A wear-resistant and heat-resistant sealing gasket and its preparation process

Abstract

The present invention discloses a wear-resistant and heat-resistant sealing gasket and a preparation process thereof, the process comprising the following steps: step 1, pre-drying polytetrafluoroethylene and polyperfluoroethylene propylene; step 2, mixing polyperfluoroethylene propylene, carbon fiber-carbon nanotube composite modified filler and polytetrafluoroethylene, stirring; step 3, adding the mixture into a mold for compression molding; sintering, cooling, obtaining a gasket blank; step 4, mechanical processing, obtaining a sealing gasket. In the present invention, by constructing a carbon fiber-carbon nanotube composite modified filler with a special structural system, the conventional application defects of carbon fiber and carbon nanotube can be overcome, and the multiple properties of the sealing gasket material can be comprehensively improved. The improvement of the performance of the sealing gasket by each reinforcing component can play a synergistic enhancement effect, and the sealing gasket finally prepared has excellent wear resistance and corrosion resistance, high mechanical strength, and has good thermal conductivity and resilience, and has a long service life and good sealing effect.

Description

Technical Field

[0001] The invention relates to the field of sealing materials, and in particular to a wear-resistant and heat-resistant sealing gasket and a preparation process thereof. Background Art

[0002] Sealing gaskets are commonly used parts in the process. They are usually made of metal or non-metallic plate materials through cutting, stamping or cutting processes. They can be used for sealing connections between pipes, sealing connections between parts of machinery and equipment, etc. According to the material, they can be divided into metal sealing gaskets and non-metallic sealing gaskets.

[0003] The non-metallic sealing gasket based on polytetrafluoroethylene is a widely used sealing gasket product. Polytetrafluoroethylene has good mechanical properties and excellent corrosion resistance, high and low temperature resistance and other properties, which are very suitable for use as a sealing material. However, it also has some shortcomings, such as poor stress relaxation resistance and poor resilience, and generally requires the use of fillers to improve its performance. For example, the patent CN117050447A discloses a high-resilience creep-resistant modified polytetrafluoroethylene sealing material and its preparation method, and the polytetrafluoroethylene sealing gasket disclosed in CN116731458B and its preparation method. In addition, the polytetrafluoroethylene sealing gasket also has the defects of insufficient wear resistance and poor thermal conductivity. The insufficient wear resistance is likely to cause a reduction in the sealing effect and sealing life. The poor thermal conductivity makes it impossible to dissipate heat in time, which is easy to cause local high temperature and damage the mechanical strength, and accelerates thermal oxidation aging, which will shorten the service life of the sealing gasket. Therefore, it is still necessary to improve the comprehensive performance of the polytetrafluoroethylene-based sealing gasket to meet the needs of various application environments. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a wear-resistant and heat-resistant sealing gasket and a preparation process thereof in view of the deficiencies in the above-mentioned prior art.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is: In a first aspect of the present invention, a preparation process of a wear-resistant and heat-resistant sealing gasket is provided, comprising the following steps:

[0006] Step 1, pre-drying polytetrafluoroethylene and polyperfluoroethylene propylene;

[0007] Step 2: According to the mass percentage, 1.9-7.6% of polyperfluoroethylene propylene, 3.75-12% of carbon fiber-carbon nanotube composite modified filler and the balance of polytetrafluoroethylene are mixed and stirred;

[0008] Step 3, adding the mixture obtained in step 2 into a mold for compression molding; then sintering in an air atmosphere and cooling to room temperature to obtain a gasket blank;

[0009] Step 4: Mechanically process the gasket blank to obtain the wear-resistant and heat-resistant sealing gasket;

[0010] Wherein, the carbon fiber-carbon nanotube composite modified filler is prepared by the following method:

[0011] S1. Preparation of ZrO 2 Hybrid carbon fiber, denoted as CF-ZrO 2 ;

[0012] S2. Preparation of carbon fiber-carbon nanotube composites:

[0013] S2-1, preparing acidified carbon nanotubes, denoted as acidified CNTs;

[0014] S2-2, adding acidified CNTs, copper salt, glucose, ascorbic acid, 4-hexylresorcinol and urea into deionized water, and ultrasonically dispersing them to obtain a precursor solution A;

[0015] S2-3, CF-ZrO 2 , copper salt is added into deionized water, and ultrasonic dispersion is performed to obtain precursor solution B;

[0016] S2-4, adding the precursor solution A to the precursor solution B under stirring, ultrasonically dispersing, transferring the obtained mixture to a reaction kettle, performing a one-pot hydrothermal reaction under heating, cooling to room temperature after the reaction is completed, filtering, washing the solid product, and vacuum drying to obtain a carbon fiber-carbon nanotube composite;

[0017] S3, performing polyacrylonitrile graft coating treatment on the carbon fiber-carbon nanotube composite to obtain the carbon fiber-carbon nanotube composite modified filler, which is recorded as CF-ZrO 2 @Cu@CNTs-CDs.

[0018] Preferably, step S1 specifically comprises:

[0019] S1-1, washing the carbon fiber with deionized water and ethanol in sequence, drying, soaking in a mixed acid composed of sulfuric acid and nitric acid in a volume ratio of 2:1, stirring and refluxing at 65-80°C for 1-4h, cooling to room temperature, filtering, washing with deionized water until neutral, and vacuum drying at 90-110°C to constant weight to obtain acidified carbon fiber;

[0020] S1-2, taking 2.5-10 g of acidified carbon fiber, adding it into 100-500 mL of deionized water, and ultrasonically dispersing it for 15-60 min to obtain an acidified carbon fiber dispersion;

[0021] S1-3, prepare a zirconium oxychloride solution with a concentration of 0.05-0.2 mol / L with deionized water, add 25-100 mL of the zirconium oxychloride solution to the acidified carbon fiber dispersion, and perform ultrasonic dispersion for 2-10 minutes;

[0022] S1-4, under stirring, add 5-20% ammonia water to the product obtained in step S1-3 to adjust the pH value to 7.5-9, filter, wash the solid product with deionized water, and then calcine at 500-600°C for 1-3h to obtain ZrO 2 Hybrid carbon fiber, denoted as CF-ZrO 2 .

[0023] Preferably, the copper salt is any one of copper nitrate, copper sulfate and copper chloride.

[0024] Preferably, step S2 specifically comprises:

[0025] S2-1. Preparation of acidified carbon nanotubes:

[0026] The multi-walled carbon nanotubes are added to a mixed acid consisting of concentrated sulfuric acid and concentrated nitric acid in a volume ratio of 1:1, refluxed at 100-130°C for 2-6 hours, cooled to room temperature, filtered, washed with deionized water until neutral, and vacuum dried at 100-120°C to constant weight to obtain acidified carbon nanotubes, which are referred to as acidified CNTs;

[0027] S2-2, add 0.75-3 g of acidified CNTs, 142-570 mg of copper nitrate, 180-720 mg of glucose, 44-176 mg of ascorbic acid, 29-116 mg of 4-hexylresorcinol, and 75-300 mg of urea into 200-1000 mL of deionized water, and perform ultrasonic dispersion for 30-90 min to obtain precursor solution A;

[0028] S2-3, 1-4g CF-ZrO 2 , 322-1300 mg of copper nitrate is added to 250-1000 mL of deionized water, and ultrasonically dispersed for 15-60 min to obtain precursor solution B;

[0029] S2-4. Add precursor solution A to precursor solution B under stirring, ultrasonically disperse for 30-90 minutes, transfer the resulting mixture to a polytetrafluoroethylene-lined reactor, react at 185-220°C for 6-18 hours, cool to room temperature after the reaction, filter, wash the solid with deionized water and ethanol in turn, and then vacuum dry at 80-100°C for 6-24 hours to obtain a carbon fiber-carbon nanotube composite.

[0030] Preferably, step S2 specifically comprises:

[0031] S2-1. Preparation of acidified carbon nanotubes:

[0032] The multi-walled carbon nanotubes were added to a mixed acid consisting of concentrated sulfuric acid and concentrated nitric acid in a volume ratio of 1:1, refluxed at 120°C for 3 h, cooled to room temperature, filtered, washed with deionized water until neutral, and vacuum dried at 110°C to constant weight to obtain acidified carbon nanotubes, which were recorded as acidified CNTs.

[0033] S2-2, 1.5 g of acidified CNTs, 285 mg of copper nitrate, 360 mg of glucose, 88 mg of ascorbic acid, 58 mg of 4-hexylresorcinol, and 150 mg of urea were added to 400 mL of deionized water, and ultrasonically dispersed for 45 min to obtain precursor solution A;

[0034] S2-3, 2g CF-ZrO 2 , 665 mg of copper nitrate was added into 500 mL of deionized water, and ultrasonically dispersed for 45 min to obtain precursor solution B;

[0035] S2-4. Precursor solution A is added to precursor solution B under stirring, and ultrasonic dispersion is performed for 45 minutes. The resulting mixture is transferred to a polytetrafluoroethylene-lined reactor and reacted at 210°C for 10 hours. After the reaction is completed, it is cooled to room temperature and filtered. The solid is washed with deionized water and ethanol in sequence, and then vacuum dried at 90°C for 12 hours to obtain a carbon fiber-carbon nanotube composite.

