High-temperature-resistant leakproof sealing gasket and preparation method thereof

Abstract

The invention discloses a high-temperature-resistant leakproof sealing gasket and a preparation method thereof. The high-temperature-resistant leakproof sealing gasket is prepared from the following raw materials in parts by weight: 100 parts of nitrile rubber; 26-39 parts of a vermiculite-based composite filler; 2-7 parts of zinc oxide; 3-8 parts of paraffin oil; 2.5 to 9 parts of white carbon black; 1-6 parts of a vulcanizing agent; 0.8 to 2.4 parts of stearic acid; and 0.5 to 1.7 parts of a vulcanization accelerator. The expanded vermiculite-based multi-component composite filler with a special structure system is prepared, and the vermiculite-based composite filler and the nitrile rubber are compounded for use, so that the high-temperature resistance and thermo-oxidative aging resistance of the nitrile rubber can be remarkably improved, and meanwhile, the sealing performance of the nitrile rubber can be improved; the comprehensive performance of the prepared sealing gasket is remarkably improved, and the sealing requirement in the high-temperature environment can be better met.

Description

Technical Field

[0001] The present invention relates to the field of sealing materials, and in particular to a high-temperature resistant and leak-proof sealing gasket and a preparation method thereof. Background Art

[0002] Sealing gaskets are widely used in modern industry to seal various equipment. They can be divided into metal sealing gaskets and non-metallic sealing gaskets according to their material. Rubber gaskets are a typical non-metallic sealing gasket. They are widely used due to their long service life and good sealing effect.

[0003] The rapid development of the industrial sector has placed higher demands on the performance of sealing gaskets. For example, sealing gaskets used in heat exchange and heating equipment can experience long-term operating temperatures exceeding 100°C, with intermittent operating temperatures potentially reaching 150°C. This poses a challenge to the high-temperature resistance of sealing gaskets. Conventional rubber gaskets often struggle to meet the demands of long-term use in high-temperature environments, or they age faster when used in high-temperature environments, significantly shortening their service life.

[0004] Patent CN118374036A discloses a high-performance composite sealing gasket and its preparation method, which are the applicant's previous research results. By compounding reduced carbon dots, modified multi-walled carbon nanotubes, modified carbon fibers, etc. to prepare anti-aging enhanced modified composite particles, it can give the sealing gasket system excellent antioxidant properties, thereby improving the anti-aging effect; however, the carbon nanotubes and other materials used therein are relatively expensive, and their resistance to heat and oxygen aging needs to be further improved.

[0005] Vermiculite is a cheap lamellar silicate mineral with stable chemical properties and excellent properties such as thermal insulation, heat insulation, sound insulation, antibacterial, and cold resistance. When heated, the vermiculite expands due to the evaporation of water in the structure. The expanded vermiculite has a low bulk density, stable chemical properties, and excellent heat resistance, heat insulation, wear resistance, and corrosion resistance (Qian Yupeng, Jiang Xuefeng, He Yicheng, et al. Preparation of high expansion rate expanded vermiculite by composite method [J]. Bulletin of Silicates, 2017, 36(9):5. DOI:CNKI:SUN:GSYT.0.2017-09-001.). Expanded vermiculite is used as a reinforcing filler in rubber systems, or further used in sealing materials. For example, patent CN107188453B discloses a method for preparing a vermiculite-based high-temperature-resistant sealing material, and patent CN115650632B discloses a method for preparing a high-temperature-resistant vermiculite-based composite sealing gasket. Therefore, the use of expanded vermiculite in rubber gasket materials is expected to improve their heat resistance and reduce their cost. However, expanded vermiculite has poor compatibility with rubber systems and is also prone to brittleness and pulverization. These patents do not effectively address this issue.

[0006] Therefore, it is necessary to improve the existing technology to provide a more reliable solution. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a high temperature resistant and leakproof sealing gasket and a preparation method thereof in view of the deficiencies in the above-mentioned prior art.

[0008] In order to solve the above technical problems, the technical solution adopted by the present invention is as follows: In a first aspect of the present invention, a high-temperature resistant and leak-proof sealing gasket is provided, and the raw materials for preparing the same include the following components in parts by weight:

[0009]

[0010] The vermiculite-based composite filler is prepared by the following method:

[0011] S1. Preparation of composite modified vermiculite: performing in-situ graphene growth, carbon dot deposition, organic treatment, and polymer resin intercalation treatment on expanded vermiculite to obtain composite modified vermiculite;

[0012] S2, glass fiber pretreatment;

[0013] S3. The pretreated glass fiber is coated with composite modified vermiculite to obtain a vermiculite-based composite filler.

[0014] Preferably, step S1 specifically includes:

[0015] S1-1. In-situ growth of graphene:

[0016] Expanded vermiculite, copper chloride, and ruthenium trichloride are added to a citric acid aqueous solution, ultrasonically treated, and heated and evaporated to dryness; the resulting product is pretreated under a hydrogen atmosphere and heated, and then heated to react in a mixed gas consisting of argon, ethylene, and hydrogen. After the reaction is completed, the mixture is cooled to obtain graphene-composite expanded vermiculite;

[0017] S1-2, carbon dot deposition:

[0018] Graphene-composite expanded vermiculite, citric acid, and mercaptopropionic acid are added to a mixed solution of ethanol and deionized water, stirred, and then glucose and 1,2-cyclohexanediamine are added, ultrasonically dispersed, and the resulting mixture is transferred to a reactor, heated for hydrothermal reaction, cooled after the reaction, centrifuged, filtered, and the solid product is washed and vacuum dried to obtain loaded vermiculite;

[0019] S1-3, organic treatment:

[0020] Adding loaded vermiculite and hexadecyltrimethylammonium bromide to deionized water, stirring, filtering, washing the solid product, and drying to obtain organic vermiculite;

[0021] S1-4, polymer resin intercalation treatment:

[0022] Take EPDM rubber and maleic anhydride and add them to xylene. Stir under heating. Keep stirring and dropwise add the xylene solution containing benzoyl peroxide. After the addition is complete, react to obtain a polymer resin solution.

[0023] The organic vermiculite and butyl rubber are added to the polymer resin solution, and the mixture is stirred and refluxed under heating. After the reaction is completed, the mixture is filtered, the solid product is washed, and vacuum dried to obtain the composite modified vermiculite.

[0024] Preferably, step S1 specifically includes:

[0025] S1-1. In-situ growth of graphene:

[0026] 0.5-2 g of expanded vermiculite, 0.033-0.134 g of copper chloride, and 0.026-0.104 g of ruthenium trichloride are added to 50-200 mL of a 2.5-10% citric acid aqueous solution, ultrasonically treated for 15-60 minutes, and heated to dryness at 120-150° C.; the resulting product is transferred to a tube furnace, pretreated at 750-900° C. in a hydrogen atmosphere for 5-20 minutes, then kept at 880-1000° C. in a mixed gas atmosphere of argon:ethylene:hydrogen in a volume ratio of 2:2:1 for 15-60 minutes, and cooled to room temperature to obtain graphene-composite expanded vermiculite;

[0027] S1-2, carbon dot deposition:

[0028] 1-4 g of graphene-composite expanded vermiculite, 0.42-1.90 g of citric acid, and 0.21-0.84 g of mercaptopropionic acid are added to a mixed solution consisting of 30-120 mL of ethanol and 20-80 mL of deionized water, and the mixture is stirred under sealing for 5-30 min. 0.24-0.96 g of glucose and 0.06-0.24 g of 1,2-cyclohexanediamine are then added, and ultrasonic dispersion is performed under sealing for 10-40 min. The resulting mixture is transferred to a reactor, hydrothermally reacted at 180-230° C. for 4-16 h, cooled to room temperature, centrifuged, and the solid product is washed with ethanol and deionized water in sequence, and vacuum dried at 70-100° C. for 6-24 h to obtain supported vermiculite;

[0029] S1-3, organic treatment:

[0030] Take 0.5-2g of loaded vermiculite and 0.1-0.4g of hexadecyltrimethylammonium bromide and add them to 50-200mL of deionized water, stir for 1-4h, filter, wash the solid product with deionized water, and dry it to constant weight to obtain organic vermiculite;

[0031] S1-4, polymer resin intercalation treatment:

[0032] Take 0.25-1g of EPDM rubber and 0.025-0.1g of maleic anhydride and add them to 45-180mL of xylene. Stir at 90-110°C for 5-30min. Keep stirring and add 2.5-20mL of xylene solution containing 3-12mg of benzoyl peroxide dropwise within 10-30min. Then react for 1-4h to obtain a polymer resin solution.

