Long-term high-temperature resistant silicone rubber, preparation method and application thereof

Abstract

The application belongs to the technical field of synthetic rubber, and discloses a long-term high-temperature-resistant silicone rubber, which comprises the following raw materials: methyl vinyl silicone rubber, fumed white carbon black, diphenyl silicon diol, coupling agent, nano high-temperature-resistant agent and bivulcanizing agent. Meanwhile, the application also discloses a preparation method of the long-term high-temperature-resistant rubber, which comprises the following steps: taking the raw materials according to the mass ratio, preparing high-strength mixing rubber, kneading and uniformly mixing the high-strength mixing rubber and the nano high-temperature-resistant agent into a group, and mixing and vulcanizing. The long-term high-temperature-resistant silicone rubber prepared by the application has high mechanical strength and long-term and durable high-temperature-resistant performance, can be effectively used under the high-temperature condition of 300 DEG C to 350 DEG C for about 30 days, and can be widely applied to the fields of nuclear cables, aerospace cables and the like.

Description

Technical Field

[0001] This application relates to the field of synthetic rubber technology, specifically to a long-term high-temperature resistant silicone rubber, its preparation method, and its application. Background Technology

[0002] Silicone rubber is a polymeric elastomer that combines inorganic and organic properties. Its molecular backbone is composed of alternating silicon and oxygen atoms, with a silicon-oxygen bond energy of 370 kJ / mol, much higher than that of a typical carbon-carbon bond (240 kJ / mol). This is one of the main reasons for the high thermal stability of silicone rubber. Depending on the monomers used, silicone rubber can be classified into dimethyl silicone rubber, methyl vinyl silicone rubber, phenyl silicone rubber, and fluorosilicone rubber.

[0003] Ordinary silicone rubber has a temperature resistance below 250℃, an initial decomposition temperature of around 420℃, and a maximum decomposition temperature below 600℃. After aging at 200℃ for 240 hours, its aging coefficient will be below 0.5. Methylphenyl silicone rubber can withstand instantaneous temperatures between 300-350℃, but in open, long-term high-temperature environments, the cross-linking point energy of its C / C bonds is low, only 345 KJ / mol, resulting in poor thermal stability. Simultaneously, the phenyl groups on the silicone rubber molecular chain are oxidized, and the main chain undergoes thermal rearrangement and degradation, causing the silicone rubber to lose its physical properties and exhibit poor heat resistance. Currently, the industry has developed heat-resistant rubbers using phenyl silicone rubber as the main processing material, but the longest-term test period above 300℃ is only 7 days, which does not achieve long-term heat resistance. Furthermore, existing technologies also use heat-resistant agents to improve the heat resistance of silicone rubber, but the resulting silicone rubber can only withstand instantaneous or short-term aging at 300-350℃, failing to achieve long-term high-temperature resistance.

[0004] Therefore, in order to meet the long-term use requirements of higher temperature scenarios and more stringent conditions, especially the use requirements of nuclear cables and aerospace cables, it is urgent to develop a silicone rubber with durable high temperature resistance. Summary of the Invention

[0005] To overcome the aforementioned technical problems, this application provides a long-term high-temperature resistant silicone rubber, its preparation method, and its applications. This application involves mixing a high-strength compound with inorganic heat-resistant additives, followed by high-temperature vulcanization to obtain the high-temperature resistant silicone rubber. The silicone rubber obtained in this application possesses high mechanical strength and long-term high-temperature resistance, and can be effectively used for approximately 30 days at temperatures ranging from 300℃ to 350℃. It can be widely used in nuclear power cables, aerospace cables, and other applications.

[0006] In a first aspect, this application provides a long-term high-temperature resistant silicone rubber, comprising the following raw materials in parts by weight:

[0007]

[0008]

[0009] The diphenylsilanediol used in this application is a special structure control agent that can effectively remove residual hydroxyl groups and water from the silicone rubber system. This controls the structuring of the silicone rubber while inhibiting its unbuttoning degradation and improving its high-temperature degradation resistance. Simultaneously, the low content of residual active hydroxyl groups on the surface of fumed silica also contributes to improving the heat resistance of the silicone rubber. Secondly, the surface treatment of fumed silica with a coupling agent improves its hydrophobicity and promotes its compatibility with the polymer, thereby improving the crosslinking network and enhancing the high-temperature resistance of the silicone rubber. Thirdly, the precise proportions of the components in the silicone rubber allow the vulcanized silicone rubber to possess high mechanical strength and long-term high-temperature resistance, enabling effective use for approximately 30 days at 300℃–350℃.

