High-efficiency flame-retardant low-toxic-gas-release silicone rubber composite material and preparation method thereof

Abstract

The invention belongs to the technical field of polymer composite materials, and particularly relates to an efficient flame-retardant low-toxic-gas-release silicone rubber composite material and a preparation method thereof. The high-efficiency flame-retardant low-toxic-gas-release silicone rubber composite material comprises the following components in parts by weight: 100 parts of methyl vinyl silicone rubber; 10 to 20 parts of ZIF-67 modified by polysiloxane; 5-10 parts of modified nano molybdenum oxide; 5 to 10 parts of melamine cyanurate; 40 to 50 parts of mesoporous SiO2 aerogel; 1-3 parts of hydroxyl silicone oil; 0.5 to 1.5 parts of a vulcanizing agent; and 0-5 parts of an auxiliary agent. The flame-retardant and smoke-suppression performance of the silicone rubber composite material is remarkably improved through material technology innovation, and meanwhile, the mechanical property and the high temperature resistance are improved.

Description

Technical Field

[0001] This invention belongs to the field of polymer composite materials technology, specifically relating to a highly efficient flame-retardant and low-toxicity gas-release silicone rubber composite material and its preparation method. Background Technology

[0002] Silicone rubber is widely used in electronics, aerospace, automotive, and medical devices due to its excellent resistance to high and low temperatures, electrical insulation, and physiological inertness. However, silicone rubber has a low limiting oxygen index (LOI) (approximately 24%), making it a flammable material. Furthermore, it produces large amounts of smoke and toxic gases (such as CO and HCN) during combustion, posing significant safety hazards.

[0003] Currently, the flame retardant modification of silicone rubber mainly adopts the following methods: 1. Adding inorganic hydroxides (such as aluminum hydroxide and magnesium hydroxide): High addition amounts (usually exceeding 30% phr) are required to achieve a certain flame retardant effect, but this will seriously degrade the mechanical properties and processing fluidity of the material; 2. Using platinum-based catalysts: Flame retardancy is achieved by catalyzing the cross-linking of silicone rubber to form a dense carbon layer, but the cost is high and the smoke suppression effect is limited; 3. Halogenated flame retardants: Although they are highly efficient, their use has been restricted in most countries and regions because they produce highly toxic substances such as dioxins during combustion; 4. Intumescent flame retardants (IFR): They are widely used in polyolefins, but they have poor compatibility with silicone rubber, are prone to migration and precipitation, and affect long-term stability.

[0004] Metal-organic frameworks (MOFs) are a class of crystalline porous materials formed by the self-assembly of metal ions / clusters and organic ligands, possessing high specific surface area, tunable pore size, and diverse functional groups. In recent years, MOFs have made significant progress in applications such as catalysis, gas adsorption / separation, and drug delivery, and their application in flame retardancy of polymer materials is also beginning to be explored. The flame retardant mechanisms of MOFs mainly include: catalytic char formation: metal nodes (such as Co, Zn, and Zr) are converted into metal oxides at high temperatures, catalyzing polymer crosslinking to form a dense char layer; free radical quenching: organic ligands containing N and P decompose to release free radicals, interrupting the combustion chain reaction; and physical adsorption: the porous structure adsorbs combustible small molecules and smoke particles, reducing smoke density and toxic gas release. However, directly applying MOFs to silicone rubber flame retardancy faces significant challenges: 1. Dispersion issues: MOF-modified nanoparticles are prone to agglomeration, making it difficult to uniformly disperse in a hydrophobic silicone rubber matrix; 2. Poor interfacial compatibility: MOFs have high surface polarity and lack interaction with silicone rubber molecular chains, resulting in weak interfacial bonding; 3. Insufficient processing stability: High temperatures and high shear forces during silicone rubber processing can easily damage the crystal structure and pores of MOFs; 4. Limited functionality: A single MOF cannot simultaneously meet the multiple requirements of high-efficiency flame retardancy, smoke suppression, and toxicity reduction.