[0033] 0.5-2g of organic vermiculite and 0.1-0.4g of butyl rubber are added to the polymer resin solution, stirred and refluxed at 60-80°C for 12-48h, filtered, and the solid product is washed with acetone and ethanol in sequence, and vacuum dried to constant weight to obtain composite modified vermiculite.

[0034] Preferably, the expanded vermiculite is prepared by the following method: soaking the vermiculite in hydrogen peroxide with a mass concentration of 5-20% for 2-8 hours, controlling the solid-liquid ratio to be 1:2-7, taking out the soaked vermiculite, calcining it at 400-500°C for 1-5 minutes, cooling it to room temperature, and ball milling it to a particle size of less than 0.5-5 μm to obtain the expanded vermiculite.

[0035] Preferably, step S2 specifically comprises: soaking the glass fiber in hydrochloric acid under heating, filtering, washing with deionized water until neutral, and vacuum drying to constant weight to obtain pretreated glass fiber.

[0036] Preferably, step S2 is specifically as follows: soaking the glass fiber in 0.5-2 mol / L hydrochloric acid at 40-50° C. for 15-90 min, filtering, washing with deionized water until neutral, and vacuum drying at 90-120° C. to constant weight to obtain pretreated glass fiber.

[0037] Preferably, step S3 is specifically:

[0038] S3-1, adding the composite modified vermiculite to a mixture of ethanol and deionized water, and dispersing the mixture by ultrasonication to obtain a vermiculite dispersion;

[0039] S3-2. Add pretreated glass fiber to the vermiculite dispersion, disperse it by ultrasonication, then stir it under heating, increase the temperature, and stir until it is evaporated to dryness. After rinsing the obtained product, vacuum dry it to constant weight to obtain a vermiculite-based composite filler.

[0040] Preferably, step S3 is specifically:

[0041] S3-1. Take 0.5-2 g of the composite modified vermiculite and add it to 50-200 mL of a mixture of ethanol and deionized water in a volume ratio of 1:1, and ultrasonically disperse it for 15-60 minutes to obtain a vermiculite dispersion;

[0042] S3-2. Add 0.25-0.1 g of pretreated glass fiber to the vermiculite dispersion, ultrasonically disperse for 15-60 minutes, then stir at 50-85°C for 1-4 hours, heat to 95-105°C, and stir until evaporated to dryness. The resulting product is rinsed with deionized water and vacuum dried at 70-100°C to constant weight to obtain a vermiculite-based composite filler.

[0043] Preferably, the vulcanizing agent is selected from at least one of the vulcanizing agents DCP, BIPB or DBPH;

[0044] The vulcanization accelerator is at least one of vulcanization accelerator TMTD, vulcanization accelerator ZBX, vulcanization accelerator ZDMC, vulcanization accelerator NA-22, and vulcanization accelerator CZ.

[0045] A first aspect of the present invention provides a method for preparing the high-temperature resistant and leak-proof sealing gasket as described above, comprising the following steps:

[0046] 1) Banburying: Add nitrile rubber, vermiculite-based composite filler, zinc oxide, white carbon black, and stearic acid into a banbury mixer and mix at 75-95° C. for 2-10 min to obtain a banburying rubber compound;

[0047] 2) Open mixing: Add the mixed rubber material, vulcanizing agent, paraffin oil and vulcanization accelerator into the open mixing mill, mix at 55-78°C for 5-25 minutes, discharge the material, place it in the injection molding machine and press it into sheets to obtain the raw rubber gasket;

[0048] 3) Vulcanization: vulcanizing the raw rubber gasket in a vulcanizer at 160-190° C. for 12-50 min and a vulcanization pressure of 5-25 MPa to obtain the high-temperature resistant and leak-proof sealing gasket.

[0049] The beneficial effects of the present invention are:

[0050] The present invention provides a high-temperature resistant and leak-proof sealing gasket and a preparation method thereof. By preparing a multi-component composite filler with a special structural system based on expanded vermiculite, the vermiculite-based composite filler is compounded with nitrile rubber to significantly improve the high-temperature resistance and heat-oxidation aging resistance of the nitrile rubber, and at the same time improve its sealing performance, so that the comprehensive performance of the prepared sealing gasket is significantly improved, and the sealing requirements in high-temperature environments can be better met.

[0051] Vermiculite can significantly improve the heat resistance of the nitrile rubber matrix and further improve its wear resistance and corrosion resistance, but it has the defects of being brittle and easily pulverized. Graphene can improve various properties of rubber, but it has the defects of being easy to curl, easily agglomerate, and difficult to disperse in organic systems. Glass fiber has strong heat resistance, good corrosion resistance, and high mechanical strength, and can improve the mechanical properties and high-temperature resistance of rubber, but it has the disadvantages of poor compatibility with organic systems, brittleness, and poor wear resistance. In the vermiculite-based composite filler structure system prepared by the present invention, through the design of a special composite structure system, multi-components such as vermiculite, graphene, and glass fiber are organically combined, which can effectively overcome the above-mentioned shortcomings, give full play to the reinforcing effect of each component, and further, through the mutual cooperation of each component, can also play a complementary and enhanced role. In addition, the introduction of carbon dots in the system also gives the system an excellent antioxidant effect.

[0052] In the vermiculite-based composite filler structural system of the present invention, graphene grows in situ on the vermiculite surface and between its layers. The graphene, which has excellent mechanical strength, forms a network-like structure that covers the vermiculite, significantly improving the brittleness of the vermiculite and preventing it from pulverizing. The oxides formed by Cu and Ru can serve as stress nodes in the network structure, further improving its strength. On the other hand, the unique zero-bandgap structure of graphene allows both electrons and holes to move freely within it. The combination of graphene with carbon dots can help increase the electron transmission rate and promote the enhancement of the reducibility of the carbon dots.

[0053] In the vermiculite-based composite filler structural system of the present invention, graphene is grown in situ on the surface of the vermiculite, thereby overcoming its inherent defect of being easily curled. Furthermore, the compatibility of the entire system with the resin is improved through polymer resin intercalation treatment, thereby simultaneously solving the problem of poor compatibility between vermiculite, graphene, glass fiber and the resin system.

[0054] In the vermiculite-based composite filler structure of the present invention, vermiculite easily forms a dense physical layer structure in the nitrile rubber system, thereby improving sealing performance. The vermiculite's lamellar structure enables it to be peeled off to form a flaky reinforcement structure when subjected to force or friction, which helps to improve its wear resistance. The network-like coating structure of graphene on the vermiculite can further improve the wear resistance and reduce the friction coefficient, thereby giving the prepared sealing gasket excellent wear resistance. It can also maintain its sealing performance for a long time in environments with high friction, is not easily worn, and can ensure reliability during long-term use. The advantages of vermiculite and graphene in this performance can also compensate for the wear resistance deficiency of glass fiber.

[0055] In the vermiculite-based composite filler structure system of the present invention, the introduction of reducing carbon dots gives the vermiculite-based composite filler structure system excellent antioxidant ability. Combined with the improvement of the high-temperature resistance of the system by vermiculite, graphene and glass fiber, the vermiculite-based composite filler has excellent resistance to heat and oxygen aging, thereby making up for the shortcomings of nitrile rubber in this aspect.

