High-temperature-resistant low-friction-coefficient low-abrasion sealing material and preparation method thereof

Abstract

The invention discloses a high-temperature-resistant low-friction-coefficient low-abrasion sealing material and a preparation method thereof, and belongs to the technical field of sealing materials. The sealing material is prepared from the following raw materials in parts by mass: 60 to 80 parts of hydrogenated butadiene-acrylonitrile rubber, 20 to 40 parts of hydrogenated carboxyl butadiene-acrylonitrile rubber, 40 to 50 parts of carbon black N234, 4 to 6 parts of modified carbon fiber, 2 to 4 parts of modified hexagonal boron nitride, 3 to 5 parts of liquid polybutadiene, 3 to 4 parts of composite vulcanizing agent, 2 to 3 parts of zinc oxide, 1 to 2 parts of rubber anti-aging agent 445, 1 to 2 parts of anti-aging agent MB, 0.2 to 0.5 part of accelerant BZ and 0.5 to 2 parts of stearic acid. The modified carbon fiber is obtained by growing molybdenum disulfide on the surface of carbon fiber in situ and performing amination modification, the modified hexagonal boron nitride is obtained by performing grafting reaction on hydroxylated hexagonal boron nitride and an epoxy silane coupling agent, and the sealing material provided by the invention has high wear resistance and high temperature resistance.

Description

Technical Field

[0001] This invention belongs to the field of sealing material technology, specifically relating to a high-temperature resistant, low-friction coefficient, and low-wear sealing material and its preparation method. Background Technology

[0002] Rubber is one of the most commonly used elastic sealing materials, and its performance stability in complex environments directly determines the reliability of rubber sealing components. Sealing failures caused by high temperatures, friction, and material structural damage not only destroy the sealing structure but also lead to mechanical failures and affect the efficiency of mechanical operations.

[0003] Depending on the application environment and service conditions, the types of rubber matrices used in sealing components vary greatly. Commonly used rubber matrices for sealing materials mainly include: silicone rubber, nitrile rubber, neoprene rubber, fluororubber, polyurethane rubber, and EPDM rubber, etc. Nitrile rubber (NBR) is an important sealing material in mechanical oil seals, widely used for dynamic and static sealing of liquid oils and oil vapors.

[0004] However, compared with fluororubber, the wear resistance and high temperature resistance of nitrile rubber still need to be improved. Ordinary nitrile rubber will show a significant decrease in tensile strength in a short period of time in an environment exceeding 120°C. Therefore, it is necessary to improve nitrile rubber seals so that their wear resistance and high temperature resistance meet the requirements of high-temperature and high-speed rotational friction conditions, thereby improving their application adaptability under harsh conditions. Summary of the Invention

[0005] This invention provides a high-temperature resistant, low-friction coefficient, and low-wear sealing material and its preparation method, which can solve the problem of poor wear resistance and high-temperature resistance of nitrile rubber seals in the prior art.

[0006] The objective of this invention can be achieved through the following technical solutions: A high-temperature resistant, low-friction coefficient, and low-wear sealing material, comprising the following raw materials by weight: Hydrogenated nitrile butadiene rubber 60-80 parts, hydrogenated carboxylated nitrile butadiene rubber 20-40 parts, carbon black N234 40-50 parts, modified carbon fiber 4-6 parts, modified hexagonal boron nitride 2-4 parts, liquid polybutadiene 3-5 parts, composite vulcanizing agent 3-4 parts, zinc oxide 2-3 parts, rubber antioxidant 445 1-2 parts, antioxidant MB 1-2 parts, accelerator BZ 0.2-0.5 parts, stearic acid 0.5-2 parts; The modified carbon fiber is obtained by in-situ growth of molybdenum disulfide on the surface of carbon fiber followed by amylation modification; The modified hexagonal boron nitride was obtained by grafting hydroxylated hexagonal boron nitride with an epoxy silane coupling agent.

[0007] Hydrogenated carboxylated nitrile butadiene rubber (HXNBR) is produced by selective hydrogenation of carboxylated nitrile butadiene rubber (XNBR). Compared with hydrogenated nitrile butadiene rubber (HNBR) and carboxylated nitrile butadiene rubber (XNBR), it has higher tensile strength and tear strength. Especially under high temperature conditions, its wear resistance is far superior to that of hydrogenated nitrile butadiene rubber (HNBR). The synergistic effect of highly saturated HNBR and HXNBR ensures that the sealing material has excellent high temperature resistance and oil resistance while improving the wear resistance of the sealing material.

[0008] Furthermore, the method for preparing the modified carbon fiber includes the following steps: S1. Thiourea and ammonium molybdate tetrahydrate are mixed at a molar ratio of 1:2-4, added to deionized water and stirred to dissolve to form a mixture, short-cut carbon fibers are added and ultrasonically dispersed to obtain a dispersion. S2. Add the dispersion to a high-pressure reactor and react at 230-240℃ for 24 hours. After cooling to room temperature, filter, wash and dry to obtain carbon fibers with in-situ molybdenum disulfide growth. S3. Mix the carbon fiber obtained in step S2 with the n-hexane solution of n-butyllithium, add it to the reaction vessel, react at 100-105℃ for 3-4h, cool to room temperature, stir under nitrogen atmosphere for 24-48h, filter and dry the product, add deionized water and sonicate for 12-24h to form a stripping product solution, filter and freeze dry to obtain product A. S4. Add product A to an aqueous solution of mercaptoethylamine, sonicate for 24-48 hours, filter, and freeze-dry to obtain modified carbon fiber.

