Method for producing modified ptfe wear-resistant material

Abstract

The application belongs to the technical field of PTFE material preparation, and particularly relates to a preparation method of modified PTFE wear-resistant material. The preparation method comprises the following steps: (1) preparation of modified chromium corundum micro powder; (2) preparation of modified molybdenum carbide; (3) preparation of modified barium fluoride; and (4) preparation of modified PTFE wear-resistant material. According to the preparation method of the modified PTFE wear-resistant material, PTFE resin is used as a main raw material, and modified chromium corundum micro powder, modified molybdenum carbide and modified barium fluoride are used as fillers. Through the high-hardness bearing and micro-cutting blocking effect of the modified chromium corundum micro powder, the micro-polishing effect of the modified molybdenum carbide and the interface toughening and low-shear lubricating film effect of the modified barium fluoride, the wear resistance of the PTFE material is improved, and the mechanical properties of the PTFE material are ensured.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of PTFE material preparation, and particularly relates to a preparation method of modified PTFE wear-resistant material. BACKGROUND

[0002] Polytetrafluoroethylene (PTFE) is known as "plastic king", which has excellent heat resistance, corrosion resistance and dielectric properties, especially its unique non-stick and extremely low friction coefficient, so that it is widely valued in chemical, electrical, mechanical and electronic industries. As one of the most widely used engineering plastics, PTFE is widely used in sealing parts, bearings and other parts of various industrial equipment due to its excellent tribological properties, especially low friction and high and low temperature resistance. Although polytetrafluoroethylene has been a research hotspot in the field of tribology due to its excellent self-lubricating performance and chemical inertness, its poor wear resistance and easy creep limit its wider application.

[0003] Filling modification is an effective method to change the overall performance of polymer materials, and filling modification can improve the defects of the matrix without destroying the structure of the polymer matrix. Moreover, the preparation process of the composite material is simple by filling modification, and the material can be endowed with new properties by selecting different types of fillers. The fillers selected for the filling modification of PTFE composite material mainly include metal fillers, inorganic non-metal fillers and some nano fillers. Traditional fillers are mostly ordinary powders with particle sizes above microns. These modifications improve the wear resistance of polytetrafluoroethylene, but often bring negative effects such as increased friction coefficient and significantly reduced strength. At present, the method of using a single filler for modification is mostly used, which leads to very limited improvement effect. Therefore, it is necessary to explore a new preparation method of modified PTFE wear-resistant material. SUMMARY

[0004] The purpose of the present application is to provide a preparation method of modified PTFE wear-resistant material. The preparation method of the present application is easy to implement, and the prepared PTFE material has excellent wear resistance.

[0005] The preparation method of the modified PTFE wear-resistant material according to the present application comprises the following steps:

[0006] (1) Preparation of modified chromium corundum micro powder

[0007] The chromium corundum micro powder is dehydrated and activated by calcining at 400-410 DEG C for 2h, and then cooled to room temperature in the furnace. Then, the chromium corundum micro powder is added to a toluene solution of perfluorooctyltriethoxysilane and refluxed at 80-85 DEG C for 4h. After the reaction, the filter cake is obtained by vacuum filtration under nitrogen protection at 65-70 DEG C. The filter cake is washed, dried, cooled and sieved to obtain the modified chromium corundum micro powder.

[0008] (2) Preparation of modified molybdenum carbide

[0009] ① Pretreated molybdenum carbide is prepared by ultrasonic treatment of molybdenum carbide in acetone, deionized water washing and vacuum drying. The pretreated molybdenum carbide is added to a nitric acid solution and reacted at 45-50°C for 0.5h under stirring. After reaction, the oxidized molybdenum carbide is prepared by post-treatment.

[0010] ② The mixed solution composed of toluene, deionized water and perfluorooctyltriethoxysilane is ultrasonically treated for 5-7min. Then the oxidized molybdenum carbide is added to the mixed solution. The reaction is carried out under reflux at 80-83°C for 4h under nitrogen protection and stirring. After reaction, the modified molybdenum carbide is prepared by post-treatment.

[0011] (3) Preparation of modified barium fluoride

[0012] ① Barium fluoride is ultrasonically treated in anhydrous ethanol for 15-20min. Then tetraethyl orthosilicate ethanol solution is added dropwise. Ammonia is added and the reaction is carried out at room temperature for 3.8-4h under stirring. Then the barium fluoride coated with silicon dioxide is prepared by post-treatment after filtration.

[0013] ② Perfluorooctyltriethoxysilane is added to the mixed solution of water and toluene and ultrasonically treated at room temperature for 3-5min. Then the barium fluoride coated with silicon dioxide prepared in ① is added. The reaction is carried out under reflux at 65-70°C for 4h under nitrogen protection and mechanical stirring. Then the modified barium fluoride is prepared by post-treatment.

[0014] (4) Preparation of modified PTFE wear-resistant material

[0015] ① PTFE resin is vacuum dried at 77-80°C for 4h. Modified chromium corundum powder, modified molybdenum carbide and modified barium fluoride are vacuum dried at 77-80°C for 6h. Then the dried PTFE resin, modified chromium corundum powder, modified molybdenum carbide and modified barium fluoride are mixed uniformly in a mixer and sieved through a 40 mesh sieve to prepare a mixture.

[0016] ② The mixture is pressed and sintered to prepare the modified PTFE wear-resistant material.

[0017] In step (1), the mass of perfluorooctyltriethoxysilane accounts for 5-6% of the mass of chromium corundum powder.

[0018] The mass concentration of the toluene solution of perfluorooctyltriethoxysilane in step (1) is 5%.

[0019] The elution in step (1) is performed 3-5 times using toluene, the drying is performed at 100℃ for 2h under vacuum, the cooling is to room temperature, and the sieving is through a 200 mesh sieve.

