High-temperature-resistant silicone rubber and preparation method thereof

Abstract

The invention discloses high-temperature-resistant silicone rubber and a preparation method thereof, and belongs to the field of polymer compositions. The silicone rubber is composed of vinyl-terminated polydimethylsiloxane, fumed silica, hydroxyl silicone oil, a hydrogen-containing silicone oil cross-linking agent, a platinum catalyst, an inhibitor methyl butynol, cerium oxide and zinc oxide whiskers. During preparation, vinyl siloxane and 1 / 2 of white carbon black are subjected to vacuum banburying for 40 min at the temperature of 155 DEG C, the remaining white carbon black and hydroxyl silicone oil are added to be mixed for 50 min at the temperature of 125 DEG C, other components are sequentially added after cooling, and vulcanization is conducted at the temperature of 170 DEG C * 15 MPa. The shore A hardness of the obtained silicone rubber is greater than or equal to 63, the retention rate of elongation at break is greater than or equal to 485%, the retention rate of tensile strength after aging at 350 DEG C for 72 hours is greater than or equal to 86%, the thermal weight loss is 5%, the temperature is greater than or equal to 476 DEG C, the Mooney viscosity is less than or equal to 47, and the silicone rubber has excellent processability and high-temperature stability.

Description

Technical Field

[0001] This invention belongs to the field of polymer compositions, and particularly relates to a high-temperature resistant silicone rubber and its preparation method. Background Technology

[0002] Silicone rubber, as a high-performance elastomer, is widely used in sealing, insulation and other fields. However, its main chain structure is prone to depolymerization and side group oxidation above 250℃, leading to a sharp decline in mechanical properties. Traditional improvement methods mainly enhance heat resistance by adding metal oxides or introducing phenylsilane monomers. However, the former reduces the material's elasticity (elongation at break decreases by >35%), while the latter significantly increases raw material costs (increases by 40-50%) and reduces processing fluidity (Mounney viscosity increases by >55%).

[0003] Current technologies generally use bisphenol antioxidants or staged mixing to improve performance, but there are still bottlenecks: silica is prone to agglomeration in the polymer matrix, resulting in uneven cross-linking network, and the tensile strength decreases by more than 45% after aging at 350℃ for 48 hours; high-temperature deactivation of platinum catalyst reduces vulcanization efficiency, and excessive addition can lead to scorching risk; the traditional open milling process has a mixing cycle of more than 120 minutes, high energy consumption and poor batch stability (tensile strength deviation ±1.8MPa).

[0004] To address the aforementioned issues, this patent designs a novel inorganic / organic synergistic heat-resistant system and combines it with a step-by-step mixing process to regulate filler dispersion and cross-linking networks at the molecular level, achieving simultaneous breakthroughs in heat resistance, processability, and mechanical properties. Summary of the Invention

[0005] To solve the problem of achieving high heat resistance, processability, and balanced mechanical properties.

[0006] To address the above problems, the present invention provides the following technical solution: A high-temperature resistant silicone rubber, characterized in that, by weight, it comprises: 100 parts vinyl-terminated polydimethylsiloxane, 40-60 parts fumed silica, 8-12 parts hydroxyl silicone oil, 1.5-2.5 parts hydrogen-containing silicone oil crosslinking agent, 0.05-0.15 parts platinum catalyst, 0.01-0.03 parts inhibitor, 5-8 parts cerium oxide, and 3-5 parts zinc oxide whiskers.

[0007] Preferably, the specific surface area of ​​the fumed silica is 290-310 m². 2 / g, and then vacuum dried at 110-130℃ for 4h.

[0008] Preferably, the zinc oxide whiskers have an aspect ratio of 15-20:1 and their surface is modified with silane coupling agent KH-550.

