High-weather-resistance transparent super-hydrophobic coating and preparation method thereof

Abstract

The invention discloses a high-weather-resistance transparent super-hydrophobic coating and a preparation method thereof. The high-weather-resistance transparent super-hydrophobic coating is prepared from modified cashew phenolic resin, hydrogen-containing silicone oil and organic glass microspheres according to the mass ratio of (12-28): (2-5): (12-20). The modified cashew nut phenolic resin is prepared from cashew nut phenolic resin, an N-containing silane coupling agent and isocyanate in a mass ratio of (72-80): (24-31): (4-14); according to the high-weather-resistance transparent super-hydrophobic coating obtained by the preparation method, super-hydrophobicity and high light transmittance (the light transmittance is greater than or equal to 90%) are realized at the same time, and the weather resistance and the mechanical stability are remarkably improved. When applied to a photovoltaic panel, the photovoltaic module can improve the power generation efficiency and reduce the operation and maintenance cost; the sensor is applied to windshields, cameras, laser radar mirror surfaces and other equipment of new energy automobiles, the sensing reliability of the sensor can be enhanced, the visual field in rainy days can be improved, energy consumption is reduced by improving the efficiency of an air conditioner heat exchanger, and the endurance mileage is increased.

Description

Technical Field

[0001] This invention relates to the field of superhydrophobic coating materials, and in particular to a weather-resistant transparent superhydrophobic coating and its preparation method, which can be applied to photovoltaic modules and new energy vehicles. Background Technology

[0002] Contamination control of the surfaces of high-performance equipment is crucial for ensuring their long-term stable operation, especially in the photovoltaic and new energy vehicle sectors. In photovoltaic power generation, the deposition of pollutants such as dust, sand, snow, and ice on the glass cover surface can cause a 5% to 30% loss in power generation efficiency, and even lead to a precipitous drop in power generation in cold regions. Existing hydrophobic coatings, due to insufficient resistance to ultraviolet aging and mechanical abrasion, are unable to meet the 25-year lifespan requirement of photovoltaic modules. In the new energy vehicle sector, similar issues directly affect driving safety and energy consumption: rainwater adhesion and dirt accumulation on windshields, cameras, and lidar lenses significantly reduce light transmittance and sensing accuracy. Studies have shown that camera contamination in rainy weather can increase the false judgment rate of the sensing system by 40%; icing / fogging in winter forces vehicles to frequently start electric heating for de-icing, increasing additional energy consumption by 15% to 20%.

[0003] Superhydrophobic coating technology, as an effective surface protection method, offers a new opportunity to solve the aforementioned problems. Its unique microstructure and low surface energy characteristics exhibit excellent hydrophobic properties, enabling water droplets to automatically roll off and carry away surface dust and other contaminants, achieving a self-cleaning effect. However, existing superhydrophobic coatings still have many shortcomings in industry applications. For photovoltaic modules, to ensure high light transmittance and maintain high photoelectric conversion efficiency, traditional superhydrophobic coatings are forced to reduce surface roughness, resulting in insufficient hydrophobic performance. In the exterior components of new energy vehicles, the coating needs to withstand long-term exposure to wind and rain, sand and gravel impacts, drastic temperature and humidity changes, and frequent cleaning and wiping. Traditional superhydrophobic coatings have low adhesion to the substrate and a fragile rough structure, making them easily damaged under these mechanical and environmental influences, leading to a rapid loss of hydrophobic properties.

[0004] Therefore, developing a transparent coating that combines high light transmittance, superhydrophobicity, strong wear resistance, and long-lasting weather resistance has become an urgent need to break through the technological bottlenecks of photovoltaic modules and new energy vehicles and promote industrial development. Summary of the Invention

[0005] To address the core challenge of balancing transparency and durability in traditional superhydrophobic coatings, this invention provides a highly weather-resistant, transparent superhydrophobic coating applicable to photovoltaic modules and new energy vehicles, along with its preparation method. Traditional superhydrophobic coatings typically rely on silica nanoparticles to construct micro / nano structures, which easily leads to coating turbidity or fogging, and strong scattering of visible light, failing to meet high light transmittance requirements. This invention aims to overcome this limitation; the prepared coating not only possesses high transparency and superhydrophobicity but also significantly improves weather resistance and mechanical stability. When applied to photovoltaic panels, it can improve power generation efficiency and reduce operation and maintenance costs; when applied to windshields, cameras, and lidar mirrors in new energy vehicles, it can enhance sensor reliability, improve visibility in rainy weather, and reduce energy consumption and increase driving range by improving the efficiency of air conditioning heat exchangers.

[0006] Based on this, the present invention provides a highly weather-resistant transparent superhydrophobic coating, which forms a micro-nano composite network structure of "molecular layer - microsphere skeleton - film-forming resin" by inducing self-assembly of modified cashew phenolic resin, plexiglass microspheres and hydrogen-containing silicone oil through solvent evaporation.