[0020] In step (2) ①, the mass / volume ratio of molybdenum carbide to acetone is 1:8, g / mL, and the pretreated molybdenum carbide is prepared by ultrasonic treatment with acetone for 15-20min, washing with deionized water for 3-5 times, and drying at 80-85℃ under vacuum for 2h.

[0021] In step (2) ①, the concentration of the nitric acid solution is 8mol / L, and the stirring speed is 300r / min.

[0022] In step (2) ①, the post-treatment is to immediately pour the reaction solution into ice water after the reaction is completed to quench, the volume of ice water is 10 times that of the nitric acid solution, the temperature of ice water is 0℃, then suction filtration, washing with deionized water until pH=6, eluting once with 0.84% sodium bicarbonate, washing with water for 3-5 times, and finally drying at 80-85℃ under vacuum for 12h, and cooling to room temperature.

[0023] In step (2) ①, the mass / volume ratio of pretreated molybdenum carbide to nitric acid solution is 1:15.

[0024] In step (2) ②, the mass ratio of toluene to oxidized molybdenum carbide is 1:1.

[0025] In step ②, the mass ratio of deionized water to perfluorooctyltriethoxysilane is 1:1.

[0026] In step (2) ②, the mass of perfluorooctyltriethoxysilane accounts for 5-6% of the mass of oxidized molybdenum carbide.

[0027] In step (2) ②, the mechanical stirring speed is 300r / min.

[0028] In step (2) ②, the post-treatment is to cool to 38-40℃ after the reaction is completed, then suction filtration, the filter cake is eluted 3-5 times with toluene, eluted once with 0.1% sodium bicarbonate, washed with deionized water for 3-5 times, and finally dried at 80℃ under vacuum for 12h, and cooled to room temperature and sieved through a 200 mesh sieve.

[0029] In step (2), mild oxidation treatment with concentrated nitric acid can create a Mo-O-OH transition layer rich in -OH on the surface of molybdenum carbide. Once the transition layer is formed, the diffusion of H + is blocked, the reaction will automatically slow down and will not continue to deep etch, ensuring that the hardness of the particles does not change, providing chemical reaction sites for the subsequent silanization reaction.

[0030] The mass-volume ratio of barium fluoride to anhydrous ethanol in step (3) ① is 1:4, unit: g / mL.

[0031] The mass-volume ratio of tetraethyl orthosilicate to ethanol in the ethanol solution of tetraethyl orthosilicate in step (3) ① is 1:10, unit: g / mL, and the tetraethyl orthosilicate is dissolved in ethanol, and then slowly added after fully shaking, 1 mL per minute, to avoid local hydrolysis.

[0032] In step (3), ammonia water is added after the addition of the ethanol solution of tetraethyl orthosilicate is completed.

[0033] The mass of tetraethyl orthosilicate in step (3) ① accounts for 10% of the mass of barium fluoride.

[0034] The mass concentration of ammonia water in step (3) ① is 25%, and the ammonia water is added dropwise to adjust the pH value of the reaction system to 10, and the stirring speed is 300 r / min.

[0035] The post-treatment in step (3) ① is to leach with ethanol for 3-5 times to remove free SiO2 sol, and vacuum drying at 80°C for 1.5 h.

[0036] The mass ratio of water to perfluorooctyltriethoxysilane in step (3) ② is 1:8.

[0037] The mass-volume ratio of perfluorooctyltriethoxysilane to toluene in step (3) ② is 1:4.

[0038] The mass of perfluorooctyltriethoxysilane in step (3) ② accounts for 5-6% of the mass of the silica-coated barium fluoride.

[0039] The stirring speed in step (3) ② is 300 r / min.

[0040] The post-treatment in step (3) ② is hot vacuum filtration at 40°C, and then the obtained filter cake is leached with toluene for 3 times, leached with 0.1% mass concentration sodium bicarbonate solution for 1 time, washed with deionized water for 3-5 times, and finally vacuum dried at 80°C for 12 h, cooled to room temperature, and passed through a 200 mesh sieve.

[0041] The mixing temperature in step (4) ① is 20°C, and the mixing time is 20 min.

[0042] The PTFE wear-resistant material in step (4) ① is composed of the following raw materials in mass fraction: PTFE resin 80 parts, modified chromium corundum powder 7-9 parts, modified molybdenum carbide 7-9 parts, and modified barium fluoride 4 parts.

[0043] The pressure for pressing in step (4) ② is 45 MPa, and the time for pressing is 20 min.

[0044] The sintering in step (4) ② is heating to 365-370℃ at a heating rate of 1℃ / min for 2h, then decreasing to 200℃ at a rate of 1℃ / min, and finally naturally cooling to room temperature.

[0045] Compared with the prior art, the present application has the following beneficial effects:

[0046] (1) The preparation method of the modified PTFE wear-resistant material takes PTFE resin as the main raw material, and adds modified chromium corundum micropowder, modified molybdenum carbide and modified barium fluoride as fillers, and the three synergistically act to ensure the wear resistance and mechanical properties of the prepared PTFE wear-resistant material. After the chromium corundum micropowder is modified by perfluorooctyltriethoxysilane, the surface energy thereof is significantly reduced, the interfacial compatibility and bonding strength with the PTFE resin are fundamentally improved, and the effective transmission of stress from the matrix to the reinforcing particles is ensured. Since the chromium corundum itself has very high microhardness and fracture toughness, it can prevent the PTFE macromolecular chains from being sheared and torn when the PTFE wear-resistant material bears a load. When the microconvex body on the opposite surface is pressed in, the chromium corundum particles can be micro-fractured and micro-displaced, so that one large cutting is changed into countless micro-cutting, thereby dispersing the capacity and reducing the wear rate. After the molybdenum carbide is slightly oxidized and modified by fluorosilane, a fluorocarbon layer matching the surface energy of PTFE is formed on the surface of the particles, realizing good interfacial wetting and mutual solubility, and ensuring effective transmission of the load. During the friction process, the modified molybdenum carbide produces a micro-polishing effect on the opposite surface due to its high hardness, which makes the transfer film thinner and more uniform. Since the barium fluoride is an ionic compound, it is first coated with silicon dioxide on the surface, and then modified by fluorosilane. The Si-O-Si bond anchors the fluorocarbon chain on the SiO2 surface of the BaF2 / SiO2 core, and the PTFE chain segments interdiffuse during sintering to form a firm interface. BaF2 is pre-melted at high temperature (>260℃) and generates a low-shear fluoride lubricating film to reduce the friction coefficient. At the same time, the hard core is embedded in the transfer film, like a "micro rivet", which inhibits the overall peeling of the film and prolongs the film life, thereby significantly reducing the wear rate. Thus, by the high-hardness load and micro-cutting blocking effect of the modified chromium corundum micropowder, the micro-polishing effect of the modified molybdenum carbide, and the interfacial toughening and low-shear lubricating film effect of the modified barium fluoride, the wear resistance of the PTFE material is improved while the mechanical properties of the PTFE material are ensured.