[0009] Preferably, the inhibitor is a mixture of methylbutynol and etynylcyclohexanol in a ratio of 1:(0.5-1). A method for preparing high-temperature resistant silicone rubber, characterized by comprising the following steps: S1: Vinylsiloxane and 40-50% silica are mixed in an intensive kneading process at 155±2℃ and a vacuum of -0.09MPa for 40 minutes; S2: Add the remaining silica and hydroxyl silicone oil, and mix at 125±3℃ for 50 minutes; S3: After cooling to 85±2℃, add hydrogen-containing silicone oil and mix for 15 minutes; S4: Add cerium oxide and zinc oxide whiskers sequentially and mix for 20 minutes; S5: Add platinum catalyst and inhibitor, and mix under nitrogen protection for 10 minutes; S6: 170±2℃×15MPa compression vulcanization for 15min.

[0010] Preferably, the internal mixer speed in S1 is 40-50 rpm.

[0011] Preferably, the mixing vacuum degree in S2 is maintained at -0.07MPa.

[0012] Preferably, ultrasonic treatment (power 800W, frequency 28kHz) is applied during the mixing process in S4.

[0013] Preferably, the silicone rubber has a 5% thermal weight loss temperature ≥ 476℃.

[0014] Preferably, the change in Shore A hardness of the silicone rubber after aging at 350℃ for 72 hours is ≤4 degrees.

[0015] The effects and advantages of the high-temperature resistant silicone rubber and its preparation method of the present invention are as follows: 1. This patent improves high-temperature aging resistance. Cerium oxide and zinc oxide whiskers synergistically capture free radicals, and the tensile retention rate is 91.4% after 350℃×72h.

[0016] 2. This patent optimizes crosslinking efficiency, delaying the charring time to 52 min in the platinum catalyst / inhibitor composite system, achieving a crosslinking density of 5.2 × 10⁻⁶. -5 mol / cm 3 .

[0017] 3. This patented technology enhances processing fluidity and reduces Mooney viscosity to 43, which is lower than that of traditional processes, due to the segmented addition of hydroxyl silicone oil to suppress the agglomeration of silica.

[0018] 4. This patent has a tensile strength of 10.8 MPa and an elongation at break of 528% when it is not aged. Whisker reinforcement improves tear strength. Attached Figure Description

[0019] Figure 1 This is a flowchart of a high-temperature resistant silicone rubber and its preparation method according to the present invention. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0021] Example 1 refer to Figure 1 This embodiment provides a high-temperature resistant silicone rubber and its preparation method, applicable to the field of polymer compositions, including the following implementation details: Experimental objective: A high-temperature resistant silicone rubber and its preparation method are disclosed. The compatibility of the lower limit of the component ratio (40 parts of silica, 5 parts of cerium oxide, 3 parts of zinc oxide whiskers, etc.) with the stepped mixing process is verified, and the processing performance, mechanical strength and heat resistance of the basic formulation are examined to see if they meet the lower limit requirements of the claims.

[0022] Experimental materials: Matrix polymer: Vinyl-terminated polydimethylsiloxane (vinyl content 0.16%, viscosity 12,000 mPa·s) 100 parts; Reinforcing filler: Fumed silica (specific surface area 300 m² / s) 2 / g, loss on ignition ≤1.5%) 40 parts; Processing aid: hydroxyl silicone oil (hydroxyl content 8.0 wt%, viscosity 100 mPa·s) 8 parts; Crosslinking agent: hydrogen-containing silicone oil (hydrogen content 0.90 wt%, Si-H bond number / molecule = 8) 1.5 parts; Catalyst: chloroplatinic acid-isopropanol solution (platinum content 3000 ppm) 0.05 parts; Inhibitor: methylbutynol (purity ≥99%) 0.01 parts; Heat resistant agent: cerium oxide (average particle size 50 nm, specific surface area 85 m²) 2 5 parts of zinc oxide whiskers (length-to-diameter ratio 18:1, surface modified with KH-550) and 3 parts of zinc oxide whiskers (length-to-diameter ratio 18:1, surface modified with KH-550).

[0023] Experimental equipment: Internal mixer, flat vulcanizing machine, thermogravimetric analyzer, electronic tensile testing machine, Mooney viscometer.

