Low volatile high heat resistant flame retardant silicone rubber and preparation method thereof

Abstract

The application discloses low-volatile high-heat-resistant flame-retardant silicone rubber and a preparation method thereof. The low-volatile high-heat-resistant flame-retardant silicone rubber is prepared from the following raw materials in mass parts: 100 parts of methylphenyl vinyl silicone rubber raw rubber, 20-70 parts of hydrophobic fumed white carbon black, 3-15 parts of a structure control agent, 1-10 parts of a flame-retardant heat-resistant agent, 0.2-0.8 parts of hydrogen-containing silicone oil and 1.5-2.5 parts of a two-component platinum gold catalyst, wherein the flame-retardant heat-resistant agent comprises fumed titanium dioxide, nano cerium oxide and polysilazane resin, and the structure control agent is hexamethyldisilazane and water. The flame-retardant heat-resistant agent and the methylphenyl vinyl silicone rubber raw rubber and other raw materials are synergistically matched, so that the flame retardancy and heat resistance of the silicone rubber are effectively improved, and the volatile content in the silicone rubber system is effectively reduced.

Description

Technical Field

[0001] This invention relates to the field of silicone rubber materials technology, and in particular to a low-volatile, high-heat-resistant, flame-retardant silicone rubber and its preparation method. Background Technology

[0002] Silicone rubber, with its unique Si-O-Si main chain structure, possesses excellent properties such as high and low temperature resistance, electrical insulation, weather resistance, and physiological inertness, making it widely used in high-end fields such as electronics, aerospace, medical devices, and new energy vehicles. However, with the rapid development of technologies in these fields, especially the emergence of applications such as aerospace vehicle cabins, precision electronic packaging, and vacuum environments, three almost stringent requirements have been placed on the comprehensive performance of silicone rubber: low volatility, ultra-high heat resistance, and high flame retardancy. Existing silicone rubber materials often struggle to simultaneously meet these three performance indicators, presenting a significant challenge in balancing performance.

[0003] First, regarding the requirement for low volatile organic compounds (VOCs). In confined spaces such as spacecraft and satellites, volatile organic compounds (VOCs) and condensable volatile matter (CVCMs) released from materials can disperse and condense on the surfaces of critical components such as low-temperature optical lenses and precision sensors, forming a "contamination film" that leads to equipment performance degradation or even permanent failure. The decomposition of small molecule byproducts from peroxide vulcanization systems, as well as the condensation reaction of incompletely reacted hydroxyl groups at polymer chain ends under vacuum and high temperatures, both produce small molecule siloxanes that volatilize. The current conventional solution is to perform long-term (usually exceeding 8 hours) high-temperature (above 200°C) secondary vulcanization, but this not only significantly increases energy consumption and production costs, and extends the production cycle, but is also difficult to implement for certain complex structures or already assembled components. Furthermore, residual structure control agents are prone to precipitate and liquefy under high temperatures, which is also a significant factor in the formation of contamination films.

[0004] Secondly, regarding the requirements for ultra-high heat resistance. Environments such as new energy vehicle motors, high-speed rail power modules, and the vicinity of aerospace engine compartments require silicone rubber to operate at temperatures above 250°C or even 300°C for extended periods. The upper limit of the long-term operating temperature for ordinary methyl vinyl silicone rubber (VMQ) is usually only 200°C. Although the thermal stability can be significantly improved by introducing phenyl groups (to produce PVMQ), its heat resistance is still limited by several factors: (1) the silanol groups on the surface of silica will catalyze the rearrangement and depolymerization of the polymer backbone at high temperatures; (2) residual catalysts, structural control agents, and other small molecules will accelerate the thermal aging of the material at high temperatures; (3) the oxidative degradation of polymer molecular chains under the action of high temperature and oxygen. Current methods to improve heat resistance, such as adding rare earth oxides (e.g., iron oxide, cerium oxide) as heat-resistant additives or using more stable raw rubber, have some effect, but often conflict with the requirement of low volatile content (heat-resistant additives may introduce impurities), and are still insufficient to meet the long-term use requirements in extreme environments.

[0005] Finally, regarding flame retardancy requirements. The electronics, electrical, and transportation sectors have mandatory requirements for the flame retardancy safety level of materials (such as UL94 V-0). Traditional silicone rubber itself has a certain degree of flame retardancy, but it is difficult to reach the highest V-0 level (especially in the case of thin walls). Flame retardants are usually required to be added, but this raises new problems: (1) Adding inorganic hydroxide flame retardants (such as aluminum hydroxide ATH) requires extremely high addition amounts (often exceeding 100 parts) to be effective, which seriously degrades the mechanical properties of the material (such as hardening and brittleness) and processing fluidity. Moreover, the crystal water contained in these flame retardants will volatilize at high temperatures, not only generating VOCs, but also forming defects inside the material, which seriously reduces its heat resistance; (2) Adding halogenated flame retardants is highly efficient, but because they produce toxic and corrosive gases when burning, they have been banned in most high-end fields; (3) Adding phosphorus-based flame retardants can easily lead to the "poisoning" and failure of platinum catalysts, resulting in narrow applicability.

[0006] A prominent contradiction exists in existing technologies: the pursuit of high flame retardancy often comes at the cost of sacrificing heat resistance and low volatility; conversely, the pursuit of high heat resistance and low volatility often limits the selection of highly efficient flame-retardant systems. Currently, the market lacks a solution that can fundamentally and synergistically resolve this contradiction. Most products are merely compromises and cannot meet the extreme performance requirements of cutting-edge fields such as aerospace and high-end electronics. Therefore, developing a silicone rubber material that combines extremely low volatility, ultra-high heat resistance, inherently high flame retardancy, and excellent mechanical properties has become a critical technical challenge urgently needing to be solved in this field, and also has enormous market application value. Summary of the Invention

[0007] In view of the above problems, the purpose of this invention is to provide a low-volatile, high-heat-resistant, flame-retardant silicone rubber and its preparation method. The silicone rubber has good high-heat resistance and flame-retardant properties, while having a low volatile content.

[0008] To achieve the above objectives, the present invention provides a low-volatile, high-heat-resistant, flame-retardant silicone rubber. The raw materials, by weight, include: 100 parts of methylphenyl vinyl silicone rubber raw rubber, 20-70 parts of hydrophobic fumed silica, 3-15 parts of a structuring agent, 1-10 parts of a flame-retardant and heat-resistant agent, 0.2-0.8 parts of hydrogen-containing silicone oil, and 1.5-2.5 parts of a two-component platinum catalyst. The flame-retardant and heat-resistant agent includes fumed titanium dioxide, nano-cerium oxide, and polysilazane resin. The structuring agent is hexamethyldisilazane and water.

