Graphene reinforced brominated epoxy resin composite material and preparation method thereof

Abstract

The invention relates to the technical field of composite materials, in particular to a graphene reinforced brominated epoxy resin composite material and a preparation method thereof. The preparation method of the graphene-reinforced brominated epoxy resin composite material comprises the following steps: S1, preparing brominated epoxy resin; S2, preparing modified brominated epoxy resin; S3, preparing functionalized graphene; and S4, curing to obtain the graphene-reinforced brominated epoxy resin composite material. The graphene-reinforced brominated epoxy resin composite material has good mechanical properties, flame retardancy and water resistance, and a certain foundation is laid for subsequent application to the field of copper-clad plates.

Description

Technical Field

[0001] The present invention relates to the technical field of composite materials, and in particular to a graphene-reinforced brominated epoxy resin composite material and a preparation method thereof. Background Art

[0002] Graphene is a two-dimensional honeycomb lattice structure formed by a single layer of carbon atoms hybridized in sp². It is only one atomic layer thick and is one of the thinnest and strongest known materials. It has excellent electrical, thermal, and mechanical properties and chemical stability, and is widely used in electronic devices, energy storage, composite materials and other fields.

[0003] Brominated epoxy resin is a new epoxy resin material that has seen rapid growth in recent years. It is an epoxy resin derivative that modifies its properties and uses by introducing bromine atoms into the epoxy resin molecule. Brominated epoxy resin typically exhibits high flame retardancy and heat resistance and is widely used in the manufacturing of electronics, electrical appliances, automobiles, aviation, and other fields.

[0004] Patent document CN107057283B discloses a carbon fiber-reinforced resin-based composite material and its preparation method. Graphene with active functional groups on its surface is prepared using a modified Hummers method. The addition of carbon nanotubes creates a synergistic effect with the graphene, significantly improving the dispersion of the nanoscale fillers graphene and carbon nanotubes in the resin matrix. The presence of graphene and carbon nanotubes also enhances the interfacial bonding between the carbon fibers and the resin matrix. Brominated epoxy resin can improve the flame retardancy of the composite material, while cyanate esters have high strength and reactivity, enhancing the interfacial bonding between the epoxy resin and the carbon fibers. Cyanate esters also serve as a curing agent for the brominated epoxy resin. This invention offers advantages such as a simple process, environmental friendliness, and excellent composite material performance. However, current brominated epoxy resin composites still suffer from issues such as poor flame retardancy and water resistance. Summary of the Invention

[0005] In view of this, the object of the present invention is to provide a graphene-reinforced brominated epoxy resin composite material and a preparation method thereof, so as to provide a brominated epoxy resin composite material with good flame retardancy and waterproof and water resistance.

