A silicone rubber having thermal stability and a method for preparing the same

Abstract

The application relates to the field of silicone rubber preparation, and particularly discloses a silicone rubber with thermal stability and a preparation method thereof. The silicone rubber with thermal stability comprises the following raw materials in parts by weight: 100 parts of a silicone rubber matrix, 2-6 parts of hydroxyl silicone oil, 1-2.5 parts of a vulcanizing agent, 20-50 parts of white carbon black, 1-5 parts of a coupling agent, 5-10 parts of a thermal stabilizer, 10-40 parts of a flame retardant, and 4-10 parts of a toughening and reinforcing agent. The thermal stabilizer comprises active spherical silicon sol, cage-shaped oligomeric silsesquioxane grafted CeO2 and kaolin loaded Fe2O3 in a mass ratio of 3:0.5-0.7:1.5-2.1. The toughening and reinforcing agent comprises carboxylated PVDF nanofibers and modified metal organic framework materials in a mass ratio of 1:0.1-0.3. The silicone rubber has the advantages of good mechanical properties and strong high-temperature stability.

Description

Technical Field

[0001] This application relates to the field of silicone rubber preparation technology, and more specifically, to a thermally stable silicone rubber and its preparation method. Background Technology

[0002] Silicone rubber is a special synthetic rubber. Unlike ordinary rubber with its C-C bonds, the main chain of silicone rubber has a Si-O inorganic structure, making it a semi-inorganic, saturated, heterochain, non-polar elastomer. It is a type of elastomer with organic side groups, possessing excellent high and low temperature resistance, weather resistance, electrical insulation, and physiological inertness. It is widely used in electronics, aerospace, machinery manufacturing, medical and health fields, and also has extensive applications in daily life. Ordinary silicone rubber has a service temperature range of -50℃ to 200℃. Under high-temperature conditions, silicone rubber easily decomposes, releasing free oxygen free radicals that attack the silicone rubber molecular backbone, causing the rubber molecular structure to decompose and leading to high-temperature aging, rendering it unusable. With continuous technological development, the application fields of silicone rubber are becoming increasingly broad, placing higher demands on its high-temperature resistance and aging resistance. Traditional silicone rubber can no longer meet the requirements for use under higher temperature conditions; it quickly becomes brittle above 250℃, and its physical properties decline sharply.

[0003] The thermal degradation of silicone rubber is mainly caused by two reactions: main chain degradation and side group oxidation. Metal oxides such as cerium oxide and iron oxide can prevent the chain growth of thermally oxidized free radicals in silicone rubber through electron transfer reactions, and are therefore often used as heat-resistant additives for silicone rubber. For example, invention patent CN113278290A discloses a high-temperature resistant silicone rubber and its preparation method, using polydimethylsiloxane, cerium oxide, lanthanum oxide, nano-alumina, and iron oxide as heat-resistant agents to reduce the possibility of unwinding main chain degradation reactions in silicone rubber and synergistically improve its high-temperature resistance. However, metal oxides can only keep silicone rubber stable at around 300℃ and cannot withstand higher temperatures. Furthermore, metal oxides have poor compatibility with the silicone rubber matrix, which can easily affect the mechanical properties of silicone rubber. Summary of the Invention

[0004] To improve the high-temperature stability and mechanical properties of silicone rubber, this application provides a thermally stable silicone rubber and its preparation method.

[0005] In a first aspect, this application provides a thermally stable silicone rubber, employing the following technical solution:

[0006] A thermally stable silicone rubber comprises the following raw materials in parts by weight:

[0007] 100 parts silicone rubber matrix, 2-6 parts hydroxyl silicone oil, 1-2.5 parts vulcanizing agent, 20-50 parts silica, 1-5 parts coupling agent, 5-10 parts heat stabilizer, 10-40 parts flame retardant, and 4-10 parts toughening and reinforcing agent.

[0008] The silicone rubber matrix comprises methyl vinyl silicone rubber and fluorosilicone rubber in a mass ratio of 6-7:2.5-3;

[0009] The heat stabilizer comprises active spherical silica sol, cage-shaped oligomeric silsesquioxane grafted CeO2, and kaolin-supported Fe2O3 in a mass ratio of 3:0.5-0.7:1.5-2.1.

[0010] The toughening and reinforcing agent comprises carboxylated PVDF nanofibers and modified metal-organic framework materials in a mass ratio of 1:0.1-0.3.

[0011] By adopting the above technical solution, with fluorosilicone rubber and methyl vinyl silicone rubber as the main matrix, fluorosilicone rubber has good chemical stability, a wide temperature range, and better radiation aging resistance than methyl vinyl silicone rubber. Moreover, the fluorine atoms in the molecular structure of fluorosilicone rubber help to improve the rigidity and hardness of its molecular chain, thereby improving the tear resistance and tensile strength of the blend system.

[0012] Using carboxylated PVDF nanofibers as a toughening and reinforcing agent, the introduction of carboxylation enables the grafting of active functional groups onto the PVDF nanofibers. These functional groups can react chemically with the silicone rubber matrix, forming chemical bonds or hydrogen bonds. Furthermore, the introduction of carboxyl groups on the surface of PVDF nanofibers improves their surface chemical properties, making them more readily interact with the silicone rubber matrix, enhancing their compatibility and dispersibility, and reducing agglomeration. The strong interfacial interaction between the carboxyl groups and the silicone rubber matrix, along with their good dispersion within the silicone rubber, allows the carboxylated PVDF nanofibers to fully utilize their free radical scavenging capabilities. The active hydrogen atoms in the carboxyl groups can react with free radicals to form alkyl free radical intermediates, effectively blocking free radical reactions and thus inhibiting the oxidative crosslinking reaction of silicone rubber, reducing its thermal oxidation.

[0013] Cage-shaped oligomeric silsesquioxane (POSS) is a molecular-level organic / inorganic hybrid material with a hexahedral inorganic framework core of Si-O-Si nanostructure surrounded by organic groups. It exhibits a nanoscale effect and excellent thermal stability. Moreover, the nanoscale size and uniform particle size of POSS make it easier to achieve molecular-level dispersion in silicone rubber matrix, thereby reducing cerium oxide agglomeration, improving cerium oxide dispersibility, and reducing the impact of heat stabilizers on the mechanical properties of silicone rubber materials. Furthermore, the introduction of POSS significantly improves the thermal stability and mechanical strength of silicone rubber while also reducing the impact of the addition of metal oxides on silicone rubber.

[0014] In kaolin-loaded Fe2O3, kaolin is a layered material with a large specific surface area and certain adsorption capacity, which can significantly improve the mechanical strength, wear resistance and chemical stability of silicone rubber. Its layered structure and good fluidity make it easy to disperse in rubber materials and form a uniform dispersion system. The Fe2O3 particles loaded on the surface of kaolin form steric hindrance, which reduces the agglomeration of Fe2O3 particles. Therefore, it reduces the impact of metal oxide addition on the mechanical strength of silicone rubber. Moreover, the addition of kaolin can also improve the thermal aging ability of silicone rubber to a certain extent.

