A rub-repairable super-hydrophobic waterborne polyurethane coating, and a preparation method and application thereof

Abstract

The application discloses a rub-repairable super-hydrophobic waterborne polyurethane coating and a preparation method and application thereof, and relates to the technical field of coatings.The coating comprises the following components in percentage by mass: 5 wt.%-15 wt.% of hydrophobic modified nano-particles, 15 wt.%-20 wt.% of porous diatomite, 30 wt.%-60 wt.% of waterborne polyurethane, and the balance of water, and the sum of the percentage by mass of the components is 100%; the hydrophobic modified nano-particles are filled in the pores of the diatomite to form diatomite capsules, the hydrophilicity of the surface of the diatomite is ingeniously utilized to uniformly disperse the diatomite in the waterborne polyurethane emulsion, and the super-hydrophobic waterborne polyurethane coating which can be uniformly and stably dispersed is obtained; and the super-hydrophobic coating prepared from the coating has the rub-repairable performance.

Description

Technical Field

[0001] This invention relates to the field of coating technology, specifically to a friction-repairable superhydrophobic waterborne polyurethane coating, its preparation method, and its application. Background Technology

[0002] Environmentally friendly water-based coatings use water as the dispersion medium, effectively reducing the use of organic solvents and VOC emissions. In recent years, water-based emulsion coatings have experienced rapid development and their application in the coatings industry is expanding, showing a trend of gradually replacing traditional solvent-based coatings. Among them, water-based polyurethane coatings have advantages such as stable chemical structure and strong adhesion to substrates, and are widely used in home building materials, metal corrosion protection, and floor coatings. However, due to the introduction of hydrophilic groups into the resin molecules, their coatings are not water-resistant and are prone to blistering, cracking, and peeling. Superhydrophobic modification of water-based polyurethane coatings can not only improve their poor water resistance and insufficient weather resistance, but also endow them with more functionalities such as self-cleaning, anti-fouling, and anti-corrosion, which is of great significance for their high-performance development.

[0003] Low surface energy materials and rough surface structures are two necessary conditions for achieving superhydrophobicity. However, on the one hand, the surface energy difference between low surface energy materials and water is significant, making them difficult to disperse in water. This contradiction between low surface energy and water-based coatings severely limits the development of water-based superhydrophobic coatings. On the other hand, once the rough surface structure is damaged by external forces, the superhydrophobic properties of the coating are easily reduced or even lost, resulting in poor durability of existing superhydrophobic coatings, which is a major factor hindering their commercial application. Self-healing designs can extend the service life of superhydrophobic coatings. For example, patents such as CN 110358435A, CN116606590B, and CN 101791608A achieve self-healing properties in superhydrophobic coatings by introducing self-healing polymer materials or thermoplastic resin film-forming agents. However, these types of superhydrophobic coatings require the use of organic reagents to dissolve and disperse the self-healing polymers, and the self-healing function is limited to the self-healing of chemical substances on the damaged coating surface. For surfaces with severely damaged rough structures, self-healing is not possible. To address the aforementioned issues, there is an urgent need to design and prepare a water-based superhydrophobic coating that combines water-based environmental friendliness with abrasion resistance and repairability. This would greatly promote the green and high-performance development of coatings. Summary of the Invention

[0004] To address the shortcomings of the aforementioned background technology, this invention provides a tribologically repairable superhydrophobic waterborne polyurethane coating, its preparation method, and its application. The method first involves filling the pores of diatomaceous earth with hydrophobically modified nanoparticles to form diatomaceous earth capsules. The hydrophilicity of the diatomaceous earth surface is cleverly utilized to uniformly disperse these capsules in an aqueous polyurethane emulsion, resulting in a uniformly and stably dispersed superhydrophobic waterborne polyurethane coating. When this superhydrophobic waterborne polyurethane coating is applied to a substrate surface, the hydrophobically modified nanoparticles encapsulated within the diatomaceous earth pores are dynamically released through sandpaper friction, simultaneously achieving the construction of a micro / nano rough surface structure and the release of low surface energy substances, thus endowing the coating with superhydrophobicity. This method is extremely simple and time-saving, requiring no complex equipment or procedures. More importantly, the coating exhibits excellent resistance to mechanical wear; when the surface superhydrophobicity decreases due to factors such as light and heat, it can be restored through simple friction.