[0010] Preferably, the composition comprises 100 parts of methyl vinyl silicone rubber, 45 parts of fumed silica, 7 parts of diphenylsilanediol, 1 part of coupling agent, 7.5 parts of nano high-temperature resistant agent, and 3.2 parts of divulcanizing agent.

[0011] Experimental analysis shows that by controlling the amount of each component in the silicone rubber to the above-mentioned mass fractions, the mechanical strength and high-temperature resistance of the vulcanized silicone rubber can be further improved.

[0012] Preferably, the methyl vinyl silicone rubber is a dihydroxyl-terminated methyl vinyl silicone rubber, and the vinyl content is 0.04-0.05% in molar percentage.

[0013] This application introduces active terminal hydroxyl groups into methyl vinyl silicone rubber while reducing the vinyl content in the silicone rubber molecular structure, which can reduce CC crosslinking points and effectively improve the thermal stability of silicone rubber.

[0014] Preferably, the specific surface area of ​​the fumed silica is 180-220 m² / g. 2 / g.

[0015] This application controls the specific surface area of ​​fumed silica within a certain range because as the amount of fumed silica increases, the hardness of vulcanized silicone rubber increases, which can enhance the tensile strength and tear strength of silicone rubber within a certain range. The specific surface area of ​​fumed silica affects its effectiveness; therefore, the specific surface area is controlled at 180-220 μm. 2 Within / g, it can more effectively enhance the mechanical strength of silicone rubber.

[0016] In some specific embodiments, the specific surface area of ​​the fumed silica can be 180 m². 2 / g、185m 2 / g、190m 2 / g、195m 2 / g、200m 2 / g、205m 2 / g、210m 2 / g、215m 2 / g、220m 2 / g, while the specific surface area can also be 180-185m² 2 / g、180-190m 2 / g、185-195m 2 / g、190-200m 2 / g、200-210m 2 / g、210-220m 2 / g. Experimental analysis shows that by controlling the specific surface area of ​​fumed silica within the above-mentioned value or range, this application can further improve the mechanical strength of the vulcanized silicone rubber.

[0017] Preferably, the coupling agent is a silane coupling agent, preferably any one of dimethyldichlorosilane, hexamethyldisilazane, and vinyltrimethoxysilane, and more preferably vinyltrimethoxysilane.

[0018] Fumed silica contains a certain amount of active hydroxyl groups on its surface. When added to silicone rubber as a reinforcing agent, it can cause structuring of the compound and affect the product's temperature resistance, necessitating surface modification. Modifying fumed silica by adding silane coupling agents can enhance its dispersibility in the silicone rubber system, making it more uniform. Furthermore, it can form a bonding layer between the organic matrix, silane coupling agent, and inorganic matrix within the silicone rubber system, thus strengthening the bond between the fumed silica powder and methyl vinyl silicone rubber (hydroxyl-terminated). There are dozens of types of silane coupling agents, including amino, chloro, alkenyl, epoxy, and methacryloxy, such as dimethyldichlorosilane, hexamethyldisilazane, and vinyltrimethoxysilane, which are commonly used. The surface modification of fumed silica is highly dependent on the silicone rubber system in which it is applied, making it highly targeted from an application perspective. In the silicone system based on methyl vinyl in this application, when vinyltrimethoxysilane is used to modify fumed silica, the reaction between CY on the surface of vinyltrimethoxysilane and methyl vinyl is more active, which is more conducive to enhancing the bonding force and thus effectively improving the high-temperature resistance of silicone rubber.

[0019] Preferably, the nano-high temperature resistant agent is treated with a surface modifier, wherein the surface modifier is n-dodecyltrimethoxysilane, and the dosage is 1:3.

[0020] In this application, n-dodecyltrimethoxysilane is used to modify the surface of the nano-high temperature resistant agent, which can improve its compatibility with the base material. At the same time, the surface-modified nano-high temperature resistant agent has a fine particle size and small specific surface area, resulting in better dispersibility in silicone rubber. It can effectively inhibit the side group oxidation reaction of silicone rubber at high temperatures and prolong its high temperature resistance duration.