[0047] (2) The preparation method of the modified PTFE wear-resistant material has process parameters that are easy to control, so that the performance of the prepared modified PTFE wear-resistant material is stable. DETAILED DESCRIPTION

[0048] Example 1

[0049] The preparation method of the modified PTFE wear-resistant material of the present embodiment 1 is composed of the following steps:

[0050] (1) Preparation of modified chromium corundum micropowder

[0051] The chromium corundum micropowder is dehydrated and activated by calcining at 405 ℃ for 2 h, and then cooled to room temperature. Then the chromium corundum micropowder is added to a toluene solution of perfluorooctyltriethoxysilane and refluxed at 83 ℃ for 4 h. After the reaction, the filter cake is obtained by vacuum filtration under nitrogen protection at 67 ℃. The filter cake is rinsed, dried, cooled, and sieved to obtain the modified chromium corundum micropowder;

[0052] (2) Preparation of modified molybdenum carbide

[0053] ① The pretreated molybdenum carbide is prepared by ultrasonic treatment of molybdenum carbide in acetone, deionized water washing, and vacuum drying. The pretreated molybdenum carbide is added to a nitric acid solution and stirred at 47 ℃ for 0.5 h. After the reaction, the oxidized molybdenum carbide is obtained by post-treatment.

[0054] ② The mixed solution composed of toluene, deionized water, and perfluorooctyltriethoxysilane is ultrasonically treated for 6 min. Then the oxidized molybdenum carbide is added to the mixed solution and refluxed at 81 ℃ for 4 h under nitrogen protection and stirring. After the reaction, the modified molybdenum carbide is obtained by post-treatment.

[0055] (3) Preparation of modified barium fluoride

[0056] ① The barium fluoride is ultrasonically treated in anhydrous ethanol for 17 min, and then the tetraethyl orthosilicate ethanol solution is added dropwise. Ammonia is added and stirred at room temperature for 3.9 h. Then the silica-coated barium fluoride is obtained by filtration and post-treatment.

[0057] ② Perfluorooctyltriethoxysilane is added to the mixture of water and toluene and ultrasonically treated at room temperature for 4 min. Then the silica-coated barium fluoride prepared in ① is added, and the temperature is raised to 67 ℃ under nitrogen protection and mechanical stirring. The reaction is carried out for 4 h. Then the modified barium fluoride is obtained by post-treatment.

[0058] (4) Preparation of modified PTFE wear-resistant material

[0059] ① The PTFE resin is vacuum dried at 78 ℃ for 4 h. The modified chromium corundum micropowder, modified molybdenum carbide, and modified barium fluoride are vacuum dried at 78 ℃ for 6 h. Then the dried PTFE resin, modified chromium corundum micropowder, modified molybdenum carbide, and modified barium fluoride are mixed uniformly in a mixer and sieved through a 40-mesh sieve to obtain a mixture.

[0060] ② The mixture is pressed and sintered to obtain the modified PTFE wear-resistant material.

[0061] The mass of the perfluorooctyltriethoxysilane in step (1) accounts for 5.5% of the mass of the chromium corundum micropowder.

[0062] The mass concentration of the toluene solution of the perfluorooctyltriethoxysilane in step (1) is 5%.

[0063] The elution in step (1) is eluted with toluene for 4 times, the drying is vacuum drying at 100℃ for 2h, the cooling is cooling to room temperature, and the sieving is sieving through a 200-mesh sieve.

[0064] In step (2) ①, the mass-volume ratio of the molybdenum carbide to acetone is 1:8, g / mL, and the pretreated molybdenum carbide is prepared by ultrasonic treatment with acetone for 17 min, washing with deionized water for 4 times, and vacuum drying at 83℃ for 2h.

[0065] In step (2) ①, the concentration of the nitric acid solution is 8 mol / L, and the stirring speed is 300 r / min.

[0066] In step (2) ①, the post-treatment is that after the reaction is completed, the reaction solution is immediately poured into ice water for quenching, the volume of the ice water is 10 times the volume of the nitric acid solution, the temperature of the ice water is 0℃, then the filtration is performed, washing with deionized water until pH=6, eluting with 0.84% sodium bicarbonate once, washing with water for 4 times, and finally drying at 83℃ under vacuum for 12h, and cooling to room temperature.

[0067] In step (2) ①, the mass-volume ratio of the pretreated molybdenum carbide to the nitric acid solution is 1:15, g / mL.

[0068] In step (2) ②, the mass ratio of toluene to the oxidized molybdenum carbide is 1:1.

[0069] In step (2) ②, the mass ratio of deionized water to perfluorooctyltriethoxysilane is 1:1.

[0070] In step (2) ②, the mass of the perfluorooctyltriethoxysilane accounts for 5.5% of the mass of the oxidized molybdenum carbide.

[0071] In step (2) ②, the mechanical stirring speed is 300 r / min.

