A superhydrophobic polyimide-based anti-corrosion and anti-fouling self-cleaning coating and its preparation method

Abstract

This invention discloses a superhydrophobic polyimide-based anti-corrosion, anti-fouling, and self-cleaning coating and its preparation method, belonging to the field of organic anti-corrosion coating technology. The preparation method first prepares at least one modified GO selected from POSS, silane coupling agent, chain alkylamine, and chain alkyl isocyanate; then, a composite underlayer slurry is applied to the substrate surface, followed by thermal imidization treatment to obtain a composite underlayer; finally, a SiO2 modified with alkane siloxane or perfluorosiloxane and a binder are coated on the surface of the composite underlayer to obtain the superhydrophobic polyimide-based anti-corrosion, anti-fouling, and self-cleaning coating. The composite coating preparation process of this invention is simple, highly operable, and possesses excellent superhydrophobic, anti-corrosion, and mechanical properties.

Description

Technical Field

[0001] This invention belongs to the field of self-cleaning coating development technology, and relates to a superhydrophobic polyimide-based anti-corrosion and anti-fouling self-cleaning coating and its preparation method. Background Technology

[0002] Superhydrophobic coatings have great application prospects in terms of self-cleaning, anti-icing, drag reduction, antifouling, and anti-corrosion properties. The development of micro / nanoscale materials technology provides theoretical guidance for the construction of superhydrophobic coatings, while modern process technologies have created favorable conditions for the large-area preparation of superhydrophobic coatings. Compared with TiO2, ZnO, carbon nanotubes, and MOF-based superhydrophobic coatings, the design and synthesis of SiO2 multifunctional superhydrophobic coatings are more universal and economical. Tao et al. prepared a double-crosslinked supramolecular silicon polymer / SiO2 composite superhydrophobic coating, and the obtained coating can spontaneously and repeatedly self-repair through surface recombination at room temperature. Furthermore, even under repeated mechanical or chemical damage, including sandpaper abrasion, solvent immersion, water dripping, and UV aging, the coating surface can still maintain its superhydrophobicity.

[0003] Currently, the resin matrices used for organic coatings have significant defects. For example, epoxy resins are prone to micropores and brittle fracture during curing, polyurethane has limited corrosion resistance, and polyacrylic acid has poor aging resistance. These limitations restrict the performance and practical applications of organic coatings. Furthermore, traditional anti-corrosion coatings are difficult to meet the harsh engineering applications under marine and acid / alkali conditions. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides a superhydrophobic polyimide-based anti-corrosion, anti-fouling, and self-cleaning coating and its preparation method, thereby solving the technical problem that existing superhydrophobic coatings are difficult to integrate with anti-corrosion, anti-fouling, and self-cleaning functions and have insufficient mechanical properties.

[0005] This invention is achieved through the following technical solution:

[0006] A method for preparing a superhydrophobic polyimide-based anti-corrosion, anti-fouling, and self-cleaning coating includes the following steps:

[0007] S1: The modifying agent and graphene oxide are added to organic solvent A, ultrasonically dispersed, and then refluxed to obtain modified GO; the modifying agent is at least one of POSS, silane coupling agent, chain alkylamine and chain alkyl isocyanate;

[0008] S2: Under nitrogen protection, dianhydride monomers are added in batches to a mixed solution of diamine monomers and organic solvent B. After reaction, a polyamic acid solution is obtained. The polyamic acid solution is added to the modified GO and ultrasonically dispersed to obtain a composite underlayer slurry. The composite underlayer slurry is coated onto the surface of the substrate, dried, and then subjected to thermal imidization treatment to obtain the composite underlayer.

[0009] S3: Coat the surface of the composite bottom layer with a composite top layer slurry containing alkane siloxane or perfluorosiloxane modified SiO2 and a binder. After drying, the superhydrophobic polyimide-based anti-corrosion and anti-fouling self-cleaning coating is obtained.

[0010] Preferably, in step S1, the polyamic acid is a POSS-crosslinked polyamic acid.

[0011] Preferably, in step S1, the POSS is one of monoamino oligosilsesquioxane, diamino oligosilsesquioxane, and octaamino oligosilsesquioxane.

[0012] Preferably, in step S1, the number of carbon atoms in the chain alkyl amine and the chain alkyl isocyanate is 7 to 18.

[0013] Preferably, in step S1, the graphene oxide accounts for 2.5% to 6.5% of the mass of the modifying reagent.

[0014] Preferably, in step S2, the dianhydride monomer is a fluorinated dianhydride monomer and / or the diamine monomer is a fluorinated diamine monomer.

[0015] Preferably, in step S2, the modified GO accounts for 0.01% to 1.50% of the mass of the polyamic acid solution.

[0016] Preferably, in step S3, in the composite top layer slurry containing alkane-siloxane or perfluorosiloxane-modified SiO2 and binder, the alkane-siloxane or perfluorosiloxane-modified SiO2 accounts for 0.01% to 1.50% of the binder mass.

[0017] Preferably, in step S3, before coating the composite top layer slurry, a PU intermediate layer is coated on the surface of the composite bottom layer, and then the composite top layer slurry is coated.

[0018] A superhydrophobic polyimide-based anti-corrosion, anti-fouling, and self-cleaning coating is prepared by the method described above; the impedance value of the composite coating is (1.32~3.29)×10⁻⁶. 11 Ω⋅cm 2 The composite coating has a contact angle of 152°~159°, and its low-frequency impedance value is 7.04 × 10⁻⁶ after 50 days of neutral salt spray testing. 10 Ω⋅cm 2 .

[0019] Compared with the prior art, the present invention has the following beneficial technical effects:

[0020] This invention discloses a method for preparing a superhydrophobic polyimide-based anti-corrosion, anti-fouling, and self-cleaning coating. In this preparation process, firstly, graphene oxide (GO) is modified using at least one of POSS, a silane coupling agent, a chain alkylamine, and a chain alkyl isocyanate. POSS, the silane coupling agent, the chain alkylamine, and the chain alkyl isocyanate are then chemically bonded to the surface of GO, effectively improving the dispersibility of GO in the system. Next, the modified GO is used as part of a filler, and a polyamic acid solution is added to it. After mixing, a composite underlayer is coated to obtain the final product. The addition of modified GO improves defects such as micropores and cracks generated during the thermosetting process of the coating, and greatly enhances the corrosion resistance of the coating. The excellent corrosion resistance of the coating is attributed to the barrier properties of the polyimide resin matrix and the reinforcing effect of the functional filler. In addition, the surface of the composite underlayer is coated with a composite top layer slurry containing alkane siloxane or perfluorosiloxane modified SiO2 and a binder, which significantly improves the hydrophobicity and mechanical properties of the substrate. Therefore, the coating prepared by the method of the present invention has good mechanical properties, self-cleaning properties and long-lasting corrosion resistance.

[0021] Furthermore, in step S1, the polyamic acid is POSS-crosslinked polyamic acid. After crosslinking modification of the polyamic acid with POSS reagent, it is used as the bottom coating to form a "star-shaped" crosslinked polyimide, which effectively enhances the shielding performance of the coating and improves the corrosion resistance.

[0022] Furthermore, in step S1, the number of carbon atoms in the chain alkyl amine and the chain alkyl isocyanate is 7 to 18, which allows the modifying agent to be covalently grafted onto the GO surface. On the one hand, this enhances the degree of GO exfoliation, and on the other hand, it imparts hydrophobic properties to the modified GO, thereby enhancing its barrier and shielding effect against corrosive media.

