Preparation method of modified graphene oxide polyurethane composite

Abstract

The present application relates to a kind of preparation methods of modified graphene oxide polyurethane composite, modified graphene oxide polyurethane composite prepared using the method and its application.The preparation method of the present application includes: graphene oxide is reacted with 4-(trifluoromethoxy) phenyl isocyanate to obtain modified graphene oxide;Toluene group-2,4-diisocyanate end-capped poly (propylene glycol), adipic acid dihydrazide is mixed with four hydrogen bond monomers, to obtain polyurethane base material;Modified graphene oxide is added to polyurethane base material and mixed uniformly, to prepare modified graphene oxide polyurethane material.By the method of the present application, functionalized graphene polymer composite anticorrosive material with self-repairing, strong mechanical properties can be prepared.The preparation method of the present application is simple, and the modified graphene oxide polyurethane composite prepared has higher self-repairing anticorrosive efficiency.

Description

Technical Field

[0001] This invention belongs to the field of polymer self-healing material preparation technology, and relates to a method for preparing modified graphene oxide polyurethane composite material, the modified graphene oxide polyurethane composite material prepared by this method, and its application. Background Technology

[0002] Inspired by nature, self-healing elastomers, capable of repairing themselves after damage, have been applied in fields such as construction, aerospace, and medicine. These elastomers exhibit excellent performance in mechanical shock environments, capable of sensing and repairing damage. Therefore, developing smart polymer materials with both passive and active self-healing capabilities has become a research hotspot. Initially, the self-healing concept was applied to organic coatings and organic / inorganic hybrid coatings, achieving self-repair through microcapsules and microtubule networks. The intrinsic self-healing mechanism is based on reversible covalent and non-covalent interactions, with hydrogen-bonded self-healing coatings showing the most promise.

[0003] Corrosion is the process by which metals transform into a stable chemical form. While unavoidable, it can be mitigated through methods such as corrosion-resistant materials, cathodic protection, corrosion inhibitors, and coatings. Traditional anti-corrosion coatings fail when equipment or machinery develops cracks due to internal or external forces. Self-healing anti-corrosion coatings, by adding self-healing materials to the coating, automatically repair cracks after damage, thereby extending the coating's lifespan and improving its anti-corrosion effect.

[0004] Self-healing anti-corrosion coatings are mainly divided into two types: exogenous and intrinsic. Exogenous self-healing anti-corrosion coatings achieve their self-healing and anti-corrosion properties by adding nanocapsules or microcapsules loaded with self-healing agents or preservatives (e.g., Chinese patent application CN202510128391.3) within the coating, releasing the healing agent to repair the coating upon damage. However, the amount of healing agent in the capsule is limited, and a large number of capsules can affect the barrier properties of the coating. Intrinsic self-healing anti-corrosion coatings achieve their self-healing and anti-corrosion properties based on reversible polymer networks, chemical bonds, chain mobility, molecular chain entanglement, or polymerization chemical or physical processes. They also possess the unique characteristic of being reusable, further improving the durability of the coating.

[0005] Intrinsic self-healing corrosion protection strategies achieve coating self-healing corrosion protection performance based on chemical or physical processes involving reversible polymer networks, chemical bonds, chain mobility, molecular chain entanglement, or polymerization. Compared to extrinsic self-healing corrosion protection materials, intrinsic self-healing materials, due to their unique self-healing mechanism, allow for repeated healing and further enhance coating durability. Research on intrinsic self-healing anticorrosive materials (Borisova D, Akçakayıran D, Schenderlein M, et al. Nanocontainer‐based anticorrosive coatings: effect of the container size on the self‐healing performance[J]. Advanced Functional Materials, 2013, 23(30):3799-3812) revealed that their main self-healing mechanism is achieved through the reversible connection of covalent and non-covalent bonds in the polymer. Among these, the reversible covalent bonds include Diels-Alder bonds (Yang S, Du X, Du Z, et al. Robust, stretchable and photothermal self-healing polyurethane elastomerbased on furan-modified polydopamine nanoparticles[J]. Polymer, 2020, 190:122219), acylhydrazone bonds, and disulfide bonds (Zheng X, Yang H, Sun Y, et al. A molecular dynamicssimulation on self-healing behavior based on disulfide bond exchange reactions[J]. Polymer, 2021, 212: 123111), borate ester bonds, silyl ether bonds, and hindered urea bonds, etc., while non-covalent reversible connections include hydrogen bonds (multiple hydrogen bonds) (Wang YJ, He Y, Zheng SY, et al. Polymer pressure‐sensitive adhesive with a temperature‐insensitive loss factor operating under water and oil[J].(References: Advanced Functional Materials, 2021, 31(48): 2104-296); metal-ligand coordination (Burnworth M, Tang L, Kumpfer JR, et al. Optically healable supramolecular polymers[J]. Nature, 2011, 472(7343): 334-337), etc.)

[0006] The primary self-healing mechanism of intrinsic self-healing anti-corrosion coatings is achieved through the reversible connection of covalent bonds (such as Diels-Alder bonds, acylhydrazone bonds, disulfide bonds, etc.) and non-covalent bonds (such as multiple hydrogen bonds, metal-ligand coordination bonds, etc.) in the polymer. However, the interaction factors of different chemical bonds (such as temperature, light, pH value, etc.) may prevent the material from self-healing at room temperature. Summary of the Invention

[0007] Technical issues

[0008] To address the problems of poor mechanical properties, demanding self-healing conditions, and poor corrosion resistance in existing self-healing materials, this invention provides a method for preparing a modified graphene oxide polyurethane composite material, the modified graphene oxide polyurethane composite material prepared by this method, and its application in metal corrosion protection. This invention can prepare a functional graphene polymer composite corrosion-resistant material with self-healing properties and strong mechanical properties. The preparation method of this invention is simple to operate, and the prepared modified graphene oxide polyurethane composite material exhibits high self-healing and corrosion-resistant efficiency.