[0006] Based on the above objectives, the present invention provides a method for preparing a graphene-reinforced brominated epoxy resin composite material, comprising the following steps: S1: Preparation of brominated epoxy resin: Tetrabromobisphenol A, epichlorohydrin, and tetramethylammonium chloride are reacted at 70-80°C for 2-3 hours. After the reaction is completed, the mixture is distilled under reduced pressure. Toluene and sodium hydroxide solution are then added, and the mixture is reacted at 70-80°C for 1-2 hours. The mixture is then distilled to obtain an oligomer. The oligomer is then mixed with tetrabromobisphenol A, and triphenylphosphine is added. The mixture is reacted at 120-130°C for 3-4 hours to obtain a brominated epoxy resin. S2: preparing a modified brominated epoxy resin: swelling chitosan in N,N-dimethylacetamide, dissolving brominated epoxy resin in N,N-dimethylacetamide, and adding the mixture to a reaction system; and simultaneously adding diphenylmethane-4,4'-diisocyanate to the reaction system. The mixture is reacted at 100-120° C. for 20-24 hours, and rotary evaporated to obtain a modified brominated epoxy resin. S3 Preparation of functionalized graphene: Orthophosphoric acid is added to natural graphite, stirred and dispersed uniformly, followed by slow addition of nitric acid, ultrasonic treatment, and reaction at 90-100°C for 2-3 hours. Chitosan is then added and dissolved, followed by addition of aluminum phosphate, and heating at 95-100°C for 2-3 hours. The mixture is cooled, filtered, and dried to obtain functionalized graphene. S4: adding the functionalized graphene to acetone for ultrasonic dispersion, then adding the modified brominated epoxy resin, stirring and ultrasonically dispersing for 30 minutes, volatilizing to obtain a dispersion, preheating 4,4-diaminodiphenylmethane, then adding it to the dispersion, stirring evenly, casting it into a polytetrafluoroethylene mold for curing, and cooling it to obtain a graphene-reinforced brominated epoxy resin composite material; In step S1, the ratio of tetrabromobisphenol A, epichlorohydrin, tetramethylammonium chloride, toluene, and sodium hydroxide solution is 54-60 g: 80-90 g: 0.75-0.9 g: 300-400 mL: 30-35 g; The oligomer, tetrabromobisphenol A, and triphenylphosphine used in step S1 are used in a ratio of 70-100 g: 50-55 g: 0.8-1 g; In step S2, the chitosan, N,N-dimethylacetamide, brominated epoxy resin, and diphenylmethane-4,4'-diisocyanate are used in a ratio of 2-3 g: 240-340 mL: 122-130 g: 13.5-15 g; The usage ratio of orthophosphoric acid, natural graphite, nitric acid, chitosan, and aluminum phosphate in step S3 is 20-30 mL: 5-10 g: 60-100 mL: 5-7 g: 3-5 g; The amount ratio of the functionalized graphene, acetone, modified brominated epoxy resin, and 4,4-diaminodiphenylmethane in step S4 is 5-6 g: 100-200 mL: 100-120 g: 25-30 g.

[0007] Preferably, the concentration of the sodium hydroxide solution in step S1 is 30%.

[0008] Preferably, the swelling in step S2 is performed at 80° C. for 24 h.

[0009] Preferably, the concentration of nitric acid in step S3 is 69%.

[0010] Preferably, the volatilization in step S4 is carried out in a forced air oven at 60° C. for 24 h.

[0011] Preferably, the preheating in step S4 is preheating at 110° C. for 20 minutes.

[0012] Preferably, the curing in step S4 is first performed at 100° C. for 2 hours, and then heated to 150° C. and kept warm for 4 hours.

[0013] Furthermore, the present invention also provides a graphene-reinforced brominated epoxy resin composite material.

[0014] Beneficial effects of the present invention: The graphene-reinforced brominated epoxy resin composite material of the present invention has good mechanical properties, flame retardant properties, and waterproof and water-resistant properties.

[0015] The graphene-reinforced brominated epoxy resin composite material of the present invention, after the brominated epoxy resin is modified with chitosan, has an improved overall cross-linking density and a denser waterproof barrier, so that the composite material has certain improvements in mechanical properties, flame retardant properties, and waterproof and water-resistant properties.

[0016] The graphene-reinforced brominated epoxy resin composite material of the present invention adopts a method of loading chitosan and aluminum phosphate on graphene, thereby making the composite material have better mechanical strength, flame retardancy and waterproof ability. DETAILED DESCRIPTION

[0017] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to specific embodiments.