[0072] In step (2) ②, the post-treatment is that after the reaction is completed, the cooling is performed to 39℃, then the filtration is performed, the filter cake is eluted with toluene for 4 times, eluted with 0.1% sodium bicarbonate once, washed with deionized water for 4 times, and finally dried at 80℃ under vacuum for 12h, and cooled to room temperature, and sieved through a 200-mesh sieve.

[0073] In step (2), the mild oxidation treatment with concentrated nitric acid can produce a Mo-O-OH transition layer rich in -OH on the surface of the molybdenum carbide. Once the transition layer is formed, H+ The diffusion is hindered, the reaction is automatically slowed down, and the deep corrosion is not continued, so that the hardness of the particles is not changed, and a chemical reaction point is provided for the subsequent silanization reaction.

[0074] The mass-volume ratio of barium fluoride to anhydrous ethanol in step (3) 1 is 1:4, and the unit is g / mL.

[0075] The mass-volume ratio of tetraethyl orthosilicate to ethanol in the ethanol solution of tetraethyl orthosilicate in step (3) 1 is 1:10, and the unit is g / mL. The tetraethyl orthosilicate is dissolved in ethanol, and after being fully shaken, it is slowly added dropwise, 1 mL per minute, to avoid local hydrolysis.

[0076] In step (3), ammonia water is added after the addition of the ethanol solution of tetraethyl orthosilicate is completed.

[0077] The mass of tetraethyl orthosilicate in step (3) 1 accounts for 10% of the mass of barium fluoride.

[0078] The mass concentration of ammonia water in step (3) 1 is 25%, and the ammonia water is added dropwise to adjust the pH value of the reaction system to 10, and the stirring speed is 300 r / min.

[0079] The post-treatment in step (3) 1 is ethanol leaching 4 times to remove free SiO2 sol, and vacuum drying at 80°C for 1.5h.

[0080] The mass ratio of water to perfluorooctyltriethoxysilane in step (3) 2 is 1:8.

[0081] The mass-volume ratio of perfluorooctyltriethoxysilane to toluene in step (3) 2 is 1:4.

[0082] The mass of perfluorooctyltriethoxysilane in step (3) 2 accounts for 5.5% of the mass of the silica-coated barium fluoride.

[0083] The stirring speed in step (3) 2 is 300 r / min.

[0084] The post-treatment in step (3) 2 is hot vacuum filtration at 40°C, and then the obtained filter cake is washed with toluene 3 times, washed with a 0.1% mass concentration sodium bicarbonate solution 1 time, washed with deionized water 4 times, and finally vacuum dried at 80°C for 12h, cooled to room temperature, and passed through a 200 mesh screen.

[0085] The mixing temperature in step (4) 1 is 20°C, and the mixing time is 20min.

[0086] The PTFE wear-resistant material in step (4) 1 is composed of the following raw materials in mass parts: PTFE resin 80 parts, modified chromium corundum powder 8 parts, modified molybdenum carbide 8 parts, and modified barium fluoride 4 parts.

[0087] The pressure for the press forming in step (4) ② is 45 MPa, and the time for the press forming is 20 min.

[0088] The sintering in step (4) ② is performed by increasing the temperature to 368 ℃ at a rate of 1 ℃ / min and maintaining the temperature for 2 h, then decreasing the temperature to 200 ℃ at a rate of 1 ℃ / min, and finally naturally cooling to room temperature.

[0089] Example 2

[0090] The preparation method of the modified PTFE wear-resistant material described in this example 2 is composed of the following steps:

[0091] (1) Preparation of modified chromium corundum micropowder

[0092] The chromium corundum micropowder is dehydrated and activated by calcining at 400 ℃ for 2 h, and then cooled to room temperature in the furnace. Then, the chromium corundum micropowder is added to a toluene solution of perfluorooctyltriethoxysilane and refluxed at 80 ℃ for 4 h. After the reaction is completed, the obtained filter cake is washed, dried, cooled, and sieved under vacuum filtration at 65 ℃ under nitrogen protection to prepare the modified chromium corundum micropowder.

[0093] (2) Preparation of modified molybdenum carbide

[0094] ① The pretreated molybdenum carbide is prepared by ultrasonic treatment of molybdenum carbide in acetone, deionized water washing, and vacuum drying. The pretreated molybdenum carbide is added to a nitric acid solution and reacted at 50 ℃ for 0.5 h under stirring. After the reaction is completed, the post-treatment is performed to obtain the oxidized molybdenum carbide.

[0095] ② The mixed solution composed of toluene, deionized water, and perfluorooctyltriethoxysilane is ultrasonically treated for 7 min. Then, the oxidized molybdenum carbide is added to the above mixed solution, and the reaction is carried out under stirring at 83 ℃ for 4 h under nitrogen protection. After the reaction is completed, the post-treatment is performed to obtain the modified molybdenum carbide.

[0096] (3) Preparation of modified barium fluoride

[0097] ① The barium fluoride is ultrasonically treated in anhydrous ethanol for 15 min, and then the tetraethyl orthosilicate ethanol solution is added dropwise. Ammonia is added and reacted at room temperature for 4 h under stirring. Then, the filter cake is obtained by filtration and post-treatment to obtain the silica-coated barium fluoride.

[0098] ② Perfluorooctyltriethoxysilane is added to the mixed solution of water and toluene and ultrasonically treated at room temperature for 5 min. Then, the silica-coated barium fluoride prepared in ① is added, and the reaction is carried out under mechanical stirring at 65 ℃ for 4 h under nitrogen protection. Then, the post-treatment is performed to obtain the modified barium fluoride.

[0099] (4) Preparation of modified PTFE wear-resistant material

[0100] ① The PTFE resin is vacuum dried at 77℃ for 4h, the modified chromium corundum micro-powder, the modified molybdenum carbide and the modified barium fluoride are vacuum dried at 77℃ for 6h, then the dried PTFE resin, the modified chromium corundum micro-powder, the modified molybdenum carbide and the modified barium fluoride are uniformly mixed in a mixer, and sieved through a 40-mesh sieve to obtain a mixture.