[0015] Fe in the metal compound Fe2O3 and CeO2 3+ and Ce 4+ It can undergo redox reactions with these free radicals and produce inactive R. + And low-valence metal ions Fe 2+ and Ce 3+ This process involves the transfer of a single electron, while the low-valence metal ion Fe... 2+ and Ce 3+ It can also react with oxygen and be oxidized to Fe in a higher oxidation state. 3+ and Ce 4+ This reaction continues, inhibiting the side group oxidative crosslinking reaction of silicone rubber, and ultimately improving the heat resistance of silicone rubber. Therefore, adding Fe2O3 or CeO2 can significantly improve the heat resistance of silicone rubber.

[0016] Optionally, the modified metal-organic framework material is prepared using the following method:

[0017] The metal-organic framework material was acidified and then added to deionized water, and ultrasonically homogenized to obtain a dispersion.

[0018] Tin chloride pentahydrate and antimony trichloride were mixed and added to hydrochloric acid solution. The dispersion was added dropwise, and ammonia water was added dropwise at the same time. After the addition was completed, the mixture was stirred continuously for 1-2 hours. The mixture was then filtered, washed, dried, and calcined to obtain the coated material.

[0019] The coating material was added to an ethanolamine solution, sonicated, filtered, washed, and dried to obtain a modified metal-organic framework material.

[0020] Metal-organic frameworks (MOFs) possess antioxidant properties, capable of capturing free radicals and inhibiting oxidation reactions. Therefore, when combined with silicone rubber, they can slow down the oxidative aging rate of silicone rubber. Furthermore, MOFs exhibit high thermal stability, maintaining structural stability at high temperatures, thereby reducing thermal aging. ATO containing Sn was coated onto the MOF using an in-situ chemical precipitation method. 4+ and Sb 3+ A hydrochloric acid mixture was slowly added dropwise to the dispersion. With the addition of hydrochloric acid, the pH increased, and Sn... 4+ and Sb 3+ Hydrolysis begins, producing the positively charged hydrolysis product Sn(OH). 4-n n+ and SbO + After acidification, metal-organic frameworks (MOR) acquire a negative surface charge, allowing them to adsorb hydrolysis products onto their surface via electrostatic adsorption. The precipitated material forms a coating layer on the MOR surface. Ethanolamine is then used to modify the coating. Due to the coordination between amines and metal ions, ethanolamine adsorbs onto the coating surface, forming a strong N-Sb(Sn) bond between ethanolamine and the ATO surface. The ATO-coated MOR exhibits strong dispersibility due to the steric repulsion provided by the alkyl segments of ethanolamine between particles, resulting in more uniform dispersion in silicone rubber. Furthermore, the high thermal stability of ATO coating on the MOR, when added to silicone rubber, helps maintain molecular chain stability at high temperatures, reducing degradation reactions. ATO also possesses antioxidant properties, slowing down the oxidation rate of silicone rubber at high temperatures and extending its service life.

[0021] Optionally, the amount of Fe2O3 loaded with kaolin is three times the amount of CeO2 grafted onto cage-like oligomeric silsesquioxane.

[0022] By adopting the above technical solution, Fe2O3 is incorporated into silicone rubber at a dosage of 3 times that of CeO2, which can more effectively improve the heat resistance and anti-aging effect of silicone rubber.

[0023] Optionally, the method for preparing the carboxylated PVDF nanofibers includes the following steps:

[0024] PVDF and ethylene maleic anhydride copolymer are mixed and added to a solvent prepared by mixing DMA and acetone in a volume ratio of 3:2. Copper oxide is added, the temperature is raised to 50-60℃, and the mixture is stirred for 10-12 hours to obtain a spinning solution. The amounts of copper oxide and ethylene maleic anhydride copolymer are 5-9 wt% and 15-20 wt% of the mass of PVDF, respectively.

[0025] Nanofiber membranes were prepared by electrospinning the spinning solution, vacuum drying at 50-60℃, and then immersed in sulfuric acid solution, washed, and vacuum dried to obtain carboxylated PVDF nanofibers.

[0026] By adopting the above technical solution, PVDF (polyvinylidene fluoride) possesses excellent weather resistance, corrosion resistance, good wear resistance, flexibility, and impact strength. It is mixed with ethylene-maleic anhydride copolymer and copper oxide as a spinning solution. After spinning, the mixture is soaked in acid to hydrolyze all the anhydride bonds in the membrane into carboxyl groups, resulting in PVDF nanofibers rich in carboxyl groups. Copper oxide also enhances the thermal stability of silicone rubber. Therefore, the carboxyl groups in the prepared carboxylated PVDF nanofibers ensure uniform dispersion of the PVDF nanofibers in silicone rubber, generating strong interfacial interactions and increasing the initial tensile strength and breaking strength of silicone rubber. Simultaneously, it blocks free radicals and inhibits oxidative crosslinking reactions. Copper oxide further improves the thermal oxidation resistance of silicone rubber to a certain extent, enhancing its thermal stability.

[0027] Optionally, carbon nanotubes are also added to the spinning solution, with the ratio of carbon nanotubes to PVDF being 0.01-0.1:1.

[0028] By adopting the above technical solution, carbon nanotubes exhibit excellent high-temperature resistance and thermal conductivity. After being blended with spinning solution and acidified with sulfuric acid, they acquire carboxyl groups on their surface, thereby enhancing their interaction with the silicone rubber matrix and improving thermal stability. Copper oxide in the spinning solution acts as a barrier, separating the carbon nanotubes and increasing the inter-tube distance, thus weakening the van der Waals forces and π-π interactions between them. Consequently, the mutual attraction between carbon nanotubes in the spinning solution is reduced, resulting in better dispersibility. Furthermore, due to the addition of carbon nanotubes, the particle size of copper oxide decreases, improving dispersibility and increasing the specific surface area, which enhances its interaction with silicone rubber. Therefore, the combination of these two technologies further improves the thermo-oxidative stability of silicone rubber. Moreover, the addition of carbon nanotubes increases the interaction area between PVDF nanofibers and the silicone rubber matrix, and strengthens the interfacial adhesion between carboxylated PVDF nanofibers and the silicone rubber matrix.

[0029] Optionally, the method for preparing the cage-shaped oligomeric silsesquioxane grafted with CeO2 is as follows:

[0030] CeO2 was added to an acetic acid solution, stirred at 50-70℃ for 3-4 hours, filtered, and dried to obtain acidified CeO2.

[0031] Add acidified CeO2 to tetrahydrofuran, add N,N-carbonyldiimidazole, heat to 60-70℃, stir for 3-5 h, then add aminated cage-like oligomeric silsesquioxane, purge with nitrogen gas, and react at 60-70℃ for 10-12 h, filter, and vacuum dry at 60-70℃.