[0018] Example 1: A graphene-reinforced brominated epoxy resin composite material, the specific preparation steps are as follows: (1) Add 54 g of tetrabromobisphenol A, 80 g of epichlorohydrin, and 0.75 g of tetramethylammonium chloride to a four-necked glass bottle in sequence, and react at 70°C for 2 h. After the reaction is completed, distill under reduced pressure, then add 300 mL of toluene solvent and 30 g of 30% sodium hydroxide solution, and react at 70°C for 1 h. Then put the reaction solution into a separatory funnel, let it stand and separate the layers, and distill under reduced pressure to obtain an oligomer. Then, mix 70 g of the oligomer with 50 g of tetrabromobisphenol A, add 0.8 g of triphenylphosphine, and react at 120°C for 3 h to obtain a brominated epoxy resin. (2) 2 g of chitosan was placed in 40 mL of N, N-dimethylacetamide and swelled at 80 °C for 24 h. Subsequently, 122 g of brominated epoxy resin was dissolved in 200 mL of N, N-dimethylacetamide and added to the reaction system. At the same time, 13.5 g of diphenylmethane-4,4'-diisocyanate was added to the reaction system. The reaction was carried out at 100 °C for 20 h, and the modified brominated epoxy resin was obtained by rotary evaporation. (3) Add 20 mL of orthophosphoric acid to 5 g of natural graphite and stir to disperse evenly. Then slowly add 60 mL of 69% nitric acid. Ultrasonicate the mixture for 30 min and react at 90 °C for 2 h. Then add 5 g of chitosan. After it dissolves, add 3 g of aluminum phosphate and continue heating at 95 °C for 2 h. Cool, filter with 0.45 μm filter paper, and dry at 60 °C to obtain functionalized graphene. (4) 5 g of functionalized graphene was added to 100 mL of acetone solvent and ultrasonically dispersed. Then, 100 g of modified brominated epoxy resin was added and stirred ultrasonically for 30 min. Then, the mixture was volatilized in a blast oven at 60 °C for 24 h to obtain a dispersion. 25 g of 4,4-diaminodiphenylmethane was preheated at 110 °C for 20 min and then added to the dispersion. The mixture was stirred evenly and cast into a polytetrafluoroethylene mold for curing. The mixture was first cured at 100 °C for 2 h, then heated to 150 °C and kept at this temperature for 4 h for curing. The mixture was cooled to obtain a graphene-reinforced brominated epoxy resin composite material.

[0019] Example 2: A graphene-reinforced brominated epoxy resin composite material, the specific preparation steps are as follows: (1) Add 57g of tetrabromobisphenol A, 85g of epichlorohydrin, and 0.8g of tetramethylammonium chloride to a four-necked glass bottle in sequence, and react at 75°C for 2h. After the reaction is completed, distill under reduced pressure, then add 350mL of toluene solvent and 33g of 30% sodium hydroxide solution, and react at 75°C for 2h. Then put the reaction solution into a separating funnel, let it stand for stratification, and distill under reduced pressure to obtain an oligomer. Then, mix 85g of the oligomer with 53g of tetrabromobisphenol A, add 0.9g of triphenylphosphine, and react at 125°C for 4h to obtain a brominated epoxy resin. (2) 2.5 g of chitosan was placed in 40 mL of N, N-dimethylacetamide and swelled at 80 °C for 24 h. Subsequently, 126 g of brominated epoxy resin was dissolved in 250 mL of N, N-dimethylacetamide and added to the reaction system. At the same time, 14 g of diphenylmethane-4,4'-diisocyanate was added to the reaction system. The mixture was reacted at 110 °C for 22 h and the modified brominated epoxy resin was obtained by rotary evaporation. (3) Add 25 mL of orthophosphoric acid to 8 g of natural graphite and stir to disperse evenly. Then slowly add 80 mL of 69% nitric acid. Ultrasonicate the mixture for 30 min and react at 95 °C for 3 h. Then add 6 g of chitosan. After it dissolves, add 4 g of aluminum phosphate and continue heating at 98 °C for 3 h. Cool, filter with 0.45 μm filter paper, and dry at 60 °C to obtain functionalized graphene. (4) 5.5 g of functionalized graphene was added to 150 mL of acetone solvent for ultrasonic dispersion, and then 110 g of modified brominated epoxy resin was added and stirred for 30 min. Then, the mixture was evaporated in a blast oven at 60 °C for 24 h to obtain a dispersion. 28 g of 4,4-diaminodiphenylmethane was preheated at 110 °C for 20 min and then added to the dispersion. The mixture was stirred evenly and cast into a polytetrafluoroethylene mold for curing. The mixture was first cured at 100 °C for 2 h, then heated to 150 °C and kept at this temperature for 4 h for curing. The mixture was cooled to obtain a graphene-reinforced brominated epoxy resin composite material.

