Core-Shell Structure Acrylonitrile-Styrene-Acrylate Particles with Different Acrylonitrile Contents Improved Toughness of Poly(styrene-co-acrylonitrile) Resins

Core-Shell Structure Acrylonitrile-Styrene-Acrylate Particles with Different Acrylonitrile Contents Improved Toughness of Poly(styrene-co-acrylonitrile) Resins | 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 Core-Shell Structure Acrylonitrile-Styrene-Acrylate Particles with Different Acrylonitrile Contents Improved Toughness of Poly(styrene-co-acrylonitrile) Resins Mengen Liu, Qianyi Tang, Bai-jun Liu, Ming-yao ZHANG This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-3250207/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Herein, core-shell structured grafted copolymer particles of poly(butyl acrylate) grafted polystyrene acrylonitrile (ASA) with different contents of acrylonitrile (AN) were prepared by emulsion graft polymerization. ASA resins were then obtained by melt blending of ASA graft copolymers with SAN (w/w, AN/St, 25/75) resins. This paper investigates the effect of acrylonitrile content in ASA graft copolymers on the mechanical properties of ASA resins. The particle size distribution, composition of ASA, cross-section morphology, and compatibility of the material were characterized by dynamic light scattering (DLS), nuclear magnetic resonance (NMR), scanning electron microscopy (SEM), and dynamic mechanical analysis (DMA). The results revealed the highest notched impact strength of ASA resin reaching up to 277.49 J/m at AN content of grafted SAN of 21%, equivalent to an 80% increase when compared to 25% AN content. The lap shear adhesion tests revealed excellent interfacial adhesion between the ASA particles and SAN matrix owing to the difference in AN. This significantly enhanced the toughness of the ASA resin. Additionally, the ASA particles displayed the widest particle size distribution. The synergistic toughening of small and large rubber particles also enhanced the impact resistance of ASA resin to a certain extent. Therefore, the excellent interfacial adhesion between ASA graft copolymer and SAN matrix and the synergistic toughening of large rubber particles together promote the toughness of ASA resin. Acrylonitrile-Styrene-Acrylate Core-shell structure Interfacial adhesion Synergistic toughening Particle size distribution Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 1. Introduction Toughening of polymer materials has been widely researched and rapidly developed in recent decades due to its unparalleled importance in business, such as strengthening and toughening of polymer materials such as epoxy resins, poly cross esters, and polypropylene [ 1 – 5 ] . To improve the impact toughness of polymer materials for practical applications, several new techniques have been developed. For example, the most widely used application in toughening polymer materials is the development of a two-phase structure that uses rubber as the dispersed phase to improve the brittle fracture characteristics of polymers [ 6 ] . The presence of rubber particles as the dispersed phase concentrate and cavitate under load may cause silvering or shear yielding of the matrix around it, thereby resulting in toughened polymer materials [ 7 – 10 ] Rubber toughening of polymer materials depends on several factors, such as the interfacial adhesion between the rubber phase and polymer matrix, the degree of dispersion of the rubber, and the inherent ductility of the matrix [ 11 , 12 ] . Polystyrene acrylonitrile (SAN) random copolymer is a typical glassy thermoplastic polymer characterized by brittle fracture which severely limits its application. Therefore, modification of SAN resins has extensively been explored to improve its brittle fracture. For example, Xu et al. toughened SAN resins using PBL-g-SAN, PBA-g-SAN, and high-rubber EPDM-SAN impact modifiers [ 13 – 15 ] . Their results revealed the formation of PBA-g-SAN impact-modified particles consisting of a core made of crosslinked PBA rubber particles and a shell composed of grafted SAN. In this fashion, the SAN microzone transition layer showed good compatibility with the SAN matrix, ensuring better dispersion of the rubber particles in the matrix of SAN resin [ 16 – 17 ] . In another study, PBA-g-SAN impact modifier and SAN resin were prepared by melt blending to obtain ASA resin with mechanical properties comparable to those of ABS resin coupled with excellent weather resistance, coloring, and chemical corrosion resistance [ 18 ] . Therefore, ASA resin is widely used in automotive, electrical and electronic, gardening, and other fields. The factors affecting toughened polymers, such as rubber phase size and distribution, grafting rate, and core-shell morphology have widely been investigated [ 19 ] . For instance, Huang investigated the impact of PBA seeds on the feeding mode of monomers ratio on the growth of nucleated particles [ 20 ] . Tolue explored the effect of the type of surfactant, as well as the mode of incorporation of second-stage monomers on the final morphologies of latex particles [ 21 ] . Choi studied the influence of the grafting rate on the tensile properties of high-impact polystyrene (HIPS) [ 22 ] . In addition, the composition of core-shell particles may also influence the mechanical properties of the blends. For instance, Kumaraswamy et al. recorded that the miscibility and phase separation in SAN/PMMA blends investigated by positron lifetime measurements [ 23 ] . So far, numerous studies have been conducted on the toughening of SAN resins by ASA core-shell graft copolymers. However, no in-depth studies have been conducted on the mechanism of toughening of SAN resins by the composition of its shell monomer. Herein, emulsion polymerization was used to prepare modified particles of poly(butyl acrylate, PBA) as the rubber core and poly(styrene-acrylonitrile) (SAN) as the glassy polymer shell. During the polymerization process, the PBA rubber particles were slightly crosslinked to ensure the construction of the core-shell structure during grafting, as well as provide a better toughening effect [ 24 – 27 ] The unreacted double bonds during the crosslinking process of the PBA rubber particles provided grafting sites for the grafted SAN resins. Similarly, the unreacted double bonds during crosslinking of PBA rubber particles provided grafting sites for subsequent grafting. The grafted SANs also provided good interfacial adhesion between the rubber particles and the matrix. The effect of acrylonitrile content in ASA graft copolymers on the toughness of ASA resins was investigated by focusing on the synergistic toughening of ASA graft copolymers and SAN substrates with large and small rubber particles, it was found that the toughness of ASA resin jumped to the maximum value at 21% acrylonitrile content of grafted SAN. 2. Experimental 2.1 Materials Butyl acrylate (BA) was purchased from Shanghai Titan Technology Co. Sodium dodecyl sulfate (SDS), potassium carbonate (K 2 CO 3 ), and potassium persulfate (KPS) were all received from Tianjin Fuchen Chemical Reagent Co. Ethylene glycol dimethacrylate (EDGMA) was obtained from Shanghai Aladdin Biochemical Technology Co. SAN (Jihua 2437, St/AN, 75/25, w/w), styrene (St), acrylonitrile (AN), and tertiary dodecyl mercaptan (TDDM) were provided by Jilin Chemical Co. Acetone was purchased from Chengdu Cologne Chemical Co. 2.2 Synthesis of ASA Latex The ASA core-shell latexes were prepared by a two-stage emulsion polymerization method. The reaction takes place in a three-necked flask, water bath heating, condensation reflux, and mechanical stirring. The reaction system was synthesized at 65°C for 2h and 85°C for 1h to synthesize large particle-size PBA latex. The formulations are summarized in Table 1 . St and AN monomers were grafted onto PBA cores under the same conditions at a fixed total mass of the monomers and varied AN content during the dropwise monomer pre-emulsion to 21%-29% to yield ASA core-shell latexes with different AN acrylonitrile contents (Table 2 ). Note that all monomer pre-emulsions were fully pre-emulsified at room temperature. Table 1 Preparation conditions of PBA latexes. Reagent Quality (g) BA 100 EDGMA 2 DDI 67 Na 2 CO 3 0.9 SDS 1 KPS 0.4 Table 2 Preparation conditions of ASA latexes (g). Reagent A 21 A 23 A 25 A 27 A 29 Core phase latex 200 200 200 200 200 DDI 199 199 199 199 199 AN 16.8 18.4 20 21.6 23.2 St 63.2 61.6 60 58.4 56.8 SDS 0.2 0.2 0.2 0.2 0.2 KPS 0.32 0.32 0.32 0.32 0.32 A 21 : AN content of the grafted SAN corresponds to 21%. 2.3 Preparation of ASA resin The dried ASA graft copolymer was physically blended with SAN resin (w/w, 40/60), and then melted and co-mingled for 5 min at 180 ℃ using a double-roll opener to obtain ASA resin with 24% gum content. 