[0032] By employing the above technical solution, CeO2 reacts with acetic acid, allowing the acetic acid to react with the CeO2 surface, grafting carboxyl groups onto the cerium oxide particles. Then, N,N-carbonyldiimidazole is added, grafting imidazole groups onto the carboxyl groups. Next, an aminated cage-like oligomeric silsesquioxane reacts with the imidazole groups to obtain the final cage-like oligomeric silsesquioxane grafted CeO2. The POSS surface has a large number of polar groups, effectively promoting the miscibility of CeO2 in silicone rubber. Furthermore, POSS, with its three-dimensional cage-like inorganic framework as its core, exhibits excellent thermal stability at high temperatures. The main process involves the decomposition of alkyl chains on POSS, while the inorganic core Si-O-Si bonds only break at higher temperatures. The decomposition of the organic part of POSS itself consumes some heat, slowing down the decomposition rate. During the degradation process, the decomposition into SiO2 can form a deposit, partially forming a protective layer on the surface of cerium oxide. This slows down heat transfer to a certain extent, inhibits the volatilization of flammable gases, and prevents the mixing of flammable gases and oxygen. POSS gradually migrates to the surface of cerium oxide to form a barrier layer with high thermal stability, improving the thermo-oxygen stability of the particles.

[0033] Optionally, the kaolin loaded with Fe2O3 is prepared by the following method:

[0034] Kaolin was added to anhydrous ethanol and stirred evenly. Then, silane coupling agent KH560 was added and stirred for 40-60 minutes. After drying, modified kaolin was obtained. The mass ratio of silane coupling agent to kaolin was 8-10:1.

[0035] CF4 and N2 in a volume ratio of 25:1 were used as a mixed gas to fluorinate kaolin for 15-20 minutes to obtain fluorinated kaolin.

[0036] Fluorinated kaolin is impregnated in a 10% ferric nitrate solution, allowed to stand for 10-12 hours, then heated to 60-65℃, allowed to stand for 5-6 hours, and the pH is adjusted until precipitation occurs. The precipitate is then filtered, washed until neutral, dried, and heated to 400-450℃ under nitrogen protection, and held at that temperature for 1-1.5 hours.

[0037] By adopting the above technical solution, kaolin is first surface-modified using the silane coupling agent KH560 to improve the interfacial force between kaolin and silicone rubber, thereby improving mechanical strength and enhancing thermal stability. Then, a mixture of CF4 and N2 is used for plasma fluorination treatment. CF4 acts as the plasma discharge gas, while nitrogen, with its relatively stable chemical properties, serves as a protective gas, providing excited states for the reaction and simultaneously impacting the kaolin surface to open chemical bonds. During plasma discharge, high-energy particles accumulate on the dielectric surface and collide with CF4 molecules, causing CF4 to fluorinate. Four molecules ionize to form fluorine-containing free radicals. These free radicals then react with pre-grafted groups on the surface of kaolin, effectively introducing fluorine into the kaolin surface. This effectively inhibits the aggregation of kaolin in the matrix, achieving uniform dispersion. After fluorination treatment, the average particle size of kaolin decreases and the surface roughness increases, resulting in more uniform dispersion in the silicone rubber matrix and increased bonding strength with silicone rubber. Next, kaolin is impregnated with ferric nitrate solution for fluorination treatment. After adjusting the pH and high-temperature treatment, ferric nitrate forms Fe₂O₃, and the Fe₂O₃ contains Fe... 3+ It can undergo redox reactions with the free radicals generated by the oxidative crosslinking and degradation of silicone rubber at high temperatures, producing inactive R... + And low-valence metal ions Fe 2+ Fe, a metal ion in a low valence state 2+ It can also react with oxygen and be oxidized to Fe in a higher oxidation state. 3+ It continuously inhibits the side group oxidative crosslinking reaction of silicone rubber and improves its heat resistance.

[0038] Optionally, the specific method for the plasma fluorination treatment is as follows: modified kaolin is loaded into a reactor, and a vacuum is drawn to 2.8 × 10⁻⁶. -3 Pa, then a mixture of CF4 and N2 was introduced to raise the internal pressure to 10 kPa, and then a vacuum was evacuated again to 2.8 × 10 Pa. - 3 Pa, and finally a mixture of CF4 and N2 is introduced until the internal pressure stabilizes at 13.5 kPa, with a voltage of 24 kV and a frequency of 9 kHz applied.

[0039] By adopting the above technical solution, the above parameters can effectively activate the surface groups of kaolin, promote the generation of new chemical bonds and the grafting reaction of functional groups, and have high electrochemical activity, with the advantages of high efficiency, safety and stability.

[0040] Optionally, the vulcanizing agent is any one of 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane, 2,4-dichlorobenzoyl peroxide, or tert-butyl perbenzoate;

[0041] The flame retardant is selected from at least one of ammonium polyphosphate, magnesium hydroxide, and aluminum hydroxide;

[0042] The coupling agent is selected from at least one of A151 coupling agent, A171 coupling agent, KH550 coupling agent, and KH560 coupling agent.

[0043] Secondly, this application provides a method for preparing thermally stable silicone rubber, using the following technical solution:

[0044] A method for preparing thermally stable silicone rubber includes the following steps:

[0045] The silicone rubber matrix, silica and hydroxyl silicone oil are mixed at 80-100℃ for 20-30 minutes. Coupling agent, toughening and reinforcing agent, heat stabilizer and flame retardant are added and mixed at 80-100℃ for 1-1.5 hours. Then vacuum is applied for 30-40 minutes with a vacuum degree of -0.07MPa to obtain the rubber compound.

[0046] Mix the rubber compound with the vulcanizing agent and knead at 120-130℃ for 1-2 hours. Then, pass the mixture through a thin sheet to form a compounded rubber.

[0047] The compound is vulcanized at 160-170℃ and 25-30MPa for 10-20 minutes, then vulcanized at 180-190℃ for 2-4 hours, and cooled to room temperature to produce a thermally stable silicone rubber.

[0048] By adopting the above technical solution, the silicone rubber matrix is ​​first mixed with silica and other materials to increase the uniformity of mixing of each raw material, and then mixed with coupling agents and other materials. The coupling agents can increase the compatibility of the silicone rubber matrix with toughening and reinforcing agents and heat stabilizers. Finally, it is mixed with a vulcanizing agent and vulcanized twice to obtain a silicone rubber material with excellent thermal stability.

[0049] In summary, this application has the following beneficial effects:

[0050] 1. This application uses methyl vinyl silicone rubber and fluorosilicone rubber as the silicone rubber matrix. Fluorosilicone rubber has a wide temperature resistance range and contains fluorine atoms, which can improve the tear resistance and tensile strength of the finished silicone rubber material. In addition, carboxylated PVDF nanofibers and modified metal-organic framework materials are used as toughening and reinforcing agents. The introduced carboxyl groups can react chemically with the silicone rubber matrix and improve its dispersibility and compatibility in the silicone rubber matrix, reduce agglomeration, and enhance the mechanical strength of the silicone rubber material. The metal-organic framework material is loaded with ATO, which further improves the thermal stability. The heat stabilizers are active spherical silica sol, cage-like oligomeric silsesquioxane grafted CeO2 and kaolin loaded with Fe2O3. Cage-like oligomeric silsesquioxane can improve the dispersibility of cerium oxide, reduce agglomeration, and improve the mechanical strength of silicone rubber. The loading of kaolin can also reduce the agglomeration of ferric oxide and increase its dispersibility. Cerium oxide and ferric oxide can work together to inhibit the oxidative crosslinking degradation reaction of silicone rubber and enhance its thermal stability.