[0007] In a preferred embodiment, the mass ratio of the modified cashew phenolic resin, hydrogen-containing silicone oil, and plexiglass microspheres is 12-28:2-5:12-20.

[0008] In a preferred embodiment, the plexiglass microspheres are one or a mixture of several of the following: polymethyl methacrylate microspheres, polystyrene microspheres, or polyvinyl chloride microspheres.

[0009] In a preferred embodiment, the particle size of the plexiglass microspheres is between 80 and 120 nm.

[0010] In a preferred embodiment, the hydrogen-containing silicone oil may be one or a mixture of several of the following: hydrogen-terminated polydimethylsiloxane, partially hydrogen-terminated polydimethylsiloxane, hydrogen-terminated polydimethylmethylhydrosiloxane, or high-hydrogen-content silicone oil.

[0011] In a preferred embodiment, the modified cashew phenolic resin is a fluorinated modified cashew phenolic resin.

[0012] A preferred technical solution is that the preparation method of the fluorinated modified cashew phenolic resin includes:

[0013] The first step is to prepare aminated cashew phenolic resin by using an N-containing silane coupling agent and cashew phenolic resin;

[0014] The second step involves reacting the aminated cashew phenolic resin prepared in the first step with isocyanate to prepare fluorinated modified cashew phenolic resin.

[0015] In a preferred embodiment, the mass ratio of low-boiling-point solvent: medium-high-boiling-point solvent: high-boiling-point solvent in the composite solvent is 2-3:1-2:1-2.

[0016] The present invention also provides a method for preparing the high weather-resistant transparent superhydrophobic coating, wherein fluorinated cashew phenolic resin is weighed and dissolved in a composite solvent, stirred and dissolved at room temperature, plexiglass microspheres are dispersed in an organic solvent to form a suspension, and then added dropwise to the fluorinated cashew phenolic resin solution, and stirred until uniform, then hydrogen-containing silicone oil is added, and stirring is continued, and finally a catalyst, an inducer and an adhesion promoter are added, and stirred until uniform.

[0017] This invention also provides a method for implementing the aforementioned high weather-resistant transparent superhydrophobic coating. The first step involves rinsing and drying the substrate; the second step involves spraying the superhydrophobic coating using an air spray gun, and after spraying, placing the substrate in a controlled temperature and humidity environment: the first stage is set to 55°C. o C, RH≤35%, 2-8 minutes; second stage set at 35°C. o C, RH≤60%, 10-15 minutes; third stage set at 85 o C, 30-60 minutes. After gradient heating, allow to stand at room temperature for 24 hours to obtain a highly weather-resistant, transparent, superhydrophobic coating.

[0018] The advantages of this invention are:

[0019] Traditional silica nanoparticles are highly prone to aggregation, easily forming irregular, large-particle-size aggregates that induce strong light scattering. This significantly reduces coating transparency, resulting in an overall milky white or opaque appearance. Strong Rayleigh scattering is also a significant concern, as the nanoparticles rely primarily on weak physical adsorption rather than strong chemical bonding with the substrate. This leads to poor mechanical stability, low resistance to friction and scratches, and a short lifespan. Applications to photovoltaic panels or windshields can negatively impact the power generation efficiency of photovoltaic panels, as well as the visual clarity and durability of windshields and vehicle headlights. This invention utilizes the synergistic effect of plexiglass microspheres, modified cashew phenolic resin, and the inducing agent perfluoroalkyl polyoxyethylene ether. By precisely controlling the evaporation rate, the perfluoroalkyl polyoxyethylene ether, PMMA microspheres, and cashew phenolic resin-silicone rubber composite film-forming resin undergo non-solvent gas-phase induction during solvent evaporation. This induces the self-assembly of these components into a stable micro / nano composite structure with wavelengths shorter than visible light, avoiding the transmittance reduction problem caused by Rayleigh scattering. This achieves excellent optical transparency while maintaining superhydrophobic properties. Furthermore, the modified cashew phenolic resin / silicone rubber composite film-forming resin fills the gaps between the microspheres, fixing the microsphere structure through hydrosilylation. Based on the unique flexibility of the cashew phenolic resin side chains, the π–π stacking between benzene rings, and the strong and weak hydrogen bonding between systems, stress is effectively dispersed and absorbed, significantly improving impact resistance. This addresses the weakness of low mechanical strength in organic coatings, greatly enhancing the mechanical stability of the coating. Urea, amino, and phenolic hydroxyl groups in the film-forming resin act as adhesion groups, adhering to the substrate through interactions such as anion-cation interaction, coordination, and hydrogen bonding, thereby enhancing coating adhesion.

[0020] In the field of photovoltaic power generation, photovoltaic modules are susceptible to dust and rainwater adhesion, leading to decreased light transmittance and reduced power generation efficiency, and cleaning is time-consuming and water-intensive. The coating of this invention significantly reduces pollutant deposition through superhydrophobic self-cleaning effect, while ensuring light transmittance with high transparency. Combined with excellent weather resistance, it extends module life and reduces operation and maintenance costs.

