A halogen-free flame-retardant and heat-resistant rubber and its preparation method

Abstract

This invention discloses a halogen-free flame-retardant and heat-resistant rubber and its preparation method, relating to the field of rubber technology. The invention utilizes hydroxylation treatment of lamellar porous carbon to form adsorption sites, promoting the growth of nano-nickel on the surface and within the pores of the porous carbon, forming a metal network, reducing phonon scattering interference, lowering interfacial thermal resistance, and improving thermal conductivity. The nanosheet filler is uniformly dispersed in the rubber matrix, forming a thermally conductive network for rapid heat conduction, avoiding chain segment oxidative degradation, and improving thermal stability and flame retardancy. Simultaneously, this invention also relates to a novel flame-retardant microsphere preparation technology, which uses the polymerization of phosphorus-containing silane compounds to form microspheres rich in Si and P elements, increasing char residue. When combined with lamellar fillers, this improves the char residue of cable materials, rapidly conducts combustion heat, reduces free radical reactions, lowers combustion toxicity, and prepares a low-smoke flame-retardant rubber material.

Description

Technical Field

[0001] This invention relates to the field of rubber technology, specifically to a halogen-free flame-retardant and heat-resistant rubber and its preparation method. Background Technology

[0002] Ethylene propylene diene monomer (EPDM) rubber is an ethylene-propylene-nonconjugated diene copolymer with excellent weather resistance, electrical insulation, ozone resistance, and chemical resistance. Flame retardant modification of EPDM aims to overcome its flammability and improve its application safety. Currently, commercially available flame-retardant EPDM materials mainly use a bromine-antimony oxide flame retardant system. However, halogenated flame retardants are gradually being phased out by new environmental regulations because they produce toxic and corrosive gases during combustion. Therefore, research on halogen-free flame-retardant EPDM has recently attracted widespread attention.

[0003] Currently, most halogen-free flame-retardant EPDM materials use environmentally friendly magnesium hydroxide, aluminum hydroxide, or other additives in combination. Because hydroxides have low flame-retardant efficiency, a magnesium hydroxide content of up to 200 parts by weight is required for EPDM to reach the FV-0 flame-retardant level, relative to 100 parts by weight. At this point, the physical properties of EPDM, especially its elongation at break, become very poor.

[0004] The rubber industry is one of the important basic industries of the national economy. It not only provides essential daily-use and medical rubber products, but also supplies various rubber-made production equipment and components to heavy industries and emerging industries such as mining, transportation, construction, machinery, and electronics. Many rubber products have high requirements for the heat resistance of rubber. For example, rubber conveyor belts are widely used in high-temperature environments such as metallurgy, coking, and building materials, where the materials they transport are sometimes very hot. If the heat resistance of the rubber conveyor belt is insufficient, its service life will be greatly reduced. Summary of the Invention

[0005] The purpose of this invention is to provide a halogen-free flame-retardant and heat-resistant rubber and its preparation method, so as to solve the problems existing in the prior art.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a halogen-free flame-retardant and heat-resistant rubber, comprising, by weight, 40-60 parts of ethylene propylene diene monomer (EPDM) rubber, 15-35 parts of vinyl silicone rubber, 0.5-1.5 parts of sulfur, 0.5-1.5 parts of accelerator DCP, 0.5-1.5 parts of accelerator DM, 10-15 parts of flame-retardant microspheres, 5-10 parts of sheet filler, and 1-5 parts of stearic acid;

[0007] The method for preparing the flame-retardant microspheres is as follows: Diethylphosphorylethyltriethoxysilane, (4-vinylphenyl)trimethoxysilane, tetraethyl orthosilicate, and polyethylene glycol are mixed and stirred evenly at 250 rpm. Then, 0.1 to 0.5 times the mass of diethylphosphorylethyltriethoxysilane in ethanol is added to disperse it until transparent. Then, 0.2 to 0.6 times the mass of diethylphosphorylethyltriethoxysilane in hydrochloric acid solution is added dropwise. The temperature is raised to 75°C, and the reaction is continued with stirring for 5 hours. The ethanol in the system is rapidly distilled off under reduced pressure to obtain a prepolymer solution. The prepolymer solution is mixed with water under stirring at 800 rpm to form an emulsion. Then, ammonia water is added to make the pH of the emulsion reach 10, and the reaction is continued with stirring for 24 hours. After standing and filtration, a white precipitate is obtained. The precipitate is washed twice with water, and the obtained precipitate is placed in an oven and dried at 100°C for 10 hours to obtain flame-retardant microspheres.