[0023] Furthermore, in step S1, the graphene oxide accounts for 2.5% to 6.5% of the mass of the modifying reagent, which allows the modified graphene oxide to be fully encapsulated by the modifying reagent, effectively improving the dispersibility of the graphene oxide.

[0024] Furthermore, in step S2, the dianhydride monomer is a fluorinated dianhydride monomer and / or the diamine monomer is a fluorinated diamine monomer, which effectively enhances the hydrophobic properties of the surface and improves the anti-corrosion effect.

[0025] Furthermore, in step S2, the modified GO accounts for 0.01% to 1.50% of the mass of the polyamic acid solution, which allows the modified GO to be fully dispersed in the polyimide matrix as a filler, thereby maximizing its anti-corrosion performance.

[0026] Furthermore, in step S3, in the composite top layer slurry containing alkane-siloxane or perfluorosiloxane-modified SiO2 and binder, the alkane-siloxane or perfluorosiloxane-modified SiO2 accounts for 0.01% to 1.50% of the binder mass. In this process, part of the binder dissolves, and part of the binder is in a microsphere state. The alkane-siloxane or perfluorosiloxane-modified SiO2 adheres to the surface of the microsphere-shaped binder. During the coating and curing process, the binder in the dissolved state bonds the modified SiO2 microspheres together to form a layered micro-nano structure, thereby creating a superhydrophobic surface.

[0027] Furthermore, in step S3, before coating the composite top layer slurry, a PU intermediate layer is coated on the surface of the composite bottom layer, and then the composite top layer slurry is coated. The addition of the intermediate PU layer effectively improves the bonding strength between the bottom coating and the top hydrophobic layer. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 The infrared spectrum of the NH2-POSS-terminated or suspended crosslinked fluorinated polyimide composite coating of Comparative Example 1 is shown.

[0030] Figure 2 The infrared spectrum of the comparative example 28NH2-POSS "star-shaped" crosslinked fluorinated polyimide composite coating;

[0031] Figure 3 Thermogravimetric curve of the coating in Example 3;

[0032] Figure 4 The corrosion performance test of the coating in Example 3 is shown in the figure. The left figure is the Nyquist curve and the right figure is the Bode curve.

[0033] Figure 5 The corrosion performance test of the coating in Example 4 is shown in the figure. The left figure is the Nyquist curve and the right figure is the Bode curve.

[0034] Figure 6 The corrosion performance of the composite coating in Comparative Example 1 is tested. The left figure shows the Nyquist curve, and the right figure shows the Bode curve.

[0035] Figure 7The corrosion performance of the composite coating in Comparative Example 2 is tested. The left figure shows the Nyquist curve, and the right figure shows the Bode curve.

[0036] Figure 8 The microstructure and contact angle of the double-layer superhydrophobic coating in Example 12 are shown in (a) and (b), where (c) is the surface morphology of the superhydrophobic coating; (d) is the cross-sectional morphology of the composite coating; and (d) is a diagram of the contact angle and sliding contact angle of the superhydrophobic surface. In Figure (d), CA is the static contact angle and SA is the rolling contact angle.

[0037] Figure 9 The microstructure and contact angle of the double-layer superhydrophobic coating in Example 13 are shown in (a) and (b) respectively. (c) shows the surface morphology of the superhydrophobic coating, (d) shows the cross-sectional morphology of the composite coating, and (c) shows the contact angle and sliding contact angle of the superhydrophobic surface. In (c), CA is the static contact angle and SA is the rolling contact angle. Detailed Implementation

[0038] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0039] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0040] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0041] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0042] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0043] This invention provides a method for preparing a superhydrophobic polyimide-based anti-corrosion, anti-fouling, and self-cleaning coating, comprising the following steps:

[0044] S1: The modifying agent and graphene oxide are added to organic solvent A, ultrasonically dispersed, and then refluxed to obtain modified GO; the modifying agent is at least one of POSS, silane coupling agent, chain alkylamine and chain alkyl isocyanate;

[0045] The POSS is one of monoamino oligomeric silsesquioxane, diamino oligomeric silsesquioxane, and octaamino oligomeric silsesquioxane. Specifically, the POSS used for modifying GO and the POSS used for crosslinking modified polyamic acid are both one of monoamino oligomeric silsesquioxane (NH2-POSS), diamino oligomeric silsesquioxane (2NH2-POSS), and octaamino oligomeric silsesquioxane (8NH2-POSS).

[0046] The silane coupling agent is 3-aminopropylmethyltrimethoxysilane, 3-aminopropylmethyltriethoxysilane, N-2-aminoethyl-3-aminopropylmethyldiethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, or N-2-aminoethyl-3-aminopropyltriethoxysilane.

[0047] In another, more preferred embodiment, the number of carbon atoms in the chain alkylamine and the chain alkyl isocyanate is 7 to 18.

[0048] The graphene oxide mentioned above accounts for 2.5% to 6.5% of the mass of the modifying reagent, more preferably 1% to 3.0%.

[0049] Taking tetradecyl isocyanate as an example, the process of modifying GO using chain alkylamines or chain alkyl isocyanates is as follows:

[0050] 200 mg of graphene oxide was added to 100 mL of DMF (dehydrated using molecular sieves). After sonication for 1 h, 14 g of tetradecyl isocyanate was added, and sonication continued for another h. Then, 4–6 drops of dibutyltin dilaurate (DBTDL) catalyst were added, and the mixture was incubated at 50 °C for 48 h. The solution was washed with three volumes of acetone, centrifuged at 4000 rpm, and the process was repeated five times. The product was dried in a vacuum drying oven to obtain chain-like alkyl isocyanate-modified GO.

[0051] In the above-mentioned GO modification process, the modifying agent is grafted onto the surface of graphene oxide via covalent bonds.

[0052] The organic solvent A mentioned above is at least one of N,N-dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), and N-methylpyrrolidone (NMP).

[0053] In the preparation of graphene oxide in this invention, natural flake graphite is used as raw material. Graphene oxide is prepared by modifying the Hummer method. The obtained graphene oxide is dialyzed in deionized water for about a week to remove impurity ions. After centrifugation, graphene oxide is obtained by freeze drying.

[0054] S2: Under nitrogen protection, dianhydride monomers are added in batches to a mixed solution of diamine monomers and organic solvent B, wherein the molar ratio of dianhydride monomers to diamine monomers is 1:1. After the reaction, a polyamic acid solution is obtained. The polyamic acid solution is added to the modified GO and ultrasonically dispersed for 10-60 min, preferably 10-30 min, to obtain a composite underlayer slurry. The solid content of the composite underlayer slurry is 8wt%-20wt%. The composite underlayer slurry is coated onto the surface of the substrate, dried, and then subjected to thermal imidization treatment to obtain the composite underlayer.

[0055] The dianhydride monomers include 4,4'-oxobisphthalic anhydride, 4,4'-(4,4'-isopropyldiphenoxy)bis(phthalic anhydride), pyromellitic dianhydride, biphenyltetracarboxylic dianhydride, triphenyl diether carboxylic dianhydride, 4,4'-(hexafluoroisopropene)phthalic anhydride, 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride, 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride, 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]hexafluoropropane dianhydride, 1,4-bis(3,4-dicarboxyphenoxy)phenyl dianhydride, and 1,3- One or more of the following: bis(3,4-dicarboxyphenoxy)phenyl dianhydride, 4,4'-bis(3,4-dicarboxyphenoxy)diphenylsulfone dianhydride, 4,4'-bis(3,4-dicarboxyphenoxy)benzophenone dianhydride, 4,4'-bis(3,4-dicarboxyphenoxy)biphenyl dianhydride, and 4,4'-bis(3,4-dicarboxyphenoxy)diphenyl ether dianhydride.

