High-temperature-resistant mixed silicone rubber and preparation method thereof

Abstract

The invention relates to the technical field of rubber materials, in particular to high-temperature-resistant mixed silicone rubber and a preparation method thereof.The high-temperature-resistant mixed silicone rubber is prepared by taking methyl vinyl silicone rubber and methyl phenyl vinyl silicone rubber as a composite raw rubber system and matching with fumed silica reinforcing filler, a composite heat-resistant agent, a low-compression-deformation additive and a structural control agent; the rubber is prepared through the processes of rubber master batch preparation, secondary cold smelting and two-stage vulcanization. The product provided by the invention has excellent high-temperature aging resistance, low compression set rate, dimensional stability at extreme temperature of-180 DEG C to 280 DEG C, excellent mechanical properties (the non-aging tensile strength is greater than or equal to 1.5 MPa, and the elongation at break is greater than or equal to 150%), and the service life of the product is prolonged. The high-temperature-resistant and low-compression-deformation tire can be widely applied to automobile sealing parts, special tires (such as lunar vehicle tires) and other scenes with high requirements for high temperature resistance and low compression deformation.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of rubber materials, and particularly relates to a high-temperature-resistant mixing silicone rubber and a preparation method thereof. BACKGROUND

[0002] Silicone rubber is widely used in the fields of automobile, electronics, aerospace, etc. due to its elasticity of organic polymer and high-temperature resistance of inorganic polymer. However, the existing silicone rubber material still has the following technical problems, which are difficult to meet the needs of high-end scenes: insufficient high-temperature aging performance: the long-term use temperature of ordinary methyl vinyl silicone rubber is usually lower than 200 DEG C, and the main chain is easily cracked and the side group is easily oxidized under a high-temperature environment of 250 DEG C or above, resulting in a sharp decrease in mechanical properties (tensile strength, elongation at break), such as a tensile strength loss rate of more than 50% after aging for 2 hours at 280 DEG C; high compression permanent deformation rate: automobile sealing parts, tires and other parts need to bear compression stress for a long time, and the compression permanent deformation rate of the existing silicone rubber is usually higher than 30% at 200 DEG C, which easily leads to sealing failure and tire deformation exceeding the standard; poor adaptability to extreme temperature: special scenes (such as lunar vehicle tires) need to withstand alternating environments from-180 DEG C low temperature to 130 DEG C high temperature, and the existing material is easily brittle (at low temperature) or excessively softened (at high temperature) in the range, with a deformation of more than 10%; it is difficult to balance mechanical properties and heat resistance: single addition of heat-resistant agents (such as iron oxide and cerium oxide) can improve heat resistance, but easily leads to a decrease in mechanical properties; and when high mechanical properties are pursued, the high-temperature stability is sacrificed.

[0003] Therefore, according to the related technology in the above, it is urgent to develop a high-temperature-resistant mixing silicone rubber and a preparation method thereof. SUMMARY

[0004] In view of the above, the purpose of the present application is to provide a high-temperature-resistant mixing silicone rubber and a preparation method thereof, so as to solve the problems of insufficient high-temperature resistance, high compression permanent deformation rate, poor stability at extreme temperature and difficult balance between mechanical properties and heat resistance of the silicone rubber in the prior art.

[0005] Based on the above purpose, the present application provides a high-temperature-resistant mixing silicone rubber and a preparation method thereof.

[0006] The high-temperature-resistant mixing silicone rubber comprises the following raw materials by mass: 100 parts of a composite raw rubber system, 35-45 parts of reinforcing fillers, 2-5 parts of a structure control agent, 4-8 parts of a composite heat-resistant agent, 5-9 parts of a low compression deformation aid, 8-12 parts of a plasticizer, 2-3 parts of an antioxidant, 0.8-1.2 parts of a vulcanizing agent and 5-10 parts of a heat-conducting filler.

[0007] Preferably, the composite raw rubber system is obtained by mixing methyl vinyl silicone rubber and methyl phenyl vinyl silicone rubber in a mass ratio of 50-70:30-50.

[0008] Preferably, the methyl vinyl silicone rubber has a vinyl content of 1.0%-1.2%.

[0009] Preferably, the methyl phenyl vinyl silicone rubber has a phenyl content of 25%-35% and a vinyl content of 0.08%-0.1%.