[0056] In the vermiculite-based composite filler structural system of the present invention, maleic anhydride-grafted EPDM rubber and butyl rubber are compounded as intercalated polymer resins. In addition to improving the film-forming ability of the vermiculite-based composite filler and its compatibility with the nitrile rubber matrix, the system also has the following functions: the maleic anhydride-grafted EPDM rubber has excellent heat resistance, ozone resistance, and weather resistance, and can improve the problems of butyl rubber such as poor high-temperature resistance and poor heat-oxidative aging resistance; the butyl rubber has excellent air tightness and water tightness, and can overcome the problems of insufficient air tightness and oil resistance of the EPDM rubber and nitrile rubber; therefore, the combination of the maleic anhydride-grafted EPDM rubber and butyl rubber also has a significant improvement effect on the comprehensive performance of the nitrile rubber matrix. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 The tensile strength test results of the embodiments and comparative examples are as follows;

[0058] Figure 2 Compression rebound test results of the examples and comparative examples;

[0059] Figure 3 The sealing performance test results of the embodiments and comparative examples are shown in FIG.

[0060] Figure 4 The following are the test results of high temperature resistance of the examples and comparative examples;

[0061] Figure 5 The heat-oxidation aging resistance test results of the examples and comparative examples are as follows;

[0062] Figure 6 The high temperature wear resistance test results of the embodiments and comparative examples are as follows;

[0063] Figure 7 is the infrared absorption spectrum of the loaded vermiculite prepared in Example 1;

[0064] Figure 8 These are the test results of the anti-oxidation properties of the vermiculite-based composite fillers prepared in Example 1 and Comparative Examples 1 to 3. DETAILED DESCRIPTION

[0065] The present invention is further described in detail below with reference to the embodiments so that those skilled in the art can implement the invention with reference to the description.

[0066] It should be understood that terms such as “having”, “including” and “comprising” used herein do not preclude the existence or addition of one or more other elements or combinations thereof.

[0067] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Materials and reagents used in the following examples are commercially available unless otherwise specified. In the following examples, where specific conditions are not specified, the experiments were conducted under conventional conditions or those recommended by the manufacturer. Reagents and instruments used, where the manufacturer is not specified, are commercially available conventional products.

[0068] The present invention provides a high-temperature resistant and leak-proof sealing gasket, the raw materials for preparing the same include the following components in parts by weight:

[0069]

[0070]

[0071] The preparation method of the high temperature resistant and leakproof sealing gasket comprises the following steps:

[0072] 1) Banburying: Add nitrile rubber, vermiculite-based composite filler, zinc oxide, white carbon black, and stearic acid into a banbury mixer and mix at 75-95° C. for 2-10 min to obtain a banburying rubber compound;

[0073] 2) Open mixing: Add the mixed rubber material, vulcanizing agent, paraffin oil and vulcanization accelerator into the open mixing mill, mix at 55-78°C for 5-25 minutes, discharge the material, place it in the injection molding machine and press it into sheets to obtain the raw rubber gasket;

[0074] 3) Vulcanization: vulcanize the raw rubber gasket in a vulcanizer at 160-190° C. for 12-50 min and a vulcanization pressure of 5-25 MPa to obtain a high-temperature resistant and leak-proof sealing gasket.

[0075] Wherein, the vermiculite-based composite filler is prepared by the following method:

[0076] S1. Preparation of composite modified vermiculite: In-situ growth of graphene, carbon dot deposition, organic treatment, and polymer resin intercalation treatment are performed on expanded vermiculite to obtain composite modified vermiculite; the specific steps include:

[0077] S1-1. In-situ growth of graphene:

[0078] 0.5-2 g of expanded vermiculite, 0.033-0.134 g of copper chloride, and 0.026-0.104 g of ruthenium trichloride are added to 50-200 mL of a 2.5-10% citric acid aqueous solution, ultrasonically treated for 15-60 minutes, and heated to dryness at 120-150° C.; the resulting product is transferred to a tube furnace, pretreated at 750-900° C. in a hydrogen atmosphere for 5-20 minutes, then kept at 880-1000° C. in a mixed gas atmosphere of argon:ethylene:hydrogen in a volume ratio of 2:2:1 for 15-60 minutes, and cooled to room temperature to obtain graphene-composite expanded vermiculite;

[0079] The expanded vermiculite is prepared by the following method: soaking the vermiculite in hydrogen peroxide with a mass concentration of 5-20% for 2-8 hours, controlling the solid-liquid ratio to be 1:2-7, taking out the soaked vermiculite, calcining it at 400-500°C for 1-5 minutes, cooling it to room temperature, and ball milling it to a particle size of less than 0.5-5 μm to obtain the expanded vermiculite.

[0080] S1-2, carbon dot deposition:

[0081] 1-4 g of graphene-composite expanded vermiculite, 0.42-1.90 g of citric acid, and 0.21-0.84 g of mercaptopropionic acid are added to a mixed solution consisting of 30-120 mL of ethanol and 20-80 mL of deionized water, and the mixture is stirred under sealing for 5-30 min. 0.24-0.96 g of glucose and 0.06-0.24 g of 1,2-cyclohexanediamine are then added, and ultrasonic dispersion is performed under sealing for 10-40 min. The resulting mixture is transferred to a reactor, hydrothermally reacted at 180-230° C. for 4-16 h, cooled to room temperature, centrifuged, and the solid product is washed with ethanol and deionized water in sequence, and vacuum dried at 70-100° C. for 6-24 h to obtain supported vermiculite;

[0082] S1-3, organic treatment:

[0083] Take 0.5-2g of loaded vermiculite and 0.1-0.4g of hexadecyltrimethylammonium bromide and add them to 50-200mL of deionized water, stir for 1-4h, filter, wash the solid product with deionized water, and dry it to constant weight to obtain organic vermiculite;

[0084] S1-4, polymer resin intercalation treatment:

[0085] 0.25-1 g of EPDM rubber and 0.025-0.1 g of maleic anhydride are added to 45-180 mL of xylene, and the mixture is stirred at 90-110° C. for 5-30 minutes. While stirring, 2.5-20 mL of a xylene solution containing 3-12 mg of benzoyl peroxide is added dropwise over 10-30 minutes, followed by reaction for 1-4 hours to obtain a polymer resin solution; the polymer resin solution is a maleic anhydride grafted EPDM rubber (EPDM-g-MAH) solution;

[0086] 0.5-2g of organic vermiculite and 0.1-0.4g of butyl rubber are added to the polymer resin solution, stirred and refluxed at 60-80°C for 12-48h, filtered, and the solid product is washed with acetone and ethanol in sequence, and vacuum dried to constant weight to obtain composite modified vermiculite.

[0087] S2. Glass fiber pretreatment:

[0088] The glass fiber is soaked in hydrochloric acid with a concentration of 0.5-2 mol / L at 40-50° C. for 15-90 minutes, filtered, washed with deionized water until neutral, and vacuum dried at 90-120° C. to constant weight to obtain the pretreated glass fiber.

[0089] S3. Using composite modified vermiculite to coat the pretreated glass fiber to obtain a vermiculite-based composite filler:

[0090] S3-1. Take 0.5-2 g of the composite modified vermiculite and add it to 50-200 mL of a mixture of ethanol and deionized water in a volume ratio of 1:1, and ultrasonically disperse it for 15-60 minutes to obtain a vermiculite dispersion;

[0091] S3-2. Add 0.25-0.1 g of pretreated glass fiber to the vermiculite dispersion, ultrasonically disperse for 15-60 minutes, then stir at 50-85°C for 1-4 hours, heat to 95-105°C, stir until evaporated to dryness, and lightly rinse the resulting product with deionized water to remove the uncoated composite modified vermiculite on the surface, and then vacuum dry at 70-100°C to constant weight to obtain a vermiculite-based composite filler.

[0092] In a preferred embodiment, the vulcanizing agent is selected from at least one of the vulcanizing agents DCP, BIPB or DBPH.

[0093] In a preferred embodiment, the vulcanization accelerator is at least one of vulcanization accelerator TMTD, vulcanization accelerator ZBX, vulcanization accelerator ZDMC, vulcanization accelerator NA-22, and vulcanization accelerator CZ.