[0101] ② The mixture is pressed and sintered to obtain the modified PTFE wear-resistant material.

[0102] In step (1), the mass of the perfluorooctyl triethoxysilane accounts for 5% of the mass of the chromium corundum micro-powder.

[0103] In step (1), the mass concentration of the toluene solution of the perfluorooctyl triethoxysilane is 5%.

[0104] In step (1), the elution is performed by using toluene for 3 times, the drying is performed at 100℃ for 2h under vacuum, the cooling is performed to room temperature, and the sieving is performed through a 200-mesh sieve.

[0105] In step (2) ①, the mass-volume ratio of the molybdenum carbide to the acetone is 1:8, the pretreated molybdenum carbide is obtained by ultrasonic treatment with acetone for 20min, washing with deionized water for 5 times, and vacuum drying at 85℃ for 2h.

[0106] In step (2) ①, the concentration of the nitric acid solution is 8mol / L, and the stirring speed is 300r / min.

[0107] In step (2) ①, the post-treatment is performed by immediately pouring the reaction solution into ice water to quench after the reaction, the volume of the ice water is 10 times that of the nitric acid solution, the temperature of the ice water is 0℃, then the filtration is performed, washing with deionized water until pH=6, eluting with 0.84% sodium bicarbonate once, washing with water for 5 times, and finally drying at 85℃ under vacuum for 12h, and cooling to room temperature.

[0108] In step (2) ①, the mass-volume ratio of the pretreated molybdenum carbide to the nitric acid solution is 1:15.

[0109] In step (2) ②, the mass ratio of toluene to the oxidized molybdenum carbide is 1:1.

[0110] In step (2) ②, the mass ratio of deionized water to the perfluorooctyl triethoxysilane is 1:1.

[0111] In step (2) ②, the mass of the perfluorooctyl triethoxysilane accounts for 6% of the mass of the oxidized molybdenum carbide.

[0112] The mechanical stirring speed in step (2) ② is 300 r / min.

[0113] The post-treatment in step (2) ② is as follows: after cooling to 40℃, the reaction is filtered, the filter cake is washed with toluene for 5 times, washed with 0.1% sodium bicarbonate for 1 time, washed with deionized water for 5 times, and finally dried at 80℃ under vacuum for 12 h, cooled to room temperature, and sieved through a 200 mesh sieve.

[0114] In step (2), mild oxidation treatment with concentrated nitric acid can produce a Mo-O-OH transition layer rich in -OH on the surface of the molybdenum carbide. Once the transition layer is formed, H + The diffusion is hindered, the reaction slows down automatically, and the depth of corrosion is not continued, so that the hardness of the particles is not changed, and chemical reaction points are provided for the subsequent silanization reaction.

[0115] In step (3) ①, the mass / volume ratio of barium fluoride to anhydrous ethanol is 1:4, in units of g / mL.

[0116] In step (3) ①, the mass / volume ratio of tetraethyl orthosilicate to ethanol in the tetraethyl orthosilicate ethanol solution is 1:10, in units of g / mL. The tetraethyl orthosilicate is dissolved in ethanol, shaken thoroughly, and then slowly added dropwise, with 1 mL added per minute to avoid local hydrolysis.

[0117] In step (3), ammonia water is added after the addition of the tetraethyl orthosilicate ethanol solution is complete.

[0118] In step (3) ①, the mass of tetraethyl orthosilicate is 10% of the mass of barium fluoride.

[0119] In step (3) ①, the mass concentration of ammonia water is 25%, and the ammonia water is added dropwise to adjust the pH of the reaction system to 10, with a stirring speed of 300 r / min.

[0120] In step (3) ①, the post-treatment is washing with ethanol for 5 times to remove free SiO2 sol, and vacuum drying at 80℃ for 1.5 h.

[0121] In step (3) ②, the mass ratio of water to perfluorooctyltriethoxysilane is 1:8.

[0122] In step (3) ②, the mass / volume ratio of perfluorooctyltriethoxysilane to toluene is 1:4.

[0123] In step (3) ②, the mass of perfluorooctyltriethoxysilane is 5% of the mass of the silica-coated barium fluoride.

[0124] In step (3) ②, the stirring speed is 300 r / min.

[0125] The post-treatment in step (3) ② is vacuum filtration at 40℃ while hot, then the obtained filter cake is washed with toluene for 3 times, washed with 0.1% mass concentration sodium bicarbonate solution for 1 time, washed with deionized water for 5 times, and finally vacuum dried at 80℃ for 12h, cooled to room temperature, and sieved through a 200 mesh sieve.

[0126] The mixing temperature in step (4) ① is 20℃, and the mixing time is 20min.

[0127] The PTFE wear-resistant material in step (4) ① is composed of the following raw materials in mass fraction: PTFE resin 80 parts, modified chromium corundum micro powder 7 parts, modified molybdenum carbide 9 parts, and modified barium fluoride 4 parts.

[0128] The pressure for press molding in step (4) ② is 45MPa, and the time for press molding is 20min.

[0129] The sintering in step (4) ② is to heat up to 365℃ at a heating rate of 1℃ / min for 2h, then reduce to 200℃ at a rate of 1℃ / min, and finally cool to room temperature naturally.

[0130] Example 3

[0131] The preparation method of the modified PTFE wear-resistant material in this example 3 is composed of the following steps:

[0132] (1) Preparation of modified chromium corundum micro powder

[0133] The chromium corundum micro powder is dehydrated and activated by calcining at 410℃ for 2h, and then cooled to room temperature in the furnace. Then it is added to a toluene solution of perfluorooctyltriethoxysilane and refluxed at 85℃ for 4h. After the reaction is completed, vacuum filtration is performed under nitrogen protection at 70℃. The obtained filter cake is washed, dried, cooled, and sieved to obtain the modified chromium corundum micro powder.