[0036] Preferably, step S3 specifically comprises:

[0037] S3-1, adding 0.125-0.5 g of carbon fiber-carbon nanotube composite to a mixed solution consisting of 35-140 mL of ethanol and 15-60 mL of deionized water, and ultrasonically dispersing for 10-30 min;

[0038] S3-2, adding 5-20 mL of acrylonitrile and 0.04-0.16 mL of dodecanethiol to the mixture obtained in step S3-1, and ultrasonically dispersing for 15-60 min;

[0039] S3-3, heating to 50-70°C, adding 0.4-1.6 g of initiator dropwise under nitrogen protection and continuous stirring within 15-60 min, and then reacting at a constant temperature for 45-120 min. After the reaction is completed, cooling to room temperature, centrifuging, washing the solid product with deionized water, and drying at 80-100°C for 6-24 h to obtain the carbon fiber-carbon nanotube composite modified filler, recorded as CF-ZrO 2 @Cu@CNTs-CDs.

[0040] Preferably, the initiator is at least one of ammonium persulfate, potassium persulfate and ammonium sulfite.

[0041] Preferably, the preparation process of the wear-resistant and heat-resistant sealing gasket comprises the following steps:

[0042] Step 1: Pre-dry polytetrafluoroethylene and polyperfluoroethylene propylene at 90-120°C for 3-8h;

[0043] Step 2: According to the mass percentage, 1.9-7.6% of polyperfluoroethylene propylene, 3.75-12% of carbon fiber-carbon nanotube composite modified filler and the balance of polytetrafluoroethylene are added into a blender and mixed, and stirred at 500-2000 rpm for 1-4 hours;

[0044] Step 3, adding the mixture obtained in step 2 into a mold, and performing compression molding at 20-30°C and 30-55MPa, with a compression holding time of 2-8min; then sintering at 330-360°C in an air atmosphere for 2-6h, and cooling to room temperature at a rate of 10-35°C / h to obtain a gasket blank;

[0045] Step 4: Mechanically process the gasket blank according to the required specifications and dimensions to obtain the wear-resistant and heat-resistant sealing gasket.

[0046] Preferably, the preparation process of the wear-resistant and heat-resistant sealing gasket comprises the following steps:

[0047] Step 1: pre-dry polytetrafluoroethylene and polyperfluoroethylene propylene at 100°C for 5 hours;

[0048] Step 2: Add 3.8% of polyperfluoroethylene propylene, 7.5% of carbon fiber-carbon nanotube composite modified filler and the balance of polytetrafluoroethylene into a blender according to mass percentage, and stir at 1000 rpm for 2 hours;

[0049] Step 3, adding the mixture obtained in step 2 into a mold, and molding it at 25°C and 40MPa, with a molding holding time of 3min; then sintering it at 355°C for 3h in an air atmosphere, and cooling it to room temperature at a rate of 20°C / h to obtain a gasket blank;

[0050] Step 4: Mechanically process the gasket blank according to the required specifications and dimensions to obtain the wear-resistant and heat-resistant sealing gasket.

[0051] A second aspect of the present invention provides a wear-resistant and heat-resistant sealing gasket, which is prepared by the process described above.

[0052] The beneficial effects of the present invention are:

[0053] The present invention can significantly improve the tensile strength and creep resistance of the prepared sealing gasket by compounding polyperfluoroethylene propylene with polytetrafluoroethylene.

[0054] In the present invention, ZrO 2 Hybrid Carbon Fiber CF-ZrO 2The carbon fiber-carbon nanotube composite with a three-dimensional cross-linked network structure was constructed by using carbon nanotubes and carbon nanotubes as the main fillers, compounding reduced carbon dots and metal copper, and finally grafting and coating polyacrylonitrile to obtain a carbon fiber-carbon nanotube composite modified filler CF-ZrO 2 @Cu@CNTs-CDs; the CF-ZrO 2 @Cu@CNTs-CDs can comprehensively improve the mechanical properties, wear resistance, compression resilience, thermal conductivity, creep resistance and thermal oxidation aging resistance of polytetrafluoroethylene sealing gasket materials;

[0055] In the present invention, a carbon fiber-carbon nanotube composite modified filler CF-ZrO 2 @Cu@CNTs-CDs can overcome the conventional application defects of carbon fiber and carbon nanotubes, and comprehensively improve the multiple properties of sealing gasket materials. The various reinforcing components can have a synergistic enhancement effect on the improvement of sealing gasket performance. The finally prepared sealing gasket has excellent wear and corrosion resistance, high mechanical strength, and good thermal conductivity and resilience. It has a long service life and good sealing effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 The test results of the effect of the addition amount of carbon fiber-carbon nanotube composite modified filler on the wear rate of sealing gaskets;

[0057] Figure 2 The carbon fiber-carbon nanotube composite modified filler (CF-ZrO 2 @Cu@CNTs-CDs) infrared absorption spectrum;

[0058] Figure 3 CF-ZrO prepared in Example 1 2 @Cu@CNTs-CDs antioxidant performance test results;

[0059] Figure 4 The room temperature wear test results of the embodiments and comparative examples are shown;

[0060] Figure 5 The high temperature wear rate (200°C) test results of the embodiments and comparative examples;

[0061] Figure 6 The tensile strength test results of the embodiments and comparative examples are shown in FIG.

[0062] Figure 7 The compression resilience test results of the embodiments and comparative examples are shown in FIG.

[0063] Figure 8 The creep relaxation rate test results of the embodiments and comparative examples are shown in FIG.

[0064] Fig. 9 The test results of gas leakage rate of the embodiments and comparative examples are as follows;

[0065] Fig.10 The figures are the test results of the tensile strength retention rate after thermal oxidative aging of the embodiments and comparative examples. DETAILED DESCRIPTION

[0066] The present invention is further described in detail below in conjunction with embodiments so that those skilled in the art can implement the invention with reference to the description.

[0067] It should be understood that the terms such as “having”, “including” and “comprising” used herein do not exclude the existence or addition of one or more other elements or combinations thereof.

[0068] The test methods used in the following examples are conventional methods unless otherwise specified. The materials and reagents used in the following examples are all commercially available unless otherwise specified. In the following examples, if no specific conditions are specified, the experiments were carried out under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used, if the manufacturer is not specified, are all conventional products that can be purchased commercially.

[0069] The present invention provides a wear-resistant and heat-resistant sealing gasket and a preparation process thereof, the process comprising the following steps:

[0070] Step 1: Pre-dry polytetrafluoroethylene and polyperfluoroethylene propylene at 90-120°C for 3-8h;

[0071] Step 2: According to the mass percentage, 1.9-7.6% of polyperfluoroethylene propylene, 3.75-12% of carbon fiber-carbon nanotube composite modified filler and the balance of polytetrafluoroethylene are added into a blender and mixed, and stirred at 500-2000 rpm for 1-4 hours;

[0072] Step 3, adding the mixture obtained in step 2 into a mold, and performing compression molding at 20-30°C and 30-55MPa, with a compression holding time of 2-8min; then sintering at 330-360°C in an air atmosphere for 2-6h, and cooling to room temperature at a rate of 10-35°C / h to obtain a gasket blank;

[0073] Step 4: Machining the gasket blank according to the required specifications and dimensions to obtain a wear-resistant and heat-resistant sealing gasket.

[0074] In the present invention, the carbon fiber-carbon nanotube composite modified filler is prepared by the following method:

[0075] S1. Preparation of ZrO 2 Hybrid Carbon Fiber CF-ZrO 2 :

[0076] S1-1, washing the carbon fiber with deionized water and ethanol in sequence, drying, soaking in a mixed acid composed of sulfuric acid and nitric acid in a volume ratio of 2:1, stirring and refluxing at 65-80°C for 1-4h, cooling to room temperature, filtering, washing with deionized water until neutral, and vacuum drying at 90-110°C to constant weight to obtain acidified carbon fiber;

[0077] S1-2, taking 2.5-10 g of acidified carbon fiber, adding it into 100-500 mL of deionized water, and ultrasonically dispersing it for 15-60 min to obtain an acidified carbon fiber dispersion;

[0078] S1-3, prepare a zirconium oxychloride solution with a concentration of 0.05-0.2 mol / L with deionized water, add 25-100 mL of the zirconium oxychloride solution to the acidified carbon fiber dispersion, and perform ultrasonic dispersion for 2-10 minutes;

[0079] S1-4, under stirring, add 5-20% ammonia water to the product obtained in step S1-3 to adjust the pH value to 7.5-9, filter, wash the solid product with deionized water, and then calcine at 500-600°C for 1-3h to obtain ZrO 2 Hybrid carbon fiber, denoted as CF-ZrO 2 .

