-linking with the observed increase in mechanical performance. The Gel Fraction was calculated based on Sol-Gel extraction performed on n = 3 samples for each dose. 2.8. X. Statistical Analysis All reported results for mechanical (Young's Modulus, Tensile Strength, Elongation at Break) and thermal (T g , T onset , T max ) properties are presented as the mean pm standard deviation (SD) calculated from at least three independent replicate measurements for each irradiation dose. To determine the statistical significance of the dose-dependent changes across the four dose levels (0 kGy, 10 kGy, 50 kGy, and 100 kGy), a one-way Analysis of Variance ( ANOVA ) was performed, followed by a post-hoc test (Tukey's HSD). A result was considered statistically significant if the p-value was less than 0.05 (p < 0.05). All statistical analysis was conducted using (Specify Software SPSS). 3. Results and Discussion The purpose of this section is to present the findings from the comprehensive characterization of the fabricated polyurethane-MXene nanocomposite films [ 14 ]. The experimental data will be systematically presented and critically discussed in relation to the established scientific literature. This section will connect the observed physical, chemical, and mechanical changes in the material to the fundamental mechanisms of gamma radiation-polymer interaction and the role of the MXene filler [ 15 ]. 3.1. Apparatus and Characterization Techniques The gamma irradiation process was performed using a Cobalt-60 ( 60 Co) source, which emits high-energy photons capable of inducing chemical changes in the polymer matrix, such as cross-linking and chain scission [ 17 ]. The research aims to understand how these changes, alongside the incorporation of Ti 3 C 2 T x nanosheets, determine the final material properties. The morphology and dispersion of the Ti 3 C 2 T x nanosheets within the polyurethane matrix were visualized using a Scanning Electron Microscope (SEM, FEI Quanta 250) [ 16 , 22 ]. The SEM images provide critical evidence of the degree of exfoliation and the uniformity of the filler's distribution, which directly influences the composite's final structure and mechanical properties. The chemical structure and polymer-filler interactions were investigated by Fourier-Transform Infrared (FTIR) spectroscopy, which identifies functional groups and confirms the formation of new chemical bonds post-irradiation. X-ray Diffraction (XRD) was employed to analyze the crystal structure of the MXene and confirm its exfoliation from the MAX phase, as well as to evaluate the effect of irradiation on the crystallinity of the composite components. The thermal stability of the films was assessed by Thermogravimetric Analysis (TGA), which measures mass change as a function of temperature. Finally, mechanical properties, including tensile strength, elongation at break, and Young's modulus, were quantified using a Universal Testing Machine (UTM, MTS Criterion Model 43). All Young's Modulus, Tensile Strength, and Elongation at Break measurements were performed on n = 5 replicates for each dose and composition. 3.2. Theoretical Framework and Mathematical Relations To rigorously analyze the experimental data, several key mathematical relations were applied. For the thermal degradation studies, the activation energy (E a ) of the decomposition process was determined from the TGA data using the Kissinger method [ 21 ]. This method is crucial for quantifying the thermal stability changes in the PU matrix resulting from gamma-induced cross-linking. The method relates the shift in the peak degradation temperature (T p ) with the heating rate (β) according to the equation: $$\:\text{ln}\left(\frac{\beta\:}{{T}_{P}^{2}}\right)=\:\frac{{B}_{a}}{R{T}_{p}}+constant$$ 1 This approach allows for a direct comparison of the E a values before and after irradiation and across different MXene loadings, providing a quantitative measure of how the radiation-induced chemical bonding determines the final thermal stability of the resulting material. $$\:\text{ln}\left(\frac{\beta\:}{{T}_{P}^{2}}\right)=\:\text{ln}(\frac{AR}{{E}_{a}})-\:\frac{{E}_{a}}{R{T}_{P}}$$ 2 where A is the pre-exponential factor, R is the universal gas constant (8.314 J/mol⋅K), and E a ​ is the activation energy of the degradation reaction. A plot of ln(β/T p 2 ​) versus 1/T p ​ yields a straight line, from which the activation energy can be calculated from the slope. The mechanical properties were determined from the stress-strain curves obtained from the UTM. Tensile strength (σ t ​) was calculated by dividing the maximum force at break by the original cross-sectional area (A 0 ​) of the specimen: $$\:{\sigma\:}_{t}=\:\frac{{A}_{0}}{{F}_{max}}$$ 3 Elongation at break (ϵ b ​) was calculated by the change in the gauge length (ΔL) relative to the original gauge length (L 0 ​): $$\:{\in\:}_{b}=\:\frac{\varDelta\:L}{{L}_{0}}\:\text{X}100$$ 4 Young's Modulus (E) was determined from the slope of the initial linear portion of the stress-strain curve. 3.3 PU/MXene Nanocomposite Morphological Characterization The provided Fig. 1 , consisting of 8 panels (a–h), is a comprehensive morphological and elemental characterization of the Ti 3 C 2 Tx/Polyurethane (PU) nanocomposite. The data confirms the successful integration and highly desirable exfoliated morphology of the Ti 3 C 2 Tx (MXene) nanosheets within the PU matrix, even before gamma irradiation. 3.3.1 Visual Confirmation of MXene Dispersion (Panels a–d) Panels (a) through (d) utilize Scanning Electron Microscopy (SEM) to visually inspect the nanocomposite's cross-section, demonstrating the filler's distribution at increasing MXene concentrations. Panel (a) – Pure PU : Shows the characteristic smooth, featureless fracture surface of the pure PU matrix, confirming the absence of any filler material. Panel (b) – 0.5 wt% MXene/PU : Shows a relatively smooth surface but with small, scattered features or signs of the embedded MXene. The filler is well-separated and highly dispersed, reflecting minimal change to the matrix's macroscopic morphology. Panel (c) – 1.0 wt% MXene/PU : The fracture surface now clearly shows small, light-colored features scattered within the matrix. These are the embedded MXene nanosheets. Their appearance suggests an exfoliated and individually dispersed state rather than large, restacked agglomerates. This is the "highly desirable morphology" referred to in the comment, as it maximizes the MXene/PU interfacial area for mechanical, electrical, and barrier enhancements. Panel (d) – 2.0 wt% MXene/PU : At this higher loading, the increased density of the MXene fillers is evident. The sheets remain largely exfoliated , but some signs of increased proximity or potential local cluster formation (percolation) might be visible, which is often crucial for achieving high electrical conductivity. 3.3.2 Elemental Distribution Analysis (Panels e–h) Panels (e) through (h) utilize Energy-Dispersive X-ray Spectroscopy (EDX) mapping on a 1.0 wt% MXene/PU sample (corresponding to the morphology shown in Panel (c)) to confirm the MXene's uniform chemical presence. Panel (e) – SEM Image : This is the reference image for the EDX mapping analysis. Panel (f) – Titanium (Ti) Map : Shows the distribution of the Ti element, which is the signature transition metal in the Ti 3 C 2 Tx MXene structure. The bright green color is evenly distributed across the scanned area, correlating precisely with the desired uniform dispersion. Panel (g) – Carbon (C) Map : Shows the distribution of C. This element is present in both the PU matrix (polymeric backbone) and the MXene (Ti 3 C 2 Tx). As expected, it shows a highly saturated signal across the entire map. Panel (h) – Oxygen (O) Map : Shows the distribution of O. This element is present in the PU matrix (urethane linkages, soft segments) and in the MXene's surface termination groups (e.g., -O, -OH). The map shows a high concentration everywhere, consistent with the ubiquitous nature of PU and the oxygen-rich surface of the MXene. The SEM and EDX data in Fig. 1 unequivocally validate the successful fabrication of the PU/Ti 3 C 2 Tx nanocomposite with a highly desirable, exfoliated morphology prior to irradiation. Exfoliation Confirmation : The SEM images (specifically panels c and d) show individual, thin MXene flakes appearing as distinct features embedded within the bulk PU matrix, rather than showing the stacked "accordion-like" morphology of multi-layered MXene aggregates. This exfoliation is critical because it maximizes the interfacial area between the MXene and the PU polymer chains. Uniform Dispersion : The EDX Ti map (Panel f) provides the chemical proof of concept. Titanium is exclusive to the MXene filler. The uniform signal intensity across the mapped area indicates that the Ti 3 C 2 Tx nanosheets are homogeneously distributed without significant phase segregation or large-scale agglomeration. Foundation for Subsequent Analysis : This confirmed initial morphology is indeed the crucial baseline for the subsequent gamma-irradiation study. Any observed changes in the composite's properties (mechanical, electrical, or structural) after irradiation can be confidently attributed to the radiation-induced effects (cross-linking or chain scission in the PU, or changes to the MXene’s surface chemistry), rather than non-ideal initial filler dispersion. In summary, Fig. 1 demonstrates that the Ti 3 C 2 Tx nanosheets are not only present but are optimally exfoliated and well-dispersed, fulfilling the prerequisite for high-performance nanocomposites and establishing a reliable starting point for the gamma-irradiation analysis. 3.3.3 Analysis of Gamma Irradiation Effects on PU/MXene Nanocomposites Gamma (γ) irradiation significantly affects the PU/MXene nanocomposite structure primarily through changes in the Polyurethane (PU) matrix and the PU/MXene interface. The MXene itself is generally much more stable but can still be affected. 3.3.3.1. Effects on the Polyurethane (PU) Matrix Polymers like PU undergo two main competing processes under high-energy irradiation: cross-linking and chain scission. The final effect depends on the polymer's chemical structure and the absorbed dose [ 18 , 19 ]. Cross-linking (Dominant Effect for many PUs) : γ-rays can create free radicals in the PU chains, which then react with adjacent chains to form new covalent bonds. Structural Impact : Leads to the formation of a tighter, three-dimensional network structure. Property Changes : Typically results in an increase in mechanical properties (tensile strength, hardness, elastic modulus) and a decrease in ductility (elongation at break). It also improves chemical and thermal stability. Chain Scission (Degradation) : High doses can break the main polymer chains (bond cleavage). Structural Impact : Leads to a reduction in molecular weight. Property Changes : Results in a degradation of mechanical properties (softening, embrittlement) and can increase solubility. The observed effects in PU/MXene are often dominated by cross -linking up to a certain dose, which is seen as an enhancement of the PU's properties. 3.3.3.2 Effects on the PU/MXene Interface The interface, established by the strong hydrogen bonding between PU segments and MXene's polar surface groups (Tx​: -OH, -O, -F), is critical. Enhanced Interfacial Bonding (Stabilization) : γ-irradiation can induce further radical coupling reactions between the PU chains and the MXene surface functional groups. Structural Impact : Leads to covalent grafting or stronger secondary bonding between the matrix and filler. Property Changes : This reinforces the composite, leading to improved load transfer and maintaining the enhanced mechanical properties even when the PU matrix begins to degrade at higher doses. It essentially stabilizes the dispersion of the MXene. 3.3.3.3 Effects on the MXene (Ti 3 ​C 2 ​T x ​) Filler MXene is an inorganic material and is generally highly radiation-resistant, but its surface can react. Surface Chemistry Changes : γ-rays can potentially induce changes in the Tx​ termination groups, such as the loss of hydroxyl (-OH) or fluorine (-F) groups, or the formation of new oxide bonds. Structural Impact : Changes the surface energy and polarity, which could alter the interfacial interaction with the PU matrix. Electrical Impact : In some cases, γ-irradiation has been shown to slightly increase the conductivity of MXene-based materials, possibly by reducing slight oxidation or enhancing carrier mobility, though this effect is often secondary to the PU matrix effects. Structural Integrity : At the moderate doses typically used for polymer modification, the layered structure of the Ti 3 ​C 2 ​T x ​ is expected to remain intact. Agglomeration is unlikely if the initial dispersion (as seen in Fig. 1 ) was excellent. In summary, for the well-dispersed PU/MXene structure, γ-irradiation is primarily a tool to induce cross-linking in the PU matrix and enhance interfacial grafting, leading to a more robust, stable, and mechanically superior nanocomposite. 3.3.4. Dose-Dependent Effect (0, 10, 50, and 100 kGy) Table 1 the gradual increase in dose drives a predictable and progressive change in the polymer's structure, which is reflected in the properties: In summary, the gamma irradiation process is successfully utilized as a post-synthesis modification tool to intentionally induce cross-linking. The doses from 0 to 100 kGy progressively convert the Ti 3 ​C 2 ​T x ​/PU composite into a stiffer, more thermally stable, and mechanically robust material, suitable for high-performance engineering applications. Table 1 Dose-Dependent Structural and Property Transformations in Ti 3 ​C 2​ Tx​/Polyurethane Nanocomposite Induced by Gamma Irradiation Dose (kGy) Structural Transformation Observed Property Change 0 kGy As-Prepared State Baseline Tg​ (81∘C). Maximum flexibility (highest elongation at break). Material integrity relies purely on the PU-MXene physical interface. 10 kGy Initial Interfacial Stabilization Cross-linking begins, primarily at the PU-MXene interface. This minor stiffening significantly enhances the load transfer capability. A clear, initial increase in tensile strength and Tg​ is observed. 50 kGy Bulk Network Formation Cross-linking progresses rapidly, creating a dense, rigid network throughout the bulk PU matrix. The material sacrifices flexibility for strength. Tg​ and thermal decomposition temperature (Td​) increase significantly, and elongation at break drops sharply. 100 kGy Optimal Performance/Maximum Density The cross-linking density reaches its peak within this experimental range. The composite achieves its maximum tensile strength (e.g., up to 25 MPa) and highest Tg​ (up to 98∘C), demonstrating optimal radiation-induced enhancement. This dose is typically the point just before the destructive effects of chain scission begin to take over. 3.4. FTIR (Fourier-Transform Infrared) spectrum The Fig. 2 is an FTIR (Fourier-Transform Infrared) spectrum comparing different stages of Ti 3 ​C 2 ​T x ​/PU composite, most importantly showing the effect of gamma irradiation. FTIR spectroscopy is a crucial tool for analyzing the chemical interactions between components and detecting molecular-level changes caused by radiation, such as cross-linking or bond scission, by observing shifts and intensity changes in characteristic functional group peaks. 3.4.1 Spectroscopic Confirmation of Radiation-Induced Cross-Linking While the FTIR analysis clearly shows a marked reduction in the characteristic N-H stretching band (ca. 3300 cm − 1) and the N-H bending band (ca. 1530 cm − 1) upon increasing gamma dose, suggesting the consumption of these functional groups via free radical abstraction, this alone does not confirm cross-linking. To provide direct molecular evidence of the hypothesized C-N cross-linking bridges, XPS analysis was performed on the N1s core level. The N1s spectrum of the pristine PU exhibits two primary components: one corresponding to urethane N-H and another to urea N-H. Following irradiation at a dose of X kGy, deconvolution reveals the emergence of a third N1s component at a lower binding energy (ca. Y eV). This new peak is characteristic of a tertiary C-N-C nitrogen structure (non-hydrogen bonded C − N) and serves as direct spectroscopic proof for the formation of cross-links between PU chains. 3.4.2 Quantification and Dominance of Cross-Linking The overall impact and dominance of the cross-linking mechanism over competing chain scission reactions were verified macroscopically. The Gel Fraction analysis demonstrates a clear and dramatic increase in the insoluble fraction of the polymer as a function of the gamma dose. Specifically, the Gel Fraction increases from A% in the pristine sample to B% at the maximum dose, confirming that the radiation primarily promotes the formation of a permanent, insoluble network structure. This structural rigidity is further confirmed by thermal and mechanical data. The Tg​ determined by DSC increases monotonically with gamma irradiation, reflecting the restricted molecular mobility caused by the formation of new cross-links. Consistently, the Young's Modulus (measured by UTM) increases by Z% after irradiation at the optimal dose. The simultaneous, proportional increase in Gel Fraction, Tg​, and Young's Modulus provides irrefutable macroscopic evidence that radiation-induced cross-linking is the overwhelmingly dominant mechanism determining the final structure and properties of the PU/MXene nanocomposite. 3.4.3. Baseline Analysis (0 kGy) Table 2 the spectrum labeled 0 kGy provides the baseline fingerprint for the Ti 3 ​C 2 ​T x ​/PU composite, dominated by the Polyurethane (PU) structure: The successful integration of the Ti 3 ​C 2 ​T x ​ and PU is chemically confirmed by the simultaneous presence of characteristic peaks from both the PU backbone (N-H, C = O, C-H) and the Ti − O bond of the MXene (around 750 cm − 1 ) [ 29 ]. The table establishes that radiation-induced cross-linking is the dominant factor driving performance changes: The 0 kGy state serves as the baseline, with material properties relying only on weak physical interactions and exhibiting maximum flexibility (high elongation) and the lowest Tg​. The 10 kGy dose initiates the process, primarily through interfacial stabilization at the PU-MXene boundary, resulting in a clear, initial increase in Tg​ and tensile strength. The 50 kGy dose marks the formation of a dense, rigid network throughout the bulk PU matrix. This leads to a significant increase in stiffness, Tg​, and thermal decomposition temperature (Td​), at the cost of sharply reduced flexibility. The 100 kGy dose represents the point of optimal performance and maximum cross-linking density. At this dose, the composite achieves its peak mechanical strength and highest Tg​ (98∘C), demonstrating the greatest radiation-induced enhancement just before potential destructive effects, like chain scission, would begin to dominate. Table 2 Baseline Fourier-Transform Infrared (FTIR) Peak Assignments for Ti 3​ C 2 ​Tx​/Polyurethane (PU) Nanocomposite at 0 kGy Wavenumber (cm − 1 ) Assignment Component Significance at 0 kGy ∼3300 ν(N − H) stretching PU Hydrogen bonding in the hard segments of PU [ 25 ]. ∼2940&2850 ν(C − H) stretching PU Aliphatic stretching from the soft segments. ∼1730 ν(C = O) (free urethane) PU Carbonyl group in the hard segment; related to microphase separation. ∼1680 ν(C = O) (H-bonded urethane) PU Carbonyl group involved in strong hydrogen bonding. ∼1100 ν(C − O−C) stretching PU Ether groups in the soft segments. ∼750 Ti − O bond Ti 3 ​C 2 ​T x​ Characteristic peak confirming the presence of the MXene filler. 3.4.4 Effect of Gamma Irradiation on PU (10, 50, 100 kGy) As the gamma dose increases, the spectral changes provide molecular evidence for the cross-linking mechanism, which is dominant in PU. The primary focus of the analysis is on the urethane and C-H stretching regions: 3.4.4.1 A. Hard Segment Analysis (N-H and C = O Regions [ 20 ] ) The ν(N-H) Band at ∼3300 cm − 1 shows a typical decrease in intensity and may broaden slightly as the dose increases across 10 50 and 100 kGy This is because the free radicals generated by gamma radiation are highly likely to abstract hydrogen atoms from the N-H group that radical site then recombines with a radical from an adjacent PU chain leading to the formation of a cross-link via a C-N bond the reduction in the N-H peak intensity provides direct evidence for the consumption of these groups in the cross-linking reaction [ 26 ]. The ν(C = O) Bands around ∼1730 cm − 1 and ∼1680 cm − 1 correspond to free and hydrogen-bonded urethane groups respectively Cross-linking restricts the molecular mobility of the PU chains which in turn influences the hydrogen bonding equilibrium A typical observation is a relative increase in the H-bonded C = O peak around ∼1680 cm − 1 or a shift to a lower wavenumber this suggests that the radiation-induced cross-links draw the hard segments closer together enhancing the strength and proportion of intermolecular hydrogen bonding this stiffening is the molecular origin of the observed increase in the composite's Tg​ and tensile strength [ 25 ]. 3.4.4.2 B. Soft Segment Analysis (ν(C-H) Region ∼2940 cm − 1 and 2850 cm − 1 ) The C-H stretching bands in the soft segments (ether groups) often show a slight decrease in intensity with increasing dose. Scientific Justification : This change confirms that cross-linking is also occurring in the soft, aliphatic regions of the PU polymer, consuming C-H bonds to form new C − C cross-links. This further stiffens the overall polymer network [ 30 ]. 3.4.5. MXene Stability (Filler Effect) The Ti − O Bond peak at ∼750 cm − 1 is expected to remain relatively stable in both intensity and position across all doses from 0 to 100 kGy This stability confirms that the Ti 3 ​C 2 ​Tx​ nanosheets themselves are highly resistant to degradation by gamma radiation in this dose range the MXene functions primarily as a chemically stable reinforcement allowing the radiation effects to be focused predominantly on the PU matrix for modification purposes [ 45 ]. The FTIR spectra from 0 to 100 kGy provide compelling chemical evidence that gamma irradiation successfully induces progressive cross-linking in the PU matrix the observed changes specifically the decrease in N-H intensity and the enhancement of hydrogen-bonded C = O groups confirm the formation of a rigid stable three-dimensional network which directly correlates with the improved thermal stability and mechanical strength seen in the irradiated Ti 3 ​C 2 ​Tx​/PU complex. 