Lightweight high-strength expandable polystyrene material and preparation method thereof

Abstract

The invention belongs to the technical field of high polymer materials, and particularly relates to a lightweight high-strength expandable polystyrene material and a preparation method thereof. The high-temperature-resistant foaming material is prepared from the following components in parts by weight: 90 to 100 parts of styrene, 200 to 250 parts of deionized water, 0.3 to 0.6 part of a dispersing agent, 1.5 to 2.5 parts of a nucleating agent, 0.2 to 0.6 part of an initiator, 0.2 to 0.5 part of a particle size regulator, 4 to 7 parts of a foaming agent and 3 to 6 parts of composite filler, the composite filler is prepared by mixing modified graphene and modified silicon dioxide; the modified graphene is maleic anhydride copolymer sulfonate modified graphene, and the modified silicon dioxide is polydopamine / carboxymethyl cellulose modified silicon dioxide; the water dispersibility and interfacial compatibility of the composite filler are remarkably improved in a physical and chemical grafting manner, and the mechanical property, thermal stability and flame retardance of the polystyrene material are synchronously optimized by utilizing a multi-component synergistic effect.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, specifically relating to a lightweight, high-strength expandable polystyrene material and its preparation method. Background Technology

[0002] Traditional polystyrene materials are widely used in packaging, construction, and transportation due to their advantages such as lightweight, low cost, and ease of processing. However, their inherent brittleness, poor mechanical properties, and flammability limit their application in high-end fields. To improve these shortcomings, researchers typically modify polystyrene by adding inorganic fillers or flame retardants. However, inorganic fillers have poor compatibility with organic polymer matrices, are prone to agglomeration, and result in uneven dispersion, which severely affects the mechanical properties of the material. Furthermore, traditional modification methods often sacrifice other properties while improving one, making it difficult to achieve a balance of overall performance. In addition, the insufficient matching between the decomposition temperature of the foaming agent and the polymer melt viscosity in traditional foaming processes easily leads to uneven cell structure, further affecting the compressive strength and cushioning performance of the material. Therefore, developing a composite filler system that can achieve uniform dispersion of fillers, strong interfacial bonding, and synergistic effects of mechanical reinforcement and flame retardancy has become the key to breaking through the technical bottleneck of lightweight, high-strength polystyrene materials.

[0003] Currently, research on the modification of polystyrene composites mainly focuses on the following directions: first, improving the compatibility between fillers and the matrix through physical blending or chemical grafting, such as using polyethyleneimine to modify graphene or polydopamine to coat silica; second, constructing multi-scale filler networks, such as combining carbon nanotubes with layered clay to simultaneously improve strength and barrier properties; and third, introducing reactive additives (such as maleic anhydride grafts) to promote chemical bonding between fillers and the matrix. However, these methods still have limitations. Furthermore, existing technologies do not pay sufficient attention to the precise control of cell structure during the foaming process, especially the unclear mechanism by which fillers affect the decomposition behavior of nucleating agents and foaming agents, making it difficult to optimize the balance between material density and mechanical properties.

[0004] Against this backdrop, there is an urgent need for an innovative composite filler design strategy that can improve the water dispersibility and interfacial bonding of the filler through chemical modification, and simultaneously optimize mechanical properties, thermal stability and flame retardancy through the synergistic effect of multiple components. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a lightweight, high-strength expandable polystyrene material and its preparation method. By introducing raw materials such as styrene, dispersant, composite filler, and foaming agent, and especially by using a composite filler prepared by mixing modified graphene and modified silica, the mechanical properties, thermal stability, and flame retardancy of the polystyrene material are simultaneously optimized by utilizing the synergistic effect of multiple components.

[0006] The technical solution adopted by the present invention to achieve the above objectives is as follows: A lightweight, high-strength expandable polystyrene material, comprising the following components by weight: 90-100 parts styrene, 200-250 parts deionized water, 0.3-0.6 parts dispersant, 1.5-2.5 parts nucleating agent, 0.2-0.6 parts initiator, 0.2-0.5 parts particle size modifier, 4-7 parts foaming agent, and 3-6 parts composite filler; wherein the composite filler is prepared by mixing modified graphene and modified silica, with the mass ratio of modified graphene to modified silica being 10:1-3; The modified graphene is prepared as follows: S1. Under stirring conditions, styrene-maleic anhydride copolymer is dissolved in N,N-dimethylformamide, chlorosulfonic acid is added dropwise, the temperature is raised to 70-90℃, the reaction is carried out for 2-4 hours, the mixture is cooled and distilled under reduced pressure, sodium hydroxide ethanol solution is added dropwise, the reaction is carried out for 1-2 hours, and the modified styrene-maleic anhydride copolymer is obtained after filtration, washing and drying. S2. Activate graphene by acid treatment. Mix the modified styrene-maleic anhydride copolymer, the activated graphene, and N,N-dimethylformamide evenly, sonicate for 30-50 minutes, raise the temperature to 55-75℃ under stirring, react for 2-3 hours, cool to room temperature, filter, wash, and dry to obtain the final product.