[0009] Compared with the prior art, the low-volatile, high-heat-resistant, flame-retardant silicone rubber of the present invention has at least the following beneficial effects: (1) This invention uses fumed titanium dioxide, nano-cerium oxide, and polysilazane resin as flame retardant and heat-resistant agents. Under high-temperature conditions, the polysilazane resin begins to crosslink, solidify, and decompose, generating an amorphous ceramic layer in situ, which provides a basic framework for the entire protective layer. However, this basic framework is not dense enough. At the same time, silicone rubber rapidly chars under the synergistic catalytic action of fumed titanium dioxide and nano-cerium oxide. This char seamlessly embeds itself into the ceramic framework formed by the polysilazane, filling the pores and making the protective layer more dense. Furthermore, the fumed titanium dioxide dispersed in the ceramic framework can significantly improve the mechanical strength and thermal shock resistance of the ceramic layer, preventing the ceramicized layer from cracking and falling off during flame impact resistance. Meanwhile, the nitrogen element provided by the polysilazane resin achieves a synergistic flame retardant effect between the solidified phase and the fumed phase. Therefore, this invention, through the synergistic effect of fumed titanium dioxide, nano-cerium oxide, and polysilazane resin, can form a dense Si-OC protective layer in a high-temperature environment, thereby achieving flame retardancy and high-temperature oxidation protection. This allows the silicone rubber material to achieve a UL94 V-0 rating with a thickness of only 3mm without the addition of any traditional flame retardants. Furthermore, this invention uses methylphenyl vinyl silicone rubber as the base rubber. The introduction of phenyl groups significantly improves the heat resistance of the silicone rubber. In synergy with flame retardant and heat-resistant agents, the silicone rubber material of this invention achieves a long-term heat resistance temperature >250℃, a thermal decomposition initiation temperature ≥480℃, and a tensile strength retention rate >80% after aging at 250℃ for 1440 hours.

[0010] (2) The silicone rubber material system of the present invention does not contain hydroxyl silicone oil, thereby significantly reducing the generation and volatilization of small molecule siloxanes in the system. At the same time, the silica of the present invention is a hydrophobic fumed silica. By using hexamethyldisilazane and polysilazane resin to effectively treat the hydroxyl groups on the surface of the hydrophobic fumed silica, using a two-component platinum vulcanization system without by-products, and using methylphenyl vinyl silicone rubber raw rubber and hydrogen-containing silicone oil to form an ultra-high crosslinking density network, the source of small organic molecules in the silicone rubber system of the present invention is effectively eliminated through the mutual cooperation of the above three factors, thereby reducing the volatile matter of the system.

[0011] Furthermore, the mass ratio of fumed titanium dioxide, nano-cerium oxide, and polysilazane resin in this invention is 1~3:1~3:1~3.

[0012] Furthermore, the specific surface area of ​​the fumed titanium dioxide of the present invention is 35~65 m². 2 / g.

[0013] Furthermore, the particle size of the nano-cerium oxide of the present invention is 1~10μm.

[0014] Furthermore, the molecular weight of the polysilazane resin of the present invention is 5000~8000 g / mol.

[0015] Furthermore, the two-component platinum catalyst of the present invention comprises component A and component B in a weight ratio of 0.5~1:1~1.5, component A is a platinum catalyst with a platinum content of 300ppm, and component B is composed of a crosslinking agent and an inhibitor in a weight ratio of 25~40:0.5~1.5.

[0016] Furthermore, the molecular weight of the methylphenyl vinyl silicone rubber raw material of the present invention is 580,000 to 650,000, the molar fraction of (C6H5)CH3SiO repeating units is 10 to 20%, and the molar fraction of vinyl groups is 0.2 to 0.5%.

[0017] Furthermore, the mass ratio of hexamethyldisilazane to water in this invention is 2.5 to 4.5:1.

[0018] Furthermore, the specific surface area of ​​the hydrophobic fumed silica of the present invention is 200 m². 2 / g.

[0019] Furthermore, the active hydrogen content in the hydrogen-containing silicone oil of the present invention is 0.45% to 1.5% by mass.

[0020] Another aspect of the present invention provides a method for preparing the aforementioned low-volatile, high-heat-resistant, flame-retardant silicone rubber, comprising the steps of: (1) Methylphenyl vinyl silicone rubber, hydrogen-containing silicone oil, polysilazane resin, structure control agent and some hydrophobic fumed silica are added to the internal mixer and mixed to obtain the first mixture; (2) Add the remaining hydrophobic fumed silica to the first mixture, mix them evenly in a protective atmosphere, and then cool them at room temperature to obtain the second mixture; (3) The second mixture is mixed in a protective atmosphere and heated to a certain temperature, and then vacuum treated to obtain the third mixture; (4) Cool the third mixture to room temperature, add nano-cerium oxide and fumed titanium dioxide for mixing, cool to room temperature and then re-mix and filter to obtain the fourth mixture; (5) Add a two-component platinum catalyst to the fourth mixture and mix evenly at room temperature to obtain a low-volatile, high-heat-resistant, flame-retardant silicone rubber.

[0021] Furthermore, in step (1), the amount of hydrophobic fumed silica added in this invention accounts for 30% of the total mass of hydrophobic fumed silica.

[0022] Furthermore, in step (2), the remaining hydrophobic fumed silica of the present invention is added in four portions, and the amount of the remaining hydrophobic fumed silica added accounts for 20%, 20%, 15%, and 15% of the total mass of the hydrophobic fumed silica, respectively.

[0023] Furthermore, in step (3), the mixing temperature is raised to 110~130℃.

[0024] Furthermore, in step (3), the vacuum degree of the vacuum treatment of the present invention is 0.06~0.08MPa, and the vacuum treatment time is 4~8h. Detailed Implementation

[0025] The low-volatile, high-heat-resistant, flame-retardant silicone rubber of the present invention is prepared by means of the following raw materials in parts by weight: 100 parts of methylphenyl vinyl silicone rubber raw rubber, 20-70 parts of hydrophobic fumed silica, 3-15 parts of structuring control agent, 1-10 parts of flame-retardant and heat-resistant agent, 0.2-0.8 parts of hydrogen-containing silicone oil, and 1.5-2.5 parts of two-component platinum catalyst.

[0026] The methylphenyl vinyl silicone rubber raw material has a molecular weight of 580,000 to 650,000, a molar fraction of (C6H5)CH3SiO repeating units of 10% to 20%, and a molar fraction of vinyl groups of 0.2% to 0.5%. As an example, the molecular weight of the methylphenyl vinyl silicone rubber raw material can be, but is not limited to, 580,000, 590,000, 600,000, 610,000, 620,000, 630,000, 640,000, or 650,000; the molar fraction of (C6H5)CH3SiO repeating units can be, but is not limited to, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, or 20%; and the molar fraction of vinyl groups can be, but is not limited to, 0.2%, 0.3%, 0.4%, or 0.5%. It should be noted that the methylphenyl vinyl silicone rubber raw material of this invention can be prepared according to conventional methods in the art, or it can be obtained through conventional commercial purchases. As an example, the methylphenyl vinyl silicone rubber raw material of this invention can be purchased from Anhui Mingyi Silicon Industry Co., Ltd. Specifically, the structural formula of methylphenyl vinyl silicone rubber raw rubber is shown in Formula 1 (in Formula 1, m, n, and p represent the degree of polymerization).

[0027]

[0028] Formula 1 The mass fraction of the hydrophobic fumed silica can be, but is not limited to, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, or 70 parts. Preferably, the mass fraction of the hydrophobic fumed silica of this invention is 30-50 parts. The specific surface area of ​​the hydrophobic fumed silica of this invention is 200 m². 2 / g. Hydrophobic fumed silica exhibits better dispersibility, extremely low hygroscopicity, and superior water resistance compared to conventional fumed silica.