[0056] The diamine monomers are 4,4'-diaminodiphenyl ether, 4,4'-(1,4-phenyldioxy)bisphenylamine, 4,4'-diaminodiphenylmethane, 1,4-phenylenediamine, N-phenyl-1,4-phenylenediamine, 2,2'-bis[4-(4-aminophenoxyphenyl)]propane, 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane, 2,2-bis[4-(3-aminophenoxy)phenyl]hexafluoropropane, 2,2-bis[4-(2-trifluoromethyl-4-aminophenoxy)phenyl]propane, 2,2-[4-(2- [Trifluoromethyl-4-aminophenoxy]phenyl]hexafluoropropane, 4,4'-bis(2-trifluoromethyl-4-aminophenoxy)benzophenone, 4,4'-bis(2-trifluoromethyl-4-aminophenoxy)diphenyl sulfone, 4,4'-bis(2-trifluoromethyl-4-aminophenoxy)diphenyl sulfide, 4,4'-bis(2-trifluoromethyl-4-aminophenoxy)biphenyl, 1,3-bis(2-trifluoromethyl-4-aminophenoxy)benzene, 1,4-bis(2-trifluoromethyl-4-aminophenoxy)benzene, 1,3-bis[3'-trifluoromethyl-4'(4''-aminophenoxy)phenyl]benzene, 1,3-bis(4-amino-2-trifluoromethylphenoxy)benzene, 4,4''-bis(aminophenoxy)-3,3'-trifluoromethylterphenyl, 4 One or more of 4-bis[3'-trifluoromethyl-4'(4''-aminophenoxy)phenyl]biphenyl.

[0057] In a preferred embodiment, the dianhydride monomer is a fluorinated dianhydride monomer and / or the diamine monomer is a fluorinated diamine monomer.

[0058] In step S2, the modified GO accounts for 0.01% to 1.50% of the mass of the polyamic acid solution, preferably 0.02% to 1.0%, and more preferably 0.3% to 0.9%.

[0059] The organic solvent B mentioned above is at least one of N,N-dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), N-methylpyrrolidone (NMP), dimethyl sulfoxide (DMSO), and diacetone alcohol.

[0060] In a preferred embodiment, the polyamic acid is a POSS-crosslinked polyamic acid. Specifically, under nitrogen protection, the dianhydride monomer is added in batches to a mixed solution of diamine monomer and organic solvent B, followed by the addition of a POSS reagent. After the reaction, a POSS-crosslinked modified polyamic acid solution is obtained. Before adding the polyamic acid solution to the modified GO, the modified GO is first pre-dispersed in N,N-dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), or N-methylpyrrolidone (NMP). Then, the polyamic acid is added to the fully dispersed functionalized GO solution and further ultrasonically dispersed. Compared to directly adding functionalized graphene oxide to the polyamic acid, the pre-dispersion method avoids the functionalized graphene oxide being encapsulated by the polymer, preventing excessive agglomeration or uneven dispersion. The experimental sequence described above aids dispersion, primarily utilizing the density difference caused by the gravity sedimentation of the graphene oxide to promote dispersion. The uniform dispersion and stability of modified graphene oxide in the coating can effectively promote its excellent barrier effect as a two-dimensional nano-functional filler. The polyimide-based composite slurry obtained by the two-step method can be stably stored at room temperature for about 2 weeks without obvious precipitation.

[0061] The added POSS reagent accounts for 1% to 10% of the mass of polyamic acid, preferably 3% to 5%.

[0062] Before coating the composite underlayer slurry, the substrate surface is degreased, roughened, and ultrasonically cleaned to effectively increase the adhesion of the material.

[0063] The composite underlayer slurry is coated onto the surface of the substrate, dried, and then subjected to thermal imidization treatment to obtain the composite underlayer. Specifically, the sprayed sample is placed at room temperature for 1-2 hours to achieve surface drying, and then subjected to programmed thermal imidization treatment. This thermal imidization process includes evaporating a large amount of solvent at 80℃-135℃, preferably curing at 135℃ for 3 hours, and then completing imidization at 200-300℃. Initial imidization is carried out at 200℃ (2 hours), and more thorough imidization is completed at 240-300℃ depending on the imide system, with curing for about 1 hour.

[0064] The coating can be applied by spraying or brushing. In the spraying process, the composite underlayer slurry is ultrasonically dispersed evenly and then sprayed onto the surface of the metal substrate or part using a spray gun under 0.2 MPa oil-free compressed air or compressed nitrogen. The number of sprays is 10 to 30, preferably 15 to 20. After drying, a composite underlayer with a thickness of 1 to 100 μm is obtained, preferably 35 to 45 μm. The thickness is measured using a MINITEST 1100 coating thickness gauge.

[0065] The metal substrate can be electro-galvanized steel sheet, 304 stainless steel sheet, cold-rolled sheet, aluminized zinc steel sheet, aluminum alloy sheet, or any shape of metal part.

[0066] S3: Coat the surface of the composite bottom layer with a composite top layer slurry containing alkane siloxane or perfluorosiloxane modified SiO2 and a binder. After drying, the superhydrophobic polyimide-based anti-corrosion and anti-fouling self-cleaning coating is obtained.

[0067] The aforementioned alkane siloxanes are dodecyl siloxanes or hexadecyl siloxanes;

[0068] The perfluorosiloxane is perfluorodecyltrimethoxysilane, perfluorodecyltriethoxysilane, perfluorooctyltrimethoxysilane, or perfluorooctyltriethoxysilane.

[0069] In the above SiO2 modification process, the modifying agent reacts and combines with nano-SiO2 through dehydration condensation in a covalent manner.

[0070] The particle size of the SiO2 modified by the alkane siloxane or perfluorosiloxane is 10~40nm.

[0071] In the above process, in the composite top layer slurry containing alkane-siloxane or perfluorosiloxane-modified SiO2 and binder, the alkane-siloxane or perfluorosiloxane-modified SiO2 accounts for 0.01% to 1.50% of the binder mass.

[0072] The adhesives mentioned above include at least one of polyurethane, polyolefin, epoxy resin and polyacrylic acid.

[0073] The above-mentioned method uses a composite coating as a base layer to prepare a superhydrophobic coating on its surface. A low surface energy nano-SiO2 modified with an adhesive is used to prepare the superhydrophobic layer. This serves two purposes: firstly, it binds the SiO2 particles to create a micro-nano rough surface, and secondly, the adhesive firmly bonds to the surface of the composite coating. Alternatively, polyurethane or epoxy adhesives can be used as an intermediate transition layer between the composite coating and the superhydrophobic coating, serving two functions: firstly, it ensures a strong bond between the different layers; and secondly, it embeds a superhydrophobic layer in the intermediate transition layer to increase the mechanical durability of the superhydrophobic layer.

[0074] In step S3, before applying the composite top layer slurry, a PU intermediate layer is applied to the surface of the composite bottom layer, and then the composite top layer slurry is applied. Here, PU is polyurethane.