[0005] The first objective of this invention is to provide a tribologically repairable superhydrophobic waterborne polyurethane coating, the coating comprising the following components by weight percentage:

[0006] The composition consists of 5 wt.%–15 wt.% hydrophobically modified nanoparticles, 15 wt.%–20 wt.% porous diatomaceous earth, 30 wt.%–60 wt.% waterborne polyurethane, with the balance being water. The sum of the mass percentages of all components is 100%.

[0007] The hydrophobically modified nanoparticles are prepared by hydrophobically modifying nanoparticles.

[0008] The nanoparticles are one or more of the following: nano-silica, nano-titanium dioxide, nano-calcium hydroxide, nano-calcium carbonate, nano-alumina, nano-magnesium oxide, nano-magnesium hydroxide, nano-iron oxide particles, silver nanoparticles, polystyrene nanoparticles, polytetrafluoroethylene nanospheres, polyvinylidene fluoride nanospheres, and cellulose nanocrystals.

[0009] Preferably, the hydrophobic modified nanoparticles have a particle size of 10~100 nm; the porous diatomaceous earth has a particle size of 20~60 μm and a pore size of 500 nm~2 μm.

[0010] Preferably, the hydrophobically modified nanoparticles are prepared according to the following steps:

[0011] After ultrasonically dispersing nanoparticles in a mixed solution containing ethanol, water and ammonia, a fluorosilane coupling agent is added and the mixture is stirred to obtain hydrophobically modified nanoparticles.

[0012] The volume percentage of ethanol in the mixed solution is 70-90%, the volume percentage of water is 5-20%, and the volume percentage of ammonia is 2-10%, wherein the sum of the volume percentages of ethanol, water, and ammonia is 100%.

[0013] During the stirring reaction, the stirring temperature is 20~60℃ and the stirring time is 5-10 h.

[0014] Preferably, the fluorinated silane coupling agent is one or more of perfluorinated trimethoxysilane, perfluorinated triethoxysilane, and perfluorinated trichlorosilane; the amount of the fluorinated silane coupling agent added is 0.5-2 wt.%.

[0015] Preferably, the waterborne polyurethane is anionic waterborne polyurethane, cationic waterborne polyurethane, or nonionic waterborne polyurethane.

[0016] The second objective of this invention is to provide a method for preparing a friction-repairable superhydrophobic waterborne polyurethane coating, comprising the following steps:

[0017] Hydrophobic nanoparticles were uniformly dispersed in ethyl acetate, and porous diatomaceous earth was added and stirred. The mixture was then centrifuged to obtain diatomaceous earth capsules coated with hydrophobic nanoparticles.

[0018] Aqueous polyurethane is uniformly dispersed in water to obtain an aqueous polyurethane emulsion;

[0019] Adding diatomaceous earth capsules to an aqueous polyurethane emulsion and mixing them under normal temperature and pressure yields a superhydrophobic aqueous polyurethane coating that can be abraded and repaired.

[0020] Preferably, the process of adding porous diatomaceous earth and stirring includes: stirring at a temperature of 20~60℃ and stirring for 2~5 hours.

[0021] The third objective of this invention is to provide an application of a friction-repairable superhydrophobic waterborne polyurethane coating in the friction repair of substrate surfaces.

[0022] The fourth objective of this invention is to provide a superhydrophobic coating with friction-repairing properties, which is prepared by coating a friction-repairing superhydrophobic waterborne polyurethane coating onto a substrate.