[0021] In the field of new energy vehicles, this invention can significantly improve vehicle driving safety in adverse weather conditions and effectively reduce the impact of water film on visibility. Furthermore, in critical areas such as the battery compartment of new energy vehicles, this invention enhances the operational stability and safety of new energy vehicles under complex climatic conditions by reducing the adhesion and condensation of water vapor on surfaces. It can also reduce the de-icing energy consumption of electric vehicles in cold climates, improve de-icing efficiency, and extend the vehicle's driving range.

[0022] Based on its optical transparency of over 90%, water contact angle of 161.0°, and long-term weather resistance, the coating of this invention can achieve efficiency improvement, cost reduction, and safety assurance in both photovoltaic and new energy vehicle fields, and has outstanding practical application value. Attached Figure Description

[0023] To more clearly illustrate the specific solutions of the embodiments of this application, the accompanying drawings used in the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the accompanying drawings without creative effort.

[0024] Figure 1 These are morphological images of water droplets sprayed onto different substrates in Example 2 of this invention;

[0025] Figure 2 These are static contact angle measurement images of the samples from Comparative Examples 1-4 and Example 2 of this invention on an aluminum plate;

[0026] Figure 3 This is a wear resistance test of the samples from Comparative Examples 1-4 and Example 2 of this invention;

[0027] Figure 4 This refers to the water flow impact resistance test of the samples from Comparative Example 2, Comparative Example 3, and Example 2 of this invention;

[0028] Figure 5 This is a schematic diagram of the transmittance spectrum of high-transparency glass and the samples of Comparative Example 3 and Example 2 of the present invention sprayed onto high-transparency glass.

[0029] Figure 6 This is a UV irradiation resistance test of the coatings of Comparative Example 3 and Example 2 of the present invention;

[0030] Figure 7 This is a schematic diagram illustrating the self-assembly principle of the high weather-resistant transparent superhydrophobic coating of the present invention. Detailed Implementation

[0031] This invention provides a highly weather-resistant, transparent, superhydrophobic coating applicable to photovoltaic modules and new energy vehicles. It is prepared using modified cashew phenolic resin, hydrogen-containing silicone oil, and plexiglass microspheres. The mass ratio of the modified cashew phenolic resin, hydrogen-containing silicone oil, and plexiglass microspheres is 12-28:2-5:12-20.

[0032] The preparation of the high weather-resistant transparent superhydrophobic coating also requires catalysts and additives. The catalyst can be one or more of Speier catalyst, Karstedt catalyst or Tianan PT-50 catalyst. The additives are selected as the inducing agent perfluoroalkyl polyoxyethylene ether CF16400 (Jinan Qifu New Material Technology Co., Ltd., liquid, 100wt%) and the adhesion promoter JTW-311w (di(dioctyldiethanolamine pyrophosphoryl) ethylenediammonium titanate) (Nanjing Jingtianweidi Chemical Co., Ltd., liquid, 40wt%).

[0033] The specific preparation method of the high weather-resistant transparent superhydrophobic coating is as follows:

[0034] Dissolve 12-28 g of modified cashew phenolic resin in a composite solvent in a three-necked flask and stir at room temperature. Disperse 12-20 g of PMMA microspheres in 35-50 ml of ethyl acetate to form a suspension. Add the suspension dropwise to the three-necked flask and stir at 800 rpm for 1 hour. Add 2-5 g of hydrogen-containing silicone oil and stir at 1000 rpm for 2 hours. Finally, add 20-30 ppm of catalyst, 0.05-0.1 wt% (relative to the amount of PMMA microspheres added) of inducer, and 0.4 wt%-0.6 wt% (relative to the sum of the solid content of modified cashew phenolic resin, hydrogen-containing silicone oil, and PMMA microspheres) of adhesion promoter and stir at 1200 rpm for 0.5 hours.

[0035] The modified cashew phenolic resin is obtained by modifying cashew phenolic resin. The cashew phenolic resin is preferably purchased from Jinan Dahui Chemical Technology Co., Ltd., and is in powder form. The modification is preferably fluorination modification. It is prepared by cashew phenolic resin, N-containing silane coupling agent and isocyanate, with the mass ratio of the three being 72-80:24-30:4-14.

[0036] The modified cashew phenolic resin is prepared as follows:

[0037] Step 1: Preparation of aminated cashew phenolic resin:

[0038] Add 24-31 g KH550, 120-450 ml anhydrous 1,4-dioxane, 22-25 g 5,6-dichloropyrazine-2,3-dianitronidazole and 8-14 g anhydrous potassium phosphate (K3PO4) powder to the reaction vessel, heat the reaction mixture at 45-55 °C for 1-3 hours, and finally add 250-400 ml dimethyl sulfoxide and 60-85 g cashew phenolic resin. Heat the resulting mixture at 90-110 °C for 30 minutes to 1 hour.

