Super-hydrophobic insulating coating for power distribution equipment cabinet shell and preparation method

Abstract

The invention discloses a super-hydrophobic insulating coating for a power distribution equipment cabinet shell and a preparation method, and relates to the field of coatings. The bottom coating is a polyurethane acrylate elastomer layer which can be cured by ultraviolet light and contains an unreacted isocyanate group; the surface coating is formed by fixing a plurality of super-hydrophobic micro-nano structure units on the surface of the bottom coating, and the super-hydrophobic micro-nano structure units are arranged on the surface of the bottom coating in a single-layer manner; wherein the super-hydrophobic micro-nano structure unit is a hollow-core glass microsphere of which the surface is provided with a nano bulge structure. The super-hydrophobic insulating coating disclosed by the invention has insulativity and hydrophobicity and is long in service life.

Description

Technical Field

[0001] This invention relates to the field of coatings, and more specifically to a superhydrophobic insulating coating for the housing of power distribution equipment cabinets and its preparation method. Background Technology

[0002] With the rapid development of urbanization and power grids in my country, outdoor power distribution equipment is now ubiquitous in various complex environments. In coastal and humid areas, condensation easily forms inside the equipment cabinet due to temperature differences between the inside and outside, leading to decreased insulation performance and electrochemical corrosion of the metal casing, seriously threatening power supply safety and equipment lifespan. Meanwhile, in hot environments such as southern summers, the surface temperature of the equipment cabinet casing can reach 60-75℃, accelerating the aging of internal components due to overheating.

[0003] In existing technologies, to address the aforementioned issues, the industry typically attempts to apply a superhydrophobic coating to the surface of the power distribution equipment cabinet housing. Superhydrophobic coatings possess excellent hydrophobicity and self-cleaning capabilities, and can also significantly reduce internal temperature variations, preventing condensation.

[0004] Several superhydrophobic coating solutions exist in the prior art. For example, patent CN202411164968.8 discloses a method for preparing a high-wear-resistant superhydrophobic coating and the coating itself, which uses a composite of hydrophobic nano-silica, glass fiber, and resin, and enhances wear resistance through electrostatic flocking. However, its process is complex and does not take into account the insulation requirements of electrical equipment, making it prone to failure. Patent CN202510498359.4 discloses a composite coating, but its surface layer is usually a continuous brittle micro-nano ceramic structure, which is difficult to adapt to the significant deformation of metal cabinets caused by thermal expansion and contraction, and is prone to cracking and failure. Patent CN202510943924.3 discloses a high-performance superhydrophobic coating, which focuses on improving weather resistance and algae prevention, but the construction process is cumbersome, the insulation performance is poor, and the coating has a short service life.

[0005] While the aforementioned technologies can form superhydrophobic coatings, they generally suffer from limitations such as limited performance and short coating lifespan. Therefore, there is a need to develop a new type of superhydrophobic coating. Summary of the Invention

[0006] This invention aims to address one of the technical problems in related technologies to a certain extent. To this end, this invention provides a superhydrophobic insulating coating for power distribution equipment cabinet housings and its preparation method, which can balance insulation and hydrophobicity while maintaining a long service life.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A superhydrophobic insulating coating for the housing of a power distribution equipment cabinet includes a primer coating and a topcoat coating; The base layer is a polyurethane acrylate elastomer layer that can be cured by ultraviolet light and contains unreacted isocyanate groups; The topcoat is formed by fixing multiple superhydrophobic micro / nano structure units to the surface of the bottom coating, and the superhydrophobic micro / nano structure units are arranged in a single layer on the surface of the bottom coating. The superhydrophobic micro / nano structure unit is a hollow glass microsphere with a nano-protrusion structure on its surface.