[0020] Example 3: A graphene-reinforced brominated epoxy resin composite material, the specific preparation steps are as follows: (1) Add 60g of tetrabromobisphenol A, 90g of epichlorohydrin, and 0.9g of tetramethylammonium chloride to a four-necked glass bottle in sequence, and react at 80°C for 3h. After the reaction is completed, distill under reduced pressure, then add 400mL of toluene solvent and 35g of 30% sodium hydroxide solution, and react at 80°C for 2h. Then put the reaction solution into a separatory funnel, let it stand for stratification, and distill under reduced pressure to obtain an oligomer; then mix 100g of the oligomer with 55g of tetrabromobisphenol A, add 1g of triphenylphosphine, and react at 130°C for 4h to obtain a brominated epoxy resin; (2) 3 g of chitosan was placed in 40 mL of N, N-dimethylacetamide and swelled at 80 °C for 24 h. Subsequently, 130 g of brominated epoxy resin was dissolved in 300 mL of N, N-dimethylacetamide and added to the reaction system. At the same time, 15 g of diphenylmethane-4,4'-diisocyanate was added to the reaction system. The mixture was reacted at 120 °C for 24 h and then evaporated to obtain the modified brominated epoxy resin. (3) Add 30 mL of orthophosphoric acid to 10 g of natural graphite and stir to disperse evenly. Then slowly add 100 mL of 69% nitric acid. Ultrasonicate the mixture for 30 min and react at 100 °C for 3 h. Then add 7 g of chitosan. After it dissolves, add 5 g of aluminum phosphate and continue heating at 100 °C for 3 h. Cool, filter with 0.45 μm filter paper, and dry at 60 °C to obtain functionalized graphene. (4) 6 g of functionalized graphene was added to 200 mL of acetone solvent and ultrasonically dispersed. Then, 120 g of modified brominated epoxy resin was added and stirred ultrasonically for 30 min. Then, it was volatilized in a blast oven at 60 °C for 24 h to obtain a dispersion. 30 g of 4,4-diaminodiphenylmethane was preheated at 110 °C for 20 min and then added to the dispersion. The mixture was stirred evenly and cast into a polytetrafluoroethylene mold for curing. First, it was cured at 100 °C for 2 h, then heated to 150 °C and kept at this temperature for 4 h for curing. After cooling, a graphene-reinforced brominated epoxy resin composite material was obtained.

[0021] Comparative Example 1: A brominated epoxy resin composite material, which differs from Example 2 in that the brominated epoxy resin is not modified. The specific preparation steps are as follows: (1) Add 57g of tetrabromobisphenol A, 85g of epichlorohydrin, and 0.8g of tetramethylammonium chloride to a four-necked glass bottle in sequence, and react at 75°C for 2h. After the reaction is completed, distill under reduced pressure, then add 350mL of toluene solvent and 33g of 30% sodium hydroxide solution, and react at 75°C for 2h. Then put the reaction solution into a separating funnel, let it stand for stratification, and distill under reduced pressure to obtain an oligomer. Then, mix 85g of the oligomer with 53g of tetrabromobisphenol A, add 0.9g of triphenylphosphine, and react at 125°C for 4h to obtain a brominated epoxy resin. (2) Add 25 mL of orthophosphoric acid to 8 g of natural graphite and stir to disperse evenly. Then slowly add 80 mL of 69% nitric acid. Ultrasonicate the mixture for 30 min and react at 95 °C for 3 h. Then add 6 g of chitosan. After it dissolves, add 4 g of aluminum phosphate and continue heating at 98 °C for 3 h. Cool, filter with 0.45 μm filter paper, and dry at 60 °C to obtain functionalized graphene. (3) 5.5 g of functionalized graphene was added to 150 mL of acetone solvent for ultrasonic dispersion, and then 110 g of brominated epoxy resin was added and stirred for 30 min. Then, it was volatilized in a blast oven at 60 °C for 24 h to obtain a dispersion. 28 g of 4,4-diaminodiphenylmethane was preheated at 110 °C for 20 min and then added to the dispersion. The mixture was stirred evenly and cast into a polytetrafluoroethylene mold for curing. The mixture was first cured at 100 °C for 2 h, then heated to 150 °C and kept at this temperature for 4 h for curing. The mixture was cooled to obtain a brominated epoxy resin composite material.