[0010] Preferably, the reinforcing filler is fumed white carbon black, and the fumed white carbon black has a specific surface area of 180-220 m 2 / g.

[0011] Preferably, the structure control agent is a hydroxyl silicone oil, and the hydroxyl silicone oil has a viscosity of 100-300 mPa·s.

[0012] Preferably, the composite heat-resistant agent is a mixture of cerium oxide, titanium dioxide and iron oxide in a mass ratio of 2-4:1-2:1-2.

[0013] Preferably, the low compression deformation aid is a mixture of magnesium oxide, calcium oxide and vinyl siloxane in a mass ratio of 1-3:2-4:2-3.

[0014] Preferably, the plasticizer is a mixture of phenyl silicone oil and methyl silicone oil in a mass ratio of 4-6:4-6.

[0015] Preferably, the antioxidant is a general rubber antioxidant.

[0016] Preferably, the vulcanizing agent is 2,5-dimethyl-2,5-bis(tert-butyl peroxy) hexane.

[0017] Preferably, the heat-conducting filler is SiC powder, and the SiC powder has a particle size of 0-20 μm.

[0018] A preparation method of a high-temperature-resistant mixed silicone rubber, comprising the following steps: Step S1. Masterbatch preparation: a composite raw rubber system, fumed white carbon black and a structure control agent are added into a 50T type internal mixer, and the temperature is controlled to be ≤100 ℃ for mixing for 15-20 min until the raw materials are uniformly mixed; then the temperature is increased to 160-180 ℃ for heat preservation mixing for 2-3 h to promote the dispersion of the white carbon black and inhibit the structuring; finally, the temperature is decreased to below 30 ℃, and the masterbatch is discharged; Step S2. Secondary cold mixing: the masterbatch is re-fed into the internal mixer, and a composite heat-resistant agent, a low compression deformation aid and an antioxidant are sequentially added, and the temperature is controlled to be ≤80 ℃ for mixing for 10 min; then a plasticizer is added, and the mixing is continued for 10-15 min to obtain a mixed base rubber. The secondary cold mixing can avoid the pre-vulcanization caused by the aids and prolong the storage period of the rubber compound. Step S3. vulcanizing agent addition and plasticizing: transfer the mixed base rubber to an open mill, plasticize for 5-8 min to evenly wrap the roller; add the vulcanizing agent, thin pass 8-14 times, each time the thickness is 0.5-1 mm, and punch the triangle bag 3-5 times to ensure uniform dispersion of the vulcanizing agent, and the thickness of the film is 2-5 mm; Step S4. Two-stage vulcanization: primary vulcanization: place the film into a flat vulcanizing machine, vulcanize at 165-175 DEG C, 10-15 MPa pressure for 8-12 min; secondary vulcanization: transfer the primary vulcanized film into a hot air circulating oven, vulcanize at 200-210 DEG C for 100-140 min to remove residual vulcanizing agent decomposition products and improve thermal stability; after vulcanization, naturally cool to room temperature to obtain a high-temperature-resistant mixed silicone rubber product.

[0019] The beneficial effects of the present application are: The present application provides a high-temperature-resistant mixed silicone rubber and a preparation method thereof, and has the following beneficial effects compared with the prior art: Significant improvement in high-temperature aging performance: the composite heat-resistant agent can capture silicon rubber side group oxidation free radicals and inhibit main chain cleavage, and the tensile strength retention rate is ≥70% and the elongation at break retention rate is ≥60% after 72h aging at 280 DEG C, which is much better than ordinary silicone rubber; Low compression permanent deformation rate: the composite low compression deformation aid can prevent main chain cyclization degradation and side chain oxidation crosslinking, and the compression permanent deformation rate is ≤20% at 200 DEG C x 70h, which meets the long-term sealing requirements of automobile sealing parts; Excellent wide temperature range stability: the composite raw rubber and SiC heat-conducting filler (optional) work together to make the product not brittle at-180 DEG C and not excessively soft at 280 DEG C, with a deformation of ≤5%, which can be adapted to lunar rover tires and other extreme environments; Balanced mechanical properties: fumed white carbon black reinforcement and high crosslinking density of the composite raw rubber make the product have a tensile strength of ≥1.5 MPa and an elongation at break of ≥150% before aging, balancing elasticity and strength; Strong process controllability: the "masterbatch preparation-secondary cold rolling" process avoids presulfidation, and two-stage vulcanization ensures sufficient vulcanization, which is suitable for industrial mass production. DETAILED DESCRIPTION

[0020] To make the purpose, technical scheme and advantages of the present application clearer and more apparent, the present application will be further described in detail below with specific examples.