[0009] Carbon fiber possesses properties such as low specific gravity, high strength, and self-lubrication. Filling with carbon fiber can significantly improve its strength and resistance to friction and wear. However, as a friction-reducing material, carbon fiber has few surface active groups, resulting in poor compatibility when directly filled into rubber systems, making it prone to peeling and leading to an increase in the coefficient of friction and wear rate. In-situ growth of molybdenum disulfide on the carbon fiber surface via hydrothermal synthesis can increase lubrication sites and reduce the coefficient of friction. However, the surface-grown molybdenum disulfide exhibits a multi-layered structure with significant thickness, leading to a high surface roughness and, from the perspective of the carbon fiber itself, increasing wear. A novel approach involves peeling molybdenum disulfide from the carbon fiber surface using a lithium-ion intercalation method. This controls the presence of a single layer of molybdenum disulfide on the carbon fiber surface, ensuring friction reduction while allowing for amination modification through the sulfur atom deletion sites. The introduced amino groups can chemically react with the carboxyl groups of HXNBR to form strong amide bonds, greatly improving the interfacial bonding between the carbon fiber and the rubber matrix and avoiding the interfacial debonding and stress concentration problems that are common with carbon fiber as a rigid filler.

[0010] Furthermore, the concentration of thiourea in the mixture is 0.2-0.5 mol / L.

[0011] Furthermore, the concentration of short-cut carbon fibers in the dispersion is 20-30 g / L.

[0012] Furthermore, the concentration of the n-butyllithium in the n-hexane solution is 0.5-1.0 mol / L; The carbon fiber and n-butyllithium hexane solution obtained in step S2 are mixed at a mass ratio of carbon fiber to n-butyllithium of 1.2-1.5:1.

[0013] Furthermore, the concentration of the mercaptoethylamine aqueous solution is 0.1-0.3 mol / L; The mass ratio of product A to mercaptoethylamine is 0.2-0.5:1.

[0014] Furthermore, the preparation method of the modified hexagonal boron nitride includes the following steps: A1. Disperse hexagonal boron nitride powder in sodium hydroxide solution, hydrolyze at 110-130℃ for 24-48h, centrifuge, take the precipitate, wash with deionized water until neutral, add deionized water and sonicate for 12-18h, centrifuge, take the supernatant, filter and dry to obtain hydroxylated hexagonal boron nitride. A2. Hydroxylated hexagonal boron nitride and epoxy silane coupling agent are mixed, and the mixture is added to an aqueous ethanol solution. The mixture is heated under reflux at 80-83℃ for 12-16 hours. The solvent is removed by centrifugation, and the mixture is washed and then vacuum dried to obtain modified hexagonal boron nitride.

[0015] Hexagonal boron nitride (h-BN) possesses excellent heat resistance and good lubricity, with a low coefficient of friction, making it suitable for lubrication at high temperatures. However, its surface chemical inertness and strong interlaminar van der Waals forces make it prone to aggregation in polymer matrices, preventing it from exerting its original function. Hydroxylated hexagonal boron nitride is obtained through high-temperature alkali treatment combined with auxiliary ultrasound. This is then grafted with an epoxy coupling agent to introduce epoxy groups, which can react with carboxyl or amine groups (modified carbon fibers) in the rubber matrix. This allows h-BN to be firmly anchored in the rubber network, preventing it from easily detaching during friction and providing continuous and stable friction-reducing and wear-resistant effects. Simultaneously, the modified carbon fibers and modified hexagonal boron nitride are tightly bonded through chemical bonding. The modified hexagonal boron nitride effectively fills the gaps between the rubber matrix and the modified carbon fibers, reducing interfacial stress and improving wear resistance.

[0016] Furthermore, the concentration of the sodium hydroxide solution is 2-5 mol / L; The concentration of the hexagonal boron nitride powder in the sodium hydroxide solution is 1-2 g / L.

[0017] Furthermore, the epoxy silane coupling agent is at least one of KH560 and KH562.

[0018] Furthermore, the epoxysilane coupling agent is 5-10% by mass of hydroxylated hexagonal boron nitride.

[0019] Furthermore, the mass-to-volume ratio of the mixture to the aqueous ethanol solution is 15-25 g / L.

[0020] Furthermore, the composite vulcanizing agent is a mixture of di-tert-butyl peroxide isopropylbenzene and trimethylolpropane trimethacrylate in a mass ratio of 1-2:1. Di-tert-butyl peroxide is a representative peroxide vulcanizing agent, generating carbon-carbon crosslinks with high bond energy, giving the product excellent heat resistance and low compression set. Trimethylolpropane trimethacrylate assists in vulcanization, self-polymerizing under the action of peroxide free radicals and linking with rubber molecules, which can significantly improve crosslinking density and efficiency, while improving the hardness and wear resistance of the material.