[0039] Cool the reaction mixture to room temperature, then add 65-80 ml of acetic acid and 15-30 g of zinc. Heat at 70-90°C for 30 minutes to 1 hour. Dilute the reaction mixture with 110-420 ml of ethyl acetate, filter, and wash 2-3 times with deionized water. Dry the organic phase with anhydrous magnesium sulfate (MgSO4). Purify the crude residue by silica gel chromatography using an ethyl acetate / hexane mixture (1:1 mass ratio) as eluent to obtain aminated cashew phenolic resin.

[0040] The second step is the preparation of fluorinated cashew phenolic resin:

[0041] Add 72-80 g of aminated cashew phenolic resin to a dry three-necked flask, add 60-120 ml of anhydrous toluene, purge with nitrogen for 15-30 minutes to remove oxygen, install a condenser, connect an anhydrous CaCl2 drying tube to the top, and heat the oil bath to 60°C. o C. Stir until the resin is completely dissolved, then add 4-14 g of isocyanate to a constant pressure dropping funnel at 60°C. o Slowly add the solution dropwise to the resin solution at temperature C, and then raise the temperature to 80°C after adding the solution. o C, continue the reaction for 4-6 hours under nitrogen protection with magnetic stirring. After the reaction is complete, cool to 0°C. o C. Quench residual -NCO with 10 mL of anhydrous methanol. Pour into 200 mL of ice-cold methanol to precipitate, collect by filtration, wash three times with methanol to remove unreacted matter, 40 o The fluorinated cashew phenolic resin was obtained by drying at C for 48 hours.

[0042] The N-silane-containing coupling agent includes one or a combination of several of the following: 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropylmethyldiethoxysilane, or N-(2-aminoethyl-3-aminopropyl)methyldimethoxysilane.

[0043] The isocyanate may be one or more of perfluoroalkyl isocyanates, aromatic isocyanates, and aliphatic isocyanates.

[0044] The preparation mechanism of fluorinated cashew phenolic resin is as follows:

[0045]

[0046] The plexiglass microspheres can be one or more of polymethyl methacrylate microspheres, polystyrene microspheres, or polyvinyl chloride microspheres, preferably polymethyl methacrylate microspheres purchased from Beijing Zhongke Keyou Technology Co., Ltd., with a particle size of 80-120 nm.

[0047] The hydrogen-containing silicone oil includes one or more of hydrogen-terminated polydimethylsiloxane, partially hydrogen-terminated polydimethylsiloxane, hydrogen-terminated polydimethylmethylhydrosiloxane, or high-hydrogen-content silicone oil.

[0048] The preparation of the highly weather-resistant, transparent, superhydrophobic coating requires a composite solvent system, comprising a low-boiling-point solvent: a medium-to-high-boiling-point solvent: a high-boiling-point solvent in a mass ratio of 2-3:1-2:1-2. The low-boiling-point solvents include one or a mixture of ethyl acetate, ethanol, and acetone; the medium-to-high-boiling-point solvents include one or a mixture of propyl acetate or methyl isobutyl ketone; and the high-boiling-point solvents include one or a mixture of ethylene glycol ethyl ether acetate, propylene glycol methyl ether acetate, cyclohexanone, or amyl acetate.

[0049] This invention utilizes solvent evaporation as the driving force for self-assembly. It employs a composite system of low-boiling-point, medium-high-boiling-point, and high-boiling-point solvents, using a multi-stage evaporation process to provide the driving force for self-assembly. The low-boiling-point solvent evaporates rapidly in the initial stage, causing preliminary phase separation between the inducing agent perfluoroalkyl polyoxyethylene ether CF16400, PMMA microspheres, and the cashew phenolic resin-silicone rubber composite film-forming resin. The non-solvent gas phase induction and regulation of polymer chain segments and the inducing agent during solvent evaporation, along with precise control of the evaporation rate, triggers the self-assembly driving force. The medium-high-boiling-point solvent then evaporates at a moderate rate, providing a buffer time for phase separation and microsphere migration, ensuring the orderly stacking and network formation of the PMMA microspheres. Finally, the slow evaporation of the high-boiling-point solvent maintains a certain fluidity of the system, allowing the perfluoroalkyl polyoxyethylene ether CF16400 and the perfluorooctyl groups of the modified cashew phenolic resin to be fully enriched at the gas-liquid interface, inducing further microsphere arrangement and completing the construction of nano-network and fibrous structures. Through the synergistic effect of multi-stage solvent evaporation, this invention obtains a stable and fine micro-nano composite structure.