[0021] Example 1: A preparation method of a high-temperature-resistant mixed silicone rubber, comprising the following steps: S1. Raw material preparation: Methyl vinyl silicone rubber and methyl phenyl vinyl silicone rubber are mixed at a mass ratio of 50:30 to obtain a composite raw rubber system, wherein the vinyl content of methyl vinyl silicone rubber is 1.0%-1.2%, and the phenyl content of methyl phenyl vinyl silicone rubber is 25%-35% and the vinyl content is 0.08%-0.1%; S2. Masterbatch Preparation: Add 100g of the composite raw rubber system, 35g of fumed silica, and 2g of the structure control agent to a 50T internal mixer, and mix at ≤100℃ for 15 minutes until the raw materials are homogeneous; then raise the temperature to 160℃ and maintain the temperature for 2 hours to promote silica dispersion and inhibit structure formation; finally, cool down to below 30℃ and discharge to obtain the masterbatch, wherein the specific surface area of ​​the fumed silica is 180-220m². 2 / g, wherein the structure control agent is hydroxyl silicone oil with a viscosity of 100-300mPa·s; S3. A composite heat-resistant agent is obtained by mixing cerium oxide, titanium dioxide and iron oxide in a mass ratio of 2:1:1; a low compression set aid is obtained by mixing magnesium oxide, calcium oxide and vinylsiloxane in a mass ratio of 1:2:2; and a plasticizer is obtained by mixing phenyl silicone oil and methyl silicone oil in a mass ratio of 4:4. S4. Secondary cold mixing: Put the masterbatch back into the internal mixer, and add 4g of composite heat-resistant agent, 5g of low compression set agent, 2g of antioxidant and 5g of thermally conductive filler in sequence. Mix at ≤80℃ for 10min. Then add plasticizer and continue mixing for 10min to obtain the compound base rubber. Secondary cold mixing can avoid pre-vulcanization caused by the additives and extend the shelf life of the rubber compound. The antioxidant is a general-purpose antioxidant for rubber, and the thermally conductive filler is SiC micro powder with a particle size of 0-20μm. S5. Addition of vulcanizing agent and plasticizing: Transfer the mixed base rubber to an open mixing mill and plasticize for 5 minutes until the roll wrapping is uniform; add 0.8g of vulcanizing agent, pass through the mill 8 times, each pass through a thickness of 0.5-1mm, and make triangular wrapping 3 times to ensure uniform dispersion of the vulcanizing agent, producing a rubber sheet with a thickness of 2-5mm, wherein the vulcanizing agent is 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane; S6. Two-stage vulcanization: First vulcanization: Place the rubber sheet into a flat vulcanizing machine and vulcanize at 165℃ and 10MPa pressure for 8 minutes; Second vulcanization: Transfer the rubber sheet after the first vulcanization to a hot air circulating oven and vulcanize at 200℃ for 100 minutes to remove residual vulcanizing agent decomposition products and improve thermal stability; After vulcanization, allow it to cool naturally to room temperature to obtain the high-temperature resistant compounded silicone rubber product.

