Flame-retardant silicone rubber and method of making

Abstract

This application provides a flame-retardant silicone and its preparation method. In this flame-retardant silicone, through the synergistic effect of boron-containing polysiloxane prepolymer and functionalized boron nitride, the flame-retardant silicone has an afterflame time of ≤5s at 800℃, an oxygen index of ≥36%, and has passed UL94V-0 certification. It can quickly form a ceramic barrier layer at high temperatures, effectively preventing flame propagation. The helical structure of the siloxane main chain, combined with the reinforcing effect of functional fillers such as nano-fumed silica, low-melting-point glass powder, and activated inorganic smoke suppressant and flame retardant, makes the tensile strength of the flame-retardant silicone ≥45N, and the permanent tensile modulus retention rate ≥85% under 125% radial shrinkage, exhibiting excellent tear resistance. This flame-retardant silicone is suitable for applications requiring high flame-retardant performance, such as new energy cables and electronic device protection.

Description

Technical Field

[0001] This invention belongs to the field of flame retardant materials technology, and relates to a flame retardant silicone and its preparation method. Background Technology

[0002] Flame-retardant silicone is a special organic silicone sealing material with added flame retardants. It is mainly used for bonding and sealing electronic components and materials such as metals, plastics, and glass. It is suitable for fields such as wires and cables, power supplies, photovoltaic modules, and communication equipment.

[0003] Traditional flame-retardant silicone materials rely on the addition of bromine- or chlorine-based flame retardants, which can lead to problems such as high-temperature precipitation, equipment corrosion, and the release of toxic fumes. In existing technologies, the additive method easily results in unstable flame-retardant properties and makes it difficult to balance mechanical strength and high-temperature resistance. For example, polyvinyl chloride (PVC) materials produce hydrogen chloride when burning, and liquid flame retardants are prone to causing copper wire sulfidation failure under temperature fluctuations. Therefore, developing a silicone material that requires no external flame retardants and possesses both high thermal stability and environmental friendliness is urgently needed. Summary of the Invention

[0004] The purpose of this invention is to provide a flame-retardant silicone and its preparation method, so as to realize the self-flame-retardant properties of silicone materials at high temperatures by constructing a molecular-level flame-retardant network, while significantly improving mechanical properties and environmental durability.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, this application provides a flame-retardant silicone rubber comprising: methyl vinyl silicone rubber, hydroxyl-terminated polydimethylsiloxane, hydrogen-containing polysiloxane, nano-fumed silica, diphenylsilanediol, boron-containing polysiloxane prepolymer, platinum catalyst, functionalized boron nitride, low-melting-point glass powder, alkynyl alcohol inhibitor, silane coupling agent, and inorganic smoke suppressant and flame retardant.

[0006] Secondly, this application provides a method for preparing flame-retardant silicone, the method comprising: Nano-fumed silica, functionalized boron nitride, low-melting-point glass powder, and inorganic smoke suppressant and flame retardant are activated by silane coupling agents to form activated nano-fumed silica, activated functionalized boron nitride, activated low-melting-point glass powder, and activated inorganic smoke suppressant and flame retardant. Under nitrogen protection, methyl vinyl silicone rubber, hydroxyl-terminated polydimethylsiloxane and diphenylsilanediol are stirred and reacted at 110-120℃ for 2-3 hours to form a prepolymer. The activated nano-fumed silica was added to the prepolymer in batches and mixed well. Then, a silane coupling agent and boron-containing polysiloxane prepolymer were added and reacted under vacuum at 140-150°C for 25-35 minutes to obtain mixture a. After the mixture a is cooled to 50-70℃, the activated functionalized boron nitride, the activated low melting point glass powder, and the activated inorganic smoke suppressant and flame retardant are added and mixed evenly to obtain mixture b; After the mixture b is cooled to 30-50℃, an alkynyl alcohol inhibitor, a hydrogen-containing polysiloxane and a platinum catalyst are added and mixed. The mixture is then vulcanized at 120℃ for 2 hours, 180℃ for 3 hours and 220℃ for 4-6 hours. After hot pressing and irradiation crosslinking, flame-retardant silicone is obtained.

[0007] The present invention has the following beneficial effects: (1) Flame retardant performance: Through the synergistic effect of boron-containing polysiloxane prepolymer and functionalized boron nitride, the flame retardant silicone has an afterflame time of ≤5s at 800℃ and an oxygen index of ≥36%. It has passed UL94V-0 certification and can quickly form a ceramic barrier layer at high temperature, effectively preventing the spread of flame.

