Investigations on Thermomechanical and Biodegradable Properties of Alkaline Hydrolysis Isolated Nano Hydroxyapatite Reinforced Polylactic Acid Composite Blown Films for sustainable Packaging

Investigations on Thermomechanical and Biodegradable Properties of Alkaline Hydrolysis Isolated Nano Hydroxyapatite Reinforced Polylactic Acid Composite Blown Films for sustainable Packaging | 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 Investigations on Thermomechanical and Biodegradable Properties of Alkaline Hydrolysis Isolated Nano Hydroxyapatite Reinforced Polylactic Acid Composite Blown Films for sustainable Packaging Radhika Panickar, Devotha Mwazembe, Benny Alexander, Edwin Freeman, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7216042/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 20 Feb, 2026 Read the published version in Journal of Polymers and the Environment → Version 1 posted 14 You are reading this latest preprint version Abstract In this study, nano-hydroxyapatite (n-HAp) was extracted from pink perch fish scales (PPFS) using a simple and efficient alkaline hydrolysis method. The obtained n-HAp was characterized through XRD, FTIR, Raman spectroscopy, TGA, SEM, and TEM. Various concentrations of n-HAp (0.25, 0.5, 0.75, and 1 wt.%) were then incorporated into a polylactic acid (PLA) matrix using solution blending followed by blown film extrusion. The influence of n-HAp on the thermal, mechanical, and biodegradable properties of the PLA-based composites was systematically analyzed. FTIR and Raman spectroscopy confirmed chemical bonding between n-HAp and the PLA matrix in the blown films. Thermal analysis via TGA revealed an increase in the initial degradation temperature compared to neat PLA, attributed to the presence of n-HAp. DSC analysis showed a reduction in glass transition temperature and crystallinity, which restricted polymer chain mobility and increased the amorphous phase. Mechanical property evaluation through tensile testing demonstrated that lower concentrations of n-HAp significantly enhanced elongation at break, with PLA_HAp 0.75 exhibiting improved flexibility and increase in elongation compared to neat PLA. A 180-day soil biodegradability study indicated that incorporating 0.5 wt.% n-HAp into the PLA matrix accelerated the hydrolysis process by 500%, enhancing the overall degradation of the PLA_HAp composite film. These findings highlight the potential of n-HAp in improving the functional properties of PLA-based composites for food packaging applications. Polymer composite Alkaline hydrolysis Polylactic Acid Hydroxyapatite Blown Films Biodegradable composite Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 1. INTRODUCTION Petroleum-based plastics are highly versatile materials used in various applications in daily life, including food packaging, construction, consumer products, the medical field, etc. In 2023, global plastic consumption exceeded 400 million metric tons and continues to rise annually. A major concern associated with plastic products is their extensive pollution in landfills and water bodies, which severely impacts the entire ecosystem, including plants, animals, and human health [ 1 , 2 ]. Biodegradable polymers, which can naturally break down in the environment, offer an effective solution to address the increasing concern over the accumulation of non-biodegradable petroleum-based plastics[ 3 – 5 ]. Among the diverse variety of biobased polymers, Polylactic acid (PLA) synthesized from the ring opening polymerization of lactide offers promising properties including biodegradability, biocompatibility, good tensile strength, and widespread availability at a reasonable price[ 6 , 7 ]. PLA is extensively utilized in medical applications due to its excellent biocompatibility and ability to degrade within the body [ 8 , 9 ]. However, PLA possesses inherent disadvantages such as low elasticity, high stiffness with low elongation at break, low thermal stability, moderate water resistance, and limited biodegradability in normal environments. Although PLA is generally recognized as safe (GRAS) for food contact surfaces, these disadvantages make it less suitable for use in food packaging applications. It has been reported that reinforcing the PLA matrix using appropriate fillers at desired weight percentages is an effective method to enhance the thermal, mechanical, and biodegradability properties of PLA[ 9 , 10 ]. Various types of natural fillers, including different types of nanofibers [ 11 , 12 ], nanocellulose [ 13 , 14 ], and other additives have been reported to increase the physicochemical properties. Among these, hydroxyapatite (HAp), a natural mineral found in marine animal (fish and mollusks) bones and teeth, has been extensively studied as an effective filler in polymer composites, particularly for biomedical applications, due to its exceptional physicochemical properties, such as degradability, stability, and biocompatibility [ 15 , 16 ]. However, its use in food packaging applications has not been widely explored. In this present study, extracting HAp from fish scales facilitates the recycling of fish industry byproducts, offering a sustainable and promising filler to enhance PLA properties. HAp reinforced PLA composite blown films for food packaging applications were prepared and investigated for thermal, mechanical, and biodegradable properties. 2. Materials and Methods 2.1. Materials n-HAp for the present work was isolated from pink perch fish scales (PPFS) procured from Nizona Inc., Mumbai, India. The biodegradable polymer PLA 4032D for composite preparation was purchased from Natureworks LLC, USA. Sodium hydroxide and acetic acid for the chemical treatment of PPFS were purchased from Sigma Aldrich. Chloroform (≥ 99.8% with 0.5- 1% ethanol as a stabilizer), used as a solvent for dissolving PLA pellets, was procured from Sigma-Aldrich (St. Louis, MO, USA). 2.2. Alkaline Hydrolysis synthesis of n-HAp The n-HAp in this study was synthesized using the alkaline hydrolysis method, with a schematic representation of the synthesis process shown in Fig. 1 . Initially, PPFS is cleaned with distilled water and dried in an oven. The cleaned PPFS is then ground into a fine powder using a cryogenic freeze mill (6875D freezer/mill) by SPEX SamplePrep. A 10 g sample of the PPFS powder is treated with 0.5M NaOH solution and stirred for 5 hours on a magnetic stirrer to dissolve the organic matter. To remove any residual organic material and neutralize the solution, 0.5M acetic acid is added. The solution is then centrifuged multiple times with distilled water to wash away any remaining organic matter, isolating the n-HAp. The white residue is dried in an oven at 70°C overnight to remove moisture and to obtain the n-HAp powder represented as AH_HAp, as shown in Fig. 1 . 2.3. Preparation of PLA_HAp Composite A simple method of solution blending was employed for the reinforcement of n-HAp in the PLA matrix. Chloroform is one of the best solvents for dissolving PLA pellets in the solution blending technique. Different weight percentages of n-HAp: 0.25 wt. %, 0.5 wt. %, 0.75 wt. %, and 1 wt. % were added to PLA for the PLA_HAp composite preparation. The n-HAp particles weighed at different wt.% were initially added to chloroform and magnetically stirred for 30 minutes for the uniform dispersion of the particles in the solution. Then PLA pellets were added to the same solution followed by magnetic stirring for 5 hours to dissolve the PLA pellets completely and form the PLA_HAp composite solution. The solution was transferred to an aluminum tray and placed under a fume hood overnight to evaporate all the chloroform to obtain a thin sheet of PLA_HAp composite. 2.4. Preparation of PLA_HAp Composite Filaments The prepared PLA_HAp composite sheets were shredded into small pieces and extruded into filaments using a Filabot EX2 single-screw filament extruder. Filaments with 0.25 wt. %, 0.5 wt. %, 0.75 wt. %, and 1 wt. % of n-HAp in PLA composite were extruded. The filaments were extruded out at an extruder temperature of 170 o C (melting temperature of PLA). The single screw extruder speed was adjusted to maintain the filament thickness around 1.6 mm to 1.85 mm. The filaments extruded out from the extruder nozzle were passed through an airpath and winded on a spool at the other end of the filament extruder. 2.5. Preparation of PLA_HAp Composite Blown Films PLA_HAp composite filaments containing 0.25 wt.%, 0.5 wt.%, 0.75 wt.%, and 1 wt.% of n-HAp were first extruded and then pelletized using a Filabot pelletizer in preparation for blown film extrusion. Blown films were produced using an Ultra Microfilm Blowing Line (model LUMF-150) equipped with a single-screw extruder from Lab Tech Engineering Company LTD. The extruder featured a conical single screw with a length-to-diameter (L/D) ratio of 30, a feed diameter of 18 mm, and a terminal diameter of 8 mm. Film extrusion was performed at a screw speed of 50–60 rpm, with barrel and die temperatures maintained at 340°F (170°C) and 325°F (163°C), respectively. The extruded films were then guided through a series of spring-loaded nip rolls toward a winding bobbin located at the opposite end of the extrusion setup [ 17 ]. 2.6. Characterization Techniques The composition and identification of n-HAp and PLA_HAp composite films were performed using a RIGAKU SmartLab X-ray diffractometer with monochromatic Copper Kα1 radiation. Samples were scanned over a 2θ range of 5° to 80° at a scan rate of 5° per minute, operating at 45 kV and 40 mA. Chemical analysis of n-HAp and PLA_HAp composite films with varying weight percentages was conducted using a Thermo Scientific DXR Raman spectrometer. Raman spectra were recorded from 0 to 3500 cm⁻¹ with a laser power of 5 mW. Additionally, the chemical structure and functional groups present in the samples were analyzed by Fourier Transform Infrared (FTIR) spectroscopy using an IR Tracer-100, which offers high scanning speed and a resolution of 0.25 cm⁻¹. 2.7. Morphology Analysis The morphology and microstructure of the n-HAp and PLA_HAp composite films were imaged using a JEOL JSM-7200F field emission scanning electron microscope. The composite film samples were fixed onto SEM stubs using carbon tape followed by sputtering with Au-Pd coating for 45 seconds using a Hummer 6.2Vacuum sputter coater before SEM imaging. The n-HAp powder was imaged at an accelerating voltage of 5 kV and the particle distribution and fracture analysis of the PLA_HAp composite films were imaged at an accelerating voltage of 5kV. A JOEL-2010 Transmission Electron Microscope (TEM), operating at 80 kV was also used for the detailed shape and size imaging of the n-HAp synthesized. 2.8. Thermal Property Analysis. Thermal stability and weight loss of the synthesized n-HAp and PLA_HAp films were assessed using a TA Q500 Thermogravimetric Analyzer (TGA). Samples weighing 5–15 mg were placed in aluminum pans and heated under a nitrogen atmosphere while monitoring weight changes with increasing temperature. Thermal behavior of the PLA_HAp composite films was further investigated using a TA Q2000 Differential Scanning Calorimeter (DSC). Composite samples (5–15 mg) were sealed in hermetic pans and analyzed against a reference pan. DSC thermograms were recorded during heating and cooling cycles at a rate of 10°C/min, over a temperature range from − 20°C to 200°C, under a nitrogen atmosphere. 2.9. Mechanical Property Analysis. Tensile testing of the PLA_HAp composite films was conducted using a Zwick/Roell Z2.5 universal testing machine. The tests were carried out in accordance with the ASTM D882-10 standard, which applies to polymer films less than 1 mm thick. Film thickness was measured with a digital Vernier caliper offering a resolution of 0.001 mm. Composite film samples, measuring 150 mm in length and between 0.04 and 0.05 mm in thickness, were prepared for testing. Each sample was clamped between the upper and lower wedge grips of the Zwick/Roell Z2.5 machine, equipped with a 2.5 kN load cell, and tested at a constant crosshead speed of 50 mm/min to generate stress-strain curves [ 17 ]. 2.10 Biodegradation field experiment The biodegradation study of the blown film samples was carried out in a greenhouse that helps to mimic natural outdoor conditions. The soil for the study was collected from the agricultural field of the Department of Agricultural & Environmental Science, Tuskegee University, Alabama, USA (N: 32.4302 o , W:85.707 o ), and studies were conducted for 6 months from July 2024 to December 2024. The greenhouse conditions were maintained with a room temperature of 50–75 F, relative humidity of 50%, light period of 16/8, and light level of 500 µmol/m 2 /s throughout the experiment. The soil was sandy loam and acidic, with a pH range of 5.1. During the experiment, the soil temperature was between 43–67°F. The soil collected was primarily sieved through a wire mesh to remove unwanted gravel and plant remains and then filled into plastic pots (1000 ml). Six samples each from neat PLA, PLA_HAp 0.5, and PLA_HAp 1 were cut into rectangular samples of dimension 350 mm x 250 mm, buried at a depth of 6-7cm in plastic pots, and labeled accordingly. All the blown films were weighed before being placed inside the soil for the biodegradation study. The Gravimetric method [ 18 ] was used to determine the amount of water required to bring the soil to field capacity, which was established as 110 mL per pot. Soil moisture was subsequently maintained at field capacity throughout the experiment by regularly weighing the pots and replenishing any water loss through watering to restore the original weight. The plastic pots were watered at regular intervals of seven days, and three replicates from each set were picked out at 90 days and 180 days for biodegradation analysis. The blown film samples picked out from plastic pots were gently cleaned, washed in distilled water, and dried in an oven at 50 o C overnight to a constant weight before measuring weight loss. The dried samples were then kept in a desiccator for further characterization. 