[0008] In this application, nano-protrusion structures are formed on the surface of hollow glass microspheres to make them superhydrophobic micro / nano-structure units. These superhydrophobic micro / nano-structure units are arranged in a single layer on the surface of the base coating, forming a regular superhydrophobic surface, giving the coating excellent superhydrophobicity and scratch resistance. Through chemical reactions between the active groups on the surface of the superhydrophobic micro / nano-structure units and unreacted isocyanate groups, vinyl groups, etc., in the base coating, strong chemical bonds are formed, resulting in a tightly bonded composite coating between the top coating and the base coating. Simultaneously, the high elasticity of the base coating allows the entire coating to deform without cracking when the substrate expands thermally, solving the problem of coating failure caused by metal thermal expansion. The thermal insulation and photothermal reflection functions of the neatly arranged hollow glass microspheres in the top coating, combined with the optional addition of ultrafine hollow glass microspheres in the base coating, jointly endow the prepared composite coating with excellent thermal insulation and flame retardancy, giving it comprehensive properties of superhydrophobicity, thermal insulation, flame retardancy, and insulation. In addition, the base coating contains unreacted isocyanate groups, which can undergo a secondary curing reaction with environmental moisture to generate a hydrophobic polyurethane urea structure, further enhancing the density and water resistance of the insulating coating and maintaining its insulation properties for a long time.

[0009] Optionally, the method for forming the superhydrophobic micro / nano structure unit includes the following steps: Surface hydroxylation treatment of hollow glass microspheres; Hollow glass microspheres after hydroxylation were pretreated with silane coupling agents. Pretreated hollow glass microspheres were immersed in organosilicon-inorganic silica sol and dried by rotary evaporation to form nano-protrusion structures on the hollow glass microspheres. Surface hydrophobic modification of hollow glass microspheres with nanoprotrusions was performed using organofluorosilane coupling agents.

[0010] By using chemical bonding (silanes, fluorosilanes) rather than physical adsorption, low surface energy materials are permanently grafted onto a stable nanostructure constructed via the sol-gel method, ensuring excellent chemical and mechanical stability of the coating layer when subjected to water flow, friction, and even certain temperature changes. Additionally, rotary evaporation is performed in a rotary evaporator.

[0011] Optionally, the organosilicon-inorganic silica sol raw material composition comprises, by weight, the following components: 100-200 parts anhydrous ethanol, 30-50 parts tetraethyl silicate, 5-20 parts ammonia water at a concentration of 25%, 0-5 parts silane coupling agent, and 0-20 parts neutral silica sol at a concentration of 30%; wherein the silane coupling agent is selected from one or more of γ-aminopropyltriethoxysilane, vinyltriethoxysilane, vinyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-methacryloyloxypropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, methacryloyloxysilane, and chloropropylsilane.

[0012] Using tetraethyl silicate as the main silicon source, a controlled hydrolysis and condensation reaction occurs under the catalysis of anhydrous ethanol solvent and weakly alkaline ammonia. Ammonia provides an alkaline environment, catalyzing the hydrolysis of tetraethyl silicate to generate silanols, which then condense to form nanoscale silica primary particles or oligomers. By controlling the concentration of tetraethyl silicate, the amount of ammonia, and the reaction conditions, the particle size of the generated silica particles and the viscosity of the sol can be controlled, laying the foundation for the subsequent formation of a uniform coating layer on the microsphere surface.

[0013] Optionally, the preparation process of the organosilicon-inorganic silica sol includes: mixing anhydrous ethanol, tetraethyl silicate, ammonia water and silane coupling agent, heating in a water bath at 50-80°C, and reacting at a stirring speed of 350 rpm for 2-6 hours to obtain a solution; after the reaction is completed, rotary evaporating the aforementioned solution at room temperature until the solution is neutral to obtain nano-silica sol; finally, heating the neutral silica sol and adding it to the nano-silica sol and stirring evenly.

[0014] A temperature range of 50-80℃ provides sufficient energy to accelerate the hydrolysis and initial condensation of tetraethyl silicate, generating nano-silica nuclei and oligomers, while avoiding excessively high temperatures that could lead to overly rapid reactions, particle agglomeration, or excessive evaporation of the solvent ethanol. This ensures the formation of a nanoparticle sol with a narrow particle size distribution and good dispersibility. Continuous mechanical stirring ensures heat transfer and material uniformity in the reaction system, preventing excessively high local concentrations that could cause abnormal particle growth or gelation, thus obtaining a uniform and stable sol.