[0021] The surface modification specifically involves dynamically heating the nano-high temperature resistant agent powder to 100℃-110℃, while simultaneously adding the hydrolyzed surface modifier n-dodecyltrimethoxysilane via atomization. The reaction is maintained for about 10 minutes to promote its full dehydration, condensation and curing, and to maintain a high activation rate (greater than 99%).

[0022] Preferably, the nano-high temperature resistant agent is a mixture of nano-alumina, nano-iron oxide, and nano-cerium oxide. The nano-alumina, nano-iron oxide, and nano-cerium oxide all have a particle size of less than 100 nanometers and a specific surface area greater than 4 m². 2 / g.

[0023] The addition of an appropriate amount of nano-sized alumina in this application can absorb trace amounts of acidic or alkaline substances in the silicone rubber system that promote degradation reactions, thereby improving the system's heat resistance. At the same time, nano-iron oxide and cerium oxide are easily variable valence metal compounds. Under high temperature conditions, high-valence metal ions capture free radicals generated during the oxidation of silicone rubber, and the metal ions undergo redox reactions, being reduced from high-valence states to low-valence states. Within a certain temperature range, this prevents the continuous progress of chain growth reactions, thereby improving the heat resistance of silicone rubber to air aging.

[0024] Preferably, the mass ratio of the nano-alumina, nano-iron oxide, and nano-cerium oxide is (1-2):(4-6):(1-2). In some specific embodiments, the mass ratio of the nano-alumina, nano-iron oxide, and nano-cerium oxide can be 1:5:1, 1:7:2, 2:6:1, 2:8:3, etc. Experimental analysis shows that by controlling the specific surface area of ​​fumed silica within the above values ​​or ranges, this application can further improve the mechanical strength of the vulcanized silicone rubber.

[0025] Preferably, the disulfide agent is a peroxide sulfide agent and a polysilazane, wherein the peroxide sulfide agent is selected from one or more of di-tert-butyl peroxide (DTBP), dicumyl peroxide (DCP), and 2,5-dimethyl-2,5-di-tert-butylperoxide (DBP), and the mass ratio of the peroxide sulfide agent to the polysilazane is 1:3.

[0026] This application employs a dual-curing agent system of peroxide curing agent and polysilazane. The polysilazane can undergo a pick reaction to form crosslinks through the reaction of silanol and silanine groups. Simultaneously, the free radicals generated from the decomposition of the peroxide curing agent can synergistically crosslink with the polysilazane within a short time, promoting rapid vulcanization of the silicone rubber. Furthermore, in some specific embodiments, the mass ratio of the peroxide curing agent to the polysilazane can be 1:3. Experimental analysis shows that controlling the mass ratio within the above-mentioned value or range allows for more complete vulcanization of the rubber, resulting in a higher degree of crosslinking, and also reduces the displacement and stress relaxation of the silicone rubber molecular chains at high temperatures.

[0027] Secondly, this application also provides a method for preparing the long-term high-temperature resistant silicone rubber described in the first aspect, the method comprising the following steps:

[0028] 1) Weigh out the following components by mass: methyl vinyl silicone rubber, fumed silica, diphenylsilanediol, coupling agent, nano high-temperature resistant agent, and disulfide agent.

[0029] 2) The methyl vinyl silicone rubber is added to a mixer at room temperature in one go. 25-35% of the total mass of fumed silica is added initially, and the mixture is mechanically sheared and heated to 160-170℃. The remaining fumed silica is then added in multiple batches. The mixture is heat-treated for 1-2 hours, and diphenylsilanediol and coupling agent are added simultaneously. The mixture is then thoroughly mixed and heat-treated for 0.8-1.5 hours at 160-170℃ and a negative pressure of 0.06-0.09 MPa to obtain a high-strength compound.

[0030] 3) Knead and mix the high-strength compound and the nano high-temperature resistant agent into a ball, mix at room temperature for 2-3 hours, then heat to 145-155℃, vacuum and continue mixing for 1-2 hours, and then cool naturally.