[0005] Therefore, developing a new technology that can overcome the above bottlenecks, enable the efficient and stable application of MOFs in silicone rubber, and also possess excellent flame retardant and smoke-suppressing properties is of great scientific significance and engineering value. Summary of the Invention

[0006] The purpose of this invention is to provide a highly efficient flame-retardant silicone rubber composite material with low toxic gas release and its preparation method.

[0007] To achieve the above objectives, the present invention provides the following technical solution: A highly efficient flame-retardant and low-toxic-gas-emission silicone rubber composite material comprises the following components by weight: 100 parts methyl vinyl silicone rubber; 10-20 parts polysiloxane-modified ZIF-67; 5-10 parts modified nano molybdenum oxide; 5-10 parts melamine cyanurate; 40-50 parts mesoporous SiO2 aerogel; 1-3 parts hydroxyl silicone oil; 0.5-1.5 parts vulcanizing agent; and 0-5 parts additives.

[0008] Preferably, the preparation method of the polysiloxane-modified ZIF-67 includes the following steps: (1) Dissolve 2-aminoterephthalic acid in N,N-dimethylformamide and cobalt nitrate hexahydrate in methanol. After mixing, react, wash, collect the solid by centrifugation, and dry to obtain NH2-ZIF-67 powder. (2) KH-560, sodium dodecyl sulfate, n-hexadecane and azobisisobutyronitrile are mixed and reacted to obtain EP-PSO emulsion; (3) Disperse NH2-ZIF-67 in N,N-dimethylformamide, add EP-PSO emulsion, and react; (4) After the reaction is completed, the polysiloxane-modified ZIF-67 is obtained by centrifugation, washing and vacuum drying.

[0009] Preferably, the ratio of the number of moles of epoxy groups in the EP-PSO emulsion to the number of moles of amino groups in NH2-ZIF-67 is 2:1 to 3:1.

[0010] Preferably, the preparation method of the modified nano-molybdenum oxide includes the following steps: (1) The dried molybdenum oxide was added to anhydrous xylene, and then triethoxysilane was added. The mixture was heated and reacted. After the reaction was completed, the mixture was cooled, centrifuged, and the solid was collected, washed, and dried under vacuum to obtain Si-H modified molybdenum oxide. (2) Si-H modified molybdenum oxide was dispersed in anhydrous xylene, vinyl-terminated dimethyl polysiloxane was added, nitrogen gas was introduced, platinum catalyst was added, and the reaction was heated. After the reaction was completed, it was cooled to room temperature, washed, and dried to obtain modified molybdenum oxide.

[0011] Molybdenum oxide possesses flame-retardant and smoke-suppressing properties, and can also improve the thermal stability of composite materials. However, molybdenum oxide particles are prone to agglomeration in the silicone rubber matrix, forming stress concentration points. The weak van der Waals forces between molybdenum oxide and silicone rubber prevent the effective transfer of external forces from the soft polymer matrix to the rigid filler particles. When subjected to external forces, the agglomerated molybdenum oxide particles become crack initiation points, leading to premature material fracture. This invention modifies molybdenum oxide to improve its dispersibility in silicone rubber and enhance its interfacial bonding with the silicone rubber matrix, thereby improving the high-temperature resistance of silicone rubber composite materials, especially their tensile strength at high temperatures.

[0012] Preferably, the mass ratio of Si-H modified molybdenum oxide to vinyl-terminated dimethyl polysiloxane is 1:(2-5).

[0013] Preferably, the amount of catalyst used is 50-100 ppm based on platinum metal, which is the mass of vinyl-terminated dimethyl polysiloxane.

[0014] Preferably, the molecular weight (Mw) of the vinyl-terminated dimethyl polysiloxane is 1800-2200.

[0015] Preferably, the mass ratio of methyl vinyl silicone rubber, polysiloxane modified ZIF-67, and modified nano molybdenum oxide is 100:(14-16):(5-7).