[0015] Optionally, the thickness of the base coating is 50% to 120% of the diameter of the superhydrophobic micro / nano structure unit. The raw material composition of the base coating, by weight, includes the following components: 40-70 parts of polyurethane acrylate prepolymer, 0-20 parts of polyurethane acrylate oligomer, 10-30 parts of norborneol methacrylate, 5-30 parts of isooctyl acrylate, 1-2 parts of photoinitiator, 0-20 parts of ultrafine hollow glass microspheres, 0-3 parts of rutile titanium dioxide, 1-3 parts of alkoxy-containing hindered amine light stabilizer, 0-2 parts of nano zinc oxide, 0.1-0.5 parts of leveling agent, and 0.2-5 parts of tackifier. The polyurethane acrylate prepolymer is formed by the reaction polymerization of a polyester polyol with aliphatic isocyanate prepolymer and hydroxyethyl acrylate. The polyurethane acrylate prepolymer has a molecular weight of 1000-7000 and contains 0.5% to 2% by mass of unreacted isocyanate groups.

[0016] The thickness of the primer coating is 50% to 120% of the diameter of the superhydrophobic micro / nano structural unit (i.e., hollow glass microspheres). This ensures that the primer coating can form strong mechanical interlocking and chemical bonding with the microspheres while avoiding excessive thickness that could lead to stress concentration. This ensures that the insulating coating can deform with the metal substrate without cracking. The primer coating mainly uses polyurethane acrylate prepolymer with a molecular weight of 1000-7000, guaranteeing the application viscosity and final elasticity. After UV curing, the unreacted isocyanate groups can undergo secondary cross-linking with moisture in the environment, making the coating network denser and improving water resistance, strength, and chemical bonding strength to the microspheres.

[0017] Optionally, the raw material composition of the primer layer comprises, by weight, the following components: 50-55 parts of polyurethane acrylate prepolymer, 5-10 parts of polyurethane acrylate oligomer, 20-30 parts of norborneol methacrylate, 10-15 parts of isooctyl acrylate, 1-1.5 parts of photoinitiator TPO, 0-5 parts of ultrafine hollow glass microspheres, 0-2 parts of rutile titanium dioxide, 1-2 parts of alkoxy-containing hindered amine light stabilizer, 0-1 part of nano zinc oxide, 0.1-0.5 parts of leveling agent, and 0.2-3 parts of tackifier; the polyurethane acrylate prepolymer has a molecular weight of 3000-5000 and contains 0.5%~1% by mass of unreacted isocyanate groups.

[0018] Each component has been optimized within a narrower range to ensure that the coating achieves sufficient heat insulation, reflection, UV shielding and application performance, while avoiding the potential negative impact of excessive addition on coating transparency, mechanical properties and interfacial bonding.

[0019] Optionally, the tackifier is one or more of organic montmorillonite, inorganic gel, and inorganic clay sheet; the hindered amine light stabilizer with alkoxy group includes one or more of Eversorb 60, Eversorb 90, Eversorb 91, HS-625, and Tinuvin PUR866.

[0020] Hindered amine light stabilizers with alkoxy groups contain both hindered amine groups and alkoxy groups. During coating service, the hindered amine groups can efficiently capture polymer free radicals initiated by ultraviolet light, interrupting the photo-oxidative degradation chain reaction. Simultaneously, their alkoxy structure enhances compatibility with resins such as polyurethane and acrylate, reducing the migration and volatilization loss of the stabilizer itself. Compared to ordinary hindered amine light stabilizers, hindered amine light stabilizers with alkoxy groups exhibit superior longevity and retention in polyurethane systems.

