A modified graphene PTFE-based coating and its preparation method

Abstract

The present invention relates to the field of coating technologies, and particularly to a modified graphene PTFE-based coating. A modified graphene PTFE-based coating, the raw materials of which are, by weight: 40-80 parts of PTFE powder, 1-10 parts of coupling agent, 5-15 parts of aramid, 0.5-8 parts of graphene, 70-90 parts of copper nitrate trihydrate, and 15-25 parts of polyimide. Copper nitrate trihydrate is used to prepare copper-coated graphene powder by mixing with graphene, and the coupling agent is used to modify the copper-coated graphene powder to obtain modified graphene powder. The coupling agent is one or more of heptadecafluorodecyltriethoxysilane, γ-aminopropyltriethoxysilane, and tridecafluorooctyltriethoxysilane. In the present invention, a coupling agent is used to couple and modify copper-coated graphene, improving the compatibility between modified PTFE and the filler, so that the interfacial bonding between PTFE and the filler is closer, enhancing its wear resistance. In addition, the coupling agent can also greatly reduce the micropores and crack defects of the PTFE matrix itself, thereby improving the corrosion resistance of the prepared PTFE-based coating.

Description

Technical Field

[0001] The present invention relates to the technical field of coatings, and particularly to a modified graphene PTFE-based coating and a preparation method thereof. Background Art

[0002] In the marine field, due to the high corrosiveness and complex mechanical stress of seawater, in the fields of marine engineering and shipbuilding, traditional materials are difficult to meet the long-term use requirements. The PTFE-based three-layer self-lubricating composite material consists of a metal matrix, an intermediate bonding layer, and a PTFE-based coating. Among them, the metal matrix can provide mechanical strength, the intermediate bonding layer can ensure firm interlayer bonding, and the PTFE-based coating can provide certain self-lubricating and wear-resistant properties. If this material is applied to the seawater field, although it can reduce the friction and wear of mechanical components to a certain extent, its wear resistance still cannot meet the requirements for long-term application in the seawater field.

[0003] Due to the high corrosiveness of seawater, and the internal structure of the existing PTFE-based coating is relatively loose. After long-term use, the corrosive medium in seawater easily penetrates into the metal matrix, resulting in the corrosion of the substrate coated with the PTFE-based coating. Graphene, as a nanoscale material, has excellent mechanical strength and corrosion resistance. When graphene is added to the PTFE matrix, it can significantly improve the wear resistance and mechanical properties of the prepared coating, while maintaining the original chemical corrosion resistance and low friction coefficient characteristics of the PTFE matrix. However, the following problems will occur in the process of graphene enhancing the performance of the PTFE-based coating in the existing technology: First, graphene is prone to agglomeration and cannot be well dispersed when added to the PTFE matrix. As a result, after the prepared coating is applied to the substrate, the wear resistance and mechanical properties of different parts of the substrate vary greatly. Second, the interfacial bonding between graphene and the PTFE matrix is weak, resulting in poor adhesion between graphene and the PTFE matrix. Third, the PTFE matrix itself has many micropores and cracks. Among them, the first and second problems will seriously affect the wear resistance of the prepared PTFE-based coating, and the third problem will cause the corrosive medium in seawater to penetrate through the PTFE matrix to the metal matrix, resulting in the substrate (i.e., the metal matrix) coated with the PTFE-based coating being still easily corroded by seawater in the seawater environment, thus resulting in poor corrosion resistance. Summary of the Invention

[0004] In order to solve the problems of poor wear resistance and corrosion resistance of the PTFE-based coating in the existing technology, the present invention provides a modified graphene PTFE-based coating.

[0005] To achieve the above object, the technical solution adopted by the present invention is as follows: A modified graphene PTFE-based coating, and its raw materials are by weight: 40-80 parts of PTFE powder, 1-10 parts of coupling agent, 5-15 parts of aramid, 0.5-8 parts of graphene, 70-90 parts of copper nitrate trihydrate, and 15-25 parts of polyimide.

[0006] As a further improvement of the above solution, the copper nitrate trihydrate is used to be mixed with the graphene to prepare copper-coated graphene powder, and the coupling agent is used to modify the copper-coated graphene powder to obtain modified graphene powder.

[0007] As a further improvement of the above solution, the coupling agent is one or more of heptadecafluorodecyltriethoxysilane, γ-aminopropyltriethoxysilane, and tridecafluorooctyltriethoxysilane.

[0008] As a further improvement of the above solution, the coupling agent is used to respectively improve the interfacial bonding force between the aramid and the PTFE, the interfacial bonding force between the graphene and the PTFE, and the interfacial bonding force between the polyimide and the PTFE.

[0009] As a further improvement of the above solution, the particle size of the graphene is 2μm - 7μm.

[0010] A preparation method of a modified graphene PTFE-based coating, which includes the following steps:

[0011] Prepare copper-coated graphene powder;

[0012] Add the coupling agent into absolute ethanol, stir to dissolve it to obtain a first mixed solution, then add the prepared copper-coated graphene powder into the first mixed solution, and perform ultrasonic treatment and stirring on it to obtain a second mixed solution; then adjust the pH of the second mixed solution with hydrochloric acid so that the pH of the second mixed solution is 4-5; then heat the second mixed solution in a water bath and cool it to room temperature, wash and filter it with deionized water, and obtain the modified graphene powder after vacuum drying;

[0013] Add the modified graphene powder into the PTFE dispersion liquid, and perform stirring, filtering, and drying in sequence to obtain a modified graphene PTFE composite powder;

[0014] Add aramid and polyimide into the modified graphene PTFE composite powder respectively, and mix them evenly to obtain a mixed mud;

[0015] Spread the mixed mud evenly on a copper powder plate, and roll it with a rolling mill to obtain a plate with the mixed mud coated on the surface;

[0016] Next, place the board with the mixed mud on its surface layer into a sintering device for plasticization. The plasticization temperature is 370 °C, the plasticization time is 4 h, and the heating rate is 10 °C / min. After sintering is completed, it is cooled to room temperature with the sintering device, and thus the board with the modified graphene PTFE-based coating is obtained.

[0017] As a further improvement of the above solution, the copper-coated graphene powder is prepared by an in-situ generation method.

[0018] As a further improvement of the above solution, the preparation of the copper-coated graphene powder includes the following steps:

[0019] Disperse graphene in 600 mL of ethanol solution, and after ultrasonic treatment, perform magnetic stirring to obtain a mixed solution III;

[0020] Sequentially add copper nitrate trihydrate and glucose solution to the mixed solution III, and stir for a period of time to obtain a mixed solution IV;

[0021] Add a 5 mol / L NaOH solution with a volume of 500 mL dropwise to the mixed solution IV in three portions. After the addition is completed, stir for 3 hours, then filter the stirred solution to obtain a solid product; wash the solid product with deionized water multiple times and filter it by suction and dry it to obtain the copper-coated graphene powder.

[0022] As a further improvement of the above solution, the PTFE dispersion is obtained by adding PTFE powder to distilled water and performing mechanical stirring while ultrasonic dispersing for 2 h.