[0022] Example 2: A method for preparing a high-temperature resistant compounded silicone rubber, comprising the following steps: S1. Raw material preparation: Methyl vinyl silicone rubber and methyl phenyl vinyl silicone rubber are mixed at a mass ratio of 55:35 to obtain a composite raw rubber system, wherein the vinyl content of methyl vinyl silicone rubber is 1.0%-1.2%, and the phenyl content of methyl phenyl vinyl silicone rubber is 25%-35% and the vinyl content is 0.08%-0.1%; S2. Masterbatch Preparation: Add 100g of the composite raw rubber system, 38g of fumed silica, and 3g of the structure control agent to a 50T internal mixer, and mix at ≤100℃ for 16 minutes until the raw materials are homogeneous; then raise the temperature to 165℃ and hold for 2.5 hours to promote silica dispersion and inhibit structure formation; finally, cool to below 30℃ and discharge to obtain the masterbatch, wherein the specific surface area of ​​the fumed silica is 180-220m². 2 / g, wherein the structure control agent is hydroxyl silicone oil with a viscosity of 100-300mPa·s; S3. A composite heat-resistant agent is obtained by mixing cerium oxide, titanium dioxide and iron oxide in a mass ratio of 2.5:1.5:1.5; a low compression set aid is obtained by mixing magnesium oxide, calcium oxide and vinylsiloxane in a mass ratio of 2:3:2.5; and a plasticizer is obtained by mixing phenyl silicone oil and methyl silicone oil in a mass ratio of 4.5:4.5. S4. Secondary cold mixing: Put the masterbatch back into the internal mixer, add 5g of composite heat-resistant agent, 7g of low compression set agent, 2.5g of antioxidant and 7g of thermally conductive filler in sequence, and mix at ≤80℃ for 10min; then add plasticizer and continue mixing for 12min to obtain the compound base rubber. Secondary cold mixing can avoid pre-vulcanization caused by the additives and extend the shelf life of the rubber compound. The antioxidant is a general-purpose antioxidant for rubber, and the thermally conductive filler is SiC micro powder with a particle size of 0-20μm. S5. Addition of vulcanizing agent and plasticizing: Transfer the mixed base rubber to an open mixing mill and plasticize for 6 minutes until the rolls are uniformly wrapped; add 0.9g of vulcanizing agent, pass through the mill 10 times, each pass having a thickness of 0.5-1mm, and make triangular wraps 4 times to ensure that the vulcanizing agent is evenly dispersed, producing a rubber sheet with a thickness of 2-5mm, wherein the vulcanizing agent is 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane; S6. Two-end vulcanization: First vulcanization: Place the rubber sheet into a flat vulcanizing machine and vulcanize for 9 minutes at 170℃ and 12MPa pressure; Second vulcanization: Transfer the rubber sheet after the first vulcanization to a hot air circulating oven and vulcanize for 120 minutes at 204℃ to remove residual vulcanizing agent decomposition products and improve thermal stability; After vulcanization, allow it to cool naturally to room temperature to obtain the high-temperature resistant compounded silicone rubber product.

[0023] Example 3: A method for preparing a high-temperature resistant compounded silicone rubber, comprising the following steps: S1. Raw material preparation: Methyl vinyl silicone rubber and methyl phenyl vinyl silicone rubber are mixed at a mass ratio of 60:40 to obtain a composite raw rubber system, wherein the vinyl content of methyl vinyl silicone rubber is 1.0%-1.2%, and the phenyl content of methyl phenyl vinyl silicone rubber is 25%-35% and the vinyl content is 0.08%-0.1%; S2. Masterbatch Preparation: Add 100g of the composite raw rubber system, 42g of fumed silica, and 4g of the structure control agent to a 50T internal mixer, and mix at ≤100℃ for 18 minutes until the raw materials are homogeneous; then raise the temperature to 170℃ and mix for 3 hours to promote silica dispersion and inhibit structure formation; finally, cool to below 30℃ and discharge to obtain the masterbatch, wherein the specific surface area of ​​the fumed silica is 180-220m². 2 / g, wherein the structure control agent is hydroxyl silicone oil with a viscosity of 100-300mPa·s; S3. A composite heat resistant agent is obtained by mixing cerium oxide, titanium dioxide and iron oxide in a mass ratio of 3:1.8:1.8; a low compression set aid is obtained by mixing magnesium oxide, calcium oxide and vinylsiloxane in a mass ratio of 2.5:3.5:3; and a plasticizer is obtained by mixing phenyl silicone oil and methyl silicone oil in a mass ratio of 5:5. S4. Secondary cold mixing: Put the masterbatch back into the internal mixer, add 6g of composite heat-resistant agent, 8g of low compression set agent, 2.8g of antioxidant and 9g of thermally conductive filler in sequence, and mix at ≤80℃ for 10min; then add plasticizer and continue mixing for 14min to obtain the compound base rubber. Secondary cold mixing can avoid pre-vulcanization caused by the additives and extend the shelf life of the rubber compound. The antioxidant is a general-purpose antioxidant for rubber, and the thermally conductive filler is SiC micro powder with a particle size of 0-20μm. S5. Addition of vulcanizing agent and plasticizing: Transfer the mixed base rubber to an open mixing mill and plasticize for 7 minutes until the rolls are uniformly wrapped; add 1.0g of vulcanizing agent, pass through the mill 12 times, each pass having a thickness of 0.5-1mm, and make triangular wraps 4 times to ensure that the vulcanizing agent is evenly dispersed, producing a rubber sheet with a thickness of 2-5mm, wherein the vulcanizing agent is 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane; S6. Two-end vulcanization: First vulcanization: Place the rubber sheet into a flat vulcanizing machine and vulcanize at 172℃ and 14MPa pressure for 10 minutes; Second vulcanization: Transfer the rubber sheet after the first vulcanization to a hot air circulating oven and vulcanize at 208℃ for 130 minutes to remove residual vulcanizing agent decomposition products and improve thermal stability; After vulcanization, allow it to cool naturally to room temperature to obtain the high-temperature resistant compounded silicone rubber product.