[0024] Experimental steps: S1: Preliminary mixing: 100 parts of vinylsiloxane and 20 parts of silica are put into the mixing chamber, and the temperature is set to 155±2℃, the vacuum degree to -0.09 MPa, and the rotor speed to 45 rpm. The mixture is then discharged after 40 minutes of mixing. S2: Dispersion enhancement, add the remaining 20 parts of silica and 8 parts of hydroxyl silicone oil, and mix at 125±3℃ and vacuum degree -0.07 MPa for 50 min; S3: Introduce crosslinking agent, cool to 85±2℃, add 1.5 parts of hydrogen-containing silicone oil, and mix for 15 min (reducing the speed to 30 rpm). S4: Heat resistant agent dispersion, add 5 parts cerium oxide + 3 parts zinc oxide whiskers, turn on ultrasonic assistance (power 800 W, frequency 28 kHz), mix for 20 min; S5: Catalytic sulfidation system, add 0.05 parts of chloroplatinic acid-isopropanol solution and 0.01 parts of methylbutynol, mix for 10 min under nitrogen protection (N2 flow rate 5 L / min). S6: Vulcanization molding, the mixed rubber is placed into the mold, vulcanized on a flat plate at 170±1℃×15 MPa for 15 min, and the sample is taken out after holding the pressure and cooling to room temperature.

[0025] Experimental results: See Table 1 for details.

[0026] Table 1: Test Results of Example 1

[0027] Example 1: A high-temperature resistant silicone rubber and its preparation method. The Shore A hardness of 63 is attributed to the dual reinforcing effect of silica and zinc oxide whiskers: fumed silica is effectively dispersed during intensive mixing at 155℃, and its silanol groups form physical crosslinking points with the matrix; modified zinc oxide whiskers, as a rigid reinforcing phase, chemically bond with the matrix through surface KH-550 silane, and stress concentration at the whisker ends increases the macroscopic hardness. The balance between tensile strength of 9.1 MPa and elongation at break of 485% is due to the optimization of the stepped mixing process: hydroxyl silicone oil is added in the mid-temperature range of 125℃, increasing the silanol end-capping rate on the silica surface and reducing stress concentration caused by filler agglomeration; while hydrogen-containing silicone oil is introduced in the low-temperature range, forming a Si-H / Vi crosslinking network (crosslinking density 4.2 × 10⁻⁶). -5 mol / cm 3 This ensures the ductility of the molecular chains. The breakthrough of achieving 5% thermal weight loss at 476℃ is attributed to the catalytic synergistic mechanism of cerium oxide: Ce in nano-CeO2... 3+ / Ce 4+ The redox pair efficiently quenches silicon-oxygen free radicals and simultaneously forms a Zn2CeO4 heterojunction with zinc oxide whiskers at the interface, increasing the activation energy for thermal decomposition. The excellent processing fluidity of Mooney viscosity 47 stems from the synergistic effect of matrix plasticization and dispersion: low molecular weight hydroxyl silicone oil acts as a lubricating phase, reducing the aggregate volume fraction of silica and lowering shear viscosity. The stability of 86.2% tensile strength retention after aging at 350℃ for 72h is primarily driven by the heat-resistant system: CeO2 continuously captures free radicals, resulting in a low main chain breakage rate, while ZnO whiskers inhibit side group oxidation. The +4 degree increase in hardness reflects the dynamic evolution of the crosslinking network: at high temperatures, the remaining Si-H bonds continue to crosslink, increasing the crosslinking point density, but oxidation chain breakage and filler rearrangement together lead to an increase in elastic modulus.

[0028] Example 2 This embodiment provides a high-temperature resistant silicone rubber and its preparation method, optimizing the upper limit of components, including the following implementation details: Experimental objective: A high-temperature resistant silicone rubber and its preparation method are disclosed. The feasibility of the process with the upper limit of the component ratio (60 parts of silica, 8 parts of cerium oxide, 5 parts of zinc oxide whiskers, etc.) is verified, and the dispersion uniformity, crosslinking efficiency and high-temperature stability under the high filler system are investigated.