[0023] The fifth objective of this invention is to provide a method for preparing a superhydrophobic coating with friction-repairing properties, comprising the following steps:

[0024] A superhydrophobic waterborne polyurethane coating with abrasion repair properties is applied to a substrate by spraying, brushing, or dipping. After drying and curing, the hydrophobic modified nanoparticles encapsulated in diatomaceous earth are exposed after sanding, thus obtaining a superhydrophobic coating with abrasion repair properties. The substrate includes wood, paper, metal, concrete, glass, plastic, rubber, or fiber fabric.

[0025] Compared with the prior art, the beneficial effects of the present invention are:

[0026] This invention provides a friction-repairable superhydrophobic waterborne polyurethane coating, its preparation method, and its application. The friction-repairable superhydrophobic waterborne polyurethane coating provided by this invention combines waterborne environmental friendliness with friction resistance and repairability. Its preparation method is simple, cleverly utilizing the porous structure of diatomaceous earth to encapsulate hydrophobic nanoparticles. Simultaneously, the hydrophilic structure of the diatomaceous earth surface endows it with the ability to disperse uniformly and stably in aqueous systems, enabling uniform mixing with aqueous polymer emulsions. The prepared superhydrophobic composite coating exhibits excellent resistance to mechanical wear and aging. After wear, it not only does not damage the superhydrophobic properties but also enhances roughness and releases hydrophobic particles. Moreover, when the surface superhydrophobicity decreases due to uncontrollable factors, it can be restored through simple friction, effectively solving the problem of poor durability of superhydrophobic coatings. Attached Figure Description

[0027] Figure 1 The infrared spectra are those of the hydrophobically modified nanoparticles in Example 1 and the diatomite capsules SiO2@Diatomite in Example 3.

[0028] Figure 2 This is a SEM image of the TiO2@Diatomite diatomite capsules from Example 4.

[0029] Figure 3 This represents the dispersion state of the diatomite capsule SiO2@Diatomite and the hydrophobically modified nanoparticles without diatomite coating in an aqueous polyurethane emulsion in Example 6.

[0030] Figure 4 The images shown are SEM images of the superhydrophobic waterborne polyurethane coating on the wood surface before and after friction in Example 8.

[0031] Figure 5 The anti-wetting properties of various liquids after applying a superhydrophobic waterborne polyurethane coating to the wood surface in Example 8.

[0032] Figure 6 The water contact angle is the angle after applying a superhydrophobic waterborne polyurethane coating to the wood surface in Example 9.

[0033] Figure 7 The water contact angle changes during multiple cycles of plasma treatment and friction repair treatment of the superhydrophobic waterborne polyurethane coating on the steel surface in Example 9. Detailed Implementation

[0034] To enable those skilled in the art to better understand and implement the technical solutions of the present invention, the present invention will be further described below in conjunction with specific embodiments and accompanying drawings. However, the embodiments described are not intended to limit the present invention.

[0035] This invention addresses the problem that existing technologies achieve self-healing of superhydrophobic coatings by introducing self-healing polymer materials or thermoplastic resin film-forming agents, but require the use of organic reagents to dissolve and disperse the self-healing polymers, and the self-healing function is limited to the self-healing of chemical substances on the damaged coating surface, failing to achieve self-healing for surfaces with severely damaged rough structures. This invention provides a friction-healable superhydrophobic waterborne polyurethane coating, its preparation method, and its application.

[0036] To achieve the above objectives, a first aspect of the present invention provides a tribologically repairable superhydrophobic waterborne polyurethane coating, the coating comprising the following components by weight percentage:

[0037] The composition consists of 5 wt.%–15 wt.% hydrophobically modified nanoparticles, 15 wt.%–20 wt.% porous diatomaceous earth, 30 wt.%–60 wt.% waterborne polyurethane, with the balance being water. The sum of the mass percentages of all components is 100%.