[0134] (2) Preparation of modified molybdenum carbide

[0135] ① The molybdenum carbide is pretreated by ultrasonic treatment in acetone, vacuum filtration, deionized water washing, and vacuum drying to obtain pretreated molybdenum carbide. The pretreated molybdenum carbide is added to a nitric acid solution and reacted at 45℃ for 0.5h under stirring. After the reaction is completed, post-treatment is performed to obtain the oxidized molybdenum carbide.

[0136] ② The mixed solution composed of toluene, deionized water, and perfluorooctyltriethoxysilane is ultrasonically treated for 5min. Then the oxidized molybdenum carbide is added to the above mixed solution and refluxed at 80℃ for 4h under stirring and nitrogen protection. After the reaction is completed, post-treatment is performed to obtain the modified molybdenum carbide.

[0137] (3) Preparation of modified barium fluoride

[0138] ① The barium fluoride is ultrasonically treated in anhydrous ethanol for 20 min, then the tetraethyl orthosilicate ethanol solution is added dropwise, ammonia water is added, and the reaction is carried out at room temperature under stirring for 3.8 h, then the silica-coated barium fluoride is prepared by post-treatment after filtration.

[0139] ② The perfluorooctyltriethoxysilane is added to the mixture of water and toluene, and ultrasonically treated at room temperature for 3 min, then the silica-coated barium fluoride prepared in ① is added, and the reaction is carried out under mechanical stirring at 70℃ under nitrogen protection for 4 h, then the modified barium fluoride is prepared by post-treatment.

[0140] (4) Preparation of modified PTFE wear-resistant material

[0141] ① The PTFE resin is vacuum dried at 80℃ for 4 h, the modified chromium corundum micropowder, the modified molybdenum carbide and the modified barium fluoride are vacuum dried at 80℃ for 6 h, then the dried PTFE resin, the modified chromium corundum micropowder, the modified molybdenum carbide and the modified barium fluoride are uniformly mixed in a mixer, and sieved through a 40-mesh sieve to prepare a mixture.

[0142] ② The mixture is pressed and sintered to prepare the modified PTFE wear-resistant material.

[0143] In step (1), the mass of the perfluorooctyltriethoxysilane accounts for 6% of the mass of the chromium corundum micropowder.

[0144] In step (1), the mass concentration of the toluene solution of the perfluorooctyltriethoxysilane is 5%.

[0145] In step (1), the elution is performed by toluene for 5 times, the drying is performed at 100℃ under vacuum for 2 h, the cooling is performed to room temperature, and the sieving is performed through a 200-mesh sieve.

[0146] In step (2) ①, the mass-volume ratio of the molybdenum carbide to acetone is 1:8 (g / mL), the molybdenum carbide is ultrasonically treated in acetone for 15 min, washed with deionized water for 3 times, and vacuum dried at 80℃ for 2 h to prepare the pretreated molybdenum carbide.

[0147] In step (2) ①, the concentration of the nitric acid solution is 8 mol / L, and the stirring speed is 300 r / min.

[0148] In step (2) ①, the post-treatment is performed by immediately pouring the reaction solution into ice water after the reaction is completed to quench, the volume of the ice water is 10 times of the volume of the nitric acid solution, the temperature of the ice water is 0℃, then the filtration is performed, washed with deionized water until pH=6, eluted with 0.84% sodium bicarbonate once, washed with water for 3 times, and finally dried at 80℃ under vacuum for 12 h, and cooled to room temperature.

[0149] The mass-volume ratio of the pretreated molybdenum carbide and the nitric acid solution in step (2) 1 is 1:15, in units of g / mL.

[0150] The mass ratio of toluene to the oxidized molybdenum carbide in step (2) 2 is 1:1.

[0151] The mass ratio of deionized water to perfluorooctyltriethoxysilane in step 2 is 1:1.

[0152] The mass of perfluorooctyltriethoxysilane in step (2) 2 accounts for 5% of the mass of the oxidized molybdenum carbide.

[0153] The mechanical stirring speed in step (2) 2 is 300 r / min.

[0154] The post-treatment in step (2) 2 is that after cooling to 38℃, the filter cake is washed with toluene three times, washed with 0.1% sodium bicarbonate once, washed with deionized water three times, and finally dried at 80℃ under vacuum for 12h, cooled to room temperature, and sieved through a 200-mesh sieve.

[0155] The mild oxidation treatment with concentrated nitric acid in step (2) can produce a Mo-O-OH transition layer rich in -OH on the surface of the molybdenum carbide. Once the transition layer is formed, the diffusion of H + is blocked, the reaction slows down automatically, and the particle hardness does not change, providing chemical reaction sites for the subsequent silanization reaction.

[0156] The mass-volume ratio of barium fluoride to anhydrous ethanol in step (3) 1 is 1:4, in units of g / mL.

[0157] The mass-volume ratio of tetraethyl orthosilicate to ethanol in the tetraethyl orthosilicate ethanol solution in step (3) 1 is 1:10, in units of g / mL. The tetraethyl orthosilicate is dissolved in ethanol, shaken thoroughly, and then slowly added dropwise, with 1mL added per minute to avoid local hydrolysis.

[0158] In step (3), ammonia water is added after the addition of the tetraethyl orthosilicate ethanol solution is complete.

[0159] The mass of tetraethyl orthosilicate in step (3) 1 accounts for 10% of the mass of barium fluoride.

[0160] The mass concentration of ammonia water in step (3) 1 is 25%, and the ammonia water is added dropwise to adjust the pH value of the reaction system to 10, with a stirring speed of 300 r / min.

[0161] The post-treatment in step (3) 1 is toluene washing three times to remove free SiO2 sol, and vacuum drying at 80℃ for 1.5h.

[0162] The mass ratio of water to perfluorooctyltriethoxysilane in step (3) ② is 1:8.

[0163] The mass-volume ratio of perfluorooctyltriethoxysilane to toluene in step (3) ② is 1:4.

[0164] The mass of perfluorooctyltriethoxysilane in step (3) ② accounts for 6% of the mass of the silica-coated barium fluoride.