[0007] The modified graphene is prepared by first sulfonating a styrene-maleic anhydride copolymer under chlorosulfonic acid, where hydrogen atoms on the benzene ring are replaced by sulfonic acid groups to generate a sulfonated copolymer. Subsequently, a neutralization reaction is carried out with sodium hydroxide ethanol solution to obtain styrene-maleic anhydride copolymer sulfonate, enhancing the copolymer's water solubility and reactivity. Then, the graphene is acid-activated, introducing oxygen-containing functional groups such as carboxyl and hydroxyl groups onto the graphene surface, increasing its surface activity and making it easier for it to interact with the copolymer sulfonate. Under ultrasonic and heating conditions, the sodium sulfonate groups of the copolymer bind to the oxygen-containing functional groups on the graphene surface through electrostatic interactions or hydrogen bonds. Simultaneously, the maleic anhydride units in the copolymer react chemically with the oxygen-containing functional groups on the graphene surface, forming covalent bonds. Finally, the copolymer sulfonate is grafted onto the graphene surface through both physical adsorption and chemical bonding to obtain maleic anhydride copolymer sulfonate-modified graphene, significantly improving the water dispersibility and interfacial compatibility of graphene.

[0008] Further, in step S1, the mass ratio of the styrene-maleic anhydride copolymer, chlorosulfonic acid, and sodium hydroxide ethanol solution is 10:4-7:30-50, and the mass-to-volume ratio of the styrene-maleic anhydride copolymer to N,N-dimethylformamide is 0.15-0.20 g / mL; the mass percentage of sodium hydroxide in the sodium hydroxide ethanol solution is 5-10%; in step S2, the mass ratio of the modified styrene-maleic anhydride copolymer and the activated graphene is 1:0.5-0.7, and the modified styrene... The mass-to-volume ratio of maleic anhydride copolymer to N,N-dimethylformamide is 0.01-0.03 g / mL; the specific steps of the acid treatment in step S2 are as follows: concentrated sulfuric acid and nitric acid are mixed evenly under ice-water bath conditions to obtain a mixed acid, then graphene is added, and ultrasonic treatment is carried out at 30-35℃ for 4.5-5.5 h, followed by dilution, filtration, washing, and drying. The volume ratio of concentrated sulfuric acid to nitric acid is 2.5-3.5:1, and the mass-to-volume ratio of graphene to mixed acid is 4-6 mg / mL.

[0009] Furthermore, the method for preparing the modified silica is as follows: (1) Disperse silica in Tris-HCl buffer, sonicate for 20-40 min, add dopamine hydrochloride, mix evenly and continue sonication for 10-20 min, stir and react at room temperature for 20-28 h, centrifuge, wash, dry, grind and sieve to obtain polydopamine modified silica; (2) Disperse polydopamine-modified silica, phosphorus oxychloride and triethylamine in tetrahydrofuran, sonicate for 1-2 hours, then add carboxymethyl cellulose, raise the temperature to 35-45℃ under stirring, react for 20-28 hours, and then centrifuge, wash, dry, grind and sieve to obtain the product.

[0010] First, silica is ultrasonically dispersed in Tris-HCl buffer to form a uniform dispersion system. Upon addition of dopamine hydrochloride, an oxidative self-polymerization reaction occurs, forming polydopamine, which is deposited on the silica surface. Polydopamine, rich in catechol and amino groups, can firmly bind to silica through hydrogen bonding and π-π stacking, achieving polydopamine modification of silica. Then, phosphorus oxychloride is used as a phosphorylation agent to esterify or amidate the hydroxyl or amino groups on the polydopamine, introducing phosphoryl groups. This process further functionalizes the silica surface, forming an active intermediate. After adding carboxymethyl cellulose, the carboxyl or hydroxyl groups on its molecular chain undergo a condensation reaction with the phosphoryl groups, thus covalently grafting carboxymethyl cellulose onto the polydopamine-modified silica surface, ultimately yielding polydopamine / carboxymethyl cellulose-modified silica.