[0051] 2. In this application, PVDF and ethylene maleic anhydride copolymer, copper oxide and carbon nanotubes are preferably mixed, electrospun and then acidified to obtain carboxylated PVDF nanofibers. Copper oxide and carbon nanotubes can cooperate with each other to reduce their agglomeration and disperse evenly in PVDF nanofibers. During acidification, carbon nanotubes can also introduce carboxyl groups on their surface, which increases the interaction between PVDF nanofibers and silicone rubber and improves thermal stability.

[0052] 3. In this application, kaolin is preferably treated with silane coupling agent KH560, and then plasma fluorination is performed with a mixture of CF4 and N2 to graft CF2 onto its surface, so as to reduce the particle size of kaolin, increase its surface roughness, improve the dispersion of particles in silicone rubber material, increase the interfacial compatibility between the two, and increase the loading of ferric oxide. Detailed Implementation

[0053] The following embodiments provide a further detailed description of this application.

[0054] Preparation Examples of Carboxylated PVDF Nanofibers 1-4

[0055] In Preparation Example 1, the Mw of PVDF was 500,000, the Mw of ethylene-maleic anhydride copolymer was 50,000, and the carbon nanotubes were selected from Xianfeng Nano, catalog number 100252, catalog number XFM13.

[0056] Preparation Example 1: 20g of PVDF and ethylene maleic anhydride copolymer were mixed and added to a solvent prepared by mixing DMA and acetone in a volume ratio of 3:2. Copper oxide and carbon nanotubes were added, the temperature was raised to 50℃, and the mixture was stirred for 12h to obtain a spinning solution. The amounts of copper oxide and ethylene maleic anhydride copolymer were 9wt% and 20wt% of the mass of PVDF, respectively, and the mass ratio of carbon nanotubes to PVDF was 0.1:1.

[0057] Nanofiber membranes were prepared by electrospinning the spinning solution, dried under vacuum at 50°C, and then immersed in a 0.1 mol / L sulfuric acid solution. After washing and vacuum drying, carboxylated PVDF nanofibers were obtained. The spinning voltage was 15 kV, the solution flow rate was 0.5 mL / h, and the receiving distance was 15 cm.

[0058] Preparation Example 2: 20g of PVDF and ethylene maleic anhydride copolymer were mixed and added to a solvent prepared by mixing DMA and acetone in a volume ratio of 3:2. Copper oxide and carbon nanotubes were added, the temperature was raised to 60℃, and the mixture was stirred for 10h to obtain a spinning solution. The amounts of copper oxide and ethylene maleic anhydride copolymer were 5wt% and 15wt% of the mass of PVDF, respectively, and the mass ratio of carbon nanotubes to PVDF was 0.01:1.

[0059] Nanofiber membranes were prepared by electrospinning the spinning solution, dried under vacuum at 60°C, and then immersed in a 0.1 mol / L sulfuric acid solution. After washing and vacuum drying, carboxylated PVDF nanofibers were obtained. The spinning voltage was 15 kV, the solution flow rate was 0.5 mL / h, and the receiving distance was 15 cm.

[0060] Preparation Example 3: The difference from Preparation Example 1 is that an equal amount of copper oxide was used instead of carbon nanotubes.

[0061] Preparation Example 4: The difference from Preparation Example 1 is that an equal amount of carbon nanotubes were used instead of copper oxide.

[0062] Preparation Example 5: The difference from Preparation Example 1 is that carbon nanotubes and copper oxide were not added.

[0063] Preparation Examples of Cage-shaped Oligomeric Silsesquioxane Grafted CeO2 (Examples 6-9)

[0064] Preparation Example 6: 10g CeO2 was added to an acetic acid solution with a concentration of 0.1mol / L, stirred at 50℃ for 4h, filtered, and dried at 60℃ to obtain acidified CeO2;

[0065] Add acidified CeO2 to 250 ml of tetrahydrofuran, add 10 g of N,N-carbonyldiimidazole, heat to 60 °C, stir for 5 h, then add 10 g of amino-coated cage-like oligomeric silsesquioxane, purge with nitrogen gas, and react at 60 °C for 12 h, filter, and vacuum dry at 60 °C for 72 h.

[0066] Preparation Example 7: 10g CeO2 was added to an acetic acid solution with a concentration of 0.1mol / L, stirred at 70℃ for 3h, filtered, and dried at 60℃ to obtain acidified CeO2;

[0067] Add acidified CeO2 to 300 ml tetrahydrofuran, add 10 g N,N-carbonyldiimidazole, heat to 70 °C, stir for 3 h, then add 10 g aminocage-shaped oligomeric silsesquioxane, purge with nitrogen gas, react at 70 °C for 10 h, filter, and vacuum dry at 70 °C for 72 h.

[0068] Preparation Example 8: The difference from Preparation Example 6 is that N,N-carbonyldiimidazole was not added. The specific method is as follows: 10g of CeO2 was added to an acetic acid solution with a concentration of 0.1mol / L, stirred at 50°C for 4h, filtered, and dried at 60°C to obtain acidified CeO2.

[0069] Add acidified CeO2 to 250 ml of tetrahydrofuran, heat to 60 °C, stir for 5 h, then add 10 g of amino-coated cage-like oligomeric silsesquioxane, purge with nitrogen, and react at 60 °C for 12 h, filter, and vacuum dry at 60 °C for 72 h.

[0070] Preparation Example 9: The difference from Preparation Example 6 is that CeO2 was not acidified. The specific method is as follows: 10g CeO2 was added to 250ml tetrahydrofuran, 10g N,N-carbonyldiimidazole was added, the temperature was raised to 60℃, and the mixture was stirred for 5h. Then 10g of aminated cage-like oligomeric silsesquioxane was added, nitrogen gas was introduced, and the reaction was carried out at 60℃ for 12h. The mixture was then filtered and dried under vacuum at 60℃ for 72h.

[0071] Preparation of Fe2O3 supported on kaolin (Examples 10-13)

[0072] Preparation Example 10: 10g of kaolin was added to 100g of anhydrous ethanol, stirred at 4500r / min for 20min, then silane coupling agent KH560 was added, the temperature was raised to 70℃, stirring was continued for 40min, and then dried at 80℃ for 48h to obtain modified kaolin. The mass ratio of silane coupling agent to kaolin was 10:1.