[0023] As a further improvement of the above solution, the adjusted mixed solution II reacts in a water bath at 50 °C for 30 min, then the temperature is raised to 70 °C and reacts for 30 min, and finally it is cooled to room temperature.

[0024] As a further improvement of the above solution, the cooled mixed solution II is washed and filtered 3 times with deionized water and dried in vacuum at 60 °C, and the modified graphene powder is obtained after drying.

[0025] As a further improvement of the above solution, after adding the prepared modified graphene powder to the PTFE dispersion, perform mechanical stirring for 1 h, then vacuum filter, and finally dry at 100 °C for 9 h to obtain the modified graphene PTFE composite powder.

[0026] A modified graphene PTFE-based composite board, which includes a modified graphene PTFE-based coating prepared by the above preparation method.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] (1) In the present invention, a coupling agent is used to couple and modify copper-coated graphene, improving the coverage rate of graphene on the PTFE surface, improving the micropores and crack defects of the PTFE matrix itself, and enhancing the corrosion resistance of the prepared PTFE-based coating.

[0029] (2) The present invention prepares copper-coated graphene powder by in-situ generation method, enabling copper nanoparticles to be evenly distributed on the surface and folds of graphene sheets, improving the dispersibility of graphene, and enhancing the wear resistance of the prepared PTFE-based coating.

[0030] (3) By coating copper nanoparticles on the surface of graphene, the present invention can effectively improve the interfacial bonding force between graphene and the PTFE matrix, thereby enhancing the bonding force between the PTFE matrix and the filler in the prepared PTFE-based coating, and thus improving its wear resistance.

[0031] (4) The PTFE-based coating prepared by the present invention has good wear resistance and corrosion resistance, and can be applied to equipment in the marine field. By coating the PTFE-based coating prepared by the present invention on some devices in the marine field, the wear resistance and corrosion resistance of these devices can be improved, avoiding the corrosion that is likely to occur due to long-term immersion in seawater, and thus extending the service life of these devices. Description of the Drawings

[0032] Figure 1 It is the microscopic morphology diagram of the graphene powder in the present invention.

[0033] Figure 2 It is the microscopic morphology diagram of the prepared copper-coated graphene powder in the present invention.

[0034] Figure 3 It is the hardness curve diagram of the composite plates corresponding to the PTFE-based coatings prepared in different embodiments of the present invention.

[0035] Figure 4 It is the friction curve diagram of the composite plates corresponding to the PTFE-based coatings prepared in different embodiments of the present invention.

[0036] Figure 5 It is the bar chart of the wear rate of the composite plates corresponding to the PTFE-based coatings prepared in different embodiments of the present invention.

[0037] Figure 6 It is the wear scar morphology diagram of the composite plate coated with the PTFE-based coating prepared in Example 8 of the present invention.

[0038] Figure 7 It is the wear scar morphology diagram of the composite plate coated with the PTFE-based coating prepared in Example 9 of the present invention.

[0039] Figure 8 This is the abrasion scar morphology diagram of the composite board coated with the PTFE-based coating prepared in Example 5 of the present invention.

[0040] Figure 9 This is the abrasion scar morphology diagram of the composite board coated with the PTFE-based coating prepared in Comparative Example 3 of the present invention.

[0041] Figure 10 This is the surface morphology diagram of the PTFE-based coating in the composite board prepared in Example 5 of the present invention.

[0042] Figure 11 This is the surface morphology diagram of the PTFE-based coating in the composite board prepared in Comparative Example 3 of the present invention.

[0043] Figure 12 This is the polarization curve diagram of the composite boards prepared in Example 5, Example 8, Example 9 and Comparative Example 3 of the present invention. Detailed implementation manners

[0044] Next, in combination with the detailed implementation manners, the present invention will be further described. It should be noted that, on the premise of no conflict, any combination of the following-described embodiments or technical features can form a new embodiment.

[0045] In the description of the present invention, it should be noted that for orientation terms, such as the terms "center", "horizontal", "vertical", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc., the orientation and position relationships indicated are based on the orientation or position relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and should not be construed as limiting the specific protection scope of the present invention. The terms "first", "second", etc. in the description and claims of the present invention are used to distinguish similar objects and do not necessarily describe a specific order or sequence. The terms "include" and "have" in the description and claims of the present invention and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0046] Example 1

[0047] A modified graphene PTFE-based coating, the raw materials of which are by weight: 40-80 parts of PTFE powder, 1-10 parts of coupling agent, 5-15 parts of aramid, 0.5-8 parts of graphene, 70-90 parts of copper nitrate trihydrate, and 15-25 parts of polyimide.

[0048] Among them, the coupling agent is one or more of heptadecafluorodecyltriethoxysilane, γ-aminopropyltriethoxysilane, and tridecafluorooctyltriethoxysilane. In this embodiment, the copper-plated graphene is modified by using a coupling agent, so that the number of micropores and crack defects in the PTFE matrix is greatly reduced, thereby improving the corrosion resistance of the PTFE-based coating.

[0049] Specifically, both heptadecafluorodecyltriethoxysilane and tridecafluorooctyltriethoxysilane are fluorine-based coupling agents. Their C-F groups are extremely similar to the C-F groups in the PTFE matrix. Therefore, during the mixing process, according to the principle of like dissolves like, the compatibility between PTFE and fillers (i.e., graphene, aramid, and polyimide) is modified by the fluorine-based coupling agent, so that the interfacial bonding between PTFE and fillers is tighter, improving its wear resistance. At the same time, the coupling agent can also greatly reduce the micropores and crack defects of the PTFE matrix itself, thereby improving the corrosion resistance of the prepared PTFE-based coating. The improvement of corrosion resistance enables the prepared coating to be applied to devices in the marine field, thereby improving the corrosion resistance of these devices. The wear resistance and corrosion resistance of the equipment in the marine field coated with this coating are greatly improved.

[0050] γ-aminopropyltriethoxysilane is an amino coupling agent. The fluorine atoms on the surface of PTFE will repel the unshared electrons of the amino N, making it far away from the fluorine atoms, while the H atoms in the amino group are attracted by the F atoms and accept the unshared electron pair on the surface of the F atoms, thus forming an intermolecular hydrogen bond, greatly reducing the repulsive force between the surface of polytetrafluoroethylene, and improving the organic-inorganic interfacial bonding strength. As a result, the micropores and cracks in the prepared PTFE-based coating are reduced, and the corrosion resistance of the prepared PTFE-based coating is improved.

[0051] In addition, in this embodiment, the copper nanoparticles are evenly adsorbed on the surface of graphene or embedded in the graphene sheets, so that the number of graphene layers is small and there is no agglomeration phenomenon. In addition, the copper nanoparticles can effectively inhibit the agglomeration of graphene under the van der Waals force. The reason is that the thinner graphene layer can provide adsorption sites for copper ions, which is beneficial to the generation of copper nanoparticles, and these reactive adsorption sites will limit the aggregation of graphene, enhancing the dispersion of graphene in PTFE, thereby improving the wear resistance of the prepared PTFE-based coating.

[0052] The particle size of graphene is 2μm - 7μm.