[0011] Further, in step (1), the mass ratio of silica to dopamine hydrochloride is 1:2-2.5, and the amount of silica added in the Tris-HCl buffer is 0.2-0.3 mg / mL; in step (2), the mass ratio of polydopamine-modified silica, phosphorus oxychloride, triethylamine, and carboxymethyl cellulose is 1:0.6-0.8:0.3-0.4:1.2-1.5, and the amount of polydopamine-modified silica added in tetrahydrofuran is 0.01-0.015 g / mL.

[0012] Further, the dispersant is one or more of polyvinyl alcohol, hydroxyethyl cellulose, and hydroxypropyl methyl cellulose; the nucleating agent is polyethylene wax; the particle size regulator is one or more of activated calcium phosphate, sodium dodecylbenzene sulfonate, and calcium carbonate; the initiator is one or more of benzoyl peroxide, tert-butyl peroxyacetate, di-tert-butyl peroxide, and tert-butyl perethylhexanoate; and the foaming agent is one or more of n-pentane, isopentane, and neopentane.

[0013] This invention also provides a method for preparing lightweight, high-strength expandable polystyrene material, comprising the following steps: mixing deionized water and dispersant evenly, then adding styrene and composite filler sequentially, stirring for 30-50 minutes, raising the temperature to 40-60°C, then adding nucleating agent and initiator, mixing evenly, and continuing to raise the temperature to 88-92°C, stirring for 4.5-6.5 hours, adding particle size regulator and foaming agent and continuing to stir, raising the temperature to 120-124°C, reacting for 3-5 hours, and discharging after cooling to obtain the final product.

[0014] The present invention has the following beneficial effects: In the preparation process of polystyrene materials, this invention introduces raw materials such as styrene, dispersant, composite filler, and foaming agent, and in particular, uses a composite filler prepared by mixing maleic anhydride copolymer sulfonate modified graphene with polydopamine / carboxymethyl cellulose modified silica, which can significantly improve the mechanical properties, thermal stability and flame retardant properties of the material.

[0015] (1) The introduction of composite fillers significantly improves the mechanical properties of polystyrene matrix. Maleic anhydride copolymer sulfonate modified graphene introduces unsaturated double bonds on the graphene surface, which can covalently bond with the polystyrene chains formed during styrene polymerization, effectively preventing filler agglomeration and forming a strong interfacial bond. The modified graphene can form a denser reinforcing network in the polystyrene matrix. When the material is subjected to external force, the graphene sheets can efficiently transfer and disperse stress through their rigid skeleton, avoiding stress concentration in local weak areas. This load transfer capability allows the polystyrene material to maintain high mechanical strength after foaming. At the same time, polydopamine / carboxymethyl cellulose modified silica binds to the polystyrene matrix through physical entanglement and hydrogen bonding. The rigid particles of silica can hinder molecular chain slippage, thereby improving the mechanical properties of the material.

[0016] (2) Composite fillers significantly improve the thermal stability and flame retardant properties of the material. The layered structure of graphene can effectively block the diffusion of heat and oxygen, delaying the thermal degradation of polystyrene molecular chains. The sulfonic acid groups in maleic anhydride copolymer sulfonate can promote the formation of a char layer at high temperatures, further inhibiting the combustion process. The addition of silica reduces the heat release rate of the material through endothermic effect and physical barrier effect. In addition, the carbonization products of polydopamine and the carbon-containing substances generated by the decomposition of carboxymethyl cellulose can form a dense char layer on the material surface, synergistically improving the flame retardant properties. This multi-scale flame retardant mechanism enables the material to maintain structural integrity under high temperature environment, making it suitable for fields with high fire resistance requirements such as building insulation.

[0017] (3) Surface modification of the composite filler significantly improved its compatibility with the polystyrene matrix. The hydrophobic segments in the maleic anhydride copolymer sulfonate are compatible with polystyrene, while the hydrophilic sulfonic acid groups prevent graphene sheets from agglomerating through electrostatic repulsion, ensuring uniform dispersion during aqueous suspension polymerization. Polydopamine / carboxymethyl cellulose modified silica achieves stable dispersion of silica in the aqueous phase through the adhesion of polydopamine and the steric hindrance effect of carboxymethyl cellulose. This good dispersibility ensures uniform distribution of the filler during polymerization, avoids local stress concentration, and further improves the mechanical properties of the composite material.