[0029] The mass fraction of the structure control agent can be, but is not limited to, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15 parts. Preferably, the mass fraction of the structure control agent of the present invention is 5 to 10 parts. The structure control agent is hexamethyldisilazane and water, and the mass ratio of hexamethyldisilazane to water is 2.5 to 4.5:1. As an example, the mass ratio of hexamethyldisilazane to water can be, but is not limited to, 2.5:1, 2.8:1, 3:1, 3.2:1, 3.4:1, 3.5:1, 3.6:1, 3.8:1, 4:1, 4.1:1, 4.2:1, 4.3:1, 4.4:1, or 4.5:1.

[0030] The mass fraction of the flame retardant and heat resistant agent can be, but is not limited to, 1 part, 2 parts, 3 parts, 4 parts, 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, or 10 parts. Preferably, the mass fraction of the flame retardant and heat resistant agent is 1 to 5 parts. The flame retardant and heat resistant agent includes fumed titanium dioxide, nano-cerium oxide, and polysilazane resin, with a mass ratio of fumed titanium dioxide, nano-cerium oxide, and polysilazane resin of 1 to 3:1 to 3:1 to 3. Preferably, the mass ratio of fumed titanium dioxide, nano-cerium oxide, and polysilazane resin is 1:1:1. The specific surface area of ​​the fumed titanium dioxide of this invention is 35 to 65 m². 2 / g, as an example. The specific surface area of ​​fumed titanium dioxide can be, but is not limited to, 35m². 2 / g、40m 2 / g、45m 2 / g, 50m 2 / g、55m 2 / g、60m 2 / g、65m 2 / g, it should be noted that this invention does not limit the source of fumed titanium dioxide; fumed titanium dioxide within this specific surface area range can guarantee the performance of the product. The particle size of the nano-cerium oxide of this invention is 1~10μm. As an example, the particle size of nano-cerium oxide can be, but is not limited to, 1μm, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, and 10μm. It should be noted that this invention does not limit the source of nano-cerium oxide; nano-cerium oxide within this particle size range can guarantee the performance of the product. The molecular weight of the polysilazane resin is 5000~8000g / mol. As an example, the molecular weight of the polysilazane resin can be, but is not limited to, 5000g / mol, 5500g / mol, 6000g / mol, 6500g / mol, 7000g / mol, 7500g / mol, and 8000g / mol. It should be noted that this invention does not restrict the source of the polysilazane resin; polysilazane resins within this molecular weight range can guarantee the performance of the product. Specifically, the structural formula of the polysilazane resin of this invention is shown in Formula 2 (in Formula 2, n represents the degree of polymerization).

[0031]

[0032] Formula 2 The mass fraction of hydrogen-containing silicone oil can be, but is not limited to, 0.2 parts, 0.3 parts, 0.4 parts, 0.5 parts, 0.6 parts, 0.7 parts, or 0.8 parts. The mass content of active hydrogen in the hydrogen-containing silicone oil is 0.45% to 1.5%. For example, the mass content of active hydrogen in hydrogen-containing silicone oils is 0.45%, 0.5%, 0.55%, 0.6%, 0.8%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, or 1.5%. The viscosity of the hydrogen-containing silicone oil is 15 to 25 mm.2 / s, as an example, the viscosity of hydrogen-containing silicone oil can be, but is not limited to, 15 mm. 2 / s, 16mm 2 / s, 17mm 2 / s, 18mm 2 / s, 19mm 2 / s, 20mm 2 / s, 21mm 2 / s, 22mm 2 / s, 23mm 2 / s, 24mm 2 / s, 25mm 2 / s.

[0033] The weight proportions of the two-component platinum catalyst can be, but are not limited to, 1.5, 1.6, 1.7, 1.8, 1.9, 2, 2.1, 2.2, 2.3, 2.4, or 2.5 parts. The two-component platinum catalyst comprises component A and component B in a weight ratio of 0.5–1:1–1.5. Component A is a platinum catalyst with a platinum content of 300 ppm, and component B consists of a crosslinking agent and an inhibitor, with a weight ratio of crosslinking agent to inhibitor of 25–40:0.5–1.5. Specifically, the weight ratio of component A to component B can be, but is not limited to, 0.5:1, 0.5:1.2, 0.5:1.5, 0.6:1, 0.6:1.2, 0.6:1.5, 0.8:1, 0.8:1.2, 0.8:1.5, 1:1, 1:1.2, or 1:1.5; the weight ratio of crosslinking agent to inhibitor can be, but is not limited to, 25:0.5, 25:1, 25:1.5, 30:0.5, 30:1, 30:1.5, 35:0.5, 35:1, 35:1.5, 40:0.5, 40:1, or 40:1.5.

[0034] The preparation method of the low-volatile, high-heat-resistant, flame-retardant silicone rubber of the present invention includes the following steps: (1) Methylphenyl vinyl silicone rubber, hydrogen-containing silicone oil, polysilazane resin, structure control agent and hydrophobic fumed silica are added to a mixer and mixed to obtain the first mixture; (2) Add the remaining hydrophobic fumed silica to the first mixture, mix them evenly in a protective atmosphere, and then cool them at room temperature to obtain the second mixture; (3) The second mixture is mixed in a protective atmosphere and heated to a certain temperature, and then vacuum treated to obtain the third mixture; (4) Cool the third mixture to room temperature, add nano-cerium oxide and fumed titanium dioxide for mixing, cool to room temperature and then re-mix and filter to obtain the fourth mixture; (5) Add a two-component platinum catalyst to the fourth mixture and mix evenly at room temperature to obtain a low-volatile, high-heat-resistant, flame-retardant silicone rubber.

[0035] In step (1), the amount of hydrophobic fumed silica added accounts for 30% of the total mass of hydrophobic fumed silica.

[0036] In step (2), the remaining hydrophobic fumed silica is added in four portions, and the amount of the remaining hydrophobic fumed silica added accounts for 20%, 20%, 15%, and 15% of the total mass of the hydrophobic fumed silica, respectively.

[0037] In step (3), the mixing temperature is raised to 110~130℃.

[0038] In step (3), the vacuum degree of the vacuum treatment is 0.06~0.08MPa, and the vacuum treatment time is 4~8h.

[0039] To better illustrate the purpose, technical solution, and beneficial effects of this invention, the invention will be further described below with reference to specific embodiments. It should be noted that the methods described below are further explanations of this invention and should not be construed as limiting it.

[0040] In the embodiments and comparative examples of this invention, the raw methylphenyl vinyl silicone rubber was manufactured by Anhui Mingyi Silicon Industry Co., Ltd., with a molecular weight of 600,000, a molar fraction of (C6H5)CH3SiO repeating units of 15%, and a molar fraction of vinyl groups of 0.23%; the fumed titanium dioxide was manufactured by Guangzhou Xiyi Chemical Co., Ltd., with the product type PF2 and a specific surface area of ​​50 m². 2 / g; the manufacturer of nano-cerium oxide is Baotou Lanthanide Organosilicon Materials Technology Co., Ltd., with a particle size of 5μm; the manufacturer of polysilazane resin is Jiangxi Yanxun Silicon Materials Co., Ltd., with a molecular weight of 6000g / mol; the manufacturer of hydrogen-containing silicone oil is Zhejiang Xin'an Maitu Organosilicon Co., Ltd., with an active hydrogen content of 1.5% and a viscosity of 20mm. 2 / s; The molar fraction of vinyl in the raw methyl vinyl silicone rubber is 0.23%, and the molecular weight is 600,000 g / mol; The manufacturer of hydrophobic fumed silica is Evonik Industries, Inc., with a specific surface area of ​​200 m² / s. 2 / g; The manufacturer of ordinary fumed silica is Hubei Huifu Nanomaterials Co., Ltd., with a specific surface area of ​​200m². 2 / g; The manufacturer of the two-component platinum catalyst is Dongguan Yaneng Organosilicon Materials Co., Ltd. The two-component platinum catalyst comprises component A and component B in a weight ratio of 0.6:1.5. Component A is a platinum catalyst with a platinum content of 300 ppm, and component B consists of a crosslinking agent and an inhibitor in a weight ratio of 33:1. The crosslinking agent is a hydrogen-containing silicone oil with an active hydrogen content of 0.75% and a viscosity of 20 mm. 2 The inhibitor is 1-ethynylcyclohexanol. All other raw materials not specified herein are commercially available.