[0024] Example 4: A method for preparing a high-temperature resistant compounded silicone rubber, comprising the following steps: S1. Raw material preparation: Methyl vinyl silicone rubber and methyl phenyl vinyl silicone rubber are mixed at a mass ratio of 70:50 to obtain a composite raw rubber system, wherein the vinyl content of methyl vinyl silicone rubber is 1.0%-1.2%, and the phenyl content of methyl phenyl vinyl silicone rubber is 25%-35% and the vinyl content is 0.08%-0.1%; S2. Masterbatch Preparation: Add 100g of the composite raw rubber system, 45g of fumed silica, and 5g of the structure control agent to a 50T internal mixer, and mix at ≤100℃ for 20 minutes until the raw materials are homogeneous; then raise the temperature to 180℃ and maintain the temperature for 3 hours to promote silica dispersion and inhibit structure formation; finally, cool down to below 30℃ and discharge to obtain the masterbatch, wherein the specific surface area of ​​the fumed silica is 180-220m². 2 / g, wherein the structure control agent is hydroxyl silicone oil with a viscosity of 100-300mPa·s; S3. A composite heat resistant agent is obtained by mixing cerium oxide, titanium dioxide and iron oxide in a mass ratio of 4:2:2; a low compression set aid is obtained by mixing magnesium oxide, calcium oxide and vinylsiloxane in a mass ratio of 3:4:3; and a plasticizer is obtained by mixing phenyl silicone oil and methyl silicone oil in a mass ratio of 6:6. S4. Secondary cold mixing: Put the masterbatch back into the internal mixer, add 8g of composite heat-resistant agent, 9g of low compression set agent, 3g of antioxidant and 10g of thermally conductive filler in sequence, and mix at ≤80℃ for 10min; then add plasticizer and continue mixing for 15min to obtain the compound base rubber. Secondary cold mixing can avoid pre-vulcanization caused by the additives and extend the shelf life of the rubber compound. The antioxidant is a general-purpose antioxidant for rubber, and the thermally conductive filler is SiC micro powder with a particle size of 0-20μm. S5. Addition of vulcanizing agent and plasticizing: Transfer the mixed base rubber to an open mixing mill and plasticize for 8 minutes until the roll wrapping is uniform; add 1.2g of vulcanizing agent, pass through the mill 14 times, each pass having a thickness of 0.5-1mm, and make triangular wrapping 5 times to ensure uniform dispersion of the vulcanizing agent, producing a rubber sheet with a thickness of 2-5mm, wherein the vulcanizing agent is 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane; S6. Two-end vulcanization: First vulcanization: Place the rubber sheet into a flat vulcanizing machine and vulcanize at 175℃ and 15MPa pressure for 12 minutes; Second vulcanization: Transfer the rubber sheet after the first vulcanization to a hot air circulating oven and vulcanize at 210℃ for 140 minutes to remove residual vulcanizing agent decomposition products and improve thermal stability; After vulcanization, allow it to cool naturally to room temperature to obtain the high-temperature resistant compounded silicone rubber product.

[0025] Comparative Example 1: Compared to Example 1, the composite raw rubber system was replaced with 100g of single methyl vinyl silicone rubber (methyl phenyl vinyl silicone rubber was removed). The other raw material formulations and preparation steps were completely consistent. This comparative example will not be repeated. Finally, the high-temperature resistant compounded silicone rubber product was obtained.