[0022] Comparative Example 2: A brominated epoxy resin composite material, which differs from Example 2 in that diphenylmethane-4,4'-diisocyanate is replaced with an equimolar amount of hexamethylene diisocyanate. The specific preparation steps are as follows: (1) Add 57g of tetrabromobisphenol A, 85g of epichlorohydrin, and 0.8g of tetramethylammonium chloride to a four-necked glass bottle in sequence, and react at 75°C for 2h. After the reaction is completed, distill under reduced pressure, then add 350mL of toluene solvent and 33g of 30% sodium hydroxide solution, and react at 75°C for 2h. Then put the reaction solution into a separating funnel, let it stand for stratification, and distill under reduced pressure to obtain an oligomer. Then, mix 85g of the oligomer with 53g of tetrabromobisphenol A, add 0.9g of triphenylphosphine, and react at 125°C for 4h to obtain a brominated epoxy resin. (2) 2.5 g of chitosan was placed in 40 mL of N,N-dimethylacetamide and swelled at 80 °C for 24 h. Subsequently, 126 g of brominated epoxy resin was dissolved in 250 mL of N,N-dimethylacetamide and added to the reaction system. At the same time, 9.4 g of hexamethylene diisocyanate was added to the reaction system. The mixture was reacted at 110 °C for 22 h and then evaporated to obtain the modified brominated epoxy resin. (3) Add 25 mL of orthophosphoric acid to 8 g of natural graphite and stir to disperse evenly. Then slowly add 80 mL of 69% nitric acid. Ultrasonicate the mixture for 30 min and react at 95 °C for 3 h. Then add 6 g of chitosan. After it dissolves, add 4 g of aluminum phosphate and continue heating at 98 °C for 3 h. Cool, filter with 0.45 μm filter paper, and dry at 60 °C to obtain functionalized graphene. (4) 5.5 g of functionalized graphene was added to 150 mL of acetone solvent for ultrasonic dispersion, and then 110 g of modified brominated epoxy resin was added and stirred for 30 min. Then, the mixture was evaporated in a blast oven at 60 °C for 24 h to obtain a dispersion. 28 g of 4,4-diaminodiphenylmethane was preheated at 110 °C for 20 min and then added to the dispersion. The mixture was stirred evenly and cast into a polytetrafluoroethylene mold for curing. The mixture was first cured at 100 °C for 2 h, then heated to 150 °C and kept at this temperature for 4 h for curing. The mixture was cooled to obtain a brominated epoxy resin composite material.