[0038] This invention utilizes the porous structure of micron-sized diatomaceous earth to encapsulate hydrophobic nanoparticles. The hydrophilic structure of the diatomaceous earth surface ensures uniform and stable dispersion in an aqueous system, solving the problem of hydrophobic nanoparticle aggregation and dispersion difficulties in water. This achieves the simultaneous provision of a micro / nano hierarchical structure and low surface energy, endowing the composite coating with superhydrophobicity. Waterborne polyurethane, as the main film-forming substance, provides strong adhesion between the diatomaceous earth, hydrophobically modified nanoparticles, and the substrate, resulting in a superhydrophobic composite coating with excellent mechanical wear resistance. Furthermore, wear can dynamically release the hydrophobic nanoparticles and increase roughness, making it repairable. This coating simultaneously achieves water-based properties, superhydrophobicity, mechanical wear resistance, and repairability.

[0039] The hydrophobically modified nanoparticles are prepared by hydrophobically modifying nanoparticles.

[0040] The nanoparticles are one or more of the following: nano-silica, nano-titanium dioxide, nano-calcium hydroxide, nano-calcium carbonate, nano-alumina, nano-magnesium oxide, nano-magnesium hydroxide, nano-iron oxide particles, silver nanoparticles, polystyrene nanoparticles, polytetrafluoroethylene nanospheres, polyvinylidene fluoride nanospheres, and cellulose nanocrystals.

[0041] The hydrophobic modified nanoparticles have a particle size of 10~100 nm; the porous diatomaceous earth has a particle size of 20~60 μm and a pore size of 500 nm~2 μm.

[0042] The hydrophobically modified nanoparticles were prepared according to the following steps:

[0043] After ultrasonically dispersing nanoparticles in a mixed solution containing ethanol, water and ammonia, a fluorosilane coupling agent is added and the mixture is stirred to obtain hydrophobically modified nanoparticles.

[0044] The volume percentage of ethanol in the mixed solution is 70-90%, the volume percentage of water is 5-20%, and the volume percentage of ammonia is 2-10%, wherein the sum of the volume percentages of ethanol, water, and ammonia is 100%.

[0045] During the stirring reaction, the stirring temperature is 20~60℃ and the stirring time is 5-10 h.

[0046] The fluorinated silane coupling agent is one or more of perfluorinated trimethoxysilane, perfluorinated triethoxysilane, and perfluorinated trichlorosilane; the amount of the fluorinated silane coupling agent added is 0.5-2 wt.%.

[0047] The waterborne polyurethane is anionic waterborne polyurethane, cationic waterborne polyurethane, or nonionic waterborne polyurethane.

[0048] A second aspect of this invention provides a method for preparing a friction-repairable superhydrophobic waterborne polyurethane coating, comprising the following steps:

[0049] Hydrophobic nanoparticles were uniformly dispersed in ethyl acetate, and porous diatomaceous earth was added and stirred. The mixture was then centrifuged to obtain diatomaceous earth capsules coated with hydrophobic nanoparticles.

[0050] Aqueous polyurethane is uniformly dispersed in water to obtain an aqueous polyurethane emulsion;

[0051] Adding diatomaceous earth capsules to an aqueous polyurethane emulsion and mixing them under normal temperature and pressure yields a superhydrophobic aqueous polyurethane coating that can be abraded and repaired.

[0052] The process of adding porous diatomaceous earth and stirring includes: stirring at a temperature of 20-60°C and stirring for 2-5 hours.

[0053] In one embodiment, a method for preparing a friction-repairable superhydrophobic waterborne polyurethane coating includes the following steps:

[0054] Step 1: Preparation of hydrophobically modified nanoparticles. Nanoparticles were ultrasonically dispersed in a mixed solution of ethanol / water / ammonia, then a fluorosilane coupling agent was added. The mixture was stirred at a certain temperature, and the hydrophobically modified nanoparticles were collected by centrifugation.