[0021] This invention also provides a method for preparing a high-temperature resistant, low-friction coefficient, and low-wear sealing material, which includes the following steps: Step 1: Prepare raw materials according to the ratio. Mix hydrogenated nitrile rubber and hydrogenated carboxylated nitrile rubber and then put them into an internal mixer for plasticizing for 2-5 minutes. Step 2: Add stearic acid, liquid polybutadiene, carbon black N234, modified carbon fiber, modified hexagonal boron nitride, zinc oxide, rubber antioxidant 445 and antioxidant MB, and mix for 3-6 minutes until the temperature reaches 120-130℃. Step 3: Cool and let the first-stage compound stand for 8-10 hours. Add accelerator BZ and compound vulcanizing agent to the first-stage compound. Mix the second stage for 2-3 minutes until the temperature reaches 80-90℃ and pour the rubber. Step 4: Feed the two-stage compounded rubber into the open mill rolls, pass through a thin pass, form a triangular roll, and then extrude it as a sheet to obtain the final compounded rubber. Step 5: The final compound is molded and vulcanized to obtain the sealing material.

[0022] The beneficial effects of this invention are: (1) The present invention uses hydrogenated nitrile butadiene rubber and hydrogenated carboxylated nitrile butadiene rubber to form a rubber matrix. The main chain of hydrogenated nitrile butadiene rubber has high saturation and good heat resistance and oil resistance. The carboxyl group is introduced by hydrogenated carboxylated nitrile butadiene rubber, and combined with modified carbon fiber and modified hexagonal boron nitride filler with good heat resistance, so that the material can work stably for a long time above 150°C, giving full play to the synergistic lubrication and reinforcement effect of the filler, and thus preparing a sealing material with high temperature resistance, low friction coefficient and low wear.

[0023] (2) In this invention, modified carbon fiber and modified hexagonal boron nitride are added to the rubber matrix. The molybdenum disulfide and boron nitride on the modified carbon fiber act as efficient solid lubricants, forming a stable transfer film at the friction interface, achieving continuous lubrication, significantly reducing the coefficient of friction, reducing wear, and synergistically improving the friction performance of the sealing material.

[0024] (3) This invention achieves a strong bond between the filler and the matrix through interfacial chemical bonding of hydrogenated carboxylated nitrile rubber and modified filler, avoiding failure caused by stress concentration and significantly improving the fatigue life of the sealing material. At the same time, the modified filler (modified carbon fiber and modified hexagonal boron nitride) utilizes the active groups (amino and epoxy groups) on its surface to participate in the crosslinking of the rubber matrix to construct a three-dimensional network structure, further improving the high-temperature resistance of the sealing material.

[0025] (4) In the preparation of modified carbon fiber, the boron nitride on the surface of carbon fiber can be made into a single layer or few layers by the interlayer exfoliation method. The interlayer sliding resistance is low, which can form a more continuous lubricating film with low friction coefficient and wear rate. At the same time, sulfur atom missing sites can be formed by exfoliation, which creates conditions for amination modification, enhances the bonding force between modified boron nitride and rubber matrix, and improves the friction reduction effect. Detailed Implementation

[0026] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0027] Example 1

[0028] Preparation of modified carbon fibers: S1. Weigh out ammonium molybdate tetrahydrate ((NH4)6Mo7O) according to a molar ratio of molybdenum to sulfur of 1:3. 24 A mixture of thiourea (CH4N2S) and 4H2O was added to deionized water and magnetically stirred for 30 minutes until completely dissolved to form a solution. The concentration of thiourea in the solution was 0.3 mol / L. Short-cut carbon fibers were weighed and added to the solution. The solution was then ultrasonically dispersed in an ultrasonic disperser for 20 minutes to obtain a dispersion with a concentration of 25 g / L.

[0029] S2. Add the dispersion to a high-pressure reactor, heat to 230℃ and react at a constant temperature for 24 hours. After cooling to room temperature, filter and wash with ethanol and deionized water three times each. Transfer to an oven and dry at 100℃ for 24 hours to obtain carbon fibers with in-situ molybdenum disulfide growth.

[0030] S3. Dissolve n-butyllithium in n-hexane to prepare a solution with a concentration of 0.6 mol / L. Mix the carbon fiber and the n-butyllithium n-hexane solution obtained in step S2 at a mass ratio of 1.4:1, add them to a reaction vessel, heat to 100℃ and react at a constant temperature for 4 hours. Cool to room temperature, replace the reaction vessel with nitrogen gas, stir under nitrogen atmosphere for 48 hours, filter, and dry in a vacuum drying oven at 60℃ for 4 hours. Add the obtained product to deionized water at a concentration of 10 g / L, place it in an ultrasonic disperser and sonicate for 24 hours to form a stripping product solution, filter and freeze dry to obtain product A.

[0031] S4. Add product A to a 0.2 mol / L aqueous solution of mercaptoethylamine, wherein the mass ratio of product A to mercaptoethylamine is 0.4:1. Place the mixture in an ultrasonic disperser and react ultrasonically for 48 h. After filtration, freeze dry to obtain modified carbon fiber.

[0032] Preparation of modified hexagonal boron nitride: A1. Weigh hexagonal boron nitride powder and disperse it in 5 mol / L sodium hydroxide solution at a concentration of 1.5 g / L. Heat to 120℃ for hydrolysis for 48 h. After centrifugation, collect the precipitate and wash it with deionized water until neutral. Add the product to deionized water at a concentration of 20 g / L and sonicate it in an ultrasonic disperser for 16 h. Transfer the suspension to a centrifuge and centrifuge at 2000 r / min for 5 min. Take the supernatant, filter it, and dry it at 60℃ for 8 h to obtain hydroxylated hexagonal boron nitride.