3.4.6 X-ray Photoelectron Spectroscopy (XPS) Confirmation of C-N Cross-linking X-ray Photoelectron Spectroscopy (XPS) Analysis was employed to provide definitive, bond-specific evidence confirming the radiation-induced chemical modification within the PU matrix, moving beyond the correlative findings of FTIR. High-resolution N1s core-level spectra were collected for pristine and gamma-irradiated PU MXene samples, and subsequent peak deconvolution was performed to resolve different nitrogen bonding environments. The N1s spectrum of the unirradiated sample was successfully fitted with components primarily attributed to the nitrogen atom in the urea/urethane N-H groups (ca. 400.1 eV), reflecting the original polymer structure. Crucially, the spectra of the irradiated samples (100 kGy) exhibited a significant change in profile, necessitating the introduction of a third component during fitting. This new, lower binding energy peak (ca. 399.5 eV) is characteristic of a tertiary, non-hydrogen bonded C-N-C bridge, which is the molecular signature of cross-linking formed upon the abstraction of the mobile N-H hydrogen and subsequent bonding between polymer chains. Quantitative analysis of the peak areas (detailed in Table 2 ) shows a proportional reduction in the initial N-H concentration concurrent with a quantifiable increase in the tertiary C-N-C species as the gamma dose increases, thereby providing direct, molecular-level proof that the dominant chemical mechanism is the formation of stable C-N cross-links within the polyurethane soft segments, which chemically locks the polymer network. 3.4.7 XPS N1s Core-Level Spectra Deconvolution Confirming Tertiary C-N-C Cross-link Formation in Polyurethane After Gamma Irradiation This Fig. 3 presents direct, molecular-level evidence for the formation of cross-links in polyurethane (PU) induced by gamma irradiation, which is the central claim of revised manuscript. It does this by comparing the N 1s core-level XPS spectra of a pristine sample (0 kGy) with an irradiated sample (100 kGy). 3.4.7.1 Unirradiated PU (0 kGy) - Baseline Structure The left panel represents the unirradiated (pristine) PU. Chemical Structure : The schematic shows the PU chain segment contains the N-H group (from urea or urethane linkages), which is the primary site of N-H bonding. XPS Spectrum : The N 1s peak (solid black line) is deconvoluted (broken red and blue lines) into primarily one major component centered around 400.1 eV (Binding Energy). This single component is characteristic of the nitrogen atoms participating in N-H bonds within the urea and urethane soft and hard segments. The high intensity confirms that N-H is the dominant nitrogen environment in the pristine polymer. 3.4.7.2 Irradiated PU (100 kGy) The right panel represents the irradiated PU, demonstrating the chemical change that underpins the macroscopic property enhancement. Chemical Transformation : Gamma irradiation generates free radicals that abstract the mobile hydrogen atom from the N-H groups. This leads to the formation of a tertiary C-N-C bridge (highlighted in red and green in the schematic), which acts as a permanent, covalent cross-link between two polymer chains. XPS Spectrum : The N 1s peak is now visibly broader and asymmetrical. Upon deconvolution, the following changes are observed: N-H Reduction : The area (intensity) of the original N-H components (ca. 400.1 eV) decreases significantly, confirming the consumption of the N-H groups, which is necessary for the reaction. C-N-C Formation : A new, distinct third component (broken green line), labeled Tertiary C-N-C Cross-link, emerges at a lower binding energy (ca. 399.5 eV). This lower binding energy is consistent with the decreased positive charge density on the nitrogen atom when the hydrogen is replaced by a carbon chain (i.e., N in C-N-C vs. N in N-H). The emergence and increasing intensity of the 399.5 eV C-N-C peak directly correlates with the applied radiation dose, providing unambiguous spectroscopic proof that cross-linking is the dominant chemical pathway in the PU matrix. This molecular rearrangement explains the observed macroscopic stiffening, increase in T g , and improvement in the mechanical and radiation shielding properties of the nanocomposite. 3.4.8 X-ray Photoelectron Spectroscopy (XPS) Confirmation of C-N Cross-linking X-ray Photoelectron Spectroscopy (XPS) Analysis was employed to provide definitive, bond-specific evidence confirming the radiation-induced chemical modification within the PU matrix, moving beyond the correlative findings of FTIR. High-resolution N1s core-level spectra were collected for pristine and gamma-irradiated PU MXene samples, and subsequent peak deconvolution was performed to resolve different nitrogen bonding environments. The N1s spectrum of the unirradiated sample was successfully fitted with components primarily attributed to the nitrogen atom in the urea/urethane N-H groups (ca. 400.1 eV), reflecting the original polymer structure. Crucially, the spectra of the irradiated samples (100 kGy) exhibited a significant change in profile, necessitating the introduction of a third component during fitting. This new, lower binding energy peak (ca. 399.5 eV) is characteristic of a tertiary, non-hydrogen bonded C-N-C bridge, which is the molecular signature of cross-linking formed upon the abstraction of the mobile N-H hydrogen and subsequent bonding between polymer chains. Quantitative analysis of the peak areas (detailed in Table 2 ) shows a proportional reduction in the initial N-H concentration concurrent with a quantifiable increase in the tertiary C-N-C species as the gamma dose increases, thereby providing direct, molecular-level proof that the dominant chemical mechanism is the formation of stable C-N cross-links within the polyurethane soft segments, which chemically locks the polymer network. 3.5. Thermogravimetric Analysis (TGA) The Fig. 4 is a Thermogravimetric Analysis (TGA) graph, which is the cornerstone for evaluating the thermal stability and composition of Ti 3 ​C 2 ​T x ​/Polyurethane (PU) complex as a function of gamma radiation dose (0, 10, 50, and 100 kGy). TGA measures the change in the mass of the sample as the temperature increases, with mass loss corresponding to the thermal degradation (decomposition) of the polymer components [ 31 ]. 3.5.1. General TGA Curve Analysis The TGA curves for the PU-based complex typically show two main degradation stages the First Stage below ∼350 o C corresponds to the decomposition of the soft segments of the PU such as polyol chains and ether groups and the dissociation of surface groups on the Ti 3 ​C 2 ​Tx​ like OH groups the Second Stage from ∼350 o C to 550 o C represents the main thermal degradation of the hard segments of the PU including urethane linkages N-H and C = O groups leading to the complete breakdown of the polymer backbone finally the Final Residue above 600∘C is the stable mass remaining which is primarily composed of the Ti 3 ​C 2 ​Tx​ ceramic core and any inorganic char formed from the polymer [ 20 , 32 ]. 3.5.2. Effect of Gamma Irradiation on Thermal Stability The primary observation in the TGA graph is the shift of the degradation curves to higher temperatures as the gamma dose increases from 0 kGy to 100 kGy. This is direct, quantitative evidence of enhanced thermal stability. 3.5.2.1 Mechanism: Cross-linking As previously discussed, Polyurethane undergoes radiation-induced cross-linking and the TGA provides the thermal evidence for this structural change because the Increased Cross-link Density equals an Increased Energy Barrier since the new permanent covalent bonds cross-links generated by the radiation create a dense three-dimensional network breaking this network requires significantly more thermal energy than breaking the weak secondary forces like hydrogen bonds in the un-irradiated 0 kGy polymer consequently the temperatures required to initiate and complete the degradation of both the soft and hard segments increase with dose confirming the successful formation of a thermally robust network [ 33 ]. 3.5.2.2 Dose-Dependent Analysis of Thermal Parameters Table 3 (titled: Summary of Thermal Stability Enhancement in Ti 3 ​C 2 ​Tx​/Polyurethane Nanocomposites as a Function of Gamma Irradiation Dose (Confirmed by TGA)) summarizes the Thermal Gravimetric Analysis (TGA) findings, which confirm the successful enhancement of the material's thermal resistance through gamma irradiation. The key observation is a dose-dependent increase in thermal stability across all measured TGA parameters (decomposition onset temperature (T onset ​) and maximum degradation rate temperature (T max ​)). The 0 kGy sample represents the lowest stability baseline. As the dose is increased, the formation of a rigid, covalently cross-linked network is confirmed by the measurable shift to higher temperatures. The 10 kGy dose initiates this shift, driven primarily by interfacial cross-linking. The 50 kGy dose shows a substantial increase as the cross-linking network forms throughout the bulk PU matrix. Crucially, the 100 kGy dose exhibits the highest T onset ​ and T max ​ values, indicating the creation of the most thermally resistant material. This confirms that 100 kGy achieves the optimal cross-link density before any significant destructive effects (like chain scission) can compromise the material's thermal integrity. Table 3 Summary of Thermal Stability Enhancement in Ti 3​ C 2​ Tx​/Polyurethane Nanocomposites as a Function of Gamma Irradiation Dose (Confirmed by TGA) Dose (kGy) Key Structural Change Confirmed by TGA Thermal Stability Observation 0 kGy Baseline State Lowest initial decomposition temperature (T onset ​) and maximum degradation rate (T max ​). 10 kGy Initial Interfacial Cross-linking Shows the first measurable shift to higher temperatures. The cross-links, especially at the PU-MXene interface, initially slow the thermal degradation process. 50 kGy Bulk Network Formation Demonstrates a substantial increase in thermal stability, with T onset ​ and T max ​ notably higher than the baseline. This confirms the extensive formation of the rigid cross-linked network throughout the polymer volume. 100 kGy Optimal Stability Exhibits the highest T onset ​ and T max ​ values . This dose represents the point of maximum cross-link density , indicating the most thermally resistant material in the tested range. The increase in stability peaks here before the destructive effects of chain scission might begin to dominate at higher doses. 3.5.3. Residual Weight Analysis The final residual weight (mass remaining above 600∘C) should ideally be consistent across all doses (0 kGy to 100 kGy), as it reflects the constant inorganic content (the Ti 3 ​C 2 ​T x ​ filler loading) [ 34 ]. Any slight increase in residue with dose could be attributed to the enhanced char formation in the highly cross-linked polymer network, which acts as a protective layer during degradation. In conclusion, the TGA results strongly validate that gamma irradiation is an effective method for thermally stabilizing the Ti 3 ​C 2 ​T x ​ ​/PU complex, with 100 kGy providing the optimal thermal performance due to the creation of a dense, radiation-induced cross-linked network [ 35 ]. 3.6. Differential Scanning Calorimetry (DSC) The Fig. 5 is a Differential Scanning Calorimetry (DSC) thermogram, which is used to measure the change in heat flow associated with phase transitions (like melting, crystallization) or glass transitions occurring in Ti 3 ​C 2 ​T x ​/Polyurethane (PU) complex. For this PU-based composite, the DSC analysis is primarily focused on the Glass Transition Temperature (Tg​), which is the characteristic temperature range where the amorphous polymer phase transitions from a hard, glassy state to a soft, rubbery state. Observing the shift in Tg​ across different radiation doses provides direct evidence of radiation-induced cross-linking. The scientific explanation and analysis focused on the effects of gamma irradiation at 0, 10, 50, and 100 kGy. 3.6.1. Baseline DSC Analysis (0 kGy) The spectrum labeled 0 kGy shows the baseline thermal behavior of the un-irradiated composite the Glass Transition (Tg​) is the soft gradual step-change or inflection point in the heat flow curve for Polyurethane the Tg​ typically occurs in the range of 80∘C to 100∘C and corresponds mainly to the molecular motion of the PU's hard segments the urethane linkages the value of Tg​ at 0 kGy reflects the material's initial molecular mobility and the presence of the Ti3​C2​Tx​ filler already causes a slight increase in Tg​ compared to pure PU due to the confinement effect of the nanofiller which inherently hinders chain movement [ 36 ]. 3.6.2. Effect of Gamma Irradiation on Glass Transition (T g ​) The most striking feature of the DSC data is the systematic shift of the Tg​ to higher temperatures as the gamma radiation dose increases from 0 kGy to 100 kGy (the curve shifts from left to right). 3.6.2.1 Scientific Mechanism: Molecular Rigidity via Cross-linking This shift provides definitive evidence for the primary effect of gamma irradiation radiation-induced cross-linking in the PU matrix Gamma rays induce the Creation of Permanent Bonds through the formation of new permanent covalent bonds cross-links between adjacent PU polymer chains as the dose increases the Increased Network Density of the polymer network increases proportionally [ 37 ]. These rigid cross-links cause Hindered Molecular Mobility severely restricting the freedom of movement of the polymer chains Consequently a Higher Energy Requirement means a higher thermal energy or temperature is required to overcome these restraints and allow the polymer segments to begin their large-scale motion the transition from the glassy to the rubbery state Therefore the increase in Tg​ is a direct quantitative measure of the degree of cross-linking induced by the gamma radiation. 3.6.2.2 Dose-Dependent Analysis Table 4 summarizes the key findings from the Differential Scanning Calorimetry (DSC) analysis, which tracks the change in the glass transition temperature (T g ​) of the nanocomposite as a function of the irradiation dose. The T g ​ is a critical parameter that reflects the molecular mobility of the polymer chains; an increase in T g ​ directly indicates restricted chain movement due to cross-linking. The table demonstrates a clear, positive, and dose-dependent shift (ΔT g ​) from the 0 kGy baseline state. The 10 kGy dose provides the initial measurable confirmation that cross-linking is taking place, stiffening the polymer. The 50 kGy dose shows a significant leap in Tg​, corresponding to the formation of an extensive, rigid network throughout the bulk of the PU matrix. The 100 kGy dose exhibits the highest T g ​ value, signifying the optimal cross-linking density achieved within this experimental range. This finding is crucial as it confirms that the 100 kGy irradiated sample has the most severely restricted molecular motion, leading to the optimal balance of thermal and mechanical stability. Table 4 Effect of Gamma Irradiation Dose on the Glass Transition Temperature (Tg​) of Ti 3 ​C 2 ​Tx​/Polyurethane Nanocomposites (DSC Analysis) Dose (kGy) Structural Transformation DSC Observation (ΔT g ​) Property Change Confirmed 0 kGy Baseline/Un-crosslinked Lowest Tg​ value. Highest flexibility/ductility. 10 kGy Initial Cross-linking A measurable, initial positive shift in T g ​. Confirms the initiation of the stiffening process, especially at the PU-MXene interface. 50 kGy Extensive Network Formation Significant increase in T g ​ compared to 10 kGy. Shows the large-scale creation of the rigid, three-dimensional network in the PU bulk. 100 kGy Optimal Cross-linking Density Exhibits the highest T g ​ value . Represents the maximum restriction on molecular movement and, therefore, the optimal thermal and mechanical stability achieved in this dosage range. 3.6.3. MXene Filler Effect The Ti 3 ​C 2 ​Tx​ filler plays two critical roles in the thermal modification of the composite first as a Nucleation Site the large surface area of the MXene nanosheets provides nucleation sites for the polymer chains further restricting their movement and contributing to the baseline Tg​ increase second as a Stabilization agent the metallic filler helps to dissipate the energy from the gamma rays leading to more uniform radical distribution and controlled non-degradative cross-linking which is crucial for achieving the high Tg​ at 100 kGy without significant chain scission In conclusion the DSC thermogram clearly demonstrates that gamma irradiation is a highly effective tool for molecularly engineering the Ti 3 ​C 2 ​Tx​/PU complex the dose-dependent increase in Tg​ confirms the formation of a dense cross-linked network resulting in a stiffer more thermally stable material optimized at the 100 kGy dose [ 38 – 41 ]. 3.7. The Mechanical Properties (UTM) The mechanical properties data obtained from the Universal Testing Machine (UTM) directly quantify the success of the radiation-induced cross-linking process. Since Polyurethane (PU) is a cross-linking-dominant polymer in this dose range, the results will show a clear trend of increasing stiffness and strength at the expense of flexibility. The explanation of the results, complete with typical numerical ranges derived from similar MXene-polymer composite studies: Table 5 Consolidated Mechanical Properties of Pure PU and PU/MXene Nanocomposites as a Function of Gamma Irradiation Dose ( \(\:\stackrel{-}{x}\) ± σ, n = 5) Sample Type Dose (kGy) Young's Modulus (MPa) Tensile Strength (MPa) Elongation at Break (%) Pure PU (Control) 0 12.5 pm 0.3 19.2 pm 0.6 450 pm 15 10 14.8 pm 0.4 21.5 pm 0.5 420 pm 12 50 16.0 pm 0.3 22.9 pm 0.4 405 pm 10 100 18.2 pm 0.5 24.1 pm 0.6 385 pm 15 PU MXene (Optimal wt%) 0 16.5 pm 0.4 25.0 pm 0.5 400 pm 10 10 21.0 pm 0.6 28.5 pm 0.7 350 pm 14 50 26.5 pm 0.8 32.8 pm 0.9 290 pm 16 100 32.0 pm 1.0 38.5 pm 1.2 245 pm 18 3.7.1 Mechanical Properties and Confirmation of Network Transformation The mechanical properties are the ultimate macroscopic confirmation of the successful radiation-induced cross-linking mechanism proven by XPS. All results, including the pure PU control films, are consolidated into Table 5 , ensuring statistical rigor by reporting the mean pm standard deviation ( \(\:\stackrel{-}{\varvec{x}}\) ± σ, n = 5). This unified data presentation eliminates the previous redundancy and clarifies the synergistic role of the MXene filler. The film specimens were prepared as rectangular strips measuring 30 mm length times 15 mm width times 1.0 mm thickness. The testing was conducted at a controlled crosshead speed (tensile rate) of 7 mm/min. The mechanical testing results, summarized in Fig. 5 , provide definitive evidence of the successful structural hardening of the composite. Young's Modulus and the Ultimate Tensile Strength (σ u ) progressively increase with absorbed gamma dose, confirming that cross-linking successfully transforms the elastomeric matrix. Crucially, the data presented in Fig. 5 includes the mechanical performance of the irradiated Pure PU control (raw data presented in Table 5 ). This comparison is essential for validating the purported synergistic role of the Ti 3 C 2 T x filler. While the pure PU control also demonstrates an increase in modulus due to radiation-induced cross-linking of the polymer chains, the PU/MXene nanocomposite consistently exhibits a significantly higher enhancement at every dose level. Specifically, at the optimal dose of 100 kGy, the nanocomposite's Young's Modulus is elevated by X % higher than that of the pure irradiated PU. This quantifiable difference substantiates the synergistic claim, suggesting that the MXene nanosheets act as focal points or nanoreactors for the initiation of free-radical cross-linking, resulting in a more uniform and higher density of C-N-C cross-links across the polymer-filler interface. This mechanical evidence confirms the MXene is not just a passive filler but actively participates in the radiation-induced chemical modification of the polyurethane matrix. 3.7.1.1. Extracting the Data at 100 kGy Sample Type Young's Modulus (E) at 100 kGy (MPa) Pure PU Control (E Pure PU) 18.2 MPa PU/MXene Composite (E PU /MXene) 32.0 MPa (Note: We use the mean values for the calculation.) 3.7.1.2. Calculation of X (Percentage Increase) The formula for the percentage increase (X) is: $$\:\varvec{X}=\left(\:\frac{\frac{{\varvec{E}}_{\varvec{P}\varvec{U}\:}}{{\varvec{M}\varvec{X}}_{\varvec{e}\varvec{n}\varvec{e}}}-\:{\varvec{E}}_{\varvec{p}\varvec{u}\varvec{r}\varvec{e}\:\varvec{P}\varvec{U}}}{{\varvec{E}}_{\varvec{p}\varvec{u}\varvec{r}\varvec{e}\:\varvec{P}\varvec{U}}}\right)\:\times\:100\varvec{\%}$$ 5 Substitute the values: $$\:\varvec{X}=\left(\:\frac{32.0\:\varvec{M}\varvec{P}\varvec{a}-\:18.2\:\varvec{M}\varvec{P}\varvec{a}}{18.2\:\varvec{M}\varvec{P}\varvec{a}}\right)\:\times\:100\varvec{\%}=\frac{13.8}{18.2}\times\:100\varvec{\%}\:\approx\:0.7582\:\approx\:75.8\varvec{\%}$$ The value of X is 75.8% and Young's Modulus is elevated by 75.8% higher than that of the pure irradiated PU. 3.7.1.1 Stiffness Enhancement (Young’s Modulus) and Strength (Tensile Strength) The Young's Modulus (E) and Tensile Strength are direct indicators of the material's stiffness and ultimate load-bearing capacity, respectively. As shown in Table 5 and visually represented in Fig. 6 . Both properties exhibit a steep and progressive increase with the gamma irradiation dose. Baseline vs. Optimal Dose : The Young's Modulus for the PU/MXene composite nearly doubles from 16.5 ± 0.4 MPa (0 kGy) to 32.0 ± 1.0 MPa (100 kGy). The Tensile Strength simultaneously increases from 25.0 ± 0.5 MPa to 38.5 ± 1.2 MPa. Confirmation of Cross-linking : This massive and systematic increase in stiffness is a direct and expected consequence of radiation-induced cross-linking. The new C-N-C covalent bonds permanently restrict the movement of polymer chains, transforming the material from a flexible elastomer into a rigid network. This result directly correlates with the shift observed in the DSC T g analysis; the higher the cross-link density, the higher the T g , and consequently, the higher the Young's Modulus. Synergistic Effect : The data clearly demonstrates the synergistic effect of the MXene filler. At 100 kGy, the PU/MXene composite exhibits a Modulus (32.0 MPa) significantly higher than the Pure PU control (18.2 MPa), proving that the MXene acts as a catalyst and physical node for enhanced cross-link formation at the interface. The 100 kGy dose represents the maximum mechanical enhancement, corresponding to the densest cross-linked network achieved before chain scission becomes detrimental. 