Modified graphene reinforced epdm composites and methods of making

Abstract

This invention relates to the field of EPDM rubber technology, and discloses a modified graphene-reinforced EPDM rubber composite material and its preparation method, comprising 100 parts by weight of EPDM rubber, 1-1.4 parts by weight of antioxidant, 2-3 parts by weight of sulfur, 1-1.5 parts by weight of accelerator, 0.5-5 parts by weight of flame-retardant modified graphene, and 0.15-2 parts by weight of compatibilizer ethylene-vinyl acetate copolymer. The ethylene-vinyl acetate copolymer of this invention can act as a compatibilizer, enhancing the compatibility between the flame-retardant modified graphene and EPDM rubber, allowing graphene to play a better reinforcing role and significantly improving the material's hardness and other mechanical properties. The flame-retardant modified graphene contains a large number of diphenyl bisphosphate flame-retardant groups, acting as a phosphorus-containing flame retardant, giving the composite material better flame-retardant properties and exhibiting a higher limiting oxygen index.

Description

Technical Field

[0001] This invention relates to the field of EPDM rubber technology, specifically to a modified graphene-reinforced EPDM rubber composite material and its preparation method. Background Technology

[0002] Ethylene propylene diene monomer (EPDM) rubber possesses excellent heat resistance, weather resistance, and aging resistance, making it widely used in wires and cables, household appliances, and building flooring materials. Improving the mechanical strength and flame retardancy of EPDM rubber is a research hotspot. Reinforcing EPDM rubber with inorganic nanoparticles such as graphene and titanium dioxide is an effective method to enhance its mechanical properties.

[0003] Graphene possesses high mechanical strength, strong high-temperature resistance, and certain flame-retardant properties, making it widely applicable. Chinese patent CN107236199B discloses a modified EPDM rubber and its preparation method, which involves in-situ synthesis of hyperbranched phosphoramides on the surface of graphene oxide, improving the mechanical properties, flame-retardant properties, and thermal conductivity of EPDM rubber. Improving the compatibility between graphene and EPDM rubber allows graphene to exert a better reinforcing effect, thus enhancing the mechanical properties of EPDM rubber. Summary of the Invention

[0004] This invention solves the problems of poor compatibility between graphene and EPDM rubber, as well as the poor flame retardancy of EPDM rubber.

[0005] The technical solution provided by this invention is:

[0006] A modified graphene-reinforced EPDM rubber composite material comprises 100 parts by weight of EPDM rubber, 1-1.4 parts by weight of antioxidant, 2-3 parts by weight of sulfur, 1-1.5 parts by weight of accelerator, 1-2 parts by weight of stearic acid, 6-12 parts by weight of zinc oxide, 0.5-5 parts by weight of flame retardant modified graphene, and 0.15-2 parts by weight of compatibilizer ethylene-vinyl acetate copolymer.

[0007] The preparation method of flame retardant modified graphene is as follows: KH570 modified graphene is added to toluene, ultrasonically dispersed, vinyl acetate flame retardant is added, nitrogen gas is introduced, an initiator is added, the solution is concentrated after reaction, washed with ethanol, and dried to obtain flame retardant modified graphene.

[0008] The structural formula of vinyl acetate flame retardant is formula (Ⅰ):

[0009] Equation (Ⅰ).

[0010] The amount of KH570 modified graphene is 100 parts by weight, the amount of vinyl acetate flame retardant is 500-1500 parts by weight, and the amount of initiator is 4.4-16 parts by weight.

[0011] The initiator is either azobisisobutyronitrile or benzoyl peroxide.

[0012] The reaction is carried out at 75-85℃ for 8-12 hours.