[0075] This invention also discloses a superhydrophobic polyimide-based anti-corrosion and anti-fouling self-cleaning coating, prepared by the above method; the impedance value of the composite coating is (1.32~3.29)×10⁻⁶. 11 Ω⋅cm 2 The composite coating has a contact angle of 152°~159°, and still exhibits good corrosion resistance after 50 days of neutral salt spray testing, with a low-frequency impedance value as high as 7.04 × 10⁻⁶. 10Ω⋅cm 2 The double-layer or sandwich superhydrophobic coating still retains its superhydrophobic properties after 100 sandpaper abrasions and 80 tape glass mechanical tests.

[0076] This invention discloses a method for preparing a superhydrophobic polyimide-based anti-corrosion, anti-fouling, and self-cleaning coating. The method uses polyimide as the main film-forming substance of the coating. The polyimide can be a specific fluorinated or non-fluorinated molecular structure, or a blend of two or more types, or even a polyimide crosslinked with octaaminooliposilsesquioxane (8NH2-POSS) in a "star-shaped" configuration. Functionalized graphene oxide two-dimensional fillers are stably dispersed in the coating resin matrix, avoiding the common problem of uneven and stable dispersion when using graphene directly or graphene oxide. The addition of functionalized two-dimensional fillers improves defects such as micropores and cracks generated during the thermosetting process, while significantly enhancing the anti-corrosion performance of the coating. The excellent corrosion resistance of the coating is attributed to the barrier properties of the polyimide resin matrix and the reinforcing effect of the functional fillers. Furthermore, a superhydrophobic coating can be prepared based on the composite coating. A slurry of nano-SiO2 modified with long-chain alkane siloxane or perfluorosiloxane and combined with a binder is sprayed onto the surface of the composite coating to prepare a double-layer or "sandwich" superhydrophobic coating, forming a multi-layer isolation barrier. This functional coating combines the corrosion resistance of the composite coating with the significant antifouling and self-cleaning properties of the superhydrophobic coating, making the prepared multi-layer organic composite superhydrophobic coating have excellent anti-corrosion, antifouling and self-cleaning properties.

[0077] This invention uses polyimide (non-fluorinated or fluorinated) or POSS-crosslinked polyimide as the matrix resin for composite coatings, preparing intrinsically hydrophobic, thickness-controllable, and high-temperature resistant polyimide-based composite anti-corrosion coatings. Fluorinated polyimides possess highly stable aromatic heterocyclic structural units and hydrophobic trifluoromethyl functional groups in their chain segments. Furthermore, POSS, which possesses hydrophobic and interfacial compatibility functions, is introduced into the fluorinated polyimide molecule through either POSS "end-capping" or "star-shaped" crosslinking. This POSS-hybridized polyimide, as the matrix resin for the composite coating, exhibits intrinsic hydrophobicity, mechanical properties, and excellent anti-corrosion performance. Its glass transition temperature is generally above 200 °C, and its initial decomposition temperature is above 500 °C, demonstrating high heat resistance. Electrochemical testing proves that the impedance value of the fluorinated polyimide-based composite coating reaches as high as 1.58 × 10⁻⁶. 11 Ω⋅cm 2 The impedance value of the non-fluorinated polyimide composite coating reaches 1.32 × 10⁻⁶. 11 Ω⋅cm 2 The impedance value of the POSS crosslinked fluorinated polyimide composite coating reaches 3.29 × 10⁻⁶. 11 Ω⋅cm 2 This indicates that the polyimide-based composite coating has excellent corrosion resistance.

[0078] The polyimide-based composite anti-corrosion coating prepared by the present invention, consisting of fluorinated polyimide, non-fluorinated polyimide, and POSS crosslinked polyimide, has high heat resistance, good mechanical properties, and excellent intrinsic hydrophobicity. Furthermore, the coating thickness can be controlled by changing the number of sprayings and adjusting the spraying flow rate.

[0079] The polyimide or POSS crosslinked polyimide-based composite anti-corrosion coating prepared by this invention exhibits excellent corrosion resistance due to the presence of hydrophobic crown groups such as POSS and trifluoromethyl groups in the polymer molecular backbone, resulting in a low moisture absorption rate. The polyimide-based composite superhydrophobic coating prepared by this invention uses a composite coating as a base layer, and then sprays a SiO2 superhydrophobic slurry onto its surface to prepare a multilayer composite superhydrophobic coating. The polyimide-based composite superhydrophobic coating prepared by this invention combines the excellent barrier properties of the composite coating with the significant self-cleaning and antifouling properties of the superhydrophobic coating, endowing the multilayer superhydrophobic coating with comprehensive self-cleaning, antifouling, and anti-corrosion properties.

[0080] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0081] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" refers to weight percentage, "parts" refers to parts by weight, and "ratio" refers to weight proportion.

[0082] Example 1

[0083] Pre-oxidation of natural flake graphene: Under 25 ℃ water bath conditions, 30 mL of concentrated sulfuric acid was added to a 250 mL three-necked flask equipped with a mechanical stirrer. Then, 5 g of natural flake graphene, 3 g of potassium persulfate, and 8 g of phosphorus pentoxide were added with stirring. The temperature was slowly increased to 60 ℃ for 3 h, then cooled to 25 ℃ and oxidation continued for 5 h. The experiment was then completed by filtration and washing until the filtrate was neutral. The product was then vacuum dried at 50 ℃ for 24 h before use.

[0084] Preparation of graphene oxide: In a 500 mL three-necked flask equipped with a mechanical stirrer, 360 mL of concentrated sulfuric acid and 40 mL of phosphoric acid were added. 3 g of pre-oxidized graphene was then added with rapid stirring. After thorough mixing, 18 g of potassium permanganate powder was added within 2 h. The temperature was then raised to 50 °C and maintained at this temperature with stirring for 12 h. The temperature was then lowered to 25 °C. The reaction liquid was poured into 400 mL of ice water with stirring. 30% hydrogen peroxide solution was added dropwise until the system turned bright yellow and no more bubbles were generated. An equal volume of 10% dilute hydrochloric acid solution was added, and SO4 was removed by dialysis. 2- After removing impurity ions, the solution is centrifuged and concentrated, and then freeze-dried to obtain graphene oxide.

[0085] Example 2

[0086] Preparation of functionalized graphene oxide:

[0087] (1) Single NH2-POSS functionalized graphene oxide: 350 mg graphene oxide, 5.0 g NH2-POSS, 100 mg dicyclohexylcarbodiimide and 50 mL tetrahydrofuran were accurately weighed and dissolved in a 250 mL single-necked flask and sonicated for 30 min. The above dispersion was then refluxed for 48 h. The solvent was then removed by rotary evaporation and heat-treated at 120 °C for 12 h to obtain the product.

[0088] The above product was dissolved in 50 mL of tetrahydrofuran and precipitated in 500 mL of methanol. The experiment was repeated three times to remove unreacted NH2-POSS. The final product was then obtained by filtration through a 0.22 μm organic filter membrane, dried under vacuum at 80 °C, and stored for later use.

[0089] (2) γ-methacryloxypropyltrimethoxysilane (KH570) functionalized graphene oxide: 500 mg KH570 and 50 g anhydrous ethanol were added to a 250 mL single-necked flask and sonicated for 30 min. The above dispersion was then refluxed for 24 h. The product was then washed three times with deionized water and anhydrous ethanol alternately and dried at 80 °C for 24 h to obtain KH570 modified graphene oxide.