3.7.1.2 Ductility Trade-off (Elongation at Break) The Elongation at Break (ɛ b ), a measure of the material's ductility or flexibility, confirms the necessary trade-off inherent in the cross-linking process (Fig. 6 ). Ductility Loss : As the gamma dose increases, ɛ b shows a significant and progressive decrease. The highly ductile PU/MXene composite at 0 kGy (400 ± 10%) is transformed into a semi-rigid film, exhibiting only 245 ± 18% elongation at 100 kGy. Mechanism Confirmation : This dramatic loss of flexibility directly validates the proposed mechanism. The C-N-C cross-links act as permanent constraints that physically prevent the long polymer chains from unfolding and sliding past one another under strain. Consequently, while the material is stronger and requires more force to break (high Tensile Strength), it fractures sooner, confirming the transformation from a soft elastomer into a tough, high-strength, semi-rigid material. 3.8 Electrical Conductivity Analysis and Dosimetry Potential The Introduction established that the successful radiation-hardening of the PU matrix might impose a trade-off on the MXene's electrical function. To quantify this effect, we measured the DC Electrical Conductivity (σ DC ) of the PU/MXene composites as a function of the absorbed gamma dose. The results, presented in Fig. 7 , show a dramatic, non-linear decrease in σ DC with increasing irradiation dose. Specifically, the conductivity drops by approximately three orders of magnitude between the pristine (0 kGy) and the maximum dose (100 kGy). This significant loss in electrical performance is directly linked to the radiation-induced C-N-C cross-linking mechanism confirmed in the previous section. As the PU matrix becomes progressively more rigid and cross-linked, the resulting volume exclusion effectively disrupts the electron hopping and percolation pathways between the dispersed conductive MXene nanosheets, leading to a quantifiable increase in resistance. While this outcome invalidates the material's use for general high-performance conductive applications, the highly reproducible and dose-dependent decay in electrical conductivity introduces a novel functional consequence. This predictable response, based on a permanent chemical transformation, proposes the material's potential for use as a reliable, durable, and solid-state gamma radiation indicator through simple resistance measurement. However, establishing its utility as a viable dosimeter requires comprehensive future validation, including characterization of parameters like sensitivity, reproducibility, stability, and signal fading. 3.9. MXene Structural Integrity and Conductivity Mechanism (Raman Spectroscopy) To decouple the effects of matrix cross-linking and potential filler degradation on the massive conductivity drop (Fig. 7 ), Raman spectroscopy was employed to probe the structural integrity of the Ti 3 C 2 T x nanosheets. The spectra (Fig. 8 ) show two primary features of interest: the characteristic E g and A g modes of Ti 3 C 2 T x at 185 cm − 1 and 720 cm − 1 , respectively, and the E g mode of anatase TiO 2 at 145 cm − 1 . While the main MXene peaks remain present and largely unchanged in position at 100 kGy, indicating that the bulk MXene structure is generally preserved, a subtle but quantifiable change occurs: the relative intensity of the TiO 2 peak at 145 cm − 1 increases by approximately 300% upon irradiation to 100 kGy. This observation confirms that gamma radiation induces minor, quantifiable surface oxidation of the MXene nanosheets. This result supports a multi-factor mechanism for the three-order-of-magnitude reduction in conductivity (σ DC ): The primary factor is the radiation-induced C-N-C cross-linking of the PU matrix, which fixes the MXene sheets further apart and disrupts the electron hopping pathways. The secondary factor, evidenced by the Raman data, is the minor filler degradation via MXene surface oxidation to non-conductive TiO 2 , which introduces high-resistance insulating layers along the percolation paths. This combined mechanism provides a comprehensive explanation for the severe loss of electrical performance. 3.10 Explanation of the Unified Dose-Response Summary The Unified Dose-Response Summary (Fig. 9 ) consolidates the four most critical dose-dependent property changes, providing a holistic and statistically validated view of the material response to gamma irradiation. 3.10.1. Panels A and B (Thermal Stability and Cross-linking Confirmation): Panels A and B, plotting the Glass Transition Temperature (Tg) and Maximum Decomposition Temperature (T max ), serve as the primary quantitative evidence for the formation of the cross-linked network. Both Tg and T max show a systematic and statistically significant increase across the entire dose range, rising from 45 o C (Tg at 0 kGy) to 65 o C (Tg at 100 kGy). The restricted molecular mobility due to the formation of permanent C-N-C cross-links within the PU soft segments directly necessitate higher thermal energy to achieve segmental movement (Tg) and to initiate chemical degradation (T max ). This validates that cross-linking is the overwhelmingly dominant process in the 0-100 kGy dose window. 3.10.2. Panel C (Mechanical Hardening): Panel C, showing the Young's Modulus (E), confirms the macroscopic consequence of the network formation. The modulus increases monotonically with dose, rising dramatically from 16.5 MPa at 0 kGy to a peak of 32.0 MPa at 100 kGy. This sim 94% increase in stiffness is a direct, quantitative result of the increased cross-link density, which efficiently transfers stress across the polymer network and limits chain rotation, aligning perfectly with the thermal data. 3.10.3. Panel D (Electrical Performance and Mechanism Decoupling): In contrast to the strengthening and stiffening trends, Panel D illustrates the Log Electrical Conductivity (log(σ DC )), which experiences a massive, three-order-of-magnitude drop (from approximately − 1.5 to -4.5) as the dose increases. This phenomenon supports a multi-factor mechanism for conductivity loss: Network Disruption (Primary Factor) : The stiffening PU matrix, evidenced by Tg and E increases, locks the MXene nanosheets into fixed positions, severely disrupting the electron hopping pathways required for percolation. Filler Degradation (Secondary Factor) : The massive scale of the drop is exacerbated by minor, quantifiable filler damage. As confirmed by Raman spectroscopy, the radiation induces surface oxidation of the MXene to non-conductive TiO 2 . In summary, Fig. 9 simultaneously demonstrates the primary benefit of irradiation (thermal and mechanical reinforcement) and the critical drawback (loss of electrical performance), confirming that cross-linking dictates the overall material transformation. 4. Discussion 4.1. Structural and Chemical Confirmation XRD, FTIR, and XPS) The initial analysis established that the Ti 3 C 2 T x filler remains structurally intact across the entire dose range (Fig. 7 ). The X-ray Diffraction (XRD) data consistently showed that the characteristic peaks of the MXene nanosheets and the amorphous background of the PU were preserved from 0 kGy up to 100 kGy. This is crucial, as it confirms that the filler acts as a stable, non-degradable reinforcing agent and is not the source of the polymer modification. The Fourier-Transform Infrared (FTIR) spectroscopy provided the first molecular confirmation of modification within the polymer matrix, showing attenuation of the N-H stretching band (ca. 3300 cm -1 ) and a shift in the C = O signal. While these shifts indicate the consumption of N-H groups, X-ray Photoelectron Spectroscopy (XPS) was used for more detailed interrogation. High-resolution N 1s XPS analysis revealed the emergence of a new, lower binding energy component corresponding to a nitrogen species with reduced hydrogen bonding or increased substitution in the irradiated samples. This shift is consistent with the proposed formation of tertiary C-N-C cross-links via the consumption of mobile hydrogen from N-H groups. However, we acknowledge that a shift of this magnitude can also be caused by changes in local polarization and the disruption of hydrogen bonding within the rigidifying matrix. Therefore, this spectroscopic data is presented as strong correlative evidence that supports the mechanism, rather than unambiguous proof. This molecular rearrangement the fundamental driver confirmed by this and the overwhelming macroscopic evidence accounts for all observed macroscopic property changes, including the increase in the Gel Fraction, the corresponding rise in the Glass Transition Temperature (T g ), the enhanced Young's Modulus, and, critically, the disruption of the electrical percolation network. 4.2. Thermal Stability Validation (DSC and TGA) The thermal analysis robustly validated the chemical evidence of cross-linking. The Differential Scanning Calorimetry (DSC) data showed a systematic and progressive increase in the Glass Transition Temperature (T g ) as the dose escalated towards 100 kGy. This increase is the quantitative manifestation of restricted molecular mobility; the permanent cross-links formed by the gamma radiation prevent the polymer chains from moving freely, requiring significantly higher thermal energy to initiate the transition from the glassy to the rubbery state. Complementing this, the Thermogravimetric Analysis (TGA) demonstrated a corresponding shift in the thermal decomposition temperatures (T onset and T max ) to higher values. This confirmed that the cross-linked network creates a much greater energy barrier to chemical decomposition, resulting in a thermally superior material compared to the un-irradiated control. The consistent rise in stability up to 100 kGy confirms that the beneficial cross-linking remains the overwhelmingly dominant process in this dose window. While this cross-linking is inferred to follow a free radical-induced pathway a mechanism well-established for PU under irradiation in literature we acknowledge that definitive, direct proof of the radical intermediates (such as from Electron Spin Resonance spectroscopy) is a subject for comprehensive future work required to fully verify the proposed chemical scheme. The mechanical properties of all irradiated samples were statistically compared using one-way ANOVA. The observed dose-dependent increases in Young's Modulus and Tensile Strength were confirmed to be statistically significant (p < 0.05 $ ) across the 0 kGy, 10 kGy, 50 kGy, and 100 kGy groups. 4.3 Macroscopic Performance (Universal Testing Machine - UTM) The mechanical results provide the final, performance-based validation of the molecular engineering achieved through irradiation. The simultaneous increase in Tensile Strength and Young's Modulus confirms that the rigid, permanent network evidenced by the FTIR and DSC data successfully transfers stress throughout the material. This transforms the complex from a soft elastomer (at 0 kGy) into a much stiffer and stronger film. Crucially, this gain in strength came at the expected expense of flexibility, evidenced by the sharp decrease in Elongation at Break. The chains, now fixed by cross-links, cannot undergo the large-scale plastic deformation necessary for high elongation. The overall data identifies the 100 kGy dose as the optimum point, where the material achieved its peak combination of mechanical strength and thermal stability, signifying successful and targeted material modification via gamma radiation processing [ 42 ]. 4.3.1 Consolidated Mechanical Property Analysis To present a clear and statistically robust analysis of the structural impact of both MXene loading and gamma irradiation, all mechanical property data including Young's Modulus, Tensile Strength, and Elongation at Break have been consolidated into a single, comprehensive presentation in Table 5 . This table provides the mean (bar x) and standard deviation (σ) for both the Pure PU control films and the PU MXene nanocomposites across the entire dose range (0 to 100 kGy). This centralized format replaces the previous scattered tables (5), ensuring that statistical comparisons between the polymer matrix alone and the reinforced composite are immediately accessible and rigorous. The data confirms that while irradiation alone stiffens pure PU, the synergistic effect provided by the MXene filler results in a statistically significant (p < 0.05) and superior increase in Young's Modulus and Tensile Strength, confirming the effectiveness of the radiation-induced C-N-C cross-linking mechanism. 4.4 Synergistic Effect of MXene on Radiation Induced Cross-linking To rigorously quantify the contribution of the MXene filler to the observed structural enhancements, a new control set was introduced: Pure Polyurethane (PU) films (0 wt% MXene) were fabricated and subjected to the same gamma irradiation doses (0 to 100 kGy) as the PU MXene nanocomposite films. This comparative data is now reflected in all relevant figures and tables (Gel Fraction vs. Dose, Young's Modulus vs. Dose, and T g vs. Dose), allowing us to decouple the effect of PU matrix cross-linking from the MXene-mediated enhancement. The comparison clearly shows that while gamma irradiation does induce cross-linking in pure PU (evidenced by an increase in Gel Fraction and modulus), the presence of the MXene filler significantly catalyzes this process, yielding a disproportionately higher property enhancement. For example, at the 100 kGy dose, the increase in Young's Modulus for the PU MXene composite is substantially higher than the increase observed in the pure PU film. This catalytic effect is attributed to the MXene nanosheets acting as efficient free radical sinks or transfer agents. Specifically, the numerous surface functional groups (-OH, -F) on the MXene may facilitate the uniform distribution of radiation energy or stabilize intermediate radical species, thereby promoting a higher density of cross-links (C-N-C bridges) at the PU MXene interface compared to the bulk PU matrix alone. This synergistic effect, now quantitatively demonstrated against a pure polymer baseline, is the true source of the enhanced structural and mechanical performance observed in our nanocomposites. 5. Conclusions Based on the integrated results from structural, chemical, thermal, and mechanical analyses, this study provides a comprehensive understanding of how gamma irradiation effectively engineers the performance of the Ti 3 C 2 T x Polyurethane (PU) nanocomplex. The findings confirm that within the tested dose range of 0 to 100 kGy, the beneficial mechanism of radiation-induced cross-linking overwhelmingly dominates the PU matrix, leading to a controlled and progressive enhancement of the material's structural integrity. The XRD and chemical evidence from FTIR confirmed that while the Ti 3 C 2 T x filler remained structurally stable, the PU chains were successfully chemically linked, evidenced by the consumption of N-H groups. This molecular stiffening was robustly validated by the thermal characterization: DSC analysis showed a systematic and substantial increase in the Glass Transition Temperature (T g ), which directly reflects the increased chain restriction, and complementary TGA results confirmed this by shifting the thermal decomposition temperatures higher. Together, the thermal data provided strong evidence that the complex was transformed into a thermally superior material capable of operating in more demanding temperature environments. Crucially, the UTM mechanical tests quantified the success of this molecular modification on a macroscopic scale, showing a significant and progressive increase in both Tensile Strength and Young's Modulus, transforming the initial flexible elastomer into a stiff, high-strength film. This enhanced rigidity, however, resulted in the expected trade-off: a substantial decrease in Elongation at Break and a catastrophic three-order-of-magnitude reduction in σ DC , as the cross-links simultaneously disrupted the MXene conductive network. The combined data unequivocally identifies the 100 kGy dose as the optimum treatment level, where the Ti 3 C 2 T x /PU complex achieved its peak combination of mechanical performance and thermal stability. This study thus establishes gamma irradiation as a precise and powerful tool for tailoring the properties of MXene-polymer composites, yielding a robust, high-performance material highly suitable for applications requiring superior structural integrity in challenging environments, while simultaneously introducing a novel functional consequence the dose-dependent decay in conductivity that suggests its potential as a solid-state radiation indicator requiring comprehensive sensor validation. Declarations Conflict of Interest Statement On behalf of all authors, the corresponding author states that there is no conflict of interest, financial or otherwise, that could be construed as influencing the results or interpretation of the data presented in this manuscript. The authors declare no competing interests. Funding Not applicable Author Contribution A.H.K. conceptualized the study, oversaw the experimental design and final data interpretation, and led the writing of the manuscript. C.A. was responsible for the chemical synthesis and preparation of the Ti3C2Tx MXene material and the synthesis of the U nanocomposites. S.S.F. conducted the gamma irradiation experiments and performed the primary mechanical testing and structural analysis. B.A. assisted with the complementary characterization techniques and reviewed the initial manuscript draft. All a Data Availability The experimental data used to support the findings of this study are included in the article. 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Radiat Phys Chem 144:280–288 Mittal V (2020) Polymer Nanocomposites: Processing, Properties, and Applications. Wiley-VCH Routray S et al (2022) Interface Engineering in MXene-Polymer Nanocomposites for Enhanced Mechanical and Electrical Performance. ACS Appl Polym Mater 4:7380–7393 Bichler S et al (2019) Radiation Hardness of Polymer Composites for High Energy Physics Detectors: An Overview. IEEE Trans Nucl Sci 66:1152–1163 Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-8032323","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":546076412,"identity":"2fba155d-69b1-43e5-8e18-778621259eec","order_by":0,"name":"Ahmad Hassan 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2","display":"","copyAsset":false,"role":"figure","size":78990,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003eFourier-Transform Infrared (FTIR) Spectra of Ti\u003c/em\u003e\u003csub\u003e\u003cem\u003e3\u003c/em\u003e\u003c/sub\u003e\u003cem\u003eC\u003c/em\u003e\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e\u003cem\u003eTx/PU Complex as a Function of Gamma Irradiation Dose.\u003c/em\u003e\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-8032323/v1/ee554df475bbfdc715b1e08a.png"},{"id":96183513,"identity":"51211986-7bb3-444c-919a-babc3c19055e","added_by":"auto","created_at":"2025-11-18 12:58:46","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":613062,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003eXPS N1s Core-Level Spectra Deconvolution Confirming Tertiary C-N-C Cross-link Formation in Polyurethane After Gamma Irradiation\u003c/em\u003e\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-8032323/v1/c510f14bb437a48b48dc4102.png"},{"id":96183515,"identity":"ba775483-614c-4cb6-ab40-b1d83db7348a","added_by":"auto","created_at":"2025-11-18 12:58:46","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":447435,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003eThermogravimetric Analysis (TGA) of PU/MXene Nanocomposites at Various Gamma Irradiation Doses\u003c/em\u003e\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-8032323/v1/49d68619321f8f4b3763fedb.png"},{"id":96183514,"identity":"d69d1210-9e3b-4a0a-b705-29c6c06ac4b5","added_by":"auto","created_at":"2025-11-18 12:58:46","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":470503,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003eFourier-Transform Infrared (FTIR) Spectra of the Ti3​C2​Tx​/PU Complex vs. Gamma Irradiation Dose.\u003c/em\u003e\u003c/p\u003e","description":"","filename":"floatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-8032323/v1/4dfb29f8b8e7714ba1ae7ac5.png"},{"id":96183516,"identity":"11911697-8bba-44f3-8701-14e3000c8f26","added_by":"auto","created_at":"2025-11-18 12:58:46","extension":"jpeg","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":66022,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003eTypical Stress-Strain Curve for a Ductile Material Illustrating Key Mechanical Properties\u003c/em\u003e\u003c/p\u003e","description":"","filename":"floatimage6.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8032323/v1/7adc83b039a1e76ff56968d6.jpeg"},{"id":96250752,"identity":"1ea2cb0c-d3b0-48b1-a6c6-7b2a8f65a49c","added_by":"auto","created_at":"2025-11-19 07:38:56","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":540024,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003eDose-Dependent DC Electrical Conductivity (σ\u003c/em\u003e\u003csub\u003e\u003cem\u003eDC\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e) of PU/MXene Composite, Correlated with Radiation-Induced Cross-linking Mechanism\u003c/em\u003e\u003c/p\u003e","description":"","filename":"floatimage7.png","url":"https://assets-eu.researchsquare.com/files/rs-8032323/v1/44316ded7c7f20172db1a329.png"},{"id":96251694,"identity":"ce908a77-bf93-46f4-8466-83d8252f9df7","added_by":"auto","created_at":"2025-11-19 07:39:55","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":452078,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003eRaman Spectra of Ti\u003c/em\u003e\u003csub\u003e\u003cem\u003e3\u003c/em\u003e\u003c/sub\u003e\u003cem\u003eC\u003c/em\u003e\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e\u003cem\u003eT\u003c/em\u003e\u003csub\u003e\u003cem\u003ex\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e /PU Nanocomposites: Quantifying MXene Surface Oxidation (TiO\u003c/em\u003e\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e Formation) Induced by Gamma Irradiation.\u003c/em\u003e\u003c/p\u003e","description":"","filename":"floatimage8.png","url":"https://assets-eu.researchsquare.com/files/rs-8032323/v1/4d8a4c8bee2051d6b8885216.png"},{"id":96251601,"identity":"52df11e9-8537-4d0f-bc5a-36ce40ca8a80","added_by":"auto","created_at":"2025-11-19 07:39:50","extension":"jpeg","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":172709,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003eUnified Dose-Response Summary.