[0009] Technical solution

[0010] This invention introduces modified graphene oxide into a multi-hydrogen bonded polymer to construct a self-healing intelligent anti-corrosion material. By integrating modified graphene oxide into a multi-hydrogen bonded polymer system, a polymer composite material with excellent mechanical properties is obtained. The effects of coating microstructure, load, and chemical medium on the dynamic healing law of the corrosion interface are studied, providing a theoretical basis for the corrosion mechanism of modified graphene oxide polymer composite anti-corrosion materials.

[0011] This invention provides a method for preparing a modified graphene oxide polyurethane composite material, the method comprising:

[0012] S1: Modified graphene oxide is obtained by reacting graphene oxide with 4-(trifluoromethoxy)phenyl isocyanate;

[0013] S2: Toluene-2,4-diisocyanate-terminated poly(propylene glycol), adipate dihydrazide and the tetrad hydrogen-bonded monomer shown in Formula I are mixed and reacted to obtain a polyurethane substrate;

[0014] (I)

[0015] S3: Add modified graphene oxide to a polyurethane substrate and mix evenly to obtain a modified graphene oxide polyurethane material.

[0016] Step S1

[0017] In this invention, "graphene oxide (GO)" refers to a complex compound formed by the oxidation of graphene, which has a large number of oxygen-containing groups on its surface and edges, such as carboxyl groups (-COOH), hydroxyl groups (-OH), or epoxy groups.

[0018] In step S1, the graphene oxide can be a commercially available product or can be prepared by known methods, such as those disclosed in CN103382028A, CN103496690A, CN106629673A, CN104291330B, Progress in the Preparation, Reduction and Application of Graphene Oxide [J], Journal of Infrared and Millimeter Waves, 2019, 38(1):79~90, but is not limited thereto.

[0019] In some embodiments, graphene oxide can be prepared as follows:

[0020] S1-1: Pre-oxidation of flake graphite by reacting it with phosphorus pentoxide and potassium persulfate in concentrated sulfuric acid;

[0021] S1-2: The pre-oxidized phosphorus flake graphite is mixed with sodium nitrate and potassium permanganate in concentrated sulfuric acid and reacted at 30-40℃. Then, deionized water is added and the reaction is carried out at 80-100℃ for further oxidation treatment to obtain graphene oxide.

[0022] In S1-1, concentrated sulfuric acid (H2SO4) refers to an aqueous solution of sulfuric acid with a mass concentration of approximately 98% or higher. The amount of concentrated sulfuric acid used is approximately 23-28 mL for 1 g of flake graphite. Within this range, the purpose of oxidizing graphite can be achieved.

[0023] In S1-1, potassium persulfate (K2S2O8) serves as the oxidant, phosphorus pentoxide (P2O5) as the intercalating agent or auxiliary oxidant, and concentrated sulfuric acid (H2SO4) as the reaction medium and intercalating agent. Based on 1 part by weight of flake graphite, the amount of potassium persulfate can be 1-1.20 parts by weight, preferably 1-1.10 parts by weight, particularly 1 part by weight; the amount of phosphorus pentoxide can be 1-1.60 parts by weight, preferably 1-1.30 parts by weight, particularly 1 part by weight. Within these ranges, the pre-oxidation process can be successfully achieved. If the amount of phosphorus pentoxide is too low, the intercalation effect will be poor, while if it is too high, the reaction system may become too viscous, making subsequent washing difficult. If the amount of potassium persulfate is too low, oxidation will be insufficient, and the graphite interlayers will be difficult to open effectively, resulting in poor performance of subsequent oxidation steps; while if it is too high, it may lead to over-oxidation, damaging the graphene sheet structure and generating more structural defects.

[0024] In S1-1, pre-oxidation can be carried out at 50-90℃, such as 55, 60, 65, 70, 75, 80, and 85℃, preferably at 80℃. Within this temperature range, the flake graphite framework can be moderately oxidized, introducing oxygen-containing functional groups (such as hydroxyl and epoxy groups), but the structure is not severely damaged. If the temperature is too low, the intercalating agent (P2O5) and oxidizing agent (K2S2O8) cannot be effectively embedded between the graphite layers; the oxidation reaction only occurs on the surface of the graphite particles, and the interior is not effectively affected. If the temperature is too high, the excessively rapid oxidation rate leads to too many structural defects on the graphene sheets, and may even cause the carbon framework to break, generating small molecule carbon oxides (CO2, CO), resulting in a decrease in yield and carbon loss.

[0025] In S1-1, pre-oxidation can be carried out for 4-8 hours. Within this reaction time range, a suitable amount and relatively uniformly distributed oxygen-containing functional groups can be introduced into the carbon framework, effectively expanding the interlayer spacing and perfectly preparing for the next reaction. If the reaction time is too short, the number of oxygen-containing functional groups (such as COC, C-OH) generated is small, and the graphite layers are not effectively "expanded". If the reaction time is too long, more structural defects will be generated on the graphene sheets, and even carbon-carbon bonds will break, resulting in a reduction in sheet size and severe fragmentation.

[0026] S1-1 may also include a post-processing step, in which the reaction solution is cooled after the pre-oxidation reaction, then solid-liquid separation is performed, and the pre-oxidized graphene is washed with deionized water.

[0027] In S1-2, the description of concentrated sulfuric acid is the same as that in S1-1.