[0094] Acrylonitrile butadiene rubber has excellent oil resistance, wear resistance and strength, and is a commonly used material for the preparation of sealing rubber gaskets, but it has problems such as poor high temperature resistance and poor heat-oxidation aging resistance. In the present invention, a multi-component composite filler with a special structural system based on expanded vermiculite is prepared: the vermiculite-based composite filler is compounded with acrylonitrile butadiene rubber, which can significantly improve the high temperature resistance and heat-oxidation aging resistance of acrylonitrile butadiene rubber, and at the same time improve its sealing performance, so that the comprehensive performance of the prepared sealing gasket is significantly improved, and the sealing requirements under high temperature environments can be better met. The following will be combined with specific preparation steps to describe the mechanism of action of the vermiculite-based composite filler in detail for the convenience of understanding the present invention.

[0095] Vermiculite is a lamellar silicate mineral. When heated, the volume of vermiculite expands due to the evaporation of water in the structure. The expanded vermiculite has a low bulk density, stable chemical properties, and excellent heat resistance, heat insulation, wear resistance and corrosion resistance (Qian Yupeng, Jiang Xuefeng, He Yicheng, et al. Preparation of high expansion rate expanded vermiculite by composite method [J]. Bulletin of Silicates, 2017, 36(9): 5. DOI: CNKI: SUN: GSYT.0.2017-09-001.), (Jing Lvlu, Guo Fang, Jing Lvlu, et al. Tribological properties of organic vermiculite filled modified PBO fiber fabric gasket materials [J]. Lubrication and Sealing, 2014, 39(7): 6. DOI: 10.3969 / j.issn.0254-0150.2014.07.015.). The main preparation mechanism of the vermiculite-based composite filler in the present invention is as follows:

[0096] 1. Preparation of composite modified vermiculite:

[0097] (1) The present invention first prepares expanded vermiculite by combining hydrogen peroxide immersion with high-temperature heat treatment. The hydrogen peroxide immersion can remove some impurities in the vermiculite. In addition, the H2O2 molecules entering the vermiculite interlayer decompose at a subsequent high temperature to generate oxygen pressure that can promote the dissociation and expansion of the structural layer, thereby promoting the expansion and improving the expansion efficiency and treatment effect. The interlayer spacing of the expanded vermiculite increases, providing conditions for subsequent interlayer deposition of graphene and carbon dots and insertion of organic molecules, resin polymers, etc. Expanded vermiculite can also improve the sound insulation performance of the prepared sealing gasket.

[0098] (2) Then, using chemical vapor deposition and an in-situ growth method, graphene is loaded on the surface of vermiculite and between layers to obtain graphene-composite expanded vermiculite;

[0099] The specific method is: first load Cu on expanded vermiculite in a weakly acidic solution. 2+ and Ru 3+ Then, under the action of high temperature and reducing gas hydrogen, Cu2+ and Ru 3+ Generate elemental Cu and elemental Ru, both of which have catalytic effects on the chemical vapor deposition of graphene (Jin Yan, Yang Qian, Zhao Wenbin, et al. Research on catalytic reaction system for controllable preparation of graphene chemical vapor deposition method [J]. Journal of Chemical Industry and Engineering, 2020, 71(6): 22. DOI: 10.11949 / 0438-1157.20200107.), then use ethylene as carbon source, hydrogen as reducing gas, elemental Cu and Ru as composite catalysts (the two composites can achieve a synergistic enhancement effect), and in situ grow graphene on expanded vermiculite at high temperature. Since elemental Cu and Ru are uniformly loaded on the surface and interlayer of expanded vermiculite, they can promote full contact between the composite catalyst and the carbon source, promote the aggregation of carbon atoms in the gas phase into graphene structure, significantly improve its catalytic efficiency in promoting graphene growth, and increase the loading amount of graphene.

[0100] (3) Through hydrothermal reaction, carbon dots are synthesized in situ on expanded vermiculite. In this process, the graphene-composite expanded vermiculite is first mixed with citric acid and mercaptopropionic acid. In a weak acid solution, the elemental Cu in the graphene-composite expanded vermiculite can form a large amount of Cu 2+ , glucose, 1,2-cyclohexanediamine and other raw material precursors and Cu 2+ Through electrostatic adsorption, coordination and other combinations, and then through high-temperature hydrothermal reaction, a large number of uniformly loaded carbon dots are deposited on the graphene composite expanded vermiculite. 2+ The formation of oxides plays a connecting role and, together with Ru, also has a doping effect on the carbon dots. In this process, citric acid and mercaptopropionic acid are used to provide an acidic environment and, at the same time, participate in the subsequent synthesis of carbon dots as carbon sources and sulfur sources. Mercaptopropionic acid has good reducibility, and the prepared carbon dots inherit the reducibility of the precursor well, so that the prepared carbon dots have excellent antioxidant properties. The doping effect of Cu and Ru on the carbon dots can enhance the antioxidant properties of the carbon dots by increasing the electron cloud density and the electron transfer rate. Furthermore, the carbon dots exert their antioxidant effect by capturing the active oxygen in the system. Since the carbon dots have a large amount of load on the surface of the expanded vermiculite and between its layers and are stably connected to the expanded vermiculite, they will not exhibit phenomena such as free agglomeration or surface migration in the nitrile rubber system, and can exert stable antioxidant properties without affecting the mechanical strength of the nitrile rubber system. Moreover, the load of the carbon dots between the layers can make its antioxidant properties have the characteristics of long-lasting effect.

[0101] (4) The expanded vermiculite was then organically treated by hexadecyltrimethylammonium bromide, and finally maleic anhydride-grafted EPDM rubber and butyl rubber were intercalated by a solution method, so that a large amount of resin composite was grafted between the layers of the expanded vermiculite to obtain a composite modified vermiculite. The intercalation of the polymer resin can greatly improve the compatibility and interface connection strength between the expanded vermiculite and the nitrile rubber system, and at the same time can enhance the coating film-forming performance of the expanded vermiculite, which is beneficial to the subsequent coating treatment of the glass fiber. In this process, EPDM rubber is first grafted with maleic anhydride to obtain a polymer resin solution, namely a maleic anhydride grafted EPDM rubber resin (EPDM-g-MAH) solution. The maleic anhydride grafting treatment can toughen and expand the volume of EPDM rubber, improve its mechanical properties and compatibility with the nitrile rubber matrix; then, the expanded vermiculite is intercalated with butyl rubber and organic vermiculite in the solution under stirring and reflux.

[0102] 2. Composite modified vermiculite coating on glass fiber:

[0103] The glass fiber is first treated with acid immersion to increase surface roughness, increase fiber surface area, improve fiber-resin wettability and interfacial bonding strength, and form abundant silanol groups on the glass fiber surface. The acid-treated glass fiber is then dispersed in a vermiculite dispersion. Under heating and stirring, the solution gradually evaporates, and micron-sized composite modified vermiculite gradually precipitates on the glass fiber surface, coating it. Finally, a vermiculite-based composite filler is prepared. The polymer resin intercalated into the composite modified vermiculite effectively promotes film formation, improving coating efficiency and density. Furthermore, because the glass fiber surface is rich in silanol groups, the composite modified vermiculite forms a certain amount of copper ions on its surface in the mixed solution. The copper ions coordinate with the silanol groups, promoting this coating process.