[0080] S2. Preparation of carbon fiber-carbon nanotube composites:

[0081] S2-1, preparation of acidified carbon nanotubes:

[0082] The multi-walled carbon nanotubes are added to a mixed acid consisting of concentrated sulfuric acid and concentrated nitric acid in a volume ratio of 1:1, refluxed at 100-130°C for 2-6 hours, cooled to room temperature, filtered, washed with deionized water until neutral, and vacuum dried at 100-120°C to constant weight to obtain acidified carbon nanotubes, which are referred to as acidified CNTs;

[0083] S2-2, add 0.75-3 g of acidified CNTs, 142-570 mg of copper nitrate, 180-720 mg of glucose, 44-176 mg of ascorbic acid, 29-116 mg of 4-hexylresorcinol, and 75-300 mg of urea into 200-1000 mL of deionized water, and perform ultrasonic dispersion for 30-90 min to obtain precursor solution A;

[0084] S2-3, 1-4g CF-ZrO 2 , 322-1300 mg of copper nitrate is added to 250-1000 mL of deionized water, and ultrasonically dispersed for 15-60 min to obtain precursor solution B;

[0085] S2-4. Add precursor solution A to precursor solution B under stirring, ultrasonically disperse for 30-90 minutes, transfer the resulting mixture to a polytetrafluoroethylene-lined reactor, react at 185-220°C for 6-18 hours, cool to room temperature after the reaction, filter, wash the solid with deionized water and ethanol in turn, and then vacuum dry at 80-100°C for 6-24 hours to obtain a carbon fiber-carbon nanotube composite.

[0086] S3, performing polyacrylonitrile graft coating treatment on the carbon fiber-carbon nanotube composite to obtain a carbon fiber-carbon nanotube composite modified filler CF-ZrO 2 @Cu@CNTs-CDs:

[0087] S3-1, adding 0.125-0.5 g of carbon fiber-carbon nanotube composite to a mixed solution consisting of 35-140 mL of ethanol and 15-60 mL of deionized water, and ultrasonically dispersing for 10-30 min;

[0088] S3-2, adding 5-20 mL of acrylonitrile and 0.04-0.16 mL of dodecanethiol to the mixture obtained in step S3-1, and ultrasonically dispersing for 15-60 min;

[0089] S3-3, heating to 50-70°C, adding 0.4-1.6 g of initiator dropwise under nitrogen protection and continuous stirring within 15-60 min, and then reacting at a constant temperature for 45-120 min. After the reaction is completed, cooling to room temperature, centrifuging, washing the solid product with deionized water, and drying at 80-100°C for 6-24 h to obtain a carbon fiber-carbon nanotube composite modified filler, recorded as CF-ZrO 2 @Cu@CNTs-CDs.

[0090] In a preferred embodiment, the initiator is at least one of ammonium persulfate, potassium persulfate, and ammonium sulfite.

[0091] The main mechanism of the present invention is described below to facilitate understanding of the present invention.

[0092] Polytetrafluoroethylene has excellent corrosion resistance, high and low temperature resistance and other properties, but when used as a sealing gasket material, it still has defects such as insufficient wear resistance, poor thermal conductivity, poor resilience, poor creep resistance, and low load-bearing capacity. Filling and modifying with certain materials is currently a more commonly used method to improve its performance (Zhou Bo, Chen Ye. Preparation and performance study of fiber-modified polytetrafluoroethylene sealing materials [J]. Lubrication and Sealing, 2009, 34(6): 5. DOI: 10.3969 / j.issn.0254-0150.2009.06.019.).

[0093] In addition, although polytetrafluoroethylene has good high temperature resistance, as a polymer, it still inevitably needs to face the problem of thermal oxidative decomposition, especially when used as a sealing gasket material in harsh working environments such as high temperature, high pressure, and vibration. This problem will become more serious, causing the aging of polytetrafluoroethylene to accelerate, resulting in reduced sealing effect and shortening the service life of the sealing gasket material. Therefore, in order to improve the comprehensive performance and application effect of polytetrafluoroethylene sealing gasket materials, further slowing down the thermal oxidative aging of polytetrafluoroethylene can be an effective means.

[0094] Since polyperfluoroethylene propylene has high impact strength, creep resistance and flexibility that are better than polytetrafluoroethylene, in the present invention, by compounding polyperfluoroethylene propylene with polytetrafluoroethylene, the tensile resistance and creep resistance of the sealing gasket material can be significantly improved.

[0095] In the present invention, ZrO 2 Hybrid Carbon Fiber CF-ZrO 2 The carbon fiber-carbon nanotube composite with a three-dimensional cross-linked network structure was constructed by using carbon nanotubes and carbon nanotubes as the main fillers, compounding reduced carbon dots and metal copper, and finally grafting and coating polyacrylonitrile to obtain a carbon fiber-carbon nanotube composite modified filler CF-ZrO 2 @Cu@CNTs-CDs;CF-ZrO 2 @Cu@CNTs-CDs can comprehensively improve the mechanical properties, wear resistance, compression resilience, thermal conductivity, creep resistance and thermal oxidation aging resistance of polytetrafluoroethylene sealing gasket materials. The following is a detailed description of its preparation method and mechanism of action.

[0096] 1. Preparation mechanism:

[0097] 1. The present invention firstly performs acid oxidation treatment on carbon fibers and carbon nanotubes respectively, and introduces abundant carboxyl functional groups on the surface to improve their dispersion performance and facilitate subsequent treatment;

[0098] 2. For acidified carbon fiber, a large amount of nano ZrO is grafted on its surface through co-precipitation, calcination and other processes. 2 Particles, ZrO 2 Hybrid carbon fiber: CF-ZrO 2 ;

[0099] 3. Then use a one-pot hydrothermal method to CF-ZrO 2 The carbon fiber-carbon nanotube composite was synthesized by using acidified CNTs as the main filler, copper ions as the crosslinking component, glucose, ascorbic acid, 4-hexylresorcinol and urea as carbon dot raw materials: CF-ZrO 2 @Cu@CNTs-CDs;

[0100] In this process, the carbon dot raw material, acidified CNTs and some copper ions are first mixed to obtain precursor solution A. The copper ions can connect with functional groups such as carboxyl groups on the acidified CNTs through coordination, electrostatic adsorption and other effects, and the carbon dot raw material is attached to the surface of the acidified CNTs and its internal lumen; CF-ZrO 2 Then it is mixed with another part of copper ions to obtain precursor solution B, CF-ZrO 2 There are also oxygen-containing functional groups such as carboxyl groups, which can connect copper ions;

[0101] 4. After mixing precursor solution A with precursor solution B, copper ions play a role in cross-linking, making CF-ZrO 2 Interpenetrating and cross-linking with acidified CNTs to form a three-dimensional network structure. Then, under the hydrothermal reaction, copper ions form copper oxides (copper oxides are mainly CuO), which become strong network connection points;

[0102] Among them, 4-hexylresorcinol and ascorbic acid both have good reducing properties. The two are mixed as carbon dot raw materials and finally prepared on CF-ZrO by hydrothermal method. 2 The carbon dots synthesized in situ on acidified CNTs also showed good reducibility and inherited the characteristics of the precursor materials.

[0103] 5. Finally, the obtained carbon fiber-carbon nanotube composite is grafted and coated with polyacrylonitrile to finally obtain a carbon fiber-carbon nanotube composite modified filler CF-ZrO 2 @Cu@CNTs-CDs.

[0104] 2. Reinforcement mechanism:

[0105] Carbon fiber can improve load-bearing capacity, wear resistance, high temperature resistance, stiffness, corrosion resistance and heat resistance. However, when used in sealing gasket materials, it is limited by the thickness of the gasket and is not suitable for carbon fibers with an aspect ratio of more than 100 μm. The improvement effect on tensile strength is limited (Zhou Bo, Chen Ye. Preparation and performance study of fiber-modified polytetrafluoroethylene sealing gasket materials [J]. Lubrication and Sealing, 2009, 34 (6): 5. DOI: 10.3969 / j.issn.0254-0150.2009.06.019.).

[0106] Carbon nanotubes have excellent mechanical properties, can reduce the friction coefficient, greatly improve wear resistance, have super strong mechanical properties, can strengthen the matrix, reduce the adhesion and plowing of materials during friction, promote the formation of transfer film, and reduce the friction coefficient. In addition, carbon nanotubes have strong thermal conductivity, which can significantly improve the thermal conductivity of polytetrafluoroethylene sealing gasket materials.

[0107] However, in actual applications, due to the nanostructure and other characteristics of carbon fibers and carbon nanotubes, it is difficult to achieve uniform dispersion of both in the polytetrafluoroethylene matrix, and the interface bonding strength between them and the polytetrafluoroethylene matrix is ​​low, which makes it difficult for them to fully exert their respective reinforcement effects. It is even easy for the curling and agglomeration of carbon fibers and carbon nanotubes to cause stress concentration points and lose the mechanical properties or other properties of the matrix.

[0108] The present invention uses carbon fiber and carbon nanotube to construct a carbon fiber-carbon nanotube composite modified filler CF-ZrO 2 @Cu@CNTs-CDs can at least overcome the above-mentioned defects and achieve a synergistic enhancement effect in improving the comprehensive performance of sealing gasket materials.