[0016] When methyl vinyl silicone rubber, polysiloxane-modified ZIF-67, and modified nano-molybdenum oxide are added in specific proportions, the elongation at break of silicone rubber composites at high temperatures can be significantly improved. This is because the main chain of silicone rubber has a compliant Si-O-Si structure, and its strength decreases at high temperatures primarily due to the excessive mobility of molecular chain segments, making them more prone to slippage. However, when the three raw materials are in a specific proportion, ZIF-67, with its regular pore structure and unsaturated metal sites, allows these broken coordination bonds to potentially reform elsewhere at high temperatures, forming a dynamic and reversible cross-linked network. Simultaneously, the cross-linking effect of modified molybdenum oxide, the dynamic properties of ZIF-67, and the flexibility of silicone rubber achieve an optimal balance. The material transforms from a "easy slippage-easy breakage" mode at high temperatures to a "high energy consumption-controlled deformation" mode, thereby improving the elongation at break at high temperatures.

[0017] Preferably, the additives include at least one of structure control agents and heat-resistant additives.

[0018] This invention provides a method for preparing the aforementioned high-efficiency flame-retardant and low-toxicity gas-emission silicone rubber composite material, comprising the following steps: (1) Pretreatment: The mesoporous SiO2 aerogel is dried to remove adsorbed water; (2) Initial mixing: methyl vinyl silicone rubber is rolled on a two-roll mill with hydroxyl silicone oil, PSi@ZIF-67, modified nano MoO3, MCA, mesoporous SiO2 aerogel and additives added in sequence, and mixed until evenly dispersed; (3) Final mixing: Continue to add vulcanizing agent bis(25) and continue mixing to obtain compound rubber; (4) Vulcanization molding: The compound rubber is subjected to first-stage vulcanization and second-stage vulcanization in sequence; (5) Post-processing: After vulcanization, the sample is taken out and cooled to obtain a high-efficiency flame-retardant silicone rubber composite material with low toxic gas release.

[0019] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows: 1. This invention provides a highly efficient flame-retardant and low-toxic-gas-release silicone rubber composite material and its preparation method. Through material innovation, the flame-retardant and smoke-suppressing performance of the silicone rubber composite material is significantly improved. For the first time, polysiloxane is used to modify the surface of ZIF-67 metal-organic frameworks (MOFs), effectively improving the dispersion and interfacial compatibility of MOFs in the silicone rubber matrix and inhibiting agglomeration. Furthermore, PSi@ZIF-67 is compounded with modified nano-MoO3 and melamine cyanurate (MCA) to construct a highly efficient flame-retardant and smoke-suppressing system with synergistic "condensed phase-gas phase" action. This fully utilizes the flame-retardant mechanisms of each component at different combustion stages, significantly improving the overall fire resistance of the material.

[0020] 2. The silicone rubber composite material obtained by this invention achieves a breakthrough in performance. While maintaining good mechanical and processing properties, it achieves a flame retardant rating of UL-94 V-0, a significantly improved limiting oxygen index (LOI), a substantial reduction in smoke density rating (SDR), and a marked decrease in heat release rate and total smoke release. The content of toxic gases (such as CO and HCN) released during the material's combustion process is significantly reduced, exhibiting advantages such as low smoke, low toxicity, halogen-free, and environmentally friendly characteristics. This aligns with the development trend of modern green flame-retardant materials and stringent fire safety standards.

[0021] 3. This invention expands the application boundaries of MOFs materials in the field of polymer flame retardancy, providing an efficient solution to the technical challenges of traditional silicone rubber, such as flammability, high smoke production, and high smoke toxicity. The prepared composite material can be widely used in high-end flame-retardant cable insulation layers, electronic and electrical device packaging materials, aerospace sealing components, and rail transit interior components, which have extremely high requirements for fire safety performance, demonstrating significant social benefits and broad application prospects.

[0022] 4. This invention improves the mechanical properties and high-temperature resistance of silicone rubber composites by modifying molybdenum oxide and compounding methyl vinyl silicone rubber, PSi@ZIF-67, and modified nano-MoO3 in a specific ratio in the system.