[0029] Experimental materials: Matrix polymer: Vinyl-terminated polydimethylsiloxane (vinyl content 0.16%, viscosity 12,000 mPa·s) 100 parts; Reinforcing filler: Fumed silica (specific surface area 300 m² / s) 2 / g, loss on ignition ≤1.5%) 60 parts; Processing aid: hydroxyl silicone oil (hydroxyl content 8.0 wt%, viscosity 100 mPa·s) 12 parts; Crosslinking agent: hydrogen-containing silicone oil (hydrogen content 0.90 wt%, Si-H bond number / molecule = 8) 1.5 parts; Catalyst: chloroplatinic acid-isopropanol solution (platinum content 3000 ppm) 0.05 parts; Inhibitor: methylbutynol:tetramethyltetravinylcyclotetrasiloxane = 1:0.6 0.01 parts; Heat resistant agent: cerium oxide (average particle size 50 nm, specific surface area 85 m²) 2 / g) 8 parts; reinforcing agent: zinc oxide whiskers (length-to-diameter ratio 18:1, surface modified with KH-550) 5 parts.

[0030] Experimental steps: S1: Preliminary mixing: 100 parts of vinylsiloxane and 30 parts of silica are put into the mixing chamber, and the temperature is set to 155±2℃, the vacuum degree to -0.09 MPa, and the rotor speed to 45 rpm. The mixture is then discharged after 40 minutes of mixing. S2: Dispersion enhancement, add the remaining 30 parts of silica and 12 parts of hydroxyl silicone oil, and mix for 50 min at 125±3℃ and vacuum degree -0.07 MPa; S3: Introduce crosslinking agent, cool to 85±2℃, add 1.5 parts of hydrogen-containing silicone oil, and mix for 15 minutes (reducing the speed to 30 rpm). S4: Disperse the heat resistant agent by adding 8 parts cerium oxide + 5 parts zinc oxide whiskers, turn on the ultrasonic (800W, 28kHz), and mix for 20 minutes. S5: Catalytic sulfidation system, add 0.05 parts of chloroplatinic acid-isopropanol solution and 0.01 parts of compound inhibitor, mix for 10 min under nitrogen protection (N2 flow rate 5 L / min). S6: Vulcanization molding, the mixed rubber is placed into the mold, vulcanized on a flat plate at 170±1℃×15 MPa for 15 min, and the sample is taken out after holding the pressure and cooling to room temperature.

[0031] Experimental results: See Table 2 for details.

[0032] Table 2: Test Results of Example 2

[0033] Example 2: A high-temperature resistant silicone rubber and its preparation method. The hardness is 68. Due to the high filler volume fraction (60 parts silica + 5 parts whiskers), a strong filling effect is generated. The whiskers are oriented along the stress direction, forming a "skeleton-fine particle" bilevel structure with the silica, thus increasing the elastic modulus. The tensile strength of 11.3 MPa originates from a triple reinforcement mechanism: ① High crosslinking density (4.9 × 10⁻⁶). -5 mol / cm 3The following factors contributed to the improvement: ① Increased hydrogen-containing silicone oil reacted fully with the platinum catalyst; ② The aspect ratio of zinc oxide whiskers increased to 20:1, bridging silica aggregates and inhibiting crack propagation; ③ Ultrasonic waves reduced cerium oxide dispersion to nanoscale size. Elongation at break was 528% due to the increased hydroxyl silicone oil plasticizing the matrix and ensuring molecular chain slippage. The 5% thermal weight loss at 482℃ was due to the optimized cerium oxide / whisker molar ratio of 1:0.35, with the heterogeneous interface raising the thermal desorption barrier. Mooney viscosity decreased to 43, attributed to: ① Increased lubricity of hydroxyl silicone oil; ② Ultrasonic waves breaking up secondary silica aggregates. Tensile retention after aging was 89.7% due to the high CeO2 content forming a continuous passivation layer on the whisker surface, blocking oxygen diffusion pathways; the compounded inhibitor retained 87% of the residual platinum catalytic activity, continuously repairing broken chains. Hardness (+3ΔA) showed little change due to the high uniformity of the cross-linked network, inhibiting high-temperature rearrangement.

[0034] Example 3 This embodiment provides a high-temperature resistant silicone rubber and its preparation method, which optimizes the catalyst system and high-temperature mixing, including the following implementation details: Experimental objective: A high-temperature resistant silicone rubber and its preparation method are disclosed. The synergistic effect of increasing the amount of platinum catalyst (0.12 parts) and increasing the mixing temperature (160℃) on crosslinking efficiency and heat resistance is verified.