[0008] (2) Mechanical strength: The helical structure of the siloxane main chain and the reinforcing effect of functional fillers such as nano-vaporized silica, low melting point glass powder, and activated inorganic smoke suppressant and flame retardant make the tensile strength of flame retardant silicone ≥45N, the permanent tensile modulus retention rate ≥85% under 125% radial shrinkage, and the tear resistance is excellent.

[0009] (3) Environmental stability: No surface corrosion or cracking after 504 hours of salt spray immersion; stable performance in high and low temperature cycle tests from -40℃ to 150℃; smoke release is reduced by more than 75% compared with traditional flame-retardant silicone, and no toxic gas is released.

[0010] (4) The flame-retardant silicone in this application is suitable for applications requiring high flame-retardant performance, such as new energy cables and electronic device protection. Detailed Implementation

[0011] This application provides a flame-retardant silicone rubber, the raw materials for which include: methyl vinyl silicone rubber, hydroxyl-terminated polydimethylsiloxane, hydrogen-containing polysiloxane, nano-fumed silica, diphenylsilanediol, boron-containing polysiloxane prepolymer, platinum catalyst, functionalized boron nitride, low-melting-point glass powder, alkynyl alcohol inhibitor, silane coupling agent and inorganic smoke suppressant and flame retardant.

[0012] Among them, the vinyl content of methyl vinyl silicone rubber is 4.8-5.2%, the degree of polymerization of hydroxyl-terminated polydimethylsiloxane is 8-10, the particle size of nano-fumed silica is 10-40nm, the melting point of low melting point glass powder is 380-430℃, and the platinum content of platinum catalyst is 0.05-0.15%.

[0013] In this application, the method for preparing the boron-containing polysiloxane prepolymer includes: By weight, 40 parts of dimethyldichlorosilane, 25 parts of triethoxyborane, and 50 parts of toluene were placed in a dry reactor. Under nitrogen protection, the reaction was carried out at 60-70°C for 4-5 hours to form a polymer. 30 parts of deionized water were added to the polymer, and the reaction was carried out at 60-70°C for 2-3 hours. After the reaction was completed, the mixture was allowed to stand and separate into layers. The organic phase was then subjected to vacuum distillation to remove toluene and unreacted monomers, yielding a boron-containing polysiloxane prepolymer.

[0014] In this application, the method for preparing functionalized boron nitride includes: By weight, 10 parts of hexagonal boron nitride powder were added to 80 parts of anhydrous ethanol. After ultrasonic dispersion at 40 kHz for 40-50 min, 3-5 parts of silane coupling agent KH-550 were added, and the mixture was refluxed at 80-90 °C for 3-4 h. After the reaction was completed, the reaction product was separated by centrifugation to obtain a precipitate. The precipitate was washed 3-4 times with anhydrous ethanol and then vacuum dried at 100 °C for 12 h to obtain functionalized boron nitride.

[0015] Hydrogen-containing polysiloxanes are organosilicon polymers containing silane-hydrogen bonds. The hydrogen-containing polysiloxanes in this application include poly(methylhydrosiloxane), hydrogen-terminated dimethylmethylhydro (siloxane and polysiloxane), or hydrogen-terminated poly(dimethylsiloxane).

[0016] Under the catalysis of platinum catalyst, the vinyl groups in methyl vinyl silicone rubber can undergo cross-linking reactions with the hydroxyl groups in hydroxyl-terminated polydimethylsiloxane, the hydroxyl groups in boron-containing polysiloxane prepolymer, and the silane-hydrogen bonds in hydrogen-containing polysiloxane to form a continuous and dense three-dimensional network structure.

[0017] The diphenylsilanediol in this application can neutralize the hydroxyl groups in nano-fumed silica, prevent the rubber compound from becoming structured, ensure the long-term softness of the silicone, and facilitate mixing.

[0018] Methyl vinyl silicone rubber and similar materials are prone to premature vulcanization during crosslinking reactions catalyzed by platinum catalysts. Therefore, this application incorporates alkynyl alcohol inhibitors. At room temperature, alkynyl alcohol inhibitors can block the vulcanization reaction, while upon heating, they unblock and solidify, thus facilitating the vulcanization reaction, preventing scorching, and facilitating storage. In this application, the alkynyl alcohol inhibitor is selected from one or more of methylbutynyl alcohol, ethynylcyclohexanol, 3,5-dimethyl-1-hexyn-3-ol, and 3,7,11-trimethyldodecyn-3-ol.