2.4 Testing and Characterization The notched impact strength was evaluated using a cantilever beam impact tester (model AJU-22, Chengde Test Machinery Factory, China) according to ASTM-256 at 23 ℃. The tensile strengths of ASA resins were measured by an Instron instrument according to ASTM-638 at 23 ℃ and a tensile rate of 50 mm/min. The conversion rate was calculated by gravimetric method. The grafting rate was calculated as the mass ratio of grafted SAN to the that of rubber phase. The grafting efficiency was estimated as the percentage of the grafted SAN copolymer to the total mass of SAN. For these tests, acetone was used as the solvent and free SAN was washed away by shaking and centrifugation to yield PBA-g-SAN copolymer. The washed-away free SAN acetone solution was used for NMR testing. The structures of the PBA-g-SAN copolymers were analyzed by Fourier transform infrared spectroscopy (FTIR, Nicolet IS50, Thermo Fisher, Waltham, USA). The spectra were recorded at a spectral acquisition resolution of 4 cm − 1 and a scanning range of 4000 − 400 cm − 1 of washed and dried samples with acetone. The compositions of both grafted SAN and matrix SAN were analyzed using nuclear magnetic resonance spectrometry (NMR, Avance Ⅲ 400M, Bruker, Germany). The 1 H NMR spectra of the SAN resins were recorded using CDCl 3 as a solvent and tetramethylsilane (TMS) as a calibration. Here, the grafted SAN composition can be determined to be consistent with the free SAN composition, and ethanol was added to the acetone solution of the free SAN in the grafting rate test to precipitate the free SAN, and centrifugation and drying yielded the pure free SAN. The particle size of latex was characterized by a dynamic light scattering particle size analyzer (DLS, Zetasizer- ZS90, Malvern, UK). The thermodynamic analysis of ASA resins was carried out on a Dynamic Mechanical Analyzer (DMA, Q-800, TA, USA). The measurements were carried out in single cantilever beam mode over a temperature range of -70°C to 130°C with a ramp rate of 3°C/minute at 1 Hz. The ASA resin notched impact sample sections were viewed by scanning electron microscopy (SEM, JSM-6510, Japan). To increase the conductivity, the sections were covered with a thin gold layer fabricated by an automatic fine coater (JFC-1600, Japan). The interfacial adhesion between the rubber and matrix resin was determined by the lap-shear method. To this end, the double outer SAN plates were used to sandwich the inner ASA graft copolymer plates. The obtained three plates were then placed and welded together in a compression mold at 130°C and 2 MPa for 7 min to ensure completely bonded plates. Next, the lap shear plates were cut after completion of the bonding to yield sample strips forming a lap shear head of 1 cm 2 . 3. Results and discussion 3.1 Interface bonding analysis The interfacial adhesion between ASA core-shell particles and matrix may affect the impact resistance of ASA resins. Thus, the interfacial adhesions between the matrix SAN and ASA graft copolymer at different AN contents in the grafted SAN were studied. As shown in Fig. 1 , a difference in AN between the graft SAN and matrix SAN (w/w, AN/St, 25/75) was recorded. In other words, the interfacial adhesion between ASA graft copolymer and SAN matrix reached a maximum at the AN level of graft SAN lower than that of matrix SAN by 4%. Also, elevated contents of AN significantly decreased the interfacial adhesion between both. 3.2 Particle size analysis The particle sizes and particle size distribution of large-size PBA latex particles and ASA latex particles synthesized by emulsion polymerization are shown in Fig. 2 . The average size of the PBA particles was estimated to be 391.9 nm, while that of ASA particles was around 440 nm. The particle size distribution graph revealed that AN contents of grafted SAN of 21% and 23% generated large and small particles. The generation of small particles was attributed to the occurrence of secondary nucleation during the grafting process, while large particle formation was linked to the difference in solubility parameters between AN, St copolymer, and auto polymer. St tended to form internal grafts inside PBA, while AN tended to copolymerize with St to form an externally grafted SAN layer on the surface of latex particles. As shown in the particle size distribution diagram, the internal grafting of St increased the effective volume of large-size PBA rubber particles. Meanwhile, the synergistic toughening of small and large rubber particles in ASA resins improved the impact toughness of ASA resins to a certain extent. 3.3 Mechanical properties analysis Table 3 Effect of AN content of grafted SAN on grafting parameters of ASA graft copolymers. AN content (%) grafting rate (%) Grafting efficiency (%) 21 36.78 55.18 23 38.31 57.46 25 34.54 51.81 27 36.52 54.79 29 44.67 67.00 The impact properties of ASA resins are important for end use. Meanwhile, both the modifier type and core-shell ratio may affect the impact strength and brittle-toughness transition of rubber-toughened polymeric materials. Therefore, ASA core-shell particles with a core-shell ratio of 6/4 were prepared by two-stage emulsion polymerization at a fixed mass mixing ratio of ASA graft copolymer and SAN resin of 4/6. The rubber particles under such a mixing ratio produced dense cavities under stress concentration accompanied by the generation of a large number of silver lines, resulting in ASA resin with excellent impact toughness. The effect of the AN content of graft SAN on the impact properties of ASA resin is provided in Fig. 3 a. The composition of the shell layer of the core-shell modifier is similar to that of the base resin, and the compatibility between them is high, so the toughening effect is more excellent. The theoretical AN content of the SAN base resin was estimated to be 25%, while the highest value of impact did not occur at the best compatibility. In other words, the same AN content of the graft SAN and the base SAN of 25% shifted to 21% instead. In Fig. 4 a and 4 b, a good correlation was obtained between impact strength and lap shear strength, as well the impact strength and ASA particle size distribution. The best interfacial adhesion between grafted SAN and matrix SAN was achieved at 21% AN content of grafted SAN. Meanwhile, the superposition of the stress field of both small and large rubber particles can maximize the cavitation of the rubber particles and generate silver lines to yield ASA resin with the best impact toughness. The influence of the AN content of grafted SAN on the tensile properties of ASA resin is presented in Fig. 3 b. Combined with the grafting rate analysis (Table 3 ), the highest grafting rate of ASA graft copolymers was recorded at 29% AN content of grafted SAN. However, much higher grafting rates increased the modulus of rubber particles [ 28 – 31 ] Therefore, the lowest modulus loss and the highest tensile strength of the ASA resin were accomplished at 29% AN content of grafted SAN. The maximum elongation at the break of the ASA resin was achieved at about 21% AN content of grafted SAN. This can be attributed to the superposition of the stress field of small and large rubber particles, as well as the sufficient interfacial adhesion between the grafted SAN and matrix SAN to sufficiently trigger the generation of silvering and cavitation of rubber particles to yield large-scale shear yielding of the matrix at low strain rates [ 32 ] . The low elongation at the break of the grafted SAN with 29% AN content can be attributed to the high modulus of the rubber particles and the low interfacial adhesion that cannot effectively produce silvering. Moreover, much higher grafting rates were detrimental to the dispersion of rubber particles [ 33 – 35 ] . The impact and tensile fracture samples of grafted SAN with different AN contents of ASA resin are provided in Fig. 5 . The fracture surfaces of the notched impact samples all showed obvious stress whitening phenomena without showing complete breakage. Thus, the as-prepared ASA resins possessed good impact toughness. The tensile fracture samples showed a large area of shear yielding, attributed to the low strain rate that increased the contribution of silvering. 