[0050] The present invention also provides a method for applying the above-mentioned highly weather-resistant transparent superhydrophobic coating, as follows:

[0051] The substrate was ultrasonically treated with anhydrous ethanol for 10 minutes, rinsed with deionized water, and dried with nitrogen. The high-weather-resistant, transparent, superhydrophobic coating was then applied using an air spray gun. Spraying parameters included: spraying distance, 20-25 cm; air pressure, 0.16-0.25 MPa; film thickness control, wet film thickness 45±5 μm, dry film thickness 15-20 μm. After spraying, the substrate was placed in a controlled temperature and humidity environment: the first stage was set at 55°C. o C, RH≤35%, 2-8 minutes; second stage set at 35°C. o C, RH≤60%, 10-15 minutes; third stage set at 85 o C, 30-60 minutes. After gradient heating, allow to stand at room temperature for 24 hours to obtain a highly weather-resistant, transparent, superhydrophobic coating.

[0052] The substrate can be glass, metal, or plastic.

[0053] This invention utilizes a modified cashew phenolic resin / silicone rubber composite film-forming resin to fill the voids between plexiglass microspheres, and constructs a stable network of "molecular layer—microsphere skeleton—film-forming resin" through the following multiple mechanisms, thereby endowing the coating with excellent mechanical stability and adhesion:

[0054] Structure locking is achieved through hydrosilylation: Under Speier catalyst and heating conditions, cashew phenolic resin undergoes a hydrosilylation reaction with hydrogen-containing silicone oil to generate stable silicon-carbon bonds. This reaction forms a "chemical bridge" between the microsphere surface and the resin matrix, effectively fixing and coating the PMMA microspheres. This allows the micro-nano structures formed by the self-assembly of the microspheres to remain stable for a long time, preventing them from detaching or collapsing during external forces or aging.

[0055] π–π stacking and weak interactions relieve stress: In the composite system, the benzene rings of cashew phenolic resin form a flexible network through π–π stacking and other weak interactions. This intermolecular stacking can disperse and absorb stress under external impact, preventing stress concentration that could lead to coating cracking. This significantly improves the impact resistance of the coating and solves the problem of insufficient mechanical strength in traditional organic coatings.

[0056] Multi-level hydrogen bond network enhances stability: The urea, amino, and phenolic hydroxyl groups in the composite film-forming system can form hydrogen bonds with different interfacial groups: strong hydrogen bonds with their own silane groups, the hydroxyl groups of perfluoroalkyl polyoxyethylene ether CF16400, and the hydroxyl groups on the surface of the metal substrate, significantly enhancing the coating's stability and adhesion; simultaneously, the amino groups form weak hydrogen bonds with other hydroxyl groups, further constructing a synergistic multi-level hydrogen bond network. This interwoven structure of strong and weak hydrogen bonds not only improves the overall toughness and stability of the coating but also enhances its ability to resist environmental stress under long-term conditions.

[0057] Coordination enhances adhesion to the substrate: The urea groups, vinyl groups, and silicon-oxygen bonds in the hydrogen-containing silicone oil in the composite system can coordinate with metal ions on the surface of the metal substrate. This coordination bond, in synergy with hydrogen bonds, significantly enhances the adhesion between the coating and the metal substrate (such as aluminum plate), avoiding the problem of traditional coatings peeling off under thermal cycling or mechanical impact due to insufficient adhesion.

[0058] The following embodiments and accompanying drawings are used to describe in detail the implementation of the present invention, so that the process of how the present invention uses technical means to solve technical problems and achieve technical effects can be fully understood and implemented accordingly.

[0059] Example 1 Fluorinated cashew phenolic resin

[0060] Add 28 g KH550, 400 ml anhydrous 1,4-dioxane, 23.88 g 5,6-dichloropyrazine-2,3-dianitronidazole, and 10 g anhydrous K3PO4 powder to a round-bottom flask equipped with a magnetic inlet. Heat the reaction mixture at 50 °C for 2 hours. Finally, add 350 ml DMSO and 75 g cashew phenolic resin, and heat the resulting mixture at 100 °C for 30 minutes.

[0061] The reaction mixture was cooled to room temperature, then 80 ml of acetic acid and 25 g of Zn powder were added, and the mixture was heated at 80 °C for 30 minutes. The reaction mixture was diluted with 400 ml of ethyl acetate, filtered, and washed three times with deionized water. The organic phase was dried over anhydrous magnesium sulfate, and the crude residue was purified by silica gel chromatography using an ethyl acetate / hexane mixture as eluent to obtain aminated cashew phenolic resin.

