Preparation method of waterproof marine plywood

Abstract

The invention provides a preparation method of waterproof marine plywood, and belongs to the technical field of marine paints.The preparation method comprises the following steps that S1, fluorinated MXene is added into a solvent, ultrasonic dispersion is conducted, and dispersion liquid is obtained; step S2, adding cardanol glycidyl ether, bisphenol A epoxy resin, a rheological additive, a dispersant and the dispersion liquid obtained in the step S1 into a high-speed dispersion machine, carrying out high-speed shearing dispersion, then switching to low-speed stirring, adding epoxy modified polysiloxane, and uniformly stirring to obtain a waterproof coating; and S3, the plywood is pretreated, the waterproof coating obtained in the step S2 and a curing agent citric acid solution are evenly mixed, the surface of the plywood is coated with the mixture, and the plywood for the waterproof ship is obtained through flash drying layering and stepped curing. By constructing a self-assembly system based on surface energy gradient, a gradient structure with high bottom adhesion and super-hydrophobic surface is formed through single coating, the construction efficiency is greatly improved, and the problem of interlayer stripping of traditional multi-layer coating is thoroughly solved.

Description

Technical Field

[0001] This invention belongs to the field of marine coating technology, specifically relating to a method for preparing waterproof marine plywood. Background Technology

[0002] Marine plywood is an important structural material used in ship decks, cabin interiors, and marine engineering, widely applied due to its high strength-to-weight ratio and ease of processing. Besides basic load-bearing capacity, marine plywood must also withstand the high humidity, high salinity, strong ultraviolet radiation, and corrosion from marine organisms in the marine environment. Surface coating protection is a key means of isolating the plywood from the external environment and extending its service life. High-performance coatings, in particular, with environmental adaptability and long-term protective functions, are of great significance for ensuring the structural safety of ships.

[0003] Currently, the protective technology for marine plywood mainly involves two aspects: coating processes and material systems. In terms of coating processes, a multi-layer composite system of "primer-intermediate coat-topcoat" is primarily used. While this system achieves functional complementarity through the superposition of different coatings, the construction process is cumbersome, requiring strict control of recoating intervals between layers, and the interfaces are prone to delamination due to stress concentration or mismatched curing. In terms of material systems, they are mainly divided into rigid thermosetting resins and antifouling materials. Rigid materials, represented by bisphenol A epoxy resin, although possessing high hardness and strong barrier properties, cannot adapt to the stress relaxation caused by the significant hygroscopic expansion and shrinkage characteristics of wood under alternating wet and dry conditions. This makes them highly susceptible to micro-cracks, leading to moisture intrusion and substrate rot. Environmentally friendly antifouling materials, represented by silicone, while possessing low surface energy and effectively inhibiting biofouling, have poor wettability and adhesion to hydrophilic wood surfaces, making them unsuitable for direct use as single-layer coatings.

[0004] To achieve both effective penetration and anchoring of the wood coating and surface antifouling and hydrophobicity, existing technologies attempt to address this through physical blending or improved multilayer processes. However, simple physical blending struggles to achieve an ordered distribution of functional components along the thickness direction, while multilayer processes fail to solve the problems of interlayer failure and low construction efficiency. Therefore, developing a preparation method that can achieve internal layered assembly of the coating in a single application, adapting to wood deformation to prevent cracking while providing highly efficient surface antifouling, is a pressing technical problem that needs to be solved. Summary of the Invention

[0005] In view of the above situation and to overcome the defects of the prior art, the purpose of this invention is to provide a method for preparing waterproof marine plywood, so as to at least partially solve the problems mentioned in the background art.

[0006] The technical solution adopted in this invention is as follows: This invention proposes a method for preparing waterproof marine plywood, comprising the following steps: Step S1: Add fluorinated MXene to the solvent and disperse it by ultrasonication to obtain a dispersion; Step S2: In a high-speed disperser, add cashew phenol glycidyl ether, bisphenol A epoxy resin, rheology modifier, dispersant and the dispersion obtained in step S1, and perform high-speed shear dispersion. Then switch to low-speed stirring, add epoxy-modified polysiloxane, and stir evenly to obtain a waterproof coating. Step S3: Pre-treat the plywood by mixing the waterproof coating obtained in step S2 with the curing agent citric acid solution evenly, applying it to the surface of the plywood, and then flash-drying and layering and step-curing to obtain waterproof marine plywood.