[0073] Modified kaolin was loaded into the reactor, and a vacuum of 2.8 × 10⁻⁶ was applied. -3Pa, then a mixture of CF4 and N2 with a volume ratio of 25:1 was introduced to raise the internal pressure to 10 kPa, and then a vacuum was evacuated again to 2.8 × 10 Pa. -3 Pa, and finally, a mixture of CF4 and N2 with a volume ratio of 25:1 is introduced until the internal pressure stabilizes at 13.5 kPa. A voltage of 24 kV and a frequency of 9 kHz are applied to kaolin for plasma fluorination treatment for 20 min to obtain fluorinated kaolin.

[0074] Fluorinated kaolin was impregnated in a 10% ferric nitrate solution, allowed to stand for 12 hours, then heated to 60°C, allowed to stand for 6 hours, and the pH was adjusted to 7 by adding 1 mol / L ammonia. The mixture was then filtered, rinsed until neutral, dried at 110°C for 12 hours, and then heated to 400°C under nitrogen protection and held at that temperature for 1 hour.

[0075] Preparation Example 11: 10g of kaolin was added to 100g of anhydrous ethanol, stirred at 4500r / min for 20min, then silane coupling agent KH560 was added, the temperature was raised to 70℃, stirring was continued for 60min, and then dried at 80℃ for 48h to obtain modified kaolin. The mass ratio of silane coupling agent to kaolin was 8:1.

[0076] Modified kaolin was loaded into the reactor, and a vacuum of 2.8 × 10⁻⁶ was applied. -3 Pa, then a mixture of CF4 and N2 with a volume ratio of 25:1 was introduced to raise the internal pressure to 10 kPa, and then a vacuum was evacuated again to 2.8 × 10 Pa. -3 Pa, and finally, a mixture of CF4 and N2 with a volume ratio of 25:1 is introduced until the internal pressure stabilizes at 13.5 kPa. A voltage of 24 kV and a frequency of 9 kHz are applied to kaolin for plasma fluorination treatment for 15 min to obtain fluorinated kaolin.

[0077] Fluorinated kaolin was impregnated in a 10% ferric nitrate solution, allowed to stand for 10 hours, then heated to 65°C, allowed to stand for 5 hours, and 1 mol / L ammonia was added to adjust the pH to 7. The mixture was then filtered, rinsed until neutral, dried at 110°C for 12 hours, and then heated to 450°C under nitrogen protection and held at that temperature for 1.5 hours.

[0078] Preparation Example 12: The difference from Preparation Example 10 is that the kaolin was not modified with silane coupling agent KH560, and the kaolin was directly subjected to plasma fluorination treatment. The rest of the operation was the same as in Preparation Example 10.

[0079] Preparation Example 13: The difference from Preparation Example 10 is that the modified kaolin was not subjected to plasma fluorination treatment, and the modified kaolin treated with silane coupling agent KH550 was directly impregnated in ferric nitrate solution.

[0080] Example 14: 10g of metal-organic framework material was soaked in a 5wt% acetic acid solution for 20min, then filtered, washed until neutral, dried at 60℃ and added to 90g of deionized water. The mixture was then sonicated to obtain a dispersion.

[0081] Tin chloride pentahydrate and antimony trichloride were mixed in a tin to antimony molar ratio of 6:1 and added to a 1.5 mol / L hydrochloric acid solution. The dispersion was added dropwise while ammonia was added dropwise. After the addition was complete, the mixture was stirred for 2 hours, filtered, washed, dried and calcined to obtain the coated material.

[0082] 1g of the coating was added to an ethanolamine solution formed by 2ml of ethanolamine and 500g of deionized water. After sonication for 30min, the mixture was filtered, washed, and dried at 80℃ to obtain the modified metal-organic framework material.

[0083] Example

[0084] Example 1: A thermally stable silica sol, the raw material amounts are shown in Table 1. The silicone rubber matrix includes methyl vinyl silicone rubber and fluorosilicone rubber in a mass ratio of 7:3. The methyl vinyl silicone rubber is selected from Ningbo Ruichen High-Tech New Materials, model 110 raw rubber; the fluorosilicone rubber is selected from Dow Corning, model LS5-2040; the hydroxyl silicone oil is selected from Guangzhou Canxiang Chemical, catalog number Dow Corning PMX-0156; the vulcanizing agent is 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane; the silica is selected from Jiangsu Tianxing New Materials, catalog number TSP-L12; the coupling agent is KH550 coupling agent; the flame retardant is aluminum hydroxide; the toughening and reinforcing agent includes carboxylated PVDF nanofibers and modified metal-organic framework materials in a mass ratio of 1:0.3. The carboxylated PVDF nanofibers are prepared from Example 1. The modified metal-organic framework material was prepared in Preparation Example 14. The heat stabilizers included active spherical silica sol, cage-shaped oligomeric silsesquioxane-grafted CeO2, and kaolin-supported Fe2O3 in a mass ratio of 3:0.5:1.5. The preparation method of the active spherical silica sol was as follows: silica sol was added to acetone, heated to 60°C, and diethylenetetramethyldisilazane was added. After stirring and mixing evenly, the mixture was allowed to stand for 24 hours to allow the diethylenetetramethyldisilazane to react with the hydroxyl groups on the surface of the silica sol, replacing the hydroxyl groups with vinyl groups to prepare active spherical silica sol. The silica sol was selected from Shandong Baite New Materials, model SS3015, with a particle size of 10-15 nm and a silica content of 30±1%. The cage-shaped oligomeric silsesquioxane-grafted CeO2 was prepared in Preparation Example 6, and the kaolin-supported Fe2O3 was prepared in Preparation Example 10.

[0085] The method for preparing the above-mentioned thermally stable silicone rubber includes the following steps:

[0086] The silicone rubber matrix, silica and hydroxyl silicone oil were mixed at 100°C for 20 minutes. Coupling agent, toughening and reinforcing agent, heat stabilizer and flame retardant were added and mixed at 100°C for 1 hour. Then, the mixture was vacuumed for 30 minutes with a vacuum degree of -0.07 MPa to obtain the rubber compound.

[0087] Mix the rubber compound with the vulcanizing agent, knead at 120°C for 2 hours, and then sheet it out to form a compound rubber.

[0088] The compound was vulcanized at 160℃ and 25MPa for 20 minutes, then vulcanized at 180℃ for 4 hours, and cooled to room temperature to produce a thermally stable silicone rubber.