[0062] Add 22 g of aminated cashew phenolic resin to a dry three-necked flask. Add 50 mL of anhydrous toluene, purge with nitrogen for 15 minutes to remove oxygen, install a condenser, and connect anhydrous CaCl2 drying tube to the top. Heat the oil bath to 60°C. o C. Stir until the resin is completely dissolved. Add 11.5 g of perfluorooctyl ethyl isocyanate to a constant pressure dropping funnel, and stir at 60°C. o Slowly add the solution dropwise at temperature C over a period of 30 minutes. After addition, raise the temperature to 80°C. o Continue the reaction at C for 4-6 hours under nitrogen protection and with magnetic stirring throughout. After the reaction is complete, cool to 0°C in an ice bath. o C, add 1 mL of anhydrous methanol to quench residual -NCO. Pour in 200 mL of 0 o The precipitate was collected in ethyl acetate by filtration and washed three times with ethyl acetate to remove unreacted material. (45) o Drying at C for 12 hours yields fluorinated cashew phenolic resin.

[0063] Example 2: Transparent self-assembling superhydrophobic coating

[0064] A composite solvent system was prepared with anhydrous ethanol: butyl acetate: propylene glycol methyl ether acetate in a mass ratio of 2:2:1. 24 g of the fluorinated cashew phenolic resin prepared in Example 1 was weighed and dissolved in 100 g of the composite solvent in a three-necked flask, and stirred at room temperature. 3 g of hydrogen-terminated polydimethylsiloxane and 46.8 g of PMMA microsphere ethyl acetate suspension (containing 12 g of PMMA microspheres) were added, and the mixture was stirred at 1000 rpm for 2 hours. Finally, 25 ppm of Speier catalyst, 0.08 wt% of the inducing agent perfluoroalkyl polyoxyethylene ether CF16400 (relative to the amount of PMMA microspheres added), and 0.5 wt% of the adhesion promoter titanate JTW-311w (relative to the sum of the solid content of the modified cashew phenolic resin, containing hydrogen silicone oil, and PMMA microspheres) were added, and the mixture was stirred at 1200 rpm for 0.5 hours.

[0065] Comparative Example 1: Transparent self-assembling superhydrophobic coating 2

[0066] The same preparation method as in Example 2 was used, except that Craton SYLVARES™ 540 phenolic resin was used instead of the resin in Example 2. Example 1Fluorinated cashew phenolic resin.

[0067] Comparative Example 2

[0068] The same preparation method as in Example 2 was used, except that Dongyue Group's hydrophobic fumed silica DYSIL-B was used instead of PMMA microspheres.

[0069] Comparative Example 3

[0070] The same preparation method as in Example 2 was used, except that isophorone diisocyanate was used instead of perfluorooctyl ethyl isocyanate.

[0071] Comparative Example 4

[0072] The same preparation method as in Example 2 was used, except that a different composite solvent system was used.

[0073] Prepare a composite solvent system with butyl acetate: propylene glycol methyl ether acetate = 2:1.

[0074] Comparative Example 1 uses a common solvent-based phenolic resin in its film-forming resin composite system. Lacking double bonds, it cannot undergo hydrosilylation with hydrogen-containing silicone oil. Compared to Comparative Example 1, Comparative Examples 2-4 and Example 2 use cashew phenolic resin. Based on its unsaturated long carbon chains embedded in the phenolic resin network, it enhances energy dissipation and improves overall toughness while maintaining the original high-temperature resistance and high adhesion properties of phenolic resin. Compared to Example 2, Comparative Example 2 emphasizes that the self-assembly of PMMA microspheres is key to achieving coating transparency. Modified silica nanoparticles have poor induction ability from non-solvent gas phases, easily agglomerating, resulting in excessively large and uneven micro / nano structures that affect coating structural stability and produce Mie scattering. The difference between Comparative Example 3 and Example 2 lies in the different modifier (isocyanate) used for the aminated cashew phenolic resin. Compared to Example 2, Comparative Example 4 emphasizes that low-boiling-point solvents are crucial for microsphere self-assembly. The absence of low-boiling-point solvents leads to reduced coating volatility, hindering rapid phase separation, and causing excessive gravitational influence on the microspheres, easily resulting in a "gravitational settling effect." The porous structure that should have formed will collapse and aggregate due to the unevenness of the coating in the vertical direction, resulting in larger pore size, rougher and more uneven structure, which affects the construction of micro and nano structures on the coating surface and reduces superhydrophobic performance.

[0075] The experimental results are compared below:

[0076] The coatings prepared in Comparative Examples 1, 2, 3, 4, and 2 were sprayed onto metal substrates. After drying, the droplet shapes were analyzed using a DSA100 droplet shape analyzer. Figure 2As shown. Tests showed that the static contact angles of Comparative Example 1, Comparative Example 2, Comparative Example 3, Comparative Example 4 and Example 2 were 142.6°, 158.6°, 153.5°, 141.2° and 161.0°, respectively.

[0077] like Figure 7 As shown, with the continuous evaporation of the composite solvent, the concentration of perfluoroalkyl polyoxyethylene ether CF16400 in the solution gradually increases. To reduce unfavorable contact between the nonpolar and polar solvents, the hydrophobic, nonpolar fluorocarbon chain molecules aggregate inwards, while the polar polyoxyethylene ether segments tend to interact with solvent molecules, leading to the self-assembly of perfluoroalkyl polyoxyethylene ether CF16400 into micelles. Nanoscale fibrous or network-like secondary structures are formed through intermolecular forces, interspersed between PMMA microspheres. With further solvent evaporation, the PMMA microspheres tightly pack at the interface, forming a network induced by perfluoroalkyl polyoxyethylene ether CF16400, thus constructing the micro / nano structure of the coating surface.