3. RESULTS AND DISCUSSIONS 3.1 Characterization of n-HAp powder Figure 2 (a) gives the XRD spectrum obtained for the n-HAp isolated from PPFS using the alkaline hydrolysis method. The XRD spectrum exhibits strong evident peaks of hydroxyapatite (JCPDS file # 01-080-3958) with distinct peaks of 2θ at 25.95, 32.24, 40.42, 46.69, 50.44, 53.30 Corresponding to (022), (112), (221), (222), (231) and (004) planes, respectively. The crystalline peaks of the alkaline hydrolysis synthesized n-HAp were calculated using the Debye-Scherrer equation given below in Eq. (1) D= \(\:\frac{K\lambda\:}{\beta\:Cos\:\theta\:}\) (1) Where D is the crystalline size in nm, K stands for the Scherrer constant, which is 0.94, λ denotes the diffraction wavelength of 1.54 A o , β denotes the FWHM of the considered peaks, and θ is the diffraction angle. The average particle size of the sample is determined by evaluating the distinct peaks of the XRD spectrum. The average particle size calculated from the Scherrer equation confirms that the hydroxyapatite isolated from PPFS is nanohydroxyapatite (n-HAp) with an average particle size of around 11.34 nm. The functional group identification of the n-HAp using FTIR is shown in Fig. 2 (b). The FTIR spectrum shows significant absorption bands of the phosphate group (PO 4 3− ) around 985–1080 cm − 1 and also the carbonyl group (CO 3 2− ) around 1415–1525 cm − 1 representing n-HAp [ 19 , 20 ]. The surface morphology of the PPFS and alkaline hydrolysis isolated n-HAp from PPFS is shown in Fig. 2 (c) & (d), respectively. The PPFS SEM image was distinct from the n-HAp SEM image with large lumps of agglomerated particles. However, the n-HAp isolated from PPFS highlights nano-sized particles agglomerated together exhibiting good agreement with the particle size calculated from the Scherrer equation given in Eq. (1). Figure 3 (a) shows the TEM image of the n-HAp isolated from PPFS revealing an interesting morphology of nanorod like structures. The Raman spectrum obtained for the n-HAp is presented in Fig. 3 (b) exhibiting the characteristic peak of PO 4 3− at 962 cm − 1 with a strong active P-O-P symmetric stretching mode of n-HAp [ 21 ]. The Raman band observed at 432 cm − 1 and 587 cm − 1 corresponds to PO 4 3− in triply degenerate bending mode and the band at 1054 cm − 1 represents the asymmetric stretching vibration of P-O bonds [ 22 ]. The thermal stability of the n-HAp studied under air and nitrogen atmosphere using TGA is given in Fig. 3 (c). TGA analysis of the n-HAp powder under nitrogen and air heated up to 950 o C exhibited a weight loss of 11% and 18%, respectively. The weight loss observed in TGA analysis is attributed to the small percentage of organic moieties present in n-HAp after the isolation process. 3.2 Characterization PLA_HAp Blown Films PLA_HAp with 0.25 wt.%, 0.5 wt.%, 0.75 wt.%, and 1 wt.% of n-HAp reinforced PLA composite blown films were extruded and further characterized for any possible chemical interaction and chemical bonding during composite formation. Figure 4 (a-b) gives the FTIR spectrum obtained for the PLA_HAp composite blown films compared with neat PLA blown films. The FTIR spectrum of PLA_HAp composite blown films exhibited no significant changes in the peaks compared with the neat PLA films. However, there were variations in the intensities of the peaks as shown in Fig. 4 (b). The Characteristic peaks of neat PLA include 2995 − 2850 cm − 1 attributes to the -CH 3 stretching, 1743 cm − 1 attributes to the -C = O stretching, 1454 cm − 1 and 1376 cm − 1 attributes to -C-H bending, 1080 cm − 1 attributes to the C-O-C stretching and 860 cm − 1 attributes to O-COO stretching. A distinguishable variation in the intensity of the peaks was observed around 2800–3000 cm − 1 for the PLA_HAp composite blown films compared with neat PLA as shown in Fig. 4 (b). A significant reduction of the peak intensity was observed compared with neat PLA as the filler concentration was increased from 0.25 to 0.75 wt. %. Previous studies have reported that a significant decrease in C–H peak intensities is linked to the formation of strong hydrogen bonds during polymer blending (Panickar & Rangari, 2024; Zhang et al., 2020). The –CH groups likely act as hydrogen donors, chemically bonding with the terminal hydroxyl groups in AH/HAp, which leads to the notable reduction in –CH intensities observed in the polymer composite. Additionally, this decrease in intensity has been attributed to the grafting of the filler onto the PLA matrix (Qin et al., 2017). FTIR analysis of the composite films confirms the presence of chemical bonding between n-HAp and the PLA matrix. Furthermore, Raman spectroscopy was used to characterize the PLA_HAp films and investigate possible chemical interactions between the PLA matrix and n-HAp (Fig. 4 (c)). The Raman spectrum of neat PLA showed characteristic peaks at 876, 1460, 1768, and 2848–3047 cm⁻¹, corresponding to the –C–COO, –CH, –C = O, and –CH vibrational groups, respectively. When comparing the Raman spectra of neat PLA and PLA_HAp composite films, no significant peak shifts or changes were detected. However, a small additional peak at 676 cm⁻¹ (Fig. 4 (d)) appeared in all PLA_HAp samples, attributed to the symmetric P–O–P stretching vibration of n-HAp (Andrade et al., 1999). This P–O–P vibration peak further confirms the chemical interaction between n-HAp and the PLA backbone. Such interaction likely contributes to the notable enhancement in the thermal and mechanical properties observed in the PLA_HAp composite blown films. 3.3 Thermal Characterization of PLA_HAp Blown Films Thermal property analysis of the PLA_HAp composite, in comparison to neat PLA blown films, was conducted using TGA and DSC. Figure 5 (a & b) presents the thermal degradation curves and DTG curves obtained for the PLA_HAp composite films (0.25, 0.5, 0.75, and 1 wt.% n-HAp in PLA) as well as for neat PLA films. The thermal degradation values gathered from the thermograms are summarized in Table 1 . The initial degradation temperature of the PLA_HAp composite films increased significantly by 15°C for 0.25 wt.% of n-HAp when compared to neat PLA and subsequently decreased by 9°C, 5°C, and − 7°C with increasing wt.% of 0.5, 0.75, and 1, respectively. This study reveals that a notably low concentration of n-HAp in PLA has enhanced the thermal stability of the PLA_HAp composite compared to neat PLA (≤ 0.75 wt.%). However, higher concentrations of HAp reduced the thermal stability of the polymer composite. It is noted that the thermal stability of the composites is influenced by the interfacial bonding within the composite. Akinodoyo et al. have reported that the electrostatic attraction of the Ca2 + ions in n-HAp and the -COO- functional groups can significantly affect the interfacial attraction in the polymer composite. The observed decrease in the thermal stability of the PLA_HAp composite in this study, with increasing filler concentration, can be attributed to the electrostatic interaction between the n-HAp and PLA. Table 1 TGA analysis Summary of PLA_HAp composite blown films Samples Initial degradation Temp ( o C) Final degradation Temp ( o C) Deriv Weight % Neat PLA 344.11 371.64 382.96 PLA_HAp 0.25 359.11 396.42 384.30 PLA_HAp 0.5 352.65 380.66 371.31 PLA_HAp 0.75 348.80 392.85 379.62 PLA_HAp 1 337.35 374.91 363.01 DSC thermograms of heating and cooling cycles of the PLA_HAp blown film samples were analyzed to understand the effect of n-HAp on the thermal properties of the PLA composite. Figure 5 (c&d) shows the heating and cooling DSC thermograms, respectively, of the PLA_HAp composite films. Table 2 summarizes the DSC heating curves obtained for neat PLA and PLA_HAp composite films. Thermal properties including glass transition temperature (Tg), melting temperature (Tm), and crystallinity (χ) were derived from the DSC thermograms. It was observed that the Tg of the PLA_HAp composite film samples decreased significantly compared to neat PLA films. The reduction in Tg is attributed to increased mobility in the polymer chains caused by the incorporation of n-HAp into the PLA matrix (Maiza et al., 2015). The crystallinity (χ) behavior of the PLA_HAp composite samples was calculated using Eq. (2) with data from the first heating cycle thermogram. χ = \(\:\frac{{\varDelta\:H}_{m}-{\varDelta\:H}_{C}}{{\varDelta\:H}_{m}^{o}}\) (2) Where ΔHm is the melting enthalpy of the samples (J/g), ΔHc is the crystallization enthalpy, and ΔH o m is the melting enthalpy of fully crystalline PLA, valued at 93.7 J/g. The crystallinity values calculated for the PLA films using Eq. (2) indicate that the presence of n-HAp reduces the crystallinity of the PLA composite films. This decrease is attributed to the small amount of n-HAp in the PLA matrix, which introduces more amorphous regions, thereby reducing polymer chain orientation and limiting their mobility. This leads to an increased degree of disorder within the PLA matrix (Akindoyo et al., 2018; Nedaipour et al., 2020). It has also been reported that reduced crystallinity may accelerate PLA degradation (Pantani & Sorrentino, 2013). A slight shift in the melting temperature of the PLA_HAp composite films was also observed, likely due to less stable crystal sizes within the polymer matrix (Pandele et al., 2020). Table 2 DSC analysis summary of PLA_HAp composite blown films Samples Glass Transition Temp T g ( o C) Crystallization Temp T CC ( o C) Crystallization enthalpy ΔH c Melting Temp T m ( o C) Melting enthalpy ΔH m Crystallinity %χ Neat PLA 58.65 88.29 16.41 170.15 36.35 21.28 PLA_HAp 0.25 49.80 94.85 20.33 171.51 36.05 16.77 PLA_HAp 0.5 50.55 93.95 19.81 171.37 36.54 17.85 PLA_HAp 0.75 53.31 92.0 18.36 168.38 36.34 19.18 PLA_HAp_1 49.60 94.16 19.10 168.25 35.88 17.93 3.4 Mechanical Characterization of PLA_HAp Blown Films The mechanical properties of the PLA composite blown films were compared with neat PLA films. Figure 6 (a) shows the stress vs strain curves obtained for the PLA blown film samples that highlight the influence of n-HAp in the PLA matrix. The steep slope of the neat PLA exhibits the high stiffness of the polymer. The reinforcement of the n-HAp at varying wt.% in PLA significantly changed the mechanical properties of the PLA films. Mechanical property analysis of hydroxyapatite in PLA at a relatively lower concentration of less than 1% has not been reported yet. However, hydroxyapatite at relatively high concentrations varying from 1–50% has been reported previously [ 23 – 25 ]. These studies reported that higher concentrations of hydroxyapatite exhibited improved tensile strength and then deteriorated at relatively higher concentrations. The Strain vs Stress curves of the PLA_HAp blown films loaded with 0.25 wt.%, 0.5 wt.%, 0.75 wt.%, and 1 wt.% exhibited reduced tensile strength compared to neat PLA films. This result can be related to the reduced crystallinity values determined from DSC thermograms in the present study. It has been reported that reduced crystallinity can reduce the tensile strength and stiffness of PLA, making it more flexible and softer. Table 3 . Summarized the average values of Young’s modulus, tensile strength, and elongation at break obtained for neat PLA and PLA_HAp composite samples. All PLA_HAp composite samples displayed reduced Young's modulus compared to neat PLA. It can be deduced that the reduced Young's modulus is due to the weak interfacial interaction between n-HAp and the polymer [ 26 ]. Among various wt.% of n-HAp in PLA, PLA_HAp 0.75 exhibited the maximum flexibility and elongation at break. The elongation at the break of PLA_HAp 0.75 showed an enhancement of 368% from the neat PLA film. As the wt.