[0090] Example 3

[0091] Functionalized graphene oxide was prepared using the same modified Hummer method as in Example 1 and the same method as in Example 2 (1). Under nitrogen protection, fluorinated polyamic acid was synthesized by reacting 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane and 4,4'-(hexafluoroisopropene)phthalic anhydride in a molar ratio of 1:1 at room temperature for 6 h and at 80 °C for 4 h. A fluorinated polyamic acid mixed solution with a mass fraction of 0.3 wt.% of functionalized graphene oxide (Example 2 (1)) was prepared. The prepared mixed solution was sprayed onto a metal substrate, and a fluorinated polyimide-based composite coating with a thickness of 42 μm was obtained by thermal imidization at room temperature for pre-curing and at high temperature program controlled temperatures of 135, 205 and 280 °C for 3, 1 and 1 h respectively.

[0092] Example 4

[0093] Functionalized graphene oxide was prepared using the same modified Hummer method as in Example 1 and the same method as in Example 2 (1). Under nitrogen protection, polyamic acid was synthesized by reacting 4,4'-diaminodiphenyl ether and 4,4'-(4,4'-isopropyldiphenoxy)bis(phthalic anhydride) in a molar ratio of 1:1 at room temperature for 4 h and 70 °C for 2 h. A polyamic acid mixed solution with a mass fraction of 0.3 wt.% functionalized graphene oxide (Example 2 (1)) was prepared. The prepared mixed solution was sprayed onto a metal substrate, and a polyimide-based composite coating with a thickness of 44 μm was obtained by pre-curing at room temperature and thermal imidization at high-temperature programmed temperatures of 135, 210, and 280 °C for 3, 1, and 1 h respectively.

[0094] Example 5

[0095] Graphene oxide was prepared using the same method as in Example 1, and functionalized graphene oxide was prepared using the same method as in Example 2 (2). Fluorinated polyamic acid was synthesized using the same method as in Example 3. A mixed solution of fluorinated polyamic acid with a mass fraction of 0.3 wt% functionalized graphene oxide (Example 2 (2)) was prepared; the prepared mixed solution was sprayed onto a metal substrate, and then subjected to room temperature pre-curing and high-temperature programmed temperature control of 135, 205 and 280°C for curing times of 3, 1 and 1 h respectively to obtain a fluorinated polyimide-based composite coating with a coating thickness of 44 μm.

[0096] Example 6

[0097] Graphene oxide was prepared using the same method as in Example 1, and functionalized graphene oxide was prepared using the same method as in Example 2 (2). Polyamic acid was synthesized using the same method as in Example 4. A polyamic acid mixed solution with a mass fraction of 0.3 wt% functionalized graphene oxide (Example 2 (2)) was prepared; the prepared mixed solution was sprayed onto a metal substrate, and after room temperature pre-curing and high-temperature programmed temperature control of 135, 210 and 280 °C for corresponding curing times of 3, 1 and 1 h, a polyimide-based composite coating with a coating thickness of 45 μm was obtained.

[0098] Example 7

[0099] Graphene oxide was prepared using the same modified Hummer method as in Example 1; functionalized graphene oxide was prepared using the same method as in Example 2(1). Fluorinated polyamic acid was synthesized using the same method as in Example 3. A mixed solution of fluorinated polyamic acid with a mass fraction of 0.3 wt% functionalized graphene oxide (Example 2(1)) was prepared; the prepared mixed solution was sprayed onto a metal substrate, and then subjected to room temperature pre-curing and high-temperature programmed temperature control of 135, 205 and 280 °C for curing times of 3, 1 and 1 h respectively to obtain a fluorinated polyimide-based composite coating with a coating thickness of 43 μm.

[0100] Example 8

[0101] Graphene oxide was prepared using the same modified Hummer method as in Example 1; functionalized graphene oxide was prepared using the same method as in Example 2(1). Polyamic acid was synthesized using the same method as in Example 4. A polyamic acid mixed solution with a mass fraction of 0.5 wt% functionalized graphene oxide (Example 2(1)) was prepared; the prepared mixed solution was sprayed onto a metal substrate, and after room temperature pre-curing and high-temperature programmed temperature control of 135, 210 and 280 °C for corresponding curing times of 3, 1 and 1 h, a polyimide-based composite coating with a coating thickness of 45 μm was obtained.

[0102] Example 9

[0103] Graphene oxide was prepared using the same modified Hummer method as in Example 1; functionalized graphene oxide was prepared using the same method as in Example 2 (2). Fluorinated polyamic acid was synthesized using the same method as in Example 3. 0.5 wt% functionalized graphene oxide (Example 2 (2)) was added to the fluorinated polyamic acid slurry; the prepared mixed solution was sprayed onto a metal substrate and subjected to thermal imidization at 135, 280 and 300 °C for 2, 1 and 0.5 h respectively to obtain a fluorinated polyimide composite anti-corrosion coating with a thickness of 42 μm.

[0104] Example 10

[0105] Graphene oxide was prepared using the same modified Hummer method as in Example 1; functionalized graphene oxide was prepared using the same method as in Example 2 (2). Polyamic acid was synthesized using the same method as in Example 4. 0.5 wt% functionalized graphene oxide (Example 2 (2)) was added to the polyamic acid slurry; the prepared mixed solution was sprayed onto a metal substrate and subjected to thermal imidization at 135, 260, and 280 °C for 2, 1, and 0.5 h respectively to obtain a polyimide composite anti-corrosion coating with a thickness of 43 μm.

[0106] Fluorinated polyamic acid was obtained using the same synthesis method as in Example 3. A polyamic acid mixed solution with the same mass content as the composite coating was sprayed onto a metal substrate and subjected to thermal imidization processes at 135, 280, and 300 °C for curing times of 2, 1, and 0.5 h, respectively, to obtain a fluorinated polyimide coating with a thickness of 46 μm, which was recorded as a blank sample.

[0107] Comparative Example 1

[0108] Fluorinated polyamic acid was synthesized using the same method as in Example 3. Then, 5 wt% NH2-POSS was added at room temperature and the reaction was maintained at room temperature for 10 h to further obtain POSS-terminated or side-chain-suspended fluorinated polyamic acid. At the same time, functionalized graphene oxide (Example 2 (1)) with the same mass content as in Example 3 was added to obtain a mixed slurry. The above slurry was sprayed onto a metal substrate at a pressure of 0.2 MPa. After thermal imidization at 135, 280 and 300 °C for curing times of 2, 1 and 0.5 h respectively, a POSS-suspended or end-terminated fluorinated polyimide coating was obtained with a coating thickness of 42 μm, which was recorded as the comparative sample of Example 3.

[0109] Comparative Example 2

[0110] Fluorinated polyamic acid was synthesized using the same method as in Example 3. Then, 8NH2-POSS with a mass fraction of 5wt% was added at room temperature and the reaction was maintained at room temperature for 10 h to further obtain POSS "star-shaped" crosslinked fluorinated polyamic acid. At the same time, functionalized graphene oxide (Example 2 (2)) with the same mass content as in Example 3 was added to obtain a mixed slurry. The above slurry was sprayed onto a metal substrate at a pressure of 0.2 MPa. After thermal imidization at 135, 280 and 300 °C for curing times of 2, 1 and 0.5 h respectively, a POSS "star-shaped" crosslinked fluorinated polyimide coating was obtained with a coating thickness of 42 μm, which was recorded as the comparative sample of Example 4.

[0111] Example 11

[0112] A polyamic acid mixed solution of functionalized graphene oxide (Example 2 (1)) with a mass fraction of 0.5 wt% was prepared; the prepared mixed solution was sprayed onto a metal substrate, and a polyimide-based composite coating with a thickness of 45 μm was obtained by pre-curing at room temperature and thermal imidization at high temperature program temperature control of 135, 210 and 280 °C for 3, 1 and 1 h respectively.