3.4 Component Analysis Table 4 Composition of 2437 SAN and grafted SAN with different AN contents. SAN St (wt %) AN (wt %) SAN2437 82.71 17.29 SAN 21 86.82 13.18 SAN 25 82.63 17.37 SAN 29 74.88 25.12 The FTIR spectra of copolymers of SAN grafted with different AN contents of ASA are shown in Fig. 6 a. The nitrile group (C ≡ N) of acrylonitrile was identified by the FTIR peak at 2238 cm − 1 . The peaks at 699 cm − 1 , 757 cm − 1 indicate the benzene ring bending vibration of styrene, and the peaks at 1448 cm − 1 , 1491 cm − 1 , and 1600 cm − 1 indicate the benzene backbone vibration of styrene. The peaks at 2863 cm − 1 and 2927 cm − 1 were associated with the symmetric stretching and asymmetric stretching of the carbon-hydrogen bond (-CH 2 ) symmetric stretching and asymmetric stretching. Those at 1165 cm − 1 and 1730 cm − 1 were assigned to the stretching vibration of the carbon-oxygen bond (C-O-C) and carbonyl group (C = O) in poly(butyl acrylate), respectively [ 36 ] . No significant shift in FTIR peaks was recorded, indicating no strong interactions between the groups during the reaction process. Hence, the shell composition of the ASA graft copolymers within an appropriate range did not significantly affect the ASA structure. The 1 H NMR spectra of grafted SANs with different AN contents in comparison with 2437 SAN resins are shown in Fig. 6 b. The compositions of grafted SAN in comparison with 2437 SAN with different AN contents were calculated based on the peak areas of -C 6 H 5 and -CHCN-proton [ 37 ] . As shown in Table 4 , the compositions of grafted SAN with 25% AN content and 2437 SAN (w/w, AN/St, 25/75) looked the same. Grafted SAN with 21% AN content did illustrate AN differences with 2437 SAN. Also, the ASA graft copolymer possessed high interfacial adhesion with the matrix SAN. 3.5 Dynamic Mechanical Analysis The DMA curves of ASA resins with different AN contents of grafted SAN are shown in Fig. 7 . The peaks of the temperature-dependent curves of tanδ characterized the specific glass transition temperatures of the ASA resins, as shown in Table 5 . The low-temperature glass transition temperatures of the ASA resins did not significantly change (-46°C to -48°C) as a function of acrylonitrile content. Meanwhile, the change in the acrylonitrile content of the glass shell layer showed little effect on the structure of the ASA resin. From the single high-temperature peak, the variation of the acrylonitrile content of the shell layer within an appropriate range did not significantly affect the compatibility between the ASA graft copolymer and the SAN matrix. The loss modulus curves of grafted SAN for ASA resins with different AN contents are shown in Fig. 7 b. The ASA resins with 21% and 29% acrylonitrile content grafted with SAN have a high level of loss peaks in both the low-temperature and room-temperature segments. The reason for this can be attributed to the cross-penetration network formed between the SAN shell layer and the PBA core layer. At 21% acrylonitrile content, the internal grafting of more St in the graft monomer increased the volume of the PBA rubber phase. This, in turn, enhanced the interaction between the dispersed phase of PBA and the continuous phase of SAN in the ASA resin. Meanwhile, the interfacial adhesion between the PBA rubber particles and the base SAN greatly improved. The cross-interpenetrating network inhibited the movement of the rubber phase, resulting in a higher low-temperature loss peak of the ASA resin. The highest grafting rate was recorded at an acrylonitrile content of 29%. The interaction between the dispersed phase of PBA and the continuous phase of SAN was also the strongest, and the cross-interpenetrating network resulted in the highest loss peak in the low-temperature region. However, the occlusion formed by the higher grafting rate was not conducive to the interfacial adhesion between the PBA rubber particles and the matrix SAN. Table 5 Glass transition temperatures of ASA resins grafted with SAN at different AN contents. AN content (%) T g1 (℃) T g2 (℃) 21 -47.5 115.6 23 -46.6 114.5 25 -46.5 115.5 27 -48.5 115.5 29 -47.8 115.6 3.6 Section Topography analysis The mechanical properties of modified resins are often affected by the impact section morphology. For stress concentration around the core-shell modified particles, the rubber particles induce cavitation and silvering accompanied by plastic flow of the matrix. Therefore, the impact resistance of modified resins is generally determined by the density of cavitation of rubber particles and the strength of the plastic flow of the matrix. SEM images of notched impact sections of grafted SAN ASA resins with different AN contents are provided in Fig. 8 . The notched impact section of AN content of 21% ASA in Fig. 8 a-b revealed a very rough surface, dense rubbery cavities, and synapses, typical characteristics of ductile fracture. In Fig. 8 c, the notched impact section of 23% AN ASA was visible, and a rougher surface with dense synapses was observed. The flatness of some areas and the absence of rubber cavities resulted in lower impact strength when compared to the 21% AN ASA resin. In Fig. 8 d-e, the notched impact sections of 25 and 27% AN ASA displayed synapses disappearing at such AN contents and being replaced by a lamellar structure. Thus, the ASA resins with such AN content flowed poorly under external forces, reducing the shear-yielding capacity of the matrix. Figure 8 f shows the impact section of an ASA with 29% AN content, where it is observed that the section is flat and the rubber particles are unevenly dispersed. This phenomenon is due to the weak interfacial adhesion between the ASA core-shell particles and the matrix SAN. Also, the ASA core-shell particles possessed high grafting rates, resulting in a high rubber modulus and a thicker shell layer. Accordingly, ASA particles acted as rigid particles instead of impact modifiers in the matrix. Figure 9 shows the microscopic schematic of the fracture surface of the ASA resin when subjected to external forces. The ASA core-shell particles with 29% acrylonitrile content grafted with SAN have a weak ability to induce cavitation and silvering due to the insufficient interfacial adhesion between the rubber particles and the SAN matrix, and the superposition of the stress field between the rubber particles with a narrow particle size distribution is not strong enough. The ASA core-shell particles with 21% acrylonitrile content grafted with SAN have the best interfacial adhesion and the widest particle size distribution, and the superposition of the stress field of the rubber particles of different sizes under the action of external force can sufficiently trigger the silvering and cavitation of the rubber particles. Therefore, the ASA resin with this AN content has the most excellent impact toughness. 4. Conclusions In this work, a series of PBA-g-SAN graft copolymers were prepared by varying the acrylonitrile (AN) content of grafted SAN, which was melt blended with 2437 SAN (w/w, AN/St, 25/75) to obtain ASA resins with excellent impact resistance. The impact strength of the ASA resin with 21% AN content of grafted SAN jumped to a maximum value of 277.49 J/m, which was more than 80% higher than that of the ASA resin with 25% AN content of grafted SAN. This AN content of ASA graft copolymer and SAN matrix has the most excellent interfacial adhesion, and the ASA particles have the widest particle size distribution St grafting increases the volume of PBA rubber particles, the size of the rubber particles of the superposition of the stress field, resulting in synergistic toughening effect. ASA resin in the excellent interfacial adhesion and the synergistic toughening of large and small rubber particles of the dual role, the impact resistance performance to reach the best. 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Apparatus and data handling. Journal of Applied Polymer Science, 1976, 20(4): 1107-1116. Mao Z, Zhang J. Largely improved the low-temperature toughness of acrylonitrile-styrene-acrylate (ASA) resin: Fabricated a core-shell structure of two elastomers through the differences of interfacial tensions. Applied Surface Science, 2018, 444:345-354. Akitt J, Mann E B. NMR and Chemistry. Taylor and Francis; CRC Press:2014-04-21. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-3250207","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":226428425,"identity":"d35f60d1-31fb-4e62-8ae3-33371bf69d86","order_by":0,"name":"Mengen Liu","email":"","orcid":"","institution":"","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Mengen","middleName":"","lastName":"Liu","suffix":""},{"id":226428426,"identity":"4d9610a4-0522-4775-89a3-f7b1dd2ec65d","order_by":1,"name":"Qianyi Tang","email":"","orcid":"","institution":"","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Qianyi","middleName":"","lastName":"Tang","suffix":""},{"id":226428427,"identity":"8cbdd091-91db-4f2d-89ed-d50607b4b73c","order_by":2,"name":"Bai-jun Liu","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA80lEQVRIiWNgGAWjYBACfmbmAwcSeCR42NibD0DFEvBrkWxvS3zwQMZGjp/nGEipAWEtBj1njA0f2KQZS87wMSBSi0SCmURCzuHEDTd4Pn742faHgZ89x4Dh5w7cWswlEtIkEs4Atdzu3SzZ22bAINnzxoCx9wxuLZYzEo5JJPYAtdw5u42ZEajF4EaOAZCBx2E3EtskEv+BHJbzDKzFnqCWM4eZDRJ4QN7PYYPYIkFACzCQGR8k8IAD2Viy55wxj8SZZwUHe/Fo4Wfm/3DwByQqH374USYnx9+evPHBTzxaMAAPiDhAgoZRMApGwSgYBVgAACxmVOlaaSYUAAAAAElFTkSuQmCC","orcid":"https://orcid.org/0000-0002-4881-5132","institution":"Changchun University of Technology","correspondingAuthor":true,"submittingAuthor":false,"prefix":"","firstName":"Bai-jun","middleName":"","lastName":"Liu","suffix":""},{"id":226428428,"identity":"dc5a399b-e445-4b88-8b01-c5301c370b4a","order_by":3,"name":"Ming-yao ZHANG","email":"","orcid":"","institution":"","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Ming-yao","middleName":"","lastName":"ZHANG","suffix":""}],"badges":[],"createdAt":"2023-08-09 23:36:43","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-3250207/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-3250207/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":41868483,"identity":"3ba2a7ab-a347-45a9-92c8-aa3d90b38ae8","added_by":"auto","created_at":"2023-08-21 13:20:27","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":29050,"visible":true,"origin":"","legend":"\u003cp\u003eEffect of AN content of grafted SAN on lap shear strength between matrix SAN.\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-3250207/v1/5e333004acf30f0e923b9df7.png"},{"id":41869697,"identity":"6aafa844-e95c-4062-9e4a-4e16c37df8fb","added_by":"auto","created_at":"2023-08-21 13:28:27","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":169413,"visible":true,"origin":"","legend":"\u003cp\u003eThe particle sizes and particle size distributions of nuclear PBA and ASA particles with different acrylonitrile contents.\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-3250207/v1/dfa4023de20dc76cf4e2f509.png"},{"id":41871675,"identity":"9a083f2d-b567-4365-b90e-6876cbef1635","added_by":"auto","created_at":"2023-08-21 13:36:27","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":124835,"visible":true,"origin":"","legend":"\u003cp\u003eEffect of AN content of grafted SAN on mechanical properties of ASA resin: (a) notched impact strength, (b) tensile strength and elongation at break.\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-3250207/v1/80466dd926ac257a445adcba.png"},{"id":41868484,"identity":"49447794-86d4-45fd-aed2-d470faeb9074","added_by":"auto","created_at":"2023-08-21 13:20:27","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":66147,"visible":true,"origin":"","legend":"\u003cp\u003eImpact strength as a function of lap shear strength (a), Impact strength as a function of particle size distribution (b).\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-3250207/v1/99a589b7126b3350ad7755d7.png"},{"id":41868489,"identity":"83be0006-c54f-4ea4-9ca5-afc7a6e816f6","added_by":"auto","created_at":"2023-08-21 13:20:27","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":367096,"visible":true,"origin":"","legend":"\u003cp\u003eImpact and tensile fracture samples of grafted SAN ASA resins with different AN contents: (a) 21 %, (b) 23 %, (c) 25 %, (d) 27 %, and (e) 29 %.\u003c/p\u003e","description":"","filename":"floatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-3250207/v1/b9a36b01c7bfb465dc71415f.png"},{"id":41869699,"identity":"b74b96af-6c28-4886-8033-2c60b3b92746","added_by":"auto","created_at":"2023-08-21 13:28:27","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":140712,"visible":true,"origin":"","legend":"\u003cp\u003e(a) FTIR spectra of ASA graft copolymers with different AN contents of grafted SAN, (b) \u003csup\u003e1\u003c/sup\u003eH NMR spectra of grafted SAN and 2437SAN with different AN contents.\u003c/p\u003e","description":"","filename":"floatimage6.png","url":"https://assets-eu.researchsquare.com/files/rs-3250207/v1/2047fa96782190ca8f014bde.png"},{"id":41868487,"identity":"6333e11c-fea1-46db-898f-e5cc27296b5e","added_by":"auto","created_at":"2023-08-21 13:20:27","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":124311,"visible":true,"origin":"","legend":"\u003cp\u003eDMA curves of ASA resin at different AN contents of grafted SAN: (a) tanδ curves, and (b) loss peak curves.\u003c/p\u003e","description":"","filename":"floatimage7.png","url":"https://assets-eu.researchsquare.com/files/rs-3250207/v1/baed2cf753146de01e3dbc86.png"},{"id":41868491,"identity":"89f0e7b6-ae20-41c7-9c4c-e2619697aaed","added_by":"auto","created_at":"2023-08-21 13:20:28","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":560248,"visible":true,"origin":"","legend":"\u003cp\u003eSEM images of the impact fracture surface of ASA resin with different AN contents of grafted SAN at various magnifications. (a) 21 % 10000x, (b) 21 % 3000x, (c) 23 % 3000x, (d) 25 % 3000x, (e) 27% 3000x, and (f) 29% 3000x.\u003c/p\u003e","description":"","filename":"floatimage8.png","url":"https://assets-eu.researchsquare.com/files/rs-3250207/v1/8148e861e8f2a62c40fc923e.png"},{"id":41869698,"identity":"6a630111-25db-434e-ad84-b41ae941b4ec","added_by":"auto","created_at":"2023-08-21 13:28:27","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":108224,"visible":true,"origin":"","legend":"\u003cp\u003eMicroscopic schematic of the impact section of ASA resin. ASA with 21 % AN content of grafted SAN and 29 % AN content of grafted SAN.\u003c/p\u003e","description":"","filename":"floatimage9.png","url":"https://assets-eu.researchsquare.com/files/rs-3250207/v1/777793851b02c4744bef3699.png"},{"id":46490717,"identity":"0cdf8b12-bee1-4da5-b7f2-9541094683ba","added_by":"auto","created_at":"2023-11-15 14:13:30","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1878282,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-3250207/v1/48e387ba-71e2-46c2-8708-ae2276ed0c7c.pdf"}],"financialInterests":"","formattedTitle":"Core-Shell Structure Acrylonitrile-Styrene-Acrylate Particles with Different Acrylonitrile Contents Improved Toughness of Poly(styrene-co-acrylonitrile) Resins","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eToughening of polymer materials has been widely researched and rapidly developed in recent decades due to its unparalleled importance in business, such as strengthening and toughening of polymer materials such as epoxy resins, poly cross esters, and polypropylene \u003csup\u003e[\u003cspan additionalcitationids=\"CR2 CR3 CR4\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]\u003c/sup\u003e. To improve the impact toughness of polymer materials for practical applications, several new techniques have been developed. For example, the most widely used application in toughening polymer materials is the development of a two-phase structure that uses rubber as the dispersed phase to improve the brittle fracture characteristics of polymers \u003csup\u003e[\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]\u003c/sup\u003e. The presence of rubber particles as the dispersed phase concentrate and cavitate under load may cause silvering or shear yielding of the matrix around it, thereby resulting in toughened polymer materials \u003csup\u003e[\u003cspan additionalcitationids=\"CR8 CR9\" citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]\u003c/sup\u003e Rubber toughening of polymer materials depends on several factors, such as the interfacial adhesion between the rubber phase and polymer matrix, the degree of dispersion of the rubber, and the inherent ductility of the matrix \u003csup\u003e[\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003ePolystyrene acrylonitrile (SAN) random copolymer is a typical glassy thermoplastic polymer characterized by brittle fracture which severely limits its application. Therefore, modification of SAN resins has extensively been explored to improve its brittle fracture. For example, Xu et al. toughened SAN resins using PBL-g-SAN, PBA-g-SAN, and high-rubber EPDM-SAN impact modifiers \u003csup\u003e[\u003cspan additionalcitationids=\"CR14\" citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]\u003c/sup\u003e. Their results revealed the formation of PBA-g-SAN impact-modified particles consisting of a core made of crosslinked PBA rubber particles and a shell composed of grafted SAN. In this fashion, the SAN microzone transition layer showed good compatibility with the SAN matrix, ensuring better dispersion of the rubber particles in the matrix of SAN resin \u003csup\u003e[\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]\u003c/sup\u003e. In another study, PBA-g-SAN impact modifier and SAN resin were prepared by melt blending to obtain ASA resin with mechanical properties comparable to those of ABS resin coupled with excellent weather resistance, coloring, and chemical corrosion resistance \u003csup\u003e[\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]\u003c/sup\u003e. Therefore, ASA resin is widely used in automotive, electrical and electronic, gardening, and other fields.