[0026] Comparative Example 2: Compared to Example 1, the composite heat resistant agent (cerium oxide, titanium dioxide, and iron oxide mixed in a mass ratio of 2:1:1) was replaced with 5 parts of single cerium oxide. The other raw material formulations and preparation steps were completely consistent. This comparative example will not be repeated. Finally, the high-temperature resistant compounded silicone rubber product was obtained.

[0027] Comparative Example 3: Compared with Example 1, the low compression set additive was removed (the mixture of magnesium oxide, calcium oxide and vinylsiloxane was removed), and the rest of the raw material formulation and preparation steps were completely the same. This comparative example will not be repeated. Finally, the high temperature resistant compounded silicone rubber product was obtained.

[0028] Comparative Example 4: Compared with Example 1, the thermally conductive filler was removed (SiC micro powder with a particle size of 0-20μm was removed), and the remaining raw material formulation and preparation steps were completely consistent. This comparative example will not be repeated. Finally, the high-temperature resistant compounded silicone rubber product was obtained.

[0029] Comparative Example 5: Compared to Example 1, the vulcanization process was simplified to "only one vulcanization (vulcanization at 165℃ and 10MPa for 8 minutes), removing the secondary vulcanization step". The remaining raw material formulation and preparation steps are completely consistent. This comparative example will not repeat the details. Finally, the high-temperature resistant compounded silicone rubber product is obtained.

[0030] Performance testing: All test samples (Examples 1-4, Comparative Examples 1-5) were prepared according to a uniform standard. Each test was repeated three times and the average value was taken. The specific test methods are as follows: Shore A hardness test: The test is conducted using an LX-A type Shore hardness tester in accordance with ASTM D2240-15 (2021) standard. The test specimen must meet the requirements of 6mm thickness, 20mm diameter and smooth surface without bubbles.

[0031] Room temperature tensile strength and elongation at break tests: In accordance with ASTM D412-16 (2021) standard, the tests were conducted using an AI-7000-SU1 tensile testing machine. The test specimens were type 1 dumbbell-shaped, and the tensile speed was controlled at 50 mm / min.

[0032] High-temperature aging resistance test: Referring to ASTM D573-04 standard, the tensile test specimens were first placed in a PHH101 electric thermostatic drying oven and aged in hot air at 280℃ for 72 hours. After aging, the specimens were removed, cooled to room temperature, and then the tensile strength and elongation at break were tested using the above tensile testing machine. The performance retention rate was calculated (retention rate = performance value after aging / performance value before aging × 100%).

[0033] Compression set test: In accordance with ASTM D395-2003 (Method B) standard, a 547-401 thickness gauge and a high-temperature compression device were used for testing. The test specimen was a cylindrical specimen with a diameter of 29 mm and a thickness of 12 mm. It was subjected to a 25% compression rate at 200℃ and kept at that temperature for 70 h. After the heat preservation was completed, the pressure was released, and the specimen thickness was measured after cooling to room temperature. The compression set was then calculated.

[0034] Low-temperature brittle fracture performance test: In accordance with GB / T 15256-2014 standard, the test was conducted using a -196℃ liquid nitrogen cryogenic chamber and an impact testing machine. The test specimen was a cuboid of 10mm×10mm×50mm. The specimen was first kept at -180℃ for 2 hours. After the heat preservation was completed, an impact test was immediately conducted with an impact energy of 2J. The specimen was observed to see if brittle fracture occurred and the crack length.

[0035] Thermal conductivity testing: Following GB / T 3399-82 standard, the thermal conductivity was tested using a DRL-Ⅲ type vacuum heat flow method thermal conductivity meter. The test sample was a 30mm × 30mm × 5mm cube. The vacuum level was controlled at ≤10Pa, and the test temperature was 25℃. The test data are shown in Tables 1-5 below: Table 1 Summary of test results for Examples 1-2