[0055] Step 2: Preparation of diatomaceous earth capsules. Under normal temperature and pressure, the hydrophobic nanoparticles from Step 1 were ultrasonically dispersed in ethyl acetate, and an appropriate amount of porous diatomaceous earth was added and stirred. The capsules coated with hydrophobic nanoparticles were then collected by centrifugation.

[0056] Step 3: Preparation of abrasion-repairable superhydrophobic waterborne polyurethane coating. The diatomaceous earth capsules prepared in Step 2 are mixed with the waterborne polyurethane emulsion in a certain proportion and stirred and dispersed evenly at room temperature and pressure to obtain the abrasion-repairable superhydrophobic waterborne polyurethane coating.

[0057] The stirring in steps 1, 2 and 3 is carried out by one or more of the following methods: mechanical stirring, magnetic stirring, ultrasonic stirring and oscillating stirring. The stirring temperature range in step 1 is 20~60℃ and the stirring time is 5-10 h. The stirring time in steps 2 and 3 is 2-5 h.

[0058] The aqueous polyurethane emulsion in step 3 is one of anionic aqueous polyurethane, cationic aqueous polyurethane, or nonionic aqueous polyurethane.

[0059] The third aspect of this invention provides an application of a friction-repairable superhydrophobic waterborne polyurethane coating in the friction repair of substrate surfaces.

[0060] The fourth aspect of the present invention provides a superhydrophobic coating with friction-repairing properties, which is prepared by coating a friction-repairing superhydrophobic waterborne polyurethane coating onto a substrate.

[0061] The fifth aspect of this invention provides a method for preparing a superhydrophobic coating with friction-repairing properties, comprising the following steps:

[0062] A superhydrophobic waterborne polyurethane coating with abrasion repair properties is applied to a substrate by spraying, brushing, or dipping. After drying and curing, the hydrophobic modified nanoparticles encapsulated in diatomaceous earth are exposed after sanding, thus obtaining a superhydrophobic coating with abrasion repair properties.

[0063] In one embodiment, the abrasion-repairable superhydrophobic waterborne polyurethane coating is applied to substrates such as wood, paper, metal, concrete, glass, plastic, rubber, and fiber fabric by spraying, brushing, or dipping. After drying and curing, the hydrophobic modified nanoparticles encapsulated in the diatomaceous earth are exposed after sanding, thus obtaining a superhydrophobic coating with abrasion-repair properties. The curing temperature range is 20~80℃, and the higher the temperature, the shorter the required curing time.

[0064] The superhydrophobic coating with friction repair properties can restore its superhydrophobicity after the superhydrophobic properties are reduced or lost due to natural aging, mechanical damage, plasma interference, etc., by rubbing the surface with sandpaper.

[0065] It should be noted that, unless otherwise specified, the experimental methods used in this invention are all conventional methods; and the reagents and materials used, unless otherwise specified, are all commercially available.

[0066] Example 1

[0067] Preparation of hydrophobically modified silica nanoparticles:

[0068] First, add 3.6 g of silica particles with a particle size of about 30 nm, then add 80 mL of ethanol, 8 mL of deionized water, and 4 mL of ammonia. Stir mechanically at 50 °C for 10 min, then add 0.48 mL of perfluorinated trichlorosilane. React for 5 h, and after centrifugation and drying, hydrophobic modified silica nanoparticles with F element grafted on the surface can be obtained.

[0069] Example 2

[0070] Preparation of hydrophobically modified titanium dioxide nanoparticles:

[0071] First, add 1.5 mL of titanium dioxide particles with a particle size of about 30 nm, then add 40 mL of ethanol, 4 mL of deionized water, and 2 mL of ammonia. Stir mechanically at 50 °C for 10 min, then add 0.25 mL of perfluorodecyltrimethoxysilane. React for 10 h, and after centrifugation and drying, hydrophobic modified titanium dioxide nanoparticles with F element grafted on the surface can be obtained.