[0013] The preparation method of vinyl acetate flame retardant is as follows:

[0014] Step (1): Add 100 parts by weight of 2-(3,5-dihydroxyphenyl)acetic acid (CAS Registry No. 4670-09-1), 650-720 parts by weight of vinyl acetate (CAS Registry No. 108-05-4), and 3.6-4.4 parts by weight of mercuric acetate to tetrahydrofuran. Add 1.2-1.5 parts by weight of concentrated sulfuric acid (98% by mass) dropwise. React at 60-65℃ for 6-10 hours, refluxing during the reaction. After the reaction, add sodium acetate, stir, concentrate the solution, add water and ethyl acetate, extract by shaking, allow to stand for separation, dry the ethyl acetate phase, and concentrate to obtain 2-(3,5-dihydroxyphenyl)vinyl acetate. The reaction formula is as follows:

[0015]

[0016] Step (2): Under ice-water bath conditions, add 100 parts by weight of 2-(3,5-dihydroxyphenyl)vinyl acetate, 280-310 parts by weight of diphenyl chlorophosphate (CAS Registry No. 2524-64-3), and 200-225 parts by weight of triethylamine to toluene. Then react at 30-45℃ for 18-24 hours. Concentrate the solution, wash with methanol, and recrystallize with ethyl acetate to obtain the vinyl acetate flame retardant. The reaction formula is:

[0017]

[0018] The preparation method of modified graphene-reinforced EPDM rubber composite material is as follows: EPDM rubber is internally mixed in a mixer for 3-4 minutes at a roller temperature of 120-125℃; then zinc oxide, flame retardant modified graphene, compatibilizer ethylene-vinyl acetate copolymer, and stearic acid are added, and the mixture is discharged at 100-110℃ to obtain masterbatch; then the masterbatch is mixed with antioxidant, accelerator, and sulfur in a two-roll mill for 10-15 minutes using a triangular rolling mill, thin-passing, and sheeting, cooled, and finally placed in a flat vulcanizing agent and vulcanized at 160-170℃ under a pressure of 8-10MPa to obtain modified graphene-reinforced EPDM rubber composite material.

[0019] The technical effect of this invention is that it uses mercuric acetate and concentrated sulfuric acid as a catalytic system to carry out transesterification of 2-(3,5-dihydroxyphenyl)acetic acid and vinyl acetate, and then reacts them with diphenyl chlorophosphate to obtain a novel vinyl acetate flame retardant.

[0020] This invention utilizes a graft polymerization reaction between an alkenyl-containing vinyl acetate flame retardant and KH570 modified graphene to graft polyvinyl acetate flame retardant molecular chains onto the graphene surface, thereby introducing polyvinyl acetate molecular chains onto the graphene surface. Simultaneously, the added ethylene-vinyl acetate copolymer exhibits excellent compatibility with EPDM rubber, and since the ethylene-vinyl acetate copolymer also contains polyvinyl acetate molecular chains, it also demonstrates excellent compatibility with the flame retardant-modified graphene. This allows the ethylene-vinyl acetate copolymer to act as a compatibilizer, enhancing the compatibility between the flame retardant-modified graphene and EPDM rubber, improving the dispersion of graphene in EPDM rubber, and enabling graphene to provide better reinforcement. This significantly improves the Shore A hardness, tensile properties, and tear strength of the material.

[0021] The flame retardant modified graphene of the present invention contains a large number of diphenyl bisphosphate flame retardant groups. As a phosphorus-containing flame retardant, it can promote the dehydration of EPDM rubber into carbon during combustion and form an inorganic carbon composite layer with graphene at a continuous temperature. This can isolate oxygen, inhibit heat conduction, and prevent dripping, thus giving the composite material better flame retardant properties and exhibiting a higher limiting oxygen index. Detailed Implementation

[0022] To make the technical solutions of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. It should be noted that the following embodiments are only used to better understand the technical solutions of the present invention and should not be construed as limiting the present invention.

[0023] The graphene oxide of this invention has a diameter of 0.5-3 μm and a thickness of 0.55-1.2 nm.

[0024] Ethylene propylene diene monomer (EPDM) rubber grade TER 4436. Ethylene-vinyl acetate copolymer grade V5110J.