[0078] Solvent evaporation leads to a cooling effect on the solution surface, causing uneven distribution of liquid temperature and concentration, thus generating a surface tension gradient. This surface tension pushes the solute in the solution upwards, promoting the formation of self-assembled structures. Due to their low surface energy, the fluorocarbon segments of perfluoroalkyl polyoxyethylene ether CF16400 and modified cashew phenolic resin are enriched at the gas-liquid interface. Perfluorooctyl segments are interspersed within the self-assembled structures, synergistically constructing the micro / nano structures of the coating surface.

[0079] To further examine the mechanical durability of the coating surface, abrasion resistance and water flow impact resistance tests were conducted. The abrasion resistance test used the number of abrasion cycles and static contact angle as indicators, employing 800-grit sandpaper, with the test surface facing down, and a 20g weight as the test load. Figure 3 As shown, a horizontal uniform force of 20 cm is applied as one friction cycle, and the change in contact angle is measured every 10 cycles.

[0080] like Figure 3 As shown, in Comparative Example 1, the static contact angle of the coating surface dropped sharply within 20 friction cycles, indicating severe damage to the coating surface. In Comparative Example 2, the coating surface maintained its superhydrophobic surface after 50 friction cycles, with the static contact angle remaining above 150°. After 60 cycles, the static contact angle of the coating surface in Comparative Example 2 was 146.6°. The coating surface in Comparative Example 3 maintained a static contact angle of 150° for 70 friction cycles. Although the coating surface in Comparative Example 4 did not achieve a superhydrophobic surface, its static contact angle showed no significant change within 20 friction cycles. The coating surface in Example 2 maintained its superhydrophobic surface over a longer range of friction resistance, up to 120 friction cycles. Water flow impact resistance test results are as follows... Figure 4As shown, the samples prepared in Comparative Example 2, Comparative Example 3, and Example 2 of this invention were subjected to an inclined water flow of 60 kPa. The test results were similar to those of the wear resistance test. The static contact angle of the sample in Comparative Example 2 decreased sharply with the water flow impact time. The coatings prepared in Comparative Example 3 and Example 2 showed no significant change in static contact angle within 60 minutes of water flow impact, exhibiting superior superhydrophobic properties. The coating prepared in Example 2 still retained superhydrophobic properties after 160 minutes of water flow impact. In practical applications, the impact pressure of raindrops is much less than 60 kPa, and the test environment is a fixed-point impact. Therefore, the highly weather-resistant transparent superhydrophobic coating prepared by this invention can maintain its properties for a longer period of time in outdoor rainfall environments.

[0081] In Comparative Example 1, the solubilized phenolic resin and high-hydrogen-content silicone oil form a composite film-forming resin system relying solely on weak interactions such as hydrogen bonds. This system is prone to brittleness and has relatively weak mechanical strength. In Comparative Example 2, the modified silica nanoparticles migrate to the gas-liquid surface during solvent evaporation, forming disordered and irregular aggregates that cause Mie scattering, resulting in a strong scattering effect on light. Furthermore, the microspheres protruding from the surface become direct stress points, with a relatively small contact area with the substrate, making them more susceptible to being ground away or impacted, thus permanently damaging the surface's micro / nano structure and causing hydrophobicity failure. In Comparative Example 4, the lack of a low-boiling-point solvent leads to insufficient evaporation power, failing to effectively drive convection. Due to surface tension and gravity, the porous structure that should have formed is prone to collapse and aggregation, resulting in larger pore sizes, a rougher and less uniform structure. This causes strong Mie scattering and fails to effectively trap air to form a stable gas-liquid interface, thus affecting superhydrophobicity. In the cashew phenolic resin / silicone rubber composite film-forming resin, urea groups, amino groups, and phenolic hydroxyl groups act as adhesion groups, adhering to the substrate through interactions such as anion-cation interactions, coordination interactions, and hydrogen bonds, thereby enhancing coating adhesion. Based on this, the coatings of Comparative Example 3 and Example 2 samples in the formulation of this invention both exhibit good wear resistance.