[0033] A2. Hydroxylated hexagonal boron nitride and KH560 silane coupling agent were mixed, with KH560 silane coupling agent accounting for 8% of the mass of hydroxylated hexagonal boron nitride. An ethanol-water solution was prepared according to a volume ratio of 9:1 for ethanol and water. The mixture was added to the ethanol-water solution at a concentration of 20 g / L. The mixture was heated to 80 °C and refluxed for 15 h. After cooling to room temperature, it was transferred to a centrifuge, and the solvent was removed by centrifugation. The precipitate was collected and washed twice each with ethanol and acetone. After washing, it was placed in a vacuum drying oven and dried at 80 °C for 6 h to obtain modified hexagonal boron nitride.

[0034] Preparation of sealing materials: Step 1: Prepare the raw materials for the sealing material according to the following mass proportions: 70 parts hydrogenated nitrile butadiene rubber (Mounney viscosity = 72 (ML1+4, 100℃), ACN mass fraction = 36%, degree of hydrogenation = 98%), 30 parts hydrogenated carboxylated nitrile butadiene rubber (Mounney viscosity = 77 (ML1+4, 100℃), ACN mass fraction = 33%, residual unsaturation = 3.5%), 45 parts carbon black N234, 5 parts modified carbon fiber, 3 parts modified hexagonal boron nitride, 4 parts liquid polybutadiene, 3.5 parts composite vulcanizing agent (a mixture of di-tert-butyl peroxide isopropylbenzene and trimethylolpropane trimethacrylate in a mass ratio of 2:1), 2.5 parts zinc oxide, 1.5 parts rubber antioxidant 445, 1.5 parts antioxidant MB, 0.3 parts accelerator BZ, and 1 part stearic acid. After mixing hydrogenated nitrile rubber and hydrogenated carboxylated nitrile rubber, the mixture is put into an internal mixer and plasticized for 3 minutes.

[0035] Step 2: Add stearic acid, liquid polybutadiene, carbon black N234, modified carbon fiber, modified hexagonal boron nitride, zinc oxide, rubber antioxidant 445 and antioxidant MB, and mix for 5 minutes until the temperature reaches 130℃.

[0036] Step 3: Cool and let the first-stage compound stand for 8 hours. Add accelerator BZ and compound vulcanizing agent to the first-stage compound. Mix the second stage for 3 minutes until the temperature reaches 90℃ and then pour the rubber.

[0037] Step 4: Feed the two-stage compounded rubber into the open mill rolls, pass through a thin pass, form a triangular roll, and then extrude the final compounded rubber.

[0038] Step 5: The final compound is subjected to compression molding and vulcanization, with the vulcanization pressure controlled at 15MPa and the vulcanization temperature at 160℃, to obtain the sealing material.

[0039] Example 2

[0040] The only difference from Example 1 is that the mass fraction of modified carbon fiber in the sealing material raw material is increased to 6 parts, while the other steps and conditions are the same as in Example 1.

[0041] Example 3

[0042] The only difference from Example 1 is that the mass fraction of modified carbon fiber in the sealing material raw material is reduced to 4 parts, while the other steps and conditions are the same as in Example 1.

[0043] Example 4

[0044] The only difference from Example 1 is that the mass fraction of modified hexagonal boron nitride in the sealing material raw material is increased to 4 parts, while the other steps and conditions are the same as in Example 1.

[0045] Example 5

[0046] The only difference from Example 1 is that the mass fraction of modified hexagonal boron nitride in the sealing material raw material is reduced to 2 parts, while the other steps and conditions are the same as in Example 1.

[0047] Example 6

[0048] The only difference from Example 1 is that the mass fraction of hydrogenated nitrile rubber in the sealing material raw material is increased to 80 parts, and the mass fraction of hydrogenated carboxylated nitrile rubber is reduced to 20 parts. The other steps and conditions are the same as in Example 1.

[0049] Example 7

[0050] The only difference from Example 1 is that the mass fraction of hydrogenated nitrile rubber in the sealing material raw material is reduced to 60 parts, and the mass fraction of hydrogenated carboxylated nitrile rubber is increased to 40 parts. The other steps and conditions are the same as in Example 1.

[0051] Examples 8-9

[0052] The only difference from Example 1 is that the proportion of additives in the raw materials of the sealing material is different, as shown in Table 1. The other steps and conditions are the same as in Example 1.

[0053] Table 1

[0054] Comparative Example 1

[0055] The only difference from Example 1 is that no modified carbon fiber is added to the raw materials of the sealing material in this comparative example.

[0056] Preparation of modified hexagonal boron nitride: A1. Weigh hexagonal boron nitride powder and disperse it in 5 mol / L sodium hydroxide solution at a concentration of 1.5 g / L. Heat to 120℃ for hydrolysis for 48 h. After centrifugation, collect the precipitate and wash it with deionized water until neutral. Add the product to deionized water at a concentration of 20 g / L and sonicate it in an ultrasonic disperser for 16 h. Transfer the suspension to a centrifuge and centrifuge at 2000 r / min for 5 min. Take the supernatant, filter it, and dry it at 60℃ for 8 h to obtain hydroxylated hexagonal boron nitride.