[0023] Comparative Example 3: A brominated epoxy resin composite material, which differs from Example 2 in that the functionalized graphene does not contain chitosan. The specific preparation steps are as follows: (1) Add 57g of tetrabromobisphenol A, 85g of epichlorohydrin, and 0.8g of tetramethylammonium chloride to a four-necked glass bottle in sequence, and react at 75°C for 2h. After the reaction is completed, distill under reduced pressure, then add 350mL of toluene solvent and 33g of 30% sodium hydroxide solution, and react at 75°C for 2h. Then put the reaction solution into a separating funnel, let it stand for stratification, and distill under reduced pressure to obtain an oligomer. Then, mix 85g of the oligomer with 53g of tetrabromobisphenol A, add 0.9g of triphenylphosphine, and react at 125°C for 4h to obtain a brominated epoxy resin. (2) 2.5 g of chitosan was placed in 40 mL of N, N-dimethylacetamide and swelled at 80 °C for 24 h. Subsequently, 126 g of brominated epoxy resin was dissolved in 250 mL of N, N-dimethylacetamide and added to the reaction system. At the same time, 14 g of diphenylmethane-4,4'-diisocyanate was added to the reaction system. The mixture was reacted at 110 °C for 22 h and the modified brominated epoxy resin was obtained by rotary evaporation. (3) Add 25 mL of orthophosphoric acid to 8 g of natural graphite and stir to disperse evenly. Then slowly add 80 mL of 69% nitric acid. Ultrasonicate the mixture for 30 min and react at 95 °C for 3 h. Add 4 g of aluminum phosphate and continue heating at 98 °C for 3 h. Cool, filter with 0.45 μm filter paper, and dry at 60 °C to obtain functionalized graphene. (4) 5.5 g of functionalized graphene was added to 150 mL of acetone solvent for ultrasonic dispersion, and then 110 g of modified brominated epoxy resin was added and stirred for 30 min. Then, the mixture was evaporated in a blast oven at 60 °C for 24 h to obtain a dispersion. 28 g of 4,4-diaminodiphenylmethane was preheated at 110 °C for 20 min and then added to the dispersion. The mixture was stirred evenly and cast into a polytetrafluoroethylene mold for curing. The mixture was first cured at 100 °C for 2 h, then heated to 150 °C and kept at this temperature for 4 h for curing. The mixture was cooled to obtain a brominated epoxy resin composite material.

[0024] Comparative Example 4: A brominated epoxy resin composite material, the specific preparation steps are as follows: (1) Add 57g of tetrabromobisphenol A, 85g of epichlorohydrin, and 0.8g of tetramethylammonium chloride to a four-necked glass bottle in sequence, and react at 75°C for 2h. After the reaction is completed, distill under reduced pressure, then add 350mL of toluene solvent and 33g of 30% sodium hydroxide solution, and react at 75°C for 2h. Then put the reaction solution into a separating funnel, let it stand for stratification, and distill under reduced pressure to obtain an oligomer. Then, mix 85g of the oligomer with 53g of tetrabromobisphenol A, add 0.9g of triphenylphosphine, and react at 125°C for 4h to obtain a brominated epoxy resin. (2) 2.44 g of natural graphite, 4.33 g of chitosan, and 1.22 g of aluminum phosphate were added to 150 mL of acetone solvent and ultrasonically dispersed. Then, 110 g of brominated epoxy resin was added and stirred ultrasonically for 30 min. Then, the mixture was volatilized in a blast oven at 60 °C for 24 h to obtain a dispersion. 28 g of 4,4-diaminodiphenylmethane was preheated at 110 °C for 20 min and then added to the dispersion. The mixture was stirred evenly and cast into a polytetrafluoroethylene mold for curing. The mixture was first cured at 100 °C for 2 h, then heated to 150 °C and kept at this temperature for 4 h for curing. The mixture was cooled to obtain a graphite-brominated epoxy resin composite material.

[0025] Performance Testing Tensile strength: The tensile strength test was carried out using an XWW-20A universal mechanical testing machine, and the GB / T1042-1992 test standard was used as the test criterion. The test results are shown in Table 1.

[0026] Impact strength test: XJ-300A impact testing machine was used to conduct the impact strength test, and GB / T1043.1-2008 was used as the test standard. The test results are shown in Table 1.

[0027] Limiting oxygen index (LOI) test: According to the AMSD D286 standard, the test was performed using a K-R2406S LOI instrument. The test sample size was 130 mm × 6.5 mm × 3.2 mm. The test results are shown in Table 1.