[0031] 4) Pass the material obtained in step 3) through a two-roll mill 15-20 times, add the disulfide agent and mix at room temperature for 15-20 minutes to obtain the final product.

[0032] Preferably, the nano high-temperature resistant agent in step (1) is a surface-modified nano high-temperature resistant agent; the surface modification specifically involves dynamically heating the nano high-temperature resistant agent powder to 100℃-110℃, while simultaneously adding the hydrolyzed surface modifier n-dodecyltrimethoxysilane by atomization, and maintaining the reaction for about 10 minutes to promote its full dehydration, condensation and curing, and maintain a high activation rate (greater than 99%).

[0033] Preferably, the mass of fumed silica added for the first time in step (2) can be 25%, 30%, or 35% of the total mass, or it can be 25%-30% or 30%-35%.

[0034] Preferably, the heating temperature for mechanical shearing in step (2) can be 160℃, 165℃, or 170℃, or it can be 160-165℃ or 165-170℃.

[0035] Preferably, the first mixing time in step (3) can be 2 hours, 2.5 hours or 3 hours, or 2-2.5 hours or 2.5-3 hours; the second mixing time can be 1 hour, 1.5 hours or 2 hours, or 1-1.5 hours or 1.5-2 hours.

[0036] Preferably, the vacuum level in step (3) is 0.08 MPa.

[0037] Experimental analysis shows that by controlling the parameters in the preparation method within the above-mentioned values ​​or ranges, the mechanical strength of the vulcanized silicone rubber can be further improved.

[0038] Thirdly, this application also provides the application of the long-term high-temperature resistant silicone rubber mentioned in the first aspect above in the preparation of nuclear cables or aerospace cables.

[0039] In summary, this application has the following technical advantages over the prior art:

[0040] 1) This application introduces active terminal hydroxyl groups into methyl vinyl silicone rubber and uses polysilazane as a crosslinking agent to form Si-O-Si crosslinking points with high thermal stability and bond energy up to 451 KJ / mol, effectively improving the heat resistance of the silicone rubber. Simultaneously, diphenylsilanediol is added as a special structure control agent to the high-temperature resistant silicone rubber composition of this application, effectively removing residual hydroxyl groups and water from the silicone rubber system, thereby controlling the structuring of the silicone rubber while inhibiting its unbuttoning degradation. The surface treatment of fumed silica with the coupling agent vinyltrimethoxysilane improves the hydrophobicity of the silica and promotes the compatibility between the fumed silica and the polymer, thereby improving the crosslinking network and enhancing the durability of high-temperature resistance.

[0041] 2) The nano-high temperature resistant agent added in this application is a nano-high temperature resistant agent modified with n-dodecyltrimethoxysilane. Modification can improve its compatibility with the base material. At the same time, the surface-modified nano-high temperature resistant agent has a fine particle size and small specific surface area, which results in better dispersibility in silicone rubber and can effectively inhibit the side group oxidation reaction of silicone rubber at high temperatures, thereby ensuring its high temperature resistance and duration.

[0042] 3) This application uses a dual vulcanizing agent system, which uses both peroxide vulcanizing agent and polysilazane. The polysilazane can undergo a cross-linking reaction between silanol and silanine according to the pick reaction. At the same time, the free radicals generated by the decomposition of the peroxide vulcanizing agent can also play a synergistic cross-linking role with the polysilazane in a short time, promoting the rapid vulcanization of silicone rubber.

[0043] 4) Using the preparation method of this application, high-strength compound rubber and inorganic heat-resistant additives are mixed to prepare a high-temperature resistant silicone rubber composition, which is then vulcanized at high temperature to obtain high-temperature resistant silicone rubber. The preparation method is simple and convenient and has high versatility. The high-temperature resistant silicone rubber prepared by this application can be effectively used for about 30 days under high temperature conditions of 300℃~350℃, and can be well applied to nuclear cables, aerospace cables, etc. Detailed Implementation

[0044] The present application will be further described below with reference to specific embodiments, and the advantages and features of the present application will become clearer with the description. It should be noted that: unless otherwise specified in the following embodiments, the conditions are carried out according to conventional conditions or the conditions recommended by the manufacturer, and the raw materials used in the following embodiments are all from commercially available sources unless otherwise specified.