[0041] Example 1 This embodiment provides a low-volatile, high-heat-resistant, flame-retardant silicone rubber. The raw materials for preparation, by mass, include: 100 parts of methylphenyl vinyl silicone rubber raw rubber, 40 parts of hydrophobic fumed silica, 6 parts of hexamethyldisilazane, 2 parts of distilled water, 1 part of fumed titanium dioxide, 1 part of nano-cerium oxide, 1 part of polysilazane resin, 0.5 parts of hydrogen-containing silicone oil, and 2.1 parts of a two-component platinum catalyst.

[0042] This embodiment also provides a method for preparing the aforementioned low-volatile, high-heat-resistant, flame-retardant silicone rubber, including the following steps: (1) Add 100 parts of methyl phenyl vinyl silicone rubber, 0.5 parts of hydrogen-containing silicone oil, 1 part of polysilazane resin, 12 parts of hydrophobic fumed silica, 6 parts of hexamethyldisilazane and 2 parts of distilled water to a mixer and mix with the lid open for 20-30 minutes to obtain the first mixture. (2) Add 8 parts, 8 parts, 6 parts and 6 parts of hydrophobic fumed silica to the first mixture in batches, purge with nitrogen for protection, mix with the lid open for 20-30 minutes and then cool at room temperature for 12 hours to obtain the second mixture; (3) The second mixture is mixed in a nitrogen atmosphere and heated to 120°C and then vacuum treated with a vacuum degree of 0.06~0.08MPa for 6 hours to obtain the third mixture; (4) Cool the third mixture to room temperature, add 1 part of nano cerium oxide and 1 part of fumed titanium dioxide and knead for 20-40 minutes. After cooling to room temperature, re-knead and filter in a filter using a 300-mesh stainless steel mesh to obtain the fourth mixture. (5) Add 2.1 parts of a two-component platinum catalyst to the fourth mixture and mix evenly at room temperature to obtain a low-volatile, high-heat-resistant, flame-retardant silicone rubber.

[0043] Example 2 This embodiment provides a low-volatile, high-heat-resistant, flame-retardant silicone rubber. The raw materials for preparation, by mass, include: 100 parts of methylphenyl vinyl silicone rubber raw rubber, 30 parts of hydrophobic fumed silica, 4 parts of hexamethyldisilazane, 1.33 parts of distilled water, 1 part of fumed titanium dioxide, 1 part of nano-cerium oxide, 1 part of polysilazane resin, 0.5 parts of hydrogen-containing silicone oil, and 2.1 parts of a two-component platinum catalyst.

[0044] This embodiment also provides a method for preparing the aforementioned low-volatile, high-heat-resistant, flame-retardant silicone rubber, including the following steps: (1) Add 100 parts of methyl phenyl vinyl silicone rubber, 0.5 parts of hydrogen-containing silicone oil, 1 part of polysilazane resin, 9 parts of hydrophobic fumed silica, 4 parts of hexamethyldisilazane and 1.33 parts of distilled water to a mixer and mix with the lid open for 20-30 minutes to obtain the first mixture; (2) Add 6 parts, 6 parts, 4.5 parts and 4.5 parts of hydrophobic fumed silica to the first mixture in batches, purge with nitrogen for protection, mix with the lid open for 20-30 minutes and then cool at room temperature for 12 hours to obtain the second mixture; (3) The second mixture is mixed in a nitrogen atmosphere and heated to 120°C and then vacuum treated with a vacuum degree of 0.06~0.08MPa for 6 hours to obtain the third mixture; (4) Cool the third mixture to room temperature, add 1 part of nano cerium oxide and 1 part of fumed titanium dioxide and knead for 20-40 minutes. After cooling to room temperature, re-knead and filter in a filter using a 300-mesh stainless steel mesh to obtain the fourth mixture. (5) Add 2.1 parts of a two-component platinum catalyst to the fourth mixture and mix evenly at room temperature to obtain a low-volatile, high-heat-resistant, flame-retardant silicone rubber.

[0045] Example 3 This embodiment provides a low-volatile, high-heat-resistant, flame-retardant silicone rubber. The raw materials for preparation, by mass, include: 100 parts of methylphenyl vinyl silicone rubber raw rubber, 50 parts of hydrophobic fumed silica, 7.5 parts of hexamethyldisilazane, 2.5 parts of distilled water, 1 part of fumed titanium dioxide, 1 part of nano-cerium oxide, 1 part of polysilazane resin, 0.5 parts of hydrogen-containing silicone oil, and 2.1 parts of a two-component platinum catalyst.

[0046] This embodiment also provides a method for preparing the aforementioned low-volatile, high-heat-resistant, flame-retardant silicone rubber, including the following steps: (1) Add 100 parts of methyl phenyl vinyl silicone rubber, 0.5 parts of hydrogen-containing silicone oil, 1 part of polysilazane resin, 15 parts of hydrophobic fumed silica, 7.5 parts of hexamethyldisilazane and 2.5 parts of distilled water to a mixer and mix with the lid off for 20-30 minutes to obtain the first mixture; (2) Add 10 parts, 10 parts, 7.5 parts and 7.5 parts of hydrophobic fumed silica to the first mixture in batches, purge with nitrogen for protection, mix with the lid open for 20-30 minutes and then cool at room temperature for 12 hours to obtain the second mixture; (3) The second mixture is mixed in a nitrogen atmosphere and heated to 120°C and then vacuum treated with a vacuum degree of 0.06~0.08MPa for 6 hours to obtain the third mixture; (4) Cool the third mixture to room temperature, add 1 part of nano cerium oxide and 1 part of fumed titanium dioxide and knead for 20-40 minutes. After cooling to room temperature, re-knead and filter in a filter using a 300-mesh stainless steel mesh to obtain the fourth mixture. (5) Add 2.1 parts of a two-component platinum catalyst to the fourth mixture and mix evenly at room temperature to obtain a low-volatile, high-heat-resistant, flame-retardant silicone rubber.

[0047] Example 4 This embodiment provides a low-volatile, high-heat-resistant, flame-retardant silicone rubber. The raw materials for preparation, by mass, include: 100 parts of methylphenyl vinyl silicone rubber raw rubber, 40 parts of hydrophobic fumed silica, 6 parts of hexamethyldisilazane, 2 parts of distilled water, 1 part of fumed titanium dioxide, 1 part of nano-cerium oxide, 1 part of polysilazane resin, 0.2 parts of hydrogen-containing silicone oil, and 2.1 parts of a two-component platinum catalyst.