[0053] Example 2

[0054] A preparation method of a modified graphene PTFE-based coating, which comprises the following steps:

[0055] Preparing copper-coated graphene powder:

[0056] Adding a coupling agent into absolute ethanol, stirring to dissolve it to obtain a first mixed solution, then adding the prepared copper-coated graphene powder into the first mixed solution, and performing ultrasonic treatment and stirring on it to obtain a second mixed solution; then adjusting the pH of the second mixed solution with hydrochloric acid so that the pH of the second mixed solution is 4-5; then heating the second mixed solution in a water bath and cooling it to room temperature, washing and filtering with deionized water, and drying it under vacuum to obtain modified graphene powder.

[0057] Adding the modified graphene powder into a PTFE dispersion liquid, and sequentially performing stirring, filtering and drying to obtain a modified graphene PTFE composite powder.

[0058] Adding aramid and polyimide into the modified graphene PTFE composite powder respectively, and mixing evenly to obtain a mixed mud.

[0059] Spreading the mixed mud evenly on a copper powder plate, and rolling it with a rolling mill to obtain a plate with the mixed mud coated on the surface layer.

[0060] Then putting the plate with the mixed mud coated on the surface layer into a sintering device for plasticizing, the plasticizing temperature is 370 °C, the plasticizing time is 4 h, the heating rate is 10 °C / min, and after sintering is completed, it is cooled to room temperature along with the sintering device, thus obtaining a plate with a modified graphene PTFE-based coating.

[0061] Among them, the sintering device can be a muffle furnace.

[0062] After rolling with a rolling mill, a plate with a total thickness of 2.1 mm and a surface layer thickness of 0.1 mm of the mixed mud can be obtained.

[0063] When the plate with the mixed mud coated on the surface layer is put into the sintering device for plasticizing, a protective gas needs to be introduced into the sintering device, and the protective gas can be nitrogen with a purity of more than 99.9%.

[0064] Among them, the copper-coated graphene powder is prepared by an in-situ generation method, and the specific steps are as follows:

[0065] Dispersing graphene in 600 mL of an ethanol solution, performing ultrasonic treatment and then magnetic stirring to obtain a third mixed solution.

[0066] Sequentially adding copper nitrate trihydrate and a glucose solution into the third mixed solution, and stirring for a period of time to obtain a fourth mixed solution.

[0067] Add the NaOH solution with a concentration of 5 mol / L and a volume of 500 mL to the fourth mixture in three portions. After the addition is completed, stir for 3 hours, and then filter the stirred solution to obtain a solid product. Wash the solid product with deionized water multiple times and filter it by suction and dry it to obtain copper-coated graphene powder.

[0068] Among them, the PTFE dispersion is obtained by adding PTFE powder to distilled water and performing mechanical stirring while ultrasonically dispersing for 2 h.

[0069] Example 3

[0070] A preparation method of a modified graphene PTFE-based coating, which comprises the following steps:

[0071] (1) First, disperse 8 g of graphene in 600 ml of ethanol solution, ultrasonically stir for 10 min, and then magnetically stir for 5 min.

[0072] (2) Then, successively add 90 g of Cu(NO3)2·3H2O and a C6H 12 O6·H2O solution with a volume of 300 ml and a concentration of 1.25 mol / L, and stir for about 2 hours.

[0073] (3) Add 500 ml of 5 mol / L NaOH in 3 portions to the solution in step (2). After the addition is completed, stir in a magnetic stirrer for 3 hours. Wash the obtained product with deionized water and filter it by suction, and dry it at 80 °C for 9 h. Repeat this process three times to obtain copper-coated graphene powder.

[0074] (4) Add 1 g of heptadecafluorodecyltriethoxysilane to anhydrous ethanol and stir to dissolve it.

[0075] (5) Add the copper-coated graphene powder prepared in step (3) to the solution in step (4), ultrasonically stir for 10 min first and then stir for 1 h, and finally adjust the pH of the solution with hydrochloric acid to make its pH 4-5.

[0076] (6) Place the solution with the adjusted pH value in a water bath at 50 °C and react for 30 min. Then, raise the temperature of the water bath to 70 °C and react for 30 min, and cool to room temperature.

[0077] (7) Wash and filter the solution cooled in step (6) with deionized water 3 times, and then dry it in a vacuum at 60 °C to obtain modified graphene powder.

[0078] (8) Add 60 g of PTFE powder to 100 g of distilled water, perform mechanical stirring while ultrasonically dispersing for 2 h to obtain a PTFE dispersion.

[0079] (9) Add the modified graphene powder in step (7) to the PTFE dispersion in step (8), then mechanically stir for 1 h, followed by vacuum filtration. After filtration, dry at 100 °C for 9 h to obtain the modified graphene / PTFE composite powder.

[0080] (10) Add 10 g of aramid and 20 g of polyimide to the modified graphene / PTFE composite powder respectively, and then stir in a high-speed mixer for 30 min. After mixing evenly, a mixed mud is obtained.

[0081] (11) Spread the mixed mud prepared in step (10) evenly on a copper powder plate, and roll it using a rolling mill to obtain a plate with a total thickness of 2.1 mm and a thickness of 0.1 mm for the surface layer coated with the mixed mud.

[0082] (12) Then put the plate with the surface layer coated with the mixed mud into a muffle furnace under a protective atmosphere for plasticization. The plasticization temperature is 370 °C, the plasticization time is 4 h, the heating rate is 10 °C / min, and the protective atmosphere is nitrogen with a purity of more than 99.9%. After sintering is completed, cool it to room temperature with the furnace, and a plate with a modified graphene PTFE-based coating is obtained.

[0083] Example 4

[0084] A preparation method of a modified graphene PTFE-based coating, which comprises the following steps:

[0085] (1) First, disperse 6 g of graphene in 600 ml of ethanol solution, ultrasonic for 10 min and then magnetically stir for 5 min.

[0086] (2) Then add 85 g of Cu(NO3)2·3H2O and a C6H 12 O6·H2O solution with a volume of 300 ml and a concentration of 1.25 mol / L in sequence, and stir for about 2 hours.

[0087] (3) Add 500 ml of 5 mol / L NaOH dropwise to the solution in step (2) in 3 portions. After the addition is completed, stir in a magnetic stirrer for 3 hours. Then wash the obtained product with deionized water and filter it, and dry it at 80 °C for 9 h. This process is repeated three times to obtain copper-coated graphene powder.

[0088] (4) Add 2 g of 1,1,2,2,3,3,4,4,5,5,6,6,7,7,7-heptadecafluorodecyltriethoxysilane to absolute ethanol and stir to dissolve it.

[0089] (5) Add the copper-coated graphene powder prepared in step (3) to the solution in step (4), ultrasonic for 10 min first and then stir for 1 h, and finally adjust the pH of the solution with hydrochloric acid to make its pH 4-5.

[0090] (6) Place the solution with adjusted pH value in a water bath at 50 °C and react for 30 min. Then raise the temperature of the water bath to 70 °C and react for 30 min. Cool to room temperature.