[0028] Vertical combustion method (UL-94) test: The instrument selected for testing is the HVR-JT UL-94 instrument. The UL-94 test is used to evaluate the combustion behavior of the material. The evaluation level is divided into three levels: V-2, V-1 and V-0. The test results are shown in Table 1.

[0029] Water absorption rate: Cut the sample into specimens with a size of 55×55×1.1mm, and then weigh them, which is m1. Then immerse them completely in water, cook them at 100℃ for 4h, take them out, dry them, and weigh them, which is m2. The water absorption rate is calculated according to the following formula: Water absorption rate (%) = (m2-m1) / m1×100%. The test results are shown in Table 1.

[0030]

[0031] Data analysis shows that the graphene-reinforced brominated epoxy resin composite material of the present invention has good mechanical properties, flame retardant properties, and waterproof and water-resistant properties.

[0032] It can be seen from the data in Table 1 that the composite material obtained in Example 2 is superior to that in Comparative Example 1 in terms of mechanical properties, flame retardancy and waterproof performance. This is mainly because the brominated epoxy resin is modified with chitosan. On the one hand, chitosan itself decomposes and carbonizes when heated to form a carbon layer with certain heat insulation and oxygen isolation effects, thereby playing a flame retardant role. At the same time, grafting enables chitosan to participate in the cross-linked network of the epoxy resin, making the overall structure denser, thereby ensuring that the overall mechanical properties are improved to a certain extent. At the same time, this dense structure can reduce It reduces the pores and defects inside the material, reduces the possibility of water molecules penetrating through the internal channels of the material, and thus improves the waterproof performance. Most importantly, due to the presence of free chitosan in the side chains of the modified brominated epoxy resin and chitosan on the surface of the functionalized graphene, the functionalized graphene can be better integrated into the polymer network without agglomeration, and the two can cooperate with each other to further ensure the density of the water-blocking physical barrier. In addition, a certain π-π interaction may be formed between the two, and this π-π interaction can further enhance the mutual synergy between chitosan and functionalized graphene.

[0033] It can be seen from Example 2 and Comparative Example 2 that the mechanical, flame retardant and waterproof properties of the composite material obtained by modifying the brominated epoxy resin with diphenylmethane-4,4'-diisocyanate instead of hexamethylene diisocyanate are improved to a certain extent. This is mainly because diphenylmethane-4,4'-diisocyanate contains more rigid groups than hexamethylene diisocyanate, which can improve the performance of the composite material to a certain extent. On the other hand, the brominated epoxy resin modified with diphenylmethane-4,4'-diisocyanate as a cross-linking agent may form a certain π-π interaction with the functionalized graphene, synergistically improving its mechanical, flame retardant and waterproof properties.

[0034] It can be seen from Example 2 and Comparative Examples 3 and 4 that the performance of the composite material is greatly improved by loading chitosan on the surface of graphene. On the one hand, the overall density of the functionalized graphene is improved, thereby ensuring that it has better mechanical strength and water resistance. At the same time, both chitosan and graphene themselves have certain flame retardancy. By loading them, the flame retardancy of the functionalized graphene can be improved to a certain extent. On the other hand, the graphene-loaded chitosan can be better dispersed in the entire cross-linked system by modifying the chitosan on the brominated epoxy resin side chain.

[0035] Those skilled in the art should understand that the discussion of any of the above embodiments is merely illustrative and is not intended to imply that the scope of the present invention is limited to these examples. Within the scope of the present invention, the technical features in the above embodiments or different embodiments may be combined, the steps may be implemented in any order, and there are many other variations of the different aspects of the present invention as described above, which are not provided in detail for the sake of simplicity.