% further increased to 1% the tensile strength increased, and elongation at break was reduced for PLA_HAp 1 blown film. Mechanical property analysis of the PLA_HAp composite films shows that relatively low concentrations of n-HAp (0.5% and 0.75%) can significantly reduce the tensile strength and improve the elongation at the break of PLA polymer. Table 3 Summary of Tensile test data of PLA_HAp Blown Films Sample Youngs Modulus MPa Tensile, F max MPa Elongation at break (%) Neat PLA 2286.02 ± 18.30 62.56 ± 8.43 7.41 ± 2.59 PLA_HAp 0.25 846.6 ± 14.20 53.88 ± 3.43 12.60 ± 3.46 PLA_HAp 0.5 858.75 ± 11.16 29.19 ± 2.16 28.69 ± 2.69 PLA_HAp 0.75 987.91 ± 13.34 32.27 ± 2.72 34.67 ± 2.13 PLA_HAp 1 802.4 ± 15.37 42.07 ± 2.31 14.06 ± 3.15 The fracture analysis of the blown films after the tensile testing was performed to understand the mode of fracture and the mechanism behind the failure. The fractography of neat PLA and PLA_HAp 0.75% blown films are given in Figs. 6 (b) and (c), respectively. As shown in Fig. 6 (b), the neat PLA film exhibited fracture surface with minimal ruptures and less plastic deformations, which is identified as a brittle fracture. The PLA_HAp 0.75 wt% (Fig. 6 (c)) exhibited multiple micro-cracks and ruptures all over the fractured surface possibly due to the plastic deformation that took place during tensile testing. The fracture analysis infers that the n-HAp has significantly improved the flexibility of the composite blown film that can deform readily under stress and the elongation at break obtained for PLA_HAp 0.75 was 34.8%. It has been reported that the fillers reinforced in the PLA matrix can help to evenly distribute the stress, permitting greater deformation before failure [ 27 , 28 ]. 3.5 Soil Biodegradability Studies of PLA_HAp Blown Films The soil degradation study of the neat PLA and n-HAp reinforced PLA blown film samples was studied to investigate the effect of n-HAp filler in accelerating the biodegradation property of PLA composite. Figure 7 (a) shows the labeled plastic pots with blown film samples buried in them for biodegradation studies in the greenhouse. Six samples each from neat PLA, PLA_HAP 0.5, and PLA_HAp 1 with labels R1, R2, R3, R4, R5, and R6 were buried in the soil for the soil degradation studies. The first set of three samples R1, R2, and R3 were picked out after 90 days and the second set of samples R4, R5, and R6 were picked out after 180 days from the soil. Each blown film sample picked out from the soil was cleaned, washed with distilled water, and dried before it was measured for mass loss. The degradation kinetics was determined by calculating the mass loss that occurred in the blown film samples while in the soil. The mass loss (ML) was calculated using the Eq. (2).[ 29 ] ML= \(\:\frac{{\text{m}}_{\text{o}}-{\text{m}}_{\text{t}}}{{\text{m}}_{\text{o}}}\text{X}100\) (2) Where m o is the initial mass of the sample and m t denotes the sample mass after the degradation time. The average mass loss calculated from Eq. (2) for neat PLA, PLA_HAP 0.5, and PLA_HAP 1 samples is given in Fig. 7 (b). The ML analysis of the samples reveals that neat PLA films exhibited significantly low degradation of 0.6% after 180 days. Whereas PLA_HAp 0.5 exhibited an average ML of 1.2% and 3.6% for samples taken out at 90 days and 180 days, respectively. PLA_HAP 1 exhibited an average ML of 1.2% and 2% for samples taken out at 90 days and 180 days, respectively. The soil biodegradation studies of the neat PLA and PLA_HAp 0.5 reveal that the effect of HAp has significantly enhanced the degradation of the composite film by 500% after 180 days compared with neat PLA. These results show that the presence of n-HAp in the PLA matrix has significantly improved the biodegradation property of the PLA_HAp composite films. Hydrolysis is one of the key factors in polymer degradation, initiating a chemical reaction between water molecules and polymer bonds that effectively breaks the polymer chains into fragments. PLA is a biobased polymer that is not easily degradable at ambient temperature, which significantly reduces the hydrolysis rate. In the present work, hydroxyapatite, being a hydrophilic material, has significantly enhanced the hydrolysis rate in the polymer composite, leading to the breakdown of ester molecules. Although the PLA_HAp 1 film shows an increase in the ML over time, the ML is reduced compared to PLA_HAp 0.5, possibly because the higher concentration of HAp in the PLA composite made the films more hydrophilic, which hindered the bulk erosion of the films. Gazvoda et al. have reported that during soil degradation in hydrophilic films, degradation occurs on the surface, initiating surface erosion. It has also been reported that hydrophilicity can significantly reduce the enzymatic degradation of the polymer, as excess water molecules can restrict the enzyme’s access to the bulk, resulting in only surface erosion occurring [ 30 , 31 ]. Figure 7 (c) shows the photographs of the blown film samples of neat PLA, PLA_HAp 0.5, and PLA_HAp compared with before and after soil degradation analysis. A significant change in the film transparency was observed for the PLA_HAp 0.5 and PLA_HAp 1 blown film samples taken out from the soil at 90 and 180 days, respectively. Compared to the neat PLA films the PLA_HAP 0.5, and PLA_HAp 1 samples changed to a milky white color as shown in Fig. 7 (c) after 90 and 180 days. Siakeng et al.[ 32 ] have illustrated the color changes in biocomposite samples with exposure time. The significant reduction in the transparency of the PLA_HAp 0.5 and PLA_HAp 1 confirms the accelerated hydrolysis rate that occurred in the biocomposite samples that resulting in mass loss with time. 3.5.1 FTIR analysis One sample each from neat PLA, PLA_HAP 0.5, and PLA_HAp with the highest mass loss was further characterized for biodegradation studies. Figure 8 (a& b) shows the FTIR spectrum obtained for neat PLA_R2, PLA_HAp 0.5_R2, and PLA_HAp 1_R1 samples and Neat PLA_R5, PLA_HAp 0.5_R4, and PLA_HAp 1_R4 samples from 90 days and 180 days of soil degradation, respectively. FTIR spectrum of the blown film samples from soil was obtained to understand any change in chemical bonding that occurs during the biodegradation in soil. The FTIR spectrum reveals significant changes in the intensities of the functional groups after soil degradation. An increase in the intensity at 1384 cm − 1 , 1460 cm − 1 , and 1768 cm − 1 was observed for neat PLA_R2, PLA_HAp 0.5_R2, and PLA_HAp 1_R1 samples taken out at 90 days. The increase in intensity at 1384 cm − 1 , and 1460 cm − 1 shows the PLA degradation attributed to the C-H deformational peak of the CH 3 group of PLA[ 33 ]. The increase in the intensity at 1768 cm − 1 is attributed to the hydrolytic degradation of PLA due to the increase in carboxylic groups in the PLA matrix [ 34 ] However, the neat PLA degradation was significantly low compared to the PLA composite films from the ML calculation possibly because of the rigid long chain and the presence of methyl group that makes it more hydrophobic, thus restricting hydrolysis.[ 35 ] The significantly low intensities of neat PLA around 2995 − 2850 cm − 1 peaks attributed to the -CH 3 stretching of the alkyl chains infers a low degradation rate in soil. Figure 8 (b) shows broad low intensity peaks at 2337–2358 cm − 1 in the film samples taken out at 180 days attributed to C = N functional groups because of the long term soil exposure[ 36 ]. PLA_HAp 0.5_R2 and PLA_HAp 0.5_R4 exhibited significantly high intensity around 2995 − 2850 cm − 1 peaks attributed to the -CH 3 stretching of the alkyl chains infers a high degradation rate in soil relevant to ML measurement.[ 37 ]The FTIR spectrum showed significantly high intensity for C-O, C = O and C-H bonds for PLA_HAp composite samples compared to neat PLA. Zamir et al [ 38 ]. have also reported a similar trend in increased intensity for PLA/g-SNCs compared to neat PLA. The FTIR analysis confirms that the n-HAp in PLA has significantly improved the hydrolysis reaction and initiated microbial activity in the composite films resulting in better degradation in PLA_HAp film samples in soil. Table 4 TGA analysis: Summary of PLA_HAp composite blown films after soil degradation analysis. Samples Initial degradation Temp ( o C) Final degradation Temp ( o C) Deriv Weight % Neat PLA_R2 342.34 378.68 368.57 Neat PLA_R5 353.08 387.10 376.50 PLA_HAp 0.5_R2 341.02 381.75 368.39 PLA_HAp 0.5_R4 318.29 351.77 343.27 PLA_HAp 1_R1 330.29 347.05 339.86 PLA_HAp 1_R4 328.95 365.44 351.95 3.5.2 Thermogravimetric Analysis The thermal stability of the soil buried film samples was investigated using thermogravimetric analysis. Figure 8 (c) shows the TGA curves obtained for the soil buried samples of neat PLA, PLA_HAp 0.5, and PLA_HAp 1 samples taken out from the soil at 90 days and 180 days, respectively. The summary of the TGA thermograms obtained for the soil buried samples is given in Table 4 . The initial degradation temperatures (Table 1 ) obtained for neat PLA, PLA_HAp 0.5, and PLA_HAp 1 before soil degradation were 344.11 o C, 352.65 o C, and 337.35 o C, respectively. whereas the initial degradation temperature obtained for neat PLA, PLA_HAp 0.5, and PLA_HAp 1 exhibited a significant reduction in the initial degradation temperature after 90 and 180 days. It was observed that the PLA_HAp 0.5 and PLA_HAp 1 film samples (after 90 and 180 days) experienced weight loss at approximately 100°C. This was attributed to the enhanced hydrophilicity caused by n-HAp as a filler, which promoted soil degradation. PLA_HAp 0.5_R4 reveals the lowest thermal stability with an initial degradation temperature of 318.29 o C with maximum soil degradation after 180 days. TGA thermograms obtained for the soil buried samples showed good agreement with the ML calculations of the samples. The thermal degradation of the samples again confirms the deterioration of the samples by microbial and enzymatic degradation. 3.5.3 Morphology Changes The morphology of the PLA composite films was analyzed using SEM imaging before and after 90 and 180 days of soil degradation. Figure 8 (a-c) shows the SEM image of neat PLA, PLA_HAp 0.5, and PLA_HAp 1 film samples before the soil burial test with smooth surfaces and flow lines in the direction of extrusion. Figure 8 (d-f) shows the SEM image of neat PLA_R2, PLA_HAp 0.5_R2, and PLA_HAp 1_R1 film samples after 90 days of soil biodegradation. Figure 8 (g-i) shows the SEM image of neat PLA_R5, PLA_HAp 0.5_R4, and PLA_HAp 1_R4 film samples after 180 days of soil biodegradation. A significant surface deterioration was observed in the soil buried samples that progressed with burial time. The Neat PLA films exhibited increased roughness and tiny protrusions on the surface with burial time, which indicates the starting of deterioration [ 39 ]. In the case of PLA_HAp 0.5 and PLA_HAp 1 film samples, microcracks and fibrillations were visible on the sample with burial time. It was understood that the fibrillations and increased roughness on the surface of the PLA composite samples are attributed to the presence of n-HAp. SEM Image analysis of the soil buried film samples reveals the accelerated surface deterioration due to microbial etching. CONCLUSIONS This study demonstrates that incorporating small amounts of nano-hydroxyapatite (n-HAp) into a PLA matrix significantly enhances the thermal, mechanical, and biodegradable properties of the composite samples compared to neat PLA. A simple and feasible alkaline hydrolysis method was employed to extract n-HAp from pink perch fish scales. XRD analysis confirmed that the isolated powder is hydroxyapatite with a particle size of approximately 11–12 nm. Various concentrations of n-HAp (0.25 wt.%, 0.5 wt.%, 0.75 wt.%, and 1 wt.%) were incorporated into the PLA matrix using solution blending followed by blown film extrusion. The thermal, mechanical, and biodegradable properties of these composites were systematically analyzed. Thermal analysis via TGA and DSC revealed that even low concentrations of n-HAp significantly influence the initial degradation temperature, glass transition temperature, and crystallinity of the composite films. Tensile testing indicated that PLA_HAp 0.75 exhibited reduced tensile strength but enhanced elongation at break. A 180-day biodegradation study in soil demonstrated that the presence of n-HAp accelerates the hydrolysis process, improving the soil degradation rate of the composite films by 500% compared to neat PLA. Overall, this study highlights the effectiveness of n-HAp in enhancing the functional properties of PLA-based composites. Declarations Author Contribution CRediT authorship contribution statementRadhika Panickar: Writing -original draft, Data Curation, Methodology,Investigation. Devotha Mwazembe: Polymer degradation and soil testing,Benny Alexander, Reviewing, barrier testing, Edwin Freeman: Writing – re-view & editing, Validation. Desmond Mortley: Soil testing and methodology,Vijaya Rangari: Writing – review & editing, Methodology, Validation. Supervision, Resources Acknowledgement The authors would like to acknowledge financial support from MARS Wrigley, Global Innovation Center, Chicago, IL., NSF-NRT# 2125606, NSF-CREST #1735971, and NSF-DMR# 2117242 Data Availability Data will be provided up on request References Atiwesh G, Mikhael A, Parrish CC, et al (2021) Environmental impact of bioplastic use: A review. 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Supplementary Files GraphicalAbstractPLAHApAH.docx Cite Share Download PDF Status: Published Journal Publication published 20 Feb, 2026 Read the published version in Journal of Polymers and the Environment → Version 1 posted Editorial decision: Revision requested 29 Aug, 2025 Reviews received at journal 09 Aug, 2025 Reviews received at journal 04 Aug, 2025 Reviewers agreed at journal 01 Aug, 2025 Reviewers agreed at journal 01 Aug, 2025 Reviews received at journal 31 Jul, 2025 Reviews received at journal 30 Jul, 2025 Reviewers agreed at journal 30 Jul, 2025 Reviewers agreed at journal 30 Jul, 2025 Reviewers agreed at journal 30 Jul, 2025 Reviewers invited by journal 29 Jul, 2025 Editor assigned by journal 26 Jul, 2025 Submission checks completed at journal 26 Jul, 2025 First submitted to journal 25 Jul, 2025 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. 