[0008] Furthermore, the flame-retardant microspheres have a particle size in the range of 15-20 micrometers.

[0009] Furthermore, the mass ratio of diethylphosphorylethyltriethoxysilane, (4-vinylphenyl)trimethoxysilane, tetraethyl orthosilicate, and polyethylene glycol is 40-60:30-40:160:10-15.

[0010] Furthermore, the concentration of the hydrochloric acid solution is 2 mol / L.

[0011] Furthermore, the mass ratio of the prepolymer solution to water is 1:10 to 14.

[0012] Furthermore, the preparation method of the sheet-like filler is as follows: after hydroxylation treatment, the sheet-like porous carbon is mixed with nickel acetate hexahydrate and deionized water at a mass ratio of 0.1-1:1-5:100, and sonicated at 30-50 kHz for 1-3 hours. Then, 7-10 times the mass of acetic acid hexahydrate is added as a free radical scavenger, and the reaction is carried out under γ-ray irradiation to obtain the product.

[0013] Furthermore, the lamellar porous carbon was prepared according to CN201910619097.7 and then ground to a particle size of 200-500 nm.

[0014] Furthermore, the gamma ray dose is 20 kGy / h, and the irradiation time is 10 h.

[0015] Furthermore, the preparation method of the halogen-free flame-retardant and heat-resistant rubber is as follows: EPDM rubber, vinyl silicone rubber, sulfur, accelerator DCP, accelerator DM, flame-retardant microspheres, sheet filler, and stearic acid are put into an open mill and mixed for 5-10 minutes, then subjected to secondary vulcanization and cooled to room temperature.

[0016] Furthermore, the specific vulcanization process is as follows: vulcanize at 150-170℃ and 8-12MPa for 20-30 minutes, and then place it in an oven at 170-180℃ for a second vulcanization of 4-6 hours.

[0017] Furthermore, the EPDM rubber is Lanxess 5962 from Germany.

[0018] Furthermore, the vinyl silicone rubber has an ethylene content of 0.1–0.3 mol% and a molecular weight of 450,000–700,000.

[0019] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0020] This invention involves hydroxylating lamellar porous carbon, where the hydroxyl groups form adsorption sites. This facilitates the reduction and growth of nano-nickel on the surface and within the pores of the lamellar porous carbon, forming a continuous or semi-continuous metal network. This reduces interference from pores on phonon scattering, lowers interfacial thermal resistance, and, due to the inherent thermal conductivity of nano-nickel, effectively improves the thermal conductivity of the lamellar filler. The lamellar filler is uniformly dispersed in the system in the form of nanosheets and exhibits excellent bonding with the rubber matrix, forming a continuous thermally conductive network within the rubber matrix. By rapidly dissipating internal heat, it avoids segmental oxidative degradation caused by localized temperature rises, delays thermal aging, and improves the thermal stability of the rubber. Simultaneously, the rapid heat dissipation capacity of the lamellar filler lowers the surface temperature of the material, delays thermal decomposition and the release of flammable gases, and improves the flame retardancy of the rubber.

[0021] This invention relates to a novel flame-retardant microsphere preparation technology. This technology involves polymerizing phosphorus-containing silane compounds, double-bonded silane compounds, and tetraethyl orthosilicate to form flame-retardant microspheres rich in silicon (Si) and phosphorus (P). These microspheres exhibit a high char residue rate and can be effectively compounded with sheet-like fillers, significantly improving the char residue rate of cable materials under high-temperature environments. They also rapidly conduct combustion heat, preventing excessive heat accumulation during combustion, reducing free radical reactions, and decreasing toxic gases generated from incomplete combustion, thereby effectively reducing combustion toxicity and producing rubber materials with excellent low-smoke flame-retardant properties.