[0089] Table 1. Amount of thermally stable silicone rubber raw material used in Examples 1-4

[0090] Raw materials / kg Example 1 Example 2 Example 3 Example 4 silicone rubber matrix 100 100 100 100 Hydroxy silicone oil 4 6 5 2 vulcanizing agent 2 2.5 1.5 1 precipitate 35 50 40 20 Coupling agent 3.5 5 2 1 Heat stabilizer 8 10 6 5 Flame retardant 30 40 20 10 Toughening and strengthening agents 8 10 6 4

[0091] Example 2: A thermally stable silica sol, with raw material amounts shown in Table 1. The silicone rubber matrix comprises methyl vinyl silicone rubber and fluorosilicone rubber in a mass ratio of 6:2.5. The methyl vinyl silicone rubber is selected from Ningbo Ruichen High-Tech New Materials, model 110 raw rubber; the fluorosilicone rubber is selected from Dow Corning, model LS5-2040; the hydroxyl silicone oil is selected from Guangzhou Canxiang Chemical, catalog number Dow Corning PMX-0156; the vulcanizing agent is 2,4-dichlorobenzoyl peroxide; the silica is selected from Jiangsu Tianxing New Materials, catalog number TSP-L12; the coupling agent is KH560 coupling agent; the flame retardant is magnesium hydroxide; and the toughening and reinforcing agents include carboxylated PVDF nanofibers and modified metal-organic framework materials. The carboxylated PVDF nanofibers are prepared from Preparation Example 2, and the modified metal-organic framework... The framework material was prepared in Preparation Example 14. The heat stabilizers included active spherical silica sol, cage-shaped oligomeric silsesquioxane-grafted CeO2, and kaolin-supported Fe2O3 in a mass ratio of 3:0.7:2.1. The preparation method of the active spherical silica sol was as follows: silica sol was added to acetone, heated to 60°C, and diethylenetetramethyldisilazane was added. After stirring and mixing evenly, the mixture was allowed to stand for 24 hours to allow the diethylenetetramethyldisilazane to react with the hydroxyl groups on the surface of the silica sol, replacing the hydroxyl groups with vinyl groups to prepare active spherical silica sol. The silica sol was selected from Shandong Baite New Materials, model SS3015, with a particle size of 10-15 nm and a silica content of 30±1%. The cage-shaped oligomeric silsesquioxane-grafted CeO2 was prepared in Preparation Example 7, and the kaolin-supported Fe2O3 was prepared in Preparation Example 11.

[0092] The method for preparing the above-mentioned thermally stable silicone rubber includes the following steps:

[0093] The silicone rubber matrix, silica and hydroxyl silicone oil were mixed at 80°C for 30 minutes. Coupling agent, toughening and reinforcing agent, heat stabilizer and flame retardant were added and mixed at 80°C for 1 hour. Then, the mixture was vacuumed for 40 minutes with a vacuum degree of -0.07 MPa to obtain the rubber compound.

[0094] Mix the rubber compound with the vulcanizing agent, knead at 130°C for 1 hour, and then sheet it out to form a compound rubber.

[0095] The compound was vulcanized at 170℃ and 30MPa for 10 minutes, then vulcanized at 190℃ for 2 hours, and cooled to room temperature to produce a thermally stable silicone rubber.

[0096] Example 3: A thermally stable silica sol, with raw material amounts shown in Table 1. The silicone rubber matrix comprises methyl vinyl silicone rubber and fluorosilicone rubber in a mass ratio of 7:2.5. The methyl vinyl silicone rubber is selected from Ningbo Ruichen High-Tech New Materials, model 110 raw rubber; the fluorosilicone rubber is selected from Dow Corning, model LS5-2040; the hydroxyl silicone oil is selected from Guangzhou Canxiang Chemical, catalog number Dow Corning PMX-0156; the vulcanizing agent is tert-butyl perbenzoate; the silica is selected from Jiangsu Tianxing New Materials, catalog number TSP-L12; the coupling agent is A171 coupling agent; the flame retardant is ammonium polyphosphate; and the toughening and reinforcing agents include carboxylated PVDF nanofibers and modified metal-organic framework materials in a 1:0.2 ratio. The carboxylated PVDF nanofibers are prepared from Preparation Example 1, and the modified metal-organic framework... The framework material was prepared in Preparation Example 14. The heat stabilizers included active spherical silica sol, cage-shaped oligomeric silsesquioxane-grafted CeO2, and kaolin-supported Fe2O3 in a mass ratio of 3:0.6:1.8. The preparation method of the active spherical silica sol was as follows: silica sol was added to acetone, heated to 60°C, and diethylenetetramethyldisilazane was added. After stirring and mixing evenly, the mixture was allowed to stand for 24 hours to allow the diethylenetetramethyldisilazane to react with the hydroxyl groups on the surface of the silica sol, replacing the hydroxyl groups with vinyl groups to prepare active spherical silica sol. The silica sol was selected from Shandong Baite New Materials, model SS3015, with a particle size of 10-15 nm and a silica content of 30±1%. The cage-shaped oligomeric silsesquioxane-grafted CeO2 was prepared in Preparation Example 6, and the kaolin-supported Fe2O3 was prepared in Preparation Example 11.

[0097] The method for preparing the above-mentioned thermally stable silicone rubber includes the following steps:

[0098] The silicone rubber matrix, silica and hydroxyl silicone oil were mixed at 90°C for 25 minutes. Coupling agent, toughening and reinforcing agent, heat stabilizer and flame retardant were added and mixed at 100°C for 1 hour. Then, the mixture was vacuumed for 35 minutes with a vacuum degree of -0.07 MPa to obtain the rubber compound.

[0099] Mix the rubber compound with the vulcanizing agent, knead at 125°C for 1.5 hours, and then sheet it out to form a compound rubber.

[0100] The compound was vulcanized at 165℃ and 30MPa for 15 minutes, then vulcanized at 185℃ for 3 hours, and cooled to room temperature to produce a thermally stable silicone rubber.

[0101] Example 4: A thermally stable silicone rubber, which differs from Example 1 in that the amount of raw materials used is shown in Table 1.

[0102] Example 5: A thermally stable silicone rubber, which differs from Example 1 in that the thermal stabilizer includes active spherical silica sol, cage-shaped oligomeric silsesquioxane grafted CeO2, and kaolin-supported Fe2O3 in a mass ratio of 3:0.5:2.

[0103] Example 6: A thermally stable silicone rubber, which differs from Example 1 in that the carboxylated PVDF nanofibers are made from Preparation Example 3.

[0104] Example 7: A thermally stable silicone rubber, which differs from Example 1 in that the carboxylated PVDF nanofibers are made from Preparation Example 4.

[0105] Example 8: A thermally stable silicone rubber, which differs from Example 1 in that the carboxylated PVDF nanofibers are made from Preparation Example 5.

[0106] Example 9: A thermally stable silicone rubber, which differs from Example 1 in that the cage-like oligomeric silsesquioxane grafted CeO2 is prepared in Preparation Example 8.

[0107] Example 10: A thermally stable silicone rubber, which differs from Example 1 in that the cage-like oligomeric silsesquioxane grafted CeO2 is prepared in Preparation Example 9.

[0108] Example 11: A thermally stable silicone rubber, which differs from Example 1 in that the kaolin-loaded Fe2O3 was prepared in Preparation Example 12.

[0109] Example 12: A thermally stable silicone rubber, which differs from Example 1 in that the kaolin-loaded Fe2O3 was prepared in Preparation Example 13.