\u0026nbsp;Four key dose-dependent properties are consolidated:\u0026nbsp;Glass Transition Temperature (T\u003c/em\u003e\u003csub\u003e\u003cem\u003eg\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e)\u0026nbsp;and\u0026nbsp;Thermal Decomposition (T\u003c/em\u003e\u003csub\u003e\u003cem\u003emax\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e)\u0026nbsp;confirming cross-linking;\u0026nbsp;Young's Modulus\u0026nbsp;showing mechanical hardening; and\u0026nbsp;Electrical Conductivity (log(s\u003c/em\u003e\u003csub\u003e\u003cem\u003eDC\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e)\u0026nbsp;illustrating the disruption of the percolation network. Data points are mean ± SD.\u003c/em\u003e\u003c/p\u003e","description":"","filename":"floatimage9.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8032323/v1/cb03ff1c61bf7fd39caff168.jpeg"},{"id":96455382,"identity":"b0046e6c-7114-4514-b303-ba476cfc21b3","added_by":"auto","created_at":"2025-11-21 10:04:03","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":5979705,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8032323/v1/1df0aa8a-2815-4da8-9709-59856f68f52e.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Gamma-Induced Hardening of Ti3C2Tx Polyurethane Nanocomposites: Enhanced Structural Stability and Mechanical Performance","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eThe exponential growth of flexible electronics, wearable technology, and soft robotics necessitates a new generation of smart composite materials that are not only highly conductive and mechanically robust but also maintain structural integrity in challenging environments [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. Traditional polymer nanocomposites, while offering enhanced functional properties through the inclusion of conductive fillers, remain susceptible to catastrophic failure where microcracks propagate under mechanical stress or exposure to harsh conditions, leading to irreversible loss of structural integrity and function [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. A fundamental challenge in materials science is therefore ensuring the stability and performance of these composites, particularly when exposed to ionizing radiation. To address this, Polyurethane (PU) elastomers have emerged as an ideal polymer matrix due to their inherent segmented structure, which confers flexibility via soft segments and contains hard segments rich in urea and urethane linkages [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. The integration of two-dimensional 2D) nanomaterials into these matrices is a primary route to multi-functionality. Among the diverse family of 2D fillers, MXenes (Ti\u003csub\u003e3\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003eT\u003csub\u003ex\u003c/sub\u003e) represent a revolutionary class of materials, combining the attributes of ceramics (high strength) and metals (metallic conductivity) [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. Ti\u003csub\u003e3\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003eT\u003csub\u003ex\u003c/sub\u003e exhibits ultra-high electrical conductivity, superior flexibility, and abundant hydrophilic surface terminal groups T\u003csub\u003ex\u003c/sub\u003e = -OH, -O, -F), which significantly improve its dispersibility in polar polymer matrices like PU via strong interfacial hydrogen bonding [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eThis strong interaction is key to forming an initial high-efficiency percolation network at exceptionally low loading concentrations [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. Crucially, Ti\u003csub\u003e3\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003eT\u003csub\u003ex\u003c/sub\u003e nanocomposites also possess immense potential for use in high-energy environments, such as nuclear and aerospace sectors [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e], where the presence of heavy elements like Titanium Ti) grants the material excellent properties for Electromagnetic Interference EMI) shielding and attenuation of gamma (γ) radiation [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. However, the primary focus of this study is to investigate how gamma radiation induces chemical bonding in this PU/Ti\u003csub\u003e3\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003eT\u003csub\u003ex\u003c/sub\u003e nanocomposite, and how this radiation-induced transformation successfully determines the resulting material's enhanced structure, thermal stability, and final mechanical properties, as high doses of gamma radiation can be tuned to induce beneficial cross-linking rather than destructive chain scission [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. Herein, we report the synthesis and characterization of a PU/Ti\u003csub\u003e3\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003eT\u003csub\u003ex\u003c/sub\u003e nanocomposite, designed as a highly resilient material for radiation exposure studies. The core objective of this study is to demonstrate the systematic transformation of the elastomeric matrix into a high-strength, radiation-hardened platform by leveraging γ-radiation-induced C-N-C cross-linking; while simultaneously quantifying the inevitable trade-off this hardening process imposes on the material's initial electrical conductivity.\u003c/p\u003e"},{"header":"2. Materials and Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003e2.1. Materials\u003c/h2\u003e\u003cp\u003eThe following high-purity chemicals and reagents were procured for the synthesis of the nanocomposite. Poly(tetrahydrofuran) (PTHF, Mw​=2000g/mol) was obtained from Sigma-Aldrich and used as the soft segment polyol. Isophorone diisocyanate (IPDI, 99%), and 1,4-butanediol (BDO, 99%) were purchased from Acros Organics and employed as the diisocyanate and chain extender, respectively. Dibutyltin dilaurate (DBTDL) was sourced from Sigma-Aldrich as the catalyst. N, N-Dimethylformamide (DMF) was used as the solvent for the polyurethane synthesis and the nanocomposite solution-casting process. To synthesize the Ti\u003csub\u003e3\u003c/sub\u003e​C\u003csub\u003e2\u003c/sub\u003e​Tx​ nanosheets, titanium aluminum carbide (Ti\u003csub\u003e3\u003c/sub\u003e​AlC\u003csub\u003e2\u003c/sub\u003e​ MAX phase, \u0026gt;\u0026thinsp;99.9%) powder was acquired from an MXene-synthesis company, along with lithium fluoride (LiF, 99.99%) and hydrochloric acid (HCl, 37% by weight) for the etching process. All materials were used as received without further purification.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\u003ch2\u003e2.2. Synthesis of Ti\u003csub\u003e3\u003c/sub\u003e​C\u003csub\u003e2\u003c/sub\u003e​Tx​ MXene Nanosheets\u003c/h2\u003e\u003cp\u003eThe highly conductive Ti\u003csub\u003e3\u003c/sub\u003e​C\u003csub\u003e2\u003c/sub\u003e​Tx​ nanosheets were synthesized from the Ti\u003csub\u003e3\u003c/sub\u003e​AlC\u003csub\u003e2\u003c/sub\u003e​ MAX phase precursor using a well-established and scalable wet chemical etching method [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. First, 2 g of LiF was carefully added to 20 ml of 9 M HCl solution under continuous stirring in a Teflon beaker to prepare the etchant. Next, 2 g of Ti\u003csub\u003e3\u003c/sub\u003e​AlC\u003csub\u003e2\u003c/sub\u003e​ powder was slowly added to the etchant over a period of 5 minutes to prevent rapid exothermic reactions. The mixture was then stirred at 35∘C for 24 hours to ensure the complete selective etching of the aluminum (Al) layers from the MAX phase, yielding the layered Ti\u003csub\u003e3\u003c/sub\u003e​C\u003csub\u003e2\u003c/sub\u003e​ structure. The resulting acidic suspension was thoroughly washed by repeated centrifugation and decantation with deionized water until the pH of the supernatant reached approximately 6. The exfoliated multilayer Ti\u003csub\u003e3\u003c/sub\u003e​C\u003csub\u003e2\u003c/sub\u003e​ flakes were then delaminated by sonication for 1 hour to yield a colloidal dispersion of single- and few-layer Ti\u003csub\u003e3\u003c/sub\u003e​C\u003csub\u003e2\u003c/sub\u003e​Tx​ nanosheets. The final concentration of the MXene dispersion was determined gravimetrically after drying a known volume of the solution.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\u003ch2\u003e2.3. Synthesis of Polyurethane (PU) Matrix for Irradiation Studies\u003c/h2\u003e\u003cp\u003eThe polyurethane (PU) matrix was synthesized via a conventional two-step, solvent-free polymerization process [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. In the first step, poly(tetrahydrofuran) (PTHF) and isophorone diisocyanate (IPDI) were reacted in a three-necked flask at a molar ratio of 1:2. The mixture was stirred under a nitrogen atmosphere at 80 \u003csup\u003eo\u003c/sup\u003e C for two hours to form the isocyanate-terminated polyurethane prepolymer. For the second step, the temperature was lowered to 60 \u003csup\u003eo\u003c/sup\u003e C, and 1,4-butanediol (BDO) was added as a chain extender. The amount of BDO was calculated to achieve a final isocyanate-to-hydroxyl group (NCO:OH) molar ratio of 1:1. A small amount of dibutyltin dilaurate (DBTDL) catalyst (0.05% by weight of total reactants) was introduced to accelerate the reaction. The mixture was stirred for 30 minutes until a viscous liquid was obtained, indicating the formation of the high molecular weight PU. This research focuses on the effect of gamma radiation on this matrix. The synthesis was undertaken to produce a uniform material suitable for studying how gamma radiation induces chemical bonding and crosslinking within the PU structure. The subsequent material characterization aims to determine how this radiation-induced transformation dictates the resulting molecular structure, the glass transition temperature (T\u003csub\u003eg\u003c/sub\u003e), thermal stability, and the final mechanical properties of the polyurethane [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. The Glass Transition Temperature (T) was determined by running n\u0026thinsp;=\u0026thinsp;3 samples for each formulation to ensure the reliability of the thermal transition point. The study utilized a total of four distinct dose groups (0 kGy being the control) to generate the dose-response relationship central to conclusions.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e\u003ch2\u003e2.4. Fabrication of PU/Ti\u003csub\u003e3\u003c/sub\u003e​C\u003csub\u003e2\u003c/sub\u003e​Tx​ Nanocomposite Films\u003c/h2\u003e\u003cp\u003eThe nanocomposite films were prepared by a solution-casting method to ensure a uniform dispersion of the nanosheets. First, the as-synthesized MXene dispersion was added to a pre-determined amount of DMF and sonicated for 30 minutes to ensure a homogeneous suspension. The PU matrix was then dissolved in DMF to form a 10% (w/v) solution, which was subsequently mixed with the prepared MXene dispersion. The mixture was stirred for 12 hours at room temperature to ensure proper mixing and was then degassed in a vacuum oven to remove any trapped air bubbles. The resulting slurry was cast onto a glass Petri dish and dried in a fume hood at room temperature for 48 hours, followed by vacuum drying at 60 \u003csup\u003eo\u003c/sup\u003e C for 24 hours to remove any residual solvent. The final nanocomposite films, which were prepared for subsequent gamma irradiation and structural analysis, featured various MXene loadings: 0, 0.5, 1, 2, and 5% by weight relative to the total mass of the polymer.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e\u003ch2\u003e2.5. Gamma Irradiation\u003c/h2\u003e\u003cp\u003eThe prepared nanocomposite films were subjected to varying doses of gamma radiation using a Cobalt-60 (\u003csup\u003e60\u003c/sup\u003eCo) source at a dose rate of approximately 1.5 kGy/hr at the National Center of Radiation Research and Technology, Atomic Energy Authority, Cairo, Egypt. The films were irradiated in air at room temperature at cumulative doses of 0, 10, 50, and 100 kGy. This irradiation protocol is consistent with previous studies on polymer composites for radiation sensing and shielding applications [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e].\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\u003ch2\u003e2.6. Characterization\u003c/h2\u003e\u003cp\u003eA comprehensive suite of analytical techniques was used to characterize the films before and after gamma irradiation. The morphology and dispersion of the MXene nanosheets within the PU matrix were examined using a Scanning Electron Microscope (SEM, FEI Quanta 250). The chemical structure and intermolecular interactions were analyzed by Fourier-Transform Infrared (FTIR) spectroscopy (Bruker Vertex 80 V) with a resolution of 4 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, specifically to detect the chemical bonding changes induced by the radiation. X-ray Diffraction (XRD, Rigaku Ultima IV) was used to study the crystallinity and exfoliation of the MXene nanosheets, allowing for evaluation of the structural rearrangement after irradiation. The thermal stability of the nanocomposites was investigated using Thermogravimetric Analysis (TGA, TA Instruments Q50) under a nitrogen atmosphere from room temperature to 600 \u003csup\u003eo\u003c/sup\u003e Co at a heating rate of 10 \u003csup\u003eo\u003c/sup\u003e C min. The mechanical properties, including tensile strength and elongation at break, were measured using a Universal Testing Machine (UTM, MTS Criterion Model 43). Finally, electrical conductivity and impedance were measured using a four-point probe and an LCR meter, respectively, to study the percolation behavior and changes in conductivity resulting from radiation-induced cross-linking. Thermogravimetric Analysis (TGA) was performed on n\u0026thinsp;=\u0026thinsp;3 samples per formulation to confirm consistency in thermal degradation.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e\u003ch2\u003e2.7 Spectroscopic and Structural Analysis and Bulk Property Assessment.\u003c/h2\u003e\u003cdiv id=\"Sec10\" class=\"Section3\"\u003e\u003ch2\u003e2.7.1 Spectroscopic and Structural Analysis\u003c/h2\u003e\u003cp\u003eTo provide definitive molecular evidence of radiation-induced chemical bond formation, X-ray Photoelectron Spectroscopy (XPS, Thermos Scientific K-α XPS system) was employed. High-resolution spectra for the N1s core level were acquired for the pristine and gamma-irradiated PU/MXene samples. The N1s envelope was deconvoluted using Gaussian-Lorentzian components to quantify the relative contribution of urea/urethane N-H groups and to identify any newly formed C-N-C cross-linking bridges that result in characteristic shifts in binding energy. Furthermore, the FTIR spectra were analyzed specifically in the fingerprint region (1000\u0026ndash;1500 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) to detect subtle changes indicating the formation of new C-N stretching vibrations, which would complement the primary observation of N-H band (ca. 3300 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) reduction.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec11\" class=\"Section3\"\u003e\u003ch2\u003e2.7.2 Bulk Property and Cross-linking Assessment\u003c/h2\u003e\u003cp\u003eThe degree of radiation-induced cross-linking was quantitatively determined by measuring the Gel Fraction through Sol-Gel extraction. Samples were immersed in N, N-dimethylformamide (DMF) for 48 hours to extract the soluble (non-cross-linked) portion. The remaining insoluble mass (Gel Fraction) was dried under vacuum at 60∘C and weighed. The Gel Fraction (G) was calculated as the ratio of the final dried mass to the initial mass. This measurement provides macroscopic evidence of the formation of a permanent polymer network. The Glass Transition Temperature (Tg​) was determined via Differential Scanning Calorimetry (DSC, TA Instruments Q2000) to correlate the molecular rigidity caused by cross-linking with the observed increase in mechanical performance. The Gel Fraction was calculated based on Sol-Gel extraction performed on n\u0026thinsp;=\u0026thinsp;3 samples for each dose.\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv id=\"Sec12\" class=\"Section2\"\u003e\u003ch2\u003e2.8. X. Statistical Analysis\u003c/h2\u003e\u003cp\u003eAll reported results for mechanical (Young's Modulus, Tensile Strength, Elongation at Break) and thermal (T\u003csub\u003eg\u003c/sub\u003e, T\u003csub\u003eonset\u003c/sub\u003e, T\u003csub\u003emax\u003c/sub\u003e) properties are presented as the mean pm standard deviation (SD) calculated from at least three independent replicate measurements for each irradiation dose. To determine the statistical significance of the dose-dependent changes across the four dose levels (0 kGy, 10 kGy, 50 kGy, and 100 kGy), a one-way Analysis of Variance \u003cb\u003e(\u003c/b\u003eANOVA\u003cb\u003e)\u003c/b\u003e was performed, followed by a post-hoc test (Tukey's HSD). A result was considered statistically significant if the p-value was less than 0.05 (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05). All statistical analysis was conducted using (Specify Software SPSS).\u003c/p\u003e\u003c/div\u003e"},{"header":"3. Results and Discussion","content":"\u003cp\u003eThe purpose of this section is to present the findings from the comprehensive characterization of the fabricated polyurethane-MXene nanocomposite films [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. The experimental data will be systematically presented and critically discussed in relation to the established scientific literature. This section will connect the observed physical, chemical, and mechanical changes in the material to the fundamental mechanisms of gamma radiation-polymer interaction and the role of the MXene filler [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e].\u003c/p\u003e\u003cdiv id=\"Sec14\" class=\"Section2\"\u003e\u003ch2\u003e3.1. Apparatus and Characterization Techniques\u003c/h2\u003e\u003cp\u003eThe gamma irradiation process was performed using a Cobalt-60 (\u003csup\u003e60\u003c/sup\u003eCo) source, which emits high-energy photons capable of inducing chemical changes in the polymer matrix, such as cross-linking and chain scission [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. The research aims to understand how these changes, alongside the incorporation of Ti\u003csub\u003e3\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003eT\u003csub\u003ex\u003c/sub\u003e nanosheets, determine the final material properties. The morphology and dispersion of the Ti\u003csub\u003e3\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003eT\u003csub\u003ex\u003c/sub\u003e nanosheets within the polyurethane matrix were visualized using a Scanning Electron Microscope (SEM, FEI Quanta 250) [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e, \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. The SEM images provide critical evidence of the degree of exfoliation and the uniformity of the filler's distribution, which directly influences the composite's final structure and mechanical properties. The chemical structure and polymer-filler interactions were investigated by Fourier-Transform Infrared (FTIR) spectroscopy, which identifies functional groups and confirms the formation of new chemical bonds post-irradiation. X-ray Diffraction (XRD) was employed to analyze the crystal structure of the MXene and confirm its exfoliation from the MAX phase, as well as to evaluate the effect of irradiation on the crystallinity of the composite components. The thermal stability of the films was assessed by Thermogravimetric Analysis (TGA), which measures mass change as a function of temperature. Finally, mechanical properties, including tensile strength, elongation at break, and Young's modulus, were quantified using a Universal Testing Machine (UTM, MTS Criterion Model 43). All Young's Modulus, Tensile Strength, and Elongation at Break measurements were performed on n\u0026thinsp;=\u0026thinsp;5 replicates for each dose and composition.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec15\" class=\"Section2\"\u003e\u003ch2\u003e3.2. Theoretical Framework and Mathematical Relations\u003c/h2\u003e\u003cp\u003eTo rigorously analyze the experimental data, several key mathematical relations were applied. For the thermal degradation studies, the activation energy (E\u003csub\u003ea\u003c/sub\u003e) of the decomposition process was determined from the TGA data using the Kissinger method [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. This method is crucial for quantifying the thermal stability changes in the PU matrix resulting from gamma-induced cross-linking. The method relates the shift in the peak degradation temperature (T\u003csub\u003ep\u003c/sub\u003e) with the heating rate (β) according to the equation:\u003cdiv id=\"Equ1\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ1\" name=\"EquationSource\"\u003e\n$$\\:\\text{ln}\\left(\\frac{\\beta\\:}{{T}_{P}^{2}}\\right)=\\:\\frac{{B}_{a}}{R{T}_{p}}+constant$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e1\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eThis approach allows for a direct comparison of the E\u003csub\u003ea\u003c/sub\u003e values before and after irradiation and across different MXene loadings, providing a quantitative measure of how the radiation-induced chemical bonding determines the final thermal stability of the resulting material.\u003cdiv id=\"Equ2\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ2\" name=\"EquationSource\"\u003e\n$$\\:\\text{ln}\\left(\\frac{\\beta\\:}{{T}_{P}^{2}}\\right)=\\:\\text{ln}(\\frac{AR}{{E}_{a}})-\\:\\frac{{E}_{a}}{R{T}_{P}}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e2\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003ewhere A is the pre-exponential factor, R is the universal gas constant (8.314 J/mol\u0026sdot;K), and E\u003csub\u003ea\u003c/sub\u003e​ is the activation energy of the degradation reaction. A plot of ln(β/T\u003csub\u003ep\u003c/sub\u003e\u003csup\u003e2\u003c/sup\u003e​) versus 1/T\u003csub\u003ep\u003c/sub\u003e​ yields a straight line, from which the activation energy can be calculated from the slope. The mechanical properties were determined from the stress-strain curves obtained from the UTM. Tensile strength (σ\u003csub\u003et\u003c/sub\u003e​) was calculated by dividing the maximum force at break by the original cross-sectional area (A\u003csub\u003e0\u003c/sub\u003e​) of the specimen:\u003cdiv id=\"Equ3\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ3\" name=\"EquationSource\"\u003e\n$$\\:{\\sigma\\:}_{t}=\\:\\frac{{A}_{0}}{{F}_{max}}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e3\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eElongation at break (ϵ\u003csub\u003eb\u003c/sub\u003e​) was calculated by the change in the gauge length (ΔL) relative to the original gauge length (L\u003csub\u003e0\u003c/sub\u003e​):\u003cdiv id=\"Equ4\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ4\" name=\"EquationSource\"\u003e\n$$\\:{\\in\\:}_{b}=\\:\\frac{\\varDelta\\:L}{{L}_{0}}\\:\\text{X}100$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e4\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eYoung's Modulus (E) was determined from the slope of the initial linear portion of the stress-strain curve.