Claims

1. A method for preparing a graphene-reinforced brominated epoxy resin composite material, characterized in that: The following steps are involved: S1: Preparation of brominated epoxy resin: Tetrabromobisphenol A, epichlorohydrin, and tetramethylammonium chloride are reacted at 70-80°C for 2-3 hours. After the reaction is completed, the mixture is distilled under reduced pressure. Toluene and sodium hydroxide solution are then added, and the mixture is reacted at 70-80°C for 1-2 hours. The mixture is then distilled to obtain an oligomer. The oligomer is then mixed with tetrabromobisphenol A, and triphenylphosphine is added. The mixture is reacted at 120-130°C for 3-4 hours to obtain a brominated epoxy resin. S2: preparing a modified brominated epoxy resin: swelling chitosan in N,N-dimethylacetamide, dissolving brominated epoxy resin in N,N-dimethylacetamide, and adding the mixture to a reaction system; and simultaneously adding diphenylmethane-4,4'-diisocyanate to the reaction system. The mixture is reacted at 100-120° C. for 20-24 hours, and rotary evaporated to obtain a modified brominated epoxy resin. S3 Preparation of functionalized graphene: Orthophosphoric acid is added to natural graphite, stirred and dispersed uniformly, followed by slow addition of nitric acid, ultrasonic treatment, and reaction at 90-100°C for 2-3 hours. Chitosan is then added and dissolved, followed by addition of aluminum phosphate, and heating at 95-100°C for 2-3 hours. The mixture is cooled, filtered, and dried to obtain functionalized graphene. S4: adding the functionalized graphene to acetone for ultrasonic dispersion, then adding the modified brominated epoxy resin, stirring and ultrasonically dispersing for 30 minutes, volatilizing to obtain a dispersion, preheating 4,4-diaminodiphenylmethane, then adding it to the dispersion, stirring evenly, casting it into a polytetrafluoroethylene mold for curing, and cooling it to obtain a graphene-reinforced brominated epoxy resin composite material; In step S1, the ratio of tetrabromobisphenol A, epichlorohydrin, tetramethylammonium chloride, toluene, and sodium hydroxide solution is 54-60 g: 80-90 g: 0.75-0.9 g: 300-400 mL: 30-35 g; The oligomer, tetrabromobisphenol A, and triphenylphosphine used in step S1 are used in a ratio of 70-100 g: 50-55 g: 0.8-1 g; In step S2, the chitosan, N,N-dimethylacetamide, brominated epoxy resin, and diphenylmethane-4,4'-diisocyanate are used in a ratio of 2-3 g: 240-340 mL: 122-130 g: 13.5-15 g; The usage ratio of orthophosphoric acid, natural graphite, nitric acid, chitosan, and aluminum phosphate in step S3 is 20-30 mL: 5-10 g: 60-100 mL: 5-7 g: 3-5 g; The amount ratio of the functionalized graphene, acetone, modified brominated epoxy resin, and 4,4-diaminodiphenylmethane in step S4 is 5-6 g: 100-200 mL: 100-120 g: 25-30 g.

2. The method for preparing the graphene-enhanced brominated epoxy resin composite material according to claim 1, wherein: The concentration of the sodium hydroxide solution in step S1 is 30%.

3. The method for preparing the graphene-enhanced brominated epoxy resin composite material according to claim 1, wherein: The swelling in step S2 is carried out at 80° C. for 24 h.

4. The method for preparing the graphene-enhanced brominated epoxy resin composite material according to claim 1, wherein: The concentration of nitric acid in step S3 is 69%.

5. The method for preparing the graphene-enhanced brominated epoxy resin composite material according to claim 1, wherein: The volatilization in step S4 is carried out in a forced air oven at 60° C. for 24 h.

6. The method for preparing the graphene-enhanced brominated epoxy resin composite material according to claim 1, wherein: The preheating in step S4 is preheating at 110° C. for 20 minutes.

7. The method for preparing the graphene-enhanced brominated epoxy resin composite material according to claim 1, wherein: The curing in step S4 is first performed at 100° C. for 2 h, and then heated to 150° C. and kept at that temperature for 4 h.

8. A graphene-reinforced brominated epoxy resin composite material, characterized in that: The graphene-enhanced brominated epoxy resin composite material is prepared according to the preparation method of any one of claims 1 to 7.

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