[0023] 5. This silicone rubber composite material achieves high-efficiency flame retardancy and low smoke and low toxicity through multi-component synergistic design. Methyl vinyl silicone rubber serves as the matrix, while polysiloxane-modified ZIF-67 combines catalytic char formation with the release of inert gases for gas-phase flame retardancy, simultaneously improving compatibility. Modified nano-molybdenum oxide promotes cross-linking and char formation, enhances the density of the char layer, and inhibits the release of pyrolysis volatiles. The compounding of each component significantly reduces heat release and the generation of toxic gases, achieving a balance between high-efficiency flame retardancy and environmental safety. Detailed Implementation

[0024] The technical solutions in the embodiments of the present invention will be clearly and completely described below. 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 skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] Example 1 This embodiment provides polysiloxane-modified ZIF-67 (PSi@ZIF-67), including the following steps: (1) Dissolve 170 mg of 2-aminoterephthalic acid in 70 mL of N,N-dimethylformamide and 500 mg of cobalt nitrate hexahydrate in 20 mL of methanol. After mixing, react at 120 °C for 4 h. Wash the mixture three times each with methanol and deionized water, collect the solid by centrifugation, and dry it in an oven at 80 °C for 12 h to obtain NH2-ZIF-67 powder. (2) Epoxy-containing polysiloxane (EP-PSO) was synthesized by fine emulsion polymerization. Specifically, GPTMS (KH-560) was used as the main monomer, sodium dodecyl sulfate as the emulsifier, n-hexadecane as the stabilizer, and azobisisobutyronitrile as the initiator. The reaction was carried out at 70°C and under N2 protection for 5 hours to obtain EP-PSO emulsion. (3) Take 50 mg of NH2-ZIF-67 powder and disperse it in 40 mL of N,N-dimethylformamide. Sonicate for 30 min to form a uniform suspension. Take EP-PSO emulsion containing 0.15 mmol of epoxy group. Add EP-PSO emulsion dropwise to the suspension and stir magnetically at 60 °C for 24 h. (4) After the reaction was completed, the solid was collected by centrifugation, washed three times with N,N-dimethylformamide and three times with methanol; dried under vacuum at 60°C for 12 h to obtain polysiloxane modified ZIF-67 (denoted as PSi@ZIF-67).

[0026] Examples 2-4: Preparation of silicone rubber composite materials Prepare silicone rubber composite materials according to the formulations shown in Table 1 (parts by weight): Table 1. Formulation composition (parts) of Examples 2-4 The chemical name of the bis(2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane is: 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane.

[0027] The preparation method of the modified nano-molybdenum oxide includes the following steps: (1) Place molybdenum oxide powder in a vacuum drying oven and dry it at 120°C for 10 h. Under a nitrogen atmosphere, add 1.0 g of dried molybdenum oxide to 80 mL of anhydrous xylene and add 1.0 mL of triethoxysilane. Heat to 135°C and react under reflux for 10 h. After the reaction is complete, cool, centrifuge, collect the solid, wash it 3 times with anhydrous xylene and then wash it 2 times with anhydrous ethanol. Dry it under vacuum at 60°C for 6 h to obtain Si-H modified molybdenum oxide. (2) 1.0 g of Si-H modified molybdenum oxide was dispersed in 30 mL of anhydrous xylene, 3.0 g of vinyl-terminated dimethyl polysiloxane was added, nitrogen gas was introduced, and a platinum catalyst was added. The platinum catalyst was a caster catalyst, and the amount of platinum was 70 ppm of the mass of vinyl-terminated dimethyl polysiloxane. The reaction was carried out at 80 °C for 7 h. After the reaction was completed, the mixture was cooled to room temperature, transferred to a centrifuge tube, centrifuged at 8000 rpm for 15 min, the supernatant was discarded, xylene was added to the centrifuge tube, and the mixture was sonicated at a power density of 200 W / L for 15 min. The mixture was then centrifuged again, and the process was repeated 3 times. The solid product was vacuum dried at 60 °C for 12 h to obtain modified molybdenum oxide.