[0113] Example 12

[0114] Preparation of the superhydrophobic coating: 2.5 g of SiO2 was added to a mixed solution of 500 mL ethanol and 2.5 g sodium methylsiloxane. The mixture was stirred at 500 r / min for 20 min, followed by ultrasonic dispersion for 20 min. At room temperature, 0.75 mL of tetraethyl orthosilicate (TEOS) was added, and the mixture was stirred at high speed for 30 min. Then, 5 mL of hexadecyltrimethoxysilane (HDTMS) was added dropwise. After the addition was complete, stirring was continued for 2 h to terminate the reaction. The modified nano-SiO2 suspension was centrifuged at 8000 r / min and washed three times with anhydrous ethanol. The washed nano-SiO2 solid was vacuum dried at 60 ℃ for 12 h to obtain superhydrophobic modified nano-SiO2 powder, named HD-SiO2.

[0115] Preparation of the superhydrophobic suspension: 1.2 g of POA was dissolved in 3 g of butyl acetate and magnetically stirred at room temperature for 30 min. 3 g of ethyl acetate solution was then added, and the resulting mixed solution was denoted as solution A. Simultaneously, 1.5 g of anhydrous ethanol was added to a sample vial containing 1.0 g of HD-SiO2 and sonicated for 30 min. The resulting semi-solid was denoted as solution B. Solution B was then added dropwise to solution A, and stirring was continued for 1.5 h to obtain the superhydrophobic suspension. Then, the above suspension was transferred to a spray gun and sprayed onto the surface of the composite coating prepared in Example 3 under an air pressure of 0.2 MPa. The nozzle diameter of the spray gun was 1.0 mm. During the spraying process, the distance between the spray gun and the coating was kept at 12-20 cm. The spraying speed was controlled, and the spray gun was slowly moved from top to bottom in an "S" shape. This ensures that the prepared superhydrophobic coating has a uniform and compact roughness, which ensures the mechanical durability and continuous water transport of the superhydrophobic coating. The prepared upper superhydrophobic layer was named POA / HD-SiO2, and the double-layer superhydrophobic coating was named FPI / POSS-GO@POA / HD-SiO2. The superhydrophobic coating was obtained by curing at room temperature for 24 h.

[0116] Example 13

[0117] Preparation of the superhydrophobic coating: 3.0 g of hydrophilic nano-SiO2 (10–35 nm) was dispersed in 150 mL of an ethanol / water mixture. The mixture was mechanically stirred for 20 min, followed by ultrasonic dispersion for 20 min to ensure thorough dispersion. Then, 3 g of sodium methylsiloxane was added to the dispersion under continuous mechanical stirring at 500 r / min, and stirring continued for another 20 min. Next, 3200 μL of perfluoroquinoltriethoxysilane and 900 μL of LTEOS were added to the reaction mixture, and stirring continued at room temperature for 1.5 h. At this point, the solution became a homogeneous milky white state. The modified nano-SiO2 suspension was centrifuged at 8000 r / min and washed three times with anhydrous ethanol. The washed modified nano-SiO2 semi-solid was vacuum dried at 60 ℃ for 6 h to obtain fluorinated modified nano-SiO2 powder, named POA / PF-SiO2.

[0118] Then, 1.4 g of POA was dissolved in 5.5 g of butyl acetate and magnetically stirred for 30 min at room temperature. At this time, a nearly semi-solid slurry, pre-treated by ultrasound, consisting of 1.2 g of PF-SiO2 and 2.0 g of anhydrous ethanol, was added dropwise to the solution. After magnetic stirring for 2 h and ultrasonic dispersion for 30 min, a superhydrophobic suspension was obtained. Finally, the suspension was transferred to a spray gun and sprayed onto the surface of the B-FPI / POSS-4 polymer nanocomposite coating under an air pressure of 0.2 MPa. During spraying, the distance between the spray gun and the coating was maintained at 10–20 cm, the spray rate was controlled, and the spray gun was moved slowly from top to bottom in an “S” shape. This ensured that the prepared superhydrophobic coating had a uniform and compact roughness, guaranteeing its mechanical durability and continuous water transport. The prepared bilayer superhydrophobic layer was named FPI / POSS-GO@PF-SiO2, and the superhydrophobic coating was obtained after curing at room temperature for 24 h.

[0119] Example 14

[0120] Preparation of the superhydrophobic coating: 2.5 g of SiO2 was added to a mixed solution of 500 mL ethanol and 2.5 g sodium methylsiloxane. The mixture was stirred at 500 r / min for 20 min, followed by ultrasonic dispersion for 20 min. At room temperature, 0.75 mL of tetraethyl orthosilicate (TEOS) was added, and the mixture was stirred at high speed for 30 min. Then, 5 mL of hexadecyltrimethoxysilane (HDTMS) was added dropwise. After the addition was complete, stirring was continued for 2 h to terminate the reaction. The modified nano-SiO2 suspension was centrifuged at 8000 r / min and washed three times with anhydrous ethanol. The washed nano-SiO2 solid was vacuum dried at 60 ℃ for 12 h to obtain superhydrophobic modified nano-SiO2 powder, named HD-SiO2.

[0121] Preparation of the superhydrophobic suspension: 1.2 g of POA was dissolved in 3 g of butyl acetate and magnetically stirred at room temperature for 30 min. 3 g of ethyl acetate solution was then added, and the resulting mixed solution was denoted as solution A. Simultaneously, 1.5 g of anhydrous ethanol was added to a sample vial containing 1.0 g of HD-SiO2 and sonicated for 30 min. The resulting semi-solid was denoted as solution B. Solution B was then added dropwise to solution A, and stirring was continued for 1.5 h to obtain the superhydrophobic suspension. Then, the above suspension was transferred to a spray gun and sprayed onto the surface of the composite coating prepared in Example 4 under an air pressure of 0.2 MPa. The nozzle diameter of the spray gun was 1.0 mm. During the spraying process, the distance between the spray gun and the coating was kept at 12-20 cm. The spraying speed was controlled, and the spray gun was slowly moved from top to bottom in an "S" shape. This ensures that the prepared superhydrophobic coating has a uniform and compact roughness, which ensures the mechanical durability and continuous water transport of the superhydrophobic coating. The prepared upper superhydrophobic layer was named POA / HD-SiO2, and the double-layer superhydrophobic coating was named PI / POSS-GO@POA / HD-SiO2. The superhydrophobic coating was obtained by curing at room temperature for 24 h.

[0122] Example 15

[0123] Preparation of the superhydrophobic coating: 3.0 g of hydrophilic nano-SiO2 (10–35 nm) was dispersed in 150 mL of an ethanol / water mixture. The mixture was mechanically stirred for 20 min, followed by ultrasonic dispersion for 20 min to ensure thorough dispersion. Then, 3 g of sodium methylsiloxane was added to the dispersion under continuous mechanical stirring at 500 r / min, and stirring continued for another 20 min. Next, 3200 μL of perfluoroquinoltriethoxysilane and 900 μL of LTEOS were added to the reaction mixture, and stirring continued at room temperature for 1.5 h. At this point, the solution became a homogeneous milky white state. The modified nano-SiO2 suspension was centrifuged at 8000 r / min and washed three times with anhydrous ethanol. The washed modified nano-SiO2 semi-solid was vacuum dried at 60 ℃ for 6 h to obtain fluorinated modified nano-SiO2 powder, named POA / PF-SiO2.

