Preparation method and application of oriented graphene oxide polyurethane composite coating

Abstract

The invention discloses a preparation method and application of a directional graphene oxide polyurethane composite coating. The preparation method comprises the following steps: drying nano ferroferric oxide, preparing a silane coupling agent solution, silanizing graphene oxide, preparing ferroferric oxide grafted graphene oxide and preparing the graphene oxide polyurethane composite coating. The invention provides a simple and convenient preparation technology of a polyurethane composite coating with directionally distributed graphene, and the composite coating prepared by the technology can improve the wear resistance of a wind power blade protective coating so as to resist the scouring of wind sand and rainwater; the waterborne polyurethane disclosed by the invention accords with the concept of sustainable development; compared with the traditional solvent type polyurethane, the waterborne polyurethane taking water as a dispersion medium has the advantage that the emission of organic compounds (VOC) is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of material surface modification, and specifically relates to a preparation method of a directional graphene oxide polyurethane composite coating and application thereof. Background Art

[0002] Waterborne polyurethane (WPU) has great application potential in the field of engineering coatings due to its excellent mechanical properties, corrosion resistance and environmental protection. However, under harsh conditions, it is difficult for waterborne polyurethane alone to meet the requirements of friction reduction and wear resistance; once sliding friction occurs at high frequency, the wear resistance of pure waterborne polyurethane coating will drop sharply. This is due to the presence of strong polar groups in polyurethane molecules, such as urea, carbamate, amide and other groups with high surface energy. These molecules will accumulate heat under cyclic alternating stress, further destroying the cross-linking structure of waterborne polyurethane and causing higher wear during friction.

[0003] Nanofillers can significantly improve the optical, thermal and magnetic properties of organic coatings. As a new type of two-dimensional nanomaterial, graphene oxide has high strength, high modulus, high specific surface area, significant flexibility, high thermal stability, high thermal conductivity and high electrical conductivity; however, in practical applications, due to the dispersion and orientation problems of graphene oxide, it is difficult for the composite coating performance to reach the ideal expectations; therefore, improving the performance of composite coatings has become an urgent problem to be solved. Summary of the invention

[0004] The purpose of this section is to summarize some aspects of embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the specification abstract and the invention title of this application to avoid blurring the purpose of this section, the specification abstract and the invention title, and such simplifications or omissions cannot be used to limit the scope of the present invention.

[0005] In view of the above problems and / or the problems existing in the prior art, the present invention is proposed.

[0006] Therefore, the purpose of the present invention is to overcome the deficiencies in the prior art and provide a method for preparing a oriented graphene oxide polyurethane composite coating.

[0007] In order to solve the above technical problems, the present invention provides the following technical solutions: a method for preparing a directional graphene oxide polyurethane composite coating is provided, comprising:

[0008] Drying the nano-ferroferric oxide and preparing a silane coupling agent solution;

[0009] Silylated graphene oxide: Add the dried nano-iron tetroxide to the prepared silane coupling agent solution, dissolve in anhydrous ethanol, perform ultrasonic treatment, mechanically stir and reflux, centrifuge and discard the supernatant, vacuum dry and grind to obtain surface silanized iron tetroxide powder;

[0010] Preparation of graphene oxide grafted with ferroferric oxide: dispersing surface silanized ferroferric oxide powder in N,N-dimethylformamide, adding graphene oxide, ultrasonically treating, mechanically stirring and refluxing, centrifuging and discarding the supernatant, vacuum drying and grinding to obtain modified graphene oxide powder;

[0011] Preparation of graphene oxide polyurethane composite coating: Graphene oxide grafted with ferroferric oxide is ultrasonically uniformly dispersed in deionized water, the dispersion is uniformly mixed with aqueous polyurethane, grease and impurities on the surface of the sample are removed, the slurry is coated on the surface of the metal substrate, and the graphene oxide polyurethane composite coating is obtained after curing and drying.

[0012] As a preferred embodiment of the preparation method of the present invention, the nano-ferroferric oxide is dried in a vacuum drying oven for 24 to 30 hours at a temperature of 80 to 100°C.

[0013] As a preferred embodiment of the preparation method of the present invention, the silane coupling agent solution is prepared from silane coupling agent KH-550, anhydrous ethanol and deionized water, and the mass percentage of the solution is 10-40wt.% of silane coupling agent KH-550, 60-80wt.% of anhydrous ethanol and 5-10wt.% of deionized water.

[0014] As a preferred solution of the preparation method of the present invention, the mass ratio of the nano-ferroferric oxide to the silane coupling agent is 1:20-1000.

[0015] As a preferred embodiment of the preparation method of the present invention, the particle size of the nano-iron tetroxide after drying is 10 to 80 nm.

