A high temperature resistant silicone rubber seal and preparation method thereof

Abstract

The present invention relates to a high-temperature resistant silicone rubber seal and a method for preparing the same, belonging to the technical field of sealing materials. The high-temperature resistant silicone rubber seal comprises the following components: vinyl silicone rubber, modified silica, composite modified carbon nanotubes, methyl silicone oil, an antioxidant, and an initiator. The carbon nanotubes are modified using a vinyl silane coupling agent, chitosan, mercaptobenzaldehyde, and zinc oxide, resulting in a denser structure for the seal material, significantly improving its tensile strength and high-temperature resistance.

Description

Technical Field

[0001] The invention belongs to the technical field of sealing material, and relates to a high-temperature resistant silicone rubber sealing component and a preparation method thereof. Background Art

[0002] Silicone rubber seals are a widely used, general-purpose component. Their unique physical properties, such as low elastic modulus, high elongation, and excellent gas permeability, have led to their widespread application in various sealing mechanical equipment. Standard silicone rubber has excellent heat resistance and can operate continuously at 180°C. Even at temperatures slightly exceeding 200°C, it can maintain its elasticity for several weeks. Furthermore, it can withstand instantaneous temperatures exceeding 300°C. However, with advances in technology, the heat resistance of existing silicone rubber can no longer meet the high standards required by certain specific industries or heat-resistant equipment.

[0003] With the continuous advancement and expansion of industrial production, more and more sealing machinery and equipment are required to operate for long periods of time in harsh outdoor environments, which undoubtedly places more stringent requirements on the aging resistance of rubber seals. Currently, existing rubber seals on the market have certain deficiencies in high-temperature resistance, especially poor performance in high-temperature thermal aging resistance. This has greatly limited the application range of sealing machinery and equipment and has a negative impact on the service life of the equipment.

[0004] Carbon nanotubes (CNTs) show great potential for improving the high-temperature resistance of silicone rubber seals, but their application also faces several challenges. First, the dispersion of CNTs is a major obstacle. Due to their extremely high aspect ratio and strong van der Waals forces, CNTs tend to aggregate and form agglomerates within the silicone rubber matrix, which can degrade the composite's mechanical properties and heat resistance. Second, the interfacial compatibility between the CNTs and the silicone rubber matrix is another issue that needs to be addressed. If the interfacial bond is not strong enough, the CNTs may fall out of the matrix during high temperatures or prolonged use, resulting in a decrease in seal performance. Summary of the Invention

[0005] The purpose of the present invention is to provide a high-temperature resistant silicone rubber seal and a preparation method thereof. The present invention uses vinyl silane coupling agent, chitosan, mercaptobenzaldehyde and zinc oxide to modify carbon nanotubes to form a denser structure, significantly improving the tensile strength and high-temperature resistance of the seal material.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] A high-temperature resistant silicone rubber seal comprises the following components in parts by weight: 52-58 parts of vinyl silicone rubber, 8-12 parts of modified silicon dioxide, 14-18 parts of composite modified carbon nanotubes, 2.3-3.1 parts of methyl silicone oil, 0.5-0.8 parts of antioxidant and 0.8-1.2 parts of initiator.

[0008] As a preferred technical solution of the present invention, the modified silica is obtained by reacting 10-12 parts by weight of fumed silica, 35-40 parts by weight of ethanol and 3-4 parts by weight of vinyltrimethoxysilane at 60°C for 3 hours, filtering out, washing with ethanol three times, and drying at 90°C to constant weight.

[0009] As a preferred technical solution of the present invention, the antioxidant is prepared by mixing antioxidant 1010 and antioxidant 1076 in a mass ratio of 1.5-1.8:2.0-2.2.

[0010] As a preferred technical solution of the present invention, the vinyl content of the vinyl silicone rubber is 2%; and the initiator is initiator DHBP.