[0028] In S1-2, potassium permanganate is the primary oxidant for the direct oxidation of graphite, while sodium nitrate is a non-toxic auxiliary agent used in the buffer reaction to generate nitrogen dioxide. Based on 1 part by weight of flake graphite, the amount of sodium nitrate can be 0.5-1.0 parts by weight, preferably 0.55-0.80 parts by weight, particularly 0.60 parts by weight, and the amount of potassium permanganate can be 2-5 parts by weight, preferably 2.5-4.0 parts by weight, particularly 3 parts by weight. Within these ranges, the oxidation reaction can proceed smoothly. If the amount of sodium nitrate is too low, it will lead to insufficient MnO3 generated in the initial stage of the reaction. + Insufficient active species result in slow reaction initiation, while excessive amounts make it difficult to completely remove residual sodium nitrate through washing, affecting the purity of graphene oxide. If the amount of potassium permanganate is too low, the prepared graphene oxide will have a high C / O ratio, poor hydrophilicity, and difficulty in peeling and dispersing in water. If the amount is too high, it will cause severe oxidation, leading to the breakage of the carbon skeleton and the generation of a large number of fragments and small molecule carbon oxides (CO2, CO).

[0029] In step S1-2, the pre-oxidized phosphorus flake graphite is dispersed in concentrated sulfuric acid at 0-5°C, for example, 1, 2, 3, or 4°C, preferably 0°C, and then sodium nitrate and potassium permanganate are added and mixed. Within the above temperature range, the reactants can be effectively fused. If the temperature is too low, the fusion of reactants is inhibited, while if it is too high, the reaction rate increases exponentially, generating a large amount of gas and heat instantaneously, which can easily cause an eruption.

[0030] In S1-2, the reaction is carried out at 30-40°C, for example 32, 35, 38°C, for 3-8 hours, for example 4 hours.

[0031] In S1-2, based on 1g of flake graphite, the amount of deionized water added can be 50-80mL, such as 60 or 70mL.

[0032] In step S1-2, after adding deionized water, the reaction is carried out at 80-100°C, preferably 95°C, for 20 to 60 minutes, especially 30 minutes. Within this temperature range, the main oxidation reaction can be achieved. If the temperature is too low, the oxidation reaction rate is too slow, requiring an extremely long reaction time, and oxidation may be incomplete. Conversely, if the temperature is too high, over-oxidation will occur, causing the carbon skeleton to break down and decompose in the form of CO2 and CO (carbon loss), resulting in a decrease in yield.

[0033] S1-2 may also include a post-processing step: after cooling, hydrogen peroxide is added to quench the reaction, followed by solid-liquid separation to obtain graphene oxide.

[0034] In step S1, the structure of 4-(trifluoromethoxy)phenylisocyanate (CAS Number: 35037-73-1) is as follows: .

[0035] The reaction between graphene oxide and 4-(trifluoromethoxy)phenyl isocyanate is mainly a reaction between the isocyanate group on 4-(trifluoromethoxy)phenyl isocyanate and the hydroxyl group on graphene oxide, as shown in the following reaction formula:

[0036]

[0037] Where R' represents the graphene oxide bulk and Ar represents the phenyl group.

[0038] Based on 1 part by weight of graphene oxide, the amount of 4-(trifluoromethoxy)phenyl isocyanate can be 2-6 parts by weight, preferably 5 parts by weight. Within this range, the trifluoromethoxyphenyl groups containing 4-(trifluoromethoxy)phenyl isocyanate can be covalently grafted onto the graphene oxide. The introduced trifluoromethoxyphenyl groups may help disperse the graphene oxide in the polymer matrix. If the amount of 4-(trifluoromethoxy)phenyl isocyanate is too high, unreacted isocyanate will remain, causing side reactions and forming a large amount of covalent crosslinks between or within GO sheets, leading to subsequent problems; while if the amount is too low, the modification will be incomplete.

[0039] The reaction between graphene oxide and 4-(trifluoromethoxy)phenyl isocyanate can be carried out in a solvent. The solvent is not particularly limited, as long as it does not affect the reaction. For example, dimethylformamide (DMF) can be used as the solvent.

[0040] The reaction can be carried out at 60-100°C, preferably 70-90°C, and especially 80°C. The reaction time can be more than 4 hours, more than 6 hours, for example 12 hours, but is not limited thereto.

[0041] Step S1 may also include a post-processing step, in which the obtained product is centrifuged and then freeze-dried to obtain modified graphene oxide.

[0042] Step S2

[0043] In step S2, the tetrad hydrogen bond monomer shown in Formula I can be a commercially available product or can be prepared by known methods, but is not limited thereto.

[0044] In some embodiments, guanidine carbonate and 2-acetyl-γ-butyrolactone are reacted to prepare the tetrahydrobonded monomer shown in Formula I, as shown in the following reaction formula;

[0045] .

[0046] The reaction can be carried out at 60-100°C, preferably 70-90°C, especially 80°C, and the reaction time can be more than 1 hour, more than 2 hours, for example 4 hours, but is not limited thereto.

[0047] The reaction can be carried out in the presence of a catalyst. Considering its moderate alkalinity, good solubility, easy post-treatment volatility, large steric hindrance to avoid side reactions, and economic efficiency, triethylamine was chosen as the catalyst.

[0048] Based on 1 mol of guanidine carbonate, the amount of 2-acetyl-γ-butyrolactone can be 1-1.20 mol, for example 1-1.10 mol, preferably 1.0 mol. Within this range, a high yield of the four-hydrogen-bonded monomer can be achieved with few byproducts. If the amount of 2-acetyl-γ-butyrolactone is insufficient, the reaction will be incomplete, and the two guanidine groups in the guanidine carbonate will not be fully utilized, leaving some unreacted guanidine groups as residues. Conversely, excess 2-acetyl-γ-butyrolactone may undergo a self-condensation reaction under alkaline conditions, producing byproducts.

[0049] In step S2, the tolylene-2,4-diisocyanate-terminated poly(propylene glycol) has the English name Poly(propylene glycol), CAS Number: 9057-91-4, a number-average molecular weight (Mn) of approximately 2,300, and an isocyanate content of approximately 3.6 wt.%, with the following structural formula: .