[0048] This embodiment also provides a method for preparing the aforementioned low-volatile, high-heat-resistant, flame-retardant silicone rubber, including the following steps: (1) Add 100 parts of methyl phenyl vinyl silicone rubber, 0.2 parts of hydrogen-containing silicone oil, 1 part of polysilazane resin, 12 parts of hydrophobic fumed silica, 6 parts of hexamethyldisilazane and 2 parts of distilled water to a mixer and mix with the lid open for 20-30 minutes to obtain the first mixture; (2) Add 8 parts, 8 parts, 6 parts and 6 parts of hydrophobic fumed silica to the first mixture in batches, purge with nitrogen for protection, mix with the lid open for 20-30 minutes and then cool at room temperature for 12 hours to obtain the second mixture; (3) The second mixture is mixed in a nitrogen atmosphere and heated to 120°C and then vacuum treated with a vacuum degree of 0.06~0.08MPa for 6 hours to obtain the third mixture; (4) Cool the third mixture to room temperature, add 1 part of nano cerium oxide and 1 part of fumed titanium dioxide and knead for 20-40 minutes. After cooling to room temperature, re-knead and filter in a filter using a 300-mesh stainless steel mesh to obtain the fourth mixture. (5) Add 2.1 parts of a two-component platinum catalyst to the fourth mixture and mix evenly at room temperature to obtain a low-volatile, high-heat-resistant, flame-retardant silicone rubber.

[0049] Example 5 This embodiment provides a low-volatile, high-heat-resistant, flame-retardant silicone rubber. The raw materials for preparation, by mass, include: 100 parts of methylphenyl vinyl silicone rubber raw rubber, 40 parts of hydrophobic fumed silica, 6 parts of hexamethyldisilazane, 2 parts of distilled water, 1 part of fumed titanium dioxide, 1 part of nano-cerium oxide, 1 part of polysilazane resin, 0.8 parts of hydrogen-containing silicone oil, and 2.1 parts of a two-component platinum catalyst.

[0050] This embodiment also provides a method for preparing the aforementioned low-volatile, high-heat-resistant, flame-retardant silicone rubber, including the following steps: (1) Add 100 parts of methyl phenyl vinyl silicone rubber, 0.8 parts of hydrogen-containing silicone oil, 1 part of polysilazane resin, 12 parts of hydrophobic fumed silica, 6 parts of hexamethyldisilazane and 2 parts of distilled water to a mixer and mix with the lid open for 20-30 minutes to obtain the first mixture; (2) Add 8 parts, 8 parts, 6 parts and 6 parts of hydrophobic fumed silica to the first mixture in batches, purge with nitrogen for protection, mix with the lid open for 20-30 minutes and then cool at room temperature for 12 hours to obtain the second mixture; (3) The second mixture is mixed in a nitrogen atmosphere and heated to 120°C and then vacuum treated with a vacuum degree of 0.06~0.08MPa for 6 hours to obtain the third mixture; (4) Cool the third mixture to room temperature, add 1 part of nano cerium oxide and 1 part of fumed titanium dioxide and knead for 20-40 minutes. After cooling to room temperature, re-knead and filter in a filter using a 300-mesh stainless steel mesh to obtain the fourth mixture. (5) Add 2.1 parts of a two-component platinum catalyst to the fourth mixture and mix evenly at room temperature to obtain a low-volatile, high-heat-resistant, flame-retardant silicone rubber.

[0051] Comparative Example 1 This comparative example provides a low-volatile, high-heat-resistant, flame-retardant silicone rubber. By mass, the raw materials include: 50 parts of methyl phenyl vinyl silicone rubber raw rubber, 40 parts of hydrophobic fumed silica, 6 parts of hexamethyldisilazane, 2 parts of distilled water, 1 part of fumed titanium dioxide, 1 part of nano-cerium oxide, 1 part of polysilazane resin, 0.5 parts of hydrogen-containing silicone oil, and 2.1 parts of a two-component platinum catalyst.

[0052] This comparative example also provides a method for preparing the aforementioned low-volatile, high-heat-resistant, flame-retardant silicone rubber, including the following steps: (1) Add 50 parts of methyl phenyl vinyl silicone rubber raw rubber, 50 parts of methyl vinyl silicone rubber raw rubber, 0.5 parts of hydrogen-containing silicone oil, 1 part of polysilazane resin, 12 parts of hydrophobic fumed silica, 6 parts of hexamethyldisilazane and 2 parts of distilled water to a mixer and mix for 20-30 minutes with the lid off to obtain the first mixture. (2) Add 8 parts, 8 parts, 6 parts and 6 parts of hydrophobic fumed silica to the first mixture in batches, purge with nitrogen for protection, mix with the lid open for 20-30 minutes and then cool at room temperature for 12 hours to obtain the second mixture; (3) The second mixture is mixed in a nitrogen atmosphere and heated to 120°C and then vacuum treated with a vacuum degree of 0.06~0.08MPa for 6 hours to obtain the third mixture; (4) Cool the third mixture to room temperature, add 1 part of nano cerium oxide and 1 part of fumed titanium dioxide and knead for 20-40 minutes. After cooling to room temperature, re-knead and filter in a filter using a 300-mesh stainless steel mesh to obtain the fourth mixture. (5) Add 2.1 parts of a two-component platinum catalyst to the fourth mixture and mix evenly at room temperature to obtain a low-volatile, high-heat-resistant, flame-retardant silicone rubber.

[0053] Comparative Example 2 This comparative example provides a low-volatile, high-heat-resistant, flame-retardant silicone rubber. By mass, the raw materials include: 100 parts of methylphenyl vinyl silicone rubber raw rubber, 40 parts of ordinary fumed silica, 6 parts of hexamethyldisilazane, 2 parts of distilled water, 1 part of fumed titanium dioxide, 1 part of nano-cerium oxide, 1 part of polysilazane resin, 0.5 parts of hydrogen-containing silicone oil, and 2.1 parts of a two-component platinum catalyst.

[0054] This comparative example also provides a method for preparing the aforementioned low-volatile, high-heat-resistant, flame-retardant silicone rubber, including the following steps: (1) Add 100 parts of methyl phenyl vinyl silicone rubber raw rubber, 0.5 parts of hydrogen-containing silicone oil, 1 part of polysilazane resin, 12 parts of ordinary fumed silica, 6 parts of hexamethyldisilazane and 2 parts of distilled water to a mixer and mix with the lid open for 20-30 minutes to obtain the first mixture. (2) Add 8 parts, 8 parts, 6 parts and 6 parts of ordinary fumed silica to the first mixture in batches, pass nitrogen gas for protection, mix with the lid open for 20-30 minutes and then cool at room temperature for 12 hours to obtain the second mixture; (3) The second mixture is mixed in a nitrogen atmosphere and heated to 120°C and then vacuum treated with a vacuum degree of 0.06~0.08MPa for 6 hours to obtain the third mixture; (4) Cool the third mixture to room temperature, add 1 part of nano cerium oxide and 1 part of fumed titanium dioxide and knead for 20-40 minutes. After cooling to room temperature, re-knead and filter in a filter using a 300-mesh stainless steel mesh to obtain the fourth mixture. (5) Add 2.1 parts of a two-component platinum catalyst to the fourth mixture and mix evenly at room temperature to obtain a low-volatile, high-heat-resistant, flame-retardant silicone rubber.