[0082] The spectral transmittance of Comparative Example 3 and Example 2 of the present invention was measured using a Shimadzu UV-3600i Plus ultraviolet-visible-near-infrared spectrophotometer in the wavelength range of 300-800 nm, and compared with high-transparency glass to quantitatively demonstrate that the high-weather-resistant transparent superhydrophobic coating of the present invention has high transparency. Figure 5As shown, the transmittance of the high-transparency glass blank sample can be maintained above 90% over a wide wavelength range. The high-transparency glass coated with the sample of Comparative Example 3 of this invention has a transmittance ≥80% under light irradiation in the wavelength range of 300-800 nm. The overall transmittance loss of the transparent superhydrophobic coating is about 11%, which is correspondingly smaller compared to other transparent superhydrophobic coating preparation schemes with better wear resistance. The high-transparency glass coated with the sample of Example 2 of this invention has a transmittance of about 90% under light irradiation in the wavelength range of 600-800 nm, which is comparable to that of the bare glass, exhibiting excellent transparency. Bénard convection also occurs during evaporation, further guiding the perfluoroalkyl polyoxyethylene ether CF16400 molecules to oriented arrangement at the interface, reducing interfacial tension, and inducing self-assembly units to form a uniform structure in the vertical direction.

[0083] The weather resistance of the highly weather-resistant transparent superhydrophobic coating of this invention was evaluated using an ultraviolet aging test chamber. The ultraviolet lamp power density was 2170 mW / cm², approximately 8 times stronger than the intensity of typical summer sunlight. The coating was continuously exposed for 60 minutes, and the static contact angle change of the coatings prepared for Comparative Example 3 and Example 2 was measured every 10 minutes. Figure 6 As shown, after the coating of Comparative Example 3 sample was exposed to ultraviolet light for 40 minutes, the static contact angle decreased, and the superhydrophobic properties could not be maintained. After the coating of Example 2 sample was exposed to ultraviolet light for 60 minutes, there was no obvious change in the coating under a microscopic scale, the static contact angle decreased slightly, and it still maintained excellent superhydrophobic properties.

[0084] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A highly weatherable transparent superhydrophobic coating, characterized in that: The modified cashew phenolic resin, organic glass microspheres and hydrogen-containing silicone oil are self-assembled by solvent evaporation to form a micro-nano composite network structure of "molecular layer-microsphere skeleton-film-forming resin".

2. The highly weatherable transparent superhydrophobic coating of claim 1, wherein: The mass ratio of the modified cashew phenolic resin, hydrogen-containing silicone oil and organic glass microspheres is 12-28:2-5:12-20.

3. The highly weatherable transparent superhydrophobic coating according to claim 1 or 2, wherein: The organic glass microspheres are one or a mixture of several of polymethyl methacrylate microspheres, polystyrene microspheres or polyvinyl chloride microspheres.

4. The highly weatherable transparent superhydrophobic coating according to claim 1 or 2, wherein: The particle size of the organic glass microspheres is between 80-120 nm.

5. The highly weatherable transparent superhydrophobic coating according to claim 1 or 2, wherein: The hydrogen-containing silicone oil can be one or a mixture of several of hydrogen-terminated polydimethylsiloxane, partially hydrogen-terminated polydimethylsiloxane, hydrogen-terminated polydimethylmethylhydrogen siloxane or high hydrogen-containing silicone oil.

6. The highly weatherable transparent superhydrophobic coating according to claim 1 or 2, wherein: The modified cashew phenolic resin is a fluorinated modified cashew phenolic resin.

7. The highly weatherable transparent superhydrophobic coating of claim 6, wherein: The preparation method of the fluorinated modified cashew phenolic resin comprises: First step, preparing an aminated cashew phenolic resin by using a N-containing silane coupling agent and cashew phenolic resin; Second step, using isocyanate to modify the aminated cashew phenolic resin prepared in the first step to prepare a fluorinated modified cashew phenolic resin.

8. The highly weatherable transparent superhydrophobic coating according to claim 1 or 2, wherein: The mass ratio of low-boiling-point solvent: medium-high-boiling-point solvent: high-boiling-point solvent in the composite solvent is 2-3:1-2:1-2.

9. A method for preparing the high-weather-resistant transparent super-hydrophobic coating according to any one of claims 1-8, characterized in that: The fluorinated cashew phenolic resin is weighed and dissolved in the composite solvent, stirred and dissolved at room temperature, the organic glass microspheres are dispersed in the organic solvent to form a suspension, then the fluorinated cashew phenolic resin solution is added dropwise, stirred uniformly, then the hydrogen-containing silicone oil is added, stirred, and finally the catalyst, inducer and adhesion promoter are added and stirred uniformly.

10. A coating method for the high-weather-resistant transparent super-hydrophobic coating according to any one of claims 1-8, characterized in that: First step, rinsing and blowing dry the substrate; Second step, the air spray gun is used to spray the super-hydrophobic coating, and after spraying, the substrate is placed in a controllable temperature and humidity environment: the first stage is set to 55 o C, RH≤35%, 2-8 minutes; the second stage is set to 35 o C, RH≤60%, 10-15 minutes; the third stage is set to 85 o C, 30-60 minutes. After the gradient temperature rise, the high-weather-resistant transparent super-hydrophobic coating can be obtained after standing at room temperature for 24 hours.

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