[0050] The structure of adipic acid dihydrazide (CAS Number: 1071-93-8) is as follows: .

[0051] In step S2, the isocyanate groups of the toluene-2,4-diisocyanate-terminated poly(propylene glycol) undergo an addition reaction with the amino groups of the adipic acid dihydrazide and the tetrad hydrogen-bonded monomer shown in Formula I to achieve chain extension. The schematic reaction formula is as follows:

[0052] .

[0053] Based on 1 mol of toluene-2,4-diisocyanate-terminated poly(propylene glycol), the amount of adipic acid dihydrazide can be 0.50-0.80 mol, preferably 0.60-0.80 mol, particularly 0.80 mol, and the amount of tetrahydrobonded monomer can be 0.20-0.50 mol, preferably 0.20-0.40 mol, particularly 0.20 mol. Within the above dosage range, a stable polyurethane material can be formed. If the amount of toluene-2,4-diisocyanate-terminated poly(propylene glycol) is too low, the flexible segment density is low, and the material is rigid and unsuitable as a coating material; if the amount is too high, the flexible segment density is high, and the material is in a gel state and unsuitable. If the amount of adipic acid dihydrazide is too low, the crosslinking density is low, and the material is in a gel state and unsuitable as a coating material; if the amount is too high, the crosslinking density is high, and the material is rigid and unsuitable as a coating material. If the amount of tetrahydrobonded monomer is too low, the amount of multiple hydrogen bonds introduced will be small, and the interaction between chains will be weak. If the amount is too high, the amount of multiple hydrogen bonds introduced will be large, and the interaction between chains will be strong, resulting in excessive hardness, which is not conducive to coating.

[0054] The reaction can be carried out at room temperature. The reaction time can be more than 4 hours, more than 6 hours, such as 12 hours, but is not limited to this.

[0055] Step S3

[0056] In step S3, the modified graphene oxide and polyurethane substrate are physically mixed evenly, so that the modified graphene oxide is stably dispersed in the polyurethane substrate.

[0057] Based on the weight of toluene-2,4-diisocyanate-terminated poly(propylene glycol) in step S2, the amount of modified graphene oxide can be 0.2-0.8 wt%, for example, 0.2 wt%, 0.5 wt%, 0.8 wt%, etc., preferably 0.2 wt%. Within the above-mentioned dosage range, the modified graphene oxide can be uniformly dispersed in the polymer matrix. If the dosage is too low, the modified graphene oxide cannot fully enhance the anti-corrosion ability of the coating, while if it is too high, insufficient dispersion in the polymer matrix will lead to anisotropic effects.

[0058] In some embodiments, the preparation method of the modified graphene oxide polyurethane composite material of the present invention includes the following steps:

[0059] Step 1: Pre-oxidized graphite is obtained by heating flake graphite with phosphorus pentoxide and potassium persulfate in concentrated sulfuric acid at 80°C for 5 hours.

[0060] Step 2: Stir the pre-oxidized graphite in concentrated sulfuric acid at 0°C for 0.5 hours, add sodium nitrate and potassium permanganate and mix, react at 35°C for 4 hours, then add deionized water and react at 95°C for 0.5 hours, then cool and add hydrogen peroxide to quench the reaction to obtain graphene oxide.

[0061] Step 3: Graphene oxide and 4-(trifluoromethoxy)phenyl isocyanate were reacted at 80°C for 12 hours under nitrogen protection to obtain modified graphene oxide;

[0062] Step 4: Guanidine carbonate and 2-acetyl-γ-butyrolactone are mixed and reacted at 80°C for 4 hours to obtain the tetrahydrobonded monomer shown in Formula I;

[0063] Step 5: Tolyl-2,4-diisocyanate-terminated poly(propylene glycol), adipate dihydrazide, and the tetrad hydrogen-bonded monomer shown in Formula I are reacted at 80°C for 12 hours under nitrogen protection to obtain a polyurethane substrate.

[0064] Step 6: Add modified graphene oxide to the polyurethane matrix and stir and mix at 80°C for 2 hours under nitrogen protection to obtain the modified graphene oxide polyurethane composite material.

[0065] In step one, relative to 1g of flake graphite, the amount of concentrated sulfuric acid used is 23-28mL, the amount of potassium persulfate used is 1g, and the amount of phosphorus pentoxide used is 1g.

[0066] In step two, relative to 1g of flake graphite, the amount of concentrated sulfuric acid used is 23-28mL, the amount of sodium nitrate used is 0.6g, and the amount of potassium permanganate used is 3g.

[0067] In step three, the amount of 4-(trifluoromethoxy)phenyl isocyanate is 5g relative to 1g of graphene oxide;

[0068] In step four, based on 1 mol of guanidine carbonate, the amount of 2-acetyl-γ-butyrolactone used is 1.0 mol;

[0069] In step five, based on 1 mol of toluene-2,4-diisocyanate-terminated poly(propylene glycol), the amount of adipate dihydrazide is 0.80 mol, and the amount of tetradehydrogenated monomer is 0.20 mol.

[0070] In step six, based on the weight of toluene-2,4-diisocyanate-terminated poly(propylene glycol) in step five, the amount of modified graphene oxide is 0.20-0.80 wt%.

[0071] A second aspect of the present invention provides a modified graphene oxide polyurethane composite material, which is prepared using the preparation method of the modified graphene oxide polyurethane composite material of the present invention.

[0072] The modified graphene oxide polyurethane composite material of the present invention has high self-healing and anti-corrosion performance and outstanding mechanical properties, and can be used as an anti-corrosion material to prepare anti-corrosion coatings.

[0073] A third aspect of the present invention provides the use of the modified graphene oxide polyurethane composite material of the present invention for preparing anti-corrosion coatings.