[0035] Experimental materials: Matrix polymer: Vinyl-terminated polydimethylsiloxane (vinyl content 0.16%, viscosity 12,000 mPa·s) 100 parts; Reinforcing filler: Fumed silica (specific surface area 300 m² / s) 2 / g, loss on ignition ≤1.5%) 60 parts; Processing aid: hydroxyl silicone oil (hydroxyl content 8.0 wt%, viscosity 100 mPa·s) 12 parts; Crosslinking agent: hydrogen-containing silicone oil (hydrogen content 1.2 wt%, Si-H bond number / molecule = 8) 1.5 parts; Catalyst: chloroplatinic acid-isopropanol solution (platinum content 3000 ppm) 0.12 parts; Inhibitor: methylbutynol:tetramethyltetravinylcyclotetrasiloxane = 1:0.6 0.01 parts; Heat resistant agent: cerium oxide (average particle size 50 nm, specific surface area 85 m²) 2 / g) 8 parts; reinforcing agent: zinc oxide whiskers (length-to-diameter ratio 18:1, surface modified with KH-550) 5 parts.

[0036] Experimental steps: S1: Preliminary mixing: 100 parts of vinylsiloxane and 30 parts of silica are put into the mixing chamber, and the temperature is set to 160±2℃, the vacuum degree to -0.09 MPa, and the rotor speed to 45 rpm. The mixture is then discharged after 40 minutes of mixing. S2: Dispersion enhancement, add the remaining 30 parts of silica and 12 parts of hydroxyl silicone oil, and mix for 50 min at 125±3℃ and vacuum degree -0.07 MPa; S3: Introduce crosslinking agent, cool to 85±2℃, add 1.5 parts of hydrogen-containing silicone oil, and mix for 15 minutes (reducing the speed to 30 rpm). S4: Disperse the heat resistant agent by adding 8 parts of cerium oxide and 5 parts of zinc oxide whiskers, turn on the ultrasonic wave (800W, 28kHz), and mix for 20 minutes. S5: Catalytic sulfidation system, add 0.12 parts of chloroplatinic acid-isopropanol solution and 0.01 parts of compound inhibitor, mix for 10 min under nitrogen protection (N2 flow rate 5 L / min). S6: Vulcanization molding, the mixed rubber is placed into the mold, vulcanized on a flat plate at 170±1℃×15 MPa for 15 min, and the sample is taken out after holding the pressure and cooling to room temperature.

[0037] Experimental results: See Table 3 for details.

[0038] Table 3: Test Results of Example 3

[0039] Example 3: A high-temperature resistant silicone rubber and its preparation method. The increase in hardness (71) is attributed to the synergistic effect of silica surface activation and high crosslinking density: intensive mixing at 160℃ promotes the dehydroxylation of silanol groups on the silica surface, increasing the hydrogen bond density with the matrix, while the crosslinking density reaches 5.2 × 10⁻⁶. -5 mol / cm 3Further restriction of molecular chain movement. The tensile strength of 10.8 MPa is slightly lower than that of Example 2 (11.3 MPa). This is because the increased platinum catalyst caused excessively rapid local crosslinking, leading to a decrease in the uniformity of the microstructure network. However, the high-temperature mixing significantly optimized the dispersion of silica, partially offsetting the effect of the defects. The balanced elongation at break of 503% is attributed to the inhibitor compound system (tetramethyltetravinylcyclotetrasiloxane accounting for 50%), which delayed the scorch time to 52 min (Mounney test), ensuring sufficient extension of the molecular chains. The 5% thermal weight loss temperature of 478°C exhibits a contradictory effect of the heat-resistant components: the increased mixing temperature promotes the formation of more heterogeneous interfaces between ZnO whiskers and CeO2, raising the thermal desorption barrier; however, the excessively strong platinum catalytic activity leads to partial pre-crosslinking of the silicon-oxygen backbone. The two offset each other, resulting in a slight decrease in the 5% thermal weight loss temperature compared to Example 2. The 91.4% tensile strength retention after aging is attributed to a triple mechanism: ① High-temperature intensive mixing activates the hydroxyl groups on the surface of silica, forming Si-O-Ce bonds with cerium oxide, stabilizing the filler / matrix interface; ② High-content platinum catalytic residual activity continuously repairs broken chains; ③ The KH-570 whisker-modified layer contains double bonds, participating in cross-linking to form an interpenetrating network. The hardness change of only +2ΔA demonstrates improved network thermal stability: reduced defect density hinders high-temperature rearrangement, and chemical bonding at the whisker / matrix interface inhibits filler migration. The maintenance of Mooney viscosity of 46 reflects the effectiveness of process control: gradient mixing achieves torque balance, avoiding localized overheating and gelation.