[0072] Example 3

[0073] Preparation of SiO2@Diatomite capsules:

[0074] The entire process was carried out at room temperature and pressure. The hydrophobic modified silica particles from Example 1 were dispersed in 100 mL of ethyl acetate, and 12 g of diatomite was added and stirred. After stirring for 3 h, the mixture was filtered, washed with ethanol and water in sequence, and dried to obtain the diatomite capsule SiO2@Diatomite. The hydrophobic modified silica particles filled the pore structure of the diatomite.

[0075] Example 4

[0076] Preparation of TiO2@Diatomite capsules:

[0077] The entire process was carried out at room temperature and pressure. The hydrophobic modified titanium dioxide particles from Example 2 were dispersed in 100 mL of ethyl acetate, and 12 g of diatomite was added and stirred. After stirring for 3 h, the mixture was filtered, washed with ethanol and water in sequence, and dried to obtain the diatomite capsule SiO2@Diatomite. The hydrophobic modified titanium dioxide particles filled the pore structure of the diatomite.

[0078] Example 5

[0079] Preparation of PTFE@Diatomite capsules:

[0080] Preparation of diatomaceous earth capsules: The entire process was carried out at room temperature and pressure. Polytetrafluoroethylene nanospheres (50 nm in diameter) were directly dispersed in 100 mL of ethyl acetate, and 12 g of diatomaceous earth was added and stirred. The reaction was carried out for 3 h. After filtration, the capsules were washed with ethanol and water in sequence and then dried.

[0081] Example 6

[0082] Preparation of waterborne polyurethane superhydrophobic coatings:

[0083] Aqueous polyurethane emulsion was prepared by dispersing 3.5 g of aqueous polyurethane in 3.5 g of water. 3.0 g of SiO2@Diatomite diatomite capsules prepared in Example 3 were added to the aqueous polyurethane emulsion under mechanical stirring. The mixture was thoroughly stirred and mixed at room temperature and pressure to obtain an aqueous superhydrophobic coating with a diatomite capsule content of 30%. The coating exhibited a uniform milky white color, indicating that the SiO2@Diatomite capsules were uniformly and stably dispersed in the aqueous polyurethane emulsion. In contrast, the hydrophobically modified silica nanoparticles without diatomite coating directly agglomerated in the aqueous polyurethane emulsion, suspended above the solution, and could not be dispersed.

[0084] Example 7

[0085] Preparation of waterborne polyurethane superhydrophobic coatings:

[0086] 4.0 g of waterborne polyurethane was dispersed in 4.0 g of water to prepare a waterborne polyurethane emulsion. 2.0 g of PTFE@Diatomite capsules prepared in Example 5 was added to the above waterborne polyurethane emulsion under mechanical stirring. The mixture was stirred and mixed thoroughly at room temperature and pressure to obtain a waterborne superhydrophobic coating with a diatomite capsule mass ratio of 20%.

[0087] Example 8

[0088] Abrasion-repairable superhydrophobic waterborne polyurethane coating for wood surfaces:

[0089] The waterborne polyurethane superhydrophobic coating prepared in Example 6 was sprayed onto a cedar wood board and cured at 40°C for 6 hours. The surface was then sanded with 200-grit sandpaper. After 10 cycles of abrasion under a 100 g weight, the surface exhibited superhydrophobicity with a water contact angle of 152.5 ± 1.05°. It also showed resistance to wetting from cola, seawater, fruit juice, milk, tea, etc.

[0090] The above coating has excellent abrasion repair properties. Specifically, when a cedar board coated with water-based polyurethane superhydrophobic coating is scratched with a knife, the superhydrophobicity of the surface decreases and changes from superhydrophobic to hydrophobic. However, after the scratched area is rubbed with sandpaper to make it relatively smooth, the surface can be restored to superhydrophobicity.