[0109] (1) The carbon fiber plays a role in bearing the external load in the sealing gasket material system, while the surrounding polymer matrix plays a role in transmitting the load. The bonding strength between the carbon fiber and the matrix at the interface directly affects the performance of the sealing gasket material. 2 In hybrid carbon fiber, nano-scale ZrO is grafted onto the surface of carbon fiber. 2 particles, which can increase its surface area, and ZrO 2 The particles can serve as anchor points between the matrix and the carbon fibers, significantly improving the interfacial bonding strength; these anchor points can disperse the stress of the matrix, thereby improving the bearing capacity of the matrix; and ZrO 2 The pulling and other forces of the particles on the carbon fibers can also reduce their curling;

[0110] In addition, ZrO 2 The particles have high chemical stability, high melting point, high hardness, high wear resistance, and can improve surface roughness and reduce friction coefficient; ZrO 2 The hybridization can further improve the wear resistance and thermal stability of carbon fiber, and ultimately act on the sealing gasket material.

[0111] (2) Under the interaction of copper ions (mainly Cu oxides), ZrO 2 The hybrid carbon fibers and carbon nanotubes are cross-linked and form a three-dimensional network structure after a hydrothermal reaction. The copper ions mainly form copper oxide and serve as the connection points of the three-dimensional network structure, which can improve the strength of the network structure. The formation of the three-dimensional network structure can greatly enhance the improvement effect of carbon fibers and carbon nanotubes on the mechanical strength of the matrix, and can obtain an improvement effect that is significantly better than that when carbon fibers and carbon nanotubes are simply mixed and added; the three-dimensional network structure can significantly increase the resilience of the matrix, thereby improving the compression resilience performance of the sealing gasket material.

[0112] At the same time, the three-dimensional network structure can also reduce the curling and agglomeration phenomena that exist when carbon fibers and carbon nanotubes are added in a one-dimensional state.

[0113] Carbon nanotubes have strong thermal conductivity and can significantly improve the thermal conductivity of sealing gasket materials. Carbon fibers also have good thermal conductivity, and the formation of a three-dimensional network structure can greatly enhance the thermal conductivity of sealing gasket materials. The improvement of thermal conductivity can more effectively conduct friction heat to surrounding components and wear parts, thereby improving the creep resistance and dimensional stability of sealing gasket materials, and also improving their heat resistance.

[0114] (3) In CF-ZrO 2 In the @Cu@CNTs-CDs system, reduced carbon dots can play at least the following roles:

[0115] (3-1) Carbon dots themselves are nano-microsphere structures and can also play a certain role in physical friction reduction;

[0116] (3-2) Carbon dots can interact with ZrO 2 The effect is similar to that of hybrid carbon fibers, that is, carbon dots can also serve as anchor points between the matrix and carbon nanotubes to enhance the interfacial bonding strength; carbon dots as anchor points can disperse the stress of the matrix, thereby enhancing the bearing capacity of the matrix;

[0117] (3-3) The carbon dots have inherited the antioxidant properties of the precursor material and exhibited good reducibility. Under the action of local high temperature and pressure generated by friction, tribochemical reactions occurred. The reduced carbon dots were able to make CF-ZrO 2 The copper oxide in the @Cu@CNTs-CDs system is efficiently reduced to elemental copper and selectively enriched into a copper layer, forming a copper transfer film with anti-wear and wear-reducing effects at the friction interface. The transfer film can protect the substrate from cutting of the grinding surface and other effects, and with the help of the self-lubricating properties of elemental copper, it can reduce the adhesive wear and abrasive wear between the friction contact surfaces. This action principle follows the self-repairing principle of friction film formation (Ou Zhongwen, Xu Binshi, Ma Shining, et al. Self-repairing principle of wear parts and self-repairing design concept of nano-lubricating materials [J]. Surface Technology, 2001, 30(6): 4. DOI: 10.3969 / j.issn.1001-3660.2001.06.017.).

[0118] (3-4) When oxygen enters the polymer system, it generates oxygen-containing free radicals to attack the polymer chain, causing polymer chain degradation. 2 The reduced carbon dots in @Cu@CNTs-CDs can capture and remove oxygen free radicals with strong oxidizing ability (such as hydroxyl free radicals ·OH, singlet oxygen 1 O 2The antioxidant properties of carbon dots can slow down the thermal oxidation decomposition of polymers (polytetrafluoroethylene, polyacrylonitrile, etc.) in sealing gasket materials, especially when used in harsh environments such as high temperature and high oxygen content, thereby extending the service life of the sealing gasket material and ensuring the sealing effect. 2 In the @Cu@CNTs-CDs system, some carbon dots exist in the tubular structure of carbon nanotubes, which provides certain protection and "slow-release" effects on the carbon dots, enabling the carbon dots to provide long-lasting reduction ability, thereby being able to continue to effectively slow down the thermal oxygen decomposition of the sealing gasket material during longer use.

[0119] (4) The role of polyacrylonitrile coating:

[0120] (4-1) Polyacrylonitrile and polytetrafluoroethylene have good compatibility (Song Mingbin, Zhang Lixiang, Huang Wenhao, et al. Structural characterization and properties of polyacrylonitrile filled polytetrafluoroethylene composites [J]. Polymer Materials Science and Engineering, 2007, 23(1):5. DOI:10.3321 / j.issn:1000-7555.2007.01.023.), and its coating effect can promote the CF-ZrO 2 @Cu@CNTs-CDs are evenly dispersed in the polytetrafluoroethylene system, and polyacrylonitrile can improve the compatibility between polytetrafluoroethylene and carbon fiber-carbon nanotube composite modified filler, enhance the interface connection strength, and overcome the application difficulties of carbon fiber and carbon nanotubes as fillers in polytetrafluoroethylene in conventional technology.

[0121] (4-2) After being compounded into the sealing gasket material system, polyacrylonitrile itself can increase the glass transition temperature of polytetrafluoroethylene and enhance its heat resistance.

[0122] Therefore, in the present invention, by constructing a carbon fiber-carbon nanotube composite modified filler with a special structural system, multiple properties of the sealing gasket material can be comprehensively improved, and the various reinforcing components can have a synergistic enhancement effect on the improvement of the sealing gasket performance. The sealing gasket finally prepared has excellent wear and corrosion resistance, high mechanical strength, and good thermal conductivity and resilience. It has a long service life and good sealing effect.

[0123] The above is the overall concept of the present invention, and detailed embodiments and comparative examples are provided below on the basis of the overall concept of the present invention to further illustrate the present invention.

[0124] Main raw material sources

[0125] Polytetrafluoroethylene, Daikin L-5, Japan, purchased from Tetrafluoro New Materials (Suzhou) Co., Ltd.;

[0126] Fluorinated ethylene propylene (FEP), Japan Daikin NP101, purchased from Shanghai Juyilong Plastic Co., Ltd.;

[0127] Carbon fiber, median length 80 μm, purchased from Hangzhou Gaoke Composite Materials Co., Ltd.;

[0128] Multi-walled carbon nanotubes, with an average length of 50 μm and a tube diameter of 10-20 nm, were purchased from Suzhou Kaifa New Materials Technology Co., Ltd.;

[0129] Acrylonitrile, Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0130] Ammonium persulfate, Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0131] Dodecanethiol, Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0132] The remaining raw materials not specifically described are all commercially available products known to those skilled in the art.

[0133] Example 1

[0134] A wear-resistant and heat-resistant sealing gasket, the preparation process of which comprises the following steps:

[0135] Step 1: pre-dry polytetrafluoroethylene and polyperfluoroethylene propylene at 100°C for 5 hours;

[0136] Step 2: Add 3.8% of polyperfluoroethylene propylene, 7.5% of carbon fiber-carbon nanotube composite modified filler and the balance of polytetrafluoroethylene into a blender according to mass percentage, and stir at room temperature and 1000 rpm for 2 hours;

[0137] Step 3, adding the mixture obtained in step 2 into a mold, and molding it at 25°C and 40MPa, with a molding holding time of 3min; then sintering it at 355°C for 3h in an air atmosphere, and cooling it to room temperature at a rate of 20°C / h to obtain a gasket blank;

[0138] Step 4: Machining the gasket blank according to the required specifications and dimensions to obtain a wear-resistant and heat-resistant sealing gasket.

[0139] In this embodiment, the carbon fiber-carbon nanotube composite modified filler is prepared by the following method:

[0140] S1. Preparation of ZrO 2 Hybrid Carbon Fiber CF-ZrO 2 :

[0141] S1-1, washing the carbon fiber with deionized water and ethanol in sequence, drying, soaking in a mixed acid composed of sulfuric acid and nitric acid in a volume ratio of 2:1, stirring and refluxing at 75°C for 2h, cooling to room temperature, filtering, washing with deionized water until neutral, and vacuum drying at 100°C to constant weight to obtain acidified carbon fiber;

[0142] S1-2, taking 5 g of acidified carbon fiber, adding it into 200 mL of deionized water, and ultrasonically dispersing it for 30 min to obtain an acidified carbon fiber dispersion;

[0143] S1-3, prepare a zirconium oxychloride solution with a concentration of 0.1 mol / L with deionized water, add 50 mL of the zirconium oxychloride solution to the acidified carbon fiber dispersion, and perform ultrasonic dispersion for 5 minutes;

[0144] S1-4, under stirring, add 10% ammonia water to the product obtained in step S1-3 to adjust the pH value to 8, filter, wash the solid product with deionized water, and then roast at 550°C for 1.5h to obtain ZrO 2 Hybrid carbon fiber, denoted as CF-ZrO 2 .