[0091] (7) Wash and filter the solution cooled in step (6) three times with deionized water, and then dry it in vacuum at 60 °C to obtain modified graphene powder.

[0092] (8) Add 60 g of PTFE powder to 100 g of distilled water, and mechanically stir and ultrasonically disperse for 2 h to obtain a PTFE dispersion.

[0093] (9) Add the modified graphene powder in step (7) to the PTFE dispersion in step (8), then mechanically stir for 1 h, and then vacuum filter. After vacuum filtration, dry at 100 °C for 9 h to obtain modified graphene / PTFE composite powder.

[0094] (10) Add 10 g of aramid and 20 g of polyimide to the modified graphene / PTFE composite powder respectively, and then stir in a high-speed mixer for 30 min. After mixing evenly, a mixed mud is obtained.

[0095] (11) Spread the mixed mud prepared in step (10) evenly on a copper powder plate, and roll it with a rolling mill to obtain a plate with a total thickness of 2.1 mm and a thickness of 0.1 mm of the mixed mud coated on the surface layer.

[0096] (12) Then put the plate with the mixed mud coated on the surface layer into a muffle furnace under a protective atmosphere for plasticization. The plasticization temperature is 370 °C, the plasticization time is 4 h, the heating rate is 10 °C / min, and the protective atmosphere is nitrogen with a purity of more than 99.9%. After sintering, cool to room temperature with the furnace to obtain a plate with a modified graphene PTFE-based coating.

[0097] Example 5

[0098] A preparation method of a modified graphene PTFE-based coating, which comprises the following steps:

[0099] (1) First, disperse 4 g of graphene in 600 ml of ethanol solution, ultrasonic for 10 min and then magnetic stir for 5 min.

[0100] (2) Then add 80 g of Cu(NO3)2·3H2O and a C6H 12 O6·H2O solution with a volume of 300 ml and a concentration of 1.25 mol / L in sequence, and stir for about 2 hours.

[0101] (3) Add 500 ml of NaOH with a concentration of 5 mol / L dropwise to the solution in step (2) in three portions. After the addition is completed, stir in a magnetic stirrer for 3 hours. Then wash the resulting product with deionized water and filter by suction, and dry it at 80 °C for 9 h. Repeat this process three times to obtain copper-coated graphene powder.

[0102] (4) Add 5 g of 1,1,2,2,3,3,4,4,5,5,6,6,7,7,7 - heptadecafluorodecyltriethoxysilane to anhydrous ethanol and stir to dissolve it.

[0103] (5) Add the copper-coated graphene powder prepared in step (3) to the solution in step (4), ultrasonicate for 10 min first and then stir for 1 h, and finally adjust the pH of the solution with hydrochloric acid to make its pH 4 - 5.

[0104] (6) Place the solution with the adjusted pH value in a water bath at 50 °C and react for 30 min. Then raise the temperature of the water bath to 70 °C and react for 30 min, and cool to room temperature.

[0105] (7) Wash and filter the solution cooled in step (6) three times with deionized water, and then dry it in a vacuum at 60 °C to obtain modified graphene powder.

[0106] (8) Add 60 g of PTFE powder to 100 g of distilled water, and mechanically stir and ultrasonically disperse for 2 h to obtain a PTFE dispersion.

[0107] (9) Add the modified graphene powder in step (7) to the PTFE dispersion in step (8), then mechanically stir for 1 h, and then filter by suction. After suction filtration, dry it at 100 °C for 9 h to obtain modified graphene / PTFE composite powder.

[0108] (10) Add 10 g of aramid and 20 g of polyimide to the modified graphene / PTFE composite powder respectively, and then stir in a high-speed mixer for 30 min. After mixing evenly, obtain a mixed mud.

[0109] (11) Spread the mixed mud prepared in step (10) evenly on a copper powder plate and roll it with a rolling mill to obtain a plate with a total thickness of 2.1 mm and a thickness of 0.1 mm for the surface layer coated with the mixed mud.

[0110] (12) Then place the plate with the surface layer coated with the mixed mud into a muffle furnace under a protective atmosphere for plasticization. The plasticization temperature is 370 °C, the plasticization time is 4 h, the heating rate is 10 °C / min, and the protective atmosphere is nitrogen with a purity of more than 99.9%. After sintering is completed, cool it to room temperature with the furnace, and then obtain a plate with a modified graphene PTFE-based coating.

[0111] Example 6

[0112] A preparation method of a modified graphene PTFE-based coating, which comprises the following steps:

[0113] (1) First, disperse 2 g of graphene in 600 ml of ethanol solution, ultrasonic for 10 min and then stir magnetically for 5 min.

[0114] (2) Then, add 75 g of Cu(NO3)2·3H2O and a C6H 12 O6·H2O solution with a volume of 300 ml and a concentration of 1.25 mol / L in sequence, and stir for about 2 hours.

[0115] (3) Drop 500 ml of 5 mol / L NaOH into the solution in step (2) in 3 portions. After the dropping is completed, stir in a magnetic stirrer for 3 hours. Then wash the obtained product with deionized water and filter by suction, and dry it at 80 °C for 9 h. This process is repeated three times to obtain copper-coated graphene powder.

[0116] (4) Add 8 g of heptadecafluorodecyltriethoxysilane to anhydrous ethanol and stir to dissolve it.

[0117] (5) Add the copper-coated graphene powder prepared in step (3) to the solution in step (4), ultrasonic for 10 min first and then stir for 1 h, and finally adjust the pH of the solution with hydrochloric acid to make its pH 4 - 5.

[0118] (6) Place the solution with the adjusted pH value in a water bath at 50 °C and react for 30 min. Then raise the temperature of the water bath to 70 °C and react for 30 min, and cool to room temperature.

[0119] (7) Wash and filter the solution cooled in step (6) with deionized water 3 times, and then dry it in vacuum at 60 °C to obtain modified graphene powder.

[0120] (8) Add 60 g of PTFE powder to 100 g of distilled water, stir mechanically and disperse ultrasonically for 2 h to obtain a PTFE dispersion.

[0121] (9) Add the modified graphene powder in step (7) to the PTFE dispersion in step (8), then stir mechanically for 1 h, and then filter by vacuum. After filtration, dry it at 100 °C for 9 h to obtain modified graphene / PTFE composite powder.

[0122] (10) Add 10 g of aramid and 20 g of polyimide to the modified graphene / PTFE composite powder respectively, and then stir in a high-speed mixer for 30 min. After mixing evenly, obtain a mixed mud.

[0123] (11) Spread the mixed mud obtained in step (10) evenly on the copper powder plate and roll it using a rolling mill to obtain a plate with a total thickness of 2.1 mm and a thickness of 0.1 mm of the mixed mud coated on the surface layer.

[0124] (12) Then, put the plate with the mixed mud coated on the surface layer into a muffle furnace under a protective atmosphere for plasticization. The plasticization temperature is 370 °C, the plasticization time is 4 h, the heating rate is 10 °C / min, and the protective atmosphere is nitrogen with a purity of more than 99.9%. After sintering is completed, it is cooled to room temperature with the furnace, and the plate with the modified graphene PTFE-based coating is obtained.