[0025] Example 1

[0026] (1) Add 2g of 2-(3,5-dihydroxyphenyl)acetic acid, 13g of vinyl acetate and 72mg of mercuric acetate to 40mL of tetrahydrofuran, and add 30mg of concentrated sulfuric acid (98% by mass) dropwise. React at 65℃ for 6h, and reflux during the reaction. After the reaction, add sodium acetate, stir and concentrate the solution, add water and ethyl acetate, shake to extract, let stand to separate the layers, dry the ethyl acetate phase and concentrate to obtain 2-(3,5-dihydroxyphenyl)vinyl acetate.

[0027] (2) Add 2g of 2-(3,5-dihydroxyphenyl)vinyl acetate, 6.2g of diphenyl chlorophosphate and 4.5g of triethylamine to 60mL of toluene in an ice-water bath, and then react at 30℃ for 18h. Concentrate the solution, wash with methanol and recrystallize with ethyl acetate to obtain vinyl acetate flame retardant.

[0028] (3) Add 40 mg of graphene oxide to 20 mL of water and disperse it by sonication. Then add 1 mL of KH570 and 60 mL of ethanol. After dispersion, add glacial acetic acid to adjust the pH of the solution to 4. Heat to 70 °C and react for 5 h. Cool, centrifuge to separate, wash the precipitate with ethanol, and dry to obtain KH570 modified graphene.

[0029] (4) Add 0.5g of KH570 modified graphene to 80mL of toluene, disperse it by ultrasonication, add 2.5g of vinyl acetate flame retardant, introduce nitrogen gas, add 22mg of initiator benzoyl peroxide, react at 80℃ for 8h, concentrate the solution, wash with ethanol, dry it to obtain flame retardant modified graphene.

[0030] (5) Mix 1000g of EPDM rubber in a mixer for 4 minutes at a roller temperature of 120℃; then add 80g of zinc oxide, 5g of flame retardant modified graphene, 1.5g of compatibilizer ethylene-vinyl acetate copolymer, and 12g of stearic acid, and discharge the rubber at 110℃ to obtain masterbatch; then mix the masterbatch with 14g of antioxidant 2-mercaptoimidazole, 15g of accelerator N-cyclohexyl-2-benzothiazole sulfenamide, and 22g of sulfur in a two-roll mill for 15 minutes, followed by 5 triangular wraps, 8 thin passes, and sheeting; cool the mixture and finally place it in a flat vulcanizing agent and vulcanize it at 160℃ and 10MPa pressure to obtain a modified graphene-reinforced EPDM rubber composite material.

[0031] Example 2

[0032] (1) Add 2g of 2-(3,5-dihydroxyphenyl)acetic acid, 14.4g of vinyl acetate and 88mg of mercuric acetate to 50mL of tetrahydrofuran, and add 24mg of concentrated sulfuric acid (98% by mass) dropwise. React at 65℃ for 10h, and reflux during the reaction. After the reaction, add sodium acetate, stir and concentrate the solution, add water and ethyl acetate, shake to extract, let stand to separate the layers, dry the ethyl acetate phase and concentrate to obtain 2-(3,5-dihydroxyphenyl)vinyl acetate.

[0033] (2) Add 2g of 2-(3,5-dihydroxyphenyl)vinyl acetate, 5.6g of diphenyl chlorophosphate and 4g of triethylamine to 50mL of toluene in an ice-water bath, and then react at 45℃ for 24h. Concentrate the solution, wash with methanol and recrystallize with ethyl acetate to obtain vinyl acetate flame retardant.

[0034] (3) Add 0.5g of KH570 modified graphene (prepared according to the method of Example 1) to 150mL of toluene, disperse it by ultrasonication, add 5g of vinyl acetate flame retardant, introduce nitrogen gas, add 52mg of initiator azobisisobutyronitrile, react at 75℃ for 12h, concentrate the solution, wash with ethanol, dry and obtain flame retardant modified graphene.