[0045] Preparation Example

[0046] 1 kg of nano-alumina, 4 kg of nano-iron oxide, and 1 kg of nano-cerium oxide powder were dynamically heated to 100°C. 18 kg of hydrolyzed surface modifier n-dodecyltrimethoxysilane was added by atomization. The reaction was maintained for about 10 minutes to promote full dehydration, condensation, and curing, while maintaining a high activation rate (greater than 99%), thus obtaining modified nano-alumina, modified nano-iron oxide, and modified nano-cerium oxide.

[0047] Example 1

[0048] A long-term high-temperature resistant silicone rubber comprises the following raw materials by weight (kg): 80 kg of methyl vinyl silicone rubber (hydroxyl-terminated), 40 kg of fumed silica, 6 kg of diphenylsilanediol, 1 kg of vinyltrimethoxysilane, 1 kg of modified nano alumina, 4 kg of modified nano iron oxide, 1 kg of modified nano cerium oxide, 0.5 kg of bis(2,5-diphenyl)propane, and 1.5 kg of polysilazane.

[0049] The preparation method of the above-mentioned long-term high-temperature resistant silicone rubber includes the following steps:

[0050] 1) Weigh out the following by weight: methyl vinyl silicone rubber, fumed silica, diphenylsilanediol, vinyltrimethoxysilane, modified nano alumina, modified nano iron oxide, modified nano cerium oxide, bis(2,5-diphenyl)silane, and polysilazane.

[0051] 2) Add methyl vinyl silicone rubber to a mixer at room temperature in one go, then add 10 kg of fumed silica, mechanically shear and heat to 160°C, add the remaining fumed silica in three batches of 10 kg each, heat treat for 1 hour, add diphenylsilanediol and vinyltrimethoxysilane at the same time, mix evenly, heat treat for 0.8 hours at 160°C and negative pressure of 0.06 MPa to obtain high-strength compound;

[0052] 3) Knead and mix the high-strength compound with the modified nano-alumina, modified nano-iron oxide, and modified nano-cerium oxide into a ball, mix at room temperature for 2 hours, then heat to 145℃ and continue mixing under vacuum for 1.5 hours, then let it cool naturally.

[0053] 4) Pass the material obtained in step 3) through a two-roll mill 15 times, add bis(2,5-diphenyltrimethylammonium chloride) and polysilazane and mix at room temperature for 15 minutes to obtain the final product.

[0054] Examples 2-5

[0055] Examples 2-5 all provide a long-term high-temperature resistant silicone rubber. The raw material composition by weight is shown in Table 1. Examples 2-5 are all prepared according to the preparation method of Example 1.

[0056] Table 1 Raw material composition of long-term high-temperature resistant silicone rubber in Examples 1-5

[0057]

[0058]

[0059] Example 6

[0060] Example 6 provides a long-term high-temperature resistant silicone rubber. The only difference between this example and Example 1 is that the coupling agent vinyltrimethoxysilane is replaced with dimethyldichlorosilane. The rest is the same as in Example 1.

[0061] Example 7

[0062] Example 7 provides a long-term high-temperature resistant silicone rubber. The only difference between this example and Example 1 is that the coupling agent vinyltrimethoxysilane is replaced with hexamethyldisilazane. The rest is the same as in Example 1.

[0063] Example 8

[0064] Example 8 provides a long-term high-temperature resistant silicone rubber. The only difference between this example and Example 1 is that the peroxide vulcanizing agent polysilazane is replaced with di-tert-butyl peroxide (DTBP), and the rest is the same as in Example 1.

[0065] Example 9

[0066] Example 9 provides a long-term high-temperature resistant silicone rubber. The only difference between this example and Example 1 is that the peroxide vulcanizing agent polysilazane is replaced with dicumyl peroxide (DCP), and the rest is the same as Example 1.

[0067] Comparative Examples 1-7

[0068] Comparative Examples 1-7 all provide a long-term high-temperature resistant silicone rubber. The raw material composition by weight is shown in Table 2. All were prepared according to the preparation method of Example 1.

[0069] Table 2 Raw material composition of comparative examples 1-7 long-term high-temperature resistant silicone rubber

[0070]

[0071]

[0072] Comparative Example 1

[0073] Comparative Example 1 provides a long-term high-temperature resistant silicone rubber. The only difference between this comparative example and Example 3 is that it does not contain the coupling agent vinyltrimethoxysilane, and the rest is the same as Example 3.