[0125] Example 7

[0126] A preparation method of a modified graphene PTFE-based coating, which comprises the following steps:

[0127] (1) First, disperse 0.5 g of graphene in 600 ml of ethanol solution, ultrasonicate for 10 min, and then stir magnetically for 5 min.

[0128] (2) Then, add 70 g of Cu(NO3)2·3H2O and a C6H 12 O6·H2O solution with a volume of 300 ml and a concentration of 1.25 mol / L in sequence, and stir for about 2 hours.

[0129] (3) Add 500 ml of 5 mol / L NaOH dropwise to the solution in step (2) in 3 portions. After the addition is completed, stir in a magnetic stirrer for 3 hours. Then, wash the obtained product with deionized water and filter it by suction, and dry it at 80 °C for 9 h. This process is repeated three times to obtain copper-coated graphene powder.

[0130] (4) Add 10 g of 1H,1H,2H,2H-perfluorodecyltriethoxysilane to anhydrous ethanol and stir to dissolve it.

[0131] (5) Add the copper-coated graphene powder prepared in step (3) to the solution in step (4), ultrasonicate for 10 min first, then stir for 1 h, and finally adjust the pH of the solution with hydrochloric acid to make its pH 4 - 5.

[0132] (6) Place the solution with the adjusted pH value in a water bath at 50 °C and react for 30 min. Then, raise the temperature of the water bath to 70 °C and react for 30 min, and then cool to room temperature.

[0133] (7) Wash and filter the solution cooled in step (6) with deionized water 3 times, and then dry it in vacuum at 60 °C to obtain the modified graphene powder.

[0134] (8) Add 60 g of PTFE powder to 100 g of distilled water, mechanically stir and ultrasonically disperse for 2 h to obtain a PTFE dispersion.

[0135] (9) Add the modified graphene powder in step (7) to the PTFE dispersion in step (8), then mechanically stir for 1 h, and then perform vacuum filtration. After filtration, dry at 100 °C for 9 h to obtain the modified graphene / PTFE composite powder.

[0136] (10) Add 10 g of aramid and 20 g of polyimide to the modified graphene / PTFE composite powder respectively, and then stir in a high-speed mixer for 30 min. After mixing evenly, obtain the mixed mud.

[0137] (11) Spread the mixed mud prepared in step (10) evenly on the copper powder plate, and roll it with a rolling mill to obtain a plate with a total thickness of 2.1 mm and a thickness of 0.1 mm for the surface layer coated with the mixed mud.

[0138] (12) Then put the plate with the surface layer coated with the mixed mud into a muffle furnace under a protective atmosphere for plasticization. The plasticization temperature is 370 °C, the plasticization time is 4 h, the heating rate is 10 °C / min, and the protective atmosphere is nitrogen with a purity of more than 99.9%. After sintering is completed, cool it to room temperature with the furnace, and then obtain the plate with the modified graphene PTFE-based coating.

[0139] Example 8

[0140] A preparation method of a modified graphene PTFE-based coating, which comprises the following steps:

[0141] (1) First, disperse 4 g of graphene in 600 ml of ethanol solution, ultrasonicate for 10 min and then magnetically stir for 5 min.

[0142] (2) Then add 80 g of Cu(NO3)2·3H2O and a C6H 12 O6·H2O solution with a volume of 300 ml and a concentration of 1.25 mol / L in sequence, and stir for about 2 hours.

[0143] (3) Add 500 ml of 5 mol / L NaOH dropwise to the solution in step (2) in 3 portions. After the addition is completed, stir in a magnetic stirrer for 3 hours. Then wash the obtained product with deionized water and perform suction filtration, and dry at 80 °C for 9 h. This process is repeated three times to obtain the copper-coated graphene powder.

[0144] (4) Add 5 g of γ-aminopropyltriethoxysilane to anhydrous ethanol and stir to dissolve it.

[0145] (5) Add the copper-coated graphene powder prepared in step (3) to the solution in step (4), ultrasonicate for 10 min first and then stir for 1 h, and finally adjust the pH of the solution with hydrochloric acid to make its pH 4 - 5.

[0146] (6) Place the solution with adjusted pH value in a water bath at 50 °C and react for 30 min. Then raise the temperature of the water bath to 70 °C and react for 30 min. Cool to room temperature.

[0147] (7) Wash and filter the solution cooled in step (6) three times with deionized water, and then dry it in vacuum at 60 °C to obtain the modified graphene powder.

[0148] (8) Add 60 g of PTFE powder to 100 g of distilled water, and mechanically stir and ultrasonically disperse for 2 h to obtain a PTFE dispersion.

[0149] (9) Add the modified graphene powder in step (7) to the PTFE dispersion in step (8), then mechanically stir for 1 h, and then vacuum filter. After vacuum filtration, dry at 100 °C for 9 h to obtain the modified graphene / PTFE composite powder.

[0150] (10) Add 10 g of aramid and 20 g of polyimide to the modified graphene / PTFE composite powder respectively, and then stir in a high-speed mixer for 30 min to obtain a mixed mud after mixing evenly.

[0151] (11) Spread the mixed mud prepared in step (10) evenly on a copper powder plate, and roll it with a rolling mill to obtain a plate with a total thickness of 2.1 mm and a thickness of 0.1 mm of the mixed mud coated on the surface layer.

[0152] (12) Then put the plate with the mixed mud coated on the surface layer into a muffle furnace under a protective atmosphere for plasticization. The plasticization temperature is 370 °C, the plasticization time is 4 h, the heating rate is 10 °C / min, and the protective atmosphere is nitrogen with a purity of more than 99.9%. After sintering, cool to room temperature with the furnace to obtain a plate with a modified graphene PTFE-based coating.

[0153] Example 9

[0154] A preparation method of a modified graphene PTFE-based coating, which comprises the following steps:

[0155] (1) First, disperse 4 g of graphene in 600 ml of ethanol solution, ultrasonic for 10 min and then magnetic stir for 5 min.

[0156] (2) Then add 80 g of Cu(NO3)2·3H2O and a C6H 12 O6·H2O solution with a volume of 300 ml and a concentration of 1.25 mol / L in sequence, and stir for about 2 hours.

[0157] (3) Add 500 ml of NaOH with a concentration of 5 mol / L dropwise to the solution in step (2) in three portions. After the addition is completed, stir in a magnetic stirrer for 3 hours. Then wash the resulting product with deionized water and perform suction filtration, and dry it at 80 °C for 9 h. Repeat this process three times to obtain copper-coated graphene powder.

[0158] (4) Add 2 g of tridecafluorooctyltriethoxysilane to anhydrous ethanol and stir to dissolve it.

[0159] (5) Add the copper-coated graphene powder prepared in step (3) to the solution in step (4), first ultrasonicate for 10 min and then stir for 1 h. Finally, adjust the pH of the solution with hydrochloric acid to make the pH 4 - 5.

[0160] (6) Place the solution with the adjusted pH value in a water bath at 50 °C and react for 30 min. Then raise the temperature of the water bath to 70 °C and react for 30 min, and cool to room temperature.