[0035] (4) Mix 1000g of EPDM rubber in a mixer for 3 minutes at a roller temperature of 125℃; then add 120g of zinc oxide, 5g of flame retardant modified graphene, 1.5g of compatibilizer ethylene-vinyl acetate copolymer, and 10g of stearic acid, and discharge the rubber at 110℃ to obtain masterbatch; then mix the masterbatch with 10g of antioxidant 2-mercaptoimidazole, 15g of accelerator N-cyclohexyl-2-benzothiazole sulfenamide, and 30g of sulfur in a two-roll mill for 15 minutes, followed by 5 triangular wraps, 8 thin passes, and sheeting; cool the mixture and finally place it in a flat vulcanizing agent and vulcanize it at 165℃ and 10MPa pressure to obtain the modified graphene-reinforced EPDM rubber composite material.

[0036] Example 3

[0037] (1) Add 0.5g of KH570 modified graphene (prepared according to the method of Example 1) to 200mL of toluene, disperse it by ultrasonication, add 7.5g of vinyl acetate flame retardant (prepared according to the method of Example 1), introduce nitrogen gas, add 80mg of initiator benzoyl peroxide, react at 85℃ for 8h, concentrate the solution, wash with ethanol, dry it to obtain flame retardant modified graphene.

[0038] (2) 1000g of EPDM rubber was mixed in an internal mixer for 3 minutes at a roller temperature of 125℃. Then, 60g of zinc oxide, 5g of flame retardant modified graphene, 1.5g of compatibilizer ethylene-vinyl acetate copolymer, and 20g of stearic acid were added. The rubber was discharged at 100℃ to obtain the masterbatch. Then, the masterbatch was mixed with 11g of antioxidant 2-mercaptoimidazole, 10g of accelerator N-cyclohexyl-2-benzothiazole sulfenamide, and 20g of sulfur in a two-roll mill for 10 minutes after triangular wrapping 5 times, thin passing 8 times, and sheeting. After cooling, it was placed in a flat vulcanizing agent and vulcanized at 170℃ and 8MPa pressure to obtain the modified graphene-reinforced EPDM rubber composite material.

[0039] Comparative Example 1

[0040] The difference between this comparative example and Example 1 is that no flame retardant was added to modify the graphene.

[0041] (1) 1000g of EPDM rubber was mixed in an internal mixer for 4 minutes at a roller temperature of 120℃; then 80g of zinc oxide, 1.5g of compatibilizer ethylene-vinyl acetate copolymer, and 12g of stearic acid were added, and the rubber was discharged at 110℃ to obtain masterbatch; then the masterbatch was mixed with 14g of antioxidant 2-mercaptoimidazole, 15g of accelerator N-cyclohexyl-2-benzothiazole sulfenamide, and 22g of sulfur in a two-roll mill for 5 triangular wraps, 8 thin passes, and sheet mixing for 15 minutes, cooled, and finally placed in a flat vulcanizing agent and vulcanized at 160℃ and 10MPa pressure to obtain modified graphene-reinforced EPDM rubber composite material.

[0042] Comparative Example 2

[0043] The difference between this comparative example and Example 1 is that unmodified graphene oxide was added.

[0044] (1) 1000g of EPDM rubber was internally mixed in a mixer for 4 minutes at a roller temperature of 120℃; then 80g of zinc oxide, 5g of graphene oxide, 1.5g of compatibilizer ethylene-vinyl acetate copolymer, and 12g of stearic acid were added, and the mixture was discharged at 110℃ to obtain a masterbatch; then the masterbatch was mixed with 14g of antioxidant 2-mercaptoimidazole, 15g of accelerator N-cyclohexyl-2-benzothiazole sulfenamide, and 22g of sulfur in a two-roll mill for 15 minutes after triangular wrapping 5 times, thin-passing 8 times, and sheeting; cooled; and finally placed in a flat vulcanizing agent and vulcanized at 160℃ and 10MPa pressure to obtain a modified graphene-reinforced EPDM rubber composite material.

[0045] Comparative Example 3

[0046] The difference between this comparative example and Example 1 is the addition of KH570 modified graphene.