[0007] In some embodiments of the present invention, the waterproof coating comprises, by weight: 60-80 parts of cashew phenol glycidyl ether, 10-20 parts of bisphenol A epoxy resin, 5-15 parts of epoxy-modified polysiloxane, 0.5-3 parts of fluorinated MXene, 1-4 parts of rheology modifier, 0.1-1 parts of dispersant, and 30-50 parts of solvent.

[0008] In some embodiments of the present invention, the solvent is a mixed solvent comprising xylene, propylene glycol methyl ether acetate and n-butanol in a mass ratio of (4-6):(3-5):(0.5-1.5); and the rheology modifier is hydrophobically modified fumed silica.

[0009] In some embodiments of the present invention, step S1, the method for preparing fluorinated MXene includes the following steps: Step S101: Add Ti3AlC2 powder to a mixed solution containing LiF and hydrochloric acid, stir and react at 30-40℃ for 20-25 hours, centrifuge and wash until neutral, and ultrasonically exfoliate to obtain Ti3C2T. x Nanosheet dispersion; Step S102: Add a certain amount of Ti3C2T to the dispersion. x Perfluorooctyltriethoxysilane (1.5-2 wt% by weight of nanosheets) was added, the pH was adjusted to acidic, and the mixture was refluxed and stirred at 60-65°C for 12 hours. After washing and drying, the fluorinated MXene was obtained.

[0010] In some embodiments of the present invention, in step S2, the high-speed shear dispersion speed is 1800-2200 rpm and the dispersion time is 15-25 minutes; the low-speed stirring speed is 200-600 rpm and the stirring time is 5-15 minutes.

[0011] In some embodiments of the present invention, in step S3, the curing agent citric acid solution is an ethanol solution of citric acid with a mass concentration of 40-60%; the mixing ratio of the waterproof coating and the curing agent citric acid solution is measured according to a molar ratio of carboxyl groups to epoxy groups of (0.9-1.1):1.

[0012] In some embodiments of the present invention, step S3, the plywood pretreatment step includes: selecting marine plywood with a moisture content of less than 6%, sanding the surface with 180-240 grit sandpaper along the grain, removing dust with compressed air, and wiping the surface with acetone for degreasing treatment.

[0013] In some embodiments of the present invention, the coating is performed by high-pressure airless spraying, and the wet film thickness of the coating is controlled to be 250-300 μm.

[0014] In some embodiments of the present invention, the specific process conditions for the flash drying and layering in step S3 are as follows: after coating, the coating is left to stand for 30-45 minutes in a windless environment at a temperature of 20-30°C.

[0015] In some embodiments of the present invention, step S3 includes a first curing stage and a second curing stage: the first curing stage is heating at 75-85°C for 1.5-2.5 hours; the second curing stage is heating at 130-150°C for 0.5-1.5 hours.

[0016] The beneficial effects achieved by this invention are as follows: This invention constructs a self-assembly system based on surface energy gradients, achieving a gradient structure with high adhesion at the bottom and superhydrophobic surface in a single coating application. This significantly improves construction efficiency and completely solves the interlayer delamination problem of traditional multi-layer coatings. The polymeric dynamic network constructed by combining the base resin and citric acid endows the coating with excellent stress relaxation capabilities, effectively overcoming the cracking problem caused by wood expansion and contraction due to moisture. Furthermore, utilizing the photothermal effect and superhydrophobic properties of fluorinated MXene, a synergistic effect of physical barrier and active sterilization is achieved. This method successfully integrates structural adaptability, dynamic repair, and green antifouling functions, significantly improving the service life and reliability of marine plywood in marine environments. Attached Figure Description

[0017] Figure 1 This is a flowchart illustrating the preparation method of waterproof marine plywood according to an embodiment of the present invention.