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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-7216042","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":494498459,"identity":"bda8f930-e7ce-45cc-a4b9-113fbbe4ab04","order_by":0,"name":"Radhika Panickar","email":"","orcid":"","institution":"Tuskegee University","correspondingAuthor":false,"prefix":"","firstName":"Radhika","middleName":"","lastName":"Panickar","suffix":""},{"id":494498460,"identity":"a7745314-4c51-48a8-8714-016aa393982a","order_by":1,"name":"Devotha Mwazembe","email":"","orcid":"","institution":"Tuskegee 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10:10:15","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":505766,"visible":true,"origin":"","legend":"\u003cp\u003ea) XRD analysis of n-HAp from alkaline hydrolysis, b) FTIR spectrum obtained for n-HAp from alkaline hydrolysis,c) SEM image of PPFS, and d) SEM image of n-HAp from alkaline hydrolysis.\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-7216042/v1/9c56e66f8ca0a9e08d2bb454.png"},{"id":88234457,"identity":"571e5516-ffc7-487d-973d-12f7dce25332","added_by":"auto","created_at":"2025-08-04 10:02:15","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":2483038,"visible":true,"origin":"","legend":"\u003cp\u003ea) TEM image of the n-HAp synthesized, b) Raman spectrum of the n-HAp synthesized, and c) TGA of the n-HAp synthesized\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-7216042/v1/be032c6323ecbbda45924ebd.png"},{"id":88235459,"identity":"094b9ebd-28e6-45e3-a5c0-6a757b0e58eb","added_by":"auto","created_at":"2025-08-04 10:10:15","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":661674,"visible":true,"origin":"","legend":"\u003cp\u003eCharacterization of the PLA_HAp composite blown films using (a-b) FTIR spectrum and (c-d) Raman spectrum\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-7216042/v1/9336bbfb39eae03432b3c58b.png"},{"id":88234470,"identity":"d2f2181b-2ee9-48b9-b59c-03692d5a9d1b","added_by":"auto","created_at":"2025-08-04 10:02:15","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":604310,"visible":true,"origin":"","legend":"\u003cp\u003eThermal characterization of PLA_HAp composite blown films a) TGA analysis, b) DTG analysis, c) DSC thermogram during the heating cycle, and d) DSC thermogram during the cooling cycle.\u003c/p\u003e","description":"","filename":"floatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-7216042/v1/ecd09fff3375840c90249b35.png"},{"id":88235458,"identity":"1c7a6670-e8fa-4ac1-8f2b-d1d2e395d505","added_by":"auto","created_at":"2025-08-04 10:10:15","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":964790,"visible":true,"origin":"","legend":"\u003cp\u003ea) Stress vs Strain curves obtained for PLA_HAp composite blown films and (b-c) fracture analysis of blown films using SEM after tensile testing\u003c/p\u003e","description":"","filename":"floatimage6.png","url":"https://assets-eu.researchsquare.com/files/rs-7216042/v1/c4243938c59c1d09777e6caa.png"},{"id":88235462,"identity":"54568f65-990a-434f-93b4-5623650aeec9","added_by":"auto","created_at":"2025-08-04 10:10:16","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":567574,"visible":true,"origin":"","legend":"\u003cp\u003ea) PLA composite blown film samples buried in soil for biodegradation study, b) Comparing the PLA blown film samples before and after soil burial taken out after 90 days and 180 days, and c) bar graph showing the average weight loss recorded for PLA blown film samples after 90 and 180 days.\u003c/p\u003e","description":"","filename":"floatimage7.png","url":"https://assets-eu.researchsquare.com/files/rs-7216042/v1/569ec46e78fdca4667a9c84d.png"},{"id":88235463,"identity":"7b39c694-837e-4d00-820e-7a90b60a2fee","added_by":"auto","created_at":"2025-08-04 10:10:16","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":564474,"visible":true,"origin":"","legend":"\u003cp\u003ea\u0026amp;b) FTIR spectrum obtained for PLA composite blown film samples after soil burial studies, and c) TGA obtained for blown film samples after 90 and 180 days of soil degradation.\u003c/p\u003e","description":"","filename":"floatimage8.png","url":"https://assets-eu.researchsquare.com/files/rs-7216042/v1/587ae27fe8cbf9995c3dc220.png"},{"id":88234477,"identity":"2863f835-b83d-4893-b0a7-c99b1944b84b","added_by":"auto","created_at":"2025-08-04 10:02:16","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":903167,"visible":true,"origin":"","legend":"\u003cp\u003eSEM images of the blown film samples after soil degradation (a-c) 90 days and (d-f) 180 days\u003c/p\u003e","description":"","filename":"floatimage9.png","url":"https://assets-eu.researchsquare.com/files/rs-7216042/v1/b9326e2c7a11201c7f577949.png"},{"id":103251088,"identity":"790d534e-4dbc-4c93-8cd2-67ba4d40248e","added_by":"auto","created_at":"2026-02-23 16:04:12","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":8286068,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7216042/v1/ea1ff641-69be-45dd-8e48-ca41f3ee15a9.pdf"},{"id":88234459,"identity":"902f5eda-00ad-4a65-8778-189639afbd98","added_by":"auto","created_at":"2025-08-04 10:02:15","extension":"docx","order_by":0,"title":"","display":"","copyAsset":false,"role":"supplement","size":513304,"visible":true,"origin":"","legend":"","description":"","filename":"GraphicalAbstractPLAHApAH.docx","url":"https://assets-eu.researchsquare.com/files/rs-7216042/v1/b4f0e492fd00081fde253155.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Investigations on Thermomechanical and Biodegradable Properties of Alkaline Hydrolysis Isolated Nano Hydroxyapatite Reinforced Polylactic Acid Composite Blown Films for sustainable Packaging","fulltext":[{"header":"1. INTRODUCTION","content":"\u003cp\u003ePetroleum-based plastics are highly versatile materials used in various applications in daily life, including food packaging, construction, consumer products, the medical field, etc. In 2023, global plastic consumption exceeded 400\u0026nbsp;million metric tons and continues to rise annually. A major concern associated with plastic products is their extensive pollution in landfills and water bodies, which severely impacts the entire ecosystem, including plants, animals, and human health [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. Biodegradable polymers, which can naturally break down in the environment, offer an effective solution to address the increasing concern over the accumulation of non-biodegradable petroleum-based plastics[\u003cspan additionalcitationids=\"CR4\" citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eAmong the diverse variety of biobased polymers, Polylactic acid (PLA) synthesized from the ring opening polymerization of lactide offers promising properties including biodegradability, biocompatibility, good tensile strength, and widespread availability at a reasonable price[\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. PLA is extensively utilized in medical applications due to its excellent biocompatibility and ability to degrade within the body [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. However, PLA possesses inherent disadvantages such as low elasticity, high stiffness with low elongation at break, low thermal stability, moderate water resistance, and limited biodegradability in normal environments. Although PLA is generally recognized as safe (GRAS) for food contact surfaces, these disadvantages make it less suitable for use in food packaging applications. It has been reported that reinforcing the PLA matrix using appropriate fillers at desired weight percentages is an effective method to enhance the thermal, mechanical, and biodegradability properties of PLA[\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eVarious types of natural fillers, including different types of nanofibers [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e], nanocellulose [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e, \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e], and other additives have been reported to increase the physicochemical properties. Among these, hydroxyapatite (HAp), a natural mineral found in marine animal (fish and mollusks) bones and teeth, has been extensively studied as an effective filler in polymer composites, particularly for biomedical applications, due to its exceptional physicochemical properties, such as degradability, stability, and biocompatibility [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. However, its use in food packaging applications has not been widely explored. In this present study, extracting HAp from fish scales facilitates the recycling of fish industry byproducts, offering a sustainable and promising filler to enhance PLA properties. HAp reinforced PLA composite blown films for food packaging applications were prepared and investigated for thermal, mechanical, and biodegradable properties.\u003c/p\u003e"},{"header":"2. Materials and Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003e2.1. Materials\u003c/h2\u003e\u003cp\u003en-HAp for the present work was isolated from pink perch fish scales (PPFS) procured from Nizona Inc., Mumbai, India. The biodegradable polymer PLA 4032D for composite preparation was purchased from Natureworks LLC, USA. Sodium hydroxide and acetic acid for the chemical treatment of PPFS were purchased from Sigma Aldrich. Chloroform (\u0026ge;\u0026thinsp;99.8% with 0.5- 1% ethanol as a stabilizer), used as a solvent for dissolving PLA pellets, was procured from Sigma-Aldrich (St. Louis, MO, USA).\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\u003ch2\u003e2.2. Alkaline Hydrolysis synthesis of n-HAp\u003c/h2\u003e\u003cp\u003eThe n-HAp in this study was synthesized using the alkaline hydrolysis method, with a schematic representation of the synthesis process shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. Initially, PPFS is cleaned with distilled water and dried in an oven. The cleaned PPFS is then ground into a fine powder using a cryogenic freeze mill (6875D freezer/mill) by SPEX SamplePrep. A 10 g sample of the PPFS powder is treated with 0.5M NaOH solution and stirred for 5 hours on a magnetic stirrer to dissolve the organic matter. To remove any residual organic material and neutralize the solution, 0.5M acetic acid is added. The solution is then centrifuged multiple times with distilled water to wash away any remaining organic matter, isolating the n-HAp. The white residue is dried in an oven at 70\u0026deg;C overnight to remove moisture and to obtain the n-HAp powder represented as AH_HAp, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\u003ch2\u003e2.3. Preparation of PLA_HAp Composite\u003c/h2\u003e\u003cp\u003eA simple method of solution blending was employed for the reinforcement of n-HAp in the PLA matrix. Chloroform is one of the best solvents for dissolving PLA pellets in the solution blending technique. Different weight percentages of n-HAp: 0.25 wt. %, 0.5 wt. %, 0.75 wt. %, and 1 wt. % were added to PLA for the PLA_HAp composite preparation. The n-HAp particles weighed at different wt.% were initially added to chloroform and magnetically stirred for 30 minutes for the uniform dispersion of the particles in the solution. Then PLA pellets were added to the same solution followed by magnetic stirring for 5 hours to dissolve the PLA pellets completely and form the PLA_HAp composite solution. The solution was transferred to an aluminum tray and placed under a fume hood overnight to evaporate all the chloroform to obtain a thin sheet of PLA_HAp composite.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e\u003ch2\u003e2.4. Preparation of PLA_HAp Composite Filaments\u003c/h2\u003e\u003cp\u003eThe prepared PLA_HAp composite sheets were shredded into small pieces and extruded into filaments using a Filabot EX2 single-screw filament extruder. Filaments with 0.25 wt. %, 0.5 wt. %, 0.75 wt. %, and 1 wt. % of n-HAp in PLA composite were extruded. The filaments were extruded out at an extruder temperature of 170 \u003csup\u003eo\u003c/sup\u003eC (melting temperature of PLA). The single screw extruder speed was adjusted to maintain the filament thickness around 1.6 mm to 1.85 mm. The filaments extruded out from the extruder nozzle were passed through an airpath and winded on a spool at the other end of the filament extruder.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e\u003ch2\u003e2.5. Preparation of PLA_HAp Composite Blown Films\u003c/h2\u003e\u003cp\u003ePLA_HAp composite filaments containing 0.25 wt.%, 0.5 wt.%, 0.75 wt.%, and 1 wt.% of n-HAp were first extruded and then pelletized using a Filabot pelletizer in preparation for blown film extrusion. Blown films were produced using an Ultra Microfilm Blowing Line (model LUMF-150) equipped with a single-screw extruder from Lab Tech Engineering Company LTD. The extruder featured a conical single screw with a length-to-diameter (L/D) ratio of 30, a feed diameter of 18 mm, and a terminal diameter of 8 mm. Film extrusion was performed at a screw speed of 50\u0026ndash;60 rpm, with barrel and die temperatures maintained at 340\u0026deg;F (170\u0026deg;C) and 325\u0026deg;F (163\u0026deg;C), respectively. The extruded films were then guided through a series of spring-loaded nip rolls toward a winding bobbin located at the opposite end of the extrusion setup [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e].