[0016] As a preferred embodiment of the preparation method of the present invention, the mass ratio of ferrosoferric oxide to N,N-dimethylformamide is 1:50-150, and the mass ratio of ferrosoferric oxide to graphene oxide is 1:1-7.

[0017] As a preferred embodiment of the preparation method described in the present invention, in the preparation of the graphene oxide polyurethane composite coating, the sample is placed in a magnetic field for directional curing for 2 to 8 hours, and then placed in a vacuum tube furnace for high-temperature curing to obtain the graphene polyurethane composite coating.

[0018] As a preferred embodiment of the preparation method of the present invention, the high temperature curing includes curing at 50°C in a vacuum tube furnace until moisture disappears, then increasing the temperature to 70°C until complete curing, and cooling at room temperature.

[0019] As a preferred embodiment of the preparation method of the present invention, the intensity of the magnetic field is 0.1-0.5T.

[0020] Another object of the present invention is to overcome the deficiencies in the prior art and provide a directional graphene oxide polyurethane composite coating.

[0021] Another object of the present invention is to overcome the deficiencies in the prior art and provide an application of graphene oxide polyurethane composite coating in wind turbine blade protection and mechanical sliding surface protection.

[0022] As a preferred solution of the application of the present invention, the graphene oxide is first ultrasonically dispersed in deionized water, and then the dispersion is physically mixed with polyurethane until it is evenly dispersed.

[0023] Beneficial effects of the present invention:

[0024] 1. The present invention provides a simple preparation technology for a polyurethane composite coating with directional distribution of graphene. The composite coating prepared by this technology can improve the wear resistance of wind turbine blades and mechanical sliding surface protective coatings to resist erosion by wind, sand and rain.

[0025] 2. The present invention complies with the concept of sustainable development. Compared with traditional solvent-based polyurethane, water-based polyurethane reduces the emission of organic compounds (VOC).

[0026] 3. The wear rate of the composite coating prepared by the present invention can reach 1.61×10 -5 mm 3 / (N·m). BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative labor. Among them:

[0028] Figure 1 This is a schematic diagram of the preparation process of the nanofiller in Example 1 of the present invention;

[0029] Figure 2 The microscopic morphology of the nanofiller in Example 1 of the present invention;

[0030] Figure 3This is the infrared spectrum of the nanofiller in Example 1 of the present invention;

[0031] Figure 4 This is the X-ray diffraction pattern in Example 1 of the present invention:

[0032] Figure 5 This is the spectrum diagram of the nanofiller in Example 1 of the present invention.

[0033] Figure 6 This is the cross-sectional microscopic morphology of the oriented graphene oxide polyurethane composite coating in Example 1 of the present invention.

[0034] Figures 7 to 9 They are Figure 6 Partial image of the cross-sectional microstructure of the oriented graphene oxide polyurethane composite coating marked in the figure. DETAILED DESCRIPTION

[0035] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the embodiments of the specification.

[0036] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0037] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0038] Raw materials and reagents used in the present invention:

[0039] The sample matrix is ​​S304 stainless steel (Hubang Metal Products Processing), with a size of φ30mm×3mm; graphene oxide (GO, Suzhou Carbonfeng Graphene Technology Co., Ltd.), with a flake diameter of 0.5-5μm; nano-iron tetroxide (Fe3O4, Shanghai Myrel Biochemical Technology Co., Ltd.), with a size of 20nm; carbon fiber (CF, Toray Industries, Ltd.), with a size of 7μm; N,N-dimethylformamide (Sinopharm Chemical Reagent Co., Ltd.), silane coupling agent KH-550 (Sinopharm Chemical Reagent Co., Ltd.), and anhydrous ethanol (Sinopharm Chemical Reagent Co., Ltd.).

[0040] Example 1

[0041] Drying of nano-ferroferric oxide: Dry the nano-ferroferric oxide in a vacuum drying oven for 24 hours at a temperature of 80°C;

[0042] Prepare a silane coupling agent solution: 10 g of silane coupling agent KH-550, 36 g of anhydrous ethanol and 4 g of deionized water are mixed to obtain a silane coupling agent solution;

[0043] Silylated graphene oxide: 0.5 g of nano-iron tetroxide (20 nm) was added to 50 g of the prepared silane coupling agent KH-550 solution, and then the mixed solution was dissolved in 151.5 g of anhydrous ethanol, and ultrasonic treatment was performed for 30 min to obtain a uniformly dispersed suspension; the mixed solution was transferred into a three-necked flask and heated in a water bath, and mechanically stirred and refluxed at 78°C for 4 h; after the reaction was completed, centrifuged while hot, the supernatant was removed, deionized water and anhydrous ethanol were added for shaking and washing, centrifuged, and the operation was repeated 3 times, and finally vacuum dried at 70°C for 24 h, and fully ground in a mortar to obtain surface silanized iron tetroxide powder;