[0057] A2. Hydroxylated hexagonal boron nitride and KH560 silane coupling agent were mixed, with KH560 silane coupling agent accounting for 8% of the mass of hydroxylated hexagonal boron nitride. An ethanol-water solution was prepared according to a volume ratio of 9:1 for ethanol and water. The mixture was added to the ethanol-water solution at a concentration of 20 g / L. The mixture was heated to 80 °C and refluxed for 15 h. After cooling to room temperature, it was transferred to a centrifuge, and the solvent was removed by centrifugation. The precipitate was collected and washed twice each with ethanol and acetone. After washing, it was placed in a vacuum drying oven and dried at 80 °C for 6 h to obtain modified hexagonal boron nitride.

[0058] Preparation of sealing materials: Step 1: Prepare the raw materials for the sealing material according to the following mass proportions: 70 parts hydrogenated nitrile butadiene rubber (Mounney viscosity = 72 (ML1+4, 100℃), ACN mass fraction = 36%, degree of hydrogenation = 98%), 30 parts hydrogenated carboxylated nitrile butadiene rubber (Mounney viscosity = 77 (ML1+4, 100℃), ACN mass fraction = 33%, residual unsaturation = 3.5%), 45 parts carbon black N234, 3 parts modified hexagonal boron nitride, 4 parts liquid polybutadiene, 3.5 parts composite vulcanizing agent (a mixture of di-tert-butylperoxyisopropylbenzene and trimethylolpropane trimethacrylate in a mass ratio of 2:1), 2.5 parts zinc oxide, 1.5 parts rubber antioxidant 445, 1.5 parts antioxidant MB, 0.3 parts accelerator BZ, and 1 part stearic acid. Mix the hydrogenated nitrile butadiene rubber and the hydrogenated carboxylated nitrile butadiene rubber and then plasticize them in a mixer for 3 minutes.

[0059] Step 2: Add stearic acid, liquid polybutadiene, carbon black N234, modified hexagonal boron nitride, zinc oxide, rubber antioxidant 445 and antioxidant MB, and mix for 5 minutes until the temperature reaches 130℃.

[0060] Step 3: Cool and let the first-stage compound stand for 8 hours. Add accelerator BZ and compound vulcanizing agent to the first-stage compound. Mix the second stage for 3 minutes until the temperature reaches 90℃ and then pour the rubber.

[0061] Step 4: Feed the two-stage compounded rubber into the open mill rolls, pass through a thin pass, form a triangular roll, and then extrude the final compounded rubber.

[0062] Step 5: The final compound is subjected to compression molding and vulcanization, with the vulcanization pressure controlled at 15MPa and the vulcanization temperature at 160℃, to obtain the sealing material.

[0063] Comparative Example 2

[0064] The only difference from Example 1 is that the modified carbon fiber is replaced by short-cut carbon fiber in the sealing material raw material of this comparative example.

[0065] Preparation of modified hexagonal boron nitride: A1. Weigh hexagonal boron nitride powder and disperse it in 5 mol / L sodium hydroxide solution at a concentration of 1.5 g / L. Heat to 120℃ for hydrolysis for 48 h. After centrifugation, collect the precipitate and wash it with deionized water until neutral. Add the product to deionized water at a concentration of 20 g / L and sonicate it in an ultrasonic disperser for 16 h. Transfer the suspension to a centrifuge and centrifuge at 2000 r / min for 5 min. Take the supernatant, filter it, and dry it at 60℃ for 8 h to obtain hydroxylated hexagonal boron nitride.

[0066] A2. Hydroxylated hexagonal boron nitride and KH560 silane coupling agent were mixed, with KH560 silane coupling agent accounting for 8% of the mass of hydroxylated hexagonal boron nitride. An ethanol-water solution was prepared according to a volume ratio of 9:1 for ethanol and water. The mixture was added to the ethanol-water solution at a concentration of 20 g / L. The mixture was heated to 80 °C and refluxed for 15 h. After cooling to room temperature, it was transferred to a centrifuge, and the solvent was removed by centrifugation. The precipitate was collected and washed twice each with ethanol and acetone. After washing, it was placed in a vacuum drying oven and dried at 80 °C for 6 h to obtain modified hexagonal boron nitride.

[0067] Preparation of sealing materials: Step 1: Prepare the raw materials for the sealing material according to the following mass proportions: 70 parts hydrogenated nitrile butadiene rubber (Mounney viscosity = 72 (ML1+4, 100℃), ACN mass fraction = 36%, degree of hydrogenation = 98%), 30 parts hydrogenated carboxylated nitrile butadiene rubber (Mounney viscosity = 77 (ML1+4, 100℃), ACN mass fraction = 33%, residual unsaturation = 3.5%), 45 parts carbon black N234, 5 parts chopped carbon fiber, 3 parts modified hexagonal boron nitride, 4 parts liquid polybutadiene, 3.5 parts composite vulcanizing agent (a mixture of di-tert-butyl peroxide isopropylbenzene and trimethylolpropane trimethacrylate in a mass ratio of 2:1), 2.5 parts zinc oxide, 1.5 parts rubber antioxidant 445, 1.5 parts antioxidant MB, 0.3 parts accelerator BZ, and 1 part stearic acid. After mixing hydrogenated nitrile rubber and hydrogenated carboxylated nitrile rubber, the mixture is put into an internal mixer and plasticized for 3 minutes.