\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\u003ch2\u003e2.6. Characterization Techniques\u003c/h2\u003e\u003cp\u003eThe composition and identification of n-HAp and PLA_HAp composite films were performed using a RIGAKU SmartLab X-ray diffractometer with monochromatic Copper Kα1 radiation. Samples were scanned over a 2θ range of 5\u0026deg; to 80\u0026deg; at a scan rate of 5\u0026deg; per minute, operating at 45 kV and 40 mA. Chemical analysis of n-HAp and PLA_HAp composite films with varying weight percentages was conducted using a Thermo Scientific DXR Raman spectrometer. Raman spectra were recorded from 0 to 3500 cm⁻\u0026sup1; with a laser power of 5 mW. Additionally, the chemical structure and functional groups present in the samples were analyzed by Fourier Transform Infrared (FTIR) spectroscopy using an IR Tracer-100, which offers high scanning speed and a resolution of 0.25 cm⁻\u0026sup1;.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e\u003ch2\u003e2.7. Morphology Analysis\u003c/h2\u003e\u003cp\u003eThe morphology and microstructure of the n-HAp and PLA_HAp composite films were imaged using a JEOL JSM-7200F field emission scanning electron microscope. The composite film samples were fixed onto SEM stubs using carbon tape followed by sputtering with Au-Pd coating for 45 seconds using a Hummer 6.2Vacuum sputter coater before SEM imaging. The n-HAp powder was imaged at an accelerating voltage of 5 kV and the particle distribution and fracture analysis of the PLA_HAp composite films were imaged at an accelerating voltage of 5kV. A JOEL-2010 Transmission Electron Microscope (TEM), operating at 80 kV was also used for the detailed shape and size imaging of the n-HAp synthesized.\u003c/p\u003e\u003cp\u003e\u003cb\u003e2.8. Thermal Property Analysis.\u003c/b\u003e Thermal stability and weight loss of the synthesized n-HAp and PLA_HAp films were assessed using a TA Q500 Thermogravimetric Analyzer (TGA). Samples weighing 5\u0026ndash;15 mg were placed in aluminum pans and heated under a nitrogen atmosphere while monitoring weight changes with increasing temperature. Thermal behavior of the PLA_HAp composite films was further investigated using a TA Q2000 Differential Scanning Calorimeter (DSC). Composite samples (5\u0026ndash;15 mg) were sealed in hermetic pans and analyzed against a reference pan. DSC thermograms were recorded during heating and cooling cycles at a rate of 10\u0026deg;C/min, over a temperature range from \u0026minus;\u0026thinsp;20\u0026deg;C to 200\u0026deg;C, under a nitrogen atmosphere.\u003c/p\u003e\u003cp\u003e\u003cb\u003e2.9. Mechanical Property Analysis.\u003c/b\u003e Tensile testing of the PLA_HAp composite films was conducted using a Zwick/Roell Z2.5 universal testing machine. The tests were carried out in accordance with the ASTM D882-10 standard, which applies to polymer films less than 1 mm thick. Film thickness was measured with a digital Vernier caliper offering a resolution of 0.001 mm. Composite film samples, measuring 150 mm in length and between 0.04 and 0.05 mm in thickness, were prepared for testing. Each sample was clamped between the upper and lower wedge grips of the Zwick/Roell Z2.5 machine, equipped with a 2.5 kN load cell, and tested at a constant crosshead speed of 50 mm/min to generate stress-strain curves [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e].\u003c/p\u003e\u003cp\u003e\u003cb\u003e2.10 Biodegradation field experiment\u003c/b\u003e\u003c/p\u003e\u003cp\u003eThe biodegradation study of the blown film samples was carried out in a greenhouse that helps to mimic natural outdoor conditions. The soil for the study was collected from the agricultural field of the Department of Agricultural \u0026amp; Environmental Science, Tuskegee University, Alabama, USA (N: 32.4302\u003csup\u003eo\u003c/sup\u003e, W:85.707\u003csup\u003eo\u003c/sup\u003e), and studies were conducted for 6 months from July 2024 to December 2024. The greenhouse conditions were maintained with a room temperature of 50\u0026ndash;75 F, relative humidity of 50%, light period of 16/8, and light level of 500 \u0026micro;mol/m\u003csup\u003e2\u003c/sup\u003e/s throughout the experiment. The soil was sandy loam and acidic, with a pH range of 5.1. During the experiment, the soil temperature was between 43\u0026ndash;67\u0026deg;F. The soil collected was primarily sieved through a wire mesh to remove unwanted gravel and plant remains and then filled into plastic pots (1000 ml). Six samples each from neat PLA, PLA_HAp 0.5, and PLA_HAp 1 were cut into rectangular samples of dimension 350 mm x 250 mm, buried at a depth of 6-7cm in plastic pots, and labeled accordingly. All the blown films were weighed before being placed inside the soil for the biodegradation study. The Gravimetric method [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e] was used to determine the amount of water required to bring the soil to field capacity, which was established as 110 mL per pot. Soil moisture was subsequently maintained at field capacity throughout the experiment by regularly weighing the pots and replenishing any water loss through watering to restore the original weight. The plastic pots were watered at regular intervals of seven days, and three replicates from each set were picked out at 90 days and 180 days for biodegradation analysis. The blown film samples picked out from plastic pots were gently cleaned, washed in distilled water, and dried in an oven at 50\u003csup\u003eo\u003c/sup\u003eC overnight to a constant weight before measuring weight loss. The dried samples were then kept in a desiccator for further characterization.\u003c/p\u003e\u003c/div\u003e"},{"header":"3. RESULTS AND DISCUSSIONS","content":"\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e\u003ch2\u003e3.1 Characterization of n-HAp powder\u003c/h2\u003e\u003cp\u003eFigure \u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e (a) gives the XRD spectrum obtained for the n-HAp isolated from PPFS using the alkaline hydrolysis method. The XRD spectrum exhibits strong evident peaks of hydroxyapatite (JCPDS file # 01-080-3958) with distinct peaks of 2θ at 25.95, 32.24, 40.42, 46.69, 50.44, 53.30\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eCorresponding to (022), (112), (221), (222), (231) and (004) planes, respectively. The crystalline peaks of the alkaline hydrolysis synthesized n-HAp were calculated using the Debye-Scherrer equation given below in Eq.\u0026nbsp;(1)\u003c/p\u003e\u003cp\u003eD= \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\frac{K\\lambda\\:}{\\beta\\:Cos\\:\\theta\\:}\\)\u003c/span\u003e\u003c/span\u003e (1)\u003c/p\u003e\u003cp\u003eWhere D is the crystalline size in nm, K stands for the Scherrer constant, which is 0.94, λ denotes the diffraction wavelength of 1.54 A\u003csup\u003eo\u003c/sup\u003e, β denotes the FWHM of the considered peaks, and θ is the diffraction angle. The average particle size of the sample is determined by evaluating the distinct peaks of the XRD spectrum. The average particle size calculated from the Scherrer equation confirms that the hydroxyapatite isolated from PPFS is nanohydroxyapatite (n-HAp) with an average particle size of around 11.34 nm.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe functional group identification of the n-HAp using FTIR is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e(b). The FTIR spectrum shows significant absorption bands of the phosphate group (PO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e3\u0026minus;\u003c/sup\u003e) around 985\u0026ndash;1080 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and also the carbonyl group (CO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e2\u0026minus;\u003c/sup\u003e) around 1415\u0026ndash;1525 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e representing n-HAp [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e, \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. The surface morphology of the PPFS and alkaline hydrolysis isolated n-HAp from PPFS is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e(c) \u0026amp; (d), respectively. The PPFS SEM image was distinct from the n-HAp SEM image with large lumps of agglomerated particles. However, the n-HAp isolated from PPFS highlights nano-sized particles agglomerated together exhibiting good agreement with the particle size calculated from the Scherrer equation given in Eq.\u0026nbsp;(1).\u003c/p\u003e\u003cp\u003eFigure \u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e (a) shows the TEM image of the n-HAp isolated from PPFS revealing an interesting morphology of nanorod like structures. The Raman spectrum obtained for the n-HAp is presented in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e (b) exhibiting the characteristic peak of PO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e3\u0026minus;\u003c/sup\u003e at 962 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e with a strong active P-O-P symmetric stretching mode of n-HAp [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. The Raman band observed at 432 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 587 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e corresponds to PO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e3\u0026minus;\u003c/sup\u003e in triply degenerate bending mode and the band at 1054 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e represents the asymmetric stretching vibration of P-O bonds [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. The thermal stability of the n-HAp studied under air and nitrogen atmosphere using TGA is given in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e(c). TGA analysis of the n-HAp powder under nitrogen and air heated up to 950 \u003csup\u003eo\u003c/sup\u003eC exhibited a weight loss of 11% and 18%, respectively. The weight loss observed in TGA analysis is attributed to the small percentage of organic moieties present in n-HAp after the isolation process.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec12\" class=\"Section2\"\u003e\u003ch2\u003e3.2 Characterization PLA_HAp Blown Films\u003c/h2\u003e\u003cp\u003ePLA_HAp with 0.25 wt.%, 0.5 wt.%, 0.75 wt.%, and 1 wt.% of n-HAp reinforced PLA composite blown films were extruded and further characterized for any possible chemical interaction and chemical bonding during composite formation. Figure\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e (a-b) gives the FTIR spectrum obtained for the PLA_HAp composite blown films compared with neat PLA blown films. The FTIR spectrum of PLA_HAp composite blown films exhibited no significant changes in the peaks compared with the neat PLA films. However, there were variations in the intensities of the peaks as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e(b). The Characteristic peaks of neat PLA include 2995\u0026thinsp;\u0026minus;\u0026thinsp;2850 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e attributes to the -CH\u003csub\u003e3\u003c/sub\u003e stretching, 1743 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e attributes to the -C\u0026thinsp;=\u0026thinsp;O stretching, 1454 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 1376 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e attributes to -C-H bending, 1080 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e attributes to the C-O-C stretching and 860 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e attributes to O-COO stretching. A distinguishable variation in the intensity of the peaks was observed around 2800\u0026ndash;3000 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e for the PLA_HAp composite blown films compared with neat PLA as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e(b). A significant reduction of the peak intensity was observed compared with neat PLA as the filler concentration was increased from 0.25 to 0.75 wt. %.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003ePrevious studies have reported that a significant decrease in C\u0026ndash;H peak intensities is linked to the formation of strong hydrogen bonds during polymer blending (Panickar \u0026amp; Rangari, 2024; Zhang et al., 2020). The \u0026ndash;CH groups likely act as hydrogen donors, chemically bonding with the terminal hydroxyl groups in AH/HAp, which leads to the notable reduction in \u0026ndash;CH intensities observed in the polymer composite. Additionally, this decrease in intensity has been attributed to the grafting of the filler onto the PLA matrix (Qin et al., 2017). FTIR analysis of the composite films confirms the presence of chemical bonding between n-HAp and the PLA matrix.