[0019] Silane coupling agents are used to hydrophobically activate the surfaces of inorganic powders such as nano-fumed silica, functionalized boron nitride, low-melting-point glass powder, and inorganic smoke suppressants and flame retardants. This prevents the inorganic powders from agglomerating, precipitating, and delaminating at the interface, improves compatibility with methyl vinyl silicone rubber, and enhances the synergistic effect of flame retardancy. In this application, the silane coupling agent includes one or more of silane coupling agent KH-550, silane coupling agent KH-560, and vinyltrimethoxysilane.

[0020] Inorganic smoke suppressants and flame retardants are functional flame-retardant materials with inorganic compounds such as metal oxides and metal hydrates as their core components. These inorganic smoke suppressants and flame retardants can achieve a V0 flame retardant rating and prevent dripping when low-melting-point glass powder forms a glass phase. In this application, the inorganic smoke suppressant and flame retardant includes ultrafine aluminum hydroxide or ultrafine magnesium hydroxide, and the particle size of this inorganic smoke suppressant and flame retardant is 1-3 μm.

[0021] In this application, the raw materials for preparing flame-retardant silicone rubber include, by weight parts: 100 parts of methyl vinyl silicone rubber, 20-28 parts of hydroxyl-terminated polydimethylsiloxane, 3-8 parts of hydrogen-containing polysiloxane, 15-25 parts of nano-fumed silica, 0.8-2 parts of diphenylsilanediol, 5-12 parts of boron-containing polysiloxane prepolymer, 0.1-0.3 parts of platinum catalyst, 10-20 parts of functionalized boron nitride, 15-25 parts of low-melting-point glass powder, 0.05-0.2 parts of alkynyl alcohol inhibitor, 1.5-3 parts of silane coupling agent, and 8-15 parts of inorganic smoke suppressant and flame retardant.

[0022] This application also provides a method for preparing flame-retardant silicone, the method comprising: S01: Nano-sized fumed silica, functionalized boron nitride, low-melting-point glass powder, and inorganic smoke suppressant and flame retardant are placed separately into a powder mixer. During the mixing process, a silane coupling agent is sprayed to coat the powder surface, completing the surface hydrophobic activation. After spraying, the powder is dried in hot air at 80-90℃ to form activated nano-sized fumed silica, activated functionalized boron nitride, activated low-melting-point glass powder, and activated inorganic smoke suppressant and flame retardant.

[0023] S02: Under nitrogen protection, methyl vinyl silicone rubber, hydroxyl-terminated polydimethylsiloxane and diphenylsilanediol are stirred and reacted at 110-120℃ for 2-3 hours to form a prepolymer.

[0024] S03: Activated nano-fumed silica is added to the prepolymer in batches and mixed thoroughly. Then, a silane coupling agent and boron-containing polysiloxane prepolymer are added and mixed thoroughly. After mixing, a vacuum is applied until the vacuum degree reaches -0.085~-0.095 MPa. The temperature is then raised to 140-150℃, and the reaction is carried out under vacuum for 25-35 minutes to obtain mixture a. Vacuum heating treatment can eliminate moisture, remove small molecules, and prevent foaming and platinum catalyst poisoning.

[0025] S04: When the temperature of mixture a drops to 50-70℃, add activated functionalized boron nitride, activated low melting point glass powder, and activated inorganic smoke suppressant and flame retardant and mix well to ensure that the powder is uniformly dispersed, without agglomeration or sedimentation, to obtain mixture b.

[0026] S05: After mixture b cools to 30-50℃, add an alkynyl alcohol inhibitor and disperse it evenly. Slowly add a hydrogen-containing polysiloxane to disperse the hydrogen groups in advance and avoid local cross-linking reactions. Finally, add a small amount of platinum catalyst in multiple batches and mix well. Then, vulcanize at 120℃ for 2 hours, 180℃ for 3 hours, and 220℃ for 4-6 hours to form a polymer. This polymer is hot-pressed at 170℃, cooled to room temperature, and then cross-linked by irradiation to obtain flame-retardant silicone.