[0044] Preparation of modified graphene oxide powder: Disperse 0.15g of nano-ferroferric oxide in 150ml N,N-dimethylformamide (DMF); then add 0.6g of graphene oxide and ultrasonicate for 30 minutes to obtain a uniformly dispersed mixed solution. Transfer the mixed solution into a three-necked flask, heat it in an oil bath at 105°C, and reflux it with mechanical stirring for 5 hours; after the reaction is completed, centrifuge it while hot, remove the supernatant, add deionized water and anhydrous ethanol to shake and wash, centrifuge it, repeat the operation 3 times, and finally vacuum dry it at 70°C for 24 hours, and grind it thoroughly in a mortar to obtain modified graphene oxide powder. The schematic diagram of the preparation process of GO@Fe3O4 nanofiller is shown in the figure. Figure 1 shown.

[0045] The microstructures of GO and GO@Fe3O4 nanofillers were observed by SEM. Figure 2 As shown in the figure, nano-iron tetroxide was successfully grafted onto the GO surface, while the two-dimensional wrinkled structure of graphene oxide was not changed. The prepared nanofillers were characterized by FTIR, XRD and Raman. Figure 2 It can be seen that the spectrum of nano-iron tetroxide is at 549.34cm -1 There is an absorption peak at 548.9cm, which corresponds to the stretching vibration of Fe-O in nano-iron tetroxide. -1 The absorption peak at 991.06 cm indicates the presence of Fe3O4. -1 and 1630.12cm -1The absorption peaks at 559.59cm correspond to the antisymmetric stretching vibration and bending vibration of Si-O-Si and the bending vibration of -NH2. This indicates that the nano-iron tetroxide has been modified by silane molecules. In the infrared spectrum of GO@Fe3O4, 559.59cm -1 The absorption peak at 1644.47cm corresponds to the stretching vibration of Fe-O in nano-iron tetroxide; -1 、1720.04cm -1 The peaks at 1050.65cm correspond to the C=C and C=O bonds in GO, which are the characteristic peaks of GO. Therefore, it shows that nano-iron tetroxide is successfully grafted onto the GO surface. -1 、1225.15cm -1 、1619.07cm -1 、1719.32cm -1 、3307.52cm -1 The corresponding positions are COC, C-OH, -OH, C=O, and -OH bonds in GO, respectively, indicating the presence of hydroxyl, carboxyl, and epoxy groups on the surface of GO.

[0046] Figure 3 The XRD characterization results of GO, Fe3O4, and GO@Fe3O4 are shown below. Figure 3 As shown in the figure, the XRD pattern of GO shows a diffraction peak at 2θ=10.95°, which corresponds to the main characteristic peak of GO (001). Obviously, the intensity of the characteristic peak of GO is significantly weakened in GO@Fe3O4, and there are still a large number of diffraction peaks on the (200), (311), (400), (422), (511) and (440) crystal planes, which is consistent with the diffraction peaks on the crystal plane of the Fe3O4 structure, indicating that nano-iron tetroxide is successfully loaded on the GO surface. The Raman spectra of GO and GO@Fe3O4 are shown in Figure 1. Figure 4 As shown. The Raman spectrum of GO is at 1329 cm -1 and 1899cm -1 The D peak and G peak appeared. Compared with GO, the I D / I G The increase from 2.16 to 2.88 indicates that there are more lattice defects in graphene oxide. This is because in the process of functionalizing graphene oxide, the oxygen-containing groups such as -OH and -COOH on the GO surface disappear, which increases the surface defects, and the interaction between nano-iron tetroxide and graphene oxide during the functionalization process leads to an increase in the interlayer spacing.

[0047] Preparation of oriented graphene oxide polyurethane composite coating: 0.05 g of modified graphene oxide powder was uniformly dispersed in 2 ml of deionized water by ultrasonication, and then the dispersion was physically mixed with 10 g of waterborne polyurethane and ultrasonically stirred until uniformly dispersed;

[0048] Use sandpaper to polish the surface of the 304 stainless steel substrate, and clean it with anhydrous ethanol to remove grease and debris on the surface of the sample, ensuring that the surface cleanliness of the substrate reaches Sa3 level for standby use;

[0049] The slurry was coated on the surface of the metal substrate by scraping, placed in a 0.2T magnetic field for curing for 2 hours, and dried to obtain a sample;

[0050] The sample was placed in a vacuum tube furnace and cured at 50°C for 6 hours until the moisture disappeared, then the temperature was raised to 70°C and cured for 24 hours until it was completely cured, and then cooled at room temperature. The oriented graphene oxide polyurethane composite coating was obtained. The nanofiller content was 0.5wt.%. The coating thickness after curing was about 0.3 mm.