[0021] Furthermore, the present invention also provides a method for preparing a superhydrophobic insulating coating, wherein the superhydrophobic insulating coating includes the superhydrophobic insulating coating for the housing of power distribution equipment cabinets as described in any one of the preceding claims, and the preparation method includes the following steps: A polyurethane acrylate primer composition containing unreacted isocyanate groups is sprayed onto the surface of the power distribution equipment cabinet housing to form a wet primer film; Before the wet primer film is cured, multiple powdered superhydrophobic micro-nano structure units are applied to the surface of the primer film by electrostatic spraying and formed into a single layer arrangement. The coating after electrostatic spraying is irradiated with ultraviolet light to cause the primer composition to undergo initial curing and fix the superhydrophobic micro-nano structure unit to form the top coating. Unreacted isocyanate groups in the initially cured coating react with moisture in the environment, undergoing a second curing process.

[0022] First, a liquid primer composition containing unreacted isocyanate groups is sprayed onto the surface of the power distribution equipment cabinet housing to form a continuous and uniform wet film. Before the wet film cures, powdered superhydrophobic micro / nano structural units are applied by electrostatic spraying. Electrostatic attraction causes negatively charged powder particles to be uniformly adsorbed onto the positively charged wet film surface, achieving a monolayer or quasi-monolayer arrangement. At this point, the lower half of the powder particles is embedded in the wet film, while the upper half is exposed. The resin in the wet film initially contacts and wets the active groups (such as amino and hydroxyl groups) on the surface of the microspheres, laying the foundation for subsequent chemical bonding. Subsequently, the composite wet film is irradiated with ultraviolet light, causing the wet primer film to transform from a liquid to a solid elastomer, while simultaneously mechanically locking the embedded surface layer micro / nano structural units.

[0023] Optionally, the ultraviolet irradiation uses a UV-A band light source with a power of not less than 2000W, and the curing time is 5-30 minutes; the voltage of the electrostatic spraying is 40-80 kV.

[0024] The wavelength range of UV-A ultraviolet light is 315 nm to 400 nm to provide sufficient light intensity and penetration depth to the coating, avoiding incomplete curing. The voltage for electrostatic spraying is 40-80 kV. Under this electric field, corona discharge occurs at the tip of the spray gun electrode, ionizing the air and generating a large number of ions that adhere to the surface of the powder particles, charging them. 40 kV is the lower threshold that allows the microspheres to be fully charged and generate a sufficient electric field to overcome gravity and inertia, enabling directional flight and adsorption onto the surface of the wetted primer with the opposite charge. 80 kV is the upper limit, taking into account equipment safety, avoiding air breakdown, and preventing excessive repulsion between powder particles due to excessive charge, which could affect the tight arrangement of the single layer. This voltage range ensures high powder deposition efficiency, uniform distribution, and the formation of ideal single-layer or quasi-single-layer structures.

[0025] Optionally, the primer composition is sprayed using a self-spraying pressure can or a pneumatic pressure tank, and self-leveling is performed for 10-15 minutes after spraying; after electrostatic spraying, any superhydrophobic micro / nano structural units that are not firmly attached are removed.

[0026] Use a self-pressurized spray can or pneumatic pressure tank for the application of the primer coating to provide a stable, controllable, and well-atomized spraying effect. Allow the primer to self-level for 10-15 minutes after spraying. During this period, the wet primer coating automatically smooths out surface undulations such as orange peel and ripples caused by spraying under surface tension. Simultaneously, air bubbles trapped within the coating escape, resulting in a uniform, smooth, and defect-free primer coating. Excess superhydrophobic micro / nano structure unit powder may remain after electrostatic spraying. If not removed, this powder cannot form effective bonds with the primer coating during subsequent UV curing, easily detaching during coating service life and affecting its lifespan.

[0027] These features and advantages of the present invention will be disclosed in detail in the following specific embodiments and accompanying drawings. The preferred embodiments or means of the present invention will be shown in detail in conjunction with the accompanying drawings, but are not intended to limit the technical solutions of the present invention. In addition, each of these features, elements and components appearing in the following text and drawings is a plurality of, and different symbols or numbers are used for convenience of representation, but all represent parts with the same or similar construction or function. Attached Figure Description

[0028] The present invention will be further described below with reference to the accompanying drawings: Figure 1 The image shows an electron microscope image of the superhydrophobic micro / nano structure unit in Example 1 of this invention. Figure 2 This is an electron microscope image of the nanoprotrusion structure of the superhydrophobic micro / nano structural unit in Example 1 of this invention; Figure 3 The elongation at break and tensile strength of the primer layer formed by curing alone in Example 1 of this invention. Figure 4 This is a schematic diagram showing the test results of the static water contact angle of the superhydrophobic insulating coating prepared in Example 1 of the present invention. Detailed Implementation

[0029] The embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described are intended to explain the present invention and should not be construed as limiting the invention.