[0022] This invention incorporates vinyl silicone rubber into ethylene propylene diene monomer (EPDM) rubber, using it in combination with EPDM. The EPDM and vinyl silicone rubber form a three-dimensional interpenetrating network structure, fully leveraging the advantages of both. This invention makes it possible for EPDM and vinyl silicone rubber to crosslink simultaneously without interfering with each other, avoiding the drawback of relying on a single heat-resistant component in existing heat-resistant rubber formulations. It also prevents the failure of heat-resistant components under complex thermal conditions, achieving a highly efficient and complementary heat-resistant effect. Detailed Implementation

[0023] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0024] Example 1

[0025] (1) Diethylphosphoryl ethyltriethoxysilane, (4-vinylphenyl)trimethoxysilane, tetraethyl orthosilicate, and polyethylene glycol were mixed and stirred at 250 rpm until homogeneous. Then, 0.1 times the mass of diethylphosphoryl ethyltriethoxysilane in ethanol was added to disperse it until transparent. Next, 0.2 times the mass of diethylphosphoryl ethyltriethoxysilane in 2 mol / L hydrochloric acid solution was added dropwise. The temperature was raised to 75°C, and the reaction was continued with stirring for 5 hours. The ethanol in the system was then rapidly distilled off under reduced pressure to obtain the prepolymer solution. Under stirring, the prepolymer solution and water were mixed at a mass ratio of 1:10 to form an emulsion. Then, ammonia was added to bring the pH of the emulsion to 10. The reaction was continued for 24 hours. After standing and filtration, a white precipitate was obtained. The precipitate was washed twice with water and then placed in an oven and dried at 100°C for 10 hours to obtain flame-retardant microspheres with a particle size of 15 micrometers. The mass ratio of diethylphosphorylethyltriethoxysilane, (4-vinylphenyl)trimethoxysilane, tetraethyl orthosilicate, and polyethylene glycol was 40:30:160:10.

[0026] (2) Layered porous carbon with a particle size of 200 nm was placed in a mixed solution of hydrogen peroxide and sulfuric acid and sonicated at 30 kHz for 30 min. After sonication, it was treated in a water bath at 50 ℃ for 20 min. It was washed with water 3 times and then washed with anhydrous ethanol 3 times. It was dried at 50 ℃ for 5 h to obtain hydroxylated layered porous carbon. The mass concentration of hydrogen peroxide used was about 30%, the mass concentration of sulfuric acid was about 98%, and the mass ratio of hydrogen peroxide to sulfuric acid was 1:10. The hydroxylated layered porous carbon was mixed with nickel acetate hexahydrate and deionized water at a mass ratio of 0.1:1:100. It was sonicated at 30 kHz for 1 to 3 h. Then, catechin with a mass of 7 times that of acetic acid hexahydrate was added as a free radical scavenger. The reaction was carried out under γ-ray irradiation with a γ-ray dose of 20 KGy / h and an irradiation time of 10 h. After filtration, it was dried at 50 ℃ for 5 h to obtain sheet-like filler.

[0027] (3) 40 parts of EPDM rubber, 15 parts of vinyl silicone rubber, 0.5 parts of sulfur, 0.5 parts of accelerator DCP, 0.5 parts of accelerator DM, 10 parts of flame retardant microspheres, 5 parts of sheet filler and 1 part of stearic acid were put into a two-roll mill for 5 minutes, vulcanized at 150℃ and 8MPa for 20 minutes, and then placed in an oven at 170℃ for a second vulcanization for 4 hours, and cooled to room temperature.

[0028] Example 2

[0029] (1) Diethylphosphoryl ethyltriethoxysilane, (4-vinylphenyl)trimethoxysilane, tetraethyl orthosilicate, and polyethylene glycol were mixed and stirred at 250 rpm until homogeneous. Then, 0.3 times the mass of ethanol (by weight of diethylphosphoryl ethyltriethoxysilane) was added to disperse the mixture until it became transparent. Next, 0.4 times the mass of 2 mol / L hydrochloric acid solution (by weight of diethylphosphoryl ethyltriethoxysilane) was added dropwise. The mixture was heated to 75°C and stirred for 5 hours. The ethanol in the system was then rapidly distilled off under reduced pressure to obtain the prepolymer solution. Under stirring, the prepolymer solution and water were mixed at a mass ratio of 1:12 to form an emulsion. Ammonia was then added to bring the pH of the emulsion to 10. The reaction was continued for 24 hours. After standing and filtration, a white precipitate was obtained. The precipitate was washed twice with water and then placed in an oven and dried at 100°C for 10 hours to obtain flame-retardant microspheres with a particle size of 18 micrometers. The mass ratio of diethylphosphorylethyltriethoxysilane, (4-vinylphenyl)trimethoxysilane, tetraethyl orthosilicate, and polyethylene glycol was 50:35:160:12.