[0028] The preparation method of the high-efficiency flame-retardant and low-toxic gas-release silicone rubber composite material includes the following steps: (1) Pretreatment: The mesoporous SiO2 aerogel was dried at 120℃ for 2h to remove adsorbed water; (2) Initial mixing: Methyl vinyl silicone rubber is mixed in a mixer, and hydroxyl silicone oil, PSi@ZIF-67, modified nano MoO3, MCA and mesoporous SiO2 aerogel are added in sequence. The mixture is mixed at 50°C for 2 hours to ensure that the filler is evenly dispersed. (3) Final mixing: Continue to add vulcanizing agent bis(25) and continue mixing for 5 minutes to obtain the compound; (4) Vulcanization molding: The compound rubber is placed in the mold and vulcanized for 2 minutes at a pressure of 10 MPa and a temperature of 206℃. After demolding and cooling, a high-efficiency flame-retardant and low-toxicity silicone rubber composite material can be obtained. Comparative Example 1: Unmodified ZIF-67 silicone rubber The difference between this comparative example and Example 3 is that PSi@ZIF-67 is replaced with an equal amount of ZIF-67.

[0029] The preparation method of ZIF-67 includes the following steps: 2-aminoterephthalic acid (170 mg) is dissolved in 70 mL of N,N-dimethylformamide, and cobalt nitrate hexahydrate (500 mg) is dissolved in 20 mL of methanol. After mixing, the mixture is reacted at 120 °C for 4 h. The mixture is washed three times each with methanol and deionized water, and the solid is collected by centrifugation and dried in an oven at 80 °C for 12 h to obtain ZIF-67.

[0030] The polysiloxane-modified ZIF-67 is prepared by surface modification of ZIF-67 metal-organic framework material with polysiloxane, which improves the dispersibility and interfacial compatibility of ZIF-67 metal-organic framework material in silicone rubber matrix, thereby inhibiting agglomeration.

[0031] Comparative Example 2: MOF-free silicone rubber The difference between this comparative example and Example 3 is that PSi@ZIF-67 is not added.

[0032] Comparative Example 3: Commercial Flame-Retardant Silicone Rubber The difference between this comparative example and Example 3 is that it uses a commercially available halogen-free flame-retardant silicone rubber product.

[0033] Comparative Example 4 This comparative example is the product of Example 1 in the methyl vinyl silicone rubber and its preparation method provided by Chinese Patent CN112795197B.

[0034] Comparative Example 5 The difference between this comparative example and Example 3 is that the preparation method of the modified nano molybdenum oxide includes the following steps: molybdenum oxide powder is placed in a vacuum drying oven and dried at 120°C for 10 hours. Under a nitrogen atmosphere, 1.0 g of dried molybdenum oxide is added to 80 mL of anhydrous xylene, and 1.0 mL of triethoxysilane is added. The temperature is raised to 135°C and reacted under reflux for 10 hours. After the reaction is completed, the mixture is cooled, centrifuged, and the solid is collected. The solid is washed three times with anhydrous xylene and then twice with anhydrous ethanol. The solid is then dried under vacuum at 60°C for 6 hours to obtain modified molybdenum oxide.

[0035] Comparative Example 6 The difference between this comparative example and Example 3 is that the molecular weight (Mw) of the vinyl-terminated dimethyl polysiloxane is 1000.

[0036] Comparative Example 7 The difference between this comparative example and Example 3 is that the molecular weight (Mw) of the vinyl-terminated dimethyl polysiloxane is 3000.

[0037] Comparative Example 8 The difference between this comparative example and Example 3 is that 100 parts by weight of methyl vinyl silicone rubber, 15 parts by weight of PSi@ZIF-67, and 5 parts by weight of modified nano MoO3 are replaced with 100 parts by weight of methyl vinyl silicone rubber, 10 parts by weight of PSi@ZIF-67, and 10 parts by weight of modified nano MoO3.

[0038] Performance testing 1. The following performance tests were performed on the silicone rubber materials of Examples 2-4 and Comparative Examples 1-3: Limiting oxygen index (LOI): Tested according to GB / T10707-2008 standard; Flame retardancy UL-94: Tested according to ANSI / UL94-2013 standard; Heat release: Tested using a cone calorimeter (radiant power 35kW / m²) according to ISO 5660-1 standard; Smoke density: Tested according to GB / T8323.2-2008 standard; CO release: Analysis was performed using a flue gas toxicity analyzer coupled with FTIR; Mechanical properties: tested according to GB / T528-2009 standard.