[0074] A fourth aspect of the present invention provides an article comprising a substrate and a coating on the substrate, said coating comprising a modified graphene oxide polyurethane composite material according to the present invention.

[0075] In one embodiment, the coating can be formed by coating the modified graphene oxide polyurethane material of the present invention onto a substrate. The substrate can be a metal sheet, such as a Q235 steel sheet.

[0076] Beneficial effects

[0077] This invention resolves the contradiction between the high mechanical strength and excellent self-healing properties of self-healing polyurethane, and studies its anti-corrosion performance as a metal protective coating.

[0078] The method of this invention can prepare composite materials with high self-healing and anti-corrosion properties as well as outstanding mechanical properties. Electrochemical test results show that the coating prepared using the modified graphene oxide polyurethane composite material of this invention significantly improves the corrosion resistance of the substrate, demonstrating a four-order-of-magnitude increase in impedance and a three-order-of-magnitude decrease in corrosion current density.

[0079] This invention prepares a smart polymer coating with excellent self-healing ability, mechanical properties, and good corrosion resistance. The chemical bond information and structural information of the novel polymer composite coating are systematically characterized, and the mechanical properties, long-term stability, corrosion resistance, and self-healing performance of the novel polymer composite coating are evaluated, providing a reliable solution for corrosion protection of material surfaces in complex environments. Attached Figure Description

[0080] Figure 1 The image shows a SEM image of the graphene oxide prepared in Preparation Example 1 of the present invention in Experimental Example 1.

[0081] Figure 2 This shows a TEM image of the graphene oxide prepared in Preparation Example 1 of the present invention in Experimental Example 1;

[0082] Figure 3 This demonstrates the toluene-2,4-diisocyanate-terminated poly(propylene glycol) (PPG-NCO) from Experimental Example 2, the tetrahydrobonded monomer (UPy) prepared in Preparation Example 2, and the PAU-GO prepared in Examples 1-3. 0.2 PAU-GO 0.5 and PAU-GO 0.8Infrared spectrum of PAU prepared in Comparative Example 1;

[0083] Figure 4 The results of the 1H NMR spectrum of the quadruple hydrogen-bonded monomer (UPy) prepared in Preparation Example 3 of the present invention are shown in Experimental Example 3.

[0084] Figure 5 In Experiment 4, the modified graphene oxide polyurethane composite material PAU-GO prepared in Example 1 of this invention was shown. 0.2 Thermogravimetric analysis results of PAU prepared in Comparative Example 1;

[0085] Figure 6 Experimental Example 5 shows PAU-GO coated with the material from Example 1 of this invention. 0.2 Electrochemical impedance spectroscopy results for the coated Q235 substrate and the bare Q235 substrate are shown, where (a) and (b) are the Nyquist and Bode plots of the bare Q235 substrate, respectively, and (c) and (d) are the results for the PAU-GO coated substrate. 0.2 Nyquist and Bode plots of the coated Q235 substrate;

[0086] Figure 7 The image shown is of Experimental Example 5, coated with PAU-GO prepared in the embodiments of the present invention. 0.8 PAU-GO 0.5 PAU-GO 0.2 Polarization curves of the coated Q235 substrate and the bare Q235 substrate;

[0087] Figure 8 Example 6 is an experimental example of the PAU-GO prepared in Example 2 of this invention. 0.5 The self-healing morphology of the scratch after 2 hours at room temperature. Detailed Implementation

[0088] To make the technical problem to be solved, the technical solution, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0089] The weights of the relevant components mentioned in the embodiments of this application can refer not only to the specific content of each component, but also to the proportional relationship between the weights of the components. Therefore, any scaling up or down of the content of the relevant components according to the embodiments of this application is within the scope disclosed in the embodiments of this application. Specifically, the mass mentioned in the embodiments of this application can be μg, mg, g, kg, and the volume can be μL, mL, L, or other units known in the field of biochemistry.

[0090] Materials and Instruments

[0091] Flake graphite: purchased from Aladdin, purity approximately 99% (product number: P196402), CAS number: 7782-42-5.

[0092] Phosphorus pentoxide: purchased from Aladdin, purity >99%; CAS No.: 1314-56-3.

[0093] Potassium persulfate: purchased from Aladdin, purity approximately 99%; CAS No.: 7727-21-1.

[0094] Concentrated sulfuric acid: purchased from Sinopharm Group, purity ≥95%; CAS No.: 7664-93-9.

[0095] Sodium nitrate: Purchased from Sinopharm Group, purity ≥99%; CAS No.: 7631-99-4.

[0096] Potassium permanganate: purchased from Sinopharm Group, purity ≥99.5%; CAS No.: 7722-64-7.

[0097] Tolyl-2,4-diisocyanate-terminated poly(propylene glycol): purchased from Maclean, Mn=2300g / mol; CAS No.: 9057-91-4.

[0098] Adipic acid dihydrazide: purchased from Maclean, Mn=174.2g / mol, purity approximately 98%; CAS No.: 1071-93-8.

[0099] SEM measurements were performed on a Hitachi Regulus 8220 cold field emission scanning electron microscope.

[0100] TEM measurements were performed using a ThermoFisher Scientific Talos F200X field emission transmission electron microscope.

[0101] Infrared spectra were measured on an IRTARCER-100 Fourier transform infrared spectrometer.

[0102] The proton NMR spectrum was measured on an Agilent 500 MHz NMR spectrometer in the United States.

[0103] Thermogravimetric analysis was performed on a STA 449F3-QMS 402D-IS50 thermal analyzer. Specific conditions were: temperature: 30-600℃, heating rate: 10℃ / min, nitrogen protection.

[0104] Electrochemical impedance was measured on a CS310MA electrochemical workstation.

[0105] The polarization curves were measured on a CS310MA electrochemical workstation.