[0074] Comparative Example 2

[0075] Comparative Example 2 provides a long-term high-temperature resistant silicone rubber. The only difference between this comparative example and Example 3 is that the nano high-temperature resistant agents, nano alumina, nano iron oxide, and nano cerium oxide, are not modified by modifiers. The rest are the same as in Example 3.

[0076] Comparative Example 3

[0077] Comparative Example 3 provides a long-term high-temperature resistant silicone rubber. The only difference between this comparative example and Example 3 is that the vulcanizing agent used is a single vulcanizing agent, polysilazane, and the rest is the same as Example 3.

[0078] Comparative Example 4

[0079] Comparative Example 4 provides a long-term high-temperature resistant silicone rubber. The only difference between this comparative example and Example 3 is that the vulcanizing agent used is a single vulcanizing agent, bis(2,5), while the rest is the same as Example 3.

[0080] Comparative Example 5

[0081] Comparative Example 5 provides a long-term high-temperature resistant silicone rubber. The difference between this comparative example and Example 3 is that it does not contain the coupling agent vinyltrimethoxysilane. At the same time, the high-temperature heat-resistant agents nano alumina, nano iron oxide, and nano cerium oxide are unmodified. The rest is the same as in Example 3.

[0082] Comparative Example 6

[0083] Comparative Example 6 provides a long-term high-temperature resistant silicone rubber. The difference between this comparative example and Example 3 is that it does not contain the coupling agent vinyltrimethoxysilane. At the same time, the vulcanizing agent used is a single vulcanizing agent polysilazane. The rest is the same as Example 3.

[0084] Comparative Example 7

[0085] Comparative Example 7 provides a long-term high-temperature resistant silicone rubber. The difference between this comparative example and Example 3 is that it does not contain the coupling agent vinyltrimethoxysilane. At the same time, the vulcanizing agent used is a single vulcanizing agent, bis(2,5-dimethylsiloxane), and the rest is the same as Example 3.

[0086] Performance testing

[0087] Tensile strength and elongation at break tests: The tensile strength and elongation at break of the samples were tested according to GB / T 2951.11-2008 "General Test Methods for Insulation and Sheath Materials of Cables and Optical Fibers - Part 11: General Test Methods - Measurement of Thickness and Dimensions - Mechanical Properties Tests"; Shore hardness tests were conducted according to GB / T 2411-2008; mechanical properties before aging were tested according to GB / T 528-2009; and thermal aging tests were conducted according to GB / T 2951.12-2008. The test data are shown in Table 3.

[0088] Table 3 Performance test results of Examples 1-9 and Comparative Examples 1-7

[0089]

[0090] As can be seen from the experimental results of Examples 1-9, the long-term high-temperature resistant silicone rubber prepared in this application has excellent hardness, tensile strength, and elongation at break. Its average hardness reaches 62.2A, average tensile strength reaches 10.8 MPa, and average elongation at break reaches 485.7%. After a heat aging test (300℃, duration 720h), the average retention rate of tensile strength change reaches 33.42%, and the average retention rate of elongation at break still reaches 30.54%. Therefore, this application uses optimized raw material ratios and preparation methods to prepare silicone rubber with high hardness and high temperature resistance, which can maintain excellent performance even after approximately 30 days at 300℃.

[0091] The experimental results of Examples 1-5, 8-9 and Examples 6-7 show that after the thermal aging test (300℃, duration 720h), the average retention rate of tensile strength change and the average retention rate of elongation at break of Examples 6-7 were 32.28% and 30.63%, respectively, which were significantly lower than those of Examples 1-5 and 8-9. Analysis shows that the coupling agent used in Example 6 was dimethyldichlorosilane, and the coupling agent used in Example 7 was hexamethyldisilazane. Compared with the high-temperature resistant silicone rubber prepared by using vinyltrimethoxysilane as the coupling agent in other examples, the bonding force between fumed silica and the substrate methyl vinyl silicone rubber (hydroxyl-terminated) in Examples 6-7 is relatively weak. Therefore, the tensile strength and elongation at break of the prepared high-temperature resistant silicone rubber decreased after a heat aging test at 300°C for 720 hours. At the same time, it also shows that in the silicone system based on methyl vinyl in this application, when vinyltrimethoxysilane is used to modify fumed silica, the reaction between CY on the surface of vinyltrimethoxysilane and methyl vinyl is more active, which is more conducive to enhancing the bonding force and extending the duration of its high-temperature resistance.