[0055] Comparative Example 3 This comparative example provides a low-volatile, high-heat-resistant, flame-retardant silicone rubber. By mass, the raw materials include: 100 parts of methylphenyl vinyl silicone rubber raw rubber, 40 parts of ordinary fumed silica, 6 parts of hydroxyl silicone oil, 1 part of fumed titanium dioxide, 1 part of nano-cerium oxide, 1 part of polysilazane resin, 0.5 parts of hydrogen-containing silicone oil, and 2.1 parts of a two-component platinum catalyst.

[0056] This comparative example also provides a method for preparing the aforementioned low-volatile, high-heat-resistant, flame-retardant silicone rubber, including the following steps: (1) Add 100 parts of methyl phenyl vinyl silicone rubber raw rubber, 0.5 parts of hydrogen-containing silicone oil, 1 part of polysilazane resin, 12 parts of ordinary fumed silica and 6 parts of hydroxyl silicone oil to a mixer and mix with the lid open for 20-30 minutes to obtain the first mixture. (2) Add 8 parts, 8 parts, 6 parts and 6 parts of ordinary fumed silica to the first mixture in batches, pass nitrogen gas for protection, mix with the lid open for 20-30 minutes and then cool at room temperature for 12 hours to obtain the second mixture; (3) The second mixture is mixed in a nitrogen atmosphere and heated to 120°C and then vacuum treated with a vacuum degree of 0.06~0.08MPa for 6 hours to obtain the third mixture; (4) Cool the third mixture to room temperature, add 1 part of nano cerium oxide and 1 part of fumed titanium dioxide and knead for 20-40 minutes. After cooling to room temperature, re-knead and filter in a filter using a 300-mesh stainless steel mesh to obtain the fourth mixture. (5) Add 2.1 parts of a two-component platinum catalyst to the fourth mixture and mix evenly at room temperature to obtain a low-volatile, high-heat-resistant, flame-retardant silicone rubber.

[0057] Comparative Example 4 This comparative example provides a low-volatile, high-heat-resistant, flame-retardant silicone rubber. By mass, the raw materials include: 100 parts of methyl vinyl silicone rubber raw rubber, 40 parts of ordinary fumed silica, 6 parts of hydroxyl silicone oil, 1 part of fumed titanium dioxide, 1 part of nano-cerium oxide, 1 part of polysilazane resin, 0.5 parts of hydrogen-containing silicone oil, and 2.1 parts of a two-component platinum catalyst.

[0058] This comparative example also provides a method for preparing the aforementioned low-volatile, high-heat-resistant, flame-retardant silicone rubber, including the following steps: (1) Add 100 parts of methyl vinyl silicone rubber raw rubber, 0.5 parts of hydrogen-containing silicone oil, 1 part of polysilazane resin, 12 parts of ordinary fumed silica and 6 parts of hydroxyl silicone oil to a mixer and mix with the lid open for 20-30 minutes to obtain the first mixture. (2) Add 8 parts, 8 parts, 6 parts and 6 parts of ordinary fumed silica to the first mixture in batches, pass nitrogen gas for protection, mix with the lid open for 20-30 minutes and then cool at room temperature for 12 hours to obtain the second mixture; (3) The second mixture is mixed in a nitrogen atmosphere and heated to 120°C and then vacuum treated with a vacuum degree of 0.06~0.08MPa for 6 hours to obtain the third mixture; (4) Cool the third mixture to room temperature, add 1 part of nano cerium oxide and 1 part of fumed titanium dioxide and knead for 20-40 minutes. After cooling to room temperature, re-knead and filter in a filter using a 300-mesh stainless steel mesh to obtain the fourth mixture. (5) Add 2.1 parts of a two-component platinum catalyst to the fourth mixture and mix evenly at room temperature to obtain a low-volatile, high-heat-resistant, flame-retardant silicone rubber.

[0059] Comparative Example 5 This comparative example provides a low-volatile, high-heat-resistant, flame-retardant silicone rubber. By mass, the raw materials include: 100 parts of methylphenyl vinyl silicone rubber raw rubber, 40 parts of hydrophobic fumed silica, 6 parts of hexamethyldisilazane, 2 parts of distilled water, 3 parts of fumed titanium dioxide, 0.5 parts of hydrogen-containing silicone oil, and 2.1 parts of a two-component platinum catalyst.

[0060] This comparative example also provides a method for preparing the aforementioned low-volatile, high-heat-resistant, flame-retardant silicone rubber, including the following steps: (1) Add 100 parts of methyl phenyl vinyl silicone rubber, 0.5 parts of hydrogen-containing silicone oil, 12 parts of hydrophobic fumed silica, 6 parts of hexamethyldisilazane and 2 parts of distilled water to a mixer and mix with the lid open for 20-30 minutes to obtain the first mixture; (2) Add 8 parts, 8 parts, 6 parts and 6 parts of hydrophobic fumed silica to the first mixture in batches, purge with nitrogen for protection, mix with the lid open for 20-30 minutes and then cool at room temperature for 12 hours to obtain the second mixture; (3) The second mixture is mixed in a nitrogen atmosphere and heated to 120°C and then vacuum treated with a vacuum degree of 0.06~0.08MPa for 6 hours to obtain the third mixture; (4) Cool the third mixture to room temperature, add 3 parts of fumed titanium dioxide and knead for 20-40 minutes. After cooling to room temperature, re-knead and filter in a filter press using a 300-mesh stainless steel mesh to obtain the fourth mixture. (5) Add 2.1 parts of a two-component platinum catalyst to the fourth mixture and mix evenly at room temperature to obtain a low-volatile, high-heat-resistant, flame-retardant silicone rubber.

[0061] Comparative Example 6 This comparative example provides a low-volatile, high-heat-resistant, flame-retardant silicone rubber. By mass, the raw materials include: 100 parts of methylphenyl vinyl silicone rubber raw rubber, 40 parts of hydrophobic fumed silica, 6 parts of hexamethyldisilazane, 2 parts of distilled water, 3 parts of nano-cerium oxide, 0.5 parts of hydrogen-containing silicone oil, and 2.1 parts of a two-component platinum catalyst.

[0062] This comparative example also provides a method for preparing the aforementioned low-volatile, high-heat-resistant, flame-retardant silicone rubber, including the following steps: (1) Add 100 parts of methyl phenyl vinyl silicone rubber, 0.5 parts of hydrogen-containing silicone oil, 12 parts of hydrophobic fumed silica, 6 parts of hexamethyldisilazane and 2 parts of distilled water to a mixer and mix with the lid open for 20-30 minutes to obtain the first mixture; (2) Add 8 parts, 8 parts, 6 parts and 6 parts of hydrophobic fumed silica to the first mixture in batches, purge with nitrogen for protection, mix with the lid open for 20-30 minutes and then cool at room temperature for 12 hours to obtain the second mixture; (3) The second mixture is mixed in a nitrogen atmosphere and heated to 120°C and then vacuum treated with a vacuum degree of 0.06~0.08MPa for 6 hours to obtain the third mixture; (4) Cool the third mixture to room temperature, add 3 parts of nano-cerium oxide and knead for 20-40 minutes. After cooling to room temperature, re-knead and filter in a filter press using a 300-mesh stainless steel mesh to obtain the fourth mixture. (5) Add 2.1 parts of a two-component platinum catalyst to the fourth mixture and mix evenly at room temperature to obtain a low-volatile, high-heat-resistant, flame-retardant silicone rubber.