[0018] Furthermore, maleic anhydride copolymer sulfonate-modified graphene can act as a heterogeneous nucleating agent, lowering the critical nucleation energy barrier of the blowing agent and promoting the uniform formation of bubble nuclei. The two-dimensional structure of graphene sheets can hinder cell coalescence and stabilize cell walls, thereby forming a small and uniformly distributed closed-cell structure. Polydopamine / carboxymethyl cellulose-modified silica interacts with the blowing agent through abundant polar groups on its surface, regulating the gas diffusion rate and preventing cell collapse or over-expansion. This dual regulation mechanism results in a narrower cell diameter distribution and higher porosity, thus maintaining excellent overall performance while reducing density. Detailed Implementation

[0019] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the embodiments of this application. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0020] Styrene-maleic anhydride copolymer, brand name SMA-20H, active ingredient content 99%, purchased from Guangzhou Shanshan New Material Technology Co., Ltd.; graphene, mesh size 2000, fixed carbon content 99%, purchased from Jinan Yuanhai Chemical Co., Ltd.; silica, model TH-1300, active ingredient content 99.6%, purchased from Shandong Wanhua Tianhe New Material Co., Ltd.; carboxymethyl cellulose, density 1.125 g / mL, item number 684954, purchased from Jinan Mingjiang Chemical Co., Ltd.; polyvinyl alcohol, brand name 1799, content ≥99%, purchased from Nantong Changchen Chemical Co., Ltd.; polyethylene wax, model Q-18PE wax, active ingredient content 99%, brand Xindongyi; hydroxyethyl cellulose, density 0.75 g / mL at 25℃, pH (20 g / L, 25℃): 5.0-8.0, brand Nengju Chemical. All raw materials used in the following examples are commercially available products.

[0021] Example 1

[0022] A lightweight, high-strength expandable polystyrene material, comprising the following components by weight: 95 parts styrene, 220 parts deionized water, 0.5 parts dispersant, 2 parts nucleating agent, 0.4 parts initiator, 0.4 parts particle size modifier, 5 parts foaming agent, and 5 parts composite filler; the composite filler is prepared by mixing modified graphene and modified silica in a mass ratio of 10:2; the dispersant is prepared by mixing equal masses of polyvinyl alcohol and hydroxyethyl cellulose; the nucleating agent is polyethylene wax; the particle size modifier is calcium carbonate; the initiator is benzoyl peroxide; and the foaming agent is n-pentane. The method for preparing the modified graphene is as follows: S1. Under stirring at 160 rpm, styrene-maleic anhydride copolymer was dissolved in N,N-dimethylformamide, and chlorosulfonic acid was added dropwise. The addition was completed in 40 min, the temperature was raised to 80 °C, and the reaction was carried out for 3 h. After natural cooling to 50 °C, N,N-dimethylformamide was removed by vacuum distillation, and sodium hydroxide ethanol solution was added dropwise. The reaction was carried out for 1.5 h, filtered, and the filter residue was washed three times with ethanol and dried at 100 °C to constant weight to obtain modified styrene-maleic anhydride copolymer. The mass ratio of styrene-maleic anhydride copolymer, chlorosulfonic acid, and sodium hydroxide ethanol solution was 10:5:40, the mass-volume ratio of styrene-maleic anhydride copolymer to N,N-dimethylformamide was 0.17 g / mL, and the mass percentage of sodium hydroxide in the sodium hydroxide ethanol solution was 7.5%. S2. 98% concentrated sulfuric acid and nitric acid were mixed evenly under ice-water bath conditions to obtain a mixed acid. Graphene was then added, and the mixture was ultrasonically treated at 35°C for 5 hours. After diluting 10 times with deionized water, the mixture was filtered to obtain a filter residue. The residue was then repeatedly washed until the pH value reached 7, and then freeze-dried under vacuum for 24 hours to obtain activated graphene. Modified styrene-maleic anhydride copolymer, activated graphene, and N,N-dimethylformamide were mixed evenly and ultrasonically treated for 40 minutes at a power of 200W and a frequency of 25kHz, followed by ultrasonic treatment at 160rpm. The temperature was raised to 65℃ under stirring and reacted for 2.5 h. After natural cooling to room temperature, the mixture was filtered through a 0.45 μm microporous membrane and washed three times with deionized water. It was then freeze-dried under vacuum for 24 h to obtain the final product. The volume ratio of concentrated sulfuric acid to nitric acid was 3:1, the mass-to-volume ratio of graphene to the mixed acid was 5 mg / mL, the mass ratio of modified styrene-maleic anhydride copolymer to activated graphene was 1:0.6, and the mass-to-volume ratio of modified styrene-maleic anhydride copolymer to N,N-dimethylformamide was 0.02 g / mL. The grafting rate of the modified graphene was determined to be 15.7% using thermogravimetric analysis. The method for preparing the modified silica is as follows: (1) Silica was dispersed in Tris-HCl buffer (pH 7.4), sonicated for 30 min, then dopamine hydrochloride was added, mixed evenly and sonicated for another 15 min, stirred at room temperature and 160 rpm for 24 h, centrifuged to obtain precipitate, washed three times with deionized water, freeze-dried under vacuum for 24 h, ground and passed through an 800-mesh sieve to obtain polydopamine modified silica; wherein, the mass ratio of silica to dopamine hydrochloride was 1:2.3, the amount of silica added in Tris-HCl buffer was 0.25 mg / mL, the ultrasonic power of the sonication was 150 W, the ultrasonic frequency was 30 kHz, the centrifugation speed was 10000 r / min, and the centrifugation time was 8 min; (2) Polydopamine-modified silica, phosphorus oxychloride, and triethylamine were dispersed in tetrahydrofuran and ultrasonically treated for 1.5 h. Then, carboxymethyl cellulose was added, and the temperature was raised to 40 °C under stirring at 160 rpm for 24 h. The precipitate was obtained by centrifugation, and the precipitate was washed three times with deionized water by centrifugation. It was then freeze-dried under vacuum for 24 h, ground, and passed through an 800-mesh sieve to obtain the final product. The mass ratio of polydopamine-modified silica, phosphorus oxychloride, triethylamine, and carboxymethyl cellulose was 1:0.7:0.35:1.3, and the amount of polydopamine-modified silica added to tetrahydrofuran was 0.012 g / mL. The ultrasonic power of the ultrasonic treatment was 200 W, the ultrasonic frequency was 30 kHz, the centrifugation speed was 8000 r / min, and the centrifugation time was 8 min. The grafting rate of the modified silica was 12.8% as determined by thermogravimetric analysis.