\u003c/p\u003e \u003cp\u003eThe factors affecting toughened polymers, such as rubber phase size and distribution, grafting rate, and core-shell morphology have widely been investigated \u003csup\u003e[\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]\u003c/sup\u003e. For instance, Huang investigated the impact of PBA seeds on the feeding mode of monomers ratio on the growth of nucleated particles \u003csup\u003e[\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]\u003c/sup\u003e. Tolue explored the effect of the type of surfactant, as well as the mode of incorporation of second-stage monomers on the final morphologies of latex particles \u003csup\u003e[\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]\u003c/sup\u003e. Choi studied the influence of the grafting rate on the tensile properties of high-impact polystyrene (HIPS) \u003csup\u003e[\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]\u003c/sup\u003e. In addition, the composition of core-shell particles may also influence the mechanical properties of the blends. For instance, Kumaraswamy et al. recorded that the miscibility and phase separation in SAN/PMMA blends investigated by positron lifetime measurements \u003csup\u003e[\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]\u003c/sup\u003e. So far, numerous studies have been conducted on the toughening of SAN resins by ASA core-shell graft copolymers. However, no in-depth studies have been conducted on the mechanism of toughening of SAN resins by the composition of its shell monomer.\u003c/p\u003e \u003cp\u003eHerein, emulsion polymerization was used to prepare modified particles of poly(butyl acrylate, PBA) as the rubber core and poly(styrene-acrylonitrile) (SAN) as the glassy polymer shell. During the polymerization process, the PBA rubber particles were slightly crosslinked to ensure the construction of the core-shell structure during grafting, as well as provide a better toughening effect \u003csup\u003e[\u003cspan additionalcitationids=\"CR25 CR26\" citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]\u003c/sup\u003e The unreacted double bonds during the crosslinking process of the PBA rubber particles provided grafting sites for the grafted SAN resins. Similarly, the unreacted double bonds during crosslinking of PBA rubber particles provided grafting sites for subsequent grafting. The grafted SANs also provided good interfacial adhesion between the rubber particles and the matrix. The effect of acrylonitrile content in ASA graft copolymers on the toughness of ASA resins was investigated by focusing on the synergistic toughening of ASA graft copolymers and SAN substrates with large and small rubber particles, it was found that the toughness of ASA resin jumped to the maximum value at 21% acrylonitrile content of grafted SAN.\u003c/p\u003e"},{"header":"2. Experimental","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1 Materials\u003c/h2\u003e \u003cp\u003eButyl acrylate (BA) was purchased from Shanghai Titan Technology Co. Sodium dodecyl sulfate (SDS), potassium carbonate (K\u003csub\u003e2\u003c/sub\u003eCO\u003csub\u003e3\u003c/sub\u003e), and potassium persulfate (KPS) were all received from Tianjin Fuchen Chemical Reagent Co. Ethylene glycol dimethacrylate (EDGMA) was obtained from Shanghai Aladdin Biochemical Technology Co. SAN (Jihua 2437, St/AN, 75/25, w/w), styrene (St), acrylonitrile (AN), and tertiary dodecyl mercaptan (TDDM) were provided by Jilin Chemical Co. Acetone was purchased from Chengdu Cologne Chemical Co.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2 Synthesis of ASA Latex\u003c/h2\u003e \u003cp\u003eThe ASA core-shell latexes were prepared by a two-stage emulsion polymerization method. The reaction takes place in a three-necked flask, water bath heating, condensation reflux, and mechanical stirring. The reaction system was synthesized at 65\u0026deg;C for 2h and 85\u0026deg;C for 1h to synthesize large particle-size PBA latex. The formulations are summarized in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. St and AN monomers were grafted onto PBA cores under the same conditions at a fixed total mass of the monomers and varied AN content during the dropwise monomer pre-emulsion to 21%-29% to yield ASA core-shell latexes with different AN acrylonitrile contents (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). Note that all monomer pre-emulsions were fully pre-emulsified at room temperature.\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\u003ePreparation conditions of PBA latexes.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"2\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eReagent\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eQuality (g)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e100\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eEDGMA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDDI\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e67\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNa\u003csub\u003e2\u003c/sub\u003eCO\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.9\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSDS\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eKPS\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.4\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 \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\u003ePreparation conditions of ASA latexes (g).\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eReagent\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eA\u003csub\u003e21\u003c/sub\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eA\u003csub\u003e23\u003c/sub\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eA\u003csub\u003e25\u003c/sub\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eA\u003csub\u003e27\u003c/sub\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eA\u003csub\u003e29\u003c/sub\u003e\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCore phase latex\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e200\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e200\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e200\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e200\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e200\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDDI\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e199\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e199\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e199\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e199\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e199\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAN\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e16.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e18.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e21.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e23.2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSt\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e63.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e61.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e60\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e58.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e56.8\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSDS\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eKPS\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.32\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.32\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.32\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.32\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.32\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\u003eA\u003csub\u003e21\u003c/sub\u003e: AN content of the grafted SAN corresponds to 21%.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3 Preparation of ASA resin\u003c/h2\u003e \u003cp\u003eThe dried ASA graft copolymer was physically blended with SAN resin (w/w, 40/60), and then melted and co-mingled for 5 min at 180 ℃ using a double-roll opener to obtain ASA resin with 24% gum content.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e2.4 Testing and Characterization\u003c/h2\u003e \u003cp\u003eThe notched impact strength was evaluated using a cantilever beam impact tester (model AJU-22, Chengde Test Machinery Factory, China) according to ASTM-256 at 23 ℃. The tensile strengths of ASA resins were measured by an Instron instrument according to ASTM-638 at 23 ℃ and a tensile rate of 50 mm/min.