[0030] The terms "an embodiment," "example," or "trademark" used in this specification refer to a particular feature, structure, or characteristic described in connection with the embodiment itself that may be included in at least one embodiment disclosed in this patent. The phrase "in an embodiment" appearing in various places throughout the specification does not necessarily refer to the same embodiment.

[0031] Example: This embodiment provides a superhydrophobic insulating coating for the housing of a power distribution equipment cabinet, including a base coating and a top coating; the base coating is a polyurethane acrylate elastomer layer that can be cured by ultraviolet light and contains unreacted isocyanate groups; the top coating is formed by fixing multiple superhydrophobic micro-nano structure units to the surface of the base coating, and the superhydrophobic micro-nano structure units are arranged in a single layer on the surface of the base coating; wherein, the superhydrophobic micro-nano structure units are hollow glass microspheres with nano-protrusion structures on the surface.

[0032] In this embodiment, the superhydrophobic insulating coating for the power distribution equipment cabinet housing is a composite coating consisting of a base coat and a top coat layered together. The top coat utilizes the advantages of hollow glass microspheres—low density, easy dispersion, high mechanical strength, good water resistance, chemical inertness, and smooth surface—to improve the superhydrophobicity, corrosion resistance, high hardness, and scratch resistance of the resulting composite coating. The hollow glass microspheres constituting the top coat, due to their hollow structure, provide excellent thermal insulation. Through the thermal insulation and photothermal reflection functions of the neatly arranged hollow glass microspheres in the top coat, the thermal insulation performance of the resulting superhydrophobic insulating coating is significantly improved, isolating heat conduction during fires. This allows the coating to simultaneously possess superhydrophobic, thermal insulation, flame retardant, and insulating properties (it can be understood that insulation is an inherent property of the hollow glass microspheres), making it highly suitable for thermal insulation applications in power system distribution equipment. The base coat utilizes the UV-curable properties of polyurethane acrylate, as well as its high adhesion and high elasticity, to improve the workability and overall performance of the composite coating. In this embodiment, the superhydrophobic insulating coating is a composite structure consisting of a rigid functional unit topcoat and a highly elastic adhesive basecoat. The topcoat provides a durable physical and chemical barrier, while the basecoat acts as a stress buffer layer, absorbing the deformation energy of the metal casing of the power distribution equipment cabinet caused by thermal expansion and contraction, thereby preventing coating cracking from the source.

[0033] Using hollow glass microspheres as the basic unit, the microspheres are arranged in a single layer on the surface of the undercoat, forming a rough structure at the microscale. The microsphere layer first constructs a layer of micron-sized protrusions on the surface of the power distribution equipment cabinet housing. When water droplets fall, they can only make limited contact with the tops of the microspheres, with most of the area being air, reducing the solid-liquid contact area. Furthermore, to improve the hydrophobicity of the coating, the surface of the hollow glass microspheres in this embodiment also has a nano-protrusion structure, i.e., a lotus leaf-inspired structure, further enhancing the surface roughness. Therefore, water droplets can be held at the top of the nano-protrusion structure. In this state, the water droplets have a very large contact angle (typically greater than 150°) and a very small roll-off angle, making them very easy to roll off. This fundamentally prevents condensation formation and cuts off the electrolyte channel required for electrochemical corrosion, achieving long-term corrosion protection. Compared to existing technologies that directly construct micro-nano rough structures on substrates, this application constructs a lotus leaf-like nanoprotrusion biomimetic structure on the surface of hollow glass microspheres, an independent carrier. This allows each hollow glass microsphere to become a multifunctional structural unit integrating heat insulation, electrical insulation, high hardness, and superhydrophobicity. Furthermore, a polyurethane acrylate undercoat containing unreacted isocyanate groups is selected, meaning some trace amounts of isocyanate-based active groups are reserved. These active groups can further crosslink with trace amounts of moisture in the environment to form a hydrophobic polyurethane urea structure, effectively preventing the penetration of trace amounts of moisture into the coating during equipment use and maintaining the coating's insulation properties.