[0124] Then, 1.4 g of POA was dissolved in 5.5 g of butyl acetate and magnetically stirred at room temperature for 30 min. At this time, a nearly semi-solid slurry, pre-treated by ultrasound, consisting of 1.2 g of PF-SiO2 and 2.0 g of anhydrous ethanol, was added dropwise to the solution. After magnetic stirring for 2 h and ultrasonic dispersion for 30 min, a superhydrophobic suspension was obtained. Finally, the suspension was transferred to a spray gun and sprayed onto the surface of the composite coating prepared in Example 4 under an air pressure of 0.2 MPa. During spraying, the distance between the spray gun and the coating was maintained at 10–20 cm, the spraying speed was controlled, and the spray gun was slowly moved downwards in an “S” shape. This ensured that the prepared superhydrophobic coating had a uniform and compact roughness, guaranteeing its mechanical durability and continuous water transport. The prepared double-layer superhydrophobic layer was named PI / POSS-GO@PF-SiO2, and the superhydrophobic coating was obtained after curing at room temperature for 24 h.

[0125] Example 16

[0126] This embodiment discloses a method for preparing a superhydrophobic polyimide-based anti-corrosion and anti-fouling self-cleaning coating, including the following steps:

[0127] Under nitrogen protection, 4,4'-oxophthalic anhydride was added in batches to a mixed solution of 4,4'-diaminodiphenyl ether, 4,4'-(1,4-phenyldioxy)bisphenylamine, and N,N-dimethylacetamide (DMAc), wherein the molar ratio of the dianhydride monomer to the diamine monomer was 1:1. After the reaction, a polyamic acid solution was obtained. The polyamic acid solution was added to the monoamino oligomeric silsesquioxane-modified graphene oxide and ultrasonically dispersed for 10-60 min, preferably 10-30 min, to obtain a composite underlayer slurry with a solid content of 8 wt%-20 wt%. The composite underlayer slurry was coated onto the surface of a substrate, dried, and then subjected to thermal imidization treatment to obtain the composite underlayer.

[0128] The monoamino oligomeric silsesquioxane-modified graphene oxide accounts for 0.01% of the mass of the polyamic acid solution.

[0129] A PU intermediate layer is coated on the surface of the composite base layer. After drying, a composite top layer slurry containing dodecylsiloxane-modified SiO2 and a binder is coated on the surface of the PU intermediate layer. After drying, the superhydrophobic polyimide-based anti-corrosion, anti-fouling, and self-cleaning coating is obtained.

[0130] The dodecylsiloxane-modified SiO2 has a particle size of 10 nm.

[0131] In the above process, in the composite top layer slurry containing dodecylsiloxane-modified SiO2 and binder, the dodecylsiloxane-modified SiO2 accounts for 0.01% of the binder mass.

[0132] The adhesives mentioned above are polyurethane-based.

[0133] Example 17

[0134] This embodiment discloses a method for preparing a superhydrophobic polyimide-based anti-corrosion and anti-fouling self-cleaning coating, including the following steps:

[0135] Under nitrogen protection, 4,4'-(4,4'-isopropyldiphenoxy)bis(phthalic anhydride) was added in batches to a mixed solution of 2,2'-bis[4-(4-aminophenoxyphenyl)]propane, 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane, and N,N-dimethylformamide DMF, wherein the molar ratio of dianhydride monomer to diamine monomer was 1:1. After the reaction, a polyamic acid solution was obtained. The polyamic acid solution was added to the 3-aminopropylmethyltrimethoxysilane-modified graphene oxide and ultrasonically dispersed for 10-60 min, preferably 10-30 min, to obtain a composite underlayer slurry with a solid content of 8wt%-20wt%. The composite underlayer slurry was coated onto the surface of a substrate, dried, and then subjected to thermal imidization treatment to obtain the composite underlayer.

[0136] The modified GO accounts for 1.50% of the mass of the polyamic acid solution.

[0137] A PU intermediate layer is coated on the surface of the composite base layer. After drying, a composite top layer slurry containing perfluorodecyltrimethoxysilane modified SiO2 and a binder is coated on the surface of the PU intermediate layer. After drying, the superhydrophobic polyimide-based anti-corrosion, anti-fouling, and self-cleaning coating is obtained.

[0138] The particle size of the perfluorodecyltrimethoxysilane modified SiO2 is 40 nm.

[0139] In the above process, in the composite top layer slurry containing perfluorodecyltrimethoxysilane-modified SiO2 and binder, the perfluorodecyltrimethoxysilane-modified SiO2 accounts for 1.50% of the binder mass.

[0140] The adhesives mentioned above are polyurethane-based.

[0141] Example 18

[0142] This embodiment discloses a method for preparing a superhydrophobic polyimide-based anti-corrosion and anti-fouling self-cleaning coating, including the following steps:

[0143] S1: The modifying agent and graphene oxide are added to organic solvent A, ultrasonically dispersed, and then refluxed to obtain modified GO; the modifying agent is at least one of POSS, silane coupling agent, chain alkylamine and chain alkyl isocyanate;

[0144] Graphene oxide accounts for 2.5% of the mass of the modifying reagent.

[0145] S2: Under nitrogen protection, dianhydride monomers are added in batches to a mixed solution of diamine monomers and organic solvent B, wherein the molar ratio of dianhydride monomers to diamine monomers is 1:1. After the reaction, a polyamic acid solution is obtained. The polyamic acid solution is added to the modified GO and ultrasonically dispersed for 10-60 min, preferably 10-30 min, to obtain a composite underlayer slurry. The solid content of the composite underlayer slurry is 8wt%-20wt%. The composite underlayer slurry is coated onto the surface of the substrate, dried, and then subjected to thermal imidization treatment to obtain the composite underlayer.

[0146] The modified GO accounts for 1.0% of the mass of the polyamic acid solution.

[0147] S3: A PU intermediate layer is coated on the surface of the composite bottom layer. After drying, a composite top layer slurry containing alkane siloxane or perfluorosiloxane modified SiO2 and a binder is coated on the surface of the PU intermediate layer. After drying, the superhydrophobic polyimide-based anti-corrosion and anti-fouling self-cleaning coating is obtained.

[0148] In the above process, in the composite top layer slurry containing alkane-siloxane or perfluorosiloxane-modified SiO2 and binder, the alkane-siloxane or perfluorosiloxane-modified SiO2 accounts for 1.0% of the binder mass.

[0149] The adhesive mentioned above is a polyacrylic acid-based adhesive.

[0150] Example 19

[0151] This embodiment discloses a method for preparing a superhydrophobic polyimide-based anti-corrosion and anti-fouling self-cleaning coating, including the following steps:

[0152] S1: The modifying agent and graphene oxide are added to organic solvent A, ultrasonically dispersed, and then refluxed to obtain modified GO; the modifying agent is at least one of POSS, silane coupling agent, chain alkylamine and chain alkyl isocyanate;

[0153] The graphene oxide mentioned above accounts for 1% of the mass of the modifying reagent.

[0154] S2: Under nitrogen protection, dianhydride monomers are added in batches to a mixed solution of diamine monomers and organic solvent B, wherein the molar ratio of dianhydride monomers to diamine monomers is 1:1. After the reaction, a polyamic acid solution is obtained. The polyamic acid solution is added to the modified GO and ultrasonically dispersed for 10-60 min, preferably 10-30 min, to obtain a composite underlayer slurry with a solid content of 8 wt%. The composite underlayer slurry is coated onto the surface of a substrate, dried, and then subjected to thermal imidization treatment to obtain the composite underlayer.