[0030] (2) Layered porous carbon with a particle size of 350 nm was placed in a mixed solution of hydrogen peroxide and sulfuric acid and sonicated at 40 kHz for 60 min. After sonication, it was treated in a water bath at 65 ℃ for 35 min. It was washed with water 3 times and then washed with anhydrous ethanol 3 times. It was dried at 50 ℃ for 5 h to obtain hydroxylated layered porous carbon. The mass concentration of hydrogen peroxide used was about 30%, the mass concentration of sulfuric acid was about 98%, and the mass ratio of hydrogen peroxide to sulfuric acid was 10:1. The hydroxylated layered porous carbon was mixed with nickel acetate hexahydrate and deionized water at a mass ratio of 0.5:3:100. It was sonicated at 40 kHz for 2 h. Then, catechin with a mass of 8 times that of acetic acid hexahydrate was added as a free radical scavenger. The reaction was carried out under γ-ray irradiation. The γ-ray dose was 20 KGy / h and the irradiation time was 10 h. After filtration, it was dried at 50 ℃ for 5 h to obtain sheet-like filler.

[0031] (3) 50 parts of EPDM rubber, 25 parts of vinyl silicone rubber, 1 part of sulfur, 1 part of accelerator DCP, 1 part of accelerator DM, 12 parts of flame retardant microspheres, 7 parts of sheet filler and 3 parts of stearic acid were put into a two-roll mill for 8 minutes, vulcanized at 160℃ and 10MPa for 25 minutes, and then placed in an oven at 175℃ for a second vulcanization for 5 hours, and cooled to room temperature.

[0032] Example 3

[0033] (1) Diethylphosphoryl ethyltriethoxysilane, (4-vinylphenyl)trimethoxysilane, tetraethyl orthosilicate, and polyethylene glycol were mixed and stirred at 250 rpm until homogeneous. Then, 0.5 times the mass of ethanol (by weight of diethylphosphoryl ethyltriethoxysilane) was added to disperse the mixture until it became transparent. Next, 0.6 times the mass of 2 mol / L hydrochloric acid solution (by weight of diethylphosphoryl ethyltriethoxysilane) was added dropwise. The mixture was heated to 75°C and stirred for 5 hours. The ethanol in the system was then rapidly distilled off under reduced pressure to obtain the prepolymer solution. Under stirring, the prepolymer solution and water were mixed at a mass ratio of 1:14 to form an emulsion. Ammonia was then added to bring the pH of the emulsion to 10. The reaction was continued for 24 hours. After standing and filtration, a white precipitate was obtained. The precipitate was washed twice with water and then placed in an oven and dried at 100°C for 10 hours to obtain flame-retardant microspheres with a particle size of 20 micrometers. The mass ratio of diethylphosphorylethyltriethoxysilane, (4-vinylphenyl)trimethoxysilane, tetraethyl orthosilicate, and polyethylene glycol was 60:40:160:15.

[0034] (2) Layered porous carbon with a particle size of 500 nm was placed in a mixed solution of hydrogen peroxide and sulfuric acid and sonicated at 50 kHz for 90 min. After sonication, it was treated in a water bath at 80 ℃ for 50 min. It was washed with water 3 times and then washed with anhydrous ethanol 3 times. It was dried at 50 ℃ for 5 h to obtain hydroxylated layered porous carbon. The mass concentration of hydrogen peroxide used was about 30%, the mass concentration of sulfuric acid was about 98%, and the mass ratio of hydrogen peroxide to sulfuric acid was 10:1. The hydroxylated layered porous carbon was mixed with nickel acetate hexahydrate and deionized water at a mass ratio of 1:5:100. It was sonicated at 50 kHz for 3 h. Then, catechin with a mass of 10 times that of acetic acid hexahydrate was added as a free radical scavenger. The reaction was carried out under γ-ray irradiation. The γ-ray dose was 20 KGy / h and the irradiation time was 10 h. After filtration, it was dried at 50 ℃ for 5 h to obtain sheet-like filler.