[0034] The method for forming superhydrophobic micro / nano structural units includes the following steps: surface hydroxylation treatment of hollow glass microspheres; pretreatment of the hydroxylated hollow glass microspheres with a silane coupling agent; immersion of the pretreated hollow glass microspheres in an organosilicon-inorganic silica sol, followed by rotary evaporation drying to form nanoprotrusion structures on the hollow glass microspheres; and surface hydrophobic modification of the hollow glass microspheres with nanoprotrusions using an organofluorosilane coupling agent.

[0035] In this embodiment, the hydroxylation treatment is performed using a highly oxidizing piranha solution (a mixture of concentrated sulfuric acid and hydrogen peroxide). Specifically, hollow glass microspheres are immersed in a piranha etching solution prepared by mixing 98% concentrated sulfuric acid solution and 30% hydrogen peroxide solution in a volume ratio of 3:1. This introduces a large number of highly reactive silanol groups onto the surface of the hollow glass microspheres (mainly composed of silicon dioxide), increasing the chemical energy of the microsphere surface and laying the foundation for subsequent chemical bonding with the silane coupling agent. The silane coupling agent pretreatment involves immersing the hydroxylated hollow glass microspheres in a silane coupling agent containing active groups such as amino or epoxy groups to generate a silane molecular layer on the microsphere surface. The alkoxy group at one end of the silane coupling agent hydrolyzes and undergoes a condensation reaction with the silanol groups on the microsphere surface, forming a strong Si-O-Si covalent bond; the organic functional groups at the other end are introduced onto the microsphere surface, enhancing the chemical affinity and adhesion between the microspheres and the underlying coating.

[0036] Pretreated microspheres were immersed in an organosilicon-inorganic silica sol to form nanoprotrusion structures via a sol-gel method. During rotary evaporation drying, the organosilicon-inorganic silica sol gradually lost water and concentrated, causing nano-silica particles to deposit, aggregate, and further condense on the surface of the microspheres. Ultimately, through a sol-gel transition, a porous silica gel layer with nanoscale roughness was grown and solidified in situ on the microsphere surface, thus forming the desired nanoprotrusion structure. Finally, the microspheres with nanoprotrusions were treated with an organofluorosilane coupling agent with low surface energy and long fluorocarbon chains (such as heptadecafluorodecyltriethoxysilane). The siloxane ends of the fluorosilane reacted with the silanol groups on the surface of the protrusion structure to form chemical bonds, covalently grafting the extremely low surface energy fluorocarbon chains onto the microsphere surface. Thus, the microspheres simultaneously possess a micrometer-scale spherical substrate, a nanometer-scale protruding rough structure, and low surface energy chemical modification, conforming to the Cassie-Baxter superhydrophobic model, becoming independent functional units with stable superhydrophobicity. This application permanently grafts low surface energy materials onto a stable nanostructure constructed via the sol-gel method through chemical bonding (silanes, fluorosilanes) rather than physical adsorption, ensuring excellent chemical and mechanical stability of the coating layer when subjected to water flow, friction, and even certain temperature changes. Furthermore, rotary evaporation is performed in a rotary evaporator.

[0037] The selected hollow glass microspheres have a particle size of 20-500 μm, a wall thickness of 1-5 μm, and a density of 0.12-1.6 g / cm³. 3 The thermal conductivity is 0.025-0.073 W / (m·K), and the floating rate is required to be ≥90% (reflecting the integrity of the hollow structure). Preferably, the hollow glass microspheres have a particle size of 50-250 μm. The organosilicon-inorganic silica sol raw material composition comprises, by weight, the following components: 100-200 parts anhydrous ethanol, 