[0036] Table 2 Summary of test results for Examples 3-4

[0037] Table 3 Summary of test results for Comparative Examples 1 and 2

[0038] Table 4 Summary of test results for Comparative Examples 3-4

[0039] Table 5 Summary of test results for Comparative Example 5

[0040] Data Analysis: Examples 1-4 all meet the core indicators of "high temperature resistance, low compression set, and wide temperature range stability". Among them, Example 3 (composite raw rubber 50-70:30-50, composite heat resistant agent 3:1.8:1.8, low compression set aid 2.5:3.5:3, SiC 9 parts) is the optimal formulation, specifically as follows: The best mechanical properties: room temperature tensile strength of 1.82 MPa (highest in the examples) and elongation at break of 165%, which is due to the synergistic crosslinking of the composite raw rubber (the rigid phenyl of methyl phenyl vinyl silicone rubber increases the crosslinking density, and methyl vinyl silicone rubber ensures elasticity). The best high-temperature aging resistance: 72% of tensile strength and 61.8% of elongation at break are retained after 280℃×72h. The synergistic effect of cerium oxide (capturing free radicals), titanium dioxide (inhibiting side chain oxidation), and iron oxide (stabilizing the main chain) in the composite heat resistant agent is maximized. Lowest compression set: 18.5% compression set at 200℃ for 70h. The magnesium oxide / calcium oxide in the low compression set additive inhibits main chain cyclization, and vinylsiloxane enhances the elasticity of the crosslinking network, synergistically reducing deformation. The best thermal conductivity: 0.74 W / (m・K). The SiC micro powder forms a continuous thermally conductive network, which reduces the heat accumulation inside the compound at high temperatures and indirectly improves aging stability.

[0041] In Example 4, due to the excessive amount of methylphenyl vinyl silicone rubber in the composite raw rubber ratio (70:50), the rigidity was enhanced, resulting in a slight decrease in the elongation at break (158%), but it still met the requirement of ≥150%. This indicates that the raw rubber ratio needs to be controlled within the range of 50-70:30-50 to avoid excessive rigidity affecting elasticity.

[0042] Comparative Example 1 (single raw rubber) had a room temperature tensile strength (1.25 MPa) that was 17.7% lower than that of Example 1, and it exhibited brittle fracture at -180°C. After aging at 280°C, the tensile strength retention rate (51.2%) was only 72% of that of Example 1. This is because Comparative Example 1 lacked the rigid phenyl group of methylphenyl vinyl silicone rubber, resulting in a decrease in crosslinking density (decreased mechanical properties). Furthermore, the effect of the phenyl group on improving the flexibility of the molecular chain at low temperatures disappeared (low-temperature brittle fracture), and the main chain was more prone to decomposition at high temperatures (low aging retention rate). In contrast, the tensile strength retention rate (54.7%) of Comparative Example 2 (single heat resistant agent) after aging at 280℃ was 23% lower than that of Example 1, and the elongation at break retention rate (45.9%) was 25% lower. This is because cerium oxide alone can only capture some free radicals and cannot inhibit side chain oxidation (the effect of titanium dioxide) and main chain degradation (the effect of iron oxide). The "synergistic blocking" effect of heat aging is missing, which leads to aggravated loss of mechanical properties during the aging process. In contrast, the compression set of Comparative Example 3 (without low compression set additive) at 200℃ for 70h (35.7%) was 86% higher than that of Example 1, far exceeding the target of ≤20%. This is because without magnesium oxide / calcium oxide, the main chain of silicone rubber is prone to cyclization degradation at high temperatures (molecular chain breakage leads to decreased elasticity), and without vinylsiloxane, the crosslinking network is not elastic enough to resist long-term compressive stress, resulting in increased permanent deformation. The thermal conductivity of Comparative Example 4 (without SiC thermally conductive filler) (0.27 W / (m·K)) was only 39.7% of that of Example 1, and the tensile strength retention rate after aging at 280°C (58.0%) was 20% lower. This is because without SiC, the heat inside the rubber compound cannot be dissipated in time, and the local temperature exceeds 280°C at high temperatures, which accelerates the main chain cracking and side chain oxidation, resulting in a decrease in aging performance. Comparative Example 5 (simplified vulcanization process) showed a room temperature tensile strength (1.38 MPa) that was 9.2% lower than that of Example 1, a 280°C aging retention rate (52.2%) that was 27% lower, and brittle fracture at -180°C. This is because, without secondary vulcanization, residual decomposition products of the vulcanizing agent (such as tert-butanol) were not removed, which would catalyze the main chain cracking at high temperatures, and the crosslinking network was not sufficiently perfect (resulting in decreased mechanical properties), while the molecular chain lacked flexibility at low temperatures (leading to brittle fracture). The composite raw rubber system, composite heat-resistant agent, low compression set agent, SiC thermally conductive filler, and two-stage vulcanization process of this invention work synergistically to achieve "high temperature aging resistance (280℃×72h retention rate ≥70%), low compression set (≤20%), wide temperature range stability (-180℃ no brittleness), and excellent mechanical properties (tensile strength ≥1.5MPa)" to meet the needs of high-end applications such as automotive seals and special tires.