[0068] Step 2: Add stearic acid, liquid polybutadiene, carbon black N234, chopped carbon fiber, modified hexagonal boron nitride, zinc oxide, rubber antioxidant 445 and antioxidant MB, and mix for 5 minutes until the temperature reaches 130℃.

[0069] Step 3: Cool and let the first-stage compound stand for 8 hours. Add accelerator BZ and compound vulcanizing agent to the first-stage compound. Mix the second stage for 3 minutes until the temperature reaches 90℃ and then pour the rubber.

[0070] Step 4: Feed the two-stage compounded rubber into the open mill rolls, pass through a thin pass, form a triangular roll, and then extrude the final compounded rubber.

[0071] Step 5: The final compound is subjected to compression molding and vulcanization, with the vulcanization pressure controlled at 15MPa and the vulcanization temperature at 160℃, to obtain the sealing material.

[0072] Comparative Example 3

[0073] The only difference from Example 1 is that the sealing material raw material of this comparative example does not contain modified hexagonal boron nitride.

[0074] Preparation of modified carbon fibers: S1. Weigh out ammonium molybdate tetrahydrate ((NH4)6Mo7O) according to a molar ratio of molybdenum to sulfur of 1:3.24 A mixture of thiourea (CH4N2S) and 4H2O was added to deionized water and magnetically stirred for 30 minutes until completely dissolved to form a solution. The concentration of thiourea in the solution was 0.3 mol / L. Short-cut carbon fibers were weighed and added to the solution. The solution was then ultrasonically dispersed in an ultrasonic disperser for 20 minutes to obtain a dispersion with a concentration of 25 g / L.

[0075] S2. Add the dispersion to a high-pressure reactor, heat to 230℃ and react at a constant temperature for 24 hours. After cooling to room temperature, filter and wash with ethanol and deionized water three times each. Transfer to an oven and dry at 100℃ for 24 hours to obtain carbon fibers with in-situ molybdenum disulfide growth.

[0076] S3. Dissolve n-butyllithium in n-hexane to prepare a solution with a concentration of 0.6 mol / L. Mix the carbon fiber and the n-butyllithium n-hexane solution obtained in step S2 at a mass ratio of 1.4:1, add them to a reaction vessel, heat to 100℃ and react at a constant temperature for 4 hours. Cool to room temperature, replace the reaction vessel with nitrogen gas, stir under nitrogen atmosphere for 48 hours, filter, and dry in a vacuum drying oven at 60℃ for 4 hours. Add the obtained product to deionized water at a concentration of 10 g / L, place it in an ultrasonic disperser and sonicate for 24 hours to form a stripping product solution, filter and freeze dry to obtain product A.

[0077] S4. Add product A to a 0.2 mol / L aqueous solution of mercaptoethylamine, wherein the mass ratio of product A to mercaptoethylamine is 0.4:1. Place the mixture in an ultrasonic disperser and react ultrasonically for 48 h. After filtration, freeze dry to obtain modified carbon fiber.

[0078] Preparation of sealing materials: Step 1: Prepare the raw materials for the sealing material according to the following mass proportions: 70 parts hydrogenated nitrile butadiene rubber (Mounney viscosity = 72 (ML1+4, 100℃), ACN mass fraction = 36%, degree of hydrogenation = 98%), 30 parts hydrogenated carboxylated nitrile butadiene rubber (Mounney viscosity = 77 (ML1+4, 100℃), ACN mass fraction = 33%, residual unsaturation = 3.5%), 45 parts carbon black N234, 5 parts modified carbon fiber, 4 parts liquid polybutadiene, 3.5 parts composite vulcanizing agent (a mixture of di-tert-butylperoxide isopropylbenzene and trimethylolpropane trimethacrylate in a mass ratio of 2:1), 2.5 parts zinc oxide, 1.5 parts rubber antioxidant 445, 1.5 parts antioxidant MB, 0.3 parts accelerator BZ, and 1 part stearic acid. Mix the hydrogenated nitrile butadiene rubber and the hydrogenated carboxylated nitrile butadiene rubber and then plasticize them in a mixer for 3 minutes.

[0079] Step 2: Add stearic acid, liquid polybutadiene, carbon black N234, modified carbon fiber, zinc oxide, rubber antioxidant 445 and antioxidant MB, and mix for 5 minutes until the temperature reaches 130℃.

[0080] Step 3: Cool and let the first-stage compound stand for 8 hours. Add accelerator BZ and compound vulcanizing agent to the first-stage compound. Mix the second stage for 3 minutes until the temperature reaches 90℃ and then pour the rubber.

[0081] Step 4: Feed the two-stage compounded rubber into the open mill rolls, pass through a thin pass, form a triangular roll, and then extrude the final compounded rubber.

[0082] Step 5: The final compound is subjected to compression molding and vulcanization, with the vulcanization pressure controlled at 15MPa and the vulcanization temperature at 160℃, to obtain the sealing material.

[0083] Comparative Example 4

[0084] The only difference from Example 1 is that the sealing material raw material in this comparative example is modified hexagonal boron nitride replaced by hexagonal boron nitride by mass.