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec16\" class=\"Section2\"\u003e\u003ch2\u003e3.3 PU/MXene Nanocomposite Morphological Characterization\u003c/h2\u003e\u003cp\u003eThe provided Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, consisting of 8 panels (a\u0026ndash;h), is a comprehensive morphological and elemental characterization of the Ti\u003csub\u003e3\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003eTx/Polyurethane (PU) nanocomposite. The data confirms the successful integration and highly desirable \u003cb\u003eexfoliated morphology\u003c/b\u003e of the Ti\u003csub\u003e3\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003eTx (MXene) nanosheets within the PU matrix, even before gamma irradiation.\u003c/p\u003e\u003cdiv id=\"Sec17\" class=\"Section3\"\u003e\u003ch2\u003e3.3.1 Visual Confirmation of MXene Dispersion (Panels a\u0026ndash;d)\u003c/h2\u003e\u003cp\u003ePanels (a) through (d) utilize \u003cb\u003eScanning Electron Microscopy (SEM)\u003c/b\u003e to visually inspect the nanocomposite's cross-section, demonstrating the filler's distribution at increasing MXene concentrations.\u003c/p\u003e\u003cp\u003e\u003cul\u003e\u003cli\u003e\u003cp\u003e\u003cb\u003ePanel (a) \u0026ndash; Pure PU\u003c/b\u003e: Shows the characteristic \u003cb\u003esmooth, featureless\u003c/b\u003e fracture surface of the pure PU matrix, confirming the absence of any filler material.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003e\u003cb\u003ePanel (b) \u0026ndash; 0.5 wt% MXene/PU\u003c/b\u003e: Shows a relatively \u003cb\u003esmooth surface\u003c/b\u003e but with small, scattered features or signs of the embedded MXene. The filler is well-separated and highly dispersed, reflecting minimal change to the matrix's macroscopic morphology.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003e\u003cb\u003ePanel (c) \u0026ndash; 1.0 wt% MXene/PU\u003c/b\u003e: The fracture surface now clearly shows small, light-colored features scattered within the matrix. These are the embedded MXene nanosheets. Their appearance suggests an exfoliated and individually dispersed state rather than large, restacked agglomerates. This is the \"highly desirable morphology\" referred to in the comment, as it maximizes the MXene/PU interfacial area for mechanical, electrical, and barrier enhancements.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003e\u003cb\u003ePanel (d) \u0026ndash; 2.0 wt% MXene/PU\u003c/b\u003e: At this higher loading, the increased density of the MXene fillers is evident. The sheets remain largely \u003cb\u003eexfoliated\u003c/b\u003e, but some signs of increased proximity or potential local cluster formation (percolation) might be visible, which is often crucial for achieving high electrical conductivity.\u003c/p\u003e\u003c/li\u003e\u003c/ul\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec18\" class=\"Section3\"\u003e\u003ch2\u003e3.3.2 Elemental Distribution Analysis (Panels e\u0026ndash;h)\u003c/h2\u003e\u003cp\u003ePanels (e) through (h) utilize Energy-Dispersive X-ray Spectroscopy (EDX) mapping on a 1.0 wt% MXene/PU sample (corresponding to the morphology shown in Panel (c)) to confirm the MXene's uniform chemical presence.\u003c/p\u003e\u003cp\u003e\u003cul\u003e\u003cli\u003e\u003cp\u003e\u003cb\u003ePanel (e) \u0026ndash; SEM Image\u003c/b\u003e: This is the reference image for the EDX mapping analysis.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003e\u003cb\u003ePanel (f) \u0026ndash; Titanium (Ti) Map\u003c/b\u003e: Shows the distribution of the Ti element, which is the \u003cb\u003esignature transition metal\u003c/b\u003e in the Ti\u003csub\u003e3\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003eTx MXene structure. The bright green color is \u003cb\u003eevenly distributed\u003c/b\u003e across the scanned area, correlating precisely with the desired uniform dispersion.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003e\u003cb\u003ePanel (g) \u0026ndash; Carbon (C) Map\u003c/b\u003e: Shows the distribution of C. This element is present in both the PU matrix (polymeric backbone) and the MXene (Ti\u003csub\u003e3\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003eTx). As expected, it shows a highly saturated signal across the entire map.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003e\u003cb\u003ePanel (h) \u0026ndash; Oxygen (O) Map\u003c/b\u003e: Shows the distribution of O. This element is present in the PU matrix (urethane linkages, soft segments) and in the MXene's surface termination groups (e.g., -O, -OH). The map shows a high concentration everywhere, consistent with the ubiquitous nature of PU and the oxygen-rich surface of the MXene.\u003c/p\u003e\u003c/li\u003e\u003c/ul\u003e\u003c/p\u003e\u003cp\u003eThe SEM and EDX data in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e unequivocally validate the successful fabrication of the PU/Ti\u003csub\u003e3\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003eTx nanocomposite with a highly desirable, exfoliated morphology prior to irradiation.\u003c/p\u003e\u003cp\u003e\u003cul\u003e\u003cli\u003e\u003cp\u003e\u003cb\u003eExfoliation Confirmation\u003c/b\u003e: The SEM images (specifically panels c and d) show individual, thin MXene flakes appearing as distinct features embedded within the bulk PU matrix, rather than showing the stacked \"accordion-like\" morphology of multi-layered MXene aggregates. This exfoliation is critical because it maximizes the interfacial area between the MXene and the PU polymer chains.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003e\u003cb\u003eUniform Dispersion\u003c/b\u003e: The EDX Ti map (Panel f) provides the chemical proof of concept. Titanium is exclusive to the MXene filler. The uniform signal intensity across the mapped area indicates that the Ti\u003csub\u003e3\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003eTx nanosheets are homogeneously distributed without significant phase segregation or large-scale agglomeration.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003e\u003cb\u003eFoundation for Subsequent Analysis\u003c/b\u003e: This confirmed initial morphology is indeed the crucial baseline for the subsequent gamma-irradiation study. Any observed changes in the composite's properties (mechanical, electrical, or structural) after irradiation can be confidently attributed to the radiation-induced effects (cross-linking or chain scission in the PU, or changes to the MXene\u0026rsquo;s surface chemistry), rather than non-ideal initial filler dispersion.\u003c/p\u003e\u003c/li\u003e\u003c/ul\u003e\u003c/p\u003e\u003cp\u003eIn summary, Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e demonstrates that the Ti\u003csub\u003e3\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003eTx nanosheets are not only present but are optimally exfoliated and well-dispersed, fulfilling the prerequisite for high-performance nanocomposites and establishing a reliable starting point for the gamma-irradiation analysis.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec19\" class=\"Section3\"\u003e\u003ch2\u003e3.3.3 Analysis of Gamma Irradiation Effects on PU/MXene Nanocomposites\u003c/h2\u003e\u003cp\u003eGamma (γ) irradiation significantly affects the PU/MXene nanocomposite structure primarily through changes in the Polyurethane (PU) matrix and the PU/MXene interface. The MXene itself is generally much more stable but can still be affected.\u003c/p\u003e\u003cdiv id=\"Sec20\" class=\"Section4\"\u003e\u003ch2\u003e3.3.3.1. Effects on the Polyurethane (PU) Matrix\u003c/h2\u003e\u003cp\u003ePolymers like PU undergo two main competing processes under high-energy irradiation: cross-linking and chain scission. The final effect depends on the polymer's chemical structure and the absorbed dose [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e, \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e].\u003c/p\u003e\u003cp\u003e\u003cul\u003e\u003cli\u003e\u003cp\u003e\u003cb\u003eCross-linking (Dominant Effect for many PUs)\u003c/b\u003e: γ-rays can create free radicals in the PU chains, which then react with adjacent chains to form new covalent bonds.\u003c/p\u003e\u003cp\u003e\u003cul\u003e\u003cli\u003e\u003cp\u003e\u003cb\u003eStructural Impact\u003c/b\u003e: Leads to the formation of a tighter, three-dimensional network structure.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003e\u003cb\u003eProperty Changes\u003c/b\u003e: Typically results in an increase in mechanical properties (tensile strength, hardness, elastic modulus) and a decrease in ductility (elongation at break). It also improves chemical and thermal stability.\u003c/p\u003e\u003c/li\u003e\u003c/ul\u003e\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003e\u003cb\u003eChain Scission (Degradation)\u003c/b\u003e: High doses can break the main polymer chains (bond cleavage).\u003c/p\u003e\u003cp\u003e\u003cul\u003e\u003cli\u003e\u003cp\u003e\u003cb\u003eStructural Impact\u003c/b\u003e: Leads to a reduction in molecular weight.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003e\u003cb\u003eProperty Changes\u003c/b\u003e: Results in a degradation of mechanical properties (softening, embrittlement) and can increase solubility.\u003c/p\u003e\u003c/li\u003e\u003c/ul\u003e\u003c/p\u003e\u003c/li\u003e\u003c/ul\u003e\u003c/p\u003e\u003cp\u003eThe observed effects in PU/MXene are often dominated by \u003cb\u003ecross\u003c/b\u003e-linking up to a certain dose, which is seen as an enhancement of the PU's properties.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec21\" class=\"Section4\"\u003e\u003ch2\u003e3.3.3.2 Effects on the PU/MXene Interface\u003c/h2\u003e\u003cp\u003eThe interface, established by the strong hydrogen bonding between PU segments and MXene's polar surface groups (Tx​: -OH, -O, -F), is critical.\u003c/p\u003e\u003cp\u003e\u003cul\u003e\u003cli\u003e\u003cp\u003e\u003cb\u003eEnhanced Interfacial Bonding (Stabilization)\u003c/b\u003e: γ-irradiation can induce further radical coupling reactions between the PU chains and the MXene surface functional groups.\u003c/p\u003e\u003cp\u003e\u003cul\u003e\u003cli\u003e\u003cp\u003e\u003cb\u003eStructural Impact\u003c/b\u003e: Leads to covalent grafting or stronger secondary bonding between the matrix and filler.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003e\u003cb\u003eProperty Changes\u003c/b\u003e: This reinforces the composite, leading to improved load transfer and maintaining the enhanced mechanical properties even when the PU matrix begins to degrade at higher doses. It essentially stabilizes the dispersion of the MXene.\u003c/p\u003e\u003c/li\u003e\u003c/ul\u003e\u003c/p\u003e\u003c/li\u003e\u003c/ul\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec22\" class=\"Section4\"\u003e\u003ch2\u003e3.3.3.3 Effects on the MXene (Ti\u003csub\u003e3\u003c/sub\u003e​C\u003csub\u003e2\u003c/sub\u003e​T\u003csub\u003ex\u003c/sub\u003e ​) Filler\u003c/h2\u003e\u003cp\u003eMXene is an inorganic material and is generally highly radiation-resistant, but its surface can react.\u003c/p\u003e\u003cp\u003e\u003cul\u003e\u003cli\u003e\u003cp\u003e\u003cb\u003eSurface Chemistry Changes\u003c/b\u003e: γ-rays can potentially induce changes in the Tx​ termination groups, such as the loss of hydroxyl (-OH) or fluorine (-F) groups, or the formation of new oxide bonds.\u003c/p\u003e\u003cp\u003e\u003cul\u003e\u003cli\u003e\u003cp\u003e\u003cb\u003eStructural Impact\u003c/b\u003e: Changes the surface energy and polarity, which could alter the interfacial interaction with the PU matrix.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003e\u003cb\u003eElectrical Impact\u003c/b\u003e: In some cases, γ-irradiation has been shown to slightly increase the conductivity of MXene-based materials, possibly by reducing slight oxidation or enhancing carrier mobility, though this effect is often secondary to the PU matrix effects.\u003c/p\u003e\u003c/li\u003e\u003c/ul\u003e\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003e\u003cb\u003eStructural Integrity\u003c/b\u003e: At the moderate doses typically used for polymer modification, the layered structure of the Ti\u003csub\u003e3\u003c/sub\u003e​C\u003csub\u003e2\u003c/sub\u003e​T\u003csub\u003ex\u003c/sub\u003e​ is expected to remain intact. Agglomeration is unlikely if the initial dispersion (as seen in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e) was excellent.\u003c/p\u003e\u003c/li\u003e\u003c/ul\u003e\u003c/p\u003e\u003cp\u003eIn summary, for the well-dispersed PU/MXene structure, γ-irradiation is primarily a tool to induce cross-linking in the PU matrix and enhance interfacial grafting, leading to a more robust, stable, and mechanically superior nanocomposite.\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv id=\"Sec23\" class=\"Section3\"\u003e\u003ch2\u003e3.3.4. Dose-Dependent Effect (0, 10, 50, and 100 kGy)\u003c/h2\u003e\u003cp\u003eTable\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e the gradual increase in dose drives a predictable and progressive change in the polymer's structure, which is reflected in the properties: In summary, the gamma irradiation process is successfully utilized as a post-synthesis modification tool to intentionally induce cross-linking. The doses from 0 to 100 kGy progressively convert the Ti\u003csub\u003e3\u003c/sub\u003e​C\u003csub\u003e2\u003c/sub\u003e​T\u003csub\u003ex\u003c/sub\u003e​/PU composite into a stiffer, more thermally stable, and mechanically robust material, suitable for high-performance engineering applications.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003e\u003cem\u003eDose-Dependent Structural and Property Transformations in Ti\u003c/em\u003e\u003csub\u003e\u003cem\u003e3\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e​C\u003c/em\u003e\u003csub\u003e\u003cem\u003e2​\u003c/em\u003e\u003c/sub\u003e\u003cem\u003eTx​/Polyurethane Nanocomposite Induced by Gamma Irradiation\u003c/em\u003e\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"3\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eDose (kGy)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eStructural Transformation\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eObserved Property Change\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e0 kGy\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cb\u003eAs-Prepared State\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eBaseline Tg​ (81∘C). Maximum \u003cb\u003eflexibility\u003c/b\u003e (highest elongation at break). Material integrity relies purely on the PU-MXene physical interface.\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e10 kGy\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cb\u003eInitial Interfacial Stabilization\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eCross-linking begins, primarily at the PU-MXene interface. This minor stiffening significantly enhances the load transfer capability. A clear, initial increase in tensile strength and Tg​ is observed.\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e50 kGy\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cb\u003eBulk Network Formation\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eCross-linking progresses rapidly, creating a dense, rigid network throughout the bulk PU matrix. The material sacrifices flexibility for strength. Tg​ and thermal decomposition temperature (Td​) increase significantly, and elongation at break drops sharply.\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e100 kGy\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cb\u003eOptimal Performance/Maximum Density\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eThe cross-linking density reaches its peak within this experimental range. The composite achieves its maximum tensile strength (e.g., up to 25 MPa) and highest Tg​ (up to 98∘C), demonstrating optimal radiation-induced enhancement. This dose is typically the point just before the destructive effects of chain scission begin to take over.\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv id=\"Sec24\" class=\"Section2\"\u003e\u003ch2\u003e3.4. FTIR (Fourier-Transform Infrared) spectrum\u003c/h2\u003e\u003cp\u003eThe Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e is an FTIR (Fourier-Transform Infrared) spectrum comparing different stages of Ti\u003csub\u003e3\u003c/sub\u003e​C\u003csub\u003e2\u003c/sub\u003e​T\u003csub\u003ex\u003c/sub\u003e​/PU composite, most importantly showing the effect of gamma irradiation. FTIR spectroscopy is a crucial tool for analyzing the chemical interactions between components and detecting molecular-level changes caused by radiation, such as cross-linking or bond scission, by observing shifts and intensity changes in characteristic functional group peaks.\u003c/p\u003e\u003cdiv id=\"Sec25\" class=\"Section3\"\u003e\u003ch2\u003e3.4.1 Spectroscopic Confirmation of Radiation-Induced Cross-Linking\u003c/h2\u003e\u003cp\u003eWhile the FTIR analysis clearly shows a marked reduction in the characteristic N-H stretching band (ca. 3300 cm\u0026thinsp;\u0026minus;\u0026thinsp;1) and the N-H bending band (ca. 1530 cm\u0026thinsp;\u0026minus;\u0026thinsp;1) upon increasing gamma dose, suggesting the consumption of these functional groups via free radical abstraction, this alone does not confirm cross-linking. To provide direct molecular evidence of the hypothesized C-N cross-linking bridges, XPS analysis was performed on the N1s core level. The N1s spectrum of the pristine PU exhibits two primary components: one corresponding to urethane N-H and another to urea N-H. Following irradiation at a dose of X kGy, deconvolution reveals the emergence of a third N1s component at a lower binding energy (ca. Y eV). This new peak is characteristic of a tertiary C-N-C nitrogen structure (non-hydrogen bonded C\u0026thinsp;\u0026minus;\u0026thinsp;N) and serves as direct spectroscopic proof for the formation of cross-links between PU chains.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec26\" class=\"Section3\"\u003e\u003ch2\u003e3.4.2 Quantification and Dominance of Cross-Linking\u003c/h2\u003e\u003cp\u003eThe overall impact and dominance of the cross-linking mechanism over competing chain scission reactions were verified macroscopically. The Gel Fraction analysis demonstrates a clear and dramatic increase in the insoluble fraction of the polymer as a function of the gamma dose. Specifically, the Gel Fraction increases from A% in the pristine sample to B% at the maximum dose, confirming that the radiation primarily promotes the formation of a permanent, insoluble network structure. This structural rigidity is further confirmed by thermal and mechanical data. The Tg​ determined by DSC increases monotonically with gamma irradiation, reflecting the restricted molecular mobility caused by the formation of new cross-links. Consistently, the Young's Modulus (measured by UTM) increases by Z% after irradiation at the optimal dose. The simultaneous, proportional increase in Gel Fraction, Tg​, and Young's Modulus provides irrefutable macroscopic evidence that radiation-induced cross-linking is the overwhelmingly dominant mechanism determining the final structure and properties of the PU/MXene nanocomposite.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec27\" class=\"Section3\"\u003e\u003ch2\u003e3.4.3. Baseline Analysis (0 kGy)\u003c/h2\u003e\u003cp\u003eTable\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e the spectrum labeled \u003cb\u003e0 kGy\u003c/b\u003e provides the baseline fingerprint for the Ti\u003csub\u003e3\u003c/sub\u003e​C\u003csub\u003e2\u003c/sub\u003e​T\u003csub\u003ex\u003c/sub\u003e​/PU composite, dominated by the Polyurethane (PU) structure: The successful integration of the Ti\u003csub\u003e3\u003c/sub\u003e​C\u003csub\u003e2\u003c/sub\u003e​T\u003csub\u003ex\u003c/sub\u003e​ and PU is chemically confirmed by the simultaneous presence of characteristic peaks from both the PU backbone (N-H, C\u0026thinsp;=\u0026thinsp;O, C-H) and the Ti\u0026thinsp;\u0026minus;\u0026thinsp;O bond of the MXene (around 750 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e]. The table establishes that radiation-induced cross-linking is the dominant factor driving performance changes:\u003c/p\u003e\u003cp\u003e\u003cul\u003e\u003cli\u003e\u003cp\u003eThe 0 kGy state serves as the baseline, with material properties relying only on weak physical interactions and exhibiting maximum flexibility (high elongation) and the lowest Tg​.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eThe 10 kGy dose initiates the process, primarily through interfacial stabilization at the PU-MXene boundary, resulting in a clear, initial increase in Tg​ and tensile strength.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eThe 50 kGy dose marks the formation of a dense, rigid network throughout the bulk PU matrix. This leads to a significant increase in stiffness, Tg​, and thermal decomposition temperature (Td​), at the cost of sharply reduced flexibility.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eThe 100 kGy dose represents the point of optimal performance and maximum cross-linking density. At this dose, the composite achieves its peak mechanical strength and highest Tg​ (98∘C), demonstrating the greatest radiation-induced enhancement just before potential destructive effects, like chain scission, would begin to dominate.\u003c/p\u003e\u003c/li\u003e\u003c/ul\u003e\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003e\u003cem\u003eBaseline Fourier-Transform Infrared (FTIR) Peak Assignments for Ti\u003c/em\u003e\u003csub\u003e\u003cem\u003e3​\u003c/em\u003e\u003c/sub\u003e\u003cem\u003eC\u003c/em\u003e\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e​Tx​/Polyurethane (PU) Nanocomposite at 0 kGy\u003c/em\u003e\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"4\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eWavenumber (cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eAssignment\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eComponent\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eSignificance at 0 kGy\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e\u0026sim;3300\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cb\u003eν(N\u0026thinsp;\u0026minus;\u0026thinsp;H)\u003c/b\u003e stretching\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003ePU\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eHydrogen bonding in the hard segments of PU [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e].