[0106] Preparation Example 1: Preparation of Graphene Oxide

[0107] (1) Weigh 1g of flake graphite, 1g of phosphorus pentoxide and 1g of potassium persulfate respectively and add them to 25mL of concentrated sulfuric acid and stir for 30 minutes;

[0108] (2) Keep the mixture solution obtained in step (1) in an oil bath at 80°C for 5 hours;

[0109] (3) Add an appropriate amount of deionized water to a beaker, pour the above mixture into it, centrifuge, and then dry the solid mixture at 80°C for 10 hours to obtain pre-oxidized phosphorus flake graphite.

[0110] (4) Place the dried pre-oxidized flake graphite in 25 mL of concentrated sulfuric acid and stir in an ice-water bath for 30 minutes.

[0111] (5) Add 0.6g NaNO3, then slowly add 3g KMnO4 to the mixture and continue stirring until a dark green color appears;

[0112] (6) Transfer the above mixture to a 35°C water bath and stir for 4 hours;

[0113] (7) Add 60 mL of deionized water to the above mixture and transfer the mixture to a 95°C oil bath and react for 30 minutes;

[0114] (8) The mixture was then transferred to a 35°C water bath and H2O2 was added until the mixture turned yellow;

[0115] (9) Centrifuge at 2000 r / min for 5 min, take the supernatant, continue centrifuging at 8000 r / min for 10 min, take the precipitate and freeze-dry to obtain graphene oxide.

[0116] Preparation Example 2: Preparation of Modified Graphene Oxide

[0117] (1) Weigh 200 mg of graphene oxide from Preparation Example 1 and place it in a beaker containing 25 mL of DMF, and ultrasonically disperse for 30 minutes;

[0118] (2) Weigh 1g of 4-(trifluoromethoxy)phenyl isocyanate into a 250mL three-necked flask containing 25mL DMF, purge with nitrogen 3 times, and stir for 10 minutes.

[0119] (3) Pour the uniformly dispersed graphene oxide solution into a three-necked flask and react at 80°C for 12 hours under nitrogen protection.

[0120] (4) After the reaction is complete, the mixture is centrifuged to collect the precipitate, and the precipitate is freeze-dried to obtain modified graphene oxide.

[0121] Preparation Example 3: Preparation of tetrahydrobonded monomers

[0122] (1) Weigh 5.12 g of 2-acetyl-γ-butyrolactone (40 mmol) and place it in a three-necked flask equipped with a reflux condenser;

[0123] (2) Weigh 3.6g of guanidine carbonate (40mmol) into the three-necked flask and add 40mL of ethanol;

[0124] (3) Slowly add 11 mL of triethylamine to the above mixture, heat to 80 °C, and react for 4 hours;

[0125] (4) After the reaction is complete, the mixture is centrifuged to collect the precipitate, which is washed three times with 0.1 mol / L hydrochloric acid solution. Finally, the precipitate is dried under vacuum at 80°C to obtain the target four-fold hydrogen bond monomer, which is a white powder product.

[0126] Example 1: Preparation of modified graphene oxide polyurethane composite material and coating

[0127] (1) 2.300 g of toluene-2,4-diisocyanate-terminated poly(propylene glycol), 0.139 g of adipate dihydrazide, and 0.0338 g of the tetrad hydrogen-bonded monomer obtained in Preparation Example 3 (the molar ratio of toluene-2,4-diisocyanate-terminated poly(propylene glycol), adipate dihydrazide, and tetrad hydrogen-bonded monomer was about 1:0.8:0.2) were mixed in 30 mL of LDMF and reacted at 80 °C for 12 hours under nitrogen protection to obtain polyurethane material PAU.

[0128] (2) Add 0.2 wt% (the weight percentage of modified graphene oxide is based on the toluene-2,4-diisocyanate-terminated poly(propylene glycol) of the main monomer to the polyurethane material PAU obtained in step (1) to prepare the modified graphene oxide of Example 2, and stir and mix at 80°C for 2 hours to obtain the modified graphene oxide polyurethane composite material PAU-GO. 0.2 .

[0129] (3) The PAU-GO0.2 obtained in step (2) was dried in a drying oven at 80°C for 10 hours to obtain a molten product. This product was then coated onto a Q235 steel sheet and dried further until a coating was formed to obtain PAU-GO. 0.2 coating.

[0130] Example 2

[0131] Except for the amount of modified graphene oxide used in step (2) being 0.5 wt%, everything else was the same as in Example 1, and the modified graphene oxide polyurethane composite material PAU-GO was obtained. 0.5 And PAU-GO 0.5 coating.

[0132] Example 3

[0133] Except for the amount of modified graphene oxide used in step (2) being 0.8 wt%, everything else was the same as in Example 1, and the modified graphene oxide polyurethane composite material PAU-GO was obtained. 0.8 And PAU-GO 0.8 coating.

[0134] Comparative Example 1

[0135] Except for skipping step (2) and directly replacing PAU-GO with the polyurethane material PAU obtained in step (1) in step (3). 0.2 Except for the above, the process is the same as in Example 1, and polyurethane material PAU and PAU coating are obtained.

[0136] Experimental Example 1

[0137] The graphene oxide prepared in Example 1 was tested by scanning electrochemical microscopy and transmission electrochemical microscopy. The results are shown in [Figure 1]. Figure 1 , Figure 2 .

[0138] Figure 1 This is a SEM image of the prepared graphene oxide. (See image.) Figure 1 As shown, at a magnification of 8000x, graphene oxide can be clearly seen as a stacked sheet structure, exhibiting a typical wrinkled sheet-like structure with numerous rich wrinkles and layers on its surface. This structure endows the material with extremely high physical barrier properties, which is beneficial for improving its corrosion resistance.