[0110] Comparative Example

[0111] Comparative Example 1: A thermally stable silicone rubber, which differs from Example 1 in that the thermal stabilizer includes active spherical silica sol, cage-shaped oligomeric silsesquioxane grafted CeO2, and kaolin-supported Fe2O3 in a mass ratio of 3:0.5:1.

[0112] Comparative Example 2: A thermally stable silicone rubber, which differs from Example 1 in that the thermal stabilizer includes active spherical silica sol, cage-shaped oligomeric silsesquioxane grafted CeO2, and kaolin-supported Fe2O3 in a mass ratio of 3:0.5:3.

[0113] Comparative Example 3: A thermally stable silicone rubber, which differs from Example 1 in that no toughening and reinforcing agent was added.

[0114] Comparative Example 4: A thermally stable silicone rubber, which differs from Example 1 in that the thermal stabilizer is nano-alumina.

[0115] Comparative Example 5: A thermally stable silicone rubber, which differs from Example 1 in that the thermal stabilizer comprises active spherical silica sol, CeO2 and kaolin-supported Fe2O3 in a mass ratio of 3:0.5:1.5.

[0116] Comparative Example 6: A thermally stable silicone rubber, which differs from Example 1 in that the thermal stabilizer includes active spherical silica sol, cage-shaped oligomeric silsesquioxane grafted CeO2 and Fe2O3 in a mass ratio of 3:0.5:1.5.

[0117] Comparative Example 7: A thermally stable silicone rubber, which differs from Example 1 in that a cage-like oligomeric silsesquioxane grafted CeO2 is used in the thermal stabilizer to replace kaolin-loaded Fe2O3 in equal amounts. That is, the thermal stabilizer includes active spherical silica sol and cage-like oligomeric silsesquioxane grafted CeO2 in a mass ratio of 3:2.

[0118] Comparative Example 8: A thermally stable silicone rubber, which differs from Example 1 in that the thermal stabilizer uses an equal amount of kaolin-loaded Fe2O3 to replace the cage-like oligomeric silsesquioxane grafted CeO2. That is, the thermal stabilizer includes active spherical silica sol and kaolin-loaded Fe2O3 in a mass ratio of 3:2.

[0119] Comparative Example 9: A thermally stable silicone rubber, which differs from Example 1 in that the thermal stabilizer comprises active spherical silica sol, CeO2 and Fe2O3 in a mass ratio of 3:0.5:1.5.

[0120] Comparative Example 10: A thermally stable silicone rubber, which differs from Example 1 in that the toughening agent uses carboxylated PVDF nanofibers in an equal amount to replace the modified metal-organic framework material.

[0121] Performance testing

[0122] Silicone rubber materials were prepared according to the methods in the examples and comparative examples, and their performance was tested according to the following methods. The test results are recorded in Table 2.

[0123] 1. Tensile strength and elongation at break: Tested in accordance with GB / T528-2009 "Determination of tensile stress-strain properties of vulcanized rubber or thermoplastic rubber", with a tensile rate of 500 mm / min.

[0124] 2. Tear strength: Tested in accordance with GB / T529-2008 "Determination of tear strength of vulcanized rubber or thermoplastic rubber (trouser type, right angle and crescent type specimens)" at a rate of 500 mm / min.

[0125] 3. Thermal oxidation: The silicone rubber sample was placed in an electric heating drying oven and aged at 300℃ for 12 hours to obtain the sample after thermal oxidative aging. Its tensile strength was tested again, and the decrease rate (%) of tensile strength was calculated according to the following formula: (initial tensile strength - tensile strength after aging) / initial tensile strength × 100.

[0126] Table 2. Test results of thermally stable silicone rubber properties.

[0127]

[0128]

[0129] Based on the raw material ratios and selections in Examples 1-4, and the test data in Table 2, it can be seen that the silicone rubber materials prepared in Examples 1-4 have high initial tensile strength and elongation at break, high mechanical strength, and after being oxidized at 300℃ for 12 hours, the tensile strength reduction rate remains within 10%, indicating strong resistance to thermal oxidation and strong thermal stability.

[0130] Compared with Example 1, Example 5 shows that the amount of Fe2O3 loaded with kaolin is 4 times that of CeO2 grafted with cage-like oligomeric silsesquioxane. It can be seen that the initial tensile strength, elongation at break, and tear strength of the silicone rubber material prepared in Example 5 are slightly reduced, and the tensile strength decreases significantly after aging, exceeding 10%. This indicates that the anti-aging protective effect is stronger when the amount of Fe2O3 loaded with kaolin is 3 times that of CeO2 grafted with cage-like oligomeric silsesquioxane.

[0131] Compared with Example 1, Example 6 used carboxylated PVDF nanofibers prepared in Preparation Example 3, and compared with Preparation Example 1, used copper oxide to replace carbon nanotubes in equal amounts. As a result, the mechanical strength of the silicone rubber material prepared in Example 6 decreased, its anti-aging ability declined, and its thermal stability deteriorated.

[0132] In Example 7, the carboxylated PVDF nanofibers prepared in Preparation Example 4 were used. In Preparation Example 4, carbon nanotubes were used to replace copper oxide in equal amounts. It can be seen that its resistance to thermal aging decreased and its thermal stability deteriorated.

[0133] In Example 8, the carboxylated PVDF nanofibers prepared in Example 5 were used. No carbon nanotubes and copper oxide were added in Example 5. Compared with Example 1, the thermal aging ability of the silicone rubber prepared in Example 8 decreased significantly.

[0134] In Example 9, the cage-like oligomeric silsesquioxane prepared in Preparation Example 8 was grafted onto CeO2. Compared with Preparation Example 6 in Example 1, N,N-carbonyldiimidazole was not added. Therefore, the aminated cage-like oligomeric silsesquioxane could not be grafted onto the acidified CeO2, resulting in a decrease in its heat aging resistance and a weakening of its thermal stability.

[0135] In Example 10, the cage-shaped oligomeric silsesquioxane grafted CeO2 prepared in Preparation Example 9 was used. Compared with Preparation Example 6, CeO2 was not acidified. It can be seen that the mechanical strength and other properties of the silicone rubber material prepared by it are quite different from those of Example 1, but similar to those of the silicone rubber prepared in Example 9 without the addition of N,N-carbonyldiimidazole.

[0136] Compared with Example 1, Example 11 uses kaolin loaded with Fe2O3 prepared in Preparation Example 12. Compared with Preparation Example 10 in Example 1, Preparation Example 12 does not use silane coupling agent KH550 to pretreat the kaolin, while Example 12 uses kaolin loaded with Fe2O3 prepared in Preparation Example 13. The modified kaolin is not subjected to plasma fluorination treatment. Table 2 shows that the thermal aging resistance of the silicone rubber materials prepared in Examples 11 and 12 is significantly reduced.

[0137] In Comparative Examples 1 and 2, the amount of Fe2O3 loaded in kaolin was reduced and increased, respectively. The data in Table 2 shows that, compared with Examples 1 and 5, the mechanical strength of the silicone rubber materials prepared in Comparative Examples 1 and 2 decreased significantly, and the tensile strength decreased significantly after thermal aging.