\u003c/p\u003e\u003cp\u003eFurthermore, Raman spectroscopy was used to characterize the PLA_HAp films and investigate possible chemical interactions between the PLA matrix and n-HAp (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e(c)). The Raman spectrum of neat PLA showed characteristic peaks at 876, 1460, 1768, and 2848\u0026ndash;3047 cm⁻\u0026sup1;, corresponding to the \u0026ndash;C\u0026ndash;COO, \u0026ndash;CH, \u0026ndash;C\u0026thinsp;=\u0026thinsp;O, and \u0026ndash;CH vibrational groups, respectively. When comparing the Raman spectra of neat PLA and PLA_HAp composite films, no significant peak shifts or changes were detected. However, a small additional peak at 676 cm⁻\u0026sup1; (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e(d)) appeared in all PLA_HAp samples, attributed to the symmetric P\u0026ndash;O\u0026ndash;P stretching vibration of n-HAp (Andrade et al., 1999). This P\u0026ndash;O\u0026ndash;P vibration peak further confirms the chemical interaction between n-HAp and the PLA backbone. Such interaction likely contributes to the notable enhancement in the thermal and mechanical properties observed in the PLA_HAp composite blown films.\u003cb\u003e3.3 Thermal Characterization of PLA_HAp Blown Films\u003c/b\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThermal property analysis of the PLA_HAp composite, in comparison to neat PLA blown films, was conducted using TGA and DSC. Figure\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e (a \u0026amp; b) presents the thermal degradation curves and DTG curves obtained for the PLA_HAp composite films (0.25, 0.5, 0.75, and 1 wt.% n-HAp in PLA) as well as for neat PLA films. The thermal degradation values gathered from the thermograms are summarized in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. The initial degradation temperature of the PLA_HAp composite films increased significantly by 15\u0026deg;C for 0.25 wt.% of n-HAp when compared to neat PLA and subsequently decreased by 9\u0026deg;C, 5\u0026deg;C, and \u0026minus;\u0026thinsp;7\u0026deg;C with increasing wt.% of 0.5, 0.75, and 1, respectively. This study reveals that a notably low concentration of n-HAp in PLA has enhanced the thermal stability of the PLA_HAp composite compared to neat PLA (\u0026le;\u0026thinsp;0.75 wt.%). However, higher concentrations of HAp reduced the thermal stability of the polymer composite.\u003c/p\u003e\u003cp\u003eIt is noted that the thermal stability of the composites is influenced by the interfacial bonding within the composite. Akinodoyo et al. have reported that the electrostatic attraction of the Ca2\u0026thinsp;+\u0026thinsp;ions in n-HAp and the -COO- functional groups can significantly affect the interfacial attraction in the polymer composite. The observed decrease in the thermal stability of the PLA_HAp composite in this study, with increasing filler concentration, can be attributed to the electrostatic interaction between the n-HAp and PLA.\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\u003eTGA analysis Summary of PLA_HAp composite blown films\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=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSamples\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eInitial degradation Temp (\u003csup\u003eo\u003c/sup\u003e C)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eFinal degradation Temp (\u003csup\u003eo\u003c/sup\u003e C)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eDeriv Weight %\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eNeat PLA\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e344.11\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e371.64\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e382.96\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePLA_HAp 0.25\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e359.11\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e396.42\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e384.30\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePLA_HAp 0.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e352.65\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e380.66\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e371.31\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePLA_HAp 0.75\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e348.80\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e392.85\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e379.62\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePLA_HAp 1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e337.35\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e374.91\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e363.01\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\u003eDSC thermograms of heating and cooling cycles of the PLA_HAp blown film samples were analyzed to understand the effect of n-HAp on the thermal properties of the PLA composite. Figure\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e(c\u0026amp;d) shows the heating and cooling DSC thermograms, respectively, of the PLA_HAp composite films. Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e summarizes the DSC heating curves obtained for neat PLA and PLA_HAp composite films. Thermal properties including glass transition temperature (Tg), melting temperature (Tm), and crystallinity (χ) were derived from the DSC thermograms. It was observed that the Tg of the PLA_HAp composite film samples decreased significantly compared to neat PLA films. The reduction in Tg is attributed to increased mobility in the polymer chains caused by the incorporation of n-HAp into the PLA matrix (Maiza et al., 2015). The crystallinity (χ) behavior of the PLA_HAp composite samples was calculated using Eq.\u0026nbsp;(2) with data from the first heating cycle thermogram.\u003c/p\u003e\u003cp\u003eχ \u003csub\u003e=\u003c/sub\u003e \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\frac{{\\varDelta\\:H}_{m}-{\\varDelta\\:H}_{C}}{{\\varDelta\\:H}_{m}^{o}}\\)\u003c/span\u003e\u003c/span\u003e \u003csub\u003e(2)\u003c/sub\u003e\u003c/p\u003e\u003cp\u003eWhere ΔHm is the melting enthalpy of the samples (J/g), ΔHc is the crystallization enthalpy, and ΔH\u003csup\u003eo\u003c/sup\u003e\u003csub\u003em\u003c/sub\u003e is the melting enthalpy of fully crystalline PLA, valued at 93.7 J/g. The crystallinity values calculated for the PLA films using Eq.\u0026nbsp;(2) indicate that the presence of n-HAp reduces the crystallinity of the PLA composite films. This decrease is attributed to the small amount of n-HAp in the PLA matrix, which introduces more amorphous regions, thereby reducing polymer chain orientation and limiting their mobility. This leads to an increased degree of disorder within the PLA matrix (Akindoyo et al., 2018; Nedaipour et al., 2020). It has also been reported that reduced crystallinity may accelerate PLA degradation (Pantani \u0026amp; Sorrentino, 2013). A slight shift in the melting temperature of the PLA_HAp composite films was also observed, likely due to less stable crystal sizes within the polymer matrix (Pandele et al., 2020).\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\u003eDSC analysis summary of PLA_HAp composite blown films\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"7\"\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=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSamples\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eGlass Transition Temp\u003c/p\u003e\u003cp\u003eT \u003csub\u003eg\u003c/sub\u003e (\u003csup\u003eo\u003c/sup\u003e C)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eCrystallization Temp T\u003csub\u003eCC\u003c/sub\u003e (\u003csup\u003eo\u003c/sup\u003e C)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eCrystallization enthalpy\u003c/p\u003e\u003cp\u003eΔH \u003csub\u003ec\u003c/sub\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eMelting Temp T\u003csub\u003em\u003c/sub\u003e\u003c/p\u003e\u003cp\u003e(\u003csup\u003eo\u003c/sup\u003e C)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003eMelting enthalpy\u003c/p\u003e\u003cp\u003eΔH \u003csub\u003em\u003c/sub\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c7\"\u003e\u003cp\u003eCrystallinity %χ\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eNeat PLA\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e58.65\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e88.29\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e16.41\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e170.15\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e36.35\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e21.28\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePLA_HAp 0.25\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e49.80\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e94.85\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e20.33\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e171.51\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e36.05\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e16.77\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePLA_HAp 0.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e50.55\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e93.95\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e19.81\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e171.37\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e36.54\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e17.85\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePLA_HAp 0.75\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e53.31\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e92.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e18.36\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e168.38\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e36.34\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e19.18\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePLA_HAp_1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e49.60\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e94.16\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e19.10\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e168.25\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e35.88\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e17.93\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=\"Sec13\" class=\"Section2\"\u003e\u003ch2\u003e3.4 Mechanical Characterization of PLA_HAp Blown Films\u003c/h2\u003e\u003cp\u003eThe mechanical properties of the PLA composite blown films were compared with neat PLA films. Figure\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e (a) shows the stress vs strain curves obtained for the PLA blown film samples that highlight the influence of n-HAp in the PLA matrix. The steep slope of the neat PLA exhibits the high stiffness of the polymer. The reinforcement of the n-HAp at varying wt.% in PLA significantly changed the mechanical properties of the PLA films. Mechanical property analysis of hydroxyapatite in PLA at a relatively lower concentration of less than 1% has not been reported yet. However, hydroxyapatite at relatively high concentrations varying from 1\u0026ndash;50% has been reported previously [\u003cspan additionalcitationids=\"CR24\" citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]. These studies reported that higher concentrations of hydroxyapatite exhibited improved tensile strength and then deteriorated at relatively higher concentrations. The Strain vs Stress curves of the PLA_HAp blown films loaded with 0.25 wt.%, 0.5 wt.%, 0.75 wt.%, and 1 wt.% exhibited reduced tensile strength compared to neat PLA films. This result can be related to the reduced crystallinity values determined from DSC thermograms in the present study. It has been reported that reduced crystallinity can reduce the tensile strength and stiffness of PLA, making it more flexible and softer. Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e. Summarized the average values of Young\u0026rsquo;s modulus, tensile strength, and elongation at break obtained for neat PLA and PLA_HAp composite samples. All PLA_HAp composite samples displayed reduced Young's modulus compared to neat PLA. It can be deduced that the reduced Young's modulus is due to the weak interfacial interaction between n-HAp and the polymer [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. Among various wt.% of n-HAp in PLA, PLA_HAp 0.75 exhibited the maximum flexibility and elongation at break. The elongation at the break of PLA_HAp 0.75 showed an enhancement of 368% from the neat PLA film. As the wt.% further increased to 1% the tensile strength increased, and elongation at break was reduced for PLA_HAp 1 blown film. Mechanical property analysis of the PLA_HAp composite films shows that relatively low concentrations of n-HAp (0.5% and 0.75%) can significantly reduce the tensile strength and improve the elongation at the break of PLA polymer.