[0165] The stirring speed in step (3) ② is 300 r / min.

[0166] The post-treatment in step (3) ② is hot vacuum filtration at 40℃, then the obtained filter cake is washed with toluene for 3 times, washed with a 0.1% mass concentration sodium bicarbonate solution for 1 time, washed with deionized water for 3 times, finally vacuum dried at 80℃ for 12h, cooled to room temperature, and sieved through a 200 mesh sieve.

[0167] The mixing temperature in step (4) ① is 20℃, and the mixing time is 20min.

[0168] The PTFE wear-resistant material in step (4) ① is composed of the following raw materials in mass parts: PTFE resin 80 parts, modified chromium corundum powder 9 parts, modified molybdenum carbide 7 parts, and modified barium fluoride 4 parts.

[0169] The pressure for pressing in step (4) ② is 45MPa, and the pressing time is 20min.

[0170] The sintering in step (4) ② is to heat to 370℃ at a heating rate of 1℃ / min for 2h, then to 200℃ at a rate of 1℃ / min, and finally naturally cooled to room temperature.

[0171] Comparative Example 1

[0172] The preparation method of the modified PTFE wear-resistant material in Comparative Example 1 is the same as that in Example 1, the only difference being that the PTFE wear-resistant material does not add modified chromium corundum powder, wherein the PTFE wear-resistant material in step (4) ① is composed of the following raw materials in mass parts: PTFE resin 80 parts, modified molybdenum carbide 6 parts, and modified barium fluoride 4 parts.

[0173] Comparative Example 2

[0174] The preparation method of the modified PTFE wear-resistant material in Comparative Example 2 is the same as that in Example 1, the only difference being that the PTFE wear-resistant material does not add modified molybdenum carbide, wherein the PTFE wear-resistant material in step (4) ① is composed of the following raw materials in mass parts: PTFE resin 80 parts, modified chromium corundum powder 10 parts, and modified barium fluoride 4 parts.

[0175] Comparative Example 3

[0176] The preparation method of the modified PTFE wear-resistant material of the present comparative example 3 is the same as that of the example 1, the only difference is that the modified PTFE wear-resistant material does not add modified barium fluoride, wherein the PTFE wear-resistant material in step (4) ① is composed of the following raw materials in mass fraction: PTFE resin 80 parts, modified chromium corundum powder 10 parts, modified molybdenum carbide 6 parts.

[0177] The modified PTFE wear-resistant materials prepared in the examples 1-3 and the comparative examples 1-3 are tested for performance, wherein the tensile strength is tested by the test method of GB1040-79, the initial friction coefficient and the wear friction coefficient are both tested by the test method of GB3960-2016, and the test object of the wear friction coefficient is the surface of the composite material after the modified PTFE wear-resistant materials prepared in the examples 1-3 and the comparative examples 1-3 are subjected to a load of 180N, a sliding speed of 0.3m / s, and dry friction for 4h, the grinding wheel: 45 steel, 42-45HRC; the wear rate is the volume worn under unit load per unit length, that is, wear rate = wear volume after grinding by the above-mentioned method ÷ cumulative friction work, unit: cm 3 / (N·m). The test results are shown in Table 1:

[0178] Table 1 Performance test results of modified PTFE wear-resistant materials

[0179]

[0180] As known by those skilled in the art, the smaller the wear rate, the more excellent the wear resistance of the PTFE wear-resistant material. As shown in Table 1, the tensile strength of the modified PTFE wear-resistant materials prepared in the examples 1-3 is much greater than that of the comparative examples 1-3, and the wear rate of the modified PTFE wear-resistant materials prepared in the examples 1-3 is much smaller than that of the comparative examples 1-3.

[0181] The above is only the preferred embodiment of the present application, and is not intended to limit the other forms of the present application, and any skilled person in the art can modify or change the above-mentioned disclosed technical content into equivalent embodiments with equivalent changes. However, any simple modification, equivalent change and modification made on the basis of the technical essence of the present application to the above-mentioned embodiments, which does not deviate from the technical solution content of the present application, still belongs to the protection scope of the technical solution of the present application.

Claims

1. A method for preparing a modified PTFE wear-resistant material, characterized in that: It consists of the following steps: (1) Preparation of modified chromium corundum micro powder Chromium corundum micro powder was calcined at 400-410℃ for 2 hours to dehydrate and activate it. It was then cooled to room temperature in the furnace and added to a toluene solution of perfluorooctyltriethoxysilane. The mixture was refluxed at 80-85℃ for 4 hours. After the reaction was completed, the mixture was vacuum filtered at 65-70℃ under nitrogen protection. The resulting filter cake was washed, dried, cooled, and sieved to prepare modified chromium corundum micro powder. (2) Preparation of modified molybdenum carbide ① Molybdenum carbide was ultrasonically treated with acetone, filtered, washed with deionized water, and vacuum dried to prepare pretreated molybdenum carbide. The pretreated molybdenum carbide was added to nitric acid solution and reacted at 45-50℃ for 0.5 h under stirring. After the reaction was completed, post-treatment was performed to prepare oxidized molybdenum carbide. ②The mixed solution consisting of toluene, deionized water and perfluorooctyltriethoxysilane was ultrasonically treated for 5-7 minutes. Then, the oxidized molybdenum carbide was added to the above mixed solution. Under nitrogen protection, the mixture was refluxed at 80-83℃ for 4 hours with stirring. After the reaction was completed, the modified molybdenum carbide was obtained through post-treatment. (3) Preparation of modified barium fluoride ① Barium fluoride was ultrasonically treated in anhydrous ethanol for 15-20 min, then an ethanol solution of tetraethyl orthosilicate was added dropwise, and ammonia was added. The mixture was stirred and reacted at room temperature for 3.8-4 h. After filtration and post-treatment, silica-coated barium fluoride was obtained. ② Add perfluorooctyltriethoxysilane to a mixture of water and toluene and sonicate at room temperature for 3-5 minutes. Then add the silica-coated barium fluoride prepared in ① and reflux at 65-70℃ for 4 hours under nitrogen protection and mechanical stirring. Then, after post-treatment, modified barium fluoride is obtained. (4) Preparation of modified PTFE wear-resistant materials ① The PTFE resin was vacuum dried at 77-80℃ for 4 hours, and the modified chromium corundum powder, modified molybdenum carbide and modified barium fluoride were vacuum dried at 77-80℃ for 6 hours. Then the dried PTFE resin, modified chromium corundum powder, modified molybdenum carbide and modified barium fluoride were mixed evenly in a mixer and passed through a 40-mesh sieve to prepare a mixture. ② After pressing the mixture into shape, it is sintered to prepare modified PTFE wear-resistant material.