[0035] (3) 60 parts of EPDM rubber, 35 parts of vinyl silicone rubber, 1.5 parts of sulfur, 1.5 parts of accelerator DCP, 1.5 parts of accelerator DM, 15 parts of flame retardant microspheres, 10 parts of sheet filler and 5 parts of stearic acid were put into a two-roll mill for 10 min of mixing, vulcanized at 170℃ and 12MPa for 30 min, and then placed in an oven at 180℃ for a second vulcanization for 6 h, and cooled to room temperature.

[0036] Comparative Example 1 (without (4-vinylphenyl)trimethoxysilane)

[0037] (1) Diethylphosphoryl ethyltriethoxysilane, tetraethyl orthosilicate, and polyethylene glycol were mixed and stirred at 250 rpm until homogeneous. Then, 0.5 times the mass of diethylphosphoryl ethyltriethoxysilane in ethanol was added to disperse it until transparent. Then, 0.6 times the mass of diethylphosphoryl ethyltriethoxysilane in 2 mol / L hydrochloric acid solution was added dropwise. The temperature was raised to 75°C and the reaction was continued for 5 h. The ethanol in the system was rapidly distilled off under reduced pressure to obtain a prepolymer solution. The prepolymer solution and water were mixed at a mass ratio of 1:14 under stirring at 800 rpm to form an emulsion. Then, ammonia was added to make the pH of the emulsion reach 10. The reaction was continued for 24 h. After standing and filtration, a white precipitate was obtained. The precipitate was rinsed twice with water and placed in an oven to dry at 100°C for 10 h to obtain flame-retardant microspheres with a particle size of 20 micrometers. The mass ratio of diethylphosphoryl ethyltriethoxysilane, tetraethyl orthosilicate, and polyethylene glycol was 60:160:15.

[0038] (2) Layered porous carbon with a particle size of 500 nm was placed in a mixed solution of hydrogen peroxide and sulfuric acid and sonicated at 50 kHz for 90 min. After sonication, it was treated in a water bath at 80 ℃ for 50 min. It was washed with water 3 times and then washed with anhydrous ethanol 3 times. It was dried at 50 ℃ for 5 h to obtain hydroxylated layered porous carbon. The mass concentration of hydrogen peroxide used was about 30%, the mass concentration of sulfuric acid was about 98%, and the mass ratio of hydrogen peroxide to sulfuric acid was 10:1. The hydroxylated layered porous carbon was mixed with nickel acetate hexahydrate and deionized water at a mass ratio of 1:5:100. It was sonicated at 50 kHz for 3 h. Then, catechin with a mass of 10 times that of acetic acid hexahydrate was added as a free radical scavenger. The reaction was carried out under γ-ray irradiation. The γ-ray dose was 20 KGy / h and the irradiation time was 10 h. After filtration, it was dried at 50 ℃ for 5 h to obtain sheet-like filler.

[0039] (3) 60 parts of EPDM rubber, 35 parts of vinyl silicone rubber, 1.5 parts of sulfur, 1.5 parts of accelerator DCP, 1.5 parts of accelerator DM, 15 parts of flame retardant microspheres, 10 parts of sheet filler and 5 parts of stearic acid were put into a two-roll mill for 10 min of mixing, vulcanized at 170℃ and 12MPa for 30 min, and then placed in an oven at 180℃ for a second vulcanization for 6 h, and cooled to room temperature.