[0047] (1) 1000g of EPDM rubber was mixed in an internal mixer for 4 minutes at a roller temperature of 120℃. Then, 80g of zinc oxide, 5g of KH570 modified graphene, 1.5g of compatibilizer ethylene-vinyl acetate copolymer, and 12g of stearic acid were added. The mixture was discharged at 110℃ to obtain masterbatch. Then, the masterbatch was mixed with 14g of antioxidant 2-mercaptoimidazole, 15g of accelerator N-cyclohexyl-2-benzothiazole sulfenamide, and 22g of sulfur in a two-roll mill for 15 minutes after triangular wrapping 5 times, thin passing 8 times, and sheeting. After cooling, the mixture was placed in a flat vulcanizing agent and vulcanized at 160℃ and 10MPa pressure to obtain a modified graphene-reinforced EPDM rubber composite material.

[0048] Comparative Example 4

[0049] The difference between this comparative example and Example 1 is that, in preparing the modified graphene, vinyl acetate (…) was added. It does not contain vinyl acetate flame retardant.

[0050] (1) Add 0.5g of KH570 modified graphene to 80mL of toluene, disperse it by ultrasonication, add 2.5g of vinyl acetate, introduce nitrogen gas, add 22mg of initiator benzoyl peroxide, react at 80℃ for 8h, concentrate the solution, wash with ethanol, dry and obtain modified graphene.

[0051] (2) 1000g of EPDM rubber was mixed in an internal mixer for 4 minutes at a roller temperature of 120℃. Then, 80g of zinc oxide, 5g of modified graphene, 1.5g of compatibilizer ethylene-vinyl acetate copolymer, and 12g of stearic acid were added. The mixture was discharged at 110℃ to obtain masterbatch. The masterbatch was then mixed with 14g of antioxidant 2-mercaptoimidazole, 15g of accelerator N-cyclohexyl-2-benzothiazole sulfenamide, and 22g of sulfur in a two-roll mill for 15 minutes after triangular wrapping 5 times, thin passing 8 times, and sheeting. After cooling, the mixture was placed in a flat vulcanizing agent and vulcanized at 160℃ and 10MPa pressure to obtain a modified graphene-reinforced EPDM rubber composite material.

[0052] Comparative Example 5

[0053] The difference between this comparative example and Example 1 is that the compatibilizer ethylene-vinyl acetate copolymer is not added.

[0054] (1) 1000g of EPDM rubber was mixed in an internal mixer for 4 minutes at a roller temperature of 120℃. Then, 80g of zinc oxide, 5g of flame retardant modified graphene, and 12g of stearic acid were added and discharged at 110℃ to obtain masterbatch. Then, the masterbatch was mixed with 14g of antioxidant 2-mercaptoimidazole, 15g of accelerator N-cyclohexyl-2-benzothiazole sulfenamide, and 22g of sulfur in a two-roll mill for 15 minutes of triangular wrapping, thin-passing, and sheeting. After cooling, it was placed in a flat vulcanizing agent and vulcanized at 160℃ and 10MPa pressure to obtain EPDM rubber composite material.

[0055] Shore A hardness was tested according to the national standard GB / T 531.1-2008.

[0056] Tensile properties were tested according to GB / T 528-2009. The tensile speed was 500 mm / min, and the test temperature was 25℃.

[0057] Tear resistance was tested according to GB / T 529-2008. The tensile speed was 500 mm / min, and the test temperature was 25℃.

[0058] The oxygen index was tested according to the method in GB / T 10707-2008.

[0059] Table 1 Performance testing of EPDM rubber composite materials

[0060]

[0061] As shown in Table 1, the EPDM rubber of Comparative Example 1, which did not contain graphene, had a Shore A hardness of 68, a tensile strength of 16.4 MPa, an elongation at break of 386.8%, a tear strength of 48.9 kN / m, and a limiting oxygen index of 22.4%.