2. The method for preparing the modified PTFE wear-resistant material according to claim 1, characterized in that: In step (1), the mass of perfluorooctyltriethoxysilane accounts for 5-6% of the mass of chromium corundum micro powder; The mass concentration of the toluene solution of perfluorooctyltriethoxysilane in step (1) is 5%; The rinsing in step (1) involves rinsing with toluene 3-5 times, the drying involves vacuum drying at 100°C for 2 hours, the cooling involves cooling to room temperature, and the sieving involves passing through a 200-mesh sieve.

3. The method for preparing the modified PTFE wear-resistant material according to claim 1, characterized in that: In step (2)①, the mass-volume ratio of molybdenum carbide to acetone is 1:8, with units of g / mL. After ultrasonic treatment with acetone for 15-20 min, washing with deionized water 3-5 times, and vacuum drying at 80-85℃ for 2 h, pretreated molybdenum carbide is obtained. The concentration of the nitric acid solution mentioned in step (2) ① is 8 mol / L, and the stirring speed is 300 r / min; The post-treatment described in step (2) ① is to immediately pour the reaction solution into ice water to quench it after the reaction is completed. The volume of the ice water is 10 times the volume of the nitric acid solution and the temperature of the ice water is 0℃. Then, filter it, wash it with deionized water until pH=6, rinse it once with sodium bicarbonate with a mass concentration of 0.84%, wash it with water 3-5 times, and finally dry it under vacuum at 80-85℃ for 12 hours and cool it to room temperature. In step (2)①, the mass-to-volume ratio of pretreated molybdenum carbide to nitric acid solution is 1:15, with units of g / mL.

4. The method for preparing the modified PTFE wear-resistant material according to claim 1, characterized in that: In step (2) ②, the mass ratio of toluene to oxidized molybdenum carbide is 1:1; In step ②, the mass ratio of deionized water to perfluorooctyltriethoxysilane is 1:1; In step (2) ②, the mass of perfluorooctyltriethoxysilane accounts for 5-6% of the mass of molybdenum carbide after oxidation treatment; In step (2) ②, the mechanical stirring speed is 300 r / min; The post-treatment described in step (2) ② is to cool the reaction to 38-40℃ after the reaction is completed, then filter the filter cake, wash it with toluene 3-5 times, wash it with sodium bicarbonate with a mass concentration of 0.1% once, wash it with deionized water 3-5 times, and finally dry it at 80℃ for 12 hours under vacuum, cool it to room temperature, and pass it through a 200-mesh sieve.

5. The method for preparing the modified PTFE wear-resistant material according to claim 1, characterized in that: In step (3)①, the mass-to-volume ratio of barium fluoride to anhydrous ethanol is 1:4, with units of g / mL; Step (3) ① The mass-to-volume ratio of tetraethyl orthosilicate to ethanol in the ethanol solution of tetraethyl orthosilicate is 1:10, and the unit is g / mL; In step (3) ①, the mass of tetraethyl orthosilicate accounts for 10% of the mass of barium fluoride; In step (3)①, the mass concentration of ammonia water is 25%. Ammonia water is added dropwise to adjust the pH value of the reaction system to 10, and the stirring speed is 300 r / min. The post-treatment described in step (3) ① involves rinsing with ethanol 3-5 times to remove free SiO2 sol, followed by vacuum drying at 80℃ for 1.5h.

6. The method for preparing the modified PTFE wear-resistant material according to claim 1, characterized in that: In step (3) ②, the mass ratio of water to perfluorooctyltriethoxysilane is 1:8; In step (3) ②, the mass-to-volume ratio of perfluorooctyltriethoxysilane to toluene is 1:4; In step (3) ②, the mass of perfluorooctyltriethoxysilane accounts for 5-6% of the mass of barium fluoride coated with silica; In step (3) ②, the stirring speed is 300 r / min; In step (3) ②, the post-treatment involves vacuum filtration at 40℃ while hot, followed by washing the resulting filter cake three times with toluene, once with a sodium bicarbonate solution of 0.1% by mass, washing it three to five times with deionized water, and finally vacuum drying at 80℃ for 12 hours, cooling it to room temperature, and passing it through a 200-mesh sieve.

7. The method for preparing the modified PTFE wear-resistant material according to claim 1, characterized in that: In step (4)①, the mixing temperature is 20℃ and the mixing time is 20min.

8. The method for preparing the modified PTFE wear-resistant material according to claim 1, characterized in that: The PTFE wear-resistant material mentioned in step (4) ① is composed of the following raw materials by mass: 80 parts PTFE resin, 9-11 parts modified chromium corundum micro powder, 5-7 parts modified molybdenum carbide, and 4 parts modified barium fluoride.

9. The method for preparing the modified PTFE wear-resistant material according to claim 1, characterized in that: In step (4) ②, the pressing pressure is 45 MPa and the pressing time is 20 min.

10. The method for preparing the modified PTFE wear-resistant material according to claim 1, characterized in that: The sintering described in step (4) ② involves heating the temperature to 365-370℃ at a rate of 1℃ / min and holding it for 2 hours, then cooling it down to 200℃ at a rate of 1℃ / min, and finally allowing it to cool naturally to room temperature.

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