[0091] Example 9

[0092] Superhydrophobic waterborne polyurethane coating for abrasion-repairable steel surfaces:

[0093] The waterborne polyurethane superhydrophobic coating prepared in Example 7 was sprayed onto a steel plate and cured at 80°C for 2 hours. The surface was then polished with 100-grit sandpaper. After 10 cycles of abrasion under a 200 g weight, the surface became superhydrophobic, with a water contact angle of 153.7 ± 0.25°.

[0094] The above coating has excellent abrasion repair properties, specifically: after a steel plate coated with water-based polyurethane superhydrophobic coating is placed in a plasma cleaning device, the surface wettability changes from superhydrophobic to superhydrophilic, but after simple abrasion with sandpaper, the surface can be restored to superhydrophobicity.

[0095] To illustrate the relevant properties of the superhydrophobic waterborne polyurethane coating for friction repair provided by this invention, the accompanying drawings are provided.

[0096] Figure 1 The infrared spectra of the hydrophobically modified nanoparticles (F-SiO2) in Example 1 and the diatomite capsules SiO2@Diatomite in Example 3 are shown. Compared to unmodified silica nanoparticles (SiO2), silica treated with perfluorinated trichlorosilane shows a higher infrared spectrum at 1210 cm⁻¹. -1 The presence of characteristic peaks at the CF bond positions indicates successful grafting of fluorosilanes onto the surface of the silica nanoparticles. Compared to pristine diatomite, diatomite capsules SiO2@Diatomite (Diatomite+F-SiO2) filled with hydrophobically modified silica nanoparticles show a higher peak at 1210 cm⁻¹. -1 The presence of characteristic peaks at the CF bond positions indicates the presence of hydrophobically modified silica in diatomaceous earth.

[0097] Figure 2 This is a SEM image of the TiO2@Diatomite diatomite capsules from Example 4. Figure 2 (a) is a SEM image of the original diatomite, showing a porous cavity structure; Figure 2 (b) is a SEM image of TiO2@Diatomite capsules, which shows the filling of nanoparticles in the cavity structure.

[0098] Figure 3 This represents the dispersion state of the diatomite capsule SiO2@Diatomite and the hydrophobically modified nanoparticles without diatomite coating in an aqueous polyurethane emulsion in Example 6. Figure 3 (a) shows the dispersion state of diatomite capsules SiO2@Diatomite in aqueous polyurethane emulsion. The overall appearance is uniformly milky white, indicating that the mixing is uniform and stable. Figure 3 (b) In order to directly disperse hydrophobic modified nanoparticles in the emulsion of waterborne polyurethane, there is obvious stratification, and the hydrophobic nanoparticles agglomerate and suspend in the upper layer of the emulsion, making it difficult to disperse.

[0099] Figure 4 The images shown are SEM images of the superhydrophobic waterborne polyurethane coating on the wood surface before and after friction in Example 8. Figure 4 (a) is a SEM image of the water-based polyurethane superhydrophobic coating after it has been sprayed onto the surface of a cedar board and cured. The surface is relatively smooth, but a small number of rough particles can be observed. Figure 4 (b) is the SEM image of the surface after it has been polished with 200-grit sandpaper. The surface shows a significant rough structure after polishing.

[0100] Figure 5 The anti-wetting properties of various liquids after applying a superhydrophobic waterborne polyurethane coating to the wood surface in Example 8 are shown. After sanding, the waterborne polyurethane coating exhibits superhydrophobicity due to the release of hydrophobic substances and a significant increase in roughness. Liquids such as cola, salt water, juice, milk, and tea form spherical shapes on its surface without any spreading or wetting.

[0101] Figure 6 The water contact angle is the angle after applying a superhydrophobic waterborne polyurethane coating to the wood surface in Example 9.

[0102] After being sanded, the water-based polyurethane coating exhibits superhydrophobicity due to the release of hydrophobic substances and a significant increase in roughness, resulting in a surface water contact angle as high as 153.7±0.25°.