[0027] During the vulcanization process, the active centers of the platinum catalyst selectively activate the vinyl groups on the methyl vinyl silicone rubber molecular chain, the hydroxyl groups on the hydroxyl-terminated polydimethylsiloxane, the silane-hydrogen bonds on the hydrogen-containing polysiloxane, and the active functional groups in the boron-containing polysiloxane prepolymer. This promotes a synergistic cross-linking reaction through covalent bonds, constructing a continuous and dense three-dimensional network. Furthermore, the boron element in the boron-containing polysiloxane prepolymer is uniformly anchored within the network framework through chemical bonds. Under high-temperature conditions, it can directionally decompose to generate a dense boron oxide protective layer, effectively blocking oxygen and heat transfer, and significantly inhibiting flame spread and the continuation of the combustion reaction. In addition, the vulcanization reaction at different temperatures can gradually remove residual hydroxyl groups, low-molecular-weight silicone oil, and inhibitory volatiles, forming a dense and continuous three-dimensional network.

[0028] The purpose of irradiation crosslinking treatment is to further improve the crosslinking density and structural compactness of materials, enhance flame retardancy, mechanical strength, and thermal stability, and ensure the long-term reliability of materials under complex working conditions. The principle of irradiation crosslinking treatment is to utilize the radiation effect of high-energy rays to cause controlled breakage of the material's molecular chains and generate active free radicals. These free radicals then couple to form new covalent bonds, thereby constructing a more compact and stable three-dimensional network structure. In this application, the conditions for irradiation crosslinking treatment are: using 60Co γ-rays as the irradiation source, controlling the irradiation dose at 60-90 kGy, maintaining the irradiation ambient temperature at 25-30℃, and irradiation duration at 15-20 min.

[0029] The technical solution of the present invention will be further explained and described below through specific embodiments.

[0030] Example 1 This application provides a flame-retardant silicone rubber, the raw materials for which are prepared by weight as follows: 100 parts of methyl vinyl silicone rubber with a vinyl content of 4.9%, 25 parts of hydroxyl-terminated polydimethylsiloxane with a degree of polymerization of 9, 5 parts of poly(methylhydrosiloxane), 20 parts of nano-fumed silica with a particle size of 20 nm, 1 part of diphenylsilanediol, 8 parts of boron-containing polysiloxane prepolymer, 0.2 parts of platinum catalyst with a platinum content of 0.08%, 15 parts of functionalized boron nitride, 20 parts of low-melting-point glass powder with a melting point of 390℃, 0.1 parts of methylbutyninol, 2 parts of silane coupling agent KH-550, and 10 parts of ultrafine aluminum hydroxide with a particle size of 1.5 μm.

[0031] This application also provides a method for preparing flame-retardant silicone, the method comprising: S101: Nano-sized fumed silica, functionalized boron nitride, low-melting-point glass powder, and inorganic smoke suppressant and flame retardant are placed separately into a powder mixer. During the mixing process, a silane coupling agent is sprayed to coat the powder surface, completing the surface hydrophobic activation. After spraying, the powder is dried in hot air at 85℃ to form activated nano-sized fumed silica, activated functionalized boron nitride, activated low-melting-point glass powder, and activated inorganic smoke suppressant and flame retardant.

[0032] S102: Under nitrogen protection, methyl vinyl silicone rubber, hydroxyl-terminated polydimethylsiloxane and diphenylsilanediol are stirred and reacted at 115°C for 2 hours to form a prepolymer.

[0033] S103: Activated nano-fumed silica was added to the prepolymer in batches and mixed thoroughly. Then, a silane coupling agent and boron-containing polysiloxane prepolymer were added and mixed thoroughly. After mixing, a vacuum was applied until the vacuum level reached -0.085 MPa. The temperature was then raised to 140°C, and the mixture was reacted under vacuum for 30 minutes to obtain mixture a.

[0034] S104: When the temperature of mixture a drops to 60℃, add activated functionalized boron nitride, activated low melting point glass powder, and activated inorganic smoke suppressant and flame retardant and mix well to ensure that the powder is uniformly dispersed, without agglomeration or sedimentation, to obtain mixture b.

