High-temperature-resistant silicone rubber sealing element and preparation method thereof

Abstract

The invention relates to a high-temperature-resistant silicone rubber sealing element and a preparation method thereof, and belongs to the technical field of sealing element materials. The high-temperature-resistant silicone rubber sealing element comprises the following components: vinyl silicone rubber, modified silicon dioxide, composite modified carbon nanotubes, methyl silicone oil, an antioxidant and an initiator. The vinyl silane coupling agent, the chitosan, the mercaptobenzaldehyde and the zinc oxide are adopted to modify the carbon nanotubes, so that the sealing element material forms a more compact structure, and the tensile strength and the high temperature resistance of the sealing element material are remarkably improved.

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 type of widely used general-purpose basic components. They are widely used in various sealing mechanical equipment due to their unique physical properties, such as small elastic modulus, high elongation, and excellent air permeability. Standard silicone rubber material has good heat resistance and can operate continuously in an environment of 180°C. Even if the temperature is slightly over 200°C, it can maintain its elasticity for several weeks. In addition, it can withstand high temperatures of over 300°C instantly. However, with the advancement of technology, the existing heat resistance of silicone rubber can no longer meet the high standards required by certain specific industries or temperature-resistant equipment.

[0003] With the continuous progress and expansion of industrial production, more and more sealing machinery and equipment need to operate for a long time in harsh outdoor environments, which undoubtedly puts forward more stringent requirements on the aging resistance of rubber seals. At present, the existing rubber seals on the market have certain defects in high temperature resistance, especially poor performance in high temperature thermal aging resistance, which greatly limits the application scope of sealing machinery and equipment and has a negative impact on the service life of the equipment.

[0004] Carbon nanotubes show great potential in improving the high-temperature performance of silicone rubber seals, but their application also faces some challenges. First, the dispersion problem of carbon nanotubes is a major obstacle. Due to the extremely high aspect ratio and strong van der Waals force of carbon nanotubes, they tend to aggregate in the silicone rubber matrix to form agglomerates, which will reduce the mechanical properties and heat resistance of the composite material. Secondly, the interfacial compatibility between carbon nanotubes and the silicone rubber matrix is ​​also an issue that needs to be addressed. If the interface bonding is not strong, then the carbon nanotubes may fall off from the matrix during high temperature or long-term use, resulting in a decrease in the performance of the seal. Summary of the invention

[0005] The object 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, thereby significantly improving the tensile strength and high temperature resistance of the seal material.

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

[0007] A high temperature resistant silicone rubber seal 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.

[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 to constant weight at 90°C.

[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 and removing the lower layer of solids, washing, and drying to obtain organically modified carbon nanotubes;

[0014] S3, placing the organic modified carbon nanotubes in 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.

[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 30-40min; the constant temperature stirring is stirring at 68-72°C for 1.0-1.5h; 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 vinyl triethoxysilane.

[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 20-30min; 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 5-6h; 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; 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 min; the standing time is 3-4 h; the constant temperature treatment is carried out at a constant temperature of 160-180°C for 1-1.2 h; the drying is carried out at a temperature of 80°C to constant weight; the dosage 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; 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 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 invention purpose, 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 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 at a mass ratio of 1.5:2.0;

[0024] The modified silica is obtained 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, washing with ethanol three times, and drying at 90°C to constant weight;

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

[0026] S1. Place carboxyl carbon nanotubes (model XFD06, item number: 100227, Jiangsu Xianfeng Nanomaterial Technology Co., Ltd.) in anhydrous ethanol and ultrasonicate for 30 min at 300 W power, add silane coupling agent and stir at 68 ° C for 1.0 h, filter, and dry at 80 ° C to constant weight to obtain prefabricated carbon nanotubes; the drying is: the mass ratio of the carboxyl carbon nanotubes, anhydrous ethanol and silane coupling agent is 15:40:2; the silane coupling agent is vinyl triethoxysilane;

[0027] S2, placing the prefabricated carbon nanotubes in an ethanol solution and mixing, then heating to 50°C at a rate of 3°C / min, adding acetic acid and chitosan, ultrasonicating at 1000W for 20min, adding 4-mercaptobenzaldehyde, stirring at 50°C for 5h, centrifuging to remove the lower layer of solid matter, washing, and drying to obtain organically modified carbon nanotubes; the mass ratio of the prefabricated carbon nanotubes, ethanol solution, acetic acid, chitosan and 4-mercaptobenzaldehyde is 13:100:0.2:1.8:2.5; the mass fraction of the ethanol solution is 20%;

[0028] S3. Place the organic modified carbon nanotubes in deionized water and mix well, then add zinc nitrate at a speed of 800 r / min for 30 minutes, let it stand for 3 hours, add ammonia water and keep it at a constant temperature of 160°C for 1 hour, cool to room temperature, filter, and dry at 80°C to constant weight to obtain composite modified carbon nanotubes; the dosage ratio of the organic 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 of a high-temperature resistant silicone rubber seal comprises the following steps: heating a kneading machine 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 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 obtained 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, washing with ethanol three times, and drying at 90°C to constant weight;