[0018] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof. Detailed Implementation

[0019] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those familiar to those skilled in the art. Furthermore, any methods and materials similar to or equivalent to those described herein may be applied to this invention. The preferred embodiments and materials described herein are for illustrative purposes only and do not limit the scope of this application.

[0021] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0022] Reference Figure 1 To address the problems raised in the background art, this invention provides a method for preparing waterproof marine plywood, comprising the following steps: Step S1: Add fluorinated MXene to the solvent and disperse it by ultrasonication to obtain a dispersion; Step S2: In a high-speed disperser, add cashew phenol glycidyl ether, bisphenol A epoxy resin, rheology modifier, dispersant and the dispersion obtained in step S1, and perform high-speed shear dispersion. Then switch to low-speed stirring, add epoxy-modified polysiloxane, and stir evenly to obtain a waterproof coating. Step S3: Pre-treat the plywood by mixing the waterproof coating obtained in step S2 with the curing agent citric acid solution evenly, applying it to the surface of the plywood, and then flash-drying and layering and step-curing to obtain waterproof marine plywood.

[0023] First, this invention lays the foundation for achieving structural self-assembly in a single coating application by constructing a thermodynamically unstable system based on surface energy gradients. Fluorinated MXene modified with perfluorooctyltriethoxysilane and epoxy-modified polysiloxane serve as key low-surface-energy components, exhibiting significantly lower surface tensions than the base resins, cashew phenol glycidyl ether and bisphenol A epoxy resin. This significant thermodynamic potential energy difference drives the flash-drying delamination in step S3, allowing the low-energy components to spontaneously overcome viscosity resistance and migrate to the gas-liquid interface during solvent evaporation, while the highly polar epoxy resin preferentially wets the hydrophilic wood substrate. This design achieves a gradient distribution of high adhesion at the bottom and superhydrophobic surface without increasing the number of application steps, solving the technical problem of traditional marine coatings requiring multiple coats and prone to interlayer adhesion failure.

[0024] Secondly, the resin curing system designed in this invention constitutes a catalyst-free dynamic covalent network of polymers based on an ester exchange mechanism. Specifically, citric acid has a unique "tricarboxyl-monohydroxy" structure. On the one hand, its carboxyl group (-COOH) undergoes a ring-opening esterification reaction with the epoxy groups in the matrix resin (including cashew phenol glycidyl ether, bisphenol A epoxy resin, and epoxy-modified polysiloxane), constructing a dense cross-linked network and generating a large number of β-hydroxy ester bonds. On the other hand, the tertiary hydroxyl group inherent in the citric acid molecule and the side hydroxyl groups generated in the reaction together constitute an internal catalytic system. When marine plywood experiences interfacial stress due to the expansion and contraction of moisture in the marine environment or is heated (e.g., by sunlight), the active free hydroxyl groups (R3-OH) in the system attack the ester bonds (R1-COO-R2) in the cross-linked network, initiating a thermally activated ester exchange reaction.

[0025] This reaction enables the polymer network to rearrange its microstructure while maintaining the total crosslinking density (total number of chemical bonds). This gives the solid coating liquid-like rheological behavior to relax interfacial stress and provides self-healing crack capability, solving the problem of cracking caused by the brittleness of traditional rigid epoxy coatings.

[0026] Furthermore, this invention utilizes a process control combining flash-drying layering and step-by-step curing to create a structure that combines a dense surface barrier with a firmly anchored underlying layer. The first step, room-temperature flash-drying, induces phase separation and component migration using a solvent evaporation gradient, enriching the outermost layer with fluorinated MXene. The second step, step-by-step curing, first fixes the layered structure through medium-temperature gelation, then activates dynamic bond exchange at high temperature to perfect dense cross-linking. This process results in a dense physical barrier layer composed of fluorinated MXene nanosheets on the surface of the plywood prepared by this invention, significantly improving waterproof performance. Simultaneously, the underlying epoxy resin, through its polar groups, forms a relatively strong chemical anchor and mechanical interlock with the wood fibers.