[0035] S105: After mixture b is cooled to 40℃, an alkynyl alcohol inhibitor is added and dispersed evenly. Hydrogen-containing polysiloxane is then slowly added to pre-disperse the hydrogen groups and prevent localized cross-linking reactions. Finally, platinum catalyst is added in small amounts multiple times and mixed thoroughly. The mixture is then vulcanized successively at 120℃ for 2 hours, 180℃ for 3 hours, and 220℃ for 5 hours to form a polymer. This polymer is hot-pressed at 170℃, cooled to room temperature, and then cross-linked by irradiation to obtain flame-retardant silicone.

[0036] Example 2 This application provides a flame-retardant silicone rubber, the raw materials for which are prepared by weight as follows: 100 parts of methyl vinyl silicone rubber with a vinyl content of 4.8%, 20 parts of hydroxyl-terminated polydimethylsiloxane with a degree of polymerization of 10, 3 parts of hydrogen-capped dimethyl methyl hydrogen (siloxane and polysiloxane), 15 parts of nano-fumed silica with a particle size of 40 nm, 0.8 parts of diphenylsilanediol, 12 parts of boron-containing polysiloxane prepolymer, 0.3 parts of platinum catalyst with a platinum content of 0.05%, 10 parts of functionalized boron nitride, 15 parts of low-melting-point glass powder with a melting point of 380℃, 0.05 parts of acetylenecyclohexanol, 1.5 parts of silane coupling agent KH-560, and 8 parts of ultrafine magnesium hydroxide with a particle size of 1 μm.

[0037] This application also provides a method for preparing flame-retardant silicone, which is the same as in Example 1.

[0038] Example 3 This application provides a flame-retardant silicone rubber, the raw materials for which are prepared by weight as follows: 100 parts of methyl vinyl silicone rubber with a vinyl content of 5.2%, 25 parts of hydroxyl-terminated polydimethylsiloxane with a degree of polymerization of 9, 4 parts of hydrogen-terminated poly(dimethylsiloxane), 20 parts of nano-fumed silica with a particle size of 30 nm, 1.2 parts of diphenylsilanediol, 10 parts of boron-containing polysiloxane prepolymer, 0.1 parts of platinum catalyst with a platinum content of 0.15%, 18 parts of functionalized boron nitride, 25 parts of low-melting-point glass powder with a melting point of 430℃, 0.2 parts of 3,5-dimethyl-1-hexyn-3-ol, 3 parts of vinyltrimethoxysilane, and 12 parts of ultrafine aluminum hydroxide with a particle size of 3 μm.

[0039] This application also provides a method for preparing flame-retardant silicone, which is the same as in Example 1.

[0040] Example 4 This application provides a flame-retardant silicone rubber, the raw materials for which are prepared by weight as follows: 100 parts of methyl vinyl silicone rubber with a vinyl content of 5.2%, 22 parts of hydroxyl-terminated polydimethylsiloxane with a degree of polymerization of 9, 4 parts of poly(methylhydrosiloxane), 18 parts of nano-fumed silica with a particle size of 25 nm, 1.8 parts of diphenylsilanediol, 9 parts of boron-containing polysiloxane prepolymer, 0.15 parts of platinum catalyst with a platinum content of 0.1%, 18 parts of functionalized boron nitride, 20 parts of low-melting-point glass powder with a melting point of 390 °C, 0.18 parts of methylbutyninol, 2.5 parts of vinyltrimethoxysilane, and 10 parts of ultrafine aluminum hydroxide with a particle size of 2 μm.

[0041] This application also provides a method for preparing flame-retardant silicone, which is the same as in Example 1.

[0042] The flame-retardant silicone prepared in Examples 1-4 were tested for flame retardant properties, burning rate, tensile strength, tear strength, salt spray immersion, and high and low temperature cycling, respectively. The test results are shown in Table 1.

[0043] Table 1: Performance Test Results The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A flame-retardant silicone rubber, characterized in that, The raw materials for preparing the flame-retardant silicone include: methyl vinyl silicone rubber, hydroxyl-terminated polydimethylsiloxane, hydrogen-containing polysiloxane, nano-fumed silica, diphenylsilanediol, boron-containing polysiloxane prepolymer, platinum catalyst, functionalized boron nitride, low-melting-point glass powder, alkynyl alcohol inhibitors, silane coupling agents, and inorganic smoke suppressants and flame retardants.