[0023] A method for preparing a lightweight, high-strength expandable polystyrene material includes the following steps: Deionized water and a dispersant are mixed evenly, then styrene and a composite filler are added sequentially, and the mixture is stirred for 40 minutes. The temperature is then raised to 50°C, followed by the addition of a nucleating agent and an initiator. After mixing evenly, the temperature is further raised to 90°C and stirred for 5.5 hours. A particle size regulator and a foaming agent are added and stirring is continued, with the temperature raised to 122°C. The mixture is reacted at 0.5 MPa pressure for 4 hours, then naturally cooled to 40°C. After washing, dehydration, and drying, the polystyrene material is obtained.

[0024] Example 2

[0025] A lightweight, high-strength expandable polystyrene material and its preparation method are disclosed. The material is prepared according to the method described in Example 1, except that the composite filler is in parts by weight of 3 parts.

[0026] Example 3

[0027] A lightweight, high-strength expandable polystyrene material and its preparation method are disclosed. The material is prepared according to the method described in Example 1, except that the composite filler is in parts by weight of 6.

[0028] Example 4

[0029] A lightweight, high-strength expandable polystyrene material and its preparation method are disclosed. The material is prepared according to the method described in Example 1, except that the mass ratio of modified graphene to modified silicon dioxide is 10:1.

[0030] Example 5

[0031] A lightweight, high-strength expandable polystyrene material and its preparation method are prepared according to the method described in Example 1, with the difference being: The method for preparing the modified graphene is as follows: S1. Under stirring at 160 rpm, styrene-maleic anhydride copolymer was dissolved in N,N-dimethylformamide, and chlorosulfonic acid was added dropwise. The addition was completed in 40 min, the temperature was raised to 80 °C, and the reaction was carried out for 3 h. After natural cooling to 50 °C, N,N-dimethylformamide was removed by vacuum distillation, and sodium hydroxide ethanol solution was added dropwise. The reaction was carried out for 1.5 h, filtered, and the filter residue was washed three times with ethanol and dried at 100 °C to constant weight to obtain modified styrene-maleic anhydride copolymer. The mass ratio of styrene-maleic anhydride copolymer, chlorosulfonic acid, and sodium hydroxide ethanol solution was 10:4:30, the mass-volume ratio of styrene-maleic anhydride copolymer to N,N-dimethylformamide was 0.17 g / mL, and the mass percentage of sodium hydroxide in the sodium hydroxide ethanol solution was 5%. S2. 98% concentrated sulfuric acid and nitric acid were mixed evenly under ice-water bath conditions to obtain a mixed acid. Graphene was then added, and the mixture was ultrasonically treated at 35°C for 5 hours. After diluting 10 times with deionized water, the mixture was filtered to obtain a filter residue. The residue was then repeatedly washed until the pH value reached 7, and then freeze-dried under vacuum for 24 hours to obtain activated graphene. Modified styrene-maleic anhydride copolymer, activated graphene, and N,N-dimethylformamide were mixed evenly and ultrasonically treated for 40 minutes at a power of 200W and a frequency of 25kHz, followed by ultrasonic treatment at 160rpm. The temperature was raised to 65℃ under stirring and reacted for 2.5 h. After natural cooling to room temperature, the mixture was filtered through a 0.45 μm microporous membrane and washed three times with deionized water. It was then freeze-dried under vacuum for 24 h to obtain the final product. The volume ratio of concentrated sulfuric acid to nitric acid was 3:1, the mass-to-volume ratio of graphene to the mixed acid was 5 mg / mL, the mass ratio of modified styrene-maleic anhydride copolymer to activated graphene was 1:0.7, and the mass-to-volume ratio of modified styrene-maleic anhydride copolymer to N,N-dimethylformamide was 0.02 g / mL. The grafting rate of the modified graphene was determined to be 13.0% using thermogravimetric analysis.