[0161] (7) Wash and filter the solution cooled in step (6) three times with deionized water, and then dry it in a vacuum at 60 °C to obtain modified graphene powder.

[0162] (8) Add 60 g of PTFE powder to 100 g of distilled water, and mechanically stir and ultrasonically disperse for 2 h to obtain a PTFE dispersion.

[0163] (9) Add the modified graphene powder in step (7) to the PTFE dispersion in step (8), then mechanically stir for 1 h, and then perform vacuum suction filtration. After suction filtration, dry it at 100 °C for 9 h to obtain modified graphene / PTFE composite powder.

[0164] (10) Add 10 g of aramid and 20 g of polyimide to the modified graphene / PTFE composite powder respectively, and then stir in a high-speed mixer for 30 min. After mixing evenly, obtain a mixed mud.

[0165] (11) Spread the mixed mud prepared in step (10) evenly on a copper powder plate and roll it with a rolling mill to obtain a plate with a total thickness of 2.1 mm and a thickness of 0.1 mm for the surface layer coated with the mixed mud.

[0166] (12) Then place the plate with the surface layer coated with the mixed mud into a muffle furnace in a protective atmosphere for plasticization. The plasticization temperature is 370 °C, the plasticization time is 4 h, the heating rate is 10 °C / min, and the protective atmosphere is nitrogen with a purity of more than 99.9%. After sintering is completed, cool it to room temperature with the furnace to obtain a plate with a modified graphene PTFE-based coating.

[0167] Comparative Example 1

[0168] A method for preparing a PTFE-based coating, comprising the following steps:

[0169] (1) Add 60 g of PTFE powder to 100 g of distilled water, and mechanically stir while ultrasonically dispersing for 2 h to obtain a PTFE dispersion.

[0170] (2) Add 10 g of aramid and 20 g of polyimide to the PTFE dispersion respectively, and stir in a high-speed mixer for 30 min. After mixing evenly, a mixed mud is obtained.

[0171] (3) Spread the mixed mud prepared in step (2) evenly on a copper powder plate, and roll it using a rolling mill to obtain a plate with a total thickness of 2.1 mm and a thickness of 0.1 mm of the mixed mud coated on the surface layer.

[0172] (4) Then put the plate with the mixed mud coated on the surface layer into a muffle furnace under a protective atmosphere for plasticization. The plasticization temperature is 370 °C, the plasticization time is 4 h, the heating rate is 10 °C / min, and the protective atmosphere is nitrogen with a purity of more than 99.9%. After sintering is completed, it is cooled to room temperature with the furnace, and the plate with a PTFE-based coating is obtained.

[0173] Comparative Example 2

[0174] A preparation method of a PTFE-based coating, comprising the following steps:

[0175] (1) Add 60 g of PTFE powder to 100 g of distilled water, and mechanically stir while ultrasonically dispersing for 2 h to obtain a PTFE dispersion.

[0176] (2) Add 4 g of graphene powder to the PTFE dispersion, mechanically stir for 1 h, perform vacuum filtration, and dry at 100 °C for 9 h to obtain a graphene / PTFE composite powder.

[0177] (3) Add 10 g of aramid and 20 g of polyimide to the graphene PTFE composite powder respectively, and stir in a high-speed mixer for 30 min. After mixing evenly, a mixed mud is obtained.

[0178] (4) Spread the mixed mud prepared in step (3) evenly on a copper powder plate, and roll it using a rolling mill to obtain a plate with a total thickness of 2.1 mm and a thickness of 0.1 mm of the mixed mud coated on the surface layer.

[0179] (5) Then put the plate with the mixed mud coated on the surface layer into a muffle furnace under a protective atmosphere for plasticization. The plasticization temperature is 370 °C, the plasticization time is 4 h, the heating rate is 10 °C / min, and the protective atmosphere is nitrogen with a purity of more than 99.9%. After sintering is completed, it is cooled to room temperature with the furnace, and the plate with a graphene PTFE-based coating is obtained.

[0180] Comparative Example 3

[0181] A preparation method of a PTFE-based coating, comprising the following steps:

[0182] First, disperse 4 g of graphene in 600 ml of ethanol solution, ultrasonicate for 10 min, and then magnetically stir for 5 min.

[0183] (2) Then, sequentially add 80 g of Cu(NO3)2·3H2O and a C6H 12 O6·H2O solution with a volume of 300 ml and a concentration of 1.25 mol / L, and stir for about 2 hours.

[0184] (3) Add 500 ml of 5 mol / L NaOH dropwise to the solution in step (2) in 3 portions. After the addition is completed, stir in a magnetic stirrer for 3 hours. Then wash the obtained product with deionized water and perform suction filtration, and dry it at 80 °C for 9 h. This process is repeated three times to obtain copper-coated graphene powder.

[0185] (4) Add 60 g of PTFE powder to 100 g of distilled water, mechanically stir while ultrasonically dispersing for 2 h to obtain a PTFE dispersion.

[0186] (5) Add the copper-coated graphene powder in step (3) to the PTFE dispersion in step (4), then mechanically stir for 1 h, and then perform vacuum suction filtration. After suction filtration, dry it at 100 °C for 9 h to obtain graphene / PTFE composite powder.

[0187] (6) Add 10 g of aramid and 20 g of polyimide to the graphene / PTFE composite powder respectively, and then stir in a high-speed mixer for 30 min. After mixing evenly, obtain a mixed mud.

[0188] (7) Spread the mixed mud prepared in step (6) evenly on a copper powder plate, and roll it using a rolling mill to obtain a plate with a total thickness of 2.1 mm and a thickness of 0.1 mm of the surface layer coated with the mixed mud.

[0189] (8) Then place the plate with the surface layer coated with the mixed mud into a muffle furnace under a protective atmosphere for plasticization. The plasticization temperature is 370 °C, the plasticization time is 4 h, the heating rate is 10 °C / min, and the protective atmosphere is nitrogen with a purity of more than 99.9%. After sintering is completed, cool it to room temperature with the furnace, and then obtain a plate with a graphene PTFE-based coating.

[0190] Now, perform surface hardness, friction and wear tests, and corrosion resistance tests on the PTFE-based coatings prepared in Examples 3-9 and Comparative Examples 1-3 respectively.

[0191] In the present invention, the hardness, friction and wear, and corrosion resistance of the substrate coated with the PTFE coating need to be tested to reflect these properties of the prepared PTFE-based coating.

[0192] The plates with PTFE-based coatings prepared in Examples 3-9 and the plates with PTFE-based coatings prepared in Comparative Examples 1-3 were subjected to hardness tests, friction and wear tests, and corrosion resistance tests.

[0193] Among them, for the hardness test, a Shore hardness tester (Type D) was used to measure the hardness of specimens with dimensions of 10 mm (length), 10 mm (width), and 2.1 mm (thickness). Measurements were taken at 5 positions on each specimen, with a load of 15 N and a holding time of 3 s, and the average hardness value was calculated. The variation range of the hardness value was within 10% of the average value.