[0063] Comparative Example 7 This comparative example provides a low-volatile, high-heat-resistant, flame-retardant silicone rubber. By mass, the raw materials include: 100 parts of methylphenyl vinyl silicone rubber raw rubber, 40 parts of hydrophobic fumed silica, 6 parts of hexamethyldisilazane, 2 parts of distilled water, 3 parts of polysilazane resin, 0.5 parts of hydrogen-containing silicone oil, and 2.1 parts of a two-component platinum catalyst.

[0064] This comparative example also provides a method for preparing the aforementioned low-volatile, high-heat-resistant, flame-retardant silicone rubber, including the following steps: (1) Add 100 parts of methyl phenyl vinyl silicone rubber, 0.5 parts of hydrogen-containing silicone oil, 3 parts of polysilazane resin, 12 parts of hydrophobic fumed silica, 6 parts of hexamethyldisilazane and 2 parts of distilled water to a mixer and mix with the lid open for 20-30 minutes to obtain the first mixture. (2) Add 8 parts, 8 parts, 6 parts and 6 parts of hydrophobic fumed silica to the first mixture in batches, purge with nitrogen for protection, mix with the lid open for 20-30 minutes and then cool at room temperature for 12 hours to obtain the second mixture; (3) The second mixture is mixed in a nitrogen atmosphere and heated to 120°C and then vacuum treated with a vacuum degree of 0.06~0.08MPa for 6 hours to obtain the third mixture; (4) Cool the third mixture to room temperature, remelt it using an open mill, and filter it using a 300-mesh stainless steel mesh in a filter press to obtain the fourth mixture; (5) Add 2.1 parts of a two-component platinum catalyst to the fourth mixture and mix evenly at room temperature to obtain a low-volatile, high-heat-resistant, flame-retardant silicone rubber.

[0065] Comparative Example 8 This comparative example provides a low-volatile, high-heat-resistant, flame-retardant silicone rubber. By mass, the raw materials include: 100 parts of methylphenyl vinyl silicone rubber raw rubber, 40 parts of hydrophobic fumed silica, 6 parts of hexamethyldisilazane, 2 parts of distilled water, 1.5 parts of fumed titanium dioxide, 1.5 parts of nano-cerium oxide, 0.5 parts of hydrogen-containing silicone oil, and 2.1 parts of a two-component platinum catalyst.

[0066] This comparative example also provides a method for preparing the aforementioned low-volatile, high-heat-resistant, flame-retardant silicone rubber, including the following steps: (1) Add 100 parts of methyl phenyl vinyl silicone rubber, 0.5 parts of hydrogen-containing silicone oil, 12 parts of hydrophobic fumed silica, 6 parts of hexamethyldisilazane and 2 parts of distilled water to a mixer and mix with the lid open for 20-30 minutes to obtain the first mixture; (2) Add 8 parts, 8 parts, 6 parts and 6 parts of hydrophobic fumed silica to the first mixture in batches, purge with nitrogen for protection, mix with the lid open for 20-30 minutes and then cool at room temperature for 12 hours to obtain the second mixture; (3) The second mixture is mixed in a nitrogen atmosphere and heated to 120°C and then vacuum treated with a vacuum degree of 0.06~0.08MPa for 6 hours to obtain the third mixture; (4) Cool the third mixture to room temperature, add 1.5 parts of nano cerium oxide and 1.5 parts of fumed titanium dioxide and knead for 20-40 minutes. After cooling to room temperature, re-knead and filter in a filter using a 300-mesh stainless steel mesh to obtain the fourth mixture. (5) Add 2.1 parts of two-component platinum catalyst to the fourth mixture and mix evenly at room temperature to obtain low volatile high heat-resistant flame-retardant silicone rubber.

[0067] Comparative Example 9 This comparative example provides a low-volatile, high-heat-resistant, flame-retardant silicone rubber. By mass, the raw materials include: 100 parts of methylphenyl vinyl silicone rubber raw rubber, 40 parts of hydrophobic fumed silica, 6 parts of hexamethyldisilazane, 2 parts of distilled water, 1 part of fumed titanium dioxide, 1 part of nano-iron oxide, 1 part of polysilazane resin, 0.5 parts of hydrogen-containing silicone oil, and 2.1 parts of a two-component platinum catalyst.

[0068] This comparative example also provides a method for preparing the aforementioned low-volatile, high-heat-resistant, flame-retardant silicone rubber, including the following steps: (1) Add 100 parts of methyl phenyl vinyl silicone rubber, 0.5 parts of hydrogen-containing silicone oil, 1 part of polysilazane resin, 12 parts of hydrophobic fumed silica, 6 parts of hexamethyldisilazane and 2 parts of distilled water to a mixer and mix with the lid open for 20-30 minutes to obtain the first mixture. (2) Add 8 parts, 8 parts, 6 parts and 6 parts of hydrophobic fumed silica to the first mixture in batches, purge with nitrogen for protection, mix with the lid open for 20-30 minutes and then cool at room temperature for 12 hours to obtain the second mixture; (3) The second mixture is mixed in a nitrogen atmosphere and heated to 120°C and then vacuum treated with a vacuum degree of 0.06~0.08MPa for 6 hours to obtain the third mixture; (4) Cool the third mixture to room temperature, add 1 part of nano iron oxide and 1 part of fumed titanium dioxide and knead for 20-40 minutes. After cooling to room temperature, re-knead and filter in a filter using a 300-mesh stainless steel mesh to obtain the fourth mixture. (5) Add 2.1 parts of a two-component platinum catalyst to the fourth mixture and mix evenly at room temperature to obtain a low-volatile, high-heat-resistant, flame-retardant silicone rubber.

[0069] The low-volatile, high-heat-resistant, flame-retardant silicone rubbers prepared in Examples 1-5 and Comparative Examples 1-9 were placed in a flat vulcanizing agent and treated at 120°C for 10 minutes to obtain vulcanized rubber, which served as test samples.

[0070] The vulcanized rubber test samples prepared in Examples 1-5 and Comparative Examples 1-9 were tested for density, hardness, tensile strength, elongation, UL94 vertical flammability rating, volatile matter, thermal decomposition temperature, and amount of oily substances released. The specific testing equipment and standards are shown in Table 1, and the test results are shown in Table 2.

[0071] Table 1 Test Equipment and Standards

[0072] The test method for volatile matter includes: taking 10 grams of vulcanized sample, placing it in a forced-air drying oven, and drying it at 200℃ for 4 hours. Then, removing the sample and weighing it to obtain the weight after drying. Volatile matter = (Weight before drying - Weight after drying) / Weight before drying × 100%.

[0073] The test method for the amount of oily substance precipitation includes: taking 10 grams of vulcanized silica gel sample, placing it in a sealed crucible, and then placing the crucible in a muffle furnace at 500℃ for 30 minutes. Afterward, remove the crucible and place it in a drying oven to cool for 30 minutes. Open the crucible, remove the silica gel sample, and wipe the surface of the sample with a clean gauze dipped in a small amount of anhydrous ethanol. Then, place it in a drying oven for 30 minutes and weigh it to obtain the weight after baking. The amount of oily substance precipitation = (weight before baking - weight after baking) / weight before baking × 100% Table 2 Performance test results of Examples 1-5 and Comparative Examples 1-9

[0074] The test results are shown in Table 2. As can be seen from Examples 1-5 and Comparative Examples 1-9, the silicone rubber of the present invention has superior heat resistance and flame retardancy overall, and also has lower volatile content. Further comparison of Examples 1 and Comparative Examples 1-9 shows that when the silicone rubber material is subjected to aging tests, whether treated at 350°C for 72 hours or at 250°C for 60 days, the silicone rubber of the present invention still exhibits superior tensile strength and elongation.