[0039] The results are shown in Table 2.

[0040] Table 2 Performance test results of silicone rubber materials Note: LOI is the limiting oxygen index; THR is the total heat release; pHRR is the peak heat release rate; DS is the constant tensile stress.

[0041] Examples 2-4 all achieved UL-94V-0 rating with an LOI value exceeding 30%, significantly better than comparative examples 2-3. This indicates a clear synergistic flame-retardant effect between PSi@ZIF-67 and modified nano-MoO3 and MCA.

[0042] The tensile strength and elongation at break of Examples 2-4 both exceeded 9.0 MPa and 280%, respectively, which were much higher than the 6.5 MPa and 210% of Comparative Example 1 (unmodified ZIF-67). This demonstrates that polysiloxane modification significantly improves the compatibility and dispersibility of ZIF-67 in silicone rubber without reducing the tensile strength and elongation at break of silicone rubber.

[0043] The reductions in pHRR, THR, DS, and CO in Examples 2-4 were significantly greater than those in Comparative Examples 2-3, indicating that MOFs materials play a crucial role in smoke suppression.

[0044] 2. Hot air aging: Aging at 230℃ for 80 hours.

[0045] Change rate of tensile strength after aging = (tensile strength after aging - tensile strength before aging) ÷ tensile strength before aging * 100%.

[0046] Change rate of elongation at break after aging = (elongation at break after aging - elongation at break before aging) ÷ elongation at break before aging * 100%.

[0047] The results are shown in Table 3.

[0048] Table 3 High Temperature Resistance Test Results As shown in Table 3, the heat resistance of Example 3 is better than that of Examples 2 and 4, and significantly better than that of Comparative Example 8, indicating that the ratio of methyl vinyl silicone rubber, PSi@ZIF-67, and modified nano MoO3 in the system has an important influence on the heat resistance of the silicone rubber composite material.

[0049] Comparative Examples 5-7 show that the modification of MoO3 has a significant impact on the tensile strength of silicone rubber composites. Furthermore, the results indicate that the molecular weight of vinyl-terminated dimethyl polysiloxane affects the product's performance. The analysis shows that if the molecular weight of vinyl-terminated dimethyl polysiloxane is too low, each chain is too short, resulting in weak entanglement with the silicone rubber matrix; if the molecular weight is too high, the grafting density is low due to steric hindrance, leading to poor modification effect.

[0050] Comparative Examples 3 and 4 show that the product of Example 3 exhibits superior heat resistance compared to commercially available products and existing technologies. Although the elongation at break at room temperature exceeds 400% in existing technologies, the product of this invention maintains excellent mechanical properties even at high temperatures, with its elongation at break remaining consistently above 200%. Therefore, the product of this invention is more suitable for applications requiring high mechanical properties, high-temperature resistance, and a certain level of high-temperature ductility, such as high-temperature seals (e.g., engine seals, automotive turbocharger pipes), high-temperature protective clothing, insulating components for electric heating appliances, flexible heat-resistant materials for aerospace applications, and high-temperature conveyor belts—components that are exposed to hot and oxygen environments for extended periods and require deformation. In these applications, the high-temperature stability of the material is more critical than its ultra-high elongation at room temperature. This invention, while ensuring sufficient elongation at break, significantly improves heat aging resistance and service life, demonstrating superior overall application value.

[0051] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A highly efficient flame-retardant, low-toxicity gas-emission silicone rubber composite material, characterized in that, The product comprises, by weight, 100 parts of methyl vinyl silicone rubber; 10-20 parts of polysiloxane-modified ZIF-67; 5-10 parts of modified nano-molybdenum oxide; 5-10 parts melamine cyanurate; 40-50 parts mesoporous SiO2 aerogel; 1-3 parts hydroxyl silicone oil; 0.5-1.5 parts vulcanizing agent; 0-5 parts additives. The polysiloxane-modified ZIF-67 is prepared by surface modification of ZIF-67 metal-organic framework material with polysiloxane, which improves the dispersibility and interfacial compatibility of ZIF-67 metal-organic framework material in silicone rubber matrix, thereby inhibiting agglomeration.