[0085] Preparation of modified carbon fibers: S1. Weigh out ammonium molybdate tetrahydrate ((NH4)6Mo7O) according to a molar ratio of molybdenum to sulfur of 1:3. 24 A mixture of thiourea (CH4N2S) and 4H2O was added to deionized water and magnetically stirred for 30 minutes until completely dissolved to form a solution. The concentration of thiourea in the solution was 0.3 mol / L. Short-cut carbon fibers were weighed and added to the solution. The solution was then ultrasonically dispersed in an ultrasonic disperser for 20 minutes to obtain a dispersion with a concentration of 25 g / L.

[0086] S2. Add the dispersion to a high-pressure reactor, heat to 230℃ and react at a constant temperature for 24 hours. After cooling to room temperature, filter and wash with ethanol and deionized water three times each. Transfer to an oven and dry at 100℃ for 24 hours to obtain carbon fibers with in-situ molybdenum disulfide growth.

[0087] S3. Dissolve n-butyllithium in n-hexane to prepare a solution with a concentration of 0.6 mol / L. Mix the carbon fiber and the n-butyllithium n-hexane solution obtained in step S2 at a mass ratio of 1.4:1, add them to a reaction vessel, heat to 100℃ and react at a constant temperature for 4 hours. Cool to room temperature, replace the reaction vessel with nitrogen gas, stir under nitrogen atmosphere for 48 hours, filter, and dry in a vacuum drying oven at 60℃ for 4 hours. Add the obtained product to deionized water at a concentration of 10 g / L, place it in an ultrasonic disperser and sonicate for 24 hours to form a stripping product solution, filter and freeze dry to obtain product A.

[0088] S4. Add product A to a 0.2 mol / L aqueous solution of mercaptoethylamine, wherein the mass ratio of product A to mercaptoethylamine is 0.4:1. Place the mixture in an ultrasonic disperser and react ultrasonically for 48 h. After filtration, freeze dry to obtain modified carbon fiber.

[0089] Preparation of sealing materials: Step 1: Prepare the raw materials for the sealing material according to the following mass proportions: 70 parts hydrogenated nitrile butadiene rubber (Mounney viscosity = 72 (ML1+4, 100℃), ACN mass fraction = 36%, degree of hydrogenation = 98%), 30 parts hydrogenated carboxylated nitrile butadiene rubber (Mounney viscosity = 77 (ML1+4, 100℃), ACN mass fraction = 33%, residual unsaturation = 3.5%), 45 parts carbon black N234, 5 parts modified carbon fiber, 3 parts hexagonal boron nitride, 4 parts liquid polybutadiene, 3.5 parts composite vulcanizing agent (a mixture of di-tert-butyl peroxide isopropylbenzene and trimethylolpropane trimethacrylate in a mass ratio of 2:1), 2.5 parts zinc oxide, 1.5 parts rubber antioxidant 445, 1.5 parts antioxidant MB, 0.3 parts accelerator BZ, and 1 part stearic acid. After mixing hydrogenated nitrile rubber and hydrogenated carboxylated nitrile rubber, the mixture is put into an internal mixer and plasticized for 3 minutes.

[0090] Step 2: Add stearic acid, liquid polybutadiene, carbon black N234, modified carbon fiber, hexagonal boron nitride, zinc oxide, rubber antioxidant 445 and antioxidant MB, and mix for 5 minutes until the temperature reaches 130℃.

[0091] Step 3: Cool and let the first-stage compound stand for 8 hours. Add accelerator BZ and compound vulcanizing agent to the first-stage compound. Mix the second stage for 3 minutes until the temperature reaches 90℃ and then pour the rubber.

[0092] Step 4: Feed the two-stage compounded rubber into the open mill rolls, pass through a thin pass, form a triangular roll, and then extrude the final compounded rubber.

[0093] Step 5: The final compound is subjected to compression molding and vulcanization, with the vulcanization pressure controlled at 15MPa and the vulcanization temperature at 160℃, to obtain the sealing material.

[0094] The performance of the sealing materials prepared in Examples 1-9 and Comparative Examples 1-4 was tested, and the results are shown in Table 2.

[0095] The wear index was tested according to ISO 4649 test standard, the dynamic friction coefficient was tested according to Method A in HG / T 2729-2012 test standard, the Shore hardness (Type A) was tested according to ASTM D-2240, and the high temperature resistance test was conducted according to ASTM D-573 standard. The material was placed at 150℃ for 70 hours to test the change rate of tensile strength, change rate of elongation at break, and change value of hardness under high temperature treatment.

[0096] Table 2

[0097] As can be seen from Table 2, the sealing material prepared in the embodiments of the present invention has better wear resistance and high temperature resistance than the comparative example. The addition of modified carbon fiber and modified hexagonal boron nitride to the rubber matrix, along with other raw materials, greatly reduces the coefficient of friction of the sealing material, reduces wear, and maintains good performance at a high temperature of 150°C, making it suitable for long-term use at high temperatures.

[0098] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0099] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A high-temperature resistant, low-friction coefficient, and low-wear sealing material, characterized in that, By weight, it includes the following raw materials: Hydrogenated nitrile butadiene rubber 60-80 parts, hydrogenated carboxylated nitrile butadiene rubber 20-40 parts, carbon black N234 40-50 parts, modified carbon fiber 4-6 parts, modified hexagonal boron nitride 2-4 parts, liquid polybutadiene 3-5 parts, composite vulcanizing agent 3-4 parts, zinc oxide 2-3 parts, rubber antioxidant 445 1-2 parts, antioxidant MB 1-2 parts, accelerator BZ 0.2-0.5 parts, stearic acid 0.5-2 parts; The modified carbon fiber is obtained by in-situ growth of molybdenum disulfide on the surface of carbon fiber followed by amylation modification; The modified hexagonal boron nitride was obtained by grafting hydroxylated hexagonal boron nitride with an epoxy silane coupling agent.