[0075] Further comparison of the data from Examples 1-3 shows that a silicone rubber material with low volatile content and high heat resistance can be obtained when the amount of hydrophobic fumed silica is in the range of 30-50 parts. Comparison of the data from Examples 1, 4, and 5 shows that the performance change from 0.2 parts to 0.8 parts of hydrogen-containing silicone oil is as follows: the heat resistance of the silicone composite material improves with increasing hydrogen-containing silicone oil content, but when the amount of hydrogen-containing silicone oil reaches 0.8 parts, the heat resistance of the silicone composite material begins to decrease. This indicates that only a suitable amount of Si-H in a high-temperature environment can eliminate excess hydroxyl groups on silicone or hydrophobic fumed silica, improving heat resistance. However, when Si-H is excessive, it leads to over-crosslinking and reduces heat resistance.

[0076] Data from Example 1 and Comparative Examples 1-4 show that methylphenyl vinyl silicone rubber plays a crucial role in the heat resistance of silicone rubber materials. Hydroxyl silicone oil is the main factor leading to the precipitation of oily substances in high-temperature environments. This demonstrates that the synergistic treatment process of hexamethyldisilazane and polysilazane resin in this invention not only achieves better heat resistance but also solves the problem of oily substance precipitation in high-temperature environments.

[0077] Data from Examples 1 and Comparative Examples 5-8 show that polysilazane resin has a significant effect on improving the thermal decomposition temperature and flame retardant properties of silicone rubber materials. When polysilazane resin, fumed titanium dioxide, and nano-cerium oxide are used in combination, a significant synergistic effect is observed in both flame retardant properties and the improvement of thermal decomposition temperature. Specifically, when the silicone rubber of this invention is subjected to combustion and high-temperature aging environments, the polysilazane resin begins to crosslink, solidify, and decompose, generating an amorphous ceramic layer in situ, providing a basic framework for the entire protective layer. However, this basic framework is not dense enough. Simultaneously, the silicone rubber rapidly chars under the synergistic catalytic action of fumed titanium dioxide and nano-cerium oxide. This char seamlessly embeds into the ceramic framework formed by the polysilazane, filling pores and making the protective layer more dense. Furthermore, the fumed titanium dioxide dispersed in the ceramic framework significantly improves the mechanical strength and thermal shock resistance of the ceramic layer, preventing cracking and detachment of the ceramicized layer during flame impact resistance. At the same time, the nitrogen element provided by the polysilazane resin achieves a synergistic flame retardant effect between the solidified phase and the gas phase. Therefore, this invention achieves flame retardancy and high-temperature oxidation protection by synergistically combining fumed titanium dioxide, nano-cerium oxide, and polysilazane resin to form a dense Si-OC protective layer in a high-temperature environment.

[0078] The data from Example 1 and Comparative Example 9 show that when nano iron oxide is used instead of nano cerium oxide, although the strength retention rate after aging test can be maintained at over 80%, the overall heat resistance is not as good as that of nano cerium oxide. Moreover, the appearance of nano iron oxide is black, which limits its application for applications where appearance is important.

[0079] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, it is not limited to those listed in the embodiments. Those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A low-volatile, high-heat-resistant, flame-retardant silicone rubber, characterized in that, The raw materials, by weight, include: 100 parts methylphenyl vinyl silicone rubber raw rubber, 20-70 parts hydrophobic fumed silica, 3-15 parts structuring control agent, 1-10 parts flame retardant and heat resistant agent, 0.2-0.8 parts hydrogen-containing silicone oil, and 1.5-2.5 parts two-component platinum catalyst. The flame retardant and heat resistant agent includes fumed titanium dioxide, cerium oxide, and polysilazane resin. The structuring control agent is hexamethyldisilazane and water. The mass ratio of the fumed titanium dioxide, cerium oxide, and polysilazane resin is 1-3:1-3:1-3. The specific surface area of ​​the fumed titanium dioxide is 35-65 m². 2 / g, wherein the particle size of the cerium oxide is 1~10μm, and the molecular weight of the polysilazane resin is 5000~8000g / mol.

2. The low-volatile, high-heat-resistant, flame-retardant silicone rubber according to claim 1, characterized in that, The two-component platinum catalyst comprises component A and component B in a weight ratio of 0.5~1:1~1.

5. Component A is a platinum catalyst with a platinum content of 300 ppm. Component B consists of a crosslinking agent and an inhibitor in a weight ratio of 25~40:0.5~1.

5.

3. The low-volatile, high-heat-resistant, flame-retardant silicone rubber according to claim 1, characterized in that, The methylphenyl vinyl silicone rubber raw rubber has a molecular weight of 580,000 to 650,000, a molar fraction of (C6H5)CH3SiO repeating units of 10 to 20%, and a molar fraction of vinyl groups of 0.2 to 0.5%.

4. The low-volatile, high-heat-resistant, flame-retardant silicone rubber according to claim 1, characterized in that, The mass ratio of the hexamethyldisilazane to the water is 2.5 to 4.5:

1.

5. The low-volatile, high-heat-resistant, flame-retardant silicone rubber according to claim 1, characterized in that, The specific surface area of ​​the hydrophobic fumed silica is 200 m². 2 / g, wherein the active hydrogen content in the hydrogen-containing silicone oil is 0.45%~1.5% by mass.

6. A method for preparing low-volatile, high-heat-resistant, flame-retardant silicone rubber according to any one of claims 1 to 5, characterized in that, Including the following steps: (1) The methyl phenyl vinyl silicone rubber, the hydrogen-containing silicone oil, the polysilazane resin, the structure control agent and a portion of the hydrophobic fumed silica are fed into a mixer and mixed to obtain a first mixture; (2) Add the remaining portion of the hydrophobic fumed silica to the first mixture, mix them evenly in a protective atmosphere, and then cool them at room temperature to obtain the second mixture; (3) The second mixture is mixed in a protective atmosphere and heated to a certain temperature, and then vacuum treated to obtain the third mixture; (4) Cool the third mixture to room temperature, add the cerium oxide and the fumed titanium dioxide and knead, cool to room temperature and then knead and filter to obtain the fourth mixture; (5) Add the two-component platinum catalyst to the fourth mixture and mix evenly at room temperature to obtain a low-volatile, high-heat-resistant, flame-retardant silicone rubber.

7. The method for preparing low-volatile, high-heat-resistant, flame-retardant silicone rubber according to claim 6, characterized in that, In step (1), the amount of hydrophobic fumed silica added accounts for 30% of the total mass of the hydrophobic fumed silica. In step (2), the remaining hydrophobic fumed silica is added in four portions, and the amount of the remaining hydrophobic fumed silica added accounts for 20%, 20%, 15%, and 15% of the total mass of the hydrophobic fumed silica, respectively.

8. The method for preparing low-volatile, high-heat-resistant, flame-retardant silicone rubber according to claim 6, characterized in that, In step (3), the mixing temperature is raised to 110~130℃, the vacuum degree of the vacuum treatment is 0.06~0.08MPa, and the vacuum treatment time is 4~8h.

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