\u003c/p\u003e \u003cp\u003eThe conversion rate was calculated by gravimetric method. The grafting rate was calculated as the mass ratio of grafted SAN to the that of rubber phase. The grafting efficiency was estimated as the percentage of the grafted SAN copolymer to the total mass of SAN. For these tests, acetone was used as the solvent and free SAN was washed away by shaking and centrifugation to yield PBA-g-SAN copolymer. The washed-away free SAN acetone solution was used for NMR testing.\u003c/p\u003e \u003cp\u003eThe structures of the PBA-g-SAN copolymers were analyzed by Fourier transform infrared spectroscopy (FTIR, Nicolet IS50, Thermo Fisher, Waltham, USA). The spectra were recorded at a spectral acquisition resolution of 4 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and a scanning range of 4000\u0026thinsp;\u0026minus;\u0026thinsp;400 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e of washed and dried samples with acetone.\u003c/p\u003e \u003cp\u003eThe compositions of both grafted SAN and matrix SAN were analyzed using nuclear magnetic resonance spectrometry (NMR, Avance Ⅲ 400M, Bruker, Germany). The \u003csup\u003e1\u003c/sup\u003eH NMR spectra of the SAN resins were recorded using CDCl\u003csub\u003e3\u003c/sub\u003e as a solvent and tetramethylsilane (TMS) as a calibration. Here, the grafted SAN composition can be determined to be consistent with the free SAN composition, and ethanol was added to the acetone solution of the free SAN in the grafting rate test to precipitate the free SAN, and centrifugation and drying yielded the pure free SAN.\u003c/p\u003e \u003cp\u003eThe particle size of latex was characterized by a dynamic light scattering particle size analyzer (DLS, Zetasizer- ZS90, Malvern, UK). The thermodynamic analysis of ASA resins was carried out on a Dynamic Mechanical Analyzer (DMA, Q-800, TA, USA). The measurements were carried out in single cantilever beam mode over a temperature range of -70\u0026deg;C to 130\u0026deg;C with a ramp rate of 3\u0026deg;C/minute at 1 Hz.\u003c/p\u003e \u003cp\u003eThe ASA resin notched impact sample sections were viewed by scanning electron microscopy (SEM, JSM-6510, Japan). To increase the conductivity, the sections were covered with a thin gold layer fabricated by an automatic fine coater (JFC-1600, Japan).\u003c/p\u003e \u003cp\u003eThe interfacial adhesion between the rubber and matrix resin was determined by the lap-shear method. To this end, the double outer SAN plates were used to sandwich the inner ASA graft copolymer plates. The obtained three plates were then placed and welded together in a compression mold at 130\u0026deg;C and 2 MPa for 7 min to ensure completely bonded plates. Next, the lap shear plates were cut after completion of the bonding to yield sample strips forming a lap shear head of 1 cm\u003csup\u003e2\u003c/sup\u003e.\u003c/p\u003e \u003c/div\u003e"},{"header":"3. Results and discussion","content":"\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003e3.1 Interface bonding analysis\u003c/h2\u003e \u003cp\u003eThe interfacial adhesion between ASA core-shell particles and matrix may affect the impact resistance of ASA resins. Thus, the interfacial adhesions between the matrix SAN and ASA graft copolymer at different AN contents in the grafted SAN were studied. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, a difference in AN between the graft SAN and matrix SAN (w/w, AN/St, 25/75) was recorded. In other words, the interfacial adhesion between ASA graft copolymer and SAN matrix reached a maximum at the AN level of graft SAN lower than that of matrix SAN by 4%. Also, elevated contents of AN significantly decreased the interfacial adhesion between both.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003e3.2 Particle size analysis\u003c/h2\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe particle sizes and particle size distribution of large-size PBA latex particles and ASA latex particles synthesized by emulsion polymerization are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. The average size of the PBA particles was estimated to be 391.9 nm, while that of ASA particles was around 440 nm. The particle size distribution graph revealed that AN contents of grafted SAN of 21% and 23% generated large and small particles. The generation of small particles was attributed to the occurrence of secondary nucleation during the grafting process, while large particle formation was linked to the difference in solubility parameters between AN, St copolymer, and auto polymer. St tended to form internal grafts inside PBA, while AN tended to copolymerize with St to form an externally grafted SAN layer on the surface of latex particles. As shown in the particle size distribution diagram, the internal grafting of St increased the effective volume of large-size PBA rubber particles. Meanwhile, the synergistic toughening of small and large rubber particles in ASA resins improved the impact toughness of ASA resins to a certain extent.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003e3.3 Mechanical properties analysis\u003c/h2\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \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\u003eEffect of AN content of grafted SAN on grafting parameters of ASA graft copolymers.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"3\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"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 \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAN content (%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003egrafting rate (%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eGrafting efficiency (%)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e21\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e36.78\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e55.18\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e23\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e38.31\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e57.46\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e34.54\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e51.81\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e27\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e36.52\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e54.79\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e29\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e44.67\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e67.00\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\u003eThe impact properties of ASA resins are important for end use. Meanwhile, both the modifier type and core-shell ratio may affect the impact strength and brittle-toughness transition of rubber-toughened polymeric materials. Therefore, ASA core-shell particles with a core-shell ratio of 6/4 were prepared by two-stage emulsion polymerization at a fixed mass mixing ratio of ASA graft copolymer and SAN resin of 4/6. The rubber particles under such a mixing ratio produced dense cavities under stress concentration accompanied by the generation of a large number of silver lines, resulting in ASA resin with excellent impact toughness.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe effect of the AN content of graft SAN on the impact properties of ASA resin is provided in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea. The composition of the shell layer of the core-shell modifier is similar to that of the base resin, and the compatibility between them is high, so the toughening effect is more excellent. The theoretical AN content of the SAN base resin was estimated to be 25%, while the highest value of impact did not occur at the best compatibility. In other words, the same AN content of the graft SAN and the base SAN of 25% shifted to 21% instead. In Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ea and \u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eb, a good correlation was obtained between impact strength and lap shear strength, as well the impact strength and ASA particle size distribution. The best interfacial adhesion between grafted SAN and matrix SAN was achieved at 21% AN content of grafted SAN. Meanwhile, the superposition of the stress field of both small and large rubber particles can maximize the cavitation of the rubber particles and generate silver lines to yield ASA resin with the best impact toughness.