[0062] In Examples 1-3, flame-retardant-modified graphene was added to EPDM rubber, resulting in significant improvements in Shore A hardness, tensile strength, elongation at break, and tear strength. This is because a graft polymerization reaction was carried out between a vinyl acetate flame retardant containing alkenyl groups and KH570-modified graphene, grafting polyvinyl acetate flame retardant molecular chains onto the graphene surface, thereby introducing polyvinyl acetate molecular chains onto the graphene surface. The added ethylene-vinyl acetate copolymer exhibits excellent compatibility with EPDM rubber. Since the ethylene-vinyl acetate copolymer also contains polyvinyl acetate molecular chains, it also demonstrates good compatibility with the flame-retardant-modified graphene. This allows the ethylene-vinyl acetate copolymer to act as a compatibilizer, enhancing the compatibility between the flame-retardant-modified graphene and EPDM rubber, improving the dispersion of graphene in EPDM rubber, and enabling graphene to provide better reinforcement. This significantly improves the Shore A hardness, tensile properties, and tear strength of the material. Furthermore, the flame-retardant-modified graphene contains a large number of diphenyl bisphosphate flame-retardant groups. The polymer, as a phosphorus-containing flame retardant, can promote the dehydration of EPDM rubber into carbon during combustion, forming a continuous temperature inorganic carbon composite layer with graphene. This can isolate oxygen, inhibit heat conduction, and prevent dripping, giving the composite material better flame retardant properties and exhibiting a higher limiting oxygen index.

[0063] Compared with Example 1, the unmodified graphene added in Comparative Example 2 has poor compatibility with EPDM rubber. The graphene has poor dispersibility and is prone to agglomeration, resulting in poor reinforcement effect on EPDM rubber. The Shore A hardness, tensile strength and tear strength are not significantly improved. Furthermore, the graphene surface does not have polymers with grafted diphenyl bisphosphate flame retardant groups, resulting in poor flame retardant effect on EPDM rubber and a lower limiting oxygen index than in Example 1.

[0064] Compared to Example 1, Comparative Example 3 incorporated KH570-modified graphene. After KH570 modification, the compatibility between graphene and EPDM rubber was poor, but the graphene exhibited better dispersibility and was less prone to agglomeration, resulting in a better reinforcing effect on EPDM rubber. The Shore A hardness, tensile properties, and tear strength were significantly higher than in Comparative Example 2. While the elongation at break and tear strength were higher than in Example 1, the Shore A hardness and tensile strength were lower. This may be due to the better compatibilizing effect of the ethylene-vinyl acetate copolymer. Furthermore, the graphene-grafted flame retardant polymer contained a large number of rigid aromatic ring structures, which was beneficial for improving the hardness and tensile strength of EPDM rubber. However, the KH570-modified graphene lacked polymers with grafted diphenyl bisphosphate flame retardant groups, resulting in a poor flame retardant effect on EPDM rubber and a lower limiting oxygen index than in Example 1.

[0065] Comparative Example 4 involved graft polymerization of vinyl acetate with KH570-modified graphene, introducing polyvinyl acetate molecular chains onto the graphene surface. The ethylene-vinyl acetate copolymer exhibited good compatibility with the modified graphene, allowing it to act as a compatibilizer. This enhanced the compatibility between the flame-retardant-modified graphene and EPDM rubber, improved the dispersibility of graphene in EPDM rubber, and enabled graphene to provide better reinforcement. This significantly improved the Shore A hardness, tensile properties, and tear strength of the material, exceeding those of Comparative Example 3, possibly due to the better compatibilizing effect of the ethylene-vinyl acetate copolymer. However, the modified graphene lacked a polymer with grafted diphenyl bisphosphate flame-retardant groups, resulting in poor flame-retardant performance on EPDM rubber and a lower limiting oxygen index than in Example 1.

[0066] Compared to Example 1, Comparative Example 5 did not include the compatibilizer ethylene-vinyl acetate copolymer. The flame-retardant-modified graphene showed poor compatibility with EPDM rubber, resulting in inadequate reinforcement; its Shore A hardness, tensile properties, and tear strength were significantly lower than in Example 1. However, the polymer with diphenyl bisphosphate flame-retardant groups grafted onto the surface of the modified graphene exhibited excellent flame-retardant effects on EPDM rubber, achieving a limiting oxygen index of 25.3%.