[0040] Comparative Example 2 (without diethylphosphorylethyltriethoxysilane)

[0041] (1) Mix (4-vinylphenyl)trimethoxysilane, tetraethyl orthosilicate, and polyethylene glycol. Stir at 250 rpm until homogeneous. Add 0.5 times the mass of (4-vinylphenyl)trimethoxysilane in ethanol to disperse until transparent. Then, add 0.6 times the mass of (4-vinylphenyl)trimethoxysilane in 2 mol / L hydrochloric acid solution dropwise. Heat to 75°C and continue stirring for 5 hours. Quickly distill off the ethanol in the system under reduced pressure to obtain the prepolymer solution. Under 0 rpm stirring, the prepolymer solution and water were mixed at a mass ratio of 1:14 to form an emulsion. Then, ammonia was added to bring the pH of the emulsion to 10. The reaction was continued for 24 hours. After standing and filtration, a white precipitate was obtained. The precipitate was washed twice with water and then placed in an oven and dried at 100°C for 10 hours to obtain flame-retardant microspheres with a particle size of 20 micrometers. The mass ratio of (4-vinylphenyl)trimethoxysilane, tetraethyl orthosilicate, and polyethylene glycol was 40:160:15.

[0042] (2) Layered porous carbon with a particle size of 500 nm was placed in a mixed solution of hydrogen peroxide and sulfuric acid and sonicated at 50 kHz for 90 min. After sonication, it was treated in a water bath at 80 ℃ for 50 min. It was washed with water 3 times and then washed with anhydrous ethanol 3 times. It was dried at 50 ℃ for 5 h to obtain hydroxylated layered porous carbon. The mass concentration of hydrogen peroxide used was about 30%, the mass concentration of sulfuric acid was about 98%, and the mass ratio of hydrogen peroxide to sulfuric acid was 10:1. The hydroxylated layered porous carbon was mixed with nickel acetate hexahydrate and deionized water at a mass ratio of 1:5:100. It was sonicated at 50 kHz for 3 h. Then, catechin with a mass of 10 times that of acetic acid hexahydrate was added as a free radical scavenger. The reaction was carried out under γ-ray irradiation. The γ-ray dose was 20 KGy / h and the irradiation time was 10 h. After filtration, it was dried at 50 ℃ for 5 h to obtain sheet-like filler.

[0043] (3) 60 parts of EPDM rubber, 35 parts of vinyl silicone rubber, 1.5 parts of sulfur, 1.5 parts of accelerator DCP, 1.5 parts of accelerator DM, 15 parts of flame retardant microspheres, 10 parts of sheet filler and 5 parts of stearic acid were put into a two-roll mill for 10 min of mixing, vulcanized at 170℃ and 12MPa for 30 min, and then placed in an oven at 180℃ for a second vulcanization for 6 h, and cooled to room temperature.

[0044] Comparative Example 3 (without flame-retardant microspheres)

[0045] (1) Layered porous carbon with a particle size of 500 nm was placed in a mixed solution of hydrogen peroxide and sulfuric acid and sonicated at 50 kHz for 90 min. After sonication, it was treated in a water bath at 80 ℃ for 50 min. It was washed with water 3 times and then washed with anhydrous ethanol 3 times. It was dried at 50 ℃ for 5 h to obtain hydroxylated layered porous carbon. The mass concentration of hydrogen peroxide used was about 30%, the mass concentration of sulfuric acid was about 98%, and the mass ratio of hydrogen peroxide to sulfuric acid was 10:1. The hydroxylated layered porous carbon was mixed with nickel acetate hexahydrate and deionized water at a mass ratio of 1:5:100. It was sonicated at 50 kHz for 3 h. Then, catechin with a mass of 10 times that of acetic acid hexahydrate was added as a free radical scavenger. The reaction was carried out under γ-ray irradiation. The γ-ray dose was 20 KGy / h and the irradiation time was 10 h. After filtration, it was dried at 50 ℃ for 5 h to obtain sheet-like filler.

[0046] (2) 60 parts of EPDM rubber, 35 parts of vinyl silicone rubber, 1.5 parts of sulfur, 1.5 parts of accelerator DCP, 1.5 parts of accelerator DM, 10 parts of sheet filler and 5 parts of stearic acid were put into a two-roll mill for 10 min, vulcanized at 170℃ and 12MPa for 30 min, and then placed in an oven at 180℃ for a second vulcanization for 6 h, and cooled to room temperature.