[0145] S2. Preparation of carbon fiber-carbon nanotube composites:

[0146] S2-1. Preparation of acidified carbon nanotubes:

[0147] The multi-walled carbon nanotubes were added to a mixed acid consisting of concentrated sulfuric acid and concentrated nitric acid in a volume ratio of 1:1, refluxed at 120°C for 3 h, cooled to room temperature, filtered, washed with deionized water until neutral, and vacuum dried at 110°C to constant weight to obtain acidified carbon nanotubes, which were recorded as acidified CNTs.

[0148] S2-2, 1.5 g of acidified CNTs, 285 mg of copper nitrate, 360 mg of glucose, 88 mg of ascorbic acid, 58 mg of 4-hexylresorcinol, and 150 mg of urea were added to 400 mL of deionized water, and ultrasonically dispersed for 45 min to obtain precursor solution A;

[0149] S2-3, 2g CF-ZrO 2 , 665 mg of copper nitrate was added into 500 mL of deionized water, and ultrasonically dispersed for 45 min to obtain precursor solution B;

[0150] S2-4. Precursor solution A is added to precursor solution B under stirring, and ultrasonic dispersion is performed for 45 minutes. The resulting mixture is transferred to a polytetrafluoroethylene-lined reactor and reacted at 210°C for 10 hours. After the reaction is completed, it is cooled to room temperature and filtered. The solid is washed with deionized water and ethanol in sequence, and then vacuum dried at 90°C for 12 hours to obtain a carbon fiber-carbon nanotube composite.

[0151] S3, performing polyacrylonitrile graft coating treatment on the carbon fiber-carbon nanotube composite to obtain a carbon fiber-carbon nanotube composite modified filler CF-ZrO 2 @Cu@CNTs-CDs:

[0152] S3-1, taking 0.25g of carbon fiber-carbon nanotube composite, adding it into a mixed solution consisting of 70mL of ethanol and 30mL of deionized water, and ultrasonically dispersing it for 15min;

[0153] S3-2, adding 10 mL of acrylonitrile and 0.08 mL of dodecanethiol to the mixture obtained in step S3-1, and ultrasonically dispersing for 30 min;

[0154] S3-3, the temperature was raised to 60°C, 0.8 g of ammonium persulfate was added dropwise under nitrogen protection and continuous stirring within 30 min, and then the reaction was continued at a constant temperature for 75 min. After the reaction was completed, the mixture was cooled to room temperature and centrifuged. The solid product was washed with deionized water and dried at 90°C for 12 h to obtain a carbon fiber-carbon nanotube composite modified filler, which was recorded as CF-ZrO 2 @Cu@CNTs-CDs.

[0155] Example 2

[0156] A wear-resistant and heat-resistant sealing gasket, the preparation process of which comprises the following steps:

[0157] Step 1: pre-dry polytetrafluoroethylene and polyperfluoroethylene propylene at 100°C for 5 hours;

[0158] Step 2: Add 3.8% of polyperfluoroethylene propylene, 7.2% of carbon fiber-carbon nanotube composite modified filler and the remaining amount of polytetrafluoroethylene into a blender according to mass percentage, and stir at room temperature and 1000 rpm for 2 hours;

[0159] Step 3, adding the mixture obtained in step 2 into a mold, and molding it at 25°C and 40MPa, with a molding holding time of 3min; then sintering it at 350°C in an air atmosphere for 3.5h, and cooling it to room temperature at a rate of 20°C / h to obtain a gasket blank;

[0160] Step 4: Machining the gasket blank according to the required specifications and dimensions to obtain a wear-resistant and heat-resistant sealing gasket.

[0161] In this embodiment, the carbon fiber-carbon nanotube composite modified filler is prepared by the following method:

[0162] S1. Preparation of ZrO 2 Hybrid Carbon Fiber CF-ZrO 2 :

[0163] S1-1, washing the carbon fiber with deionized water and ethanol in sequence, drying, soaking in a mixed acid composed of sulfuric acid and nitric acid in a volume ratio of 2:1, stirring and refluxing at 75°C for 2h, cooling to room temperature, filtering, washing with deionized water until neutral, and vacuum drying at 100°C to constant weight to obtain acidified carbon fiber;

[0164] S1-2, taking 5 g of acidified carbon fiber, adding it into 200 mL of deionized water, and ultrasonically dispersing it for 30 min to obtain an acidified carbon fiber dispersion;

[0165] S1-3, prepare a zirconium oxychloride solution with a concentration of 0.1 mol / L with deionized water, add 50 mL of the zirconium oxychloride solution to the acidified carbon fiber dispersion, and perform ultrasonic dispersion for 5 minutes;

[0166] S1-4, under stirring, add 10% ammonia water to the product obtained in step S1-3 to adjust the pH value to 8, filter, wash the solid product with deionized water, and then roast at 550°C for 1.5h to obtain ZrO 2 Hybrid carbon fiber, denoted as CF-ZrO 2 .

[0167] S2. Preparation of carbon fiber-carbon nanotube composites:

[0168] S2-1. Preparation of acidified carbon nanotubes:

[0169] The multi-walled carbon nanotubes were added to a mixed acid consisting of concentrated sulfuric acid and concentrated nitric acid in a volume ratio of 1:1, refluxed at 120°C for 3 h, cooled to room temperature, filtered, washed with deionized water until neutral, and vacuum dried at 110°C to constant weight to obtain acidified carbon nanotubes, which were recorded as acidified CNTs.

[0170] S2-2, 1.5 g of acidified CNTs, 285 mg of copper nitrate, 360 mg of glucose, 88 mg of ascorbic acid, 58 mg of 4-hexylresorcinol, and 150 mg of urea were added to 400 mL of deionized water, and ultrasonically dispersed for 45 min to obtain precursor solution A;

[0171] S2-3, 2g CF-ZrO 2 , 665 mg of copper nitrate was added into 500 mL of deionized water, and ultrasonically dispersed for 45 min to obtain precursor solution B;

[0172] S2-4. Precursor solution A is added to precursor solution B under stirring, and ultrasonic dispersion is performed for 45 minutes. The resulting mixture is transferred to a polytetrafluoroethylene-lined reactor and reacted at 210°C for 10 hours. After the reaction is completed, it is cooled to room temperature and filtered. The solid is washed with deionized water and ethanol in sequence, and then vacuum dried at 90°C for 12 hours to obtain a carbon fiber-carbon nanotube composite.

[0173] S3, performing polyacrylonitrile graft coating treatment on the carbon fiber-carbon nanotube composite to obtain a carbon fiber-carbon nanotube composite modified filler CF-ZrO 2 @Cu@CNTs-CDs:

[0174] S3-1, taking 0.28g of carbon fiber-carbon nanotube composite, adding it into a mixed solution consisting of 70mL of ethanol and 30mL of deionized water, and ultrasonically dispersing it for 15min;

[0175] S3-2, adding 10 mL of acrylonitrile and 0.08 mL of dodecanethiol to the mixture obtained in step S3-1, and ultrasonically dispersing for 30 min;

[0176] S3-3, the temperature was raised to 60°C, 0.8 g of ammonium persulfate was added dropwise under nitrogen protection and continuous stirring within 30 min, and then the reaction was continued at a constant temperature for 75 min. After the reaction was completed, the mixture was cooled to room temperature and centrifuged. The solid product was washed with deionized water and dried at 90°C for 12 h to obtain a carbon fiber-carbon nanotube composite modified filler, which was recorded as CF-ZrO 2 @Cu@CNTs-CDs.

[0177] Example 3

[0178] A wear-resistant and heat-resistant sealing gasket, the preparation process of which comprises the following steps:

[0179] Step 1: pre-dry polytetrafluoroethylene and polyperfluoroethylene propylene at 100°C for 5 hours;

[0180] Step 2: Add 3.8% of polyperfluoroethylene propylene, 7.5% of carbon fiber-carbon nanotube composite modified filler and the balance of polytetrafluoroethylene into a blender according to mass percentage, and stir at room temperature and 1000 rpm for 2 hours;

[0181] Step 3, adding the mixture obtained in step 2 into a mold, and performing compression molding at 25°C and 40MPa, with a compression holding time of 3min; then sintering at 360°C for 2.5h in an air atmosphere, and cooling to room temperature at a rate of 20°C / h to obtain a gasket blank;

[0182] Step 4: Machining the gasket blank according to the required specifications and dimensions to obtain a wear-resistant and heat-resistant sealing gasket.