[0051] The cross section of the oriented composite polyurethane coating was characterized by SEM, such as Figure 6-9 As shown, the flake-like GO was successfully aligned parallel to the metal matrix in the polyurethane matrix.

[0052] Example 2

[0053] Drying of nano-ferroferric oxide: Dry the nano-ferroferric oxide in a vacuum drying oven for 24 hours at a temperature of 80°C;

[0054] Prepare a silane coupling agent solution: 10 g of silane coupling agent KH-550, 36 g of anhydrous ethanol and 4 g of deionized water are mixed to obtain a silane coupling agent solution;

[0055] Silylated graphene oxide: 0.5 g of nano-iron tetroxide (20 nm) was added to 50 g of the prepared silane coupling agent KH-550 solution, and then the mixed solution was dissolved in 151.5 g of anhydrous ethanol, and ultrasonic treatment was performed for 30 min to obtain a uniformly dispersed suspension; the mixed solution was transferred into a three-necked flask and heated in a water bath, and mechanically stirred and refluxed at 78°C for 4 h; after the reaction was completed, centrifuged while hot, the supernatant was removed, deionized water and anhydrous ethanol were added for shaking and washing, centrifuged, and the operation was repeated 3 times, and finally vacuum dried at 70°C for 24 h, and fully ground in a mortar to obtain surface silanized iron tetroxide powder;

[0056] Preparation of modified graphene oxide powder: Disperse 0.15g of nano-iron tetroxide in 150ml N,N-dimethylformamide (DMF); then add 0.6g of graphene oxide and ultrasonicate for 30min to obtain a uniformly dispersed mixed solution. Transfer the mixed solution into a three-necked flask, heat it in an oil bath at 105℃, stir it mechanically and reflux it for 5h; after the reaction is completed, centrifuge it while hot, remove the supernatant, add deionized water and anhydrous ethanol to shake and wash, centrifuge it, repeat the operation 3 times, and finally vacuum dry it at 70℃ for 24h, and grind it fully in a mortar to obtain modified graphene oxide powder;

[0057] Preparation of oriented graphene oxide polyurethane composite coating: 0.02 g of modified graphene oxide powder was uniformly dispersed in 2 ml of deionized water by ultrasonication, and then the dispersion was physically mixed with 10 g of waterborne polyurethane and ultrasonically stirred until uniformly dispersed;

[0058] Use sandpaper to polish the surface of the 304 stainless steel substrate, and clean it with anhydrous ethanol to remove grease and debris on the surface of the sample, ensuring that the surface cleanliness of the substrate reaches Sa3 level for standby use;

[0059] The slurry was coated on the surface of the metal substrate by scraping, placed in a 0.1T magnetic field for curing for 2 hours, and dried to obtain a sample;

[0060] The sample was placed in a vacuum tube furnace and cured at 50°C for 6 hours until the moisture disappeared, then the temperature was raised to 70°C and cured for 24 hours until it was completely cured, and then cooled at room temperature. The oriented graphene oxide polyurethane composite coating was obtained. The nanofiller content was 0.2wt.%. The coating thickness after curing was about 0.3 mm.

[0061] Example 3

[0062] Drying of nano-ferroferric oxide: Dry the nano-ferroferric oxide in a vacuum drying oven for 24 hours at a temperature of 80°C;

[0063] Prepare a silane coupling agent solution: 10 g of silane coupling agent KH-550, 36 g of anhydrous ethanol and 4 g of deionized water are mixed to obtain a silane coupling agent solution;

[0064] Silylated graphene oxide: 0.5 g of nano-iron tetroxide (20 nm) was added to 50 g of the prepared silane coupling agent KH-550 solution, and then the mixed solution was dissolved in 151.5 g of anhydrous ethanol, and ultrasonic treatment was performed for 30 min to obtain a uniformly dispersed suspension; the mixed solution was transferred into a three-necked flask and heated in a water bath, and mechanically stirred and refluxed at 78°C for 4 h; after the reaction was completed, centrifuged while hot, the supernatant was removed, deionized water and anhydrous ethanol were added for shaking and washing, centrifuged, and the operation was repeated 3 times, and finally vacuum dried at 70°C for 24 h, and fully ground in a mortar to obtain surface silanized iron tetroxide powder;