[0092] The experimental results of Examples 1-9 and Comparative Example 1 show that after a thermal aging test (300℃, 720h), the tensile strength of the silicone rubber in Comparative Example 1 was only 2.48MPa, and the elongation at break after aging was only 110%, which is significantly lower than the qualified standard for silicone rubber materials (tensile strength above 3MPa, elongation at break after aging at least 120%). The retention rate of tensile strength change and the retention rate of elongation at break were 24.31% and 24.12%, respectively, which are significantly lower than those of Examples 1-9. This indicates that after modifying fumed silica with a silane coupling agent, this application can enhance its dispersibility in the silica gel system, making it more uniformly dispersed. Furthermore, it can form a bonding layer of organic matrix-silane coupling agent-inorganic matrix in the silica gel system, thus strengthening the bond between the fumed silica powder and methyl vinyl silicone rubber (hydroxyl-terminated).

[0093] The experimental results from Examples 1-9 and Comparative Example 2 show that after a heat aging test (300℃, duration 720h), the tensile strength of the silicone rubber in Comparative Example 2 was only 2.3MPa, and the elongation at break after aging was only 102%, similar to Comparative Example 1, and significantly lower than the qualified standard for silicone rubber materials. Furthermore, the retention rates of tensile strength change and elongation at break were 24.21% and 22.67%, respectively, also significantly reduced. This indicates that the nano-high-temperature resistant agent modified with n-dodecyltrimethoxysilane can improve its compatibility with the base material. Simultaneously, the surface-modified nano-high-temperature resistant agent has a fine particle size and small specific surface area, resulting in better dispersibility in silicone rubber and effectively inhibiting the side group oxidation reaction of silicone rubber at high temperatures, thereby ensuring its high-temperature resistance.

[0094] The experimental results of Examples 1-9 and Comparative Examples 3-4 show that after the heat aging test (300℃, duration 720h), the retention rates of tensile strength change and elongation at break of Comparative Example 3 were 20.10% and 22.12%, respectively, and those of Comparative Example 4 were 20.30% and 21.54%, respectively, which are also significantly reduced. This indicates that the present application uses a dual-vulcanizing agent system, employing both peroxide vulcanizing agent and polysilazane. The polysilazane can undergo a pick reaction to form crosslinks through the reaction of silanol and silanine groups. Simultaneously, the free radicals generated by the decomposition of the peroxide vulcanizing agent can synergistically crosslink with the polysilazane in a short time, promoting rapid vulcanization of the silicone rubber and improving its high-temperature resistance.

[0095] The experimental results of Examples 1-9 and Comparative Examples 1-7 show that after the anti-aging test, the retention rate of tensile strength change and the retention rate of elongation at break of Comparative Example 5 were 18.30% and 21.43%, respectively, which were significantly lower than those of Examples 1-9 and also significantly lower than those of Comparative Examples 1-4. This shows that the use of disulfide alone in the preparation of high-temperature resistant silicone rubber does not have a significant effect on improving the high-temperature resistance of silicone rubber. Similarly, the experimental results of Examples 1-9 and Comparative Examples 1-7 show that after the anti-aging test, the retention rate of tensile strength change and elongation at break of Comparative Example 6 were 18.13% and 19.36%, respectively, and the retention rate of tensile strength change and elongation at break of Comparative Example 7 were 18.17% and 20.41%, respectively, which were significantly lower than those of Examples 1-9 and also significantly lower than those of Comparative Examples 1-4. This shows that in the preparation of high-temperature resistant silicone rubber, the use of surface-modified high-temperature resistant agents (nano-alumina, nano-iron oxide, and nano-cerium oxide) alone has little effect on improving the high-temperature resistance of silicone rubber, and the use of coupling agent vinyltrimethoxysilane to modify fumed silica alone also has little effect on improving the high-temperature resistance of silicone rubber.