[0183] In this embodiment, the carbon fiber-carbon nanotube composite modified filler is prepared by the following method:

[0184] S1. Preparation of ZrO 2 Hybrid Carbon Fiber CF-ZrO 2 :

[0185] S1-1, washing the carbon fiber with deionized water and ethanol in sequence, drying, soaking in a mixed acid composed of sulfuric acid and nitric acid in a volume ratio of 2:1, stirring and refluxing at 75°C for 2h, cooling to room temperature, filtering, washing with deionized water until neutral, and vacuum drying at 100°C to constant weight to obtain acidified carbon fiber;

[0186] S1-2, taking 5 g of acidified carbon fiber, adding it into 200 mL of deionized water, and ultrasonically dispersing it for 30 min to obtain an acidified carbon fiber dispersion;

[0187] S1-3, prepare a zirconium oxychloride solution with a concentration of 0.1 mol / L with deionized water, add 50 mL of the zirconium oxychloride solution to the acidified carbon fiber dispersion, and perform ultrasonic dispersion for 5 minutes;

[0188] S1-4, under stirring, add 10% ammonia water to the product obtained in step S1-3 to adjust the pH value to 8, filter, wash the solid product with deionized water, and then roast at 550°C for 1.5h to obtain ZrO 2 Hybrid carbon fiber, denoted as CF-ZrO 2 .

[0189] S2. Preparation of carbon fiber-carbon nanotube composites:

[0190] S2-1. Preparation of acidified carbon nanotubes:

[0191] The multi-walled carbon nanotubes were added to a mixed acid consisting of concentrated sulfuric acid and concentrated nitric acid in a volume ratio of 1:1, refluxed at 120°C for 3 h, cooled to room temperature, filtered, washed with deionized water until neutral, and vacuum dried at 110°C to constant weight to obtain acidified carbon nanotubes, which were recorded as acidified CNTs.

[0192] S2-2, 1.5 g of acidified CNTs, 285 mg of copper nitrate, 360 mg of glucose, 88 mg of ascorbic acid, 58 mg of 4-hexylresorcinol, and 150 mg of urea were added to 400 mL of deionized water, and ultrasonically dispersed for 45 min to obtain precursor solution A;

[0193] S2-3, 2g CF-ZrO 2 , 665 mg of copper nitrate was added into 500 mL of deionized water, and ultrasonically dispersed for 45 min to obtain precursor solution B;

[0194] S2-4. Precursor solution A is added to precursor solution B under stirring, and ultrasonic dispersion is performed for 45 minutes. The resulting mixture is transferred to a polytetrafluoroethylene-lined reactor and reacted at 210°C for 10 hours. After the reaction is completed, it is cooled to room temperature and filtered. The solid is washed with deionized water and ethanol in sequence, and then vacuum dried at 90°C for 12 hours to obtain a carbon fiber-carbon nanotube composite.

[0195] S3, performing polyacrylonitrile graft coating treatment on the carbon fiber-carbon nanotube composite to obtain a carbon fiber-carbon nanotube composite modified filler CF-ZrO 2 @Cu@CNTs-CDs:

[0196] S3-1, taking 0.3 g of carbon fiber-carbon nanotube composite, adding it to a mixed solution consisting of 70 mL of ethanol and 30 mL of deionized water, and ultrasonically dispersing it for 15 min;

[0197] S3-2, adding 10 mL of acrylonitrile and 0.08 mL of dodecanethiol to the mixture obtained in step S3-1, and ultrasonically dispersing for 30 min;

[0198] S3-3, the temperature was raised to 60°C, 0.8 g of ammonium persulfate was added dropwise under nitrogen protection and continuous stirring within 30 min, and then the reaction was continued at a constant temperature for 75 min. After the reaction was completed, the mixture was cooled to room temperature and centrifuged. The solid product was washed with deionized water and dried at 90°C for 12 h to obtain a carbon fiber-carbon nanotube composite modified filler, which was recorded as CF-ZrO 2 @Cu@CNTs-CDs.

[0199] Comparative Example 1

[0200] A wear-resistant and heat-resistant sealing gasket, the preparation process of which comprises the following steps:

[0201] Step 1: pre-dry polytetrafluoroethylene and polyperfluoroethylene propylene at 100°C for 5 hours;

[0202] Step 2: Add 3.8% of polyperfluoroethylene propylene and the rest of polytetrafluoroethylene into a blender according to the mass percentage, and stir at room temperature and 1000 rpm for 2 hours;

[0203] Step 3, adding the mixture obtained in step 2 into a mold, and molding it at 25°C and 40MPa, with a molding holding time of 3min; then sintering it at 355°C for 3h in an air atmosphere, and cooling it to room temperature at a rate of 20°C / h to obtain a gasket blank;

[0204] Step 4: Machining the gasket blank according to the required specifications and dimensions to obtain a wear-resistant and heat-resistant sealing gasket.

[0205] Comparative Example 2

[0206] This example is basically the same as Example 1, except that the carbon fiber-carbon nanotube composite modified filler in this example is prepared by the following method:

[0207] S1. Preparation of acidified carbon fibers:

[0208] The carbon fiber was first washed with deionized water and ethanol in sequence, dried, immersed in a mixed acid composed of sulfuric acid and nitric acid in a volume ratio of 2:1, stirred and refluxed at 75°C for 2h, cooled to room temperature, filtered, washed with deionized water until neutral, and vacuum dried at 100°C to constant weight to obtain acidified carbon fiber;

[0209] S2. Preparation of carbon fiber-carbon nanotube composites:

[0210] S2-1, preparation of acidified carbon nanotubes:

[0211] The multi-walled carbon nanotubes were added to a mixed acid consisting of concentrated sulfuric acid and concentrated nitric acid in a volume ratio of 1:1, refluxed at 120°C for 3 h, cooled to room temperature, filtered, washed with deionized water until neutral, and vacuum dried at 110°C to constant weight to obtain acidified carbon nanotubes, which were recorded as acidified CNTs.

[0212] S2-2, 1.5 g of acidified CNTs, 285 mg of copper nitrate, 360 mg of glucose, 88 mg of ascorbic acid, 58 mg of 4-hexylresorcinol, and 150 mg of urea were added to 400 mL of deionized water, and ultrasonically dispersed for 45 min to obtain precursor solution A;

[0213] S2-3, adding 2 g of acidified carbon fiber and 665 mg of copper nitrate into 500 mL of deionized water, and ultrasonically dispersing for 45 min to obtain precursor solution B;

[0214] S2-4. Precursor solution A is added to precursor solution B under stirring, and ultrasonic dispersion is performed for 45 minutes. The resulting mixture is transferred to a polytetrafluoroethylene-lined reactor and reacted at 210°C for 10 hours. After the reaction is completed, it is cooled to room temperature and filtered. The solid is washed with deionized water and ethanol in sequence, and then vacuum dried at 90°C for 12 hours to obtain a carbon fiber-carbon nanotube composite.

[0215] S3, performing polyacrylonitrile graft coating treatment on the carbon fiber-carbon nanotube composite to obtain a carbon fiber-carbon nanotube composite modified filler CF-ZrO 2 @Cu@CNTs-CDs, the specific steps are the same as those in Example 1.

[0216] Comparative Example 3

[0217] This example is basically the same as Example 1, except that the carbon fiber-carbon nanotube composite modified filler in this example is prepared by the following method:

[0218] S1. Preparation of ZrO 2 Hybrid Carbon Fiber CF-ZrO 2 , the specific steps are the same as those in Example 1;

[0219] S2. Preparation of carbon fiber-carbon nanotube composites:

[0220] S2-1. Preparation of acidified carbon nanotubes:

[0221] The multi-walled carbon nanotubes were added to a mixed acid consisting of concentrated sulfuric acid and concentrated nitric acid in a volume ratio of 1:1, refluxed at 120°C for 3 h, cooled to room temperature, filtered, washed with deionized water until neutral, and vacuum dried at 110°C to constant weight to obtain acidified carbon nanotubes, which were recorded as acidified CNTs.

[0222] S2-2, 1.5 g of acidified CNTs, 360 mg of glucose, 88 mg of ascorbic acid, 58 mg of 4-hexylresorcinol, and 150 mg of urea were added to 400 mL of deionized water, and ultrasonically dispersed for 45 min to obtain precursor solution A;

[0223] S2-3, 2g CF-ZrO 2 Add into 500 mL of deionized water and disperse by ultrasonic for 45 min to obtain precursor solution B;

[0224] S2-4. Precursor solution A is added to precursor solution B under stirring, and ultrasonic dispersion is performed for 45 minutes. The resulting mixture is transferred to a polytetrafluoroethylene-lined reactor and reacted at 210°C for 10 hours. After the reaction is completed, it is cooled to room temperature and filtered. The solid is washed with deionized water and ethanol in sequence, and then vacuum dried at 90°C for 12 hours to obtain a carbon fiber-carbon nanotube composite.

[0225] S3, performing polyacrylonitrile graft coating treatment on the carbon fiber-carbon nanotube composite to obtain a carbon fiber-carbon nanotube composite modified filler CF-ZrO 2 @Cu@CNTs-CDs, the specific steps are the same as those in Example 1.