[0027] Furthermore, the fluorinated MXene component introduced in this invention endows the coating with the ability to actively defend against biofouling. The fluorinated MXene enriched on the surface not only constructs a superhydrophobic surface to inhibit initial biofouling, but its excellent photothermal conversion properties also generate localized thermal shock under sunlight irradiation, disrupting the protein structure of attached microorganisms. This synergistic effect of physical barrier and photothermal sterilization enables the coating to achieve long-lasting, green antifouling without relying on the release of toxic heavy metals.

[0028] In summary, this invention, by constructing a self-assembly system based on surface energy gradients, achieves a gradient structure with high adhesion at the bottom and superhydrophobic surface in a single coating application, significantly improving construction efficiency and completely solving the interlayer delamination problem of traditional multi-layer coatings. The polymeric dynamic network constructed by combining the matrix resin and citric acid endows the coating with excellent stress relaxation capabilities, effectively overcoming the cracking problem caused by wood expansion and contraction due to moisture. Furthermore, utilizing the photothermal effect and superhydrophobic properties of fluorinated MXene, a synergistic effect of physical barrier and active sterilization is achieved. This method successfully integrates structural adaptability, dynamic repair, and green antifouling functions, significantly improving the service life and reliability of marine plywood in marine environments.

[0029] In some embodiments, the waterproof coating comprises, by weight, 60-80 parts of cashew phenol glycidyl ether, 10-20 parts of bisphenol A epoxy resin, 5-15 parts of epoxy-modified polysiloxane, 0.5-3 parts of fluorinated MXene, 1-4 parts of rheology modifier, 0.1-1 parts of dispersant, and 30-50 parts of solvent. The 60-80 parts of cashew phenol glycidyl ether, as the main component, utilizes its long aliphatic side chains to impart excellent internal plasticizing effect to the coating, enabling it to adapt to the deformation of wood. Combined with 10-20 parts of bisphenol A epoxy resin, it effectively compensates for the insufficient rigidity of pure bio-based resins, improving the hardness and crosslinking density of the coating. Simultaneously, the ratio of 5-15 parts of epoxy-modified polysiloxane to 0.5-3 parts of fluorinated MXene ensures sufficient low surface energy components migrate to the surface to form a continuous and dense superhydrophobic photothermal layer, while avoiding agglomeration or interface defects caused by excessive filler. Furthermore, the appropriate amount of rheology modifier precisely controls the thixotropy of the system, preventing excessive penetration of the coating into the porous plywood and ensuring an effective wet film thickness for layered assembly. Additionally, epoxy-modified polysiloxanes refer to polysiloxanes with reactive epoxy groups. Their main chain contains a polysiloxane structure, exhibiting weather resistance and low surface energy, while also containing epoxy functional groups that can participate in the curing reaction.

[0030] In some embodiments, the solvent is a mixed solvent comprising xylene, propylene glycol methyl ether acetate, and n-butanol in a mass ratio of (4-6):(3-5):(0.5-1.5); the rheology modifier is hydrophobically modified fumed silica. Xylene, as a fast-evaporating solvent, preferentially escapes, rapidly increasing the system viscosity and inducing thermodynamic phase separation; while propylene glycol methyl ether acetate (PMA), as a slow-evaporating solvent, prolongs the liquid phase existence time, providing sufficient time and carrier for the migration of low surface energy components to the surface; n-butanol, as a co-solvent, improves the homogeneous stability of the initial system. This solvent gradient design further drives the coating to achieve automatic layering. Simultaneously, the selected hydrophobically modified fumed silica can construct a physical network when the coating is stationary, effectively preventing excessive penetration of the coating into the deep layers of the wood, ensuring sufficient wet film thickness on the substrate surface for layered assembly, thereby improving the integrity and functionality of the final superhydrophobic surface structure.

[0031] In some embodiments, the method for preparing fluorinated MXene in step S1 includes the following steps: Step S101: Add Ti3AlC2 powder to a mixed solution containing LiF and hydrochloric acid, stir and react at 30-40℃ for 20-25 hours, centrifuge and wash until neutral, and ultrasonically exfoliate to obtain Ti3C2T. x Nanosheet dispersion; Step S102: Add a certain amount of Ti3C2T to the dispersion. x Perfluorooctyltriethoxysilane (1.5-2 wt% by weight) was added to nanosheets, the pH was adjusted to acidic, and the mixture was refluxed and stirred at 60-65°C for 12 hours. After washing and drying, fluorinated MXene was obtained.