2. The high-temperature resistant, low-friction coefficient, and low-wear sealing material according to claim 1, characterized in that, The method for preparing the modified carbon fiber includes the following steps: S1. Thiourea and ammonium molybdate tetrahydrate are mixed at a molar ratio of 1:2-4, added to deionized water and stirred to dissolve to form a mixture, short-cut carbon fibers are added and ultrasonically dispersed to obtain a dispersion. S2. Add the dispersion to a high-pressure reactor and react at 230-240℃ for 24 hours. After cooling to room temperature, filter, wash and dry to obtain carbon fibers with in-situ molybdenum disulfide growth. S3. Mix the carbon fiber obtained in step S2 with the n-hexane solution of n-butyllithium, add it to the reaction vessel, react at 100-105℃ for 3-4h, cool to room temperature, stir under nitrogen atmosphere for 24-48h, filter and dry the product, add deionized water and sonicate for 12-24h to form a stripping product solution, filter and freeze dry to obtain product A. S4. Add product A to an aqueous solution of mercaptoethylamine, sonicate for 24-48 hours, filter, and freeze-dry to obtain modified carbon fiber.

3. The high-temperature resistant, low-friction coefficient, and low-wear sealing material according to claim 2, characterized in that, The concentration of thiourea in the mixture is 0.2-0.5 mol / L; The concentration of short-cut carbon fibers in the dispersion is 20-30 g / L.

4. The high-temperature resistant, low-friction coefficient, and low-wear sealing material according to claim 2, characterized in that, The concentration of the n-butyllithium in the n-hexane solution is 0.5-1.0 mol / L; The carbon fiber and n-butyllithium hexane solution obtained in step S2 are mixed at a mass ratio of carbon fiber to n-butyllithium of 1.2-1.5:

1.

5. The high-temperature resistant, low-friction coefficient, and low-wear sealing material according to claim 2, characterized in that, The concentration of the mercaptoethylamine aqueous solution is 0.1-0.3 mol / L; The mass ratio of product A to mercaptoethylamine is 0.2-0.5:

1.

6. The high-temperature resistant, low-friction coefficient, and low-wear sealing material according to claim 1, characterized in that, The method for preparing the modified hexagonal boron nitride includes the following steps: A1. Disperse hexagonal boron nitride powder in sodium hydroxide solution, hydrolyze at 110-130℃ for 24-48h, centrifuge, take the precipitate, wash with deionized water until neutral, add deionized water and sonicate for 12-18h, centrifuge, take the supernatant, filter and dry to obtain hydroxylated hexagonal boron nitride. A2. Hydroxylated hexagonal boron nitride and epoxy silane coupling agent are mixed, and the mixture is added to an aqueous ethanol solution. The mixture is heated under reflux at 80-83℃ for 12-16 hours. The solvent is removed by centrifugation, and the mixture is washed and then vacuum dried to obtain modified hexagonal boron nitride.

7. The high-temperature resistant, low-friction coefficient, and low-wear sealing material according to claim 6, characterized in that, The concentration of the sodium hydroxide solution is 2-5 mol / L; The concentration of the hexagonal boron nitride powder in the sodium hydroxide solution is 1-2 g / L.

8. The high-temperature resistant, low-friction coefficient, and low-wear sealing material according to claim 6, characterized in that, The epoxy silane coupling agent is 5-10% by mass of hydroxylated hexagonal boron nitride; The mass-to-volume ratio of the mixture to the aqueous ethanol solution is 15-25 g / L.

9. The high-temperature resistant, low-friction coefficient, and low-wear sealing material according to claim 1, characterized in that, The composite vulcanizing agent is a mixture of di-tert-butylperoxyisopropylbenzene and trimethylolpropane trimethacrylate in a mass ratio of 1-2:

1.

10. A method for preparing a high-temperature resistant, low-friction coefficient, and low-wear sealing material, characterized in that, The preparation of the high-temperature resistant, low-friction coefficient, and low-wear sealing material as described in any one of claims 1-9 includes the following steps: Step 1: Prepare raw materials according to the ratio. Mix hydrogenated nitrile rubber and hydrogenated carboxylated nitrile rubber and then put them into an internal mixer for plasticizing for 2-5 minutes. Step 2: Add stearic acid, liquid polybutadiene, carbon black N234, modified carbon fiber, modified hexagonal boron nitride, zinc oxide, rubber antioxidant 445 and antioxidant MB, and mix for 3-6 minutes until the temperature reaches 120-130℃. Step 3: Cool and let the first-stage compound stand for 8-10 hours. Add accelerator BZ and compound vulcanizing agent to the first-stage compound. Mix the second stage for 2-3 minutes until the temperature reaches 80-90℃ and pour the rubber. Step 4: Feed the two-stage compounded rubber into the open mill rolls, pass through a thin pass to form a triangular roll, and then extrude it as a sheet to obtain the final compounded rubber. Step 5: The final compound is molded and vulcanized to obtain the sealing material.

Images