[0138] Compared with Example 1, no toughening and reinforcing agent was added to Comparative Example 3. It can be seen that the tensile and tear strength of the silicone rubber material prepared in Comparative Example 3 decreased, and the tensile strength decreased significantly after thermal oxidation, and the thermal stability was weakened.

[0139] In Comparative Example 4, nano-alumina was used as a heat stabilizer. Compared with Example 1, the silicone rubber material prepared therefrom showed a significant decrease in its resistance to thermal oxidation, and the improvement effect on the initial tensile strength, elongation at break and tear strength of the silicone rubber was not good.

[0140] In Comparative Example 5, cerium oxide was used to replace the cage-like oligomeric silsesquioxane grafted CeO2, and in Comparative Example 6, Fe2O3 was used to replace kaolin-loaded Fe2O3. The initial tensile and tear resistance and the heat aging resistance of the silicone rubber materials prepared in Comparative Examples 5 and 6 were weakened.

[0141] Comparative Example 7 used active spherical silica sol and cage-shaped oligomeric silsesquioxane-grafted CeO2 in a mass ratio of 3:2 as heat stabilizers. Comparative Example 8 used active spherical silica sol and kaolin-supported Fe2O3 in a mass ratio of 3:2. As shown in Table 2, the silicone rubber prepared in Comparative Examples 7 and 8 showed a decrease in anti-aging ability, indicating that the combined effect of cage-shaped oligomeric silsesquioxane-grafted CeO2 and kaolin-supported Fe2O3 produced a compounding effect, which is beneficial to improving anti-aging performance. In Comparative Example 9, only active spherical silica sol, CeO2, and Fe2O3 were used as heat stabilizers, and its thermal stability decreased most significantly.

[0142] In Comparative Example 10, only carboxylated PVDF nanofibers were used as toughening and reinforcing agents. It can be seen that after thermal aging, the tensile strength and reduction rate of silicone rubber decreased significantly.

[0143] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A thermally stable silicone rubber, characterized in that, The raw materials include the following parts by weight: 100 parts silicone rubber matrix, 2-6 parts hydroxyl silicone oil, 1-2.5 parts vulcanizing agent, 20-50 parts silica, 1-5 parts coupling agent, 5-10 parts heat stabilizer, 10-40 parts flame retardant, and 4-10 parts toughening and reinforcing agent. The silicone rubber matrix comprises methyl vinyl silicone rubber and fluorosilicone rubber in a mass ratio of 6-7:2.5-3; The heat stabilizer comprises active spherical silica sol, cage-shaped oligomeric silsesquioxane grafted CeO2, and kaolin-supported Fe2O3 in a mass ratio of 3:0.5-0.7:1.5-2.

1. The toughening and reinforcing agent comprises carboxylated PVDF nanofibers and modified metal-organic framework materials in a mass ratio of 1:0.1-0.3; The method for preparing the carboxylated PVDF nanofibers includes the following steps: PVDF and ethylene maleic anhydride copolymer were mixed and added to a solvent prepared by mixing DMA and acetone in a volume ratio of 3:

2. Copper oxide was added, the mixture was heated to 50-60℃, and stirred for 10-12 hours to obtain a spinning solution. The amounts of copper oxide and ethylene maleic anhydride copolymer were 5-9 wt% and 15-20 wt% of the mass of PVDF, respectively. The spinning solution was electrospun to obtain a nanofiber membrane, which was then vacuum dried at 50-60℃, impregnated in sulfuric acid solution, washed, and vacuum dried to obtain carboxylated PVDF nanofibers. The method for preparing the cage-shaped oligomeric silsesquioxane grafted with CeO2 is as follows: CeO2 was added to an acetic acid solution, stirred at 50-70℃ for 3-4 hours, filtered, and dried to obtain acidified CeO2. Add acidified CeO2 to tetrahydrofuran, add N,N-carbonyldiimidazole, heat to 60-70℃, stir for 3-5h, then add aminated cage-like oligomeric silsesquioxane, purge with nitrogen, and react at 60-70℃ for 10-12h, filter, and vacuum dry at 60-70℃. The kaolin loaded with Fe2O3 was prepared by the following method: Kaolin was added to anhydrous ethanol and stirred evenly. Then, silane coupling agent KH560 was added and stirred for 40-60 minutes. After drying, modified kaolin was obtained. The mass ratio of silane coupling agent to kaolin was 8-10:

1. CF4 and N2 in a volume ratio of 25:1 were used as a mixed gas to fluorinate kaolin for 15-20 minutes to obtain fluorinated kaolin. Fluorinated kaolin is impregnated in a 10% ferric nitrate solution, allowed to stand for 10-12 hours, then heated to 60-65℃, allowed to stand for 5-6 hours, and the pH is adjusted until precipitation occurs. The precipitate is then filtered, washed until neutral, dried, and heated to 400-450℃ under nitrogen protection, and held at that temperature for 1-1.5 hours.

2. The thermally stable silicone rubber according to claim 1, characterized in that: The spinning solution also contains carbon nanotubes, and the ratio of carbon nanotubes to PVDF is 0.01-0.1:

1.

3. The thermally stable silicone rubber according to claim 1, characterized in that: The specific method for plasma fluorination treatment is as follows: modified kaolin is loaded into a reactor, and a vacuum is drawn to 2.8 × 10⁻⁶. -3 Pa, then a mixture of CF4 and N2 was introduced to raise the internal pressure to 10 kPa, and then a vacuum was evacuated again to 2.8 × 10 Pa. -3 Pa, and finally a mixture of CF4 and N2 is introduced until the internal pressure stabilizes at 13.5 kPa, with a voltage of 24 kV and a frequency of 9 kHz applied.

4. The thermally stable silicone rubber according to claim 1, characterized in that: The vulcanizing agent is any one of 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane and 2,4-dichlorobenzoyl peroxide; The flame retardant is selected from at least one of ammonium polyphosphate, magnesium hydroxide, and aluminum hydroxide; The coupling agent is selected from at least one of A151 coupling agent, A171 coupling agent, KH550 coupling agent, and KH560 coupling agent.

5. A method for preparing the thermally stable silicone rubber according to any one of claims 1-4, characterized in that: Includes the following steps: The silicone rubber matrix, silica and hydroxyl silicone oil are mixed at 80-100℃ for 20-30 minutes. Coupling agent, toughening and reinforcing agent, heat stabilizer and flame retardant are added and mixed at 80-100℃ for 1-1.5 hours. Then vacuum is applied for 30-40 minutes with a vacuum degree of -0.07MPa to obtain the rubber compound. Mix the rubber compound with the vulcanizing agent and knead at 120-130℃ for 1-2 hours. Then, pass the mixture through a thin sheet to form a compounded rubber. The compound is vulcanized at 160-170℃ and 25-30MPa for 10-20 minutes, then vulcanized at 180-190℃ for 2-4 hours, and cooled to room temperature to produce a thermally stable silicone rubber.

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