[0065] Preparation of modified graphene oxide powder: Disperse 0.15g of nano-iron tetroxide in 150ml N,N-dimethylformamide (DMF); then add 0.6g of graphene oxide and ultrasonicate for 30min to obtain a uniformly dispersed mixed solution. Transfer the mixed solution into a three-necked flask, heat it in an oil bath at 105℃, stir it mechanically and reflux it for 5h; after the reaction is completed, centrifuge it while hot, remove the supernatant, add deionized water and anhydrous ethanol to shake and wash, centrifuge it, repeat the operation 3 times, and finally vacuum dry it at 70℃ for 24h, and grind it fully in a mortar to obtain modified graphene oxide powder;

[0066] Preparation of oriented graphene oxide polyurethane composite coating: 0.1 g of modified graphene oxide powder was uniformly dispersed in 2 ml of deionized water by ultrasonication, and then the dispersion was physically mixed with 10 g of waterborne polyurethane and ultrasonically stirred until uniformly dispersed;

[0067] Use sandpaper to polish the surface of the 304 stainless steel substrate, and clean it with anhydrous ethanol to remove grease and debris on the surface of the sample, ensuring that the surface cleanliness of the substrate reaches Sa3 level for standby use;

[0068] The slurry was coated on the surface of the metal substrate by scraping, placed in a 0.3T magnetic field for curing for 2 h, and dried to obtain a sample;

[0069] The sample was placed in a vacuum tube furnace and cured at 50°C for 6 hours until the moisture disappeared, then the temperature was raised to 70°C and cured for 24 hours until it was completely cured, and then cooled at room temperature. The oriented graphene oxide polyurethane composite coating was obtained. The nanofiller content was 1.0wt.%. The coating thickness after curing was about 0.3 mm.

[0070] Example 4

[0071] Drying of nano-ferroferric oxide: Dry the nano-ferroferric oxide in a vacuum drying oven for 24 hours at a temperature of 80°C;

[0072] Prepare a silane coupling agent solution: 10 g of silane coupling agent KH-550, 36 g of anhydrous ethanol and 4 g of deionized water are mixed to obtain a silane coupling agent solution;

[0073] Silylated graphene oxide: 0.5 g of nano-iron tetroxide (20 nm) was added to 50 g of the prepared silane coupling agent KH-550 solution, and then the mixed solution was dissolved in 151.5 g of anhydrous ethanol, and ultrasonic treatment was performed for 30 min to obtain a uniformly dispersed suspension; the mixed solution was transferred into a three-necked flask and heated in a water bath, and mechanically stirred and refluxed at 78°C for 4 h; after the reaction was completed, centrifuged while hot, the supernatant was removed, deionized water and anhydrous ethanol were added for shaking and washing, centrifuged, and the operation was repeated 3 times, and finally vacuum dried at 70°C for 24 h, and fully ground in a mortar to obtain surface silanized iron tetroxide powder;

[0074] Preparation of modified graphene oxide powder: Disperse 0.15g of nano-iron tetroxide in 150ml N,N-dimethylformamide (DMF); then add 0.6g of graphene oxide and ultrasonicate for 30min to obtain a uniformly dispersed mixed solution. Transfer the mixed solution into a three-necked flask, heat it in an oil bath at 105℃, stir it mechanically and reflux it for 5h; after the reaction is completed, centrifuge it while hot, remove the supernatant, add deionized water and anhydrous ethanol to shake and wash, centrifuge it, repeat the operation 3 times, and finally vacuum dry it at 70℃ for 24h, and grind it fully in a mortar to obtain modified graphene oxide powder;

[0075] Preparation of oriented graphene oxide polyurethane composite coating: 0.15 g of modified graphene oxide powder was uniformly dispersed in 2 ml of deionized water by ultrasonication, and then the dispersion was physically mixed with 10 g of waterborne polyurethane and ultrasonically stirred until uniformly dispersed;

[0076] Use sandpaper to polish the surface of the 304 stainless steel substrate, and clean it with anhydrous ethanol to remove grease and debris on the surface of the sample, ensuring that the surface cleanliness of the substrate reaches Sa3 level for standby use;

[0077] The slurry was coated on the surface of the metal substrate by scraping, placed in a 0.4T magnetic field for curing for 2 hours, and dried to obtain a sample;

[0078] The sample was placed in a vacuum tube furnace and cured at 50°C for 6 hours until the moisture disappeared, then the temperature was raised to 70°C and cured for 24 hours until it was completely cured, and then cooled at room temperature. The oriented graphene oxide polyurethane composite coating was obtained. The nanofiller content was 1.5wt.%. The coating thickness after curing was about 0.3 mm.