[0103] Figure 7 This example illustrates the change in water contact angle of the superhydrophobic waterborne polyurethane coating on the steel surface during multiple cycles of plasma treatment and friction repair in Example 9. The steel plate coated with the waterborne polyurethane superhydrophobic coating was placed in a plasma cleaning device. The high-energy plasma etched the surface and generated polar groups, causing the surface water contact angle to decrease to below 10°, irreversibly changing it from superhydrophobic to superhydrophilic. However, after simple sandpaper friction, the hydrophobic substances on the surface were released and replenished, restoring the superhydrophobicity. Furthermore, the surface consistently returned to a superhydrophobic state during five plasma cleaning-friction cycles.

[0104] This invention describes preferred embodiments and their effects. However, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to include both the preferred embodiments and all changes and modifications falling within the scope of this invention.

[0105] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a superhydrophobic coating with tribological repair properties, characterized in that, Includes the following steps: A water-based polyurethane superhydrophobic coating was sprayed onto a cedar board and cured at 40°C for 6 hours. The surface was then sanded with 200-grit sandpaper and subjected to 10 cycles of abrasion under a 100 g weight. This resulted in a superhydrophobic coating with friction repair properties on the cedar board surface. The water contact angle of this coating reached 152.5 ± 1.05°. Among them, the preparation of waterborne polyurethane superhydrophobic coatings: 3.5 g of waterborne polyurethane was dispersed in 3.5 g of water to prepare a waterborne polyurethane emulsion. 3.0 g of diatomite capsules SiO2@Diatomite were added to the waterborne polyurethane emulsion under mechanical stirring. The mixture was stirred and mixed thoroughly at room temperature and pressure to obtain a waterborne superhydrophobic coating with a diatomite capsule mass ratio of 30%. Preparation of hydrophobically modified nanoparticles: 3.6 g of silica particles with a particle size of 30 nm were added to a mixed solution containing 80 mL of ethanol, 8 mL of deionized water and 4 mL of ammonia. The mixture was mechanically stirred at 50 °C for 10 min. Then, 0.48 mL of perfluorinated trichlorosilane was added, and the reaction was carried out for 5 h. After centrifugation and drying, hydrophobic modified silica nanoparticles with F element grafted on the surface were obtained. Preparation of SiO2@Diatomite capsules: At room temperature and pressure, hydrophobically modified silica nanoparticles were dispersed in 100 mL of ethyl acetate, and 12 g of diatomite was added and stirred. The mixture was reacted for 3 h, filtered, centrifuged, washed with ethanol and water in sequence, and dried to obtain diatomite capsules SiO2@Diatomite.

2. A method for preparing a superhydrophobic coating with tribological repair properties, characterized in that, Includes the following steps: A water-based polyurethane superhydrophobic coating was sprayed onto a steel plate and cured at 80°C for 2 hours. The surface was then polished with 100-grit sandpaper and subjected to 10 cycles of abrasion under a 200 g weight. This resulted in a superhydrophobic coating with friction repair properties on the steel plate surface. The water contact angle of this coating reached 153.7 ± 0.25°. Among them, the preparation of waterborne polyurethane superhydrophobic coatings: 4.0 g of waterborne polyurethane was dispersed in 4.0 g of water to prepare a waterborne polyurethane emulsion. 2.0 g of diatomite capsules PTFE@Diatomite were added to the waterborne polyurethane emulsion under mechanical stirring. The mixture was stirred and mixed thoroughly at room temperature and pressure to obtain a waterborne superhydrophobic coating with a diatomite capsule mass ratio of 20%. Preparation of PTFE@Diatomite capsules: At room temperature and pressure, 50 nm polytetrafluoroethylene nanospheres were dispersed in 100 mL of ethyl acetate, and 12 g of diatomite was added and stirred. The mixture was reacted for 3 h, filtered, centrifuged, washed with ethanol and water, and dried to obtain PTFE@Diatomite diatomite capsules.

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