[0032] Example 6

[0033] A lightweight, high-strength expandable polystyrene material and its preparation method are prepared according to the method described in Example 1, with the difference being: The method for preparing the modified silica is as follows: (1) Silica was dispersed in Tris-HCl buffer (pH 7.4), sonicated for 30 min, then dopamine hydrochloride was added, mixed evenly and sonicated for another 15 min, stirred at room temperature and 160 rpm for 24 h, centrifuged to obtain precipitate, washed three times with deionized water, freeze-dried under vacuum for 24 h, ground and passed through an 800-mesh sieve to obtain polydopamine modified silica; wherein, the mass ratio of silica to dopamine hydrochloride was 1:2, the amount of silica added in Tris-HCl buffer was 0.25 mg / mL, the ultrasonic power of the sonication was 150 W, the ultrasonic frequency was 30 kHz, the centrifugation speed was 10000 r / min, and the centrifugation time was 8 min; (2) Polydopamine-modified silica, phosphorus oxychloride, and triethylamine were dispersed in tetrahydrofuran and ultrasonically treated for 1.5 h. Then, carboxymethyl cellulose was added, and the temperature was raised to 40 °C under stirring at 160 rpm for 24 h. The precipitate was obtained by centrifugation, and the precipitate was washed three times with deionized water by centrifugation. It was then freeze-dried under vacuum for 24 h, ground, and passed through an 800-mesh sieve to obtain the final product. The mass ratio of polydopamine-modified silica, phosphorus oxychloride, triethylamine, and carboxymethyl cellulose was 1:0.6:0.3:1.2, and the amount of polydopamine-modified silica added to tetrahydrofuran was 0.012 g / mL. The ultrasonic power of the ultrasonic treatment was 200 W, the ultrasonic frequency was 30 kHz, the centrifugation speed was 8000 r / min, and the centrifugation time was 8 min. The grafting rate of the modified silica was 10.1% as determined by thermogravimetric analysis.

[0034] Comparative Example 1

[0035] A lightweight, high-strength expandable polystyrene material and its preparation method are disclosed. The material is prepared according to the method described in Example 1, except that the composite filler is prepared by mixing graphene and modified silica prepared in Example 1, with a mass ratio of graphene to modified silica of 10:2.

[0036] Comparative Example 2

[0037] A lightweight, high-strength expandable polystyrene material and its preparation method are disclosed. The material is prepared according to the method described in Example 1, except that the composite filler is prepared by mixing modified graphene and silicon dioxide prepared in Example 1, with a mass ratio of modified graphene to silicon dioxide of 10:2.

[0038] Comparative Example 3

[0039] A lightweight, high-strength expandable polystyrene material and its preparation method are disclosed. The method described in Example 1 is followed, except that the composite filler is prepared by mixing graphene and silicon dioxide, with a mass ratio of graphene to silicon dioxide of 10:2.

[0040] The water dispersibility of the modified graphene, modified silica, and commercially available graphene and silica prepared in Examples 1 and 5-6 was tested. First, modified graphene and modified silica aqueous dispersions with excess of different processing methods were prepared. After ultrasonic treatment for 30 min, they were centrifuged in a centrifuge at a speed of 5000 r / min for 5 min. The resulting supernatant was dried to constant weight, and the mass difference before and after drying was measured. The mass concentration of modified graphene and modified silica in the supernatant was calculated (considered as the maximum mass concentration). The test was repeated three times, and the average value was taken. The results showed that the maximum mass concentration of the modified graphene aqueous dispersion prepared in Example 1 was 0.35 mg / mL, the maximum mass concentration of the modified silica aqueous dispersion prepared in Example 1 was 0.12 mg / mL, the maximum mass concentration of the modified graphene aqueous dispersion prepared in Example 5 was 0.27 mg / mL, and the maximum mass concentration of the modified silica aqueous dispersion prepared in Example 6 was 0.10 mg / mL. In contrast, the maximum mass concentration of commercially available graphene aqueous dispersions was 0.07 mg / mL, and the maximum mass concentration of commercially available silica aqueous dispersions was 0.02 mg / mL. These results indicate that modifying graphene and silica using the processing technology provided in this application can significantly improve the water dispersibility of inorganic fillers, prevent agglomeration, ensure uniform distribution of inorganic fillers in the polystyrene matrix, and effectively exert the nano-reinforcing effect.