[0079] Comparative Example 1

[0080] Use sandpaper to polish the surface of the 304 stainless steel substrate, and clean it with anhydrous ethanol to remove grease and debris on the surface of the sample, ensuring that the surface cleanliness of the substrate reaches Sa3 level for standby use;

[0081] Pure waterborne polyurethane is applied to the surface of the substrate by scraping, and the sample is obtained after drying.

[0082] The sample was placed in a vacuum tube furnace and cured at 50°C for 6 hours until the water disappeared, then the temperature was raised to 70°C and cured for 24 hours until it was completely cured, and then cooled at room temperature. A pure waterborne polyurethane coating was obtained. The nanofiller content was 0wt.%. The coating thickness after curing was about 0.3 mm.

[0083] Comparative Example 2:

[0084] Drying of nano-ferroferric oxide: Dry the nano-ferroferric oxide in a vacuum drying oven for 24 hours at a temperature of 80°C;

[0085] Prepare a silane coupling agent solution: 10 g of silane coupling agent KH-550, 36 g of anhydrous ethanol and 4 g of deionized water are mixed to obtain a silane coupling agent solution;

[0086] Silylated graphene oxide: 0.5 g of nano-iron tetroxide (20 nm) was added to 50 g of the prepared silane coupling agent KH-550 solution, and then the mixed solution was dissolved in 151.5 g of anhydrous ethanol, and ultrasonic treatment was performed for 30 min to obtain a uniformly dispersed suspension; the mixed solution was transferred into a three-necked flask and heated in a water bath, and mechanically stirred and refluxed at 78°C for 4 h; after the reaction was completed, centrifuged while hot, the supernatant was removed, deionized water and anhydrous ethanol were added for shaking and washing, centrifuged, and the operation was repeated 3 times, and finally vacuum dried at 70°C for 24 h, and fully ground in a mortar to obtain surface silanized iron tetroxide powder;

[0087] Preparation of modified graphene oxide powder: Disperse 0.15g of nano-iron tetroxide in 150ml N,N-dimethylformamide (DMF); then add 0.6g of graphene oxide and ultrasonicate for 30min to obtain a uniformly dispersed mixed solution. Transfer the mixed solution into a three-necked flask, heat it in an oil bath at 105℃, stir it mechanically and reflux it for 5h; after the reaction is completed, centrifuge it while hot, remove the supernatant, add deionized water and anhydrous ethanol to shake and wash, centrifuge it, repeat the operation 3 times, and finally vacuum dry it at 70℃ for 24h, and grind it fully in a mortar to obtain modified graphene oxide powder;

[0088] Preparation of oriented graphene oxide polyurethane composite coating: 0.05 g of modified graphene oxide powder was uniformly dispersed in 2 ml of deionized water by ultrasonication, and then the dispersion was physically mixed with 10 g of waterborne polyurethane and ultrasonically stirred until uniformly dispersed;

[0089] Use sandpaper to polish the surface of the 304 stainless steel substrate, and clean it with anhydrous ethanol to remove grease and debris on the surface of the sample, ensuring that the surface cleanliness of the substrate reaches Sa3 level for standby use;

[0090] The slurry is coated on the surface of the metal substrate by scraping, and the sample is obtained after drying;

[0091] The sample was placed in a vacuum tube furnace and cured at 50°C for 6 hours until the moisture disappeared, then the temperature was raised to 70°C and cured for 24 hours until it was completely cured, and then cooled at room temperature. The non-oriented graphene oxide polyurethane composite coating was obtained. The nanofiller content was 0.5wt.%. The coating thickness after curing was about 0.3 mm.

[0092] Comparative Example 3:

[0093] Drying of nano-ferroferric oxide: Dry the nano-ferroferric oxide in a vacuum drying oven for 24 hours at a temperature of 80°C;

[0094] Prepare a silane coupling agent solution: 10 g of silane coupling agent KH-550, 36 g of anhydrous ethanol and 4 g of deionized water are mixed to obtain a silane coupling agent solution;

[0095] Silylated graphene oxide: 0.5 g of nano-iron tetroxide (20 nm) was added to 50 g of the prepared silane coupling agent KH-550 solution, and then the mixed solution was dissolved in 151.5 g of anhydrous ethanol, and ultrasonic treatment was performed for 30 min to obtain a uniformly dispersed suspension; the mixed solution was transferred into a three-necked flask and heated in a water bath, and mechanically stirred and refluxed at 78°C for 4 h; after the reaction was completed, centrifuged while hot, the supernatant was removed, deionized water and anhydrous ethanol were added for shaking and washing, centrifuged, and the operation was repeated 3 times, and finally vacuum dried at 70°C for 24 h, and fully ground in a mortar to obtain surface silanized iron tetroxide powder;