[0011] The present invention discloses a method for preparing the composite modified carbon nanotubes, comprising the following steps:

[0012] S1, placing carboxyl carbon nanotubes in anhydrous ethanol and ultrasonically mixing, adding a silane coupling agent and stirring at a constant temperature, filtering, and drying to obtain prefabricated carbon nanotubes;

[0013] S2, placing the prefabricated carbon nanotubes in an ethanol solution, mixing and preheating, adding acetic acid and chitosan, ultrasonically treating, adding 4-mercaptobenzaldehyde, heating and stirring, centrifuging, removing the lower layer of solids, washing, and drying to obtain organically modified carbon nanotubes;

[0014] S3. After mixing the organic modified carbon nanotubes in deionized water, zinc nitrate is added and stirred, the mixture is allowed to stand, ammonia water is added and the mixture is kept at a constant temperature, the mixture is cooled to room temperature, filtered, and dried to obtain composite modified carbon nanotubes.

[0015] As a preferred technical solution of the present invention, in step S1, the ultrasonic mixing is ultrasonication at a power of 300-400W for 30-40 minutes; the constant temperature stirring is stirring at 68-72°C for 1.0-1.5 hours; the drying is drying at 80°C to constant weight; the mass ratio of the carboxyl carbon nanotubes, anhydrous ethanol and silane coupling agent is 15-18:40-50:2-3; and the silane coupling agent is vinyltriethoxysilane.

[0016] As a preferred technical solution of the present invention, in step S2, the ultrasonic treatment is ultrasonic treatment at a power of 1000-1200W for 20-30 minutes; the preheating is heating to 50°C at a rate of 3-4°C / min; the heating and stirring is stirring at 50-60°C for 5-6 hours; the mass ratio of the prefabricated carbon nanotubes, ethanol solution, acetic acid, chitosan and 4-mercaptobenzaldehyde is 13-15:100-110:0.2-0.3:1.8-2.0:2.5-2.8; and the mass fraction of the ethanol solution is 20%.

[0017] As a preferred technical solution of the present invention, in step S3, the stirring and mixing is carried out at a speed of 800-1000 r / min for 30-40 minutes; the standing time is 3-4 hours; the constant temperature treatment is carried out at a constant temperature of 160-180°C for 1-1.2 hours; the drying is carried out at a temperature of 80°C to constant weight; the dosage ratio of the organically modified carbon nanotubes, deionized water, zinc nitrate and ammonia water is 20-21:60-70:5.2-6.0:8-9; and the mass fraction of the ammonia water is 28%.

[0018] The invention discloses a preparation method of a high-temperature resistant silicone rubber seal, comprising the following steps: heating a kneader to 110° C., adding vinyl silicone rubber, modified silicon dioxide, composite modified carbon nanotubes, methyl silicone oil, an antioxidant and an initiator, kneading for 15-18 minutes, and then vulcanizing on a flat vulcanizer at 240° C. for 8-10 minutes to obtain the seal.

[0019] Beneficial effects of the present invention:

[0020] The present invention adopts vinyl silane coupling agent, chitosan, mercaptobenzaldehyde and zinc oxide to modify carbon nanotubes to form a denser structure, thereby significantly improving the tensile strength and high temperature resistance of the sealing material. DETAILED DESCRIPTION

[0021] In order to further illustrate the technical means and effects adopted by the present invention to achieve the predetermined purpose of the invention, the specific implementation methods, structures, features and effects of the present invention are described in detail below in combination with the embodiments.

[0022] Example 1

[0023] A high-temperature resistant silicone rubber seal comprises the following components in parts by weight: 52 parts of vinyl silicone rubber, 8 parts of modified silicon dioxide, 14 parts of composite modified carbon nanotubes, 2.3 parts of methyl silicone oil, 0.5 parts of antioxidant, and 0.8 parts of initiator; the initiator is initiator DHBP; the vinyl content of the vinyl silicone rubber is 2%; the antioxidant is a mixture of antioxidant 1010 and antioxidant 1076 in a mass ratio of 1.5:2.0;

[0024] The modified silica is prepared by reacting 10 parts by weight of fumed silica, 35 parts by weight of ethanol and 3 parts by weight of vinyltrimethoxysilane at 60°C for 3 hours, filtering out the reacted silica, washing the reacted silica with ethanol three times and drying the reacted silica at 90°C to a constant weight.