[0032] Through chemical modification with perfluorooctyltriethoxysilane, long fluorocarbon chains with low surface energy were successfully grafted onto the surface of MXene. On the one hand, the extremely low surface tension of the fluorocarbon chains can be used to provide a thermodynamic driving force for the migration of fluorinated MXene fillers from the resin matrix to the gas-liquid interface, thereby achieving self-layering of the coating. On the other hand, the Ti-O-Si covalent bonds formed can be used to achieve a stable bond, prevent the functional layer from falling off, and improve the hydrophobicity and anti-bioadhesion ability of the coating.

[0033] In some embodiments, in step S2, the high-speed shear dispersion is performed at a rotation speed of 1800-2200 rpm for 15-25 minutes; the low-speed stirring is performed at a rotation speed of 200-600 rpm for 5-15 minutes. Firstly, the high-speed shearing in the first stage (1800-2200 rpm) effectively breaks up the physical agglomeration of fluorinated MXene nanosheets, achieving uniform dispersion in the epoxy resin matrix. Secondly, switching to low-speed stirring (200-600 rpm) in the second stage avoids over-emulsification after introducing the layered component, epoxy-modified polysiloxane.

[0034] In some embodiments, in step S3, the curing agent citric acid solution is an ethanol solution of citric acid with a mass concentration of 40-60%; the mixing ratio of the waterproof coating and the curing agent citric acid solution is measured according to a molar ratio of carboxyl groups to epoxy groups of (0.9-1.1):1. Pre-dissolving solid citric acid in a high-concentration ethanol solution can promote uniform mixing of the curing agent in the resin and improve the integrity of the coating film. Secondly, the molar ratio of (0.9-1.1):1 is calculated based on the epoxy equivalent of the base resin and the carboxyl equivalent of citric acid. By controlling the carboxyl group to epoxy group ratio to (0.9-1.1):1, the base resin can undergo complete ring-opening esterification, eliminating residual hydrophilic carboxyl groups, ensuring excellent water resistance of the coating in marine environments, and providing sufficient dynamic exchange density to accommodate the deformation of the plywood and prevent coating cracking.

[0035] In some embodiments, step S3, the plywood pretreatment step includes: selecting marine plywood with a moisture content of less than 6%, sanding the surface with 180-240 grit sandpaper along the grain, removing dust with compressed air, and then wiping the surface with acetone for degreasing. Acetone effectively dissolves and removes natural extracts (such as resins, tannins, or teak oil) from the wood surface, eliminating the inhibitory effect of these substances on epoxy resin curing, preventing defects such as pinholes or incomplete drying of the coating, and ensuring the stability of the chemical bond.

[0036] In some embodiments, high-pressure airless spraying is employed for coating, controlling the wet film thickness of the coating to be 250-300 μm. High-pressure airless spraying technology can adapt to the viscosity characteristics of high-solids systems, rapidly forming a uniform, continuous, and dense liquid film on rough plywood surfaces, significantly improving construction efficiency. Furthermore, the 250-300 μm thickness, on the one hand, delays the instantaneous evaporation of the solvent, providing sufficient vertical migration paths and time windows for low surface energy components. On the other hand, due to the porous and absorbent nature of wood, this thickness compensates for some of the loss caused by the coating penetrating into the wood pores, avoiding incomplete delamination due to an excessively thin film or sagging due to an excessively thick film.

[0037] In some embodiments, the specific process conditions for flash drying and delamination in step S3 are as follows: after coating, the coating is left to stand for 30-45 minutes in a windless environment at a temperature of 20-30°C. By controlling the standing time at 20-30°C for 30-45 minutes, sufficient time is given for low surface energy components to fully migrate from the bulk phase and accumulate at the gas-liquid interface.