[0043] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention is limited to these examples; within the framework of the invention, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity.

[0044] This invention is intended to cover all such substitutions, modifications, and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A high-temperature resistant compounded silicone rubber, characterized in that, Includes the following quantities of raw materials: The composition consists of 100 parts of a composite raw rubber system, 35-45 parts of reinforcing filler, 2-5 parts of a structure control agent, 4-8 parts of a composite heat resistant agent, 5-9 parts of a low compression set aid, 8-12 parts of a plasticizer, 2-3 parts of an antioxidant, 0.8-1.2 parts of a vulcanizing agent, and 5-10 parts of a thermally conductive filler.

2. The high-temperature resistant compounded silicone rubber according to claim 1, characterized in that, The composite raw rubber system is obtained by mixing methyl vinyl silicone rubber and methyl phenyl vinyl silicone rubber in a mass ratio of 50-70:30-50.

3. The high-temperature resistant compounded silicone rubber according to claim 1, characterized in that, The vinyl content of the methyl vinyl silicone rubber is 1.0%-1.2%; The methyl phenyl vinyl silicone rubber contains 25%-35% phenyl and 0.08%-0.1% vinyl.

4. The high-temperature resistant compounded silicone rubber according to claim 1, characterized in that, The reinforcing filler is fumed silica, and the specific surface area of ​​the fumed silica is 180-220 m² / g.

5. The high-temperature resistant compounded silicone rubber according to claim 1, characterized in that, The structuring control agent is hydroxyl silicone oil, and the viscosity of the hydroxyl silicone oil is 100-300 mPa·s.

6. The high-temperature resistant compounded silicone rubber according to claim 1, characterized in that, The composite heat-resistant agent is obtained by mixing cerium oxide, titanium dioxide and iron oxide in a mass ratio of 2-4:1-2:1-2.

7. The high-temperature resistant compounded silicone rubber according to claim 1, characterized in that, The low compression set aid is obtained by mixing magnesium oxide, calcium oxide and vinylsiloxane in a mass ratio of 1-3:2-4:2-3.

8. The high-temperature resistant compounded silicone rubber according to claim 1, characterized in that, The plasticizer is obtained by mixing phenyl silicone oil and methyl silicone oil in a mass ratio of 4-6:4-6; The antioxidant is a general-purpose antioxidant for rubber. The vulcanizing agent is 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane.

9. The high-temperature resistant compounded silicone rubber according to claim 1, characterized in that, The thermally conductive filler is SiC micro powder, and the particle size of the SiC micro powder is 0-20μm.

10. A method for preparing a high-temperature resistant compounded silicone rubber, comprising the following steps: Step S1. Preparation of masterbatch: Add the composite raw rubber system, fumed silica, and structure control agent to a 50T internal mixer and mix at a temperature ≤100℃ for 15-20 minutes until the raw materials are uniform; then raise the temperature to 160-180℃ and mix for 2-3 hours; finally, cool down to below 30℃ and discharge the material to obtain masterbatch. Step S2. Secondary cold mixing: Put the masterbatch back into the internal mixer, add the composite heat resistant agent, low compression set agent and antioxidant in sequence, and mix at ≤80℃ for 10 minutes; then add the plasticizer and continue mixing for 10-15 minutes to obtain the compound base rubber. Step S3. Adding vulcanizing agent and plasticizing: Transfer the mixed base rubber to an open mixing mill and plasticize for 5-8 minutes until the roll wrapping is uniform; add vulcanizing agent, pass through the mill 8-14 times, each pass through a thickness of 0.5-1mm, and make triangular wraps 3-5 times to produce a rubber sheet with a thickness of 2-5mm. Step S4. Vulcanization at both ends: First vulcanization: Place the rubber sheet into a flat vulcanizing machine and vulcanize at 165-175℃ and 10-15MPa pressure for 8-12 minutes; Second vulcanization: Transfer the rubber sheet after the first vulcanization into a hot air circulating oven and vulcanize at 200-210℃ for 100-140 minutes; After vulcanization, allow it to cool naturally to room temperature to obtain high-temperature resistant compounded silicone rubber.

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