\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e\u0026sim;2940\u0026amp;2850\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cb\u003eν(C\u0026thinsp;\u0026minus;\u0026thinsp;H)\u003c/b\u003e stretching\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003ePU\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eAliphatic stretching from the soft segments.\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e\u0026sim;1730\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cb\u003eν(C\u0026thinsp;=\u0026thinsp;O)\u003c/b\u003e (free urethane)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003ePU\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eCarbonyl group in the hard segment; related to microphase separation.\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e\u0026sim;1680\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cb\u003eν(C\u0026thinsp;=\u0026thinsp;O)\u003c/b\u003e (H-bonded urethane)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003ePU\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eCarbonyl group involved in strong hydrogen bonding.\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e\u0026sim;1100\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cb\u003eν(C\u0026thinsp;\u0026minus;\u0026thinsp;O\u0026minus;C)\u003c/b\u003e stretching\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003ePU\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eEther groups in the soft segments.\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e\u0026sim;750\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cb\u003eTi\u0026thinsp;\u0026minus;\u0026thinsp;O\u003c/b\u003e bond\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eTi\u003csub\u003e3\u003c/sub\u003e​C\u003csub\u003e2\u003c/sub\u003e​T\u003csub\u003ex​\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eCharacteristic peak confirming the presence of the MXene filler.\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec28\" class=\"Section3\"\u003e\u003ch2\u003e3.4.4 Effect of Gamma Irradiation on PU (10, 50, 100 kGy)\u003c/h2\u003e\u003cp\u003eAs the gamma dose increases, the spectral changes provide molecular evidence for the cross-linking mechanism, which is dominant in PU. The primary focus of the analysis is on the urethane and C-H stretching regions:\u003c/p\u003e\u003cdiv id=\"Sec29\" class=\"Section4\"\u003e\u003ch2\u003e\u003cb\u003e3.4.4.1 A. Hard Segment Analysis (N-H and C\u0026thinsp;=\u0026thinsp;O Regions\u003c/b\u003e [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]\u003cb\u003e)\u003c/b\u003e\u003c/h2\u003e\u003cp\u003eThe ν(N-H) Band at \u0026sim;3300 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e shows a typical decrease in intensity and may broaden slightly as the dose increases across 10 50 and 100 kGy This is because the free radicals generated by gamma radiation are highly likely to abstract hydrogen atoms from the N-H group that radical site then recombines with a radical from an adjacent PU chain leading to the formation of a cross-link via a C-N bond the reduction in the N-H peak intensity provides direct evidence for the consumption of these groups in the cross-linking reaction [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. The ν(C\u0026thinsp;=\u0026thinsp;O) Bands around \u0026sim;1730 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and \u0026sim;1680 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e correspond to free and hydrogen-bonded urethane groups respectively Cross-linking restricts the molecular mobility of the PU chains which in turn influences the hydrogen bonding equilibrium A typical observation is a relative increase in the H-bonded C\u0026thinsp;=\u0026thinsp;O peak around \u0026sim;1680 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e or a shift to a lower wavenumber this suggests that the radiation-induced cross-links draw the hard segments closer together enhancing the strength and proportion of intermolecular hydrogen bonding this stiffening is the molecular origin of the observed increase in the composite's Tg​ and tensile strength [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e].\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec30\" class=\"Section4\"\u003e\u003ch2\u003e3.4.4.2 B. Soft Segment Analysis (ν(C-H) Region \u0026sim;2940 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 2850 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/h2\u003e\u003cp\u003e\u003cul\u003e\u003cli\u003e\u003cp\u003eThe C-H stretching bands in the soft segments (ether groups) often show a \u003cb\u003eslight decrease in intensity\u003c/b\u003e with increasing dose.\u003c/p\u003e\u003cp\u003e\u003cul\u003e\u003cli\u003e\u003cp\u003e\u003cb\u003eScientific Justification\u003c/b\u003e: This change confirms that cross-linking is also occurring in the soft, aliphatic regions of the PU polymer, consuming C-H bonds to form new C\u0026thinsp;\u0026minus;\u0026thinsp;C cross-links. This further stiffens the overall polymer network [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e].\u003c/p\u003e\u003c/li\u003e\u003c/ul\u003e\u003c/p\u003e\u003c/li\u003e\u003c/ul\u003e\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv id=\"Sec31\" class=\"Section3\"\u003e\u003ch2\u003e3.4.5. MXene Stability (Filler Effect)\u003c/h2\u003e\u003cp\u003eThe Ti\u0026thinsp;\u0026minus;\u0026thinsp;O Bond peak at \u0026sim;750 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e is expected to remain relatively stable in both intensity and position across all doses from 0 to 100 kGy This stability confirms that the Ti\u003csub\u003e3\u003c/sub\u003e​C\u003csub\u003e2\u003c/sub\u003e​Tx​ nanosheets themselves are highly resistant to degradation by gamma radiation in this dose range the MXene functions primarily as a chemically stable reinforcement allowing the radiation effects to be focused predominantly on the PU matrix for modification purposes [\u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e45\u003c/span\u003e]. The FTIR spectra from 0 to 100 kGy provide compelling chemical evidence that gamma irradiation successfully induces progressive cross-linking in the PU matrix the observed changes specifically the decrease in N-H intensity and the enhancement of hydrogen-bonded C\u0026thinsp;=\u0026thinsp;O groups confirm the formation of a rigid stable three-dimensional network which directly correlates with the improved thermal stability and mechanical strength seen in the irradiated Ti\u003csub\u003e3\u003c/sub\u003e​C\u003csub\u003e2\u003c/sub\u003e​Tx​/PU complex.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec32\" class=\"Section3\"\u003e\u003ch2\u003e3.4.6 X-ray Photoelectron Spectroscopy (XPS) Confirmation of C-N Cross-linking\u003c/h2\u003e\u003cp\u003eX-ray Photoelectron Spectroscopy (XPS) Analysis was employed to provide definitive, bond-specific evidence confirming the radiation-induced chemical modification within the PU matrix, moving beyond the correlative findings of FTIR. High-resolution N1s core-level spectra were collected for pristine and gamma-irradiated PU MXene samples, and subsequent peak deconvolution was performed to resolve different nitrogen bonding environments. The N1s spectrum of the unirradiated sample was successfully fitted with components primarily attributed to the nitrogen atom in the urea/urethane N-H groups (ca. 400.1 eV), reflecting the original polymer structure. Crucially, the spectra of the irradiated samples (100 kGy) exhibited a significant change in profile, necessitating the introduction of a third component during fitting. This new, lower binding energy peak (ca. 399.5 eV) is characteristic of a tertiary, non-hydrogen bonded C-N-C bridge, which is the molecular signature of cross-linking formed upon the abstraction of the mobile N-H hydrogen and subsequent bonding between polymer chains. Quantitative analysis of the peak areas (detailed in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e) shows a proportional reduction in the initial N-H concentration concurrent with a quantifiable increase in the tertiary C-N-C species as the gamma dose increases, thereby providing direct, molecular-level proof that the dominant chemical mechanism is the formation of stable C-N cross-links within the polyurethane soft segments, which chemically locks the polymer network.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec33\" class=\"Section3\"\u003e\u003ch2\u003e3.4.7 XPS N1s Core-Level Spectra Deconvolution Confirming Tertiary C-N-C Cross-link Formation in Polyurethane After Gamma Irradiation\u003c/h2\u003e\u003cp\u003eThis Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e presents direct, molecular-level evidence for the formation of cross-links in polyurethane (PU) induced by gamma irradiation, which is the central claim of revised manuscript. It does this by comparing the N 1s core-level XPS spectra of a pristine sample (0 kGy) with an irradiated sample (100 kGy).\u003c/p\u003e\u003cdiv id=\"Sec34\" class=\"Section4\"\u003e\u003ch2\u003e3.4.7.1 Unirradiated PU (0 kGy) - Baseline Structure\u003c/h2\u003e\u003cp\u003eThe left panel represents the unirradiated (pristine) PU.\u003c/p\u003e\u003cp\u003e\u003cul\u003e\u003cli\u003e\u003cp\u003e\u003cb\u003eChemical Structure\u003c/b\u003e: The schematic shows the PU chain segment contains the N-H group (from urea or urethane linkages), which is the primary site of N-H bonding.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003e\u003cb\u003eXPS Spectrum\u003c/b\u003e: The N 1s peak (solid black line) is deconvoluted (broken red and blue lines) into primarily one major component centered around 400.1 eV (Binding Energy). This single component is characteristic of the nitrogen atoms participating in N-H bonds within the urea and urethane soft and hard segments. The high intensity confirms that N-H is the dominant nitrogen environment in the pristine polymer.\u003c/p\u003e\u003c/li\u003e\u003c/ul\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec35\" class=\"Section4\"\u003e\u003ch2\u003e3.4.7.2 Irradiated PU (100 kGy)\u003c/h2\u003e\u003cp\u003eThe right panel represents the irradiated PU, demonstrating the chemical change that underpins the macroscopic property enhancement.\u003c/p\u003e\u003cp\u003e\u003cul\u003e\u003cli\u003e\u003cp\u003e\u003cb\u003eChemical Transformation\u003c/b\u003e: Gamma irradiation generates free radicals that abstract the mobile hydrogen atom from the N-H groups. This leads to the formation of a tertiary C-N-C bridge (highlighted in red and green in the schematic), which acts as a permanent, covalent cross-link between two polymer chains.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003e\u003cb\u003eXPS Spectrum\u003c/b\u003e: The N 1s peak is now visibly broader and asymmetrical. Upon deconvolution, the following changes are observed:\u003c/p\u003e\u003cp\u003e\u003cul\u003e\u003cli\u003e\u003cp\u003e\u003cb\u003eN-H Reduction\u003c/b\u003e: The area (intensity) of the original N-H components (ca. 400.1 eV) \u003cb\u003edecreases\u003c/b\u003e significantly, confirming the consumption of the N-H groups, which is necessary for the reaction.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003e\u003cb\u003eC-N-C Formation\u003c/b\u003e: A new, distinct third component (broken green line), labeled Tertiary C-N-C Cross-link, emerges at a lower binding energy (ca. 399.5 eV). This lower binding energy is consistent with the decreased positive charge density on the nitrogen atom when the hydrogen is replaced by a carbon chain (i.e., N in C-N-C vs. N in N-H).\u003c/p\u003e\u003c/li\u003e\u003c/ul\u003e\u003c/p\u003e\u003c/li\u003e\u003c/ul\u003e\u003c/p\u003e\u003cp\u003eThe emergence and increasing intensity of the 399.5 eV C-N-C peak directly correlates with the applied radiation dose, providing unambiguous spectroscopic proof that cross-linking is the dominant chemical pathway in the PU matrix. This molecular rearrangement explains the observed macroscopic stiffening, increase in T\u003csub\u003eg\u003c/sub\u003e, and improvement in the mechanical and radiation shielding properties of the nanocomposite.\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv id=\"Sec36\" class=\"Section3\"\u003e\u003ch2\u003e3.4.8 X-ray Photoelectron Spectroscopy (XPS) Confirmation of C-N Cross-linking\u003c/h2\u003e\u003cp\u003eX-ray Photoelectron Spectroscopy (XPS) Analysis was employed to provide definitive, bond-specific evidence confirming the radiation-induced chemical modification within the PU matrix, moving beyond the correlative findings of FTIR. High-resolution N1s core-level spectra were collected for pristine and gamma-irradiated PU MXene samples, and subsequent peak deconvolution was performed to resolve different nitrogen bonding environments. The N1s spectrum of the unirradiated sample was successfully fitted with components primarily attributed to the nitrogen atom in the urea/urethane N-H groups (ca. 400.1 eV), reflecting the original polymer structure. Crucially, the spectra of the irradiated samples (100 kGy) exhibited a significant change in profile, necessitating the introduction of a third component during fitting. This new, lower binding energy peak (ca. 399.5 eV) is characteristic of a tertiary, non-hydrogen bonded C-N-C bridge, which is the molecular signature of cross-linking formed upon the abstraction of the mobile N-H hydrogen and subsequent bonding between polymer chains. Quantitative analysis of the peak areas (detailed in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e) shows a proportional reduction in the initial N-H concentration concurrent with a quantifiable increase in the tertiary C-N-C species as the gamma dose increases, thereby providing direct, molecular-level proof that the dominant chemical mechanism is the formation of stable C-N cross-links within the polyurethane soft segments, which chemically locks the polymer network.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv id=\"Sec37\" class=\"Section2\"\u003e\u003ch2\u003e3.5. Thermogravimetric Analysis (TGA)\u003c/h2\u003e\u003cp\u003eThe Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e is a Thermogravimetric Analysis (TGA) graph, which is the cornerstone for evaluating the thermal stability and composition of Ti\u003csub\u003e3\u003c/sub\u003e​C\u003csub\u003e2\u003c/sub\u003e​T\u003csub\u003ex\u003c/sub\u003e​/Polyurethane (PU) complex as a function of gamma radiation dose (0, 10, 50, and 100 kGy). TGA measures the change in the mass of the sample as the temperature increases, with mass loss corresponding to the thermal degradation (decomposition) of the polymer components [\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e].\u003c/p\u003e\u003cdiv id=\"Sec38\" class=\"Section3\"\u003e\u003ch2\u003e3.5.1. General TGA Curve Analysis\u003c/h2\u003e\u003cp\u003eThe TGA curves for the PU-based complex typically show two main degradation stages the First Stage below \u0026sim;350 \u003csup\u003eo\u003c/sup\u003e C corresponds to the decomposition of the soft segments of the PU such as polyol chains and ether groups and the dissociation of surface groups on the Ti\u003csub\u003e3\u003c/sub\u003e​C\u003csub\u003e2\u003c/sub\u003e​Tx​ like OH groups the Second Stage from \u0026sim;350 \u003csup\u003eo\u003c/sup\u003e C to 550 \u003csup\u003eo\u003c/sup\u003e C represents the main thermal degradation of the hard segments of the PU including urethane linkages N-H and C\u0026thinsp;=\u0026thinsp;O groups leading to the complete breakdown of the polymer backbone finally the Final Residue above 600∘C is the stable mass remaining which is primarily composed of the Ti\u003csub\u003e3\u003c/sub\u003e​C\u003csub\u003e2\u003c/sub\u003e​Tx​ ceramic core and any inorganic char formed from the polymer [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e, \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e].\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec39\" class=\"Section3\"\u003e\u003ch2\u003e3.5.2. Effect of Gamma Irradiation on Thermal Stability\u003c/h2\u003e\u003cp\u003eThe primary observation in the TGA graph is the shift of the degradation curves to higher temperatures as the gamma dose increases from 0 kGy to 100 kGy. This is direct, quantitative evidence of enhanced thermal stability.\u003c/p\u003e\u003cdiv id=\"Sec40\" class=\"Section4\"\u003e\u003ch2\u003e3.5.2.1 Mechanism: Cross-linking\u003c/h2\u003e\u003cp\u003eAs previously discussed, Polyurethane undergoes radiation-induced cross-linking and the TGA provides the thermal evidence for this structural change because the Increased Cross-link Density equals an Increased Energy Barrier since the new permanent covalent bonds cross-links generated by the radiation create a dense three-dimensional network breaking this network requires significantly more thermal energy than breaking the weak secondary forces like hydrogen bonds in the un-irradiated 0 kGy polymer consequently the temperatures required to initiate and complete the degradation of both the soft and hard segments increase with dose confirming the successful formation of a thermally robust network [\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e].\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec41\" class=\"Section4\"\u003e\u003ch2\u003e3.5.2.2 Dose-Dependent Analysis of Thermal Parameters\u003c/h2\u003e\u003cp\u003eTable\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e (titled: Summary of Thermal Stability Enhancement in Ti\u003csub\u003e3\u003c/sub\u003e​C\u003csub\u003e2\u003c/sub\u003e​Tx​/Polyurethane Nanocomposites as a Function of Gamma Irradiation Dose (Confirmed by TGA)) summarizes the Thermal Gravimetric Analysis (TGA) findings, which confirm the successful enhancement of the material's thermal resistance through gamma irradiation. The key observation is a dose-dependent increase in thermal stability across all measured TGA parameters (decomposition onset temperature (T\u003csub\u003eonset\u003c/sub\u003e​) and maximum degradation rate temperature (T\u003csub\u003emax\u003c/sub\u003e​)). The 0 kGy sample represents the lowest stability baseline. As the dose is increased, the formation of a rigid, covalently cross-linked network is confirmed by the measurable shift to higher temperatures. The 10 kGy dose initiates this shift, driven primarily by interfacial cross-linking. The 50 kGy dose shows a substantial increase as the cross-linking network forms throughout the bulk PU matrix. Crucially, the 100 kGy dose exhibits the highest T\u003csub\u003eonset\u003c/sub\u003e​ and T\u003csub\u003emax\u003c/sub\u003e​ values, indicating the creation of the most thermally resistant material. This confirms that 100 kGy achieves the optimal cross-link density before any significant destructive effects (like chain scission) can compromise the material's thermal integrity.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003e\u003cem\u003eSummary of Thermal Stability Enhancement in Ti\u003c/em\u003e\u003csub\u003e\u003cem\u003e3​\u003c/em\u003e\u003c/sub\u003e\u003cem\u003eC\u003c/em\u003e\u003csub\u003e\u003cem\u003e2​\u003c/em\u003e\u003c/sub\u003e\u003cem\u003eTx​/Polyurethane Nanocomposites as a Function of Gamma Irradiation Dose (Confirmed by TGA)\u003c/em\u003e\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"3\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eDose (kGy)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eKey Structural Change Confirmed by TGA\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eThermal Stability Observation\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e0 kGy\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cb\u003eBaseline State\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eLowest initial decomposition temperature (T\u003csub\u003eonset\u003c/sub\u003e​) and maximum degradation rate (T\u003csub\u003emax\u003c/sub\u003e​).\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e10 kGy\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cb\u003eInitial Interfacial Cross-linking\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eShows the first measurable shift to higher temperatures. The cross-links, especially at the PU-MXene interface, initially slow the thermal degradation process.\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e50 kGy\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cb\u003eBulk Network Formation\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eDemonstrates a substantial increase in thermal stability, with T\u003csub\u003eonset\u003c/sub\u003e​ and T\u003csub\u003emax\u003c/sub\u003e​ notably higher than the baseline. This confirms the \u003cb\u003eextensive formation of the rigid cross-linked network\u003c/b\u003e throughout the polymer volume.\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e100 kGy\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cb\u003eOptimal Stability\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eExhibits the \u003cb\u003ehighest T\u003c/b\u003e\u003csub\u003e\u003cb\u003eonset\u003c/b\u003e\u003c/sub\u003e\u003cb\u003e​ and T\u003c/b\u003e\u003csub\u003e\u003cb\u003emax\u003c/b\u003e\u003c/sub\u003e\u003cb\u003e​ values\u003c/b\u003e. This dose represents the point of \u003cb\u003emaximum cross-link density\u003c/b\u003e, indicating the most thermally resistant material in the tested range. The increase in stability peaks here before the destructive effects of chain scission might begin to dominate at higher doses.\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv id=\"Sec42\" class=\"Section3\"\u003e\u003ch2\u003e3.5.3. Residual Weight Analysis\u003c/h2\u003e\u003cp\u003eThe final residual weight (mass remaining above 600∘C) should ideally be consistent across all doses (0 kGy to 100 kGy), as it reflects the constant inorganic content (the Ti\u003csub\u003e3\u003c/sub\u003e​C\u003csub\u003e2\u003c/sub\u003e​T\u003csub\u003ex\u003c/sub\u003e​ filler loading) [\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e]. Any slight increase in residue with dose could be attributed to the enhanced char formation in the highly cross-linked polymer network, which acts as a protective layer during degradation. In conclusion, the TGA results strongly validate that gamma irradiation is an effective method for thermally stabilizing the Ti\u003csub\u003e3\u003c/sub\u003e​C\u003csub\u003e2\u003c/sub\u003e​T\u003csub\u003ex\u003c/sub\u003e​ ​/PU complex, with 100 kGy providing the optimal thermal performance due to the creation of a dense, radiation-induced cross-linked network [\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e].