[0038] In some embodiments, step S3, the gradient curing includes a first curing stage and a second curing stage: the first curing stage is heating at 75-85°C for 1.5-2.5 hours; the second curing stage is heating at 130-150°C for 0.5-1.5 hours. During the first curing stage, the reaction rate is moderate, and the coating system undergoes initial cross-linking. This not only stabilizes the formed gradient layered structure, preventing component backmixing due to a sudden drop in viscosity caused by excessively high temperatures, but also allows residual slow-evaporating solvents (such as PMA) to escape smoothly, avoiding pinholes or bubble defects caused by solvent boiling. During the second curing stage (130-150°C for 0.5-1.5 hours), the higher temperature provides sufficient energy to drive the deep esterification reaction between citric acid and epoxy resin, maximizing the cross-linking density and endowing the coating with excellent mechanical strength and water resistance. More importantly, this high-temperature treatment activates the transesterification catalytic activity in the polymer network, pre-setting a dynamic bonding mechanism, and endowing the coating with stress relaxation and self-healing functions.

[0039] The present invention will be further described below by way of specific embodiments.

[0040] Unless otherwise specified, the experimental methods used in the following examples are conventional methods already available in the prior art; unless otherwise specified, the experimental materials used in the following examples were all purchased from commercial channels. Partial raw material descriptions: Ti3AlC2 powder: 400 mesh; Bisphenol A epoxy resin: E51 type; Epoxy-modified polysiloxane: side chain containing epoxy groups; Rheology modifier: hydrophobically modified fumed silica (R972); Dispersant: BYK-161.

[0041] Example 1: Ti3AlC2 powder was slowly added to a mixed solution containing LiF and hydrochloric acid at a mass ratio of 1:1. The mixture was magnetically stirred at 35°C for 24 hours. After the reaction, the supernatant was repeatedly washed with deionized water by centrifugation until the pH of the supernatant was close to neutral. The precipitate was then ultrasonically exfoliated in an ice-water bath for 1 hour, and the unexfoliated particles were removed by centrifugation. The upper Ti3C2T layer was collected. x Nanosheet dispersion. The solvent in the dispersion was replaced with anhydrous ethanol. Adding a layer relative to Ti3C2T... x Perfluorooctyltriethoxysilane (1.5 wt% by weight) was added to nanosheets, the pH was adjusted to 4.5 with acetic acid, and the mixture was refluxed and stirred at 60 °C for 12 hours. The product was washed three times by centrifugation with ethanol, dried under vacuum at 60 °C, and then ground to obtain fluorinated MXene.

[0042] The ingredients are prepared according to the following parts by weight: 70 parts cashew phenol glycidyl ether, 15 parts bisphenol A epoxy resin, 10 parts epoxy modified polysiloxane, 1.5 parts fluorinated MXene, 2.5 parts rheology modifier, 0.5 parts dispersant, and 40 parts mixed solvent. The ratio of the mixed solvent is xylene:PMA:n-butanol = 5:4:1 (mass ratio).

[0043] Fluorinated MXene was added to a mixed solvent and ultrasonically dispersed for 30 minutes to obtain a dispersion. In a high-speed disperser, cashew phenol glycidyl ether, bisphenol A epoxy resin, rheology modifier, dispersant, and dispersion were added, and then sheared at 2000 rpm for 20 minutes. Subsequently, the speed was reduced to 400 rpm, epoxy-modified polysiloxane was added, and the mixture was stirred at low speed for 10 minutes. After vacuum degassing, a waterproof coating was obtained.

[0044] Citric acid was dissolved in anhydrous ethanol to prepare a 50% (w / w) citric acid curing agent solution. Marine plywood with a moisture content of 6% was selected, sanded with 200-grit sandpaper along the grain, and after dust removal with compressed air, the surface was wiped with a lint-free cloth dampened with acetone for degreasing. The waterproof coating and the citric acid curing agent solution were mixed at a molar ratio of carboxyl groups to epoxy groups of 1:1, and mechanically stirred until homogeneous. The coating was sprayed onto the plywood surface using a high-pressure airless sprayer, controlling the wet film thickness to 280 μm. The sprayed sample was then horizontally placed at 25°C in a windless environment for 35 minutes. The sample was then placed in an oven, heated at 80°C for 2 hours in the first stage, and then heated to 140°C for 1 hour in the second stage. After natural cooling, the waterproof marine plywood was obtained.