[0104] Vermiculite can significantly improve the heat resistance of the nitrile rubber matrix and further improve its wear resistance and corrosion resistance, but it has the defects of being brittle and easily pulverized. Graphene can improve the various properties of rubber, but it has the defects of being easy to curl, easily agglomerate, and difficult to disperse in organic systems. Glass fiber has strong heat resistance, good corrosion resistance, and high mechanical strength, and can improve the mechanical properties and high temperature resistance of rubber, but it has the disadvantages of poor compatibility with organic systems and being brittle and having poor wear resistance. It can be seen that inorganic fillers such as vermiculite, graphene, and glass fiber can all play a reinforcing role in rubber in some aspects, but they inevitably have some shortcomings, which limit their application effects. The vermiculite-based composite filler system prepared by the present invention organically combines multiple components, such as vermiculite, graphene, and glass fiber, through the design of a special composite structure system. This effectively overcomes the above-mentioned shortcomings, fully utilizing the reinforcing effects of each component. Furthermore, through the mutual cooperation of each component, it can also play a complementary and reinforcing role. In addition, the introduction of carbon dots in the system also gives the system excellent antioxidant effects. The mechanism of the coordinated action of each component in the vermiculite-based composite filler is as follows:

[0105] (1) Graphene is a carbon atom with sp 2 The two-dimensional honeycomb carbon material with the six-membered ring formed by hybridization as the basic unit cell has excellent mechanical strength and high temperature resistance. Graphene grows in situ on the surface of vermiculite and between its layers. The graphene with excellent mechanical strength forms a network-like structure coated on the vermiculite, which can significantly improve the brittleness of the vermiculite and prevent it from pulverizing. The oxides formed by Cu and Ru can serve as stress nodes of the network structure, further improving its strength. On the other hand, the unique zero-bandgap structure of graphene allows both electrons and holes to move freely in it, and the electron mobility of graphene can reach about 200,000 cm 2 ·V -1 ·s -1 (Jin Yan, Yang Qian, Zhao Wenbin, et al. Research on catalytic reaction system prepared by controllable graphene chemical vapor deposition method [J]. Journal of Chemical Industry and Engineering, 2020, 71(6): 22. DOI: 10.11949 / 0438-1157.20200107.), its composite with carbon dots can help improve the electron transfer rate and promote the enhancement of the reducibility of carbon dots.

[0106] (2) Graphene has an ultra-high specific surface area and strength, which can significantly improve the tensile strength, tear strength, and wear resistance of the rubber matrix, and can also enhance air tightness and heat resistance. In this vermiculite-based composite filler structure system, because graphene is grown in situ on the vermiculite surface, it can overcome its inherent defect of being prone to curling. Further, through the polymer resin intercalation treatment, the compatibility of the entire system with the resin is improved, which can simultaneously solve the problem of poor compatibility between vermiculite, graphene, glass fiber and the resin system.

[0107] (3) Vermiculite easily forms a dense physical layer structure in the nitrile rubber system, thereby improving the sealing performance; the lamellar structure of vermiculite enables it to peel off when subjected to force or friction to form a lamellar reinforcement structure, which helps to improve its wear resistance; and the mesh coating structure of graphene on vermiculite can further improve the wear resistance and reduce the friction coefficient, thereby giving the prepared sealing gasket excellent wear resistance, allowing it to maintain its sealing performance for a long time in an environment with high friction, and not easily wear out, which can ensure reliability during long-term use. The advantages of vermiculite and graphene in this performance can also make up for the lack of wear resistance of glass fiber.

[0108] (3) The introduction of reducing carbon dots gives the vermiculite-based composite filler structure system excellent antioxidant ability. Combined with the improvement of the high temperature resistance of the system by vermiculite, graphene and glass fiber, the vermiculite-based composite filler has excellent resistance to heat and oxygen aging, thus making up for the shortcomings of nitrile rubber in this aspect.

[0109] (4) Maleic anhydride grafted EPDM rubber and butyl rubber are compounded as intercalated polymer resins. In addition to improving the film-forming ability of vermiculite-based composite fillers and their compatibility with the nitrile rubber matrix, they also have the following effects: Maleic anhydride grafted EPDM rubber has excellent heat resistance, ozone resistance, and weather resistance, which can improve the problems of butyl rubber such as poor high temperature resistance and poor heat-oxidative aging resistance; Butyl rubber has excellent air tightness and water tightness, which can overcome the problems of insufficient air tightness and oil resistance of EPDM rubber and nitrile rubber; Therefore, the combination of maleic anhydride grafted EPDM rubber and butyl rubber also has a significant improvement effect on the comprehensive performance of the nitrile rubber matrix.

[0110] Therefore, it can be seen that the mutual cooperation between the various components in the vermiculite-based composite filler structure system can significantly improve the comprehensive performance of the nitrile rubber matrix.

[0111] The above is the overall concept of the present invention. Detailed examples and comparative examples are provided below to further illustrate the present invention.

[0112] The main sources of raw materials involved in the following examples and comparative examples are as follows:

[0113] Nitrile rubber, JSRN220S, Shanghai Yiyong New Material Technology Co., Ltd.;

[0114] Zinc oxide, Jiangsu Xianfeng Nanomaterial Technology Co., Ltd.;

[0115] Paraffin oil, Nantong Runfeng Petrochemical Co., Ltd.;

[0116] Silica (M-5), Jiangsu Runfeng Synthetic Technology Co., Ltd.;

[0117] Stearic acid, Jiangsu Runfeng Synthetic Technology Co., Ltd.;

[0118] Curing agent DCP (dicumyl peroxide), Shanghai Bojing Chemical Co., Ltd.;

[0119] Vulcanization accelerator NA-22, Guangzhou Housheng New Materials Co., Ltd.;

[0120] Vermiculite, 325 mesh, Shijiazhuang Jinli Mining Co., Ltd.

[0121] Ethylene propylene diene monomer (EPDM), Dow 763P, was purchased from Suzhou Guoyao New Materials Co., Ltd.;

[0122] Maleic anhydride, Rongsheng New Materials Technology (Nantong, Jiangsu) Co., Ltd.;

[0123] Butyl rubber, brand: Japan JSR, purchased from Shanghai Ren En Import and Export Trading Co., Ltd.

[0124] Glass fiber, diameter 20 μm, length 3 mm, Jiangsu Jingshengyuan New Material Technology Co., Ltd.;

[0125] Graphene, product brand: JCSRGO, size: 0.06-0.12μm, specific surface area: 150-200m 2 / g; Suzhou Beike Nanotechnology Co., Ltd.

[0126] The remaining raw materials not specified are conventional commercially available products.

[0127] Example 1

[0128] A high-temperature resistant and leak-proof sealing gasket, the raw materials for its preparation include the following components in parts by weight:

[0129]

[0130]

[0131] The preparation method of the sealing gasket comprises the following steps:

[0132] 1) Banburying: adding nitrile rubber, vermiculite-based composite filler, zinc oxide, white carbon black, and stearic acid into a banbury mixer and mixing at 85° C. for 6 min to obtain a banburying rubber compound;

[0133] 2) Open mixing: Add the mixed rubber material, vulcanizing agent, paraffin oil and vulcanization accelerator into an open mixing mill, mix at 70°C for 12 minutes, discharge the material, place it in an injection molding machine and press it into sheets to obtain a raw rubber gasket;

[0134] 3) Vulcanization: vulcanize the raw rubber gasket in a vulcanizer at 180° C. for 23 min and a vulcanization pressure of 10 MPa to obtain a high-temperature resistant and leak-proof sealing gasket.

[0135] Wherein, the vermiculite-based composite filler is prepared by the following method:

[0136] S1. Preparation of composite modified vermiculite:

[0137] S1-1. In situ growth of graphene: 1 g of expanded vermiculite, 0.067 g of copper chloride, and 0.052 g of ruthenium trichloride were added to 100 mL of a 5% citric acid aqueous solution, ultrasonically treated for 30 minutes, and heated to dryness at 140°C; the resulting product was transferred to a tube furnace and pretreated at 850°C for 10 minutes in a hydrogen atmosphere, and then kept at 900°C for 30 minutes in a mixed gas atmosphere of argon:ethylene:hydrogen in a volume ratio of 2:2:1 to in situ grow graphene on the expanded vermiculite, and then cooled to room temperature to obtain graphene-composite expanded vermiculite;

[0138] The expanded vermiculite is prepared by soaking the vermiculite in 10% hydrogen peroxide for 4 hours at a solid-liquid ratio of 1:5, calcining the soaked vermiculite at 450° C. for 3 minutes, cooling to room temperature, and ball milling the vermiculite to a particle size of less than 1 μm to obtain the expanded vermiculite.

[0139] S1-2, carbon dot deposition: 2 g of graphene-composite expanded vermiculite, 0.85 g of citric acid, and 0.42 g of mercaptopropionic acid were added to a mixed solution consisting of 60 mL of ethanol and 40 mL of deionized water, and stirred under a sealed state for 15 min. 0.48 g of glucose and 0.12 g of 1,2-cyclohexanediamine were then added, and ultrasonic dispersion was performed under a sealed state for 20 min. The resulting mixture was transferred to a polytetrafluoroethylene-lined reactor, and hydrothermally reacted at 200° C. for 8 h. The mixture was cooled to room temperature and centrifuged. The solid product was washed with ethanol and deionized water in sequence, and vacuum dried at 80° C. for 12 h to obtain supported vermiculite.