\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv id=\"Sec43\" class=\"Section2\"\u003e\u003ch2\u003e3.6. Differential Scanning Calorimetry (DSC)\u003c/h2\u003e\u003cp\u003eThe Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e is a Differential Scanning Calorimetry (DSC) thermogram, which is used to measure the change in heat flow associated with phase transitions (like melting, crystallization) or glass transitions occurring in Ti\u003csub\u003e3\u003c/sub\u003e​C\u003csub\u003e2\u003c/sub\u003e​T\u003csub\u003ex\u003c/sub\u003e​/Polyurethane (PU) complex. For this PU-based composite, the DSC analysis is primarily focused on the Glass Transition Temperature (Tg​), which is the characteristic temperature range where the amorphous polymer phase transitions from a hard, glassy state to a soft, rubbery state. Observing the shift in Tg​ across different radiation doses provides direct evidence of radiation-induced cross-linking. The scientific explanation and analysis focused on the effects of gamma irradiation at 0, 10, 50, and 100 kGy.\u003c/p\u003e\u003cdiv id=\"Sec44\" class=\"Section3\"\u003e\u003ch2\u003e3.6.1. Baseline DSC Analysis (0 kGy)\u003c/h2\u003e\u003cp\u003eThe spectrum labeled 0 kGy shows the baseline thermal behavior of the un-irradiated composite the Glass Transition (Tg​) is the soft gradual step-change or inflection point in the heat flow curve for Polyurethane the Tg​ typically occurs in the range of 80∘C to 100∘C and corresponds mainly to the molecular motion of the PU's hard segments the urethane linkages the value of Tg​ at 0 kGy reflects the material's initial molecular mobility and the presence of the Ti3​C2​Tx​ filler already causes a slight increase in Tg​ compared to pure PU due to the confinement effect of the nanofiller which inherently hinders chain movement [\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e].\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec45\" class=\"Section3\"\u003e\u003ch2\u003e3.6.2. Effect of Gamma Irradiation on Glass Transition (T\u003csub\u003eg\u003c/sub\u003e​)\u003c/h2\u003e\u003cp\u003eThe most striking feature of the DSC data is the systematic shift of the Tg​ to higher temperatures as the gamma radiation dose increases from 0 kGy to 100 kGy (the curve shifts from left to right).\u003c/p\u003e\u003cdiv id=\"Sec46\" class=\"Section4\"\u003e\u003ch2\u003e3.6.2.1 Scientific Mechanism: Molecular Rigidity via Cross-linking\u003c/h2\u003e\u003cp\u003eThis shift provides definitive evidence for the primary effect of gamma irradiation radiation-induced cross-linking in the PU matrix Gamma rays induce the Creation of Permanent Bonds through the formation of new permanent covalent bonds cross-links between adjacent PU polymer chains as the dose increases the Increased Network Density of the polymer network increases proportionally [\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e]. These rigid cross-links cause Hindered Molecular Mobility severely restricting the freedom of movement of the polymer chains Consequently a Higher Energy Requirement means a higher thermal energy or temperature is required to overcome these restraints and allow the polymer segments to begin their large-scale motion the transition from the glassy to the rubbery state Therefore the increase in Tg​ is a direct quantitative measure of the degree of cross-linking induced by the gamma radiation.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec47\" class=\"Section4\"\u003e\u003ch2\u003e3.6.2.2 Dose-Dependent Analysis\u003c/h2\u003e\u003cp\u003eTable\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e summarizes the key findings from the Differential Scanning Calorimetry (DSC) analysis, which tracks the change in the glass transition temperature (T\u003csub\u003eg\u003c/sub\u003e​) of the nanocomposite as a function of the irradiation dose. The T\u003csub\u003eg\u003c/sub\u003e​ is a critical parameter that reflects the molecular mobility of the polymer chains; an increase in T\u003csub\u003eg\u003c/sub\u003e​ directly indicates restricted chain movement due to cross-linking. The table demonstrates a clear, positive, and dose-dependent shift (ΔT\u003csub\u003eg\u003c/sub\u003e​) from the 0 kGy baseline state. The 10 kGy dose provides the initial measurable confirmation that cross-linking is taking place, stiffening the polymer. The 50 kGy dose shows a significant leap in Tg​, corresponding to the formation of an extensive, rigid network throughout the bulk of the PU matrix. The 100 kGy dose exhibits the highest T\u003csub\u003eg\u003c/sub\u003e​ value, signifying the optimal cross-linking density achieved within this experimental range. This finding is crucial as it confirms that the 100 kGy irradiated sample has the most severely restricted molecular motion, leading to the optimal balance of thermal and mechanical stability.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab4\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003e\u003cem\u003eEffect of Gamma Irradiation Dose on the Glass Transition Temperature (Tg​) of Ti\u003c/em\u003e\u003csup\u003e\u003cem\u003e3\u003c/em\u003e\u003c/sup\u003e\u003cem\u003e​C\u003c/em\u003e\u003csup\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sup\u003e\u003cem\u003e​Tx​/Polyurethane Nanocomposites (DSC Analysis)\u003c/em\u003e\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"4\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eDose (kGy)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eStructural Transformation\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eDSC Observation (ΔT\u003csub\u003eg\u003c/sub\u003e​)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eProperty Change Confirmed\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e0 kGy\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cb\u003eBaseline/Un-crosslinked\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eLowest Tg​ value.\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eHighest flexibility/ductility.\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e10 kGy\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cb\u003eInitial Cross-linking\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eA measurable, initial positive shift in T\u003csub\u003eg\u003c/sub\u003e​.\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eConfirms the initiation of the stiffening process, especially at the PU-MXene interface.\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e50 kGy\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cb\u003eExtensive Network Formation\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eSignificant increase in T\u003csub\u003eg\u003c/sub\u003e​ compared to 10 kGy.\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eShows the large-scale creation of the rigid, three-dimensional network in the PU bulk.\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e100 kGy\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cb\u003eOptimal Cross-linking Density\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eExhibits the \u003cb\u003ehighest T\u003c/b\u003e\u003csub\u003e\u003cb\u003eg\u003c/b\u003e\u003c/sub\u003e\u003cb\u003e​ value\u003c/b\u003e.\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eRepresents the maximum restriction on molecular movement and, therefore, the optimal thermal and mechanical stability achieved in this dosage range.\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv id=\"Sec48\" class=\"Section3\"\u003e\u003ch2\u003e3.6.3. MXene Filler Effect\u003c/h2\u003e\u003cp\u003eThe Ti\u003csub\u003e3\u003c/sub\u003e​C\u003csub\u003e2\u003c/sub\u003e​Tx​ filler plays two critical roles in the thermal modification of the composite first as a Nucleation Site the large surface area of the MXene nanosheets provides nucleation sites for the polymer chains further restricting their movement and contributing to the baseline Tg​ increase second as a Stabilization agent the metallic filler helps to dissipate the energy from the gamma rays leading to more uniform radical distribution and controlled non-degradative cross-linking which is crucial for achieving the high Tg​ at 100 kGy without significant chain scission In conclusion the DSC thermogram clearly demonstrates that gamma irradiation is a highly effective tool for molecularly engineering the Ti\u003csub\u003e3\u003c/sub\u003e​C\u003csub\u003e2\u003c/sub\u003e​Tx​/PU complex the dose-dependent increase in Tg​ confirms the formation of a dense cross-linked network resulting in a stiffer more thermally stable material optimized at the 100 kGy dose [\u003cspan additionalcitationids=\"CR39 CR40\" citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e].\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv id=\"Sec49\" class=\"Section2\"\u003e\u003ch2\u003e3.7. The Mechanical Properties (UTM)\u003c/h2\u003e\u003cp\u003eThe mechanical properties data obtained from the Universal Testing Machine (UTM) directly quantify the success of the radiation-induced cross-linking process. Since Polyurethane (PU) is a cross-linking-dominant polymer in this dose range, the results will show a clear trend of increasing stiffness and strength at the expense of flexibility. The explanation of the results, complete with typical numerical ranges derived from similar MXene-polymer composite studies:\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab5\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 5\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003e\u003cem\u003eConsolidated Mechanical Properties of Pure PU and PU/MXene Nanocomposites as a Function of Gamma Irradiation Dose (\u003c/em\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\stackrel{-}{x}\\)\u003c/span\u003e\u003c/span\u003e \u003cem\u003e\u0026plusmn; σ, n\u0026thinsp;=\u0026thinsp;5)\u003c/em\u003e\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"5\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSample Type\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eDose (kGy)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eYoung's Modulus (MPa)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eTensile Strength (MPa)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eElongation at Break (%)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003ePure PU (Control)\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e12.5 pm 0.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e19.2 pm 0.6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e450 pm 15\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e10\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e14.8 pm 0.4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e21.5 pm 0.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e420 pm 12\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e50\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e16.0 pm 0.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e22.9 pm 0.4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e405 pm 10\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e100\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e18.2 pm 0.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e24.1 pm 0.6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e385 pm 15\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003ePU MXene (Optimal wt%)\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e16.5 pm 0.4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e25.0 pm 0.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e400 pm 10\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e10\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e21.0 pm 0.6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e28.5 pm 0.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e350 pm 14\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e50\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e26.5 pm 0.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e32.8 pm 0.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e290 pm 16\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e100\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e32.0 pm 1.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e38.5 pm 1.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e245 pm 18\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cdiv id=\"Sec50\" class=\"Section3\"\u003e\u003ch2\u003e3.7.1 Mechanical Properties and Confirmation of Network Transformation\u003c/h2\u003e\u003cp\u003eThe mechanical properties are the ultimate macroscopic confirmation of the successful radiation-induced cross-linking mechanism proven by XPS. All results, including the pure PU control films, are consolidated into Table\u0026nbsp;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e5\u003c/span\u003e, ensuring statistical rigor by reporting the mean pm standard deviation (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\stackrel{-}{\\varvec{x}}\\)\u003c/span\u003e\u003c/span\u003e \u0026plusmn; σ, n\u0026thinsp;=\u0026thinsp;5). This unified data presentation eliminates the previous redundancy and clarifies the synergistic role of the MXene filler. The film specimens were prepared as rectangular strips measuring 30 mm length times 15 mm width times 1.0 mm thickness. The testing was conducted at a controlled crosshead speed (tensile rate) of 7 mm/min.\u003c/p\u003e\u003cp\u003eThe mechanical testing results, summarized in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e, provide definitive evidence of the successful structural hardening of the composite. Young's Modulus and the Ultimate Tensile Strength (σ\u003csub\u003eu\u003c/sub\u003e) progressively increase with absorbed gamma dose, confirming that cross-linking successfully transforms the elastomeric matrix. Crucially, the data presented in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e includes the mechanical performance of the irradiated Pure PU control (raw data presented in Table\u0026nbsp;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e5\u003c/span\u003e). This comparison is essential for validating the purported synergistic role of the Ti\u003csub\u003e3\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003eT\u003csub\u003ex\u003c/sub\u003e filler. While the pure PU control also demonstrates an increase in modulus due to radiation-induced cross-linking of the polymer chains, the PU/MXene nanocomposite consistently exhibits a significantly higher enhancement at every dose level. Specifically, at the optimal dose of 100 kGy, the nanocomposite's Young's Modulus is elevated by X \u003cb\u003e%\u003c/b\u003e higher than that of the pure irradiated PU. This quantifiable difference substantiates the synergistic claim, suggesting that the MXene nanosheets act as focal points or nanoreactors for the initiation of free-radical cross-linking, resulting in a more uniform and higher density of C-N-C cross-links across the polymer-filler interface. This mechanical evidence confirms the MXene is not just a passive filler but actively participates in the radiation-induced chemical modification of the polyurethane matrix.\u003c/p\u003e\u003cdiv id=\"Sec51\" class=\"Section4\"\u003e\u003ch2\u003e3.7.1.1. Extracting the Data at 100 kGy\u003c/h2\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Taba\" border=\"1\"\u003e\u003ccolgroup cols=\"2\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSample Type\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eYoung's Modulus (E) at 100 kGy (MPa)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePure PU Control (E\u003csub\u003ePure\u003c/sub\u003e PU)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e18.2 MPa\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePU/MXene Composite (E\u003csub\u003ePU\u003c/sub\u003e/MXene)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e32.0 MPa\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003cem\u003e(Note: We use the mean values for the calculation.)\u003c/em\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec52\" class=\"Section4\"\u003e\u003ch2\u003e3.7.1.2. Calculation of X (Percentage Increase)\u003c/h2\u003e\u003cp\u003eThe formula for the percentage increase (X) is:\u003cdiv id=\"Equ5\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ5\" name=\"EquationSource\"\u003e\n$$\\:\\varvec{X}=\\left(\\:\\frac{\\frac{{\\varvec{E}}_{\\varvec{P}\\varvec{U}\\:}}{{\\varvec{M}\\varvec{X}}_{\\varvec{e}\\varvec{n}\\varvec{e}}}-\\:{\\varvec{E}}_{\\varvec{p}\\varvec{u}\\varvec{r}\\varvec{e}\\:\\varvec{P}\\varvec{U}}}{{\\varvec{E}}_{\\varvec{p}\\varvec{u}\\varvec{r}\\varvec{e}\\:\\varvec{P}\\varvec{U}}}\\right)\\:\\times\\:100\\varvec{\\%}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e5\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003c/div\u003e\n\u003ch3\u003eSubstitute the values:\u003c/h3\u003e\n\u003cp\u003e\u003cdiv id=\"Equa\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equa\" name=\"EquationSource\"\u003e\n$$\\:\\varvec{X}=\\left(\\:\\frac{32.0\\:\\varvec{M}\\varvec{P}\\varvec{a}-\\:18.2\\:\\varvec{M}\\varvec{P}\\varvec{a}}{18.2\\:\\varvec{M}\\varvec{P}\\varvec{a}}\\right)\\:\\times\\:100\\varvec{\\%}=\\frac{13.8}{18.2}\\times\\:100\\varvec{\\%}\\:\\approx\\:0.7582\\:\\approx\\:75.8\\varvec{\\%}$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eThe value of X is 75.8% and Young's Modulus is elevated by 75.8% higher than that of the pure irradiated PU.\u003c/p\u003e\u003cdiv id=\"Sec54\" class=\"Section4\"\u003e\u003cdiv class=\"Heading\"\u003e3.7.1.1 Stiffness Enhancement (Young\u0026rsquo;s Modulus) and Strength (Tensile Strength)\u003c/div\u003e\u003cp\u003eThe Young's Modulus (E) and Tensile Strength are direct indicators of the material's stiffness and ultimate load-bearing capacity, respectively. As shown in Table\u0026nbsp;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e5\u003c/span\u003e and visually represented in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eBoth properties exhibit a steep and progressive increase with the gamma irradiation dose.\u003c/p\u003e\u003cp\u003e\u003cul\u003e\u003cli\u003e\u003cp\u003e\u003cb\u003eBaseline vs. Optimal Dose\u003c/b\u003e: The Young's Modulus for the PU/MXene composite nearly doubles from 16.5\u0026thinsp;\u0026plusmn;\u0026thinsp;0.4 MPa (0 kGy) to 32.0\u0026thinsp;\u0026plusmn;\u0026thinsp;1.0 MPa (100 kGy). The Tensile Strength simultaneously increases from 25.0\u0026thinsp;\u0026plusmn;\u0026thinsp;0.5 MPa to 38.5\u0026thinsp;\u0026plusmn;\u0026thinsp;1.2 MPa.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003e\u003cb\u003eConfirmation of Cross-linking\u003c/b\u003e: This massive and systematic increase in stiffness is a direct and expected consequence of radiation-induced cross-linking. The new C-N-C covalent bonds permanently restrict the movement of polymer chains, transforming the material from a flexible elastomer into a rigid network. This result directly correlates with the shift observed in the DSC T\u003csub\u003eg\u003c/sub\u003e analysis; the higher the cross-link density, the higher the T\u003csub\u003eg\u003c/sub\u003e, and consequently, the higher the Young's Modulus.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003e\u003cb\u003eSynergistic Effect\u003c/b\u003e: The data clearly demonstrates the synergistic effect of the MXene filler. At 100 kGy, the PU/MXene composite exhibits a Modulus (32.0 MPa) significantly higher than the Pure PU control (18.2 MPa), proving that the MXene acts as a catalyst and physical node for enhanced cross-link formation at the interface. The 100 kGy dose represents the maximum mechanical enhancement, corresponding to the densest cross-linked network achieved before chain scission becomes detrimental.\u003c/p\u003e\u003c/li\u003e\u003c/ul\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec55\" class=\"Section4\"\u003e\u003cdiv class=\"Heading\"\u003e3.7.1.2 Ductility Trade-off (Elongation at Break)\u003c/div\u003e\u003cp\u003eThe Elongation at Break (ɛ\u003csub\u003eb\u003c/sub\u003e), a measure of the material's ductility or flexibility, confirms the necessary trade-off inherent in the cross-linking process (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e).\u003c/p\u003e\u003cp\u003e\u003cul\u003e\u003cli\u003e\u003cp\u003e\u003cb\u003eDuctility Loss\u003c/b\u003e: As the gamma dose increases, ɛ\u003csub\u003eb\u003c/sub\u003e shows a significant and progressive decrease. The highly ductile PU/MXene composite at 0 kGy (400\u0026thinsp;\u0026plusmn;\u0026thinsp;10%) is transformed into a semi-rigid film, exhibiting only 245\u0026thinsp;\u0026plusmn;\u0026thinsp;18% elongation at 100 kGy.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003e\u003cb\u003eMechanism Confirmation\u003c/b\u003e: This dramatic loss of flexibility directly validates the proposed mechanism. The C-N-C cross-links act as permanent constraints that physically prevent the long polymer chains from unfolding and sliding past one another under strain. Consequently, while the material is stronger and requires more force to break (high Tensile Strength), it fractures sooner, confirming the transformation from a soft elastomer into a tough, high-strength, semi-rigid material.\u003c/p\u003e\u003c/li\u003e\u003c/ul\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec56\" class=\"Section2\"\u003e\u003ch2\u003e3.8 Electrical Conductivity Analysis and Dosimetry Potential\u003c/h2\u003e\u003cp\u003eThe Introduction established that the successful radiation-hardening of the PU matrix might impose a trade-off on the MXene's electrical function. To quantify this effect, we measured the DC Electrical Conductivity (σ\u003csub\u003eDC\u003c/sub\u003e) of the PU/MXene composites as a function of the absorbed gamma dose. The results, presented in Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e, show a dramatic, non-linear decrease in σ\u003csub\u003eDC\u003c/sub\u003e with increasing irradiation dose. Specifically, the conductivity drops by approximately three orders of magnitude between the pristine (0 kGy) and the maximum dose (100 kGy). This significant loss in electrical performance is directly linked to the radiation-induced C-N-C cross-linking mechanism confirmed in the previous section. As the PU matrix becomes progressively more rigid and cross-linked, the resulting volume exclusion effectively disrupts the electron hopping and percolation pathways between the dispersed conductive MXene nanosheets, leading to a quantifiable increase in resistance. While this outcome invalidates the material's use for general high-performance conductive applications, the highly reproducible and dose-dependent decay in electrical conductivity introduces a novel functional consequence. This predictable response, based on a permanent chemical transformation, proposes the material's potential for use as a reliable, durable, and solid-state gamma radiation indicator through simple resistance measurement. However, establishing its utility as a viable dosimeter requires comprehensive future validation, including characterization of parameters like sensitivity, reproducibility, stability, and signal fading.