[0025] The method for preparing the composite modified carbon nanotubes comprises the following steps:

[0026] S1. Carboxyl carbon nanotubes (model XFD06, item number: 100227, Jiangsu Xianfeng Nanomaterial Technology Co., Ltd.) were placed in anhydrous ethanol and ultrasonicated at 300 W power for 30 min. A silane coupling agent was added and stirred at 68° C. for 1.0 h. The mixture was filtered and dried at 80° C. to constant weight to obtain prefabricated carbon nanotubes. The drying step was as follows: the mass ratio of the carboxyl carbon nanotubes, anhydrous ethanol, and silane coupling agent was 15:40:2; and the silane coupling agent was vinyltriethoxysilane.

[0027] S2. Prefabricated carbon nanotubes were placed in an ethanol solution and mixed, and then the temperature was raised to 50°C at a rate of 3°C / min. Acetic acid and chitosan were added, and the mixture was ultrasonicated at a power of 1000 W for 20 minutes. 4-mercaptobenzaldehyde was added and stirred at 50°C for 5 hours. The solid layer was removed by centrifugation, washed, and dried to obtain organically modified carbon nanotubes; the mass ratio of the prefabricated carbon nanotubes, ethanol solution, acetic acid, chitosan, and 4-mercaptobenzaldehyde was 13:100:0.2:1.8:2.5; and the mass fraction of the ethanol solution was 20%;

[0028] S3. Place the organically modified carbon nanotubes in deionized water and mix them evenly. Then, add zinc nitrate and rotate at 800 r / min for 30 minutes. Let it stand for 3 hours. Then, add ammonia water and keep it at a constant temperature of 160°C for 1 hour. After cooling to room temperature, filter it and dry it at 80°C to constant weight to obtain composite modified carbon nanotubes. The usage ratio of the organically modified carbon nanotubes, deionized water, zinc nitrate and ammonia water is 20:60:5.2:8. The mass fraction of the ammonia water is 28%.

[0029] A preparation method for a high-temperature resistant silicone rubber seal comprises the following steps: heating a kneader to 110°C, adding vinyl silicone rubber, modified silica, composite modified carbon nanotubes, methyl silicone oil, an antioxidant and an initiator, kneading for 15 minutes, and then vulcanizing on a flat vulcanizer at 240°C for 8 minutes to obtain the seal.

[0030] Example 2

[0031] A high-temperature resistant silicone rubber seal comprises the following components by weight: 55 parts of vinyl silicone rubber, 10 parts of modified silicon dioxide, 16 parts of composite modified carbon nanotubes, 2.7 parts of methyl silicone oil, 0.6 parts of antioxidant, and 1 part of initiator; the initiator is initiator DHBP; the vinyl content of the vinyl silicone rubber is 2%; the antioxidant is a mixture of antioxidant 1010 and antioxidant 1076 in a mass ratio of 1.6:2.1;

[0032] The modified silica is prepared by reacting 11 parts by weight of fumed silica, 38 parts by weight of ethanol, and 3.5 parts by weight of vinyltrimethoxysilane at 60°C for 3 hours, filtering out the reacted silica, washing the reacted silica with ethanol three times, and drying the reacted silica at 90°C to a constant weight.

[0033] The method for preparing the composite modified carbon nanotubes comprises the following steps:

[0034] S1. Carboxyl carbon nanotubes (model XFD06, item number: 100227, Jiangsu Xianfeng Nanomaterial Technology Co., Ltd.) were placed in anhydrous ethanol and ultrasonicated at 350W power for 35 minutes. A silane coupling agent was added and stirred at 70°C for 1.2 hours. The mixture was filtered and dried at 80°C to a constant weight to obtain prefabricated carbon nanotubes. The drying step was as follows: the mass ratio of the carboxyl carbon nanotubes, anhydrous ethanol, and silane coupling agent was 16:45:2.5; the silane coupling agent was vinyltriethoxysilane.