[0140] S1-3, organic treatment: 1 g of loaded vermiculite and 0.2 g of hexadecyltrimethylammonium bromide were added to 100 mL of deionized water, stirred for 2 h, filtered, and the solid product was washed with deionized water until no bromide ions were detected in the washing liquid with 0.1 mol / L silver nitrate solution. The solid product was dried to constant weight to obtain organic vermiculite;

[0141] S1-4, polymer resin intercalation treatment: take 0.5g EPDM rubber and 0.05g maleic anhydride and add them to 90mL xylene, stir at 100℃ for 15min, keep stirring, add 10mL xylene solution containing 6mg benzoyl peroxide dropwise within 15min, and then react for 1.5h to obtain a polymer resin solution; take 1g organic vermiculite and 0.2g butyl rubber and add them to the polymer resin solution, stir and reflux at 70℃ for 24h, filter, wash the solid product with acetone and ethanol in turn, and vacuum dry to constant weight to obtain a composite modified vermiculite.

[0142] S2. Glass fiber pretreatment: soak the glass fiber in 1 mol / L hydrochloric acid at 45° C. for 45 min, filter, wash with deionized water until neutral, and vacuum dry at 100° C. to constant weight to obtain pretreated glass fiber.

[0143] S3. Using composite modified vermiculite to coat the pretreated glass fiber:

[0144] S3-1. 1 g of the composite modified vermiculite was added to 100 mL of a mixture of ethanol and deionized water in a volume ratio of 1:1, and ultrasonically dispersed for 30 min to obtain a vermiculite dispersion.

[0145] S3-2. Add 0.5 g of pretreated glass fiber to the vermiculite dispersion and ultrasonically disperse for 30 minutes. Then, stir at 70°C for 2 hours, heat to 100°C, and evaporate to dryness with stirring. The resulting product is rinsed with deionized water and vacuum-dried at 90°C to constant weight to obtain a vermiculite-based composite filler. The vermiculite-based composite filler weighs 1.32 g, and the glass fiber has gained 0.82 g, indicating that the composite-modified vermiculite has been extensively coated on the glass fiber.

[0146] Example 2

[0147] A high-temperature resistant and leak-proof sealing gasket, the raw materials for its preparation include the following components in parts by weight:

[0148]

[0149]

[0150] The rest is the same as in Example 1.

[0151] Example 3

[0152] A high-temperature resistant and leak-proof sealing gasket, the raw materials for its preparation include the following components in parts by weight:

[0153]

[0154] The preparation method of the sealing gasket comprises the following steps:

[0155] 1) Banburying: adding nitrile rubber, vermiculite-based composite filler, zinc oxide, white carbon black, and stearic acid into a banbury mixer and mixing at 90° C. for 5 min to obtain a banburying rubber compound;

[0156] 2) Open mixing: Add the mixed rubber material, vulcanizing agent, paraffin oil and vulcanization accelerator into an open mixing mill, mix at 70°C for 15 minutes, discharge the material, place it in an injection molding machine and press it into sheets to obtain a raw rubber gasket;

[0157] 3) Vulcanization: vulcanize the raw rubber gasket in a vulcanizer at 185° C. for 20 min and a vulcanization pressure of 10 MPa to obtain a high-temperature resistant and leak-proof sealing gasket.

[0158] The preparation method of the vermiculite-based composite filler is the same as that in Example 1.

[0159] Comparative Example 1

[0160] The only difference between this example and Example 1 is that:

[0161] The vermiculite-based composite filler in this example is prepared by the following method:

[0162] S1. Preparation of composite modified vermiculite:

[0163] S1-1. Preparation of expanded vermiculite: soaking vermiculite in 10% hydrogen peroxide for 4 h at a solid-liquid ratio of 1:5, calcining the soaked vermiculite at 450° C. for 3 min, cooling to room temperature, and ball-milling to a particle size of less than 1 μm to obtain expanded vermiculite;

[0164] S1-2, carbon dot deposition: Take 2g of expanded vermiculite, 0.85g of citric acid, and 0.42g of mercaptopropionic acid and add them to a mixed solution consisting of 60mL of ethanol and 40mL of deionized water, stir under sealing for 15min, then add 0.48g of glucose and 0.12g of 1,2-cyclohexanediamine, and ultrasonically disperse for 20min under sealing. The resulting mixture is transferred to a polytetrafluoroethylene-lined reactor, hydrothermally reacted at 200°C for 8h, cooled to room temperature, and centrifuged. The solid product is washed with ethanol and deionized water in sequence, and vacuum dried at 80°C for 12h to obtain loaded vermiculite.

[0165] The remaining steps are the same as in Example 1.

[0166] Comparative Example 2

[0167] The only difference between this example and Example 1 is that:

[0168] The vermiculite-based composite filler in this example is prepared by the following method:

[0169] S1. Preparation of composite modified vermiculite:

[0170] S1-1, in situ growth of graphene to obtain graphene-composite expanded vermiculite, the specific steps are the same as those in Example 1;

[0171] S1-2, organic treatment: take 1g of graphene composite expanded vermiculite and 0.2g of hexadecyltrimethylammonium bromide, add them to 100mL of deionized water, stir for 2h, filter, wash the solid product with deionized water until no bromide ions are detected in the washing liquid with 0.1mol / L silver nitrate solution, and dry to constant weight to obtain organic vermiculite;

[0172] S1-3, polymer resin intercalation treatment to obtain composite modified vermiculite, the specific steps are the same as step S1-4 of Example 1.

[0173] The remaining steps are the same as in Example 1.

[0174] Comparative Example 3

[0175] The only difference between this example and Example 1 is that:

[0176] The vermiculite-based composite filler in this example is prepared by the following method:

[0177] S1. Preparation of composite modified vermiculite:

[0178] S1-1. In-situ growth of graphene:

[0179] 1 g of expanded vermiculite and 0.067 g of copper chloride were added to 100 mL of a 5% citric acid aqueous solution, ultrasonically treated for 30 min, and heated to dryness at 140° C.; the resulting product was transferred to a tube furnace, pretreated at 850° C. for 10 min in a hydrogen atmosphere, and then kept at 900° C. for 30 min in a mixed gas atmosphere of argon:ethylene:hydrogen in a volume ratio of 2:2:1 to in situ grow graphene on the expanded vermiculite; the product was cooled to room temperature to obtain graphene-composite expanded vermiculite; the preparation method of the expanded vermiculite was the same as that in Example 1;

[0180] The remaining steps are the same as in Example 1.

[0181] Comparative Example 4

[0182] The only difference between this example and Example 1 is that:

[0183] In this example, the organic vermiculite in Example 1 was used instead of the composite modified vermiculite to coat the pretreated glass fiber.

[0184] Comparative Example 5

[0185] The only difference between this example and Example 1 is that:

[0186] Steps S1-4 in this example are specifically as follows:

[0187] 0.5 g of EPDM rubber and 0.05 g of maleic anhydride were added to 90 mL of xylene, stirred at 100 ° C for 15 minutes, and 10 mL of xylene solution containing 6 mg of benzoyl peroxide was added dropwise within 15 minutes, and then reacted for 1.5 hours to obtain a polymer resin solution; 1 g of organic vermiculite was added to the polymer resin solution, stirred and refluxed at 70 ° C for 24 hours, filtered, and the solid product was washed with acetone and ethanol in sequence, and vacuum dried to constant weight to obtain a composite modified vermiculite.

[0188] Comparative Example 6

[0189] The only difference between this example and Example 1 is that:

[0190] Steps S1-4 in this example are specifically as follows:

[0191] Take 0.5g of EPDM rubber and add it to 100mL of xylene. Stir it at 100℃ for 15min. Then add 1g of organic vermiculite and 0.2g of butyl rubber. Stir and reflux it at 70℃ for 24h. Filter it. Wash the solid product with acetone and ethanol in sequence. Dry it in vacuum to constant weight to obtain composite modified vermiculite.