[0067] Example 4

[0068] The difference between Example 1 and Example 3 is that the amount of flame retardant-modified graphene used is 20g, and the amount of ethylene-vinyl acetate copolymer is 7g.

[0069] (2) 1000g of EPDM rubber was mixed in an internal mixer for 3 minutes at a roller temperature of 125℃. Then, 60g of zinc oxide, 20g of flame retardant modified graphene (prepared according to the method of Example 3), 7g of compatibilizer ethylene-vinyl acetate copolymer, and 20g of stearic acid were added. The rubber was discharged at 100℃ to obtain masterbatch. Then, the masterbatch was mixed with 11g of antioxidant 2-mercaptoimidazole, 10g of accelerator N-cyclohexyl-2-benzothiazole sulfenamide, and 20g of sulfur in a two-roll mill for 10 minutes after triangular wrapping 5 times, thin passing 8 times, and sheeting. After cooling, it was placed in a flat vulcanizing agent and vulcanized at 170℃ and 8MPa pressure to obtain modified graphene-reinforced EPDM rubber composite material.

[0070] Example 5

[0071] The difference between Example 1 and Example 3 is that the amount of flame retardant-modified graphene used is 35g, and the amount of ethylene-vinyl acetate copolymer is 12g.

[0072] (2) 1000g of EPDM rubber was mixed in an internal mixer for 3 minutes at a roller temperature of 125℃. Then, 60g of zinc oxide, 35g of flame retardant modified graphene (prepared according to the method of Example 3), 12g of compatibilizer ethylene-vinyl acetate copolymer, and 20g of stearic acid were added. The rubber was discharged at 100℃ to obtain masterbatch. Then, the masterbatch was mixed with 11g of antioxidant 2-mercaptoimidazole, 10g of accelerator N-cyclohexyl-2-benzothiazole sulfenamide, and 20g of sulfur in a two-roll mill for 10 minutes after triangular wrapping 5 times, thin passing 8 times, and sheeting. After cooling, it was placed in a flat vulcanizing agent and vulcanized at 170℃ and 8MPa pressure to obtain modified graphene-reinforced EPDM rubber composite material.

[0073] Example 6

[0074] The difference between Example 1 and Example 3 is that the amount of flame retardant-modified graphene used is 50g, and the amount of ethylene-vinyl acetate copolymer is 20g.

[0075] (2) 1000g of EPDM rubber was mixed in an internal mixer for 3 minutes at a roller temperature of 125℃. Then, 60g of zinc oxide, 50g of flame retardant modified graphene (prepared according to the method in Example 3), 20g of compatibilizer ethylene-vinyl acetate copolymer, and 20g of stearic acid were added. The mixture was discharged at 100℃ to obtain masterbatch. Then, the masterbatch was mixed with 11g of antioxidant 2-mercaptoimidazole, 10g of accelerator N-cyclohexyl-2-benzothiazole sulfenamide, and 20g of sulfur in a two-roll mill for 10 minutes after triangular wrapping 5 times, thin passing 8 times, and sheeting. After cooling, the mixture was placed in a flat vulcanizing agent and vulcanized at 170℃ and 8MPa pressure to obtain a modified graphene-reinforced EPDM rubber composite material.

[0076] Table 2 Performance Tests of Modified Graphene-Reinforced EPDM Rubber Composites

[0077]

[0078] As shown in Table 1, with the increase of the amount of flame retardant modified graphene, the limiting oxygen index also increases, the flame retardancy becomes better and better, and the Shore A hardness, tensile properties and tear strength are significantly improved.

[0079] The foregoing description of this disclosure is provided to enable any person skilled in the art to implement or use this disclosure. Various modifications to this disclosure will be apparent to those skilled in the art, and the general principles applicable herein can be applied to other variations without departing from the scope of this disclosure. Therefore, this disclosure is not limited to the examples and designs described herein, but is consistent with the widest scope of the principles and novel features disclosed herein.