[0045] Example 2: Consistent with Example 1, except that the waterproof coating formulation (parts by weight) is as follows: 60 parts cashew phenol glycidyl ether, 20 parts bisphenol A epoxy resin, 5 parts epoxy modified polysiloxane, 3 parts fluorinated MXene, 4 parts rheology modifier, 1 part dispersant, and 30 parts mixed solvent.

[0046] Example 3: Consistent with Example 1, except that the waterproof coating formulation (parts by weight) is as follows: 80 parts cashew phenol glycidyl ether, 10 parts bisphenol A epoxy resin, 15 parts epoxy modified polysiloxane, 0.5 parts fluorinated MXene, 1 part rheology modifier, 0.1 parts dispersant, and 50 parts mixed solvent.

[0047] Example 4: Consistent with Example 1, except that the ratio of the mixed solvent is xylene:PMA:n-butanol = 4:5:1; the high-speed shearing speed is 1800 rpm for 15 minutes; the low-speed stirring speed is 200 rpm for 5 minutes; the molar ratio of the carboxyl group of the curing agent to the epoxy group of the waterproof coating is 0.9:1; during oven curing, the first stage is heated at 75°C for 2.5 hours; the second stage is heated at 130°C for 1.5 hours.

[0048] Example 5: Consistent with Example 1, except that the ratio of the mixed solvent is xylene:PMA:n-butanol = 6:3:1; the high-speed shearing speed is 2200 rpm for 25 minutes; the low-speed stirring speed is 600 rpm for 15 minutes; the molar ratio of the carboxyl group of the curing agent to the epoxy group of the waterproof coating is 1.1:1; during oven curing, the first stage is heated at 85°C for 1.5 hours; and the second stage is heated at 150°C for 0.5 hours.

[0049] Example 6: Consistent with Example 1, except that the amount of perfluorooctyltriethoxysilane added is relative to Ti3C2T x The nanosheets weighed 2.0 wt% and were refluxed at a stirring temperature of 65 °C.

[0050] Comparative Example 1: Consistent with Example 1, except that no fluorinated MXene is added.

[0051] Comparative Example 2: Consistent with Example 1, except that bisphenol A epoxy resin is used instead of cashew phenol glycidyl ether, and the curing agent is replaced with polyetheramine curing agent (D-230).

[0052] Test method: Surface wettability test: The test was conducted using a contact angle meter. At room temperature, 5 μL of deionized water was added to the cured plywood coating surface, and the static water contact angle (WCA) was measured at 5 different points and the average value was taken.

[0053] Adhesion test: The test was conducted using a portable pull-out tester according to ASTM D4541. A 20 mm diameter aluminum ingot was bonded to the coating surface, cured, and then pulled vertically. The maximum tensile stress (MPa) at which the coating peeled off was recorded.

[0054] Crack resistance test under wet and hot cycling: Simulating the alternating wet and dry conditions of a marine environment, the following cycling method was established: The sample was immersed in artificial seawater at 25℃ for 12 hours; then removed, dried, and placed in an oven at 80℃ for 12 hours. This constitutes one cycle, and 10 cycles were performed consecutively. After each cycle, the coating surface was observed using a 50x magnifying glass for microcracks. The number of cycles in which the first crack appeared was recorded; the higher the number of cycles, the stronger the crack resistance.

[0055] The test data is summarized in Table 1.

[0056] Table 1

[0057] Referring to the test results in Table 1, the water contact angles of Examples 1-6 all reached or approached 150°, indicating a superhydrophobic state, and were significantly higher than the 92.2° of pure epoxy resin in Comparative Example 2 and the 108.1° of Comparative Example 1. This demonstrates that the present invention successfully drives the enrichment of fluorinated MXene and epoxy-modified polysiloxane to the surface by utilizing the solvent evaporation gradient (PMA / xylene system) and surface energy differences. Example 1 showed no cracks after 10 rigorous "seawater immersion-high temperature baking" cycles, exhibiting excellent dimensional adaptability. In contrast, although Comparative Example 3 had a high initial adhesion (5.3 MPa), it experienced severe cracking in the second cycle. This was because when the wood swelled and shrank, generating stress, the polymer network underwent stress relaxation through transesterification, thus avoiding brittle fracture.