[0194] For the friction and wear experiment, a pin-on-disk tribometer (HDM-200 type) was used to test the tribological properties of each group of coated specimens. The test device adopted a pin-on-disk contact form, and the counter-specimen material was 42CrMo. Five specimens were prepared for each example and comparative example, and the duration of each test was 60 min.

[0195] For the corrosion resistance test, an electrochemical workstation (Princeton PMC-1000A type) was used with a test frequency of 100 kHz to 10 mHz, an amplitude of 20 mV, and a scanning rate of 1 mV / s.

[0196] In the present invention, the friction and wear test and the corrosion resistance test of the composite plate coated with the PTFE-based coating were both carried out with seawater as the medium. Because only by carrying out the tests with seawater as the medium can it provide reference value for its later application in the marine field.

[0197] In the present invention, the filler refers to other raw materials except the PTFE matrix in the preparation of the PTFE-based coating. Specifically, it can be graphene, aramid, and polyimide.

[0198] During the preparation process, the properties of the intermediate products were also observed. Among them Figure 1 is the SEM image of the graphene powder (i.e., without any treatment of graphene) in the raw materials used in Examples 3-9 and Comparative Example 2. By observing Figure 1 it can be seen that the graphene powder has a semi-transparent sheet-like structure and no excessive stacking.

[0199] Figure 2 is the SEM image of the modified graphene powder prepared in Example 3. Among them, Figure 2 1 is graphene and 2 is copper nanoparticles. By observing Figure 2 it can be seen that Figure 2A large number of milky white copper nanoparticles are evenly adsorbed on the surface of graphene or embedded in the graphene sheets. The number of graphene layers is small, without agglomeration, and it shows an almost transparent form. By analyzing this figure, it can be seen that the thinner graphene layer can provide adsorption sites for copper ions, which is beneficial to the formation of copper nanoparticles. Moreover, after these adsorption sites adsorb copper ions, they also limit the aggregation of graphene. Thus, it can be proved that copper nanoparticles can effectively inhibit the agglomeration of graphene under van der Waals forces, enhance the dispersion of graphene in PTFE, and thereby improve the wear resistance of the prepared PTFE-based coating.

[0200] Figure 3 It is the Shore hardness broken line graph of the composite plates obtained in Examples 3-7 and Comparative Examples 1-2. By analyzing Figure 3 it can be seen that the maximum amount of graphene added in Example 3 is 8 g, and the hardness of its composite plate is also the largest, which is 94.6. Graphene was not added in Comparative Example 1, so its hardness is the smallest, which is 76.3. Thus, it is proved that graphene can increase the hardness of the prepared PTFE-based coating. And in the PTFE-based coatings prepared in Examples 3 to 7, as the amount of graphene added gradually decreases, the hardness of the composite plates also gradually decreases. Therefore, in the actual preparation process, the hardness of the prepared PTFE-based coating can be controlled by controlling the amount of graphene. And when the amount of graphene added reaches 4 g, the hardness of the composite plate reaches 92.7 at this time. From the broken line graph, it can be seen that from Example 3 to Example 5, as the amount of graphene increases, the increasing trend of its hardness weakens.

[0201] In addition, by analyzing Example 5 and Comparative Example 2, it can be seen that the amount of graphene added in Example 3 and Comparative Example 2 is the same. The difference is that graphene was modified in Example 3, while graphene was not modified in Comparative Example 2. The hardness of the composite plate in Example 5 is 92.7, and the hardness of the composite plate in Comparative Example 2 is 89.5. The difference in hardness between the two is not large. Therefore, it shows that the modification of graphene has little effect on its hardness.

[0202] Figure 4 It is the friction coefficient curve of the composite plates prepared in Examples 3-9 and Comparative Examples 1-2 of the present invention under dry friction conditions. Figure 5 It is the bar graph of the wear rate of the composite plates prepared in Examples 3-9 and Comparative Examples 1-2 of the present invention under dry friction conditions.

[0203] By analyzing Figure 4 and Figure 5Analysis shows that the friction coefficient and wear rate of Comparative Example 1 are the largest, indicating that the PTFE-based coating prepared in Comparative Example 1 has the worst friction and wear resistance. The main reason is that graphene is not added in Comparative Example 1. Therefore, adding graphene can effectively enhance the wear resistance of the prepared PTFE-based coating. In addition, the friction coefficients and wear rates of the composite plates in Examples 3-9 are lower than those of the composite plates in Comparative Examples 1-2. This shows that modified graphene has a significant enhancing effect on the friction and wear resistance of the PTFE-based coating.

[0204] By analyzing the friction coefficients and wear rates of the composite plates in Examples 5 to 8, it can be seen that when the addition amount of graphene is in the range of 0.5 g - 4 g, as the amount of graphene increases, the friction coefficient and wear rate of the composite plate gradually decrease. When the addition amount of graphene is 4 g, the friction coefficient and wear rate of the composite plate are the lowest. Specifically, the friction coefficient is 0.124 and the wear rate is 3.4×10 -5 mm 3 / Nm.

[0205] By analyzing Examples 3 to 5, it can be seen that when the addition amount of graphene increases from 4 g to 8 g, as the addition amount of graphene increases, the friction coefficient and wear rate of the composite plate increase. Therefore, in the actual operation process, the addition amount of graphene can be selected as 4 g, which can ensure that the prepared PTFE-based coating has good wear resistance.

[0206] Figures 6 to 9 Figure shows the surface morphologies of the worn track positions of the composite plates in different examples. Among them, Figure 6 Figure shows the surface morphology of the worn track position of the composite plate in Example 8; Figure 7 Figure shows the surface morphology of the worn track position of the composite plate in Example 9; Figure 8 Figure shows the surface morphology of the worn track position of the composite plate in Example 5; Figure 9 Figure shows the surface morphology of the worn track position of the composite plate in Comparative Example 3.

[0207] By analyzing Figures 6 to 9 it can be seen that compared with Examples 5, 8 and 9, Comparative Example 3 does not use a coupling agent. Combining with Figure 9 it can be known that the surface density of the worn track of the PTFE-based coating prepared in Comparative Example 3 is poor and there are many cracks. The main reason is that there is no coupling agent in Comparative Example 3, which will lead to poor interfacial bonding between the filler and the PTFE matrix. Under the action of friction force, it is easy for each filler to fall off from the PTFE matrix.

[0208] By comparing Figure 9 and Figure 6 it can be seen that Figure 6 the surface morphology of the worn track of the composite plate inFigure 9 The surface topography of the wear marks on the composite board is much flatter, and the crack propagation is also alleviated. This is because Figure 6 γ-aminopropyltriethoxysilane coupling agent is used in , and the fluorine atoms on the surface of the PTFE matrix will repel the unshared electrons of the amino N in the γ-aminopropyltriethoxysilane coupling agent, making it far away from the fluorine atoms. The H atoms in the amino group are attracted by the fluorine atoms and accept the unshared electron pair on the surface of the fluorine atoms, thus forming an intermolecular hydrogen bond, greatly reducing the repulsive force between the filler and the PTFE substrate, improving the organic-inorganic interface bonding strength, and thus achieving the improvement of its wear resistance. It can be seen from this that the wear resistance of the PTFE-based coating prepared by adding the coupling agent is much better than that of the PTFE-based coating without addition.