[0040] Comparative Example 1 A conventional high-temperature resistant silicone rubber and its preparation method are provided, compared with conventional iron-based heat resistant agents, including the following implementation details: Experimental objective: A conventional high-temperature resistant silicone rubber and its preparation method are presented. The performance advantages of the cerium oxide / zinc oxide whisker system over the conventional ferric oxide heat resistant agent are verified, and the decisive influence of the selection of inorganic heat resistant agent on high-temperature stability and mechanical properties is clarified.

[0041] Experimental materials: Matrix polymer: Vinyl-terminated polydimethylsiloxane (vinyl content 0.16%, viscosity 12,000 mPa·s) 100 parts; Reinforcing filler: Fumed silica (specific surface area 300 m² / s) 2 / g, loss on ignition ≤1.5%) 40 parts; Processing aid: hydroxyl silicone oil (hydroxyl content 8.0 wt%, viscosity 100 mPa·s) 8 parts; Crosslinking agent: hydrogen-containing silicone oil (hydrogen content 0.90wt%, Si-H bond number / molecule = 8) 1.5 parts; Catalyst: chloroplatinic acid-isopropanol solution (platinum content 3000 ppm) 0.05 parts; Inhibitor: methylbutynol (purity ≥99%) 0.01 parts; Heat resistant agent: ferric oxide (α-Fe2O3, average particle size 1.2 μm, purity ≥99%) 8 parts (replacing cerium oxide + whiskers in Example 1).

[0042] Experimental steps: S1: Preliminary mixing: 100 parts of vinylsiloxane and 20 parts of silica are put into the mixing chamber, and the temperature is set to 155±2℃, the vacuum degree to -0.09 MPa, and the rotor speed to 45 rpm. The mixture is then discharged after 40 minutes of mixing. S2: Dispersion enhancement, add the remaining 20 parts of silica and 8 parts of hydroxyl silicone oil, and mix at 125±3℃ and vacuum degree -0.07 MPa for 50 min; S3: Introduce crosslinking agent, cool to 85±2℃, add 1.5 parts of hydrogen-containing silicone oil, and mix for 15 min (reducing the speed to 30 rpm). S4: Disperse the heat resistant agent, add 8 parts of Fe2O3 (without ultrasonic assistance), and mix for 20 min; S5: Catalytic sulfidation system, add 0.05 parts of chloroplatinic acid-isopropanol solution and 0.01 parts of methylbutynol, mix for 10 min under nitrogen protection (N2 flow rate 5 L / min). S6: Vulcanization molding, the mixed rubber is placed into the mold, vulcanized on a flat plate at 170±1℃×15 MPa for 15 min, and the sample is taken out after holding the pressure and cooling to room temperature.

[0043] Experimental results: See Table 4 for details.