[0058] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0059] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. 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 spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the protection scope of the present invention.

Claims

1. A method for preparing waterproof marine plywood, characterized in that, Includes the following steps: Step S1: Add fluorinated MXene to the solvent and disperse it by ultrasonication to obtain a dispersion. Step S2: In a high-speed disperser, add cashew phenol glycidyl ether, bisphenol A epoxy resin, rheology modifier, dispersant and the dispersion obtained in step S1, and perform high-speed shear dispersion. Then switch to low-speed stirring, add epoxy-modified polysiloxane, and stir evenly to obtain a waterproof coating. Step S3: Pre-treat the plywood by mixing the waterproof coating obtained in step S2 with the curing agent citric acid solution evenly, applying it to the surface of the plywood, and then flash-drying and layering and step-curing to obtain waterproof marine plywood.

2. The preparation method according to claim 1, characterized in that, The waterproof coating comprises, by weight, 60-80 parts of cashew phenol glycidyl ether, 10-20 parts of bisphenol A epoxy resin, 5-15 parts of epoxy-modified polysiloxane, 0.5-3 parts of fluorinated MXene, 1-4 parts of rheology modifier, 0.1-1 parts of dispersant, and 30-50 parts of solvent.

3. The preparation method according to claim 2, characterized in that, The solvent is a mixed solvent, including xylene, propylene glycol methyl ether acetate and n-butanol, with a mass ratio of (4-6):(3-5):(0.5-1.5); the rheology modifier is hydrophobically modified fumed silica.

4. The preparation method according to claim 1, characterized in that, In step S1, the preparation method of the fluorinated MXene includes the following steps: Step S101: Add Ti3AlC2 powder to a mixed solution containing LiF and hydrochloric acid, stir and react at 30-40℃ for 20-25 hours, centrifuge and wash until neutral, and ultrasonically exfoliate to obtain Ti3C2T. x Nanosheet dispersion; Step S102: Add a certain amount of Ti3C2T to the dispersion. x Perfluorooctyltriethoxysilane, weighing 1.5-2 wt% by weight, was added to nanosheets. The pH was adjusted to acidic, and the mixture was refluxed and stirred at 60-65°C for 12 hours. After washing and drying, the fluorinated MXene was obtained.

5. The preparation method according to claim 1, characterized in that, In step S2, the high-speed shear dispersion speed is 1800-2200 rpm, and the dispersion time is 15-25 minutes; the low-speed stirring speed is 200-600 rpm, and the stirring time is 5-15 minutes.

6. The preparation method according to claim 1, characterized in that, In step S3, the curing agent citric acid solution is an ethanol solution of citric acid with a mass concentration of 40-60%; the mixing ratio of the waterproof coating and the curing agent citric acid solution is measured according to a molar ratio of carboxyl groups to epoxy groups of (0.9-1.1):

1.

7. The preparation method according to claim 1, characterized in that, In step S3, the plywood pretreatment steps include: selecting marine plywood with a moisture content of less than 6%, sanding the surface with 180-240 grit sandpaper along the grain, removing dust with compressed air, and then wiping the surface with acetone for degreasing treatment.

8. According to the preparation method of claim 1, in step S3, the coating is carried out by high-pressure airless spraying, and the wet film thickness of the coating is controlled to be 250-300 μm.

9. According to the preparation method of claim 1, in step S3, the specific process conditions for the flash drying and layering are as follows: after coating, the coating is left to stand for 30-45 minutes in a windless environment at a temperature of 20-30℃.

10. The preparation method according to claim 1, wherein in step S3, the stepwise curing includes a first curing stage and a second curing stage: the first curing stage is heating at 75-85°C for 1.5-2.5 hours; the second curing stage is heating at 130-150°C for 0.5-1.5 hours.

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