[0096] Preparation of modified graphene oxide powder: Disperse 0.15g of nano-iron tetroxide in 150ml N,N-dimethylformamide (DMF); then add 0.6g of graphene oxide and ultrasonicate for 30min to obtain a uniformly dispersed mixed solution. Transfer the mixed solution into a three-necked flask, heat it in an oil bath at 105℃, stir it mechanically and reflux it for 5h; after the reaction is completed, centrifuge it while hot, remove the supernatant, add deionized water and anhydrous ethanol to shake and wash, centrifuge it, repeat the operation 3 times, and finally vacuum dry it at 70℃ for 24h, and grind it fully in a mortar to obtain modified graphene oxide powder;

[0097] Preparation of oriented graphene oxide polyurethane composite coating: 0.05 g of modified graphene oxide powder was uniformly dispersed in 2 ml of deionized water by ultrasonication, and then the dispersion was physically mixed with 10 g of waterborne polyurethane and ultrasonically stirred until uniformly dispersed;

[0098] Use sandpaper to polish the surface of the 304 stainless steel substrate, and clean it with anhydrous ethanol to remove grease and debris on the surface of the sample, ensuring that the surface cleanliness of the substrate reaches Sa3 level for standby use;

[0099] The slurry was coated on the surface of the metal substrate by scraping, placed in a 1.0T magnetic field for curing for 2 h, and dried to obtain a sample;

[0100] The sample was placed in a vacuum tube furnace and cured at 50°C for 6 hours until the moisture disappeared, then the temperature was raised to 70°C and cured for 24 hours until it was completely cured, and then cooled at room temperature. The oriented graphene oxide polyurethane composite coating was obtained. The nanofiller content was 0.5wt.%. The coating thickness after curing was about 0.3 mm.

[0101] Comparative Example 4

[0102] Drying of nano-ferroferric oxide: Dry the nano-ferroferric oxide in a vacuum drying oven for 24 hours at a temperature of 80°C;

[0103] Prepare a silane coupling agent solution: 10 g of silane coupling agent KH-550, 36 g of anhydrous ethanol and 4 g of deionized water are mixed to obtain a silane coupling agent solution;

[0104] Silylated graphene oxide: 0.5 g of nano-iron tetroxide (20 nm) was added to 50 g of the prepared silane coupling agent KH-550 solution, and then the mixed solution was dissolved in 151.5 g of anhydrous ethanol, and ultrasonic treatment was performed for 30 min to obtain a uniformly dispersed suspension; the mixed solution was transferred into a three-necked flask and heated in a water bath, and mechanically stirred and refluxed at 78°C for 4 h; after the reaction was completed, centrifuged while hot, the supernatant was removed, deionized water and anhydrous ethanol were added for shaking and washing, centrifuged, and the operation was repeated 3 times, and finally vacuum dried at 70°C for 24 h, and fully ground in a mortar to obtain surface silanized iron tetroxide powder;

[0105] Preparation of modified graphene oxide powder: Disperse 0.15g of nano-iron tetroxide in 150ml N,N-dimethylformamide (DMF); then add 0.6g of graphene oxide and ultrasonicate for 30min to obtain a uniformly dispersed mixed solution. Transfer the mixed solution into a three-necked flask, heat it in an oil bath at 105℃, stir it mechanically and reflux it for 5h; after the reaction is completed, centrifuge it while hot, remove the supernatant, add deionized water and anhydrous ethanol to shake and wash, centrifuge it, repeat the operation 3 times, and finally vacuum dry it at 70℃ for 24h, and grind it fully in a mortar to obtain modified graphene oxide powder;

[0106] Preparation of oriented carbon fiber polyurethane composite coating: 0.05 g of modified graphene oxide powder was uniformly dispersed in 2 ml of deionized water by ultrasonication, and then the dispersion was physically mixed with 10 g of waterborne polyurethane and ultrasonically stirred until uniformly dispersed;

[0107] Use sandpaper to polish the surface of the 304 stainless steel substrate, and clean it with anhydrous ethanol to remove grease and debris on the surface of the sample, ensuring that the surface cleanliness of the substrate reaches Sa3 level for standby use;

[0108] The slurry was coated on the surface of the metal substrate by scraping, placed in a 0.2T magnetic field for curing for 2 hours, and dried to obtain a sample;

[0109] The sample was placed in a vacuum tube furnace and cured at 50°C for 6 hours until the water disappeared, then the temperature was raised to 70°C and cured for 24 hours until it was completely cured, and then cooled at room temperature. The oriented graphene oxide urethane composite coating was obtained. The nanofiller content was 0.5wt.%. The coating thickness after curing was about 0.3 mm.

[0110] The wear rates of the coatings prepared in the above embodiments and comparative examples were tested, and the results are shown in Table 1 below.