[0139] Figure 2 The TEM image of the prepared graphene oxide was obtained under a 500,000x transmission electron microscope (TEM). Figure 2 The graphene oxide sheets, with few or even single layers, can be clearly observed. These sheets are transparent, flexible, and thin-film-like, with slight curling at the edges. The electron beam can easily penetrate the ultrathin sheets, further confirming their extremely thin nature.

[0140] Experimental Example 2: Infrared Chromatography

[0141] p-Tolyl-2,4-diisocyanate-terminated poly(propylene glycol) (PPG-NCO), the tetrad hydrogen-bonded monomer (UPy) prepared in Example 2, and PAU-GO prepared in Examples 1-3 0.2 PAU-GO 0.5 and PAU-GO 0.8 Infrared spectroscopy was performed on the PAU prepared in Comparative Example 1, and the results are shown in the figure. Figure 3 .

[0142] like Figure 3As shown, the red curve represents the stretching vibration peak of the quadruple hydrogen-bonded monomer (UPy)-CH2- group, which appears at 2944 cm⁻¹. -1 At 2270 cm -1 The peak at 1689 cm⁻¹ belongs to the -NCO group. -1 and 1658 cm -1 The peaks at 1583 cm⁻¹ represent the adsorption peaks of CO groups on the pyrimidine ring and CO groups on the straight chain, respectively. -1 and 1525 cm -1 The peaks at 1260 cm⁻¹ represent the adsorption peaks of the NH groups on the pyrimidine ring and the NH groups on the straight chain, respectively. -1 The peak value at that point is caused by the stretching vibration of the CN group.

[0143] Polyurethane composites with different amounts of modified graphene oxide and PAU of Comparative Example 1 at 2270 cm⁻¹ -1 The disappearance of the isocyanate-NCO stretching vibration peak and the appearance of the characteristic peaks of NH stretching vibration and COC asymmetric stretching vibration fully demonstrate the synthesis of polyurethane.

[0144] Experimental Example 3: Proton NMR Spectroscopy

[0145] The 1H NMR spectrum of the quadruple hydrogen-bonded monomer (UPy) prepared in Preparation Example 3 was measured, and the results are shown in [Figure number missing]. Figure 4 The hydrogen bond positions of each monomer group are as follows: 1 ¹H-NMR (400 MHz, DMSO-d) δ 10.92 (S, 1H, NH), 6.38 (S, 2H, NH), 4.52 (t, J = 5.5 Hz, 1H, OH), 3.35 (t, 2H, CH₂), 2.43 (t, 2H, CH₂), 2.05 (S, 3H, CH₃). The above spectroscopic analysis indicates that the preparation of UPY was successful.

[0146] Experimental Example 4: Thermogravimetric Analysis

[0147] PAU-GO prepared in Example 1 0.2 Thermogravimetric analysis was performed on the PAU prepared in Comparative Example 1, and the results are shown in the figure. Figure 5 .

[0148] The modified graphene oxide polyurethane composite material samples prepared by this invention exhibit minimal and almost negligible mass loss at temperatures below 200°C; the small initial mass loss from 200°C to 400°C is mainly due to the decomposition of quadruple hydrogen bond groups, with the polyurethane backbone starting to decompose at approximately 400°C, indicating that the modified graphene oxide polyurethane composite material of this invention has excellent thermal stability.

[0149] Experiment Example 5: Corrosion Resistance Test

[0150] For bare Q235 substrates and those coated with PAU-GO 0.2 Electrochemical impedance spectroscopy (EIS) and polarization curve analysis (Tafel) were performed on the Q235 substrate of the material to determine the corrosion protection effect of the polymer composite material on the Q235 substrate. The results are shown in [Figure number missing]. Figure 6 , Figure 7 .

[0151] The test employed a three-electrode system consisting of a working electrode (Q235 steel coating), a counter electrode (a platinum sheet measuring 15×15×mm), and a reference electrode (a saturated calomel electrode). Each sample was immersed in a 3.5wt% NaCl solution for 10 days to evaluate its long-term corrosion resistance, and three parallel samples were used to ensure good reproducibility.

[0152] Figure 6 In the image, (a) and (b) are the Nyquist and Bode plots of the bare Q235 substrate, respectively, and (c) and (d) are the PAU-GO coated substrates. 0.2 Nyquist and Bode plots of the coated Q235 substrate. (From...) Figure 6 The results show that when the frequency is 0.01Hz, the coating of PAU-GO... 0.2 The impedance of the coated Q235 substrate is twice that of the bare Q235 substrate.

[0153] Figure 7 The middle layer is bare Q235 coated with PAU-GO. 0.8 PAU-GO 0.5 Or PAU-GO 0.2 Polarization curves of the coated Q235 substrate. Figure 7 The results showed that PAU-GO coating 0.8 PAU-GO 0.5 Or PAU-GO 0.2 The corrosion potential of the coated Q235 substrate shifted positively by about 600mV compared to the bare Q235 substrate, which fully demonstrates the corrosion resistance of the coating material.

[0154] Experiment Example 6: Self-Healing Performance Test

[0155] The modified graphene oxide polyurethane composite material PAU-GO prepared in Example 2 of this invention 0.5 Self-healing performance was tested by making a 70-micrometer-wide scratch on the coating surface using a scalpel. The scratch was then observed under an optical microscope, revealing that the scratch significantly healed within 2 hours. The results showed... Figure 8 middle.

[0156] The scratch test conducted on the coating above shows that the coating material of the present invention can self-repair within 2 hours at room temperature after being damaged.