2. The flame-retardant silicone rubber according to claim 1, characterized in that, The raw materials for preparing the flame-retardant silicone rubber include, by weight, 100 parts of methyl vinyl silicone rubber, 20-28 parts of hydroxyl-terminated polydimethylsiloxane, 3-8 parts of hydrogen-containing polysiloxane, 15-25 parts of nano-fumed silica, 0.8-2 parts of diphenylsilanediol, 5-12 parts of boron-containing polysiloxane prepolymer, 0.1-0.3 parts of platinum catalyst, 10-20 parts of functionalized boron nitride, 15-25 parts of low-melting-point glass powder, 0.05-0.2 parts of alkynyl alcohol inhibitor, 1.5-3 parts of silane coupling agent, and 8-15 parts of inorganic smoke suppressant and flame retardant.

3. The flame-retardant silicone rubber according to claim 1, characterized in that, The methyl vinyl silicone rubber has a vinyl content of 4.8-5.2%; the hydroxyl-terminated polydimethylsiloxane has a degree of polymerization of 8-10; the nano-sized fumed silica has a particle size of 10-40 nm; and the low-melting-point glass powder has a melting point of 380-430 °C.

4. The flame-retardant silicone rubber according to claim 1, characterized in that, The method for preparing the boron-containing polysiloxane prepolymer includes: Under nitrogen protection, dimethyldichlorosilane, triethoxyborane and toluene react at 60-70°C for 4-5 hours to form a polymer. The polymer was hydrolyzed, allowed to stand for separation, and then distilled under reduced pressure to obtain a boron-containing polysiloxane prepolymer.

5. The flame-retardant silicone rubber according to claim 1, characterized in that, The preparation method of the functionalized boron nitride includes: adding hexagonal boron nitride powder to anhydrous ethanol, dispersing it ultrasonically, adding a silane coupling agent, refluxing at 80-90℃ for 3-4 hours, and then centrifuging, washing with anhydrous ethanol, and vacuum drying to obtain functionalized boron nitride.

6. The flame-retardant silicone rubber according to claim 1, characterized in that, The hydrogen-containing polysiloxanes include poly(methylhydrosiloxane), hydrogen-terminated dimethylmethylhydro (siloxane and polysiloxane), or hydrogen-terminated poly(dimethylsiloxane).

7. The flame-retardant silicone rubber according to claim 1, characterized in that, The alkynol inhibitors include one or more of methylbutynol, ethynylcyclohexanol, 3,5-dimethyl-1-hexyn-3-ol, and 3,7,11-trimethyldodecyn-3-ol.

8. The flame-retardant silicone rubber according to claim 1, characterized in that, The silane coupling agent includes one or more of silane coupling agent KH-550, silane coupling agent KH-560, and vinyltrimethoxysilane.

9. The flame-retardant silicone rubber according to claim 1, characterized in that, The inorganic smoke suppressant and flame retardant includes ultrafine aluminum hydroxide or ultrafine magnesium hydroxide, and the particle size of the inorganic smoke suppressant and flame retardant is 1-3 μm.

10. The method for preparing flame-retardant silicone according to any one of claims 1-9, characterized in that, include: Nano-fumed silica, functionalized boron nitride, low-melting-point glass powder, and inorganic smoke suppressant and flame retardant are activated by silane coupling agents to form activated nano-fumed silica, activated functionalized boron nitride, activated low-melting-point glass powder, and activated inorganic smoke suppressant and flame retardant. Under nitrogen protection, methyl vinyl silicone rubber, hydroxyl-terminated polydimethylsiloxane and diphenylsilanediol are stirred and reacted at 110-120℃ for 2-3 hours to form a prepolymer. The activated nano-fumed silica was added to the prepolymer in batches and mixed well. Then, a silane coupling agent and boron-containing polysiloxane prepolymer were added and reacted under vacuum at 140-150°C for 25-35 minutes to obtain mixture a. After the mixture a is cooled to 50-70℃, the activated functionalized boron nitride, the activated low melting point glass powder, and the activated inorganic smoke suppressant and flame retardant are added and mixed evenly to obtain mixture b; After the mixture b is cooled to 30-50℃, an alkynyl alcohol inhibitor, a hydrogen-containing polysiloxane and a platinum catalyst are added and mixed. The mixture is then vulcanized at 120℃ for 2 hours, 180℃ for 3 hours and 220℃ for 4-6 hours. After hot pressing and irradiation crosslinking, flame-retardant silicone is obtained.

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