[0044] Table 4: Test Results of Comparative Example 1

[0045] Comparative Example 1 provides a traditional high-temperature resistant silicone rubber and its preparation method. The hardness of 59 is attributed to the weak interfacial interaction between Fe2O3 and the silicon matrix: the ferric oxide surface lacks active groups, making it unable to form an effective bond with silica or the matrix, resulting in low filler reinforcement efficiency. The tensile strength of 7.6 MPa is attributed to: ① Fe2O3 acting as a Lewis acid catalyzing the cracking of the silicon-oxygen backbone; ② Iron ions resulting in a crosslinking density of only 3.7 × 10⁻⁶. -5 mol / cm 3 The molecular network's load-bearing capacity weakens. The sharp drop in elongation at break (398%) is due to stress concentration caused by rigid Fe2O3 particles during stretching. The 5% thermal weight loss and the steep temperature drop of 453℃ reveal defects in the Fe2O3 heat resistance mechanism: low α-Fe2O3 free radical capture efficiency, and crystal transformation occurring above 400℃, exacerbating volume shrinkage and microcracks in the matrix. The 61.5% tensile retention after aging is mainly due to the iron ion-catalyzed oxidation chain reaction: Fe 3+ / Fe 2+ Redox cycles accelerate the oxidation of side-chain methyl groups, generating volatile low-molecular-weight cyclic compounds, while reversion to sulfur causes the cross-linked network to disintegrate. Hardness increases by 12ΔA. Thermo-oxidative aging leads to molecular chain breakage, accompanied by Fe2O3 aggregation, and the increased proportion of rigid particles completely destroys the elastic recovery capability.

[0046] Example 1 provides a high-temperature resistant silicone rubber and its preparation method. Excellent comprehensive performance is achieved through a stepped mixing process and the synergistic effect of a specific component ratio (40 parts silica, 5 parts cerium oxide, and 3 parts zinc oxide whiskers). The Shore A hardness of 63 originates from the dual reinforcing effect of silica and zinc oxide whiskers: silica forms physical crosslinking points during intensive mixing at 155℃, while zinc oxide whiskers enhance rigidity by chemically bonding the matrix through surface modification. The balance between tensile strength of 9.1 MPa and elongation at break of 485% is attributed to the optimized filler dispersion with hydroxyl silicone oil and the crosslinking network formed by the low-temperature introduction of hydrogen-containing silicone oil (crosslinking density 4.2 × 10⁻⁶). -5 mol / cm 3 The breakthrough in thermal weight loss of 5% at 476℃ is attributed to the quenching of free radicals by cerium oxide and the formation of Zn₂CeO₄ heterojunctions with whiskers, which increases the activation energy for thermal decomposition. The Mooney viscosity of 47 reflects excellent processing fluidity, while the tensile retention of 86.2% and the change in hardness +4ΔA after aging at 350℃ for 72 hours indicate that the heat-resistant system effectively inhibits high-temperature degradation, although residual cross-linking reactions lead to a slight increase in modulus. Example 2 verified the feasibility of a high filler ratio (60 parts silica, 8 parts cerium oxide, and 5 parts zinc oxide whiskers), with further performance optimization. The Shore A hardness of 68 was achieved through a two-level filler "skeleton-fine particle" structure, and the tensile strength of 11.3 MPa stemmed from the high crosslinking density (4.9 × 10⁻⁶). -5 mol / cm 3 The system utilizes nanoscale cerium oxide with whisker bridging effect and ultrasonic dispersion. The 528% elongation at break is attributed to the hydroxyl silicone oil-added plasticizing of the matrix, while the 5% thermal weight loss at 482℃ is due to the optimized cerium oxide / whisker molar ratio. The Mooney viscosity of 43 reflects improved processability, and the 89.7% tensile strength retention after aging is attributed to the CeO2 passivation layer blocking oxygen diffusion and the combined inhibitor retaining platinum catalytic activity. The hardness change of only +3ΔA indicates that network uniformity in the high-filler system inhibits high-temperature rearrangement. Example 3 enhanced crosslinking efficiency and heat resistance through the synergistic effect of increasing the platinum catalyst volume (0.12 parts) and raising the mixing temperature (160°C). The Shore A hardness of 71 was achieved due to the surface activation of the silica and the high crosslinking density (5.2 × 10⁻⁶). -5 mol / cm 3 The synergistic effect resulted in a slight decrease in tensile strength to 10.8 MPa due to excessively rapid local cross-linking, but the optimized filler dispersion during high-temperature mixing partially offset this defect. The elongation at break of 503% was ensured by the delayed scorch time thanks to the compounded inhibitor. The 5% thermal weight loss at 478℃ reflects the contradictory effect of the heat-resistant components. The 91.4% tensile retention after aging is attributed to the stabilization of the Si-O-Ce bonds at the interface, platinum-catalyzed repair, and the participation of whiskers in the interpenetrating network. The +2ΔA change in hardness demonstrates a significant improvement in the network's thermal stability. Comparative Example 1 used a traditional Fe2O3 heat resistant agent, resulting in a comprehensive reduction in performance. The Shore A hardness was 59 due to the weak interfacial interaction between Fe2O3 and the matrix, and the tensile strength was 7.6 MPa, influenced by iron ion-catalyzed main chain cleavage and low crosslinking density (3.7 × 10⁻⁶). -5 mol / cm 3 The 398% drop in elongation at break is due to stress concentration in rigid particles, and the 5% thermal weight loss at 453℃ reveals the heat resistance defects of Fe2O3. The 61.5% tensile retention after aging is due to the iron ion-catalyzed oxidation chain reaction; the +12ΔA change in hardness reflects network disintegration and filler aggregation, resulting in a complete loss of elastic recovery ability.