[0047] Comparative Example 4 (using only lamellar porous carbon with a particle size of 500 nm)

[0048] (1) Diethylphosphoryl ethyltriethoxysilane, (4-vinylphenyl)trimethoxysilane, tetraethyl orthosilicate, and polyethylene glycol were mixed and stirred at 250 rpm until homogeneous. Then, 0.5 times the mass of ethanol (by weight of diethylphosphoryl ethyltriethoxysilane) was added to disperse the mixture until it became transparent. Next, 0.6 times the mass of 2 mol / L hydrochloric acid solution (by weight of diethylphosphoryl ethyltriethoxysilane) was added dropwise. The mixture was heated to 75°C and stirred for 5 hours. The ethanol in the system was then rapidly distilled off under reduced pressure to obtain the prepolymer solution. Under stirring, the prepolymer solution and water were mixed at a mass ratio of 1:14 to form an emulsion. Ammonia was then added to bring the pH of the emulsion to 10. The reaction was continued for 24 hours. After standing and filtration, a white precipitate was obtained. The precipitate was washed twice with water and then placed in an oven and dried at 100°C for 10 hours to obtain flame-retardant microspheres with a particle size of 20 micrometers. The mass ratio of diethylphosphorylethyltriethoxysilane, (4-vinylphenyl)trimethoxysilane, tetraethyl orthosilicate, and polyethylene glycol was 60:40:160:15.

[0049] (2) 60 parts of EPDM rubber, 35 parts of vinyl silicone rubber, 1.5 parts of sulfur, 1.5 parts of accelerator DCP, 1.5 parts of accelerator DM, 15 parts of flame retardant microspheres, 10 parts of lamellar porous carbon with a particle size of 500nm and 5 parts of stearic acid were put into an open mill for mixing for 10 minutes, vulcanized at 170℃ and 12MPa for 30 minutes, and then placed in an oven at 180℃ for secondary vulcanization for 6 hours, and cooled to room temperature.

[0050] Comparative Example 5 (without flake filler)

[0051] (1) Diethylphosphoryl ethyltriethoxysilane, (4-vinylphenyl)trimethoxysilane, tetraethyl orthosilicate, and polyethylene glycol were mixed and stirred at 250 rpm until homogeneous. Then, 0.5 times the mass of ethanol (by weight of diethylphosphoryl ethyltriethoxysilane) was added to disperse the mixture until it became transparent. Next, 0.6 times the mass of 2 mol / L hydrochloric acid solution (by weight of diethylphosphoryl ethyltriethoxysilane) was added dropwise. The mixture was heated to 75°C and stirred for 5 hours. The ethanol in the system was then rapidly distilled off under reduced pressure to obtain the prepolymer solution. Under stirring, the prepolymer solution and water were mixed at a mass ratio of 1:14 to form an emulsion. Ammonia was then added to bring the pH of the emulsion to 10. The reaction was continued for 24 hours. After standing and filtration, a white precipitate was obtained. The precipitate was washed twice with water and then placed in an oven and dried at 100°C for 10 hours to obtain flame-retardant microspheres with a particle size of 20 micrometers. The mass ratio of diethylphosphorylethyltriethoxysilane, (4-vinylphenyl)trimethoxysilane, tetraethyl orthosilicate, and polyethylene glycol was 60:40:160:15.

[0052] (2) 60 parts of EPDM rubber, 35 parts of vinyl silicone rubber, 1.5 parts of sulfur, 1.5 parts of accelerator DCP, 1.5 parts of accelerator DM, 15 parts of flame retardant microspheres, and 5 parts of stearic acid were put into a two-roll mill and mixed for 10 minutes. The mixture was then vulcanized at 170°C and 12MPa for 30 minutes. Finally, it was placed in an oven at 180°C for a second vulcanization for 6 hours and cooled to room temperature.

[0053] Performance testing

[0054] (1) Vertical burning time and flame retardant rating

[0055] The vertical burning time (s) was tested according to the test method of GB / T2408—1996, and the flame retardant level was determined based on the measured vertical burning time (s). The sample size was 125mm×12.5mm×1.6mm.

[0056] (2) Oxygen Index %

[0057] According to GB / T2406—1993, the sample size is 85mm×10mm×3.2mm.