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

[0034] S1. Place carboxyl carbon nanotubes (model XFD06, item number: 100227, Jiangsu Xianfeng Nanomaterial Technology Co., Ltd.) in anhydrous ethanol and ultrasonicate for 35 minutes at a power of 350W, add silane coupling agent and stir at 70°C for 1.2 hours, filter, and dry at 80°C to constant weight to obtain prefabricated carbon nanotubes; the drying is: the mass ratio of the carboxyl carbon nanotubes, anhydrous ethanol and silane coupling agent is 16:45:2.5; the silane coupling agent is vinyl triethoxysilane;

[0035] S2. Place the prefabricated carbon nanotubes in an ethanol solution and mix well, then heat the solution to 50°C at a rate of 3.5°C / min, add acetic acid and chitosan, ultrasonicate at 1100W for 25min, add 4-mercaptobenzaldehyde, stir at 55°C for 5.5h, centrifuge to remove the solid layer, wash, and dry to obtain organically modified carbon nanotubes; the mass ratio of the prefabricated carbon nanotubes, ethanol solution, acetic acid, chitosan and 4-mercaptobenzaldehyde is 14:105:0.25:1.9:2.6; the mass fraction of the ethanol solution is 20%;

[0036] S3. Place the organic modified carbon nanotubes in deionized water and mix well, then add zinc nitrate at a speed of 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, cool to room temperature, filter, and dry at 80°C to constant weight to obtain composite modified carbon nanotubes; the dosage ratio of the organic 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 of a high-temperature resistant silicone rubber seal comprises the following steps: heating a kneading machine 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 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 content of the vinyl silicone rubber is 2%; the antioxidant is a mixture of antioxidant 1010 and antioxidant 1076 in a mass ratio of 1.8:2.2;

[0040] The modified silica is obtained 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, washing with ethanol three times, and drying at 90°C to constant weight;

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

[0042] S1. Place carboxyl carbon nanotubes (model XFD06, item number: 100227, Jiangsu Xianfeng Nanomaterial Technology Co., Ltd.) in anhydrous ethanol and ultrasonicate for 40 min at 400 W power, add silane coupling agent and stir at 72 ° C for 1.5 h, filter, and dry at 80 ° C to constant weight to obtain prefabricated carbon nanotubes; the drying is: the mass ratio of the carboxyl carbon nanotubes, anhydrous ethanol and silane coupling agent is 18:50:3; the silane coupling agent is vinyl triethoxysilane;

[0043] S2, placing the prefabricated carbon nanotubes in an ethanol solution and mixing, then heating to 50°C at a rate of 4°C / min, adding acetic acid and chitosan, ultrasonicating at 1200W for 30min, adding 4-mercaptobenzaldehyde, stirring at 60°C for 6h, centrifuging to remove the lower layer of solid matter, washing, and drying to obtain organically modified carbon nanotubes; the mass ratio of the prefabricated carbon nanotubes, ethanol solution, acetic acid, chitosan and 4-mercaptobenzaldehyde is 15:110:0.3:2.0:2.8; the mass fraction of the ethanol solution is 20%;

[0044] S3. Place the organic modified carbon nanotubes in deionized water and mix well, then add zinc nitrate at a speed of 1000 r / min for 40 minutes, let it stand for 4 hours, add ammonia water and keep it at a constant temperature of 180°C for 1.2 hours, cool to room temperature, filter, and dry at 80°C to constant weight to obtain composite modified carbon nanotubes; the dosage ratio of the organic 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 of a high-temperature resistant silicone rubber seal comprises the following steps: heating a kneading machine 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 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, the difference in Comparative Example 2 is that no silane coupling agent is used in step S1, and the other 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, the difference in Comparative Example 5 is that step S2 does not use 4-mercaptobenzaldehyde, 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 obtained from Examples 1-3 and Comparative Examples 1-6 were subjected to the following performance tests, respectively. 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) according to 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 combination with Table 1, it can be seen that this is because the silane coupling agent used in the present invention contains vinyl groups that can increase the interfacial bonding strength of the carbon nanotubes in the vinyl silicone rubber system, while also facilitating more chitosan to enter the layered structure of the carbon nanotubes. Then, a covalent bond is 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 the hydrothermal reaction of ammonia water, which effectively fills the pores of the organically modified carbon nanotubes to form a denser structure, thereby significantly improving the tensile strength and high temperature resistance of the sealing material.

[0066] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technical personnel in this field can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any indirect modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall 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 and removing the lower layer of solids, washing, and drying to obtain organically modified carbon nanotubes; S3, placing the organic modified carbon nanotubes in 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.

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, washing with ethanol for 3 times and drying at 90° C. to 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; 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 vinyl triethoxysilane.

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 min; 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 h; 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 min; the standing time is 3-4 h; the constant temperature treatment is carried out at a constant temperature of 160-180° C. for 1-1.2 h; and the drying is carried out at a temperature of 80° C. to constant weight.

9. A high temperature resistant silicone rubber seal according to claim 8, characterized in that: The dosage ratio of the organic modified carbon nanotube, 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 silicon dioxide, 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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