[0226] Comparative Example 4

[0227] This example is basically the same as Example 1, except that the carbon fiber-carbon nanotube composite modified filler in this example is prepared by the following method:

[0228] S1. Preparation of ZrO 2 Hybrid Carbon Fiber CF-ZrO 2 , the specific steps are the same as those in Example 1;

[0229] S2. Preparation of carbon fiber-carbon nanotube composites:

[0230] S2-1. Preparation of acidified carbon nanotubes:

[0231] The multi-walled carbon nanotubes were added to a mixed acid consisting of concentrated sulfuric acid and concentrated nitric acid in a volume ratio of 1:1, refluxed at 120°C for 3 h, cooled to room temperature, filtered, washed with deionized water until neutral, and vacuum dried at 110°C to constant weight to obtain acidified carbon nanotubes, which were recorded as acidified CNTs.

[0232] S2-2, 1.5 g of acidified CNTs and 285 mg of copper nitrate were added to 400 mL of deionized water, and ultrasonically dispersed for 45 min to obtain precursor solution A;

[0233] S2-3, 2g CF-ZrO 2 , 665 mg of copper nitrate was added into 500 mL of deionized water, and ultrasonically dispersed for 45 min to obtain precursor solution B;

[0234] S2-4. Precursor solution A is added to precursor solution B under stirring, and ultrasonic dispersion is performed for 45 minutes. The resulting mixture is transferred to a polytetrafluoroethylene-lined reactor and reacted at 210°C for 10 hours. After the reaction is completed, it is cooled to room temperature and filtered. The solid is washed with deionized water and ethanol in sequence, and then vacuum dried at 90°C for 12 hours to obtain a carbon fiber-carbon nanotube composite.

[0235] S3, performing polyacrylonitrile graft coating treatment on the carbon fiber-carbon nanotube composite to obtain a carbon fiber-carbon nanotube composite modified filler CF-ZrO 2 @Cu@CNTs-CDs, the specific steps are the same as those in Example 1.

[0236] Comparative Example 5

[0237] This example is basically the same as Example 1, except that the carbon fiber-carbon nanotube composite prepared in step S2 of Example 1 is used as the carbon fiber-carbon nanotube composite modified filler in this example.

[0238] Performance Characterization and Testing

[0239] 1. Wear resistance

[0240] The test was conducted using a THT07-135 high temperature friction and wear tester. The friction pair was a steel pin (material GCrl5), with a hardness of 9 GPa, a roughness of 0.02 μm, a diameter of 4 mm, an applied load of 10 N, a sliding distance of 2000 m, a linear speed of 0.5 m / s, and a test wear rate K:

[0241] Where ΔV is the wear volume (mm 3 ), F is the load (N), and S is the total sliding distance (m).

[0242] (1) The wear rates of the gaskets of the embodiments and comparative examples were tested at room temperature and at a high temperature of 200°C.

[0243] (2) Referring to the process of Example 1, the amount of carbon fiber-carbon nanotube composite modified filler added (horizontal axis) was changed, and then the effect of the amount added on the wear rate was tested. The test results are as follows: Figure 1 As shown. It can be seen that within a certain range, as the amount of carbon fiber-carbon nanotube composite modified filler added increases, the wear rate of the gasket gradually decreases. Too much addition will lead to an increase in the wear rate, so the addition amount is around 3.75-12% as a better range, and further around 5-10 as a better range. Taking all factors into consideration, 7.5% is selected as the preferred addition amount in the embodiment.

[0244] 2. Performance Characterization

[0245] The carbon fiber-carbon nanotube composite modified filler (CF-ZrO 2 @Cu@CNTs-CDs) as an example, its performance is characterized as follows:

[0246] (1)Reference Figure 2 , is the carbon fiber-carbon nanotube composite modified filler (CF-ZrO 2 @Cu@CNTs-CDs) infrared absorption spectrum;

[0247] 2250cm -1 The nearby peaks are derived from the absorption peak of C≡N of PAN (polyacrylonitrile), proving the successful coating of polyacrylonitrile. -1 、680cm -1 The absorption peak near 570cm comes from CuO; -1 、480cm -1 The absorption peak near the ZrO bond originates from the ZrO bond, indicating that ZrO 2 The presence of; from the infrared absorption spectrum, it can be seen that the carbon fiber-carbon nanotube composite modified filler also has abundant functional groups such as carboxyl, amino, and hydroxyl, which mainly come from carbon dots, acidified carbon fibers and acidified carbon nanotubes. The successful synthesis of the carbon fiber-carbon nanotube composite modified filler was confirmed by the characterization of infrared absorption spectrum.

[0248] (2) CF-ZrO prepared in Example 1 2 Antioxidant properties of @Cu@CNTs-CDs

[0249] The CF-ZrO prepared in Example 1 2 @Cu@CNTs-CDs were added to ethanol to prepare a dispersion with a concentration of 0.5 mg / mL, and then the nitrogen free radical (DPPH) scavenging ability test kit (DPPH-A001-96T, Shanghai Huicheng Biotechnology Co., Ltd.) was used to detect the antioxidant properties of the dispersion at different times.

[0250] Determination principle: DPPH free radical is a relatively stable nitrogen-containing free radical with a single electron and strong absorption at 517nm. If other substances provide an electron to pair this single electron, its absorption will disappear and fade, and the degree of fading is proportional to the amount of electrons accepted. Therefore, the ability of the reactant to scavenge nitrogen free radicals is inversely proportional to the absorbance of the reagent at 517nm; that is, the lower the absorbance at 517nm, the stronger the ability to scavenge nitrogen free radicals, and the stronger the corresponding antioxidant performance.

[0251] Test results such as Figure 3 As shown, from Figure 3 It can be seen that CF-ZrO 2 @Cu@CNTs-CDs showed good antioxidant ability.

[0252] 3. Tensile strength

[0253] Tested with reference 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";

[0254] Tensile strength and compression resilience are one of the important indicators of sealing gasket materials. Tensile strength reflects the pressure resistance and tensile strength of the sealing gasket material, and can characterize the bonding strength between the filler and the matrix to a certain extent.

[0255] 4. Compression rebound rate

[0256] The test was carried out in accordance with the standard "GB / T12622-2008, GB / T 12622-2008 Test method for compression rate and rebound rate of gaskets for pipe flanges".

[0257] Compression rebound reflects the ability of the sealing gasket material to fill the defects on the sealing surface and perform elastic compensation to maintain the seal when elastic or plastic deformation occurs. The higher the compression rebound rate, the stronger the compensation ability.

[0258] 5. Creep relaxation rate

[0259] Tested with reference to the standard "GB / T20671.5-2020, GB / T 20671.5-2020 Classification system and test methods for non-metallic gasket materials Part 5: Test method for creep relaxation rate of gasket materials";

[0260] 6. Gas leakage rate

[0261] Tested in accordance with the standard GB / T12385-2008 GB / T 12385-2008 Test method for sealing performance of gaskets for pipe flanges.

[0262] 7. Thermal oxygen aging performance

[0263] Tested in accordance with the standard "GB T 7141-2008 Plastics Thermal Aging Test Method"; aged in air atmosphere, aging temperature is 150°C, aging time is 96h. Calculate the tensile strength retention rate η = tensile strength before aging / tensile strength after aging * 100%.

[0264] The above main performance test results are as follows Table 1 and Attachment Figure 4-Figure 10 As shown:

[0265] Table 1

[0266]

[0267]

[0268] From the test results in Table 1, it can be seen that the sealing gaskets prepared in Examples 1-3 have good wear resistance and thermal oxidation aging resistance, and excellent comprehensive performance. 2 @Cu@CNTs-CDs, the comprehensive performance decreased significantly; the comprehensive performance of Comparative Example 5 also decreased significantly, mainly because the carbon fiber-carbon nanotube composite was not treated with polyacrylonitrile graft coating, which affected the CF-ZrO 2 @Cu@CNTs-CDs are evenly dispersed in the sealing gasket system. The wear resistance, tensile strength, compression rebound rate and creep relaxation rate of comparative example 2 all decreased to a certain extent, indicating that ZrO 2 Hybrid carbon fiber can significantly improve the reinforcing effect of carbon fiber on the sealing gasket system. In comparative example 3, since copper nitrate was not added, the formation of the three-dimensional network structure was affected, and various properties declined; the thermal oxidation aging resistance of comparative example 4 declined significantly, which was attributed to the lack of the antioxidant effect provided by the reduced carbon dots.