[0058] (3) Elongation at break and tear strength

[0059] According to GB / T528—1998, the tensile rate is 500 mm / min.

[0060] Table 1

[0061]

[0062]

[0063] This invention utilizes hydroxylation treatment of lamellar porous carbon to create adsorption sites, promoting the growth of nano-nickel on the surface and within the pores of the porous carbon, forming a metallic network, reducing phonon scattering interference, lowering interfacial thermal resistance, and improving thermal conductivity. The nanosheet filler is uniformly dispersed in the rubber matrix, forming a thermally conductive network for rapid heat conduction, preventing chain segment oxidative degradation, and improving thermal stability and flame retardancy. Simultaneously, this invention also relates to a novel flame-retardant microsphere preparation technology, which uses the polymerization of phosphorus-containing silane compounds to form microspheres rich in Si and P elements, increasing char residue. When combined with lamellar fillers, this improves the char residue of cable materials, rapidly conducts combustion heat, reduces free radical reactions, lowers combustion toxicity, and produces low-smoke flame-retardant rubber materials.

[0064] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No markings in the claims should be construed as limiting the scope of the claims.

Claims

1. A halogen-free flame-retardant and heat-resistant rubber, characterized in that, By weight, it includes 40-60 parts of EPDM rubber, 15-35 parts of vinyl silicone rubber, 0.5-1.5 parts of sulfur, 0.5-1.5 parts of accelerator DCP, 0.5-1.5 parts of accelerator DM, 10-15 parts of flame retardant microspheres, 5-10 parts of sheet filler, and 1-5 parts of stearic acid. The method for preparing the flame-retardant microspheres is as follows: Diethylphosphorylethyltriethoxysilane, (4-vinylphenyl)trimethoxysilane, tetraethyl orthosilicate, and polyethylene glycol are mixed and stirred evenly at 250 rpm. Then, 0.1 to 0.5 times the mass of diethylphosphorylethyltriethoxysilane in ethanol is added to disperse it until transparent. Then, 0.2 to 0.6 times the mass of diethylphosphorylethyltriethoxysilane in hydrochloric acid solution is added dropwise. The temperature is raised to 75°C, and the reaction is continued with stirring for 5 hours. The ethanol in the system is rapidly distilled off under reduced pressure to obtain a prepolymer solution. The prepolymer solution is mixed with water under stirring at 800 rpm to form an emulsion. Then, ammonia water is added to make the pH of the emulsion reach 10. The reaction is continued with stirring for 24 hours. After standing and filtration, a white precipitate is obtained. The precipitate is washed twice with water and placed in an oven to dry at 100°C for 10 hours to obtain flame-retardant microspheres. The flame-retardant microspheres have a particle size in the range of 15-20 micrometers; The mass ratio of diethylphosphorylethyltriethoxysilane, (4-vinylphenyl)trimethoxysilane, tetraethyl orthosilicate, and polyethylene glycol is 40~60:30~40:160:10~15; The concentration of the hydrochloric acid solution is 2 mol / L; The mass ratio of the prepolymer solution to water is 1:10~14; The preparation method of the sheet-like filler is as follows: after hydroxylation treatment, the sheet-like porous carbon is mixed with nickel acetate hexahydrate and deionized water at a mass ratio of 0.1~1:1~5:100, and ultrasonicated for 1~3 hours under the condition of 30~50kHz. Then, 7~10 times the mass of nickel acetate hexahydrate catechin is added as a free radical scavenger, and then the reaction is carried out under γ-ray irradiation to obtain the product. The gamma ray dose was 20 kGy / h, and the irradiation time was 10 h. The preparation method of the halogen-free flame-retardant and heat-resistant rubber is as follows: EPDM rubber, vinyl silicone rubber, sulfur, accelerator DCP, accelerator DM, flame-retardant microspheres, sheet filler, and stearic acid are put into an open mill and mixed for 5-10 minutes, then vulcanized twice and cooled to room temperature. The specific vulcanization process is as follows: vulcanize at 150-170℃ and 8-12MPa for 20-30 minutes, and then place it in an oven at 170-180℃ for a second vulcanization of 4-6 hours.

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