[0192] Comparative Example 7

[0193] A sealing gasket, the raw materials for its preparation include the following components in parts by weight:

[0194]

[0195] The preparation method of expanded vermiculite is the same as that in Example 1.

[0196] The preparation method of the sealing gasket comprises the following steps:

[0197] 1) Banburying: adding nitrile rubber, expanded vermiculite, glass fiber, graphene, zinc oxide, white carbon black, and stearic acid into a banburying mixer and mixing at 85° C. for 6 min to obtain a banburying rubber compound;

[0198] 2) Open mixing: Add the mixed rubber material, vulcanizing agent, paraffin oil and vulcanization accelerator into an open mixing mill, mix at 70°C for 12 minutes, discharge the material, place it in an injection molding machine and press it into sheets to obtain a raw rubber gasket;

[0199] 3) Vulcanization: vulcanize the raw rubber gasket in a vulcanizer at 180° C. for 23 minutes and a vulcanization pressure of 10 MPa to obtain a sealing gasket.

[0200] Performance testing:

[0201] 1. Tensile strength and compression rebound rate:

[0202] The tensile strength was tested according to the standard GB / T 20671.7-2006 Classification system and test methods for non-metallic gasket materials Part 7: Test method for tensile strength of non-metallic gasket materials.

[0203] The compression rebound rate is tested with reference to the standard "GB / T12622-2008, GB / T 12622-2008 Test method for compression rate and rebound rate of gaskets for pipe flanges".

[0204] The test results are shown in Table 1 and Figure 1-Figure 2 As shown:

[0205] Table 1

[0206]

[0207]

[0208] It can be seen from the test results that the gaskets in the embodiments have high tensile strength and excellent rebound performance. Except for comparative examples 2 and 5, the two properties of the other comparative examples are significantly reduced to varying degrees.

[0209] 2. Sealing performance

[0210] The sealing performance was tested with reference to the standard GB / T20671 “Classification system and test methods for non-metallic gasket materials - Test methods for sealing properties of gasket materials”, and dry nitrogen was used as the gas medium to test the gas leakage rate.

[0211] The test results are shown in Table 2 and Figure 3 As shown:

[0212] Table 2

[0213]

[0214] The test results show that the gaskets in the examples have excellent sealing performance. The reduction in sealing performance in Comparative Example 1 indicates that graphene has an improved effect on improving sealing performance, while the reduction in sealing performance in Comparative Example 3 is mainly attributed to the lack of a grafted ruthenium catalyst, which affects the in-situ growth of graphene. In Comparative Example 4, the lack of polymer resin intercalation treatment on the vermiculite-based composite filler significantly affects its dispersion in the nitrile rubber matrix system, resulting in a reduction in sealing performance, as well as a reduction in properties such as tensile strength and rebound rate. The reduction in sealing performance in Comparative Example 5 illustrates the enhanced effect of the addition of butyl rubber on sealing performance. In Comparative Example 7, the inorganic filler components: expanded vermiculite, glass fiber, and graphene are directly blended and added to the nitrile rubber system. The inorganic filler components are difficult to disperse in the organic system, resulting in their inability to fully exert their respective complementary effects, resulting in a significant reduction in sealing performance, as well as a reduction in properties such as tensile strength and rebound rate.

[0215] 3. High temperature resistance

[0216] Heat the gasket at 200°C for 48 hours, then test the tensile strength using the same method as above and calculate the tensile strength retention rate using the following formula:

[0217] Tensile strength retention rate S=(G1 / G0)×100%, where G0 represents the tensile strength before aging and G1 represents the tensile strength after aging.

[0218] The test results are shown in Table 3 and Figure 4 As shown:

[0219] Table 3

[0220]

[0221] It can be seen from the test results that the gasket in the embodiment has good high temperature resistance and can serve for a long time in a high temperature environment.

[0222] 4. Resistance to heat and oxygen aging

[0223] The aging method was carried out according to the relevant method in the standard GB / T3512-2001, with an aging temperature of 180°C and an aging time of 120 hours. After the aging treatment was completed, the tensile strength retention rate was tested using the same method as above.

[0224] The test results are shown in Table 4 and Figure 5 As shown:

[0225] Table 4

[0226]

[0227] From the test results, it can be seen that the gaskets in the examples have excellent thermal oxygen aging resistance. In comparative examples 2 and 3, carbon dots are not deposited, the reducing property is lost, and the thermal oxygen aging resistance is greatly reduced.

[0228] 5. High temperature wear resistance

[0229] The test was conducted using a THT07-135 high-temperature friction and wear testing machine. The friction pair was a steel pin (material GCrl5), with a hardness of 9 GPa, a roughness of 0.02 μm, a diameter of 5 mm, an applied load of 15 N, a sliding distance of 2500 m, a linear speed of 0.5 m / s, a test temperature of 200 ° C, and a test wear rate K:

[0230] Where ΔV is the wear volume (mm 3 ), F is the load (N), and S is the total sliding distance (m).

[0231] The test results are shown in Table 5 and Figure 6 As shown:

[0232] Table 5

[0233]

[0234] It can be seen from the test results that the gasket in the embodiment still has excellent wear resistance at high temperatures, which can ensure reliability during long-term use.

[0235] 6. Infrared absorption spectrum characterization

[0236] Reference Figure 7 is the infrared absorption spectrum of the loaded vermiculite prepared in Example 1, wherein 900 cm -1 , 450cm -1 , and 650cm -1 The characteristic peaks near 540cm are derived from the stretching vibration of Si-O-Si, the bending vibration of Si-O-Si and the bending vibration of Al-O-Si in the vermiculite structure; -1 and 600cm -1 The peaks near 1580cm-1 belong to the characteristic peaks of copper oxide and ruthenium oxide; the characteristic peaks near 1050cm-1 come from the sp2 hybridization type CC bond peak and sp3 hybridization type CC bond peak in graphene, respectively, indicating that the in situ growth of graphene was successfully achieved; the appearance of amino, thiol and carboxyl characteristic peaks indicates the successful deposition of carbon dots; the successful synthesis of loaded vermiculite was characterized by this infrared absorption spectrum.

[0237] 7. Antioxidant properties

[0238] The anti-oxidation properties of the vermiculite-based composite fillers prepared in Example 1 and Comparative Examples 1 to 3 were tested respectively according to the following method:

[0239] Vermiculite-based composite fillers were added to ethanol and ultrasonically dispersed for 30 minutes to prepare a dispersion with a concentration of 1 mg / mL. The antioxidant properties of the dispersion at different times were then detected using a DPPH free radical scavenging ability test kit (Product No. UPLC-MS-4569, Specification: 100T / 48S, Shanghai Liquid Quality Testing Technology Co., Ltd.).

[0240] Assay Principle: The DPPH free radical has a single electron, and its alcohol solution appears purple with strong absorption at 515nm. In the presence of an antioxidant, the DPPH free radical is scavenged, the solution becomes lighter in color, and the absorbance at 515nm decreases. Within a certain range, the change in absorbance is proportional to the degree of free radical scavenging. In this kit, the degree of absorbance decrease reflects the sample's ability to scavenge DPPH free radicals; that is, the lower the absorbance at 515nm, the stronger the nitrogen free radical scavenging ability and the corresponding stronger antioxidant properties.

[0241] The test results are as follows Figure 7 As shown, it can be seen that the vermiculite-based composite filler prepared in Example 1 has excellent antioxidant properties, the antioxidant properties of the vermiculite-based composite fillers prepared in Comparative Examples 1 and 3 weaken in turn, and the vermiculite-based composite filler prepared in Comparative Example 2 has basically no antioxidant ability.

[0242] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the description and implementation methods. They can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to specific details.

Claims

1. A high temperature resistant and leakproof sealing gasket, characterized in that: The raw materials for its preparation include the following components by weight: The vermiculite-based composite filler is prepared by the following method: S1. Preparation of composite modified vermiculite: performing in-situ graphene growth, carbon dot deposition, organic treatment, and polymer resin intercalation treatment on expanded vermiculite to obtain composite modified vermiculite; S2, glass fiber pretreatment; S3. The pretreated glass fiber is coated with composite modified vermiculite to obtain a vermiculite-based composite filler.