[0096] The experimental results of Examples 1-9 and Comparative Examples 1-7 show that, in order to improve the durability of the high-temperature (300-320℃) resistance of silicone rubber, this application uses vinyltrimethoxysilane as a coupling agent to modify fumed silica, and uses n-dodecyltrimethoxysilane-modified nano-high-temperature resistant agent and disulfide agent to finally obtain a long-term high-temperature resistant silicone rubber with high mechanical strength and high-temperature resistance. It can be effectively used for about 30 days under high temperature conditions of 300℃~350℃, and is widely used in nuclear cables, aerospace cables, etc.

[0097] 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 long-term high-temperature resistant silicone rubber, characterized in that, The raw materials include the following parts by weight: 80-120 parts of methyl vinyl silicone rubber 40-50 parts of fumed silica 6-8 parts of diphenylsilanediol 1-1.2 parts of coupling agent 6-10 parts of nano high temperature resistant agent 2-5 parts of disulfide agent; The methyl vinyl silicone rubber is a dihydroxyl-terminated methyl vinyl silicone rubber, wherein the vinyl content is 0.04-0.05% by molar percentage; the fumed silica has a specific surface area of ​​180-220 m² / g. 2 / g; The nano high-temperature resistant agent is a nano high-temperature resistant agent modified with a surface modifier, namely n-dodecyltrimethoxysilane; The nano-high temperature resistant agent is a mixture of nano-alumina, nano-iron oxide, and nano-cerium oxide, wherein the mass ratio of nano-alumina, nano-iron oxide, and nano-cerium oxide is (0.5-1.5):(0.65-0.75):(1.5-2.5). The disulfide is a peroxide disulfide and a polysilazane.

2. The long-term high-temperature resistant silicone rubber according to claim 1, characterized in that, The raw materials include the following parts by weight: 100 parts of methyl vinyl silicone rubber 45 parts of fumed silica 7 parts of diphenylsilanediol 1 part coupling agent 7.5 parts of nano high-temperature resistant agent 3.2 parts of disulfide agent.

3. The long-term high-temperature resistant silicone rubber according to claim 1 or 2, characterized in that, The coupling agent is a silane coupling agent; the silane coupling agent is any one of dimethyldichlorosilane, hexamethyldisilazane, and vinyltrimethoxysilane.

4. The long-term high-temperature resistant silicone rubber according to claim 1 or 2, characterized in that, The peroxide vulcanizing agent is selected from one or more of di-tert-butyl peroxide (DTBP), dicumyl peroxide (DCP), and 2,5-dimethyl-2,5-di-tert-butylperoxide (DBPMH), and the mass ratio of the peroxide vulcanizing agent to polysilazane is 1:

3.

5. The long-term high-temperature resistant silicone rubber according to claim 1 or 2, characterized in that, The long-term high-temperature resistant silicone rubber still has a tensile strength of 3-4 MPa and an elongation at break of at least 120% after continuous use at temperatures above 300°C for more than 30 days.

6. A method for preparing the long-term high-temperature resistant silicone rubber according to any one of claims 1-5, characterized in that, Includes the following steps, 1) Weigh out the following components by weight: methyl vinyl silicone rubber, fumed silica, diphenylsilanediol, coupling agent, nano high-temperature resistant agent, and disulfide agent. 2) The methyl vinyl silicone rubber is added to a mixer at room temperature in one go. 25-35% of the total mass of fumed silica is added initially, and the mixture is mechanically sheared and heated to 160-170℃. The remaining fumed silica is then added in multiple batches. The mixture is heat-treated for 1-2 hours, and diphenylsilanediol and coupling agent are added simultaneously. The mixture is then thoroughly mixed and heat-treated for 0.8-1.5 hours at 160-170℃ and a negative pressure of 0.06-0.09 MPa to obtain a high-strength compound. 3) Knead and mix the high-strength compound and the nano high-temperature resistant agent into a ball, mix at room temperature for 2-3 hours, then heat to 145-155℃, vacuum and continue mixing for 1-2 hours, and then cool naturally. 4) Pass the material obtained in step 3) through a two-roll mill 15-20 times, add the disulfide agent and mix at room temperature for 15-20 minutes to obtain the final product.

7. The application of the long-term high-temperature resistant silicone rubber according to any one of claims 1-5 in the preparation of nuclear cables or aerospace cables.

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