[0035] S2. Prefabricated carbon nanotubes were placed in an ethanol solution and mixed, and then the temperature was raised to 50°C at a rate of 3.5°C / min. Acetic acid and chitosan were added, and the mixture was ultrasonicated at 1100 W for 25 minutes. 4-mercaptobenzaldehyde was added and stirred at 55°C for 5.5 hours. The solid layer was removed by centrifugation, washed, and dried to obtain organically modified carbon nanotubes; the mass ratio of the prefabricated carbon nanotubes, ethanol solution, acetic acid, chitosan, and 4-mercaptobenzaldehyde was 14:105:0.25:1.9:2.6; and the mass fraction of the ethanol solution was 20%;

[0036] S3. Place the organically modified carbon nanotubes in deionized water and mix them evenly. Then, add zinc nitrate and rotate at 900 r / min for 35 minutes. Let it stand for 3.5 hours. Add ammonia water and keep it at a constant temperature of 170°C for 1.1 hours. After cooling to room temperature, filter it and dry it at 80°C to constant weight to obtain composite modified carbon nanotubes. The usage ratio of the organically modified carbon nanotubes, deionized water, zinc nitrate and ammonia water is 20.5:65:5.6:8.5. The mass fraction of the ammonia water is 28%.

[0037] A preparation method for a high-temperature resistant silicone rubber seal comprises the following steps: heating a kneader to 110°C, adding vinyl silicone rubber, modified silica, composite modified carbon nanotubes, methyl silicone oil, an antioxidant and an initiator, kneading for 16 minutes, and then vulcanizing on a flat vulcanizer at 240°C for 9 minutes to obtain the seal.

[0038] Example 3

[0039] A high-temperature resistant silicone rubber seal comprises the following components by weight: 58 parts of vinyl silicone rubber, 12 parts of modified silicon dioxide, 18 parts of composite modified carbon nanotubes, 3.1 parts of methyl silicone oil, 0.8 parts of antioxidant, and 1.2 parts of initiator; the initiator is initiator DHBP; the vinyl silicone rubber has a vinyl content of 2%; the antioxidant is a mixture of antioxidant 1010 and antioxidant 1076 in a mass ratio of 1.8:2.2;

[0040] The modified silica is prepared by reacting 12 parts by weight of fumed silica, 40 parts by weight of ethanol and 4 parts by weight of vinyltrimethoxysilane at 60°C for 3 hours, filtering out the reacted silica, washing the reacted silica with ethanol three times and drying the reacted silica at 90°C to a constant weight.

[0041] The method for preparing the composite modified carbon nanotubes comprises the following steps:

[0042] S1. Carboxyl carbon nanotubes (model XFD06, item number: 100227, Jiangsu Xianfeng Nanomaterial Technology Co., Ltd.) were placed in anhydrous ethanol and ultrasonicated at 400 W power for 40 minutes. A silane coupling agent was added and stirred at 72° C. for 1.5 hours. The mixture was filtered and dried at 80° C. to constant weight to obtain prefabricated carbon nanotubes. The drying step was as follows: the mass ratio of the carboxyl carbon nanotubes, anhydrous ethanol, and silane coupling agent was 18:50:3; and the silane coupling agent was vinyltriethoxysilane.

[0043] S2. Prefabricated carbon nanotubes were placed in an ethanol solution and mixed, and then the temperature was raised to 50°C at a rate of 4°C / min. Acetic acid and chitosan were added, and the mixture was ultrasonicated at 1200 W for 30 minutes. 4-mercaptobenzaldehyde was added and stirred at 60°C for 6 hours. The solid layer was removed by centrifugation, washed, and dried to obtain organically modified carbon nanotubes; the mass ratio of the prefabricated carbon nanotubes, ethanol solution, acetic acid, chitosan, and 4-mercaptobenzaldehyde was 15:110:0.3:2.0:2.8; and the mass fraction of the ethanol solution was 20%;

[0044] S3. Place the organically modified carbon nanotubes in deionized water and mix them evenly. Then, add zinc nitrate and rotate at 1000 r / min for 40 minutes. Let it stand for 4 hours. Then add ammonia water and keep the temperature at 180°C for 1.2 hours. After cooling to room temperature, filter and dry at 80°C to constant weight to obtain composite modified carbon nanotubes. The usage ratio of the organically modified carbon nanotubes, deionized water, zinc nitrate and ammonia water is 21:70:6.0:9. The mass fraction of the ammonia water is 28%.