2. The high-efficiency flame-retardant and low-toxicity gas-emission silicone rubber composite material according to claim 1, characterized in that, The preparation method of the polysiloxane-modified ZIF-67 includes the following steps: (1) Dissolve 2-aminoterephthalic acid in N,N-dimethylformamide and cobalt nitrate hexahydrate in methanol. After mixing and reacting, wash, collect the solid by centrifugation, and dry to obtain NH2-ZIF-67 powder. (2) KH-560, sodium dodecyl sulfate, n-hexadecane and azobisisobutyronitrile are mixed and reacted to obtain EP-PSO emulsion; (3) Disperse NH2-ZIF-67 in N,N-dimethylformamide, add EP-PSO emulsion, and react; (4) After the reaction is completed, the polysiloxane-modified ZIF-67 is obtained by centrifugation, washing and vacuum drying.

3. The high-efficiency flame-retardant and low-toxicity gas-emission silicone rubber composite material according to claim 2, characterized in that, The molar ratio of epoxy groups in EP-PSO emulsion to the molar ratio of amino groups in NH2-ZIF-67 is 2:1 to 3:

1.

4. The high-efficiency flame-retardant and low-toxicity gas-emission silicone rubber composite material according to claim 1, characterized in that, The preparation method of the modified nano-molybdenum oxide includes the following steps: (1) The dried molybdenum oxide was added to anhydrous xylene, and then triethoxysilane was added. The mixture was heated and reacted. After the reaction was completed, the mixture was cooled, centrifuged, and the solid was collected, washed, and dried under vacuum to obtain Si-H modified molybdenum oxide. (2) Si-H modified molybdenum oxide was dispersed in anhydrous xylene, vinyl-terminated dimethyl polysiloxane was added, nitrogen gas was introduced, platinum catalyst was added, and the reaction was heated. After the reaction was completed, it was cooled to room temperature, washed, and dried to obtain modified molybdenum oxide.

5. The high-efficiency flame-retardant and low-toxicity gas-emission silicone rubber composite material according to claim 4, characterized in that, The mass ratio of Si-H modified molybdenum oxide to vinyl-terminated dimethyl polysiloxane is 1:(2-5).

6. The high-efficiency flame-retardant and low-toxicity gas-emission silicone rubber composite material according to claim 4, characterized in that, The amount of catalyst used is 50-100 ppm of the mass of vinyl-terminated dimethylpolysiloxane, based on platinum metal.

7. The high-efficiency flame-retardant and low-toxicity gas-emission silicone rubber composite material according to claim 4, characterized in that, The molecular weight (Mw) of vinyl-terminated dimethyl polysiloxane is 1800-2200.

8. The high-efficiency flame-retardant and low-toxicity gas-emission silicone rubber composite material according to claim 1, characterized in that, The mass ratio of methyl vinyl silicone rubber, polysiloxane-modified ZIF-67, and modified nano molybdenum oxide is 100:(14-16):(5-7).

9. The high-efficiency flame-retardant and low-toxicity gas-emission silicone rubber composite material according to claim 1, characterized in that, The additives include at least one of structure control agents and heat-resistant additives.

10. A method for preparing a high-efficiency flame-retardant, low-toxicity gas-release silicone rubber composite material according to any one of claims 1-9, characterized in that, Includes the following steps: (1) Pretreatment: The mesoporous SiO2 aerogel was dried to remove adsorbed water, and pretreated mesoporous SiO2 aerogel was obtained. (2) Initial mixing: methyl vinyl silicone rubber is rolled on a two-roll mill with hydroxyl silicone oil, PSi@ZIF-67, modified nano MoO3, MCA, pretreated mesoporous SiO2 aerogel and additives added in sequence, and mixed until evenly dispersed; (3) Final mixing: Continue to add vulcanizing agent and continue mixing to obtain compound rubber; (4) Vulcanization molding: The compound rubber is subjected to first-stage vulcanization and second-stage vulcanization in sequence; (5) Post-processing: After vulcanization, the sample is taken out and cooled to obtain a high-efficiency flame-retardant silicone rubber composite material with low toxic gas release.

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