\u003c/p\u003e \u003cp\u003eThe influence of the AN content of grafted SAN on the tensile properties of ASA resin is presented in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eb. Combined with the grafting rate analysis (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e), the highest grafting rate of ASA graft copolymers was recorded at 29% AN content of grafted SAN. However, much higher grafting rates increased the modulus of rubber particles \u003csup\u003e[\u003cspan additionalcitationids=\"CR29 CR30\" citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e]\u003c/sup\u003e Therefore, the lowest modulus loss and the highest tensile strength of the ASA resin were accomplished at 29% AN content of grafted SAN. The maximum elongation at the break of the ASA resin was achieved at about 21% AN content of grafted SAN. This can be attributed to the superposition of the stress field of small and large rubber particles, as well as the sufficient interfacial adhesion between the grafted SAN and matrix SAN to sufficiently trigger the generation of silvering and cavitation of rubber particles to yield large-scale shear yielding of the matrix at low strain rates \u003csup\u003e[\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e]\u003c/sup\u003e. The low elongation at the break of the grafted SAN with 29% AN content can be attributed to the high modulus of the rubber particles and the low interfacial adhesion that cannot effectively produce silvering. Moreover, much higher grafting rates were detrimental to the dispersion of rubber particles \u003csup\u003e[\u003cspan additionalcitationids=\"CR34\" citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eThe impact and tensile fracture samples of grafted SAN with different AN contents of ASA resin are provided in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e. The fracture surfaces of the notched impact samples all showed obvious stress whitening phenomena without showing complete breakage. Thus, the as-prepared ASA resins possessed good impact toughness. The tensile fracture samples showed a large area of shear yielding, attributed to the low strain rate that increased the contribution of silvering.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003e3.4 Component Analysis\u003c/h2\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\u003eComposition of 2437 SAN and grafted SAN with different AN contents.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"3\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"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 \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSAN\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSt (wt %)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eAN (wt %)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSAN2437\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e82.71\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e17.29\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSAN 21\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e86.82\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e13.18\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSAN 25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e82.63\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e17.37\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSAN 29\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e74.88\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e25.12\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\u003eThe FTIR spectra of copolymers of SAN grafted with different AN contents of ASA are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ea. The nitrile group (C\u0026thinsp;\u0026equiv;\u0026thinsp;N) of acrylonitrile was identified by the FTIR peak at 2238 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. The peaks at 699 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, 757 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e indicate the benzene ring bending vibration of styrene, and the peaks at 1448 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, 1491 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, and 1600 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e indicate the benzene backbone vibration of styrene. The peaks at 2863 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 2927 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e were associated with the symmetric stretching and asymmetric stretching of the carbon-hydrogen bond (-CH\u003csub\u003e2\u003c/sub\u003e) symmetric stretching and asymmetric stretching. Those at 1165 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 1730 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e were assigned to the stretching vibration of the carbon-oxygen bond (C-O-C) and carbonyl group (C\u0026thinsp;=\u0026thinsp;O) in poly(butyl acrylate), respectively \u003csup\u003e[\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e]\u003c/sup\u003e. No significant shift in FTIR peaks was recorded, indicating no strong interactions between the groups during the reaction process. Hence, the shell composition of the ASA graft copolymers within an appropriate range did not significantly affect the ASA structure.\u003c/p\u003e \u003cp\u003eThe \u003csup\u003e1\u003c/sup\u003eH NMR spectra of grafted SANs with different AN contents in comparison with 2437 SAN resins are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003eb. The compositions of grafted SAN in comparison with 2437 SAN with different AN contents were calculated based on the peak areas of -C\u003csub\u003e6\u003c/sub\u003eH\u003csub\u003e5\u003c/sub\u003e and -CHCN-proton \u003csup\u003e[\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e]\u003c/sup\u003e. As shown in Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e, the compositions of grafted SAN with 25% AN content and 2437 SAN (w/w, AN/St, 25/75) looked the same. Grafted SAN with 21% AN content did illustrate AN differences with 2437 SAN. Also, the ASA graft copolymer possessed high interfacial adhesion with the matrix SAN.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003e3.5 Dynamic Mechanical Analysis\u003c/h2\u003e \u003cp\u003eThe DMA curves of ASA resins with different AN contents of grafted SAN are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e. The peaks of the temperature-dependent curves of tanδ characterized the specific glass transition temperatures of the ASA resins, as shown in Table\u0026nbsp;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e5\u003c/span\u003e. The low-temperature glass transition temperatures of the ASA resins did not significantly change (-46\u0026deg;C to -48\u0026deg;C) as a function of acrylonitrile content. Meanwhile, the change in the acrylonitrile content of the glass shell layer showed little effect on the structure of the ASA resin. From the single high-temperature peak, the variation of the acrylonitrile content of the shell layer within an appropriate range did not significantly affect the compatibility between the ASA graft copolymer and the SAN matrix.\u003c/p\u003e \u003cp\u003eThe loss modulus curves of grafted SAN for ASA resins with different AN contents are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003eb. The ASA resins with 21% and 29% acrylonitrile content grafted with SAN have a high level of loss peaks in both the low-temperature and room-temperature segments. The reason for this can be attributed to the cross-penetration network formed between the SAN shell layer and the PBA core layer. At 21% acrylonitrile content, the internal grafting of more St in the graft monomer increased the volume of the PBA rubber phase. This, in turn, enhanced the interaction between the dispersed phase of PBA and the continuous phase of SAN in the ASA resin. Meanwhile, the interfacial adhesion between the PBA rubber particles and the base SAN greatly improved. The cross-interpenetrating network inhibited the movement of the rubber phase, resulting in a higher low-temperature loss peak of the ASA resin. The highest grafting rate was recorded at an acrylonitrile content of 29%. The interaction between the dispersed phase of PBA and the continuous phase of SAN was also the strongest, and the cross-interpenetrating network resulted in the highest loss peak in the low-temperature region. However, the occlusion formed by the higher grafting rate was not conducive to the interfacial adhesion between the PBA rubber particles and the matrix SAN.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab5\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 5\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eGlass transition temperatures of ASA resins grafted with SAN at different AN contents.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"3\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"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 \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAN content (%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eT\u003csub\u003eg1\u003c/sub\u003e (℃)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eT\u003csub\u003eg2\u003c/sub\u003e (℃)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e21\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e-47.