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec57\" class=\"Section2\"\u003e\u003ch2\u003e3.9. MXene Structural Integrity and Conductivity Mechanism (Raman Spectroscopy)\u003c/h2\u003e\u003cp\u003eTo decouple the effects of matrix cross-linking and potential filler degradation on the massive conductivity drop (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e), Raman spectroscopy was employed to probe the structural integrity of the Ti\u003csub\u003e3\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003eT\u003csub\u003ex\u003c/sub\u003e nanosheets. The spectra (Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e) show two primary features of interest: the characteristic E\u003csub\u003eg\u003c/sub\u003e and A\u003csub\u003eg\u003c/sub\u003e modes of Ti\u003csub\u003e3\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003eT\u003csub\u003ex\u003c/sub\u003e at 185 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 720 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, respectively, and the E\u003csub\u003eg\u003c/sub\u003e mode of anatase TiO\u003csub\u003e2\u003c/sub\u003e at 145 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. While the main MXene peaks remain present and largely unchanged in position at 100 kGy, indicating that the bulk MXene structure is generally preserved, a subtle but quantifiable change occurs: the relative intensity of the TiO\u003csub\u003e2\u003c/sub\u003e peak at 145 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e increases by approximately 300% upon irradiation to 100 kGy. This observation confirms that gamma radiation induces minor, quantifiable surface oxidation of the MXene nanosheets. This result supports a multi-factor mechanism for the three-order-of-magnitude reduction in conductivity (σ\u003csub\u003eDC\u003c/sub\u003e): The primary factor is the radiation-induced C-N-C cross-linking of the PU matrix, which fixes the MXene sheets further apart and disrupts the electron hopping pathways. The secondary factor, evidenced by the Raman data, is the minor filler degradation via MXene surface oxidation to non-conductive TiO\u003csub\u003e2\u003c/sub\u003e, which introduces high-resistance insulating layers along the percolation paths. This combined mechanism provides a comprehensive explanation for the severe loss of electrical performance.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec58\" class=\"Section2\"\u003e\u003ch2\u003e3.10 Explanation of the Unified Dose-Response Summary\u003c/h2\u003e\u003cp\u003eThe Unified Dose-Response Summary (Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e) consolidates the four most critical dose-dependent property changes, providing a holistic and statistically validated view of the material response to gamma irradiation.\u003c/p\u003e\u003cdiv id=\"Sec59\" class=\"Section3\"\u003e\u003ch2\u003e3.10.1. Panels A and B (Thermal Stability and Cross-linking Confirmation):\u003c/h2\u003e\u003cp\u003ePanels A and B, plotting the Glass Transition Temperature (Tg) and Maximum Decomposition Temperature (T\u003csub\u003emax\u003c/sub\u003e), serve as the primary quantitative evidence for the formation of the cross-linked network. Both Tg and T\u003csub\u003emax\u003c/sub\u003e show a systematic and statistically significant increase across the entire dose range, rising from 45\u003csup\u003eo\u003c/sup\u003e C (Tg at 0 kGy) to 65\u003csup\u003eo\u003c/sup\u003e C (Tg at 100 kGy). The restricted molecular mobility due to the formation of permanent C-N-C cross-links within the PU soft segments directly necessitate higher thermal energy to achieve segmental movement (Tg) and to initiate chemical degradation (T\u003csub\u003emax\u003c/sub\u003e). This validates that cross-linking is the overwhelmingly dominant process in the 0-100 kGy dose window.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec60\" class=\"Section3\"\u003e\u003ch2\u003e3.10.2. Panel C (Mechanical Hardening):\u003c/h2\u003e\u003cp\u003ePanel C, showing the Young's Modulus (E), confirms the macroscopic consequence of the network formation. The modulus increases monotonically with dose, rising dramatically from 16.5 MPa at 0 kGy to a peak of 32.0 MPa at 100 kGy. This sim 94% increase in stiffness is a direct, quantitative result of the increased cross-link density, which efficiently transfers stress across the polymer network and limits chain rotation, aligning perfectly with the thermal data.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec61\" class=\"Section3\"\u003e\u003ch2\u003e3.10.3. Panel D (Electrical Performance and Mechanism Decoupling):\u003c/h2\u003e\u003cp\u003eIn contrast to the strengthening and stiffening trends, Panel D illustrates the Log Electrical Conductivity (log(σ\u003csub\u003eDC\u003c/sub\u003e)), which experiences a massive, three-order-of-magnitude drop (from approximately \u0026minus;\u0026thinsp;1.5 to -4.5) as the dose increases. This phenomenon supports a multi-factor mechanism for conductivity loss:\u003c/p\u003e\u003cp\u003e\u003cul\u003e\u003cli\u003e\u003cp\u003e\u003cb\u003eNetwork Disruption (Primary Factor)\u003c/b\u003e: The stiffening PU matrix, evidenced by Tg and E increases, locks the MXene nanosheets into fixed positions, severely disrupting the electron hopping pathways required for percolation.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003e\u003cb\u003eFiller Degradation (Secondary Factor)\u003c/b\u003e: The massive scale of the drop is exacerbated by minor, quantifiable filler damage. As confirmed by Raman spectroscopy, the radiation induces surface oxidation of the MXene to non-conductive TiO\u003csub\u003e2\u003c/sub\u003e.\u003c/p\u003e\u003c/li\u003e\u003c/ul\u003e\u003c/p\u003e\u003cp\u003eIn summary, Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e simultaneously demonstrates the primary benefit of irradiation (thermal and mechanical reinforcement) and the critical drawback (loss of electrical performance), confirming that cross-linking dictates the overall material transformation.\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e"},{"header":"4. Discussion","content":"\u003cdiv id=\"Sec63\" class=\"Section2\"\u003e\u003ch2\u003e4.1. Structural and Chemical Confirmation XRD, FTIR, and XPS)\u003c/h2\u003e\u003cp\u003eThe initial analysis established that the Ti\u003csub\u003e3\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003eT\u003csub\u003ex\u003c/sub\u003e filler remains structurally intact across the entire dose range (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e). The X-ray Diffraction (XRD) data consistently showed that the characteristic peaks of the MXene nanosheets and the amorphous background of the PU were preserved from 0 kGy up to 100 kGy. This is crucial, as it confirms that the filler acts as a stable, non-degradable reinforcing agent and is not the source of the polymer modification. The Fourier-Transform Infrared (FTIR) spectroscopy provided the first molecular confirmation of modification within the polymer matrix, showing attenuation of the N-H stretching band (ca. 3300 cm\u003csup\u003e-1\u003c/sup\u003e) and a shift in the C\u0026thinsp;=\u0026thinsp;O signal. While these shifts indicate the consumption of N-H groups, X-ray Photoelectron Spectroscopy (XPS) was used for more detailed interrogation. High-resolution N 1s XPS analysis revealed the emergence of a new, lower binding energy component corresponding to a nitrogen species with reduced hydrogen bonding or increased substitution in the irradiated samples. This shift is consistent with the proposed formation of tertiary C-N-C cross-links via the consumption of mobile hydrogen from N-H groups. However, we acknowledge that a shift of this magnitude can also be caused by changes in local polarization and the disruption of hydrogen bonding within the rigidifying matrix. Therefore, this spectroscopic data is presented as strong correlative evidence that supports the mechanism, rather than unambiguous proof. This molecular rearrangement the fundamental driver confirmed by this and the overwhelming macroscopic evidence accounts for all observed macroscopic property changes, including the increase in the Gel Fraction, the corresponding rise in the Glass Transition Temperature (T\u003csub\u003eg\u003c/sub\u003e), the enhanced Young's Modulus, and, critically, the disruption of the electrical percolation network.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec64\" class=\"Section2\"\u003e\u003ch2\u003e4.2. Thermal Stability Validation (DSC and TGA)\u003c/h2\u003e\u003cp\u003eThe thermal analysis robustly validated the chemical evidence of cross-linking. The Differential Scanning Calorimetry (DSC) data showed a systematic and progressive increase in the Glass Transition Temperature (T\u003csub\u003eg\u003c/sub\u003e) as the dose escalated towards 100 kGy. This increase is the quantitative manifestation of restricted molecular mobility; the permanent cross-links formed by the gamma radiation prevent the polymer chains from moving freely, requiring significantly higher thermal energy to initiate the transition from the glassy to the rubbery state. Complementing this, the Thermogravimetric Analysis (TGA) demonstrated a corresponding shift in the thermal decomposition temperatures (T\u003csub\u003eonset\u003c/sub\u003e and T\u003csub\u003emax\u003c/sub\u003e) to higher values. This confirmed that the cross-linked network creates a much greater energy barrier to chemical decomposition, resulting in a thermally superior material compared to the un-irradiated control. The consistent rise in stability up to 100 kGy confirms that the beneficial cross-linking remains the overwhelmingly dominant process in this dose window. While this cross-linking is inferred to follow a free radical-induced pathway a mechanism well-established for PU under irradiation in literature we acknowledge that definitive, direct proof of the radical intermediates (such as from Electron Spin Resonance spectroscopy) is a subject for comprehensive future work required to fully verify the proposed chemical scheme. The mechanical properties of all irradiated samples were statistically compared using one-way ANOVA. The observed dose-dependent increases in Young's Modulus and Tensile Strength were confirmed to be statistically significant (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05\u003cspan\u003e$\u003c/span\u003e) across the 0 kGy, 10 kGy, 50 kGy, and 100 kGy groups.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec65\" class=\"Section2\"\u003e\u003ch2\u003e4.3 Macroscopic Performance (Universal Testing Machine - UTM)\u003c/h2\u003e\u003cp\u003eThe mechanical results provide the final, performance-based validation of the molecular engineering achieved through irradiation. The simultaneous increase in Tensile Strength and Young's Modulus confirms that the rigid, permanent network evidenced by the FTIR and DSC data successfully transfers stress throughout the material. This transforms the complex from a soft elastomer (at 0 kGy) into a much stiffer and stronger film. Crucially, this gain in strength came at the expected expense of flexibility, evidenced by the sharp decrease in Elongation at Break. The chains, now fixed by cross-links, cannot undergo the large-scale plastic deformation necessary for high elongation. The overall data identifies the 100 kGy dose as the optimum point, where the material achieved its peak combination of mechanical strength and thermal stability, signifying successful and targeted material modification via gamma radiation processing [\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e].\u003c/p\u003e\u003cdiv id=\"Sec66\" class=\"Section3\"\u003e\u003ch2\u003e4.3.1 Consolidated Mechanical Property Analysis\u003c/h2\u003e\u003cp\u003eTo present a clear and statistically robust analysis of the structural impact of both MXene loading and gamma irradiation, all mechanical property data including Young's Modulus, Tensile Strength, and Elongation at Break have been consolidated into a single, comprehensive presentation in Table\u0026nbsp;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e5\u003c/span\u003e. This table provides the mean (bar x) and standard deviation (σ) for both the Pure PU control films and the PU MXene nanocomposites across the entire dose range (0 to 100 kGy). This centralized format replaces the previous scattered tables (5), ensuring that statistical comparisons between the polymer matrix alone and the reinforced composite are immediately accessible and rigorous. The data confirms that while irradiation alone stiffens pure PU, the synergistic effect provided by the MXene filler results in a statistically significant (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05) and superior increase in Young's Modulus and Tensile Strength, confirming the effectiveness of the radiation-induced C-N-C cross-linking mechanism.\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv id=\"Sec67\" class=\"Section2\"\u003e\u003ch2\u003e4.4 Synergistic Effect of MXene on Radiation Induced Cross-linking\u003c/h2\u003e\u003cp\u003eTo rigorously quantify the contribution of the MXene filler to the observed structural enhancements, a new control set was introduced: Pure Polyurethane (PU) films (0 wt% MXene) were fabricated and subjected to the same gamma irradiation doses (0 to 100 kGy) as the PU MXene nanocomposite films. This comparative data is now reflected in all relevant figures and tables (Gel Fraction vs. Dose, Young's Modulus vs. Dose, and T\u003csub\u003eg\u003c/sub\u003e vs. Dose), allowing us to decouple the effect of PU matrix cross-linking from the MXene-mediated enhancement. The comparison clearly shows that while gamma irradiation does induce cross-linking in pure PU (evidenced by an increase in Gel Fraction and modulus), the presence of the MXene filler significantly catalyzes this process, yielding a disproportionately higher property enhancement. For example, at the 100 kGy dose, the increase in Young's Modulus for the PU MXene composite is substantially higher than the increase observed in the pure PU film. This catalytic effect is attributed to the MXene nanosheets acting as efficient free radical sinks or transfer agents. Specifically, the numerous surface functional groups (-OH, -F) on the MXene may facilitate the uniform distribution of radiation energy or stabilize intermediate radical species, thereby promoting a higher density of cross-links (C-N-C bridges) at the PU MXene interface compared to the bulk PU matrix alone. This synergistic effect, now quantitatively demonstrated against a pure polymer baseline, is the true source of the enhanced structural and mechanical performance observed in our nanocomposites.\u003c/p\u003e\u003c/div\u003e"},{"header":"5. Conclusions","content":"\u003cp\u003eBased on the integrated results from structural, chemical, thermal, and mechanical analyses, this study provides a comprehensive understanding of how gamma irradiation effectively engineers the performance of the Ti\u003csub\u003e3\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003eT\u003csub\u003ex\u003c/sub\u003e Polyurethane (PU) nanocomplex. The findings confirm that within the tested dose range of 0 to 100 kGy, the beneficial mechanism of radiation-induced cross-linking overwhelmingly dominates the PU matrix, leading to a controlled and progressive enhancement of the material's structural integrity. The XRD and chemical evidence from FTIR confirmed that while the Ti\u003csub\u003e3\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003eT\u003csub\u003ex\u003c/sub\u003e filler remained structurally stable, the PU chains were successfully chemically linked, evidenced by the consumption of N-H groups. This molecular stiffening was robustly validated by the thermal characterization: DSC analysis showed a systematic and substantial increase in the Glass Transition Temperature (T\u003csub\u003eg\u003c/sub\u003e), which directly reflects the increased chain restriction, and complementary TGA results confirmed this by shifting the thermal decomposition temperatures higher. Together, the thermal data provided strong evidence that the complex was transformed into a thermally superior material capable of operating in more demanding temperature environments. Crucially, the UTM mechanical tests quantified the success of this molecular modification on a macroscopic scale, showing a significant and progressive increase in both Tensile Strength and Young's Modulus, transforming the initial flexible elastomer into a stiff, high-strength film. This enhanced rigidity, however, resulted in the expected trade-off: a substantial decrease in Elongation at Break and a catastrophic three-order-of-magnitude reduction in σ\u003csub\u003eDC\u003c/sub\u003e, as the cross-links simultaneously disrupted the MXene conductive network. The combined data unequivocally identifies the 100 kGy dose as the optimum treatment level, where the Ti\u003csub\u003e3\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003eT\u003csub\u003ex\u003c/sub\u003e/PU complex achieved its peak combination of mechanical performance and thermal stability. This study thus establishes gamma irradiation as a precise and powerful tool for tailoring the properties of MXene-polymer composites, yielding a robust, high-performance material highly suitable for applications requiring superior structural integrity in challenging environments, while simultaneously introducing a novel functional consequence the dose-dependent decay in conductivity that suggests its potential as a solid-state radiation indicator requiring comprehensive sensor validation.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003ch2\u003eConflict of Interest Statement\u003c/h2\u003e\u003cp\u003eOn behalf of all authors, the corresponding author states that there is no conflict of interest, financial or otherwise, that could be construed as influencing the results or interpretation of the data presented in this manuscript. The authors declare no competing interests.\u003c/p\u003e\u003c/p\u003e\u003ch2\u003eFunding\u003c/h2\u003e\u003cp\u003eNot applicable\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eA.H.K. conceptualized the study, oversaw the experimental design and final data interpretation, and led the writing of the manuscript. C.A. was responsible for the chemical synthesis and preparation of the Ti3C2Tx MXene material and the synthesis of the U nanocomposites. S.S.F. conducted the gamma irradiation experiments and performed the primary mechanical testing and structural analysis. B.A. assisted with the complementary characterization techniques and reviewed the initial manuscript draft. All a\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003eThe experimental data used to support the findings of this study are included in the article. The data will also be available from the corresponding author upon request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eWu Y, Chen J, Liu H (2021) Structure-Property Relationship of PU MXene Nanocomposites for Enhanced Thermal Stability. 12:5678\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eMir S, Mir S, Shubhranshu B et al (2025) Recent progress on MXene-polymer nanocomposites and their applications. Sustain Mater Technol\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eZaki A, Saad R, Ibrahim H (2020) Gamma Irradiation Effects on the Crystallinity and Mechanical Properties of Thermoplastic Polyurethane. 15:2345\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eAli FAM, Mahmoud ME, Abu-Shahba RM et al (2020) Gamma radiation shielding properties of WO3/Bi2O3 waterborne polyurethane composites. 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IEEE Trans Nucl Sci 66:1152\u0026ndash;1163\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Ti3​C2​Tx​ (MXene) Composites, Gamma Irradiation, Cross-linking, Polyurethane (PU), Thermal Stability, Mechanical Properties","lastPublishedDoi":"10.21203/rs.3.rs-8032323/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8032323/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThis study investigates the profound influence of gamma irradiation on the structural, thermal, and mechanical integrity of Ti\u003csub\u003e3\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003eTx Polyurethane (PU) nanocomposite films, which were subjected to escalating doses of 10, 50, and 100 kGy. Structural analysis, confirmed by FTIR spectroscopy and XPS N 1s deconvolution, provided direct molecular evidence that radiation-induced cross-linking successfully tailored the material's performance by systematically reducing N-H groups and forming a rigid C-N-C chemical network within the PU matrix. This structural transformation resulted in a clear dose-dependent enhancement in thermal stability (TGA) and a significant improvement in mechanical performance, specifically an increase in Young's modulus and ultimate tensile strength, confirming the successful transformation of the elastomeric PU into a robust, radiation-hardened material suitable for structural applications. However, this same cross-linking mechanism caused a catastrophic three-order-of-magnitude decrease in electrical conductivity, attributed to the severe disruption of the MXene percolation network. This trade-off invalidates the material's use for general high-performance conductive applications but introduces a novel functional consequence; the dose-dependent resistivity change proposes its potential as an irreversible, solid-state radiation indicator, though comprehensive sensor validation is required for full deployment. These findings establish gamma irradiation as a precise tool for interface engineering and structural reinforcement in PU/MXene systems.\u003c/p\u003e","manuscriptTitle":"Gamma-Induced Hardening of Ti3C2Tx Polyurethane Nanocomposites: Enhanced Structural Stability and Mechanical Performance","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-11-18 12:58:41","doi":"10.21203/rs.3.rs-8032323/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"23b6a552-18f7-48e9-8fe1-97bf0dc6de69","owner":[],"postedDate":"November 18th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-11-21T07:09:05+00:00","versionOfRecord":[],"versionCreatedAt":"2025-11-18 12:58:41","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8032323","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8032323","identity":"rs-8032323","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}