[0111] Table 1

[0112]

[0113]

[0114] As can be seen from Table 1, the wear rate of the coating can be greatly reduced by inducing the directional arrangement of graphene oxide in the polyurethane coating through the magnetic field, which indicates that the present invention has successfully prepared a polyurethane composite coating with enhanced wear resistance by directional arrangement of graphene oxide induced by the magnetic field.

[0115] The present invention performs an amination treatment on ferroferric oxide by configuring a KH-550 solution to hydrolyze KH-550. Ferroferric oxide is an inorganic material with fewer hydroxyl functional groups on the surface, which is difficult to effectively combine with graphene oxide. Therefore, ferroferric oxide is firstly subjected to a silanization treatment to introduce amino groups into the surface of ferroferric oxide. Graphene oxide reacts with ferroferric oxide with amino groups on the surface in DMF to obtain ferroferric oxide-modified graphene oxide. The wear rate of the oriented graphene polyurethane composite coating with a mass fraction of 0.5wt.% is only 0.2% of that of the pure water-based polyurethane coating, and the coating wear marks are very shallow.

[0116] In addition, the wear rates of the oriented / non-oriented coatings with the same mass fraction of 0.5wt.% also have obvious differences. The wear rate of the oriented coating is only 17.4% of that of the non-oriented coating, which is greatly reduced. The uniform dispersion of graphene oxide @ ferroferric oxide filler can hinder the propagation of cracks caused by friction in the coating, thereby inhibiting the peeling of the coating and reducing the wear rate. Compared with the non-oriented graphene oxide polyurethane composite coating, the oriented graphene oxide polyurethane composite coating can further extend the path of crack propagation and achieve better friction reduction and wear resistance.

[0117] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for preparing a directional graphene oxide polyurethane composite coating, characterized in that: include, The dried nano-iron tetroxide is added to the silane coupling agent solution, and the obtained mixed solution is dissolved in anhydrous ethanol, subjected to ultrasonic treatment, mechanically stirred and refluxed, centrifuged and the supernatant is discarded, vacuum dried and ground to obtain surface silanized iron tetroxide powder; Surface silanized ferrosoferric oxide powder is dispersed in N,N-dimethylformamide, graphene oxide is added, and after ultrasonic treatment, mechanical stirring and reflux are performed, the supernatant is discarded by centrifugation, vacuum drying and grinding are performed to obtain modified graphene oxide powder; The modified graphene oxide powder is ultrasonically uniformly dispersed in deionized water to obtain a dispersion liquid which is evenly mixed with waterborne polyurethane to obtain a mixed slurry. The mixed slurry is coated on the surface of a substrate, placed in a magnetic field for directional solidification, and then cured at high temperature. After drying, a graphene oxide polyurethane composite coating is formed on the surface of the metal substrate.

2. The preparation method according to claim 1, characterized in that: The drying time of the nano-ferroferric oxide is 24 to 30 hours, and the drying temperature is 80 to 100°C.

3. The preparation method according to claim 1 or 2, characterized in that: The silane coupling agent solution is prepared from silane coupling agent KH-550, anhydrous ethanol and deionized water, and contains, by mass percentage of the solution, 10-40wt.% of silane coupling agent KH-550, 60-80wt.% of anhydrous ethanol and 5-10wt.% of deionized water.

4. The preparation method according to claim 1, characterized in that: The mass ratio of the nano-ferroferric oxide to the silane coupling agent is 1:20-1000.

5. The preparation method according to claim 1, characterized in that: The mass ratio of the surface silanized ferrosoferric oxide powder to N,N-dimethylformamide is 1:50-150, and the mass ratio of the surface silanized ferrosoferric oxide powder to graphene oxide is 1:1-7.

6. The preparation method according to claim 1, characterized in that: In the preparation of the graphene oxide polyurethane composite coating, the sample is placed in a magnetic field for directional curing for 2 to 8 hours, and then placed in a vacuum tube furnace for high-temperature curing to obtain the graphene polyurethane composite coating.

7. The preparation method according to any one of claims 1 or 6, characterized in that: The high temperature curing includes curing at 50° C. for 6 to 8 hours in a vacuum tube furnace until moisture disappears, then raising the temperature to 70° C. for curing for 24 to 30 hours until complete curing, and cooling at room temperature.

8. The preparation method according to any one of claims 1 or 6, characterized in that: The intensity of the magnetic field is 0.1 to 0.5 T, and the magnetic field directional solidification time is 2 to 4 hours.

9. An oriented graphene oxide polyurethane composite coating prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the composite coating according to claim 9 in protecting wind turbine blades and mechanical sliding surfaces.

Images