\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\u003eSummary of Tensile test data of PLA_HAp Blown Films\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=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSample\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eYoungs Modulus\u003c/p\u003e\u003cp\u003eMPa\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eTensile, F\u003csub\u003emax\u003c/sub\u003e\u003c/p\u003e\u003cp\u003eMPa\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\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\u003eNeat PLA\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e2286.02\u0026thinsp;\u0026plusmn;\u0026thinsp;18.30\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e\u003cp\u003e62.56\u0026thinsp;\u0026plusmn;\u0026thinsp;8.43\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e\u003cp\u003e7.41\u0026thinsp;\u0026plusmn;\u0026thinsp;2.59\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePLA_HAp 0.25\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e846.6\u0026thinsp;\u0026plusmn;\u0026thinsp;14.20\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e\u003cp\u003e53.88\u0026thinsp;\u0026plusmn;\u0026thinsp;3.43\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e\u003cp\u003e12.60\u0026thinsp;\u0026plusmn;\u0026thinsp;3.46\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePLA_HAp 0.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e858.75\u0026thinsp;\u0026plusmn;\u0026thinsp;11.16\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e\u003cp\u003e29.19\u0026thinsp;\u0026plusmn;\u0026thinsp;2.16\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e\u003cp\u003e28.69\u0026thinsp;\u0026plusmn;\u0026thinsp;2.69\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePLA_HAp 0.75\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e987.91\u0026thinsp;\u0026plusmn;\u0026thinsp;13.34\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e\u003cp\u003e32.27\u0026thinsp;\u0026plusmn;\u0026thinsp;2.72\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e\u003cp\u003e34.67\u0026thinsp;\u0026plusmn;\u0026thinsp;2.13\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePLA_HAp 1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e802.4\u0026thinsp;\u0026plusmn;\u0026thinsp;15.37\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e\u003cp\u003e42.07\u0026thinsp;\u0026plusmn;\u0026thinsp;2.31\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e\u003cp\u003e14.06\u0026thinsp;\u0026plusmn;\u0026thinsp;3.15\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\u003cp\u003eThe fracture analysis of the blown films after the tensile testing was performed to understand the mode of fracture and the mechanism behind the failure. The fractography of neat PLA and PLA_HAp 0.75% blown films are given in Figs.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e (b) and (c), respectively. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e (b), the neat PLA film exhibited fracture surface with minimal ruptures and less plastic deformations, which is identified as a brittle fracture. The PLA_HAp 0.75 wt% (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e (c)) exhibited multiple micro-cracks and ruptures all over the fractured surface possibly due to the plastic deformation that took place during tensile testing. The fracture analysis infers that the n-HAp has significantly improved the flexibility of the composite blown film that can deform readily under stress and the elongation at break obtained for PLA_HAp 0.75 was 34.8%. It has been reported that the fillers reinforced in the PLA matrix can help to evenly distribute the stress, permitting greater deformation before failure [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e, \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e].\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec14\" class=\"Section2\"\u003e\u003ch2\u003e3.5 Soil Biodegradability Studies of PLA_HAp Blown Films\u003c/h2\u003e\u003cp\u003eThe soil degradation study of the neat PLA and n-HAp reinforced PLA blown film samples was studied to investigate the effect of n-HAp filler in accelerating the biodegradation property of PLA composite. Figure\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e (a) shows the labeled plastic pots with blown film samples buried in them for biodegradation studies in the greenhouse. Six samples each from neat PLA, PLA_HAP 0.5, and PLA_HAp 1 with labels R1, R2, R3, R4, R5, and R6 were buried in the soil for the soil degradation studies. The first set of three samples R1, R2, and R3 were picked out after 90 days and the second set of samples R4, R5, and R6 were picked out after 180 days from the soil. Each blown film sample picked out from the soil was cleaned, washed with distilled water, and dried before it was measured for mass loss. The degradation kinetics was determined by calculating the mass loss that occurred in the blown film samples while in the soil. The mass loss (ML) was calculated using the Eq.\u0026nbsp;(2).[\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e]\u003c/p\u003e\u003cp\u003eML= \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\frac{{\\text{m}}_{\\text{o}}-{\\text{m}}_{\\text{t}}}{{\\text{m}}_{\\text{o}}}\\text{X}100\\)\u003c/span\u003e\u003c/span\u003e (2)\u003c/p\u003e\u003cp\u003eWhere m\u003csub\u003eo\u003c/sub\u003e is the initial mass of the sample and m\u003csub\u003et\u003c/sub\u003e denotes the sample mass after the degradation time. The average mass loss calculated from Eq.\u0026nbsp;(2) for neat PLA, PLA_HAP 0.5, and PLA_HAP 1 samples is given in Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e (b). The ML analysis of the samples reveals that neat PLA films exhibited significantly low degradation of 0.6% after 180 days. Whereas PLA_HAp 0.5 exhibited an average ML of 1.2% and 3.6% for samples taken out at 90 days and 180 days, respectively. PLA_HAP 1 exhibited an average ML of 1.2% and 2% for samples taken out at 90 days and 180 days, respectively. The soil biodegradation studies of the neat PLA and PLA_HAp 0.5 reveal that the effect of HAp has significantly enhanced the degradation of the composite film by 500% after 180 days compared with neat PLA. These results show that the presence of n-HAp in the PLA matrix has significantly improved the biodegradation property of the PLA_HAp composite films.\u003c/p\u003e\u003cp\u003eHydrolysis is one of the key factors in polymer degradation, initiating a chemical reaction between water molecules and polymer bonds that effectively breaks the polymer chains into fragments. PLA is a biobased polymer that is not easily degradable at ambient temperature, which significantly reduces the hydrolysis rate. In the present work, hydroxyapatite, being a hydrophilic material, has significantly enhanced the hydrolysis rate in the polymer composite, leading to the breakdown of ester molecules. Although the PLA_HAp 1 film shows an increase in the ML over time, the ML is reduced compared to PLA_HAp 0.5, possibly because the higher concentration of HAp in the PLA composite made the films more hydrophilic, which hindered the bulk erosion of the films. Gazvoda et al. have reported that during soil degradation in hydrophilic films, degradation occurs on the surface, initiating surface erosion. It has also been reported that hydrophilicity can significantly reduce the enzymatic degradation of the polymer, as excess water molecules can restrict the enzyme\u0026rsquo;s access to the bulk, resulting in only surface erosion occurring [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e, \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e]. Figure\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e (c) shows the photographs of the blown film samples of neat PLA, PLA_HAp 0.5, and PLA_HAp compared with before and after soil degradation analysis. A significant change in the film transparency was observed for the PLA_HAp 0.5 and PLA_HAp 1 blown film samples taken out from the soil at 90 and 180 days, respectively. Compared to the neat PLA films the PLA_HAP 0.5, and PLA_HAp 1 samples changed to a milky white color as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e (c) after 90 and 180 days. Siakeng et al.[\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e] have illustrated the color changes in biocomposite samples with exposure time.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe significant reduction in the transparency of the PLA_HAp 0.5 and PLA_HAp 1 confirms the accelerated hydrolysis rate that occurred in the biocomposite samples that resulting in mass loss with time.\u003c/p\u003e\u003cdiv id=\"Sec15\" class=\"Section3\"\u003e\u003ch2\u003e3.5.1 FTIR analysis\u003c/h2\u003e\u003cp\u003eOne sample each from neat PLA, PLA_HAP 0.5, and PLA_HAp with the highest mass loss was further characterized for biodegradation studies. Figure\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e (a\u0026amp; b) shows the FTIR spectrum obtained for neat PLA_R2, PLA_HAp 0.5_R2, and PLA_HAp 1_R1 samples and Neat PLA_R5, PLA_HAp 0.5_R4, and PLA_HAp 1_R4 samples from 90 days and 180 days of soil degradation, respectively. FTIR spectrum of the blown film samples from soil was obtained to understand any change in chemical bonding that occurs during the biodegradation in soil. The FTIR spectrum reveals significant changes in the intensities of the functional groups after soil degradation. An increase in the intensity at 1384 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, 1460 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, and 1768 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e was observed for neat PLA_R2, PLA_HAp 0.5_R2, and PLA_HAp 1_R1 samples taken out at 90 days. The increase in intensity at 1384 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, and 1460 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e shows the PLA degradation attributed to the C-H deformational peak of the CH\u003csub\u003e3\u003c/sub\u003e group of PLA[\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e]. The increase in the intensity at 1768 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e is attributed to the hydrolytic degradation of PLA due to the increase in carboxylic groups in the PLA matrix [\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e] However, the neat PLA degradation was significantly low compared to the PLA composite films from the ML calculation possibly because of the rigid long chain and the presence of methyl group that makes it more hydrophobic, thus restricting hydrolysis.[\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e] The significantly low intensities of neat PLA around 2995\u0026thinsp;\u0026minus;\u0026thinsp;2850 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e peaks attributed to the -CH\u003csub\u003e3\u003c/sub\u003e stretching of the alkyl chains infers a low degradation rate in soil. Figure\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e (b) shows broad low intensity peaks at 2337\u0026ndash;2358 cm \u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e in the film samples taken out at 180 days attributed to C\u0026thinsp;=\u0026thinsp;N functional groups because of the long term soil exposure[\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e]. PLA_HAp 0.5_R2 and PLA_HAp 0.5_R4 exhibited significantly high intensity around 2995\u0026thinsp;\u0026minus;\u0026thinsp;2850 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e peaks attributed to the -CH\u003csub\u003e3\u003c/sub\u003e stretching of the alkyl chains infers a high degradation rate in soil relevant to ML measurement.[\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e]The FTIR spectrum showed significantly high intensity for C-O, C\u0026thinsp;=\u0026thinsp;O and C-H bonds for PLA_HAp composite samples compared to neat PLA. Zamir et al [\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e]. have also reported a similar trend in increased intensity for PLA/g-SNCs compared to neat PLA. The FTIR analysis confirms that the n-HAp in PLA has significantly improved the hydrolysis reaction and initiated microbial activity in the composite films resulting in better degradation in PLA_HAp film samples in soil.\u003c/p\u003e\u003cp\u003e\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\u003eTGA analysis: Summary of PLA_HAp composite blown films after soil degradation analysis.