Claims

1. A method for preparing a modified graphene oxide polyurethane composite material, characterized in that, The preparation method includes: S1: Modified graphene oxide is obtained by reacting graphene oxide with 4-(trifluoromethoxy)phenyl isocyanate; wherein, based on 1 part by weight of graphene oxide, the amount of 4-(trifluoromethoxy)phenyl isocyanate is 2-6 parts by weight; the reaction is carried out at a temperature of 60-100℃ for a reaction time of more than 4 hours. S2: Toluene-2,4-diisocyanate-terminated poly(propylene glycol), adipate dihydrazide and the tetrad hydrogen-bonded monomer shown in Formula I are mixed and reacted to obtain a polyurethane substrate; （I） Among them, based on 1 mol of toluene-2,4-diisocyanate-terminated poly(propylene glycol), the amount of adipate dihydrazide is 0.50-0.80 mol, and the amount of tetrad hydrogen bond monomer is 0.20-0.50 mol; S3: Add modified graphene oxide to the polyurethane substrate and mix evenly to obtain modified graphene oxide polyurethane material. The amount of modified graphene oxide is 0.2-0.8 wt% based on the weight of toluene-2,4-diisocyanate-terminated poly(propylene glycol) in step S2.

2. The preparation method according to claim 1, characterized in that, In step S1, graphene oxide is prepared as follows: S1-1: Pre-oxidation of flake graphite by reacting it with phosphorus pentoxide and potassium persulfate in concentrated sulfuric acid; S1-2: The pre-oxidized phosphorus flake graphite is mixed with sodium nitrate and potassium permanganate in concentrated sulfuric acid and reacted at 30-40℃. Then, deionized water is added and the reaction is carried out at 80-100℃ for further oxidation treatment to obtain graphene oxide.

3. The preparation method according to claim 2, characterized in that, In S1-1, the amount of concentrated sulfuric acid used is 23-28 mL relative to 1 g of flake graphite; the amount of potassium persulfate used is 1-1.20 parts by weight and the amount of phosphorus pentoxide used is 1-1.60 parts by weight based on 1 part by weight of flake graphite; the pre-oxidation is carried out at 50-90℃ for 4-8 hours. In S1-2, based on 1 part by weight of flake graphite, the amount of sodium nitrate is 0.5-1.0 parts by weight, and the amount of potassium permanganate is 2-5 parts by weight; the pre-oxidized flake graphite is dispersed in concentrated sulfuric acid at 0-5℃, and then sodium nitrate and potassium permanganate are added and mixed; the reaction is carried out at 30-40℃ for 3-8 hours; based on 1g of flake graphite, the amount of deionized water added is 50-80mL; the reaction is carried out at 80-100℃ for 20 to 60 minutes.

4. The preparation method according to claim 1, characterized in that, In step S1, Based on 1 part by weight of graphene oxide, the amount of 4-(trifluoromethoxy)phenyl isocyanate is 5 parts by weight. The reaction is carried out at a temperature of 70-90℃. The reaction time is more than 6 hours.

5. The preparation method according to claim 1, characterized in that, In step S2, the tetrahydrobonded monomer is prepared by reacting guanidine carbonate with 2-acetyl-γ-butyrolactone, as shown in the following reaction formula; ； Based on 1 mol of guanidine carbonate, the amount of 2-acetyl-γ-butyrolactone used is 1-1.20 mol.

6. The preparation method according to claim 1, characterized in that, Includes the following steps: Step 1: Pre-oxidized graphite is obtained by heating flake graphite with phosphorus pentoxide and potassium persulfate in concentrated sulfuric acid at 80°C for 5 hours. Step 2: Stir the pre-oxidized graphite in concentrated sulfuric acid at 0°C for 0.5 hours, add sodium nitrate and potassium permanganate and mix, react at 35°C for 4 hours, then add deionized water and react at 95°C for 0.5 hours, then cool and add hydrogen peroxide to quench the reaction to obtain graphene oxide. Step 3: Graphene oxide and 4-(trifluoromethoxy)phenyl isocyanate were reacted at 80°C for 12 hours under nitrogen protection to obtain modified graphene oxide. Step 4: Guanidine carbonate and 2-acetyl-γ-butyrolactone are mixed and reacted at 80°C for 4 hours to obtain the tetrahydrobonded monomer shown in Formula I; Step 5: Tolyl-2,4-diisocyanate-terminated poly(propylene glycol), adipate dihydrazide, and the tetrad hydrogen-bonded monomer shown in Formula I are reacted at 80°C for 12 hours under nitrogen protection to obtain a polyurethane substrate. Step 6: Add modified graphene oxide to the polyurethane substrate and stir at 80°C for 2 hours to obtain the modified graphene oxide polyurethane composite material.

7. The preparation method according to claim 6, characterized in that, In step one, relative to 1g of flake graphite, the amount of concentrated sulfuric acid used is 23-28mL, the amount of potassium persulfate used is 1g, and the amount of phosphorus pentoxide used is 1g. In step two, relative to 1g of flake graphite, the amount of concentrated sulfuric acid used is 23-28mL, the amount of sodium nitrate used is 0.6g, and the amount of potassium permanganate used is 3g. In step three, the amount of 4-(trifluoromethoxy)phenyl isocyanate is 5g relative to 1g of graphene oxide; In step four, based on 1 mol of guanidine carbonate, the amount of 2-acetyl-γ-butyrolactone used is 1.0 mol; In step five, based on 1 mol of toluene-2,4-diisocyanate-terminated poly(propylene glycol), the amount of adipate dihydrazide is 0.80 mol, and the amount of tetradehydrogenated monomer is 0.20 mol. In step six, based on the weight of toluene-2,4-diisocyanate-terminated poly(propylene glycol) in step five, the amount of modified graphene oxide is 0.20-0.80 wt%.

8. A modified graphene oxide polyurethane composite material, characterized in that, Prepared using the preparation method according to any one of claims 1-7.

9. The use of the modified graphene oxide polyurethane composite material of claim 8 for preparing an anti-corrosion coating.

10. An article comprising a substrate and a coating on the substrate, characterized in that, The coating comprises the modified graphene oxide polyurethane composite material as described in claim 9.

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