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e115.6\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e23\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e-46.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e114.5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e-46.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e115.5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e27\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e-48.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e115.5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e29\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e-47.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e115.6\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\u003e3.6 Section Topography analysis\u003c/h2\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe mechanical properties of modified resins are often affected by the impact section morphology. For stress concentration around the core-shell modified particles, the rubber particles induce cavitation and silvering accompanied by plastic flow of the matrix. Therefore, the impact resistance of modified resins is generally determined by the density of cavitation of rubber particles and the strength of the plastic flow of the matrix.\u003c/p\u003e \u003cp\u003eSEM images of notched impact sections of grafted SAN ASA resins with different AN contents are provided in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e. The notched impact section of AN content of 21% ASA in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003ea-b revealed a very rough surface, dense rubbery cavities, and synapses, typical characteristics of ductile fracture. In Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003ec, the notched impact section of 23% AN ASA was visible, and a rougher surface with dense synapses was observed. The flatness of some areas and the absence of rubber cavities resulted in lower impact strength when compared to the 21% AN ASA resin. In Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003ed-e, the notched impact sections of 25 and 27% AN ASA displayed synapses disappearing at such AN contents and being replaced by a lamellar structure. Thus, the ASA resins with such AN content flowed poorly under external forces, reducing the shear-yielding capacity of the matrix. Figure\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003ef shows the impact section of an ASA with 29% AN content, where it is observed that the section is flat and the rubber particles are unevenly dispersed. This phenomenon is due to the weak interfacial adhesion between the ASA core-shell particles and the matrix SAN. Also, the ASA core-shell particles possessed high grafting rates, resulting in a high rubber modulus and a thicker shell layer. Accordingly, ASA particles acted as rigid particles instead of impact modifiers in the matrix.\u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e shows the microscopic schematic of the fracture surface of the ASA resin when subjected to external forces. The ASA core-shell particles with 29% acrylonitrile content grafted with SAN have a weak ability to induce cavitation and silvering due to the insufficient interfacial adhesion between the rubber particles and the SAN matrix, and the superposition of the stress field between the rubber particles with a narrow particle size distribution is not strong enough. The ASA core-shell particles with 21% acrylonitrile content grafted with SAN have the best interfacial adhesion and the widest particle size distribution, and the superposition of the stress field of the rubber particles of different sizes under the action of external force can sufficiently trigger the silvering and cavitation of the rubber particles. Therefore, the ASA resin with this AN content has the most excellent impact toughness.\u003c/p\u003e \u003c/div\u003e"},{"header":"4. Conclusions","content":"\u003cp\u003eIn this work, a series of PBA-g-SAN graft copolymers were prepared by varying the acrylonitrile (AN) content of grafted SAN, which was melt blended with 2437 SAN (w/w, AN/St, 25/75) to obtain ASA resins with excellent impact resistance. The impact strength of the ASA resin with 21% AN content of grafted SAN jumped to a maximum value of 277.49 J/m, which was more than 80% higher than that of the ASA resin with 25% AN content of grafted SAN. This AN content of ASA graft copolymer and SAN matrix has the most excellent interfacial adhesion, and the ASA particles have the widest particle size distribution St grafting increases the volume of PBA rubber particles, the size of the rubber particles of the superposition of the stress field, resulting in synergistic toughening effect. ASA resin in the excellent interfacial adhesion and the synergistic toughening of large and small rubber particles of the dual role, the impact resistance performance to reach the best. ASA resin, under the dual effect of excellent interfacial adhesion and synergistic toughening of large and small rubber particles, the impact resistance is optimized. In this paper, by fixing the matrix resin and changing the composition of impact-modified particles to improve the interfacial adhesion between the impact-modified particles and the matrix resin, the distribution of modified particles and the dispersion of modified particles, which provides a feasible way of thinking for toughening polymer materials.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003eAcknowledgements\u003c/p\u003e\n\u003cp\u003eThe authors appreciate the financial support from the National Natural Scientific Foundation of China (No. U21A2088) and Jilin Province Science and Technology Development Plan Project (20230201129GX).\u003c/p\u003e\n\u003cp\u003eConflict of Interest\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no conflict of interest.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eB.B. Johnsen, Kinloch A J, Mohammed R D , et al. 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Taylor and Francis; CRC Press:2014-04-21.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Acrylonitrile-Styrene-Acrylate, Core-shell structure, Interfacial adhesion, Synergistic toughening, Particle size distribution","lastPublishedDoi":"10.21203/rs.3.rs-3250207/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-3250207/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eHerein, core-shell structured grafted copolymer particles of poly(butyl acrylate) grafted polystyrene acrylonitrile (ASA) with different contents of acrylonitrile (AN) were prepared by emulsion graft polymerization. ASA resins were then obtained by melt blending of ASA graft copolymers with SAN (w/w, AN/St, 25/75) resins. This paper investigates the effect of acrylonitrile content in ASA graft copolymers on the mechanical properties of ASA resins. The particle size distribution, composition of ASA, cross-section morphology, and compatibility of the material were characterized by dynamic light scattering (DLS), nuclear magnetic resonance (NMR), scanning electron microscopy (SEM), and dynamic mechanical analysis (DMA). The results revealed the highest notched impact strength of ASA resin reaching up to 277.49 J/m at AN content of grafted SAN of 21%, equivalent to an 80% increase when compared to 25% AN content. The lap shear adhesion tests revealed excellent interfacial adhesion between the ASA particles and SAN matrix owing to the difference in AN. This significantly enhanced the toughness of the ASA resin. Additionally, the ASA particles displayed the widest particle size distribution. The synergistic toughening of small and large rubber particles also enhanced the impact resistance of ASA resin to a certain extent. Therefore, the excellent interfacial adhesion between ASA graft copolymer and SAN matrix and the synergistic toughening of large rubber particles together promote the toughness of ASA resin.\u003c/p\u003e","manuscriptTitle":"Core-Shell Structure Acrylonitrile-Styrene-Acrylate Particles with Different Acrylonitrile Contents Improved Toughness of Poly(styrene-co-acrylonitrile) Resins","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2023-08-21 13:20:22","doi":"10.21203/rs.3.rs-3250207/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"6811f639-93e4-4d8e-9b36-5cfc8adcea60","owner":[],"postedDate":"August 21st, 2023","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2023-11-15T14:05:22+00:00","versionOfRecord":[],"versionCreatedAt":"2023-08-21 13:20:22","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-3250207","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-3250207","identity":"rs-3250207","version":["v1"]},"buildId":"7rjqhiLT3MXkJMwkYKINL","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}