[0209] By comparing Figure 6 , Figure 7 and Figure 8 , it can be known that Figure 7 and Figure 8 compared with Figure 6 , the surface topography of the wear marks on the composite board in Figure 4 and Figure 5 is much lighter, and there are fewer cracks and pores, and the result is denser. The main reason is that the PTFE-based coatings in Example 9 and Example 5 both use fluorine-based coupling agents, and the C-F groups in the fluorine-based coupling agents are very similar to the C-F groups in the PTFE matrix. Therefore, in the mixing process, according to the principle of similar compatibility, the PTFE matrix modified with the fluorine-based coupling agent and the fillers (i.e., graphene, aramid, and polyimide) have good compatibility. For the PTFE-based coating modified with the fluorine-based coupling agent, during the sintering and plasticizing process, the C-F bond in the fluorine group has a higher compatibility between the filler and the PTFE matrix than the hydrogen bond in the amino group of the amino coupling agent. By combining

[0210] Figure 10 It can be known that the friction coefficient and wear rate of the composite board coated with the PTFE-based coatings in Example 9 and Example 5 are significantly lower than those in Example 8. From this, it can be concluded that during the preparation of the PTFE-based coating, the wear resistance of the PTFE-based coating prepared by adding the fluorine-based coupling agent is higher than that of the PTFE-based coating prepared by adding the amino coupling agent.

[0210] Figure 10 is the surface topography of the PTFE-based coating of the composite board in Example 5; Figure 11 is the surface topography of the PTFE-based coating of the composite board in Comparative Example 3. By comparing Figure 10 and Figure 11 , it can be known that after the PTFE-based coating in Example 5 is modified with the coupling agent graphene, the tissue morphology in the coating becomes denser. It can be seen from this that adding the coupling agent can reduce the micropores and cracks of the PTFE matrix itself, thereby improving its corrosion resistance.

[0211] Figure 12 The polarization curves of the composite plates prepared in Example 5, Example 8, Example 9 and Comparative Example 3 after being immersed in a 4% NaCl solution for 48 hours. As can be seen from Figure 12 the comparison between Example 5, Example 8, Example 9 and Comparative Example 3, it can be known that the corrosion potentials of Example 5, Example 8 and Example 9 shift towards more negative potentials, and the corrosion current density decreases significantly. Moreover, the closer the corrosion potential is to the negative potential and the lower the corrosion current density, the better its corrosion resistance. It can be seen that adding a coupling agent to the preparation of the PTFE-based coating can improve its corrosion resistance. Among them, Example 5 has the best corrosion resistance, and Comparative Example 3 has the worst corrosion resistance. Through the above experiments, it is confirmed that graphene modified by a coupling agent has an enhancing effect on the corrosion resistance protection performance of the PTFE-based coating.

[0212] The basic principle, main features and advantages of the present invention have been described above. Those skilled in the art should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification is only the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection required by the present invention is defined by the appended claims and their equivalents.

Claims

1. A modified graphene PTFE-based composite sheet, characterized in that, The raw materials of the modified graphene PTFE-based coating are as follows by weight: 40 - 80 parts of PTFE powder, 1 - 10 parts of coupling agent, 5 - 15 parts of aramid, 0.5 - 8 parts of graphene, 70 - 90 parts of copper nitrate trihydrate, and 15 - 25 parts of polyimide; The copper nitrate trihydrate is used to prepare copper-coated graphene powder by mixing with the graphene, and the coupling agent is used to modify the copper-coated graphene powder to obtain modified graphene powder; Among them, the coupling agent is one or more of heptadecafluorodecyltriethoxysilane, γ-aminopropyltriethoxysilane, and tridecafluorooctyltriethoxysilane; The preparation method of the modified graphene PTFE-based composite plate includes the following steps: Prepare copper-coated graphene powder; Add the coupling agent into anhydrous ethanol, stir to dissolve it to obtain a first mixed solution, then add the prepared copper-coated graphene powder into the first mixed solution, and perform ultrasonic treatment and stirring on it to obtain a second mixed solution; then adjust the pH of the second mixed solution with hydrochloric acid so that the pH of the second mixed solution is 4 - 5; then heat the second mixed solution in a water bath and cool it to room temperature, wash and filter it with deionized water, and obtain the modified graphene powder after vacuum drying; Add the modified graphene powder into the PTFE dispersion liquid, and perform stirring, filtering, and drying in sequence to obtain the modified graphene PTFE composite powder; Add aramid and polyimide into the modified graphene PTFE composite powder respectively, and mix evenly to obtain a mixed mud; Spread the mixed mud evenly on a copper powder plate, and roll it with a rolling mill to obtain a plate with the mixed mud coated on the surface; Then put the plate with the mixed mud coated on the surface into a sintering device for plasticization, the plasticization temperature is 370 °C, the plasticization time is 4 h, the heating rate is 10 °C / min, and after sintering is completed, it is cooled to room temperature with the sintering device, and the modified graphene PTFE-based composite plate is obtained; 2. The modified graphene PTFE-based composite sheet according to claim 1, wherein The particle size of the graphene is 2 μm - 7 μm.

3. The modified graphene PTFE-based composite sheet according to claim 1, wherein, The copper-coated graphene powder is prepared by an in-situ generation method.

4. The modified graphene PTFE-based composite sheet according to claim 1, wherein, The preparation of the copper-coated graphene powder includes the following steps: Disperse the graphene in 600 mL of ethanol solution, perform ultrasonic treatment and then magnetic stirring to obtain a third mixed solution; Add copper nitrate trihydrate and glucose solution into the third mixed solution in sequence, and stir for a period of time to obtain a fourth mixed solution; Drop a 5 mol / L, 500 mL NaOH solution into the fourth mixed solution in three times. After the dropping is completed, stir for 3 hours, then filter the stirred solution to obtain a solid product; wash the solid product with deionized water for multiple times and filter it by suction and dry it to obtain the copper-coated graphene powder.

5. The modified graphene PTFE-based composite sheet according to claim 1, wherein, The PTFE dispersion liquid is obtained by adding PTFE powder into distilled water, performing mechanical stirring and ultrasonic dispersion for 2 h.

6. The modified graphene PTFE-based composite sheet according to claim 1, characterized in that The second mixed solution with the pH adjusted reacts in a water bath at 50 °C for 30 min, then the temperature is raised to 70 °C and reacts for 30 min, and finally it is cooled to room temperature.

7. The modified graphene PTFE-based composite sheet according to claim 6, wherein, The second mixed solution cooled to room temperature is washed and filtered 3 times with deionized water, and vacuum dried at 60 °C, and the modified graphene powder is obtained after drying.

8. The modified graphene PTFE-based composite sheet according to claim 6, characterized in that, After adding the prepared modified graphene powder to the PTFE dispersion, it is mechanically stirred for 1 h, then vacuum filtered, and finally dried at 100 °C for 9 h to obtain the modified graphene PTFE composite powder.

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