Claims

1. A modified graphene-reinforced EPDM rubber composite material, characterized in that, The composite material comprises 100 parts by weight of ethylene propylene diene monomer (EPDM) rubber, 1-1.4 parts by weight of antioxidant, 2-3 parts by weight of sulfur, 1-1.5 parts by weight of accelerator, 1-2 parts by weight of stearic acid, 6-12 parts by weight of zinc oxide, 0.5-5 parts by weight of flame retardant modified graphene, and 0.15-2 parts by weight of compatibilizer ethylene-vinyl acetate copolymer. The method for preparing the flame retardant modified graphene is as follows: KH570 modified graphene is added to toluene, ultrasonically dispersed, vinyl acetate flame retardant is added, nitrogen gas is introduced, an initiator is added, the solution is concentrated after reaction, washed with ethanol, and dried to obtain flame retardant modified graphene. The structural formula of the vinyl acetate flame retardant is formula (Ⅰ): Equation (I); The amount of KH570 modified graphene is 100 parts by weight, the amount of vinyl acetate flame retardant is 500-1500 parts by weight, and the amount of initiator is 4.4-16 parts by weight.

2. The modified graphene-reinforced EPDM rubber composite material according to claim 1, characterized in that, The initiator is azobisisobutyronitrile or benzoyl peroxide.

3. The modified graphene-reinforced EPDM rubber composite material according to claim 1, characterized in that, The reaction was carried out at 75-85℃ for 8-12 hours.

4. The modified graphene-reinforced EPDM rubber composite material according to claim 1, characterized in that, The preparation method of the vinyl acetate flame retardant is as follows: Step (1): Add 2-(3,5-dihydroxyphenyl)acetic acid, vinyl acetate, and mercuric acetate to tetrahydrofuran, add concentrated sulfuric acid dropwise, add sodium acetate after the reaction, concentrate the solution after stirring, add water and ethyl acetate, shake to extract, let stand to separate the layers, dry the ethyl acetate phase, concentrate, and obtain 2-(3,5-dihydroxyphenyl)vinyl acetate. Step (2): Add 2-(3,5-dihydroxyphenyl)vinyl acetate, diphenyl chlorophosphate, and triethylamine to toluene in an ice-water bath, and then react at 30-45℃ for 18-24h. Concentrate the solution, wash with methanol, and recrystallize with ethyl acetate to obtain vinyl acetate flame retardant.

5. The modified graphene-reinforced EPDM rubber composite material according to claim 4, characterized in that, In step (1), the amount of 2-(3,5-dihydroxyphenyl)acetic acid is 100 parts by weight, vinyl acetate is 650-720 parts by weight, mercuric acetate is 3.6-4.4 parts by weight, and concentrated sulfuric acid is 1.2-1.5 parts by weight.

6. The modified graphene-reinforced EPDM rubber composite material according to claim 4, characterized in that, In step (1), the reaction is carried out at 60-65℃ for 6-10 hours.

7. The modified graphene-reinforced EPDM rubber composite material according to claim 4, characterized in that, In step (2), the amount of 2-(3,5-dihydroxyphenyl)vinyl acetate is 100 parts by weight, the amount of diphenyl chlorophosphate is 280-310 parts by weight, and the amount of triethylamine is 200-225 parts by weight.

8. A method for preparing a modified graphene-reinforced EPDM rubber composite material as described in any one of claims 1-7, characterized in that, The preparation method is as follows: EPDM rubber is internally mixed in a mixer for 3-4 minutes at a roller temperature of 120-125℃; then zinc oxide, flame retardant modified graphene, compatibilizer ethylene-vinyl acetate copolymer, and stearic acid are added, and the mixture is discharged at 100-110℃ to obtain masterbatch; then the masterbatch is mixed with antioxidant, accelerator, and sulfur in a two-roll mill for 10-15 minutes by forming triangular bundles, thin passes, and sheeting, cooled, and finally placed in a flat vulcanizing agent and vulcanized at 160-170℃ under a pressure of 8-10MPa to obtain modified graphene-reinforced EPDM rubber composite material.

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