[0045] A preparation method for a high-temperature resistant silicone rubber seal comprises the following steps: heating a kneader to 110°C, adding vinyl silicone rubber, modified silica, composite modified carbon nanotubes, methyl silicone oil, an antioxidant and an initiator, kneading for 18 minutes, and then vulcanizing on a flat vulcanizer at 240°C for 10 minutes to obtain the seal.

[0046] Comparative Example 1

[0047] Compared with Example 3, the difference in Comparative Example 1 is that the silane coupling agent in step S1 is silane coupling agent KH560, and the other components, preparation steps and parameters are the same.

[0048] Comparative Example 2

[0049] Compared with Example 3, Comparative Example 2 is different in that no silane coupling agent is used in step S1, and the remaining components, preparation steps and parameters are the same.

[0050] Comparative Example 3

[0051] Compared with Example 3, the difference in Comparative Example 3 is that chitosan is not used in step S2, and the other components, preparation steps and parameters are the same.

[0052] Comparative Example 4

[0053] Compared with Example 3, Comparative Example 4 is different in that benzaldehyde is used instead of 4-mercaptobenzaldehyde in step S2, and the other components, preparation steps and parameters are the same.

[0054] Comparative Example 5

[0055] Compared with Example 3, Comparative Example 5 is different in that 4-mercaptobenzaldehyde is not used in step S2, and the remaining components, preparation steps and parameters are the same.

[0056] Comparative Example 6

[0057] Compared with Example 3, Comparative Example 6 is different in that zinc nitrate is not used in step S3, and the remaining components, preparation steps and parameters are the same.

[0058] The sealing materials prepared in Examples 1-3 and Comparative Examples 1-6 were subjected to the following performance tests, and the test results are shown in Table 1.

[0059] Tensile strength test: according to GB / T528-2009;

[0060] High temperature resistance test: After conducting an aging resistance test (200°C, 72h) in accordance with GB / T3512-2014, the tensile strength is tested.

[0061] Table 1: Test results

[0062]

[0063]

[0064] From the test results in Table 1, it can be seen that, compared with Comparative Examples 1-6, the sealing material prepared in Examples 1-3 of the present invention has excellent tensile strength and high temperature resistance.

[0065] Through comparative analysis of Examples 1-3 and Comparative Examples 1-6 in conjunction with Table 1, it can be seen that this is because the silane coupling agent used in the present invention contains vinyl groups, which can increase the interfacial bonding strength of the carbon nanotubes in the vinyl silicone rubber system while also facilitating the entry of more chitosan into the layered structure of the carbon nanotubes. A covalent bond is then formed between chitosan and 4-mercaptobenzaldehyde, and the introduction of mercapto groups can adsorb zinc ions, promoting their entry into the interlayers of the carbon nanotubes and the pores of the organic material. Finally, zinc oxide particles are generated under a hydrothermal reaction with ammonia water, effectively filling the pores of the organically modified carbon nanotubes to form a denser structure, significantly improving the tensile strength and high temperature resistance of the sealing material.