[0047] Those skilled in the art will recognize that the modules and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0048] In addition, the functional modules in the various embodiments of this application can be integrated into one processing module, or each module can exist physically separately, or two or more modules can be integrated into one module.

[0049] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of protection of the claims.

[0050] In conclusion, the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included in the protection of the present invention.

Claims

1. A high-temperature resistant silicone rubber, characterized in that... The product comprises, by weight, 100 parts vinyl-terminated polydimethylsiloxane, 40-60 parts fumed silica, 8-12 parts hydroxyl silicone oil, 1.5-2.5 parts hydrogen-containing silicone oil crosslinking agent, 0.05-0.15 parts platinum catalyst, 0.01-0.03 parts inhibitor, 5-8 parts cerium oxide, and 3-5 parts zinc oxide whiskers.

2. The high-temperature resistant silicone rubber as described in claim 1, characterized in that, The specific surface area of ​​the fumed silica is 290-310 m². 2 / g, and then vacuum dried at 110-130℃ for 4h.

3. The high-temperature resistant silicone rubber as described in claim 1, characterized in that, The zinc oxide whiskers have an aspect ratio of 15-20:1 and their surface is modified with silane coupling agent KH-550.

4. The high-temperature resistant silicone rubber as described in claim 1, characterized in that, The inhibitor is a mixture of methylbutynol and etynylcyclohexanol in a ratio of 1:(0.5-1).

5. A method for preparing high-temperature resistant silicone rubber, characterized in that, Includes the following steps: S1: Vinylsiloxane and 40-50% silica are mixed in an intensive kneading process at 155±2℃ and a vacuum of -0.09MPa for 40 minutes; S2: Add the remaining silica and hydroxyl silicone oil, and mix at 125±3℃ for 50 minutes; S3: After cooling to 85±2℃, add hydrogen-containing silicone oil and mix for 15 minutes; S4: Add cerium oxide and zinc oxide whiskers sequentially and mix for 20 minutes; S5: Add catalyst and inhibitor, and mix under nitrogen protection for 10 minutes; S6: 170±2℃×15MPa compression vulcanization for 15min.

6. The method for preparing a high-temperature resistant silicone rubber as described in claim 5, characterized in that, The internal mixer in S1 operates at a speed of 40-50 rpm.

7. The method for preparing a high-temperature resistant silicone rubber as described in claim 5, characterized in that, The vacuum level during mixing in S2 is maintained at -0.07 MPa.

8. The method for preparing a high-temperature resistant silicone rubber as described in claim 5, characterized in that, In step S4, ultrasonic treatment (power 800W, frequency 28kHz) is applied during the mixing process.

9. The method for preparing a high-temperature resistant silicone rubber as described in claim 1, characterized in that, The silicone rubber exhibits a 5% thermal weight loss at a temperature ≥476℃.

10. The high-temperature resistant silicone rubber as described in claim 1, characterized in that, The silicone rubber undergoes a Shore A hardness change of ≤4 degrees after aging at 350℃ for 72 hours.

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