[0041] Foaming tests were conducted on the samples prepared in Examples 1-6 and Comparative Examples 1-3. After foaming, the samples were cooled and dried, and the volumes before and after foaming were measured. The foaming ratio was calculated using the formula: Foaming ratio = V2 / V1, where V1 is the volume of the sample before foaming and V2 is the volume of the sample after foaming. Density testing was performed using the specific gravity bottle method. In accordance with GB / T6594.2-2003 "Plastics Polystyrene (PS) Molding and Extrusion Materials Part 2: Specimen Preparation and Performance Determination", relevant performance tests were conducted on the lightweight, high-strength expandable polystyrene material compression molded specimens prepared in Examples 1-6 and Comparative Examples 1-3. The oxygen index test was conducted according to GB / T2406.2-2009 "Determination of Combustion Behavior by Oxygen Index Method for Plastics - Part 2: Room Temperature Test"; the thermal stability test was conducted according to GB / T8811-2008 "Test Method for Dimensional Stability of Rigid Foamed Plastics", testing the dimensional change rate of the specimens before and after heat treatment. The heat treatment conditions were: the specimens were placed at 125℃ for 7 days; the compressive strength test was conducted according to GB / T8813-2020 "Determination of Compressive Properties of Rigid Foamed Plastics"; the impact strength test was conducted according to GB / T1843-2008 "Determination of Impact Strength of Plastic Cantilever Beam", with notch type A; all the above tests were repeated three times and the average value was taken. The test results are shown in Table 1.

[0042] The performance data from Examples 1-6 and Comparative Examples 1-3 show that the surface modification of the inorganic filler and the synergistic effect of multiple components successfully improved the flame retardancy, mechanical properties, and thermal stability. However, the unmodified filler exhibited significant performance degradation due to poor dispersibility and weak interfacial bonding, with Comparative Example 3, where neither component was modified, showing the worst performance. The flame retardancy data also indicate that, compared to Example 1, the graphene in Comparative Example 1 was not sulfonated and lacked active groups to promote charring, resulting in limited flame retardant effect. The silica in Comparative Example 2 was not functionalized and could not form an effective char layer, relying solely on physical endothermic processes. In Comparative Example 3, neither component was modified, leading to poor compatibility between the inorganic composite filler and the polymer matrix, uneven dispersion, and the worst flame retardant performance. The compressive strength and impact strength data show that, compared with Example 1, the unmodified graphene in Comparative Example 1 is prone to agglomeration, has weak interfacial bonding, and low stress transfer efficiency; the unmodified silica in Comparative Example 2 has poor compatibility with the polymer matrix and is prone to forming defects; the inorganic composite filler in Comparative Example 3 exhibits severe agglomeration, and the most significant decrease in mechanical properties is due to localized stress concentration. The dimensional change rate data shows that, compared with Example 1, the composite fillers provided in Comparative Examples 1-3 cannot effectively limit the thermal expansion of the polymer matrix, resulting in poor dimensional stability at high temperatures.