[0155] In step S2, the modified GO accounts for 0.3% of the mass of the polyamic acid solution.

[0156] S3: A PU intermediate layer is coated on the surface of the composite bottom layer. After drying, a composite top layer slurry containing alkane siloxane or perfluorosiloxane modified SiO2 and a binder is coated on the surface of the PU intermediate layer. After drying, the superhydrophobic polyimide-based anti-corrosion and anti-fouling self-cleaning coating is obtained.

[0157] The particle size of the SiO2 modified by the alkane siloxane or perfluorosiloxane is 20 nm.

[0158] In the above process, in the composite top layer slurry containing alkane-siloxane or perfluorosiloxane-modified SiO2 and binder, the alkane-siloxane or perfluorosiloxane-modified SiO2 accounts for 1.2% of the binder mass.

[0159] The adhesives mentioned above are epoxy resins.

[0160] To test the performance of the composite coating obtained by this invention, the following characterization was performed:

[0161] Figure 1 The infrared spectrum of the NH2-POSS-terminated or suspended crosslinked fluorinated polyimide composite coating of Comparative Example 1 is shown in the figure. As can be seen from the figure, no characteristic absorption peaks of -COOH and -NH2 were found in the infrared curve, indicating that imidization was complete.

[0162] Figure 2 The infrared spectrum of the comparative example 28NH2-POSS "star-shaped" crosslinked fluorinated polyimide composite coating is shown in the figure. As can be seen from the figure, it is located at 1100 cm⁻¹. -1 The COC absorption peak at 1083 cm⁻¹ disappears after POSS crosslinking and reappears at 1083 cm⁻¹. -1 The absorption peak belongs to the Si-O-Si characteristic functional group, proving that POSS and fluorinated polyamic acid have successfully undergone a "star-shaped" crosslinking reaction.

[0163] Figure 3 The thermogravimetric curve of the coating in Example 3 shows that the temperature at which 5% of the weight loss occurs is 536 °C, indicating that the fluorinated polyimide composite coating has excellent heat resistance.

[0164] Figure 4 The corrosion performance of the coating in Example 3 was tested. The left figure shows the Nyquist curve, and the right figure shows the Bode curve. As can be seen from the figures, the |Z| of the coating... 0.01 Hz The value is 1.01 × 10 11 Ω⋅cm 2 .

[0165] Figure 5 The corrosion performance of the coating in Example 4 was tested. The left figure shows the Nyquist curve, and the right figure shows the Bode curve. As can be seen from the figures, the |Z| of the coating... 0.01 Hz The value is 1.12 × 10 11 Ω⋅cm 2 It has good barrier properties.

[0166] Figure 6 For the corrosion performance test of the composite coating in Comparative Example 1, the left figure is the Nyquist curve and the right figure is the Bode curve. As can be seen from the figures, the |Z| of the coating... 0.01 Hz The value is 1.26 × 10 11 Ω⋅cm 2 .

[0167] Figure 7 For the corrosion performance test of the composite coating in Comparative Example 2, the left figure is the Nyquist curve and the right figure is the Bode curve. As can be seen from the figures, the |Z| of the coating... 0.01 Hz The value is 1.45 × 10 11 Ω⋅cm 2 .

[0168] Figure 8 The microstructure and contact angle of the double-layer superhydrophobic coating in Example 12 are shown in (a) and (b), where (c) is the surface morphology of the superhydrophobic coating; (d) is the cross-sectional morphology of the composite coating; and (d) is a diagram of the contact angle and sliding contact angle of the superhydrophobic surface. In Figure (d), CA is the static contact angle and SA is the rolling contact angle. As can be seen from the figure, CA = 156.6° and SA = 5.6° of the superhydrophobic coating, indicating that the superhydrophobic coating has excellent hydrophobicity.

[0169] Figure 9 The microstructure and contact angle of the double-layer superhydrophobic coating in Example 13 are shown in (a) and (b) respectively. (c) shows the surface morphology of the superhydrophobic coating, (d) shows the cross-sectional morphology of the composite coating, and (c) shows the contact angle and sliding contact angle of the superhydrophobic surface. In (c), CA is the static contact angle and SA is the rolling contact angle. As can be seen from the figure, CA = 161.6° and SA = 4.8° of the superhydrophobic coating, indicating that the superhydrophobic coating has excellent hydrophobicity.

[0170] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

[0171] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a superhydrophobic polyimide-based anti-corrosion, anti-fouling, and self-cleaning coating, characterized in that, Includes the following steps: S1: The modifying agent and graphene oxide are added to organic solvent A, ultrasonically dispersed, and then refluxed to obtain modified graphene oxide; the modifying agent is at least one of POSS, chain alkylamine and chain alkyl isocyanate; the chain alkylamine and chain alkyl isocyanate have 7 to 18 carbon atoms in the chain alkyl alkyl group; S2: Under nitrogen protection, dianhydride monomers are added in batches to a mixed solution of diamine monomers and organic solvent B. After reaction, a polyamic acid solution is obtained. The polyamic acid solution is added to the modified graphene oxide and ultrasonically dispersed to obtain a composite underlayer slurry. The composite underlayer slurry is coated onto the surface of a substrate, dried, and then subjected to thermal imidization treatment to obtain a composite underlayer. The polyamic acid is POSS crosslinked polyamic acid. The modified graphene oxide accounts for 0.01%~1.50% of the mass of the polyamic acid solution. S3: A PU intermediate layer is coated on the surface of the composite bottom layer, and then a composite top layer slurry containing alkane siloxane or perfluorosiloxane modified SiO2 and a binder is coated. After drying, the superhydrophobic polyimide-based anti-corrosion, anti-fouling and self-cleaning coating is obtained; the alkane siloxane is dodecyl siloxane or hexadecyl siloxane. The POSS is one of monoamino oligosilsesquioxane, diamino oligosilsesquioxane, and octaamino oligosilsesquioxane.

2. The method for preparing a superhydrophobic polyimide-based anti-corrosion and anti-fouling self-cleaning coating according to claim 1, characterized in that, In step S1, the graphene oxide accounts for 2.5% to 6.5% of the mass of the modifying reagent.

3. The method for preparing a superhydrophobic polyimide-based anti-corrosion and anti-fouling self-cleaning coating according to claim 1, characterized in that, In step S2, the dianhydride monomer is a fluorinated dianhydride monomer and / or the diamine monomer is a fluorinated diamine monomer.

4. The method for preparing a superhydrophobic polyimide-based anti-corrosion and anti-fouling self-cleaning coating according to claim 1, characterized in that, In step S3, in the composite top layer slurry containing alkane-siloxane or perfluorosiloxane-modified SiO2 and binder, the alkane-siloxane or perfluorosiloxane-modified SiO2 accounts for 0.01% to 1.50% of the binder mass.

5. A superhydrophobic polyimide-based anti-corrosion, anti-fouling, and self-cleaning coating, characterized in that, The coating is prepared by the method described in any one of claims 1 to 4; the impedance value of the coating is (1.32~3.29)×10. 11 Ω•cm 2 The coating has a contact angle of 152°~159°, and its low-frequency impedance value is 7.04 × 10⁻⁶ after 50 days of neutral salt spray testing. 10 Ω•cm 2 .

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