[0269] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and the implementation modes. 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 preparation process for a wear-resistant and heat-resistant sealing gasket, characterized in that: The following steps are involved: Step 1, pre-drying polytetrafluoroethylene and polyperfluoroethylene propylene; Step 2: According to the mass percentage, 1.9-7.6% of polyperfluoroethylene propylene, 3.75-12% of carbon fiber-carbon nanotube composite modified filler and the balance of polytetrafluoroethylene are mixed and stirred; Step 3, adding the mixture obtained in step 2 into a mold for compression molding; then sintering in an air atmosphere and cooling to room temperature to obtain a gasket blank; Step 4: Mechanically process the gasket blank to obtain the wear-resistant and heat-resistant sealing gasket; Wherein, the carbon fiber-carbon nanotube composite modified filler is prepared by the following method: S1, preparing ZrO2 hybrid carbon fiber, denoted as CF-ZrO2; S2. Preparation of carbon fiber-carbon nanotube composites: S2-1, preparing acidified carbon nanotubes, denoted as acidified CNTs; S2-2, adding acidified CNTs, copper salt, glucose, ascorbic acid, 4-hexylresorcinol and urea into deionized water, and ultrasonically dispersing them to obtain a precursor solution A; S2-3, adding CF-ZrO2 and copper salt into deionized water, and ultrasonically dispersing them to obtain precursor solution B; S2-4, adding the precursor solution A to the precursor solution B under stirring, ultrasonically dispersing, transferring the obtained mixture to a reaction kettle, performing a one-pot hydrothermal reaction under heating, cooling to room temperature after the reaction is completed, filtering, washing the solid product, and vacuum drying to obtain a carbon fiber-carbon nanotube composite; S3. Performing polyacrylonitrile graft coating treatment on the carbon fiber-carbon nanotube composite to obtain the carbon fiber-carbon nanotube composite modified filler, which is recorded as CF-ZrO2@Cu@CNTs-CDs.

2. The preparation process of the wear-resistant and heat-resistant sealing gasket according to claim 1, characterized in that: Step S1 is specifically as follows: S1-1, washing the carbon fiber with deionized water and ethanol in sequence, drying, soaking in a mixed acid composed of sulfuric acid and nitric acid in a volume ratio of 2:1, stirring and refluxing at 65-80°C for 1-4h, cooling to room temperature, filtering, washing with deionized water until neutral, and vacuum drying at 90-110°C to constant weight to obtain acidified carbon fiber; S1-2, taking 2.5-10 g of acidified carbon fiber, adding it into 100-500 mL of deionized water, and ultrasonically dispersing it for 15-60 min to obtain an acidified carbon fiber dispersion; S1-3, prepare a zirconium oxychloride solution with a concentration of 0.05-0.2 mol / L with deionized water, add 25-100 mL of the zirconium oxychloride solution to the acidified carbon fiber dispersion, and perform ultrasonic dispersion for 2-10 minutes; S1-4. Add 5-20% by mass of ammonia water to the product obtained in step S1-3 under stirring to adjust the pH value to 7.5-9, filter, wash the solid product with deionized water, and then calcine at 500-600°C for 1-3h to obtain ZrO2 hybrid carbon fiber, recorded as CF-ZrO2.

3. The preparation process of the wear-resistant and heat-resistant sealing gasket according to claim 1, characterized in that: The copper salt is any one of copper nitrate, copper sulfate and copper chloride.

4. The preparation process of the wear-resistant and heat-resistant sealing gasket according to claim 3, characterized in that: Step S2 is specifically as follows: S2-1, preparation of acidified carbon nanotubes: The multi-walled carbon nanotubes are added to a mixed acid consisting of concentrated sulfuric acid and concentrated nitric acid in a volume ratio of 1:1, refluxed at 100-130°C for 2-6 hours, cooled to room temperature, filtered, washed with deionized water until neutral, and vacuum dried at 100-120°C to constant weight to obtain acidified carbon nanotubes, which are referred to as acidified CNTs; S2-2, add 0.75-3 g of acidified CNTs, 142-570 mg of copper nitrate, 180-720 mg of glucose, 44-176 mg of ascorbic acid, 29-116 mg of 4-hexylresorcinol, and 75-300 mg of urea into 200-1000 mL of deionized water, and disperse by ultrasonic for 30-90 min to obtain precursor solution A; S2-3, add 1-4 g CF-ZrO2 and 322-1300 mg copper nitrate into 250-1000 mL deionized water, and disperse by ultrasonic for 15-60 min to obtain precursor solution B; S2-4. Add precursor solution A to precursor solution B under stirring, ultrasonically disperse for 30-90 minutes, transfer the resulting mixture to a polytetrafluoroethylene-lined reactor, react at 185-220°C for 6-18 hours, cool to room temperature after the reaction, filter, wash the solid with deionized water and ethanol in turn, and then vacuum dry at 80-100°C for 6-24 hours to obtain a carbon fiber-carbon nanotube composite.

5. The preparation process of the wear-resistant and heat-resistant sealing gasket according to claim 4, characterized in that: Step S2 is specifically as follows: S2-1, preparation of acidified carbon nanotubes: The multi-walled carbon nanotubes were added to a mixed acid consisting of concentrated sulfuric acid and concentrated nitric acid in a volume ratio of 1:1, refluxed at 120°C for 3 h, cooled to room temperature, filtered, washed with deionized water until neutral, and vacuum dried at 110°C to constant weight to obtain acidified carbon nanotubes, which were recorded as acidified CNTs. S2-2, 1.5 g of acidified CNTs, 285 mg of copper nitrate, 360 mg of glucose, 88 mg of ascorbic acid, 58 mg of 4-hexylresorcinol, and 150 mg of urea were added to 400 mL of deionized water, and ultrasonically dispersed for 45 min to obtain precursor solution A; S2-3, add 2g CF-ZrO2 and 665mg copper nitrate into 500mL deionized water, and disperse by ultrasonic for 45min to obtain precursor solution B; S2-4. Precursor solution A is added to precursor solution B under stirring, and ultrasonic dispersion is performed for 45 minutes. The resulting mixture is transferred to a polytetrafluoroethylene-lined reactor and reacted at 210°C for 10 hours. After the reaction is completed, it is cooled to room temperature and filtered. The solid is washed with deionized water and ethanol in sequence, and then vacuum dried at 90°C for 12 hours to obtain a carbon fiber-carbon nanotube composite.

6. The preparation process of the wear-resistant and heat-resistant sealing gasket according to claim 1, characterized in that: Step S3 is specifically as follows: S3-1, adding 0.125-0.5 g of carbon fiber-carbon nanotube composite to a mixed solution consisting of 35-140 mL of ethanol and 15-60 mL of deionized water, and ultrasonically dispersing for 10-30 min; S3-2, adding 5-20 mL of acrylonitrile and 0.04-0.16 mL of dodecanethiol to the mixture obtained in step S3-1, and ultrasonically dispersing for 15-60 min; S3-3, raise the temperature to 50-70°C, add 0.4-1.6 g of initiator dropwise under nitrogen protection and continuous stirring, complete the addition within 15-60 minutes, and then react at a constant temperature for 45-120 minutes. After the reaction is completed, cool to room temperature and centrifuge. Wash the solid product with deionized water and dry it at 80-100°C for 6-24 hours to obtain the carbon fiber-carbon nanotube composite modified filler, recorded as CF-ZrO2@Cu@CNTs-CDs.

7. The preparation process of the wear-resistant and heat-resistant sealing gasket according to claim 6, characterized in that: The initiator is at least one of ammonium persulfate, potassium persulfate and ammonium sulfite.

8. The preparation process of the wear-resistant and heat-resistant sealing gasket according to claim 1, characterized in that: The following steps are involved: Step 1: Pre-dry polytetrafluoroethylene and polyperfluoroethylene propylene at 90-120°C for 3-8h; Step 2: According to the mass percentage, 1.9-7.6% of polyperfluoroethylene propylene, 3.75-12% of carbon fiber-carbon nanotube composite modified filler and the balance of polytetrafluoroethylene are added into a blender and mixed, and stirred at 500-2000 rpm for 1-4 hours; Step 3, adding the mixture obtained in step 2 into a mold, and performing compression molding at 20-30°C and 30-55MPa, with a compression holding time of 2-8min; then sintering at 330-360°C in an air atmosphere for 2-6h, and cooling to room temperature at a rate of 10-35°C / h to obtain a gasket blank; Step 4: Mechanically process the gasket blank according to the required specifications and dimensions to obtain the wear-resistant and heat-resistant sealing gasket.

9. The preparation process of the wear-resistant and heat-resistant sealing gasket according to claim 8, characterized in that: The following steps are involved: Step 1: pre-dry polytetrafluoroethylene and polyperfluoroethylene propylene at 100°C for 5 hours; Step 2: Add 3.8% of polyperfluoroethylene propylene, 7.5% of carbon fiber-carbon nanotube composite modified filler and the balance of polytetrafluoroethylene into a blender according to mass percentage, and stir at 1000 rpm for 2 hours; Step 3, adding the mixture obtained in step 2 into a mold, and molding it at 25°C and 40MPa, with a molding holding time of 3min; then sintering it at 355°C for 3h in an air atmosphere, and cooling it to room temperature at a rate of 20°C / h to obtain a gasket blank; Step 4: Mechanically process the gasket blank according to the required specifications and dimensions to obtain the wear-resistant and heat-resistant sealing gasket.

10. A wear-resistant and heat-resistant sealing gasket, characterized in that: The method is prepared by the process as described in any one of claims 1 to 9.

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