[0043] Table 1. Test results of relevant properties of lightweight, high-strength expandable polystyrene materials. ; Although embodiments of this application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A lightweight, high-strength expandable polystyrene material, characterized in that, The product comprises, by weight, the following components: 90-100 parts styrene, 200-250 parts deionized water, 0.3-0.6 parts dispersant, 1.5-2.5 parts nucleating agent, 0.2-0.6 parts initiator, 0.2-0.5 parts particle size modifier, 4-7 parts foaming agent, and 3-6 parts composite filler; wherein the composite filler is prepared by mixing modified graphene and modified silica, with a mass ratio of modified graphene to modified silica of 10:1-3. The modified graphene is prepared as follows: S1. Under stirring conditions, styrene-maleic anhydride copolymer is dissolved in N,N-dimethylformamide, chlorosulfonic acid is added dropwise, the temperature is raised to 70-90℃, the reaction is carried out for 2-4 hours, the mixture is cooled and distilled under reduced pressure, sodium hydroxide ethanol solution is added dropwise, the reaction is carried out for 1-2 hours, and the modified styrene-maleic anhydride copolymer is obtained after filtration, washing and drying. S2. Activate graphene by acid treatment. Mix the modified styrene-maleic anhydride copolymer, the activated graphene, and N,N-dimethylformamide evenly, sonicate for 30-50 min, raise the temperature to 55-75℃ under stirring, react for 2-3 h, cool to room temperature, filter, wash, and dry to obtain the final product. The method for preparing the modified silica is as follows: (1) Disperse silica in Tris-HCl buffer, sonicate for 20-40 min, add dopamine hydrochloride, mix evenly and continue sonication for 10-20 min, stir and react at room temperature for 20-28 h, centrifuge, wash, dry, grind and sieve to obtain polydopamine modified silica; (2) Disperse polydopamine-modified silica, phosphorus oxychloride and triethylamine in tetrahydrofuran, sonicate for 1-2 hours, then add carboxymethyl cellulose, raise the temperature to 35-45℃ under stirring, react for 20-28 hours, and then centrifuge, wash, dry, grind and sieve to obtain the product.

2. The lightweight, high-strength expandable polystyrene material according to claim 1, characterized in that, In step S1, the mass ratio of styrene-maleic anhydride copolymer, chlorosulfonic acid, and sodium hydroxide ethanol solution is 10:4-7:30-50, the mass-volume ratio of styrene-maleic anhydride copolymer to N,N-dimethylformamide is 0.15-0.20 g / mL, and the mass percentage of sodium hydroxide in the sodium hydroxide ethanol solution is 5-10%.

3. The lightweight, high-strength expandable polystyrene material according to claim 1, characterized in that, In step S2, the mass ratio of the modified styrene-maleic anhydride copolymer to the activated graphene is 1:0.5-0.7, and the mass-to-volume ratio of the modified styrene-maleic anhydride copolymer to N,N-dimethylformamide is 0.01-0.03 g / mL.

4. The lightweight, high-strength expandable polystyrene material according to claim 1, characterized in that, The specific steps of the acid treatment in step S2 are as follows: concentrated sulfuric acid and nitric acid are mixed evenly under ice-water bath conditions to obtain a mixed acid, then graphene is added, and ultrasonic treatment is carried out at 30-35℃ for 4.5-5.5h, followed by dilution, filtration, washing and drying.

5. The lightweight, high-strength expandable polystyrene material according to claim 4, characterized in that, The volume ratio of concentrated sulfuric acid to nitric acid is 2.5-3.5:1, and the mass-volume ratio of graphene to the mixed acid is 4-6 mg / mL.

6. The lightweight, high-strength expandable polystyrene material according to claim 1, characterized in that, The mass ratio of silica to dopamine hydrochloride in step (1) is 1:2-2.5, and the amount of silica added to the Tris-HCl buffer is 0.2-0.3 mg / mL.

7. The lightweight, high-strength expandable polystyrene material according to claim 1, characterized in that, In step (2), the mass ratio of polydopamine-modified silica, phosphorus oxychloride, triethylamine, and carboxymethyl cellulose is 1:0.6-0.8:0.3-0.4:1.2-1.5, and the amount of polydopamine-modified silica added to tetrahydrofuran is 0.01-0.015 g / mL.

8. The lightweight, high-strength expandable polystyrene material according to claim 1, characterized in that, The dispersant is one or more of polyvinyl alcohol, hydroxyethyl cellulose, and hydroxypropyl methyl cellulose; the nucleating agent is polyethylene wax; the particle size regulator is one or more of activated calcium phosphate, sodium dodecylbenzene sulfonate, and calcium carbonate; the initiator is one or more of benzoyl peroxide, tert-butyl peroxyacetate, di-tert-butyl peroxide, and tert-butyl perethylhexanoate; and the foaming agent is one or more of n-pentane, isopentane, and neopentane.

9. The method for preparing lightweight, high-strength expandable polystyrene material according to any one of claims 1-8, characterized in that, The process includes the following steps: Mix deionized water and dispersant evenly, then add styrene and composite filler in sequence, stir for 30-50 minutes, raise the temperature to 40-60℃, then add nucleating agent and initiator, mix evenly, continue to raise the temperature to 88-92℃, stir for 4.5-6.5 hours, add particle size regulator and foaming agent and continue stirring, raise the temperature to 120-124℃, react for 3-5 hours, cool down and discharge the material to obtain the final product.