\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=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSamples\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eInitial degradation Temp (\u003csup\u003eo\u003c/sup\u003eC)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eFinal degradation Temp (\u003csup\u003eo\u003c/sup\u003eC)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eDeriv Weight %\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eNeat PLA_R2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e342.34\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e378.68\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e368.57\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eNeat PLA_R5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e353.08\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e387.10\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e376.50\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePLA_HAp 0.5_R2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e341.02\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e381.75\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e368.39\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePLA_HAp 0.5_R4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e318.29\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e351.77\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e343.27\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePLA_HAp 1_R1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e330.29\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e347.05\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e339.86\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePLA_HAp 1_R4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e328.95\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e365.44\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e351.95\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=\"Sec16\" class=\"Section3\"\u003e\u003ch2\u003e3.5.2 Thermogravimetric Analysis\u003c/h2\u003e\u003cp\u003eThe thermal stability of the soil buried film samples was investigated using thermogravimetric analysis. Figure\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e (c) shows the TGA curves obtained for the soil buried samples of neat PLA, PLA_HAp 0.5, and PLA_HAp 1 samples taken out from the soil at 90 days and 180 days, respectively. The summary of the TGA thermograms obtained for the soil buried samples is given in Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e. The initial degradation temperatures (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e) obtained for neat PLA, PLA_HAp 0.5, and PLA_HAp 1 before soil degradation were 344.11 \u003csup\u003eo\u003c/sup\u003eC, 352.65 \u003csup\u003eo\u003c/sup\u003eC, and 337.35 \u003csup\u003eo\u003c/sup\u003eC, respectively. whereas the initial degradation temperature obtained for neat PLA, PLA_HAp 0.5, and PLA_HAp 1 exhibited a significant reduction in the initial degradation temperature after 90 and 180 days. It was observed that the PLA_HAp 0.5 and PLA_HAp 1 film samples (after 90 and 180 days) experienced weight loss at approximately 100\u0026deg;C. This was attributed to the enhanced hydrophilicity caused by n-HAp as a filler, which promoted soil degradation. PLA_HAp 0.5_R4 reveals the lowest thermal stability with an initial degradation temperature of 318.29 \u003csup\u003eo\u003c/sup\u003eC with maximum soil degradation after 180 days. TGA thermograms obtained for the soil buried samples showed good agreement with the ML calculations of the samples. The thermal degradation of the samples again confirms the deterioration of the samples by microbial and enzymatic degradation.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec17\" class=\"Section3\"\u003e\u003ch2\u003e3.5.3 Morphology Changes\u003c/h2\u003e\u003cp\u003eThe morphology of the PLA composite films was analyzed using SEM imaging before and after 90 and 180 days of soil degradation. Figure\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e (a-c) shows the SEM image of neat PLA, PLA_HAp 0.5, and PLA_HAp 1 film samples before the soil burial test with smooth surfaces and flow lines in the direction of extrusion. Figure\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e (d-f) shows the SEM image of neat PLA_R2, PLA_HAp 0.5_R2, and PLA_HAp 1_R1 film samples after 90 days of soil biodegradation. Figure\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e (g-i) shows the SEM image of neat PLA_R5, PLA_HAp 0.5_R4, and PLA_HAp 1_R4 film samples after 180 days of soil biodegradation. A significant surface deterioration was observed in the soil buried samples that progressed with burial time. The Neat PLA films exhibited increased roughness and tiny protrusions on the surface with burial time, which indicates the starting of deterioration [\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e]. In the case of PLA_HAp 0.5 and PLA_HAp 1 film samples, microcracks and fibrillations were visible on the sample with burial time. It was understood that the fibrillations and increased roughness on the surface of the PLA composite samples are attributed to the presence of n-HAp. SEM Image analysis of the soil buried film samples reveals the accelerated surface deterioration due to microbial etching.\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e"},{"header":"CONCLUSIONS","content":"\u003cp\u003eThis study demonstrates that incorporating small amounts of nano-hydroxyapatite (n-HAp) into a PLA matrix significantly enhances the thermal, mechanical, and biodegradable properties of the composite samples compared to neat PLA. A simple and feasible alkaline hydrolysis method was employed to extract n-HAp from pink perch fish scales. XRD analysis confirmed that the isolated powder is hydroxyapatite with a particle size of approximately 11\u0026ndash;12 nm. Various concentrations of n-HAp (0.25 wt.%, 0.5 wt.%, 0.75 wt.%, and 1 wt.%) were incorporated into the PLA matrix using solution blending followed by blown film extrusion. The thermal, mechanical, and biodegradable properties of these composites were systematically analyzed. Thermal analysis via TGA and DSC revealed that even low concentrations of n-HAp significantly influence the initial degradation temperature, glass transition temperature, and crystallinity of the composite films. Tensile testing indicated that PLA_HAp 0.75 exhibited reduced tensile strength but enhanced elongation at break. A 180-day biodegradation study in soil demonstrated that the presence of n-HAp accelerates the hydrolysis process, improving the soil degradation rate of the composite films by 500% compared to neat PLA. Overall, this study highlights the effectiveness of n-HAp in enhancing the functional properties of PLA-based composites.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eCRediT authorship contribution statementRadhika Panickar: Writing -original draft, Data Curation, Methodology,Investigation. Devotha Mwazembe: Polymer degradation and soil testing,Benny Alexander, Reviewing, barrier testing, Edwin Freeman: Writing \u0026ndash; re-view \u0026amp; editing, Validation. Desmond Mortley: Soil testing and methodology,Vijaya Rangari: Writing \u0026ndash; review \u0026amp; editing, Methodology, Validation. Supervision, Resources\u003c/p\u003e\u003ch2\u003eAcknowledgement\u003c/h2\u003e\u003cp\u003eThe authors would like to acknowledge financial support from MARS Wrigley, Global Innovation Center, Chicago, IL., NSF-NRT# 2125606, NSF-CREST #1735971, and NSF-DMR# 2117242\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003eData will be provided up on request\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eAtiwesh G, Mikhael A, Parrish CC, et al (2021) Environmental impact of bioplastic use: A review. Heliyon 7:e07918. https://doi.org/https://doi.org/10.1016/j.heliyon.2021.e07918\u003c/li\u003e\n\u003cli\u003eMutmainna I, Gareso PL, Suryani S, Tahir D (2024) Microplastics from petroleum-based plastics and their effects: A systematic literature review and science mapping of global bioplastics production. 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Express Polym Lett 4:423\u0026ndash;430. https://doi.org/10.3144/expresspolymlett.2010.53\u003c/li\u003e\n\u003cli\u003eMakadia HK, Siegel SJ (2011) Poly Lactic-co-Glycolic Acid (PLGA) as Biodegradable Controlled Drug Delivery Carrier. Polymers (Basel) 3:1377\u0026ndash;1397. https://doi.org/10.3390/polym3031377\u003c/li\u003e\n\u003cli\u003ePlohl O, Erjavec A, Fras Zemljič L, et al (2023) Morphological, surface and thermal properties of polylactic acid foils, melamine-etherified resin, and polyethylene terephthalate fabric during (bio)degradation in soil. J Clean Prod 421:. https://doi.org/10.1016/j.jclepro.2023.138554\u003c/li\u003e\n\u003cli\u003eLv S, Liu X, Gu J, et al (2017) Microstructure analysis of polylactic acid-based composites during degradation in soil. Int Biodeterior Biodegradation 122:53\u0026ndash;60. https://doi.org/https://doi.org/10.1016/j.ibiod.2017.04.017\u003c/li\u003e\n\u003cli\u003eSharafi Zamir S, Fathi B, Ajji A, et al (2022) Biodegradation of modified starch/poly lactic acid nanocomposite in soil. Polym Degrad Stab 199:109902. https://doi.org/https://doi.org/10.1016/j.polymdegradstab.2022.109902\u003c/li\u003e\n\u003cli\u003eSharma S, Majumdar A, Butola B (2021) Tailoring the biodegradability of polylactic acid (PLA) based films and ramie- PLA green composites by using selective additives. Int J Biol Macromol 181:. https://doi.org/10.1016/j.ijbiomac.2021.04.108\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"journal-of-polymers-and-the-environment","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"jooe","sideBox":"Learn more about [Journal of Polymers and the Environment](https://www.springer.com/journal/10924)","snPcode":"10924","submissionUrl":"https://submission.nature.com/new-submission/10924/3","title":"Journal of Polymers and the Environment","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Polymer composite, Alkaline hydrolysis, Polylactic Acid, Hydroxyapatite, Blown Films, Biodegradable composite","lastPublishedDoi":"10.21203/rs.3.rs-7216042/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7216042/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eIn this study, nano-hydroxyapatite (n-HAp) was extracted from pink perch fish scales (PPFS) using a simple and efficient alkaline hydrolysis method. The obtained n-HAp was characterized through XRD, FTIR, Raman spectroscopy, TGA, SEM, and TEM. Various concentrations of n-HAp (0.25, 0.5, 0.75, and 1 wt.%) were then incorporated into a polylactic acid (PLA) matrix using solution blending followed by blown film extrusion. The influence of n-HAp on the thermal, mechanical, and biodegradable properties of the PLA-based composites was systematically analyzed. FTIR and Raman spectroscopy confirmed chemical bonding between n-HAp and the PLA matrix in the blown films. Thermal analysis via TGA revealed an increase in the initial degradation temperature compared to neat PLA, attributed to the presence of n-HAp. DSC analysis showed a reduction in glass transition temperature and crystallinity, which restricted polymer chain mobility and increased the amorphous phase. Mechanical property evaluation through tensile testing demonstrated that lower concentrations of n-HAp significantly enhanced elongation at break, with PLA_HAp 0.75 exhibiting improved flexibility and increase in elongation compared to neat PLA. A 180-day soil biodegradability study indicated that incorporating 0.5 wt.% n-HAp into the PLA matrix accelerated the hydrolysis process by 500%, enhancing the overall degradation of the PLA_HAp composite film. These findings highlight the potential of n-HAp in improving the functional properties of PLA-based composites for food packaging applications.\u003c/p\u003e","manuscriptTitle":"Investigations on Thermomechanical and Biodegradable Properties of Alkaline Hydrolysis Isolated Nano Hydroxyapatite Reinforced Polylactic Acid Composite Blown Films for sustainable Packaging","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-08-04 10:02:10","doi":"10.21203/rs.3.rs-7216042/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-08-29T15:06:51+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-08-09T10:36:45+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-08-04T07:15:25+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"235890264418597994473423313199747726533","date":"2025-08-01T21:48:10+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"102417879826980271687230129791592223838","date":"2025-08-01T08:55:47+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-07-31T09:52:42+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-07-30T10:50:14+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"202037567854617308301223239000713311964","date":"2025-07-30T10:27:53+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"5401046351410239670943270525721891557","date":"2025-07-30T05:49:19+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"82915910659256802645046309346894140087","date":"2025-07-30T04:49:29+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-07-29T20:10:39+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-07-26T14:19:44+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-07-26T14:18:22+00:00","index":"","fulltext":""},{"type":"submitted","content":"Journal of Polymers and the Environment","date":"2025-07-25T16:14:10+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"journal-of-polymers-and-the-environment","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"jooe","sideBox":"Learn more about [Journal of Polymers and the Environment](https://www.springer.com/journal/10924)","snPcode":"10924","submissionUrl":"https://submission.nature.com/new-submission/10924/3","title":"Journal of Polymers and the Environment","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"efc84bb1-9c5e-4590-adb0-499c80f25dce","owner":[],"postedDate":"August 4th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2026-02-23T16:01:18+00:00","versionOfRecord":{"articleIdentity":"rs-7216042","link":"https://doi.org/10.1007/s10924-025-03737-8","journal":{"identity":"journal-of-polymers-and-the-environment","isVorOnly":false,"title":"Journal of Polymers and the Environment"},"publishedOn":"2026-02-20 15:57:49","publishedOnDateReadable":"February 20th, 2026"},"versionCreatedAt":"2025-08-04 10:02:10","video":"","vorDoi":"10.1007/s10924-025-03737-8","vorDoiUrl":"https://doi.org/10.1007/s10924-025-03737-8","workflowStages":[]},"version":"v1","identity":"rs-7216042","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7216042","identity":"rs-7216042","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}