2. The high temperature resistant and leakproof sealing gasket according to claim 1, characterized in that: Step S1 specifically includes: S1-1. In-situ growth of graphene: Expanded vermiculite, copper chloride, and ruthenium trichloride are added to a citric acid aqueous solution, ultrasonically treated, and heated and evaporated to dryness; the resulting product is pretreated under a hydrogen atmosphere and heated, and then heated to react in a mixed gas consisting of argon, ethylene, and hydrogen. After the reaction is completed, the mixture is cooled to obtain graphene-composite expanded vermiculite; S1-2, carbon dot deposition: Graphene-composite expanded vermiculite, citric acid, and mercaptopropionic acid are added to a mixed solution of ethanol and deionized water, stirred, and then glucose and 1,2-cyclohexanediamine are added, ultrasonically dispersed, and the resulting mixture is transferred to a reactor, heated for hydrothermal reaction, cooled after the reaction, centrifuged, filtered, and the solid product is washed and vacuum dried to obtain loaded vermiculite; S1-3, organic treatment: Adding loaded vermiculite and hexadecyltrimethylammonium bromide to deionized water, stirring, filtering, washing the solid product, and drying to obtain organic vermiculite; S1-4, polymer resin intercalation treatment: Take EPDM rubber and maleic anhydride and add them to xylene. Stir under heating. Keep stirring and dropwise add the xylene solution containing benzoyl peroxide. After the addition is complete, react to obtain a polymer resin solution. The organic vermiculite and butyl rubber are added to the polymer resin solution, and the mixture is stirred and refluxed under heating. After the reaction is completed, the mixture is filtered, the solid product is washed, and vacuum dried to obtain the composite modified vermiculite.

3. The high temperature resistant and leakproof sealing gasket according to claim 2, characterized in that: Step S1 specifically includes: S1-1. In-situ growth of graphene: 0.5-2 g of expanded vermiculite, 0.033-0.134 g of copper chloride, and 0.026-0.104 g of ruthenium trichloride are added to 50-200 mL of a 2.5-10% citric acid aqueous solution, ultrasonically treated for 15-60 minutes, and heated to dryness at 120-150° C.; the resulting product is transferred to a tube furnace, pretreated at 750-900° C. in a hydrogen atmosphere for 5-20 minutes, then kept at 880-1000° C. in a mixed gas atmosphere of argon:ethylene:hydrogen in a volume ratio of 2:2:1 for 15-60 minutes, and cooled to room temperature to obtain graphene-composite expanded vermiculite; S1-2, carbon dot deposition: 1-4 g of graphene-composite expanded vermiculite, 0.42-1.90 g of citric acid, and 0.21-0.84 g of mercaptopropionic acid are added to a mixed solution consisting of 30-120 mL of ethanol and 20-80 mL of deionized water, and the mixture is stirred under sealing for 5-30 min. 0.24-0.96 g of glucose and 0.06-0.24 g of 1,2-cyclohexanediamine are then added, and ultrasonic dispersion is performed under sealing for 10-40 min. The resulting mixture is transferred to a reactor, hydrothermally reacted at 180-230° C. for 4-16 h, cooled to room temperature, centrifuged, and the solid product is washed with ethanol and deionized water in sequence, and vacuum dried at 70-100° C. for 6-24 h to obtain supported vermiculite; S1-3, organic treatment: Take 0.5-2g of loaded vermiculite and 0.1-0.4g of hexadecyltrimethylammonium bromide and add them to 50-200mL of deionized water, stir for 1-4h, filter, wash the solid product with deionized water, and dry it to constant weight to obtain organic vermiculite; S1-4, polymer resin intercalation treatment: Take 0.25-1g of EPDM rubber and 0.025-0.1g of maleic anhydride and add them to 45-180mL of xylene. Stir at 90-110°C for 5-30min. Keep stirring and add 2.5-20mL of xylene solution containing 3-12mg of benzoyl peroxide dropwise within 10-30min. Then react for 1-4h to obtain a polymer resin solution. 0.5-2g of organic vermiculite and 0.1-0.4g of butyl rubber are added to the polymer resin solution, stirred and refluxed at 60-80°C for 12-48h, filtered, and the solid product is washed with acetone and ethanol in sequence, and vacuum dried to constant weight to obtain composite modified vermiculite.

4. The high temperature resistant and leakproof sealing gasket according to claim 1, characterized in that: The expanded vermiculite is prepared by the following method: soaking the vermiculite in hydrogen peroxide with a mass concentration of 5-20% for 2-8 hours, controlling the solid-liquid ratio to be 1:2-7, taking out the soaked vermiculite, calcining it at 400-500°C for 1-5 minutes, cooling it to room temperature, and ball milling it to a particle size of less than 0.5-5 μm to obtain the expanded vermiculite.

5. The high temperature resistant and leakproof sealing gasket according to claim 1, characterized in that: Step S2 specifically comprises: soaking the glass fiber in hydrochloric acid under heating, filtering, washing with deionized water until neutral, and vacuum drying to constant weight to obtain pretreated glass fiber.

6. The high temperature resistant and leakproof sealing gasket according to claim 5, characterized in that: Step S2 is specifically as follows: soaking the glass fiber in 0.5-2 mol / L hydrochloric acid at 40-50° C. for 15-90 min, filtering, washing with deionized water until neutral, and vacuum drying at 90-120° C. to constant weight to obtain pretreated glass fiber.

7. The high temperature resistant and leakproof sealing gasket according to claim 1, characterized in that: Step S3 is specifically as follows: S3-1, adding the composite modified vermiculite to a mixture of ethanol and deionized water, and dispersing the mixture by ultrasonication to obtain a vermiculite dispersion; S3-2. Add pretreated glass fiber to the vermiculite dispersion, disperse it by ultrasonication, then stir it under heating, increase the temperature, and stir until it is evaporated to dryness. After rinsing the obtained product, vacuum dry it to constant weight to obtain a vermiculite-based composite filler.

8. The high temperature resistant and leakproof sealing gasket according to claim 7, characterized in that: Step S3 is specifically as follows: S3-1. Take 0.5-2 g of the composite modified vermiculite and add it to 50-200 mL of a mixture of ethanol and deionized water in a volume ratio of 1:1, and ultrasonically disperse it for 15-60 minutes to obtain a vermiculite dispersion; S3-2. Add 0.25-0.1 g of pretreated glass fiber to the vermiculite dispersion, ultrasonically disperse for 15-60 minutes, then stir at 50-85°C for 1-4 hours, heat to 95-105°C, and stir until evaporated to dryness. The resulting product is rinsed with deionized water and vacuum dried at 70-100°C to constant weight to obtain a vermiculite-based composite filler.

9. The high temperature resistant and leakproof sealing gasket according to claim 1, characterized in that: The vulcanizing agent is selected from at least one of the vulcanizing agents DCP, BIPB or DBPH; The vulcanization accelerator is at least one of vulcanization accelerator TMTD, vulcanization accelerator ZBX, vulcanization accelerator ZDMC, vulcanization accelerator NA-22, and vulcanization accelerator CZ.

10. A method for preparing a high temperature resistant and leakproof sealing gasket according to any one of claims 2 to 9, characterized in that: The following steps are involved: 1) Banburying: Add nitrile rubber, vermiculite-based composite filler, zinc oxide, white carbon black, and stearic acid into a banbury mixer and mix at 75-95° C. for 2-10 min to obtain a banburying rubber compound; 2) Open mixing: Add the mixed rubber material, vulcanizing agent, paraffin oil and vulcanization accelerator into the open mixing mill, mix at 55-78°C for 5-25 minutes, discharge the material, place it in the injection molding machine and press it into sheets to obtain the raw rubber gasket; 3) Vulcanization: vulcanizing the raw rubber gasket in a vulcanizer at 160-190° C. for 12-50 min and a vulcanization pressure of 5-25 MPa to obtain the high-temperature resistant and leak-proof sealing gasket.

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