[0066] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as a preferred embodiment as above, it is not intended to limit the present invention. Any person skilled in the art can make some changes or modifications to equivalent embodiments using the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any indirect modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A high temperature resistant silicone rubber seal, characterized in that: The composition comprises the following components by weight: 52-58 parts of vinyl silicone rubber, 8-12 parts of modified silicon dioxide, 14-18 parts of composite modified carbon nanotubes, 2.3-3.1 parts of methyl silicone oil, 0.5-0.8 parts of antioxidant and 0.8-1.2 parts of initiator; The method for preparing the composite modified carbon nanotubes comprises the following steps: S1, placing carboxyl carbon nanotubes in anhydrous ethanol and ultrasonically mixing, adding a silane coupling agent and stirring at a constant temperature, filtering, and drying to obtain prefabricated carbon nanotubes; S2, placing the prefabricated carbon nanotubes in an ethanol solution, mixing and preheating, adding acetic acid and chitosan, ultrasonically treating, adding 4-mercaptobenzaldehyde, heating and stirring, centrifuging, removing the lower layer of solids, washing, and drying to obtain organically modified carbon nanotubes; S3, adding organically modified carbon nanotubes to deionized water and mixing, adding zinc nitrate and stirring, allowing to stand, adding ammonia water and treating at a constant temperature, cooling to room temperature, filtering, and drying to obtain composite modified carbon nanotubes; The silane coupling agent is vinyltriethoxysilane.

2. A high temperature resistant silicone rubber seal according to claim 1, characterized in that: The modified silica is prepared by reacting 10-12 parts by weight of fumed silica, 35-40 parts by weight of ethanol and 3-4 parts by weight of vinyltrimethoxysilane at 60° C. for 3 hours, filtering out the reacted silica, washing the reacted silica with ethanol three times and drying the reacted silica at 90° C. to a constant weight.

3. The high temperature resistant silicone rubber seal according to claim 1, characterized in that: The antioxidant is prepared by mixing antioxidant 1010 and antioxidant 1076 in a mass ratio of 1.5-1.8:2.0-2.

2.

4. The high temperature resistant silicone rubber seal according to claim 1, characterized in that: The vinyl content of the vinyl silicone rubber is 2%.

5. The high temperature resistant silicone rubber seal according to claim 1, characterized in that: The initiator is initiator DHBP.

6. The high temperature resistant silicone rubber seal according to claim 1, characterized in that: In step S1, the ultrasonic mixing is performed at a power of 300-400 W for 30-40 minutes; the constant temperature stirring is performed at 68-72° C. for 1.0-1.5 hours; the drying is performed at 80° C. to constant weight; and the mass ratio of the carboxyl carbon nanotubes, anhydrous ethanol, and silane coupling agent is 15-18:40-50:2-3.

7. The high temperature resistant silicone rubber seal according to claim 1, characterized in that: In step S2, the ultrasonic treatment is performed at a power of 1000-1200 W for 20-30 minutes; the preheating is performed at a rate of 3-4°C / min to a temperature of 50°C; the heating and stirring is performed at a temperature of 50-60°C for 5-6 hours; the mass ratio of the prefabricated carbon nanotubes, ethanol solution, acetic acid, chitosan and 4-mercaptobenzaldehyde is 13-15:100-110:0.2-0.3:1.8-2.0:2.5-2.8; and the mass fraction of the ethanol solution is 20%.

8. The high temperature resistant silicone rubber seal according to claim 1, characterized in that: In step S3, the stirring and mixing is carried out at a speed of 800-1000 r / min for 30-40 minutes; the standing time is 3-4 hours; the constant temperature treatment is carried out at a constant temperature of 160-180° C. for 1-1.2 hours; and the drying is carried out at a temperature of 80° C. to constant weight.

9. The high temperature resistant silicone rubber seal according to claim 8, characterized in that: The usage ratio of the organic modified carbon nanotubes, deionized water, zinc nitrate and ammonia water is 20-21:60-70:5.2-6.0:8-9; the mass fraction of the ammonia water is 28%.

10. A method for preparing a high temperature resistant silicone rubber seal according to any one of claims 1 to 9, characterized in that: The preparation method comprises the following steps: heating a kneader to 110° C., adding vinyl silicone rubber, modified silica, composite modified carbon nanotubes, methyl silicone oil, antioxidant and initiator, kneading for 15-18 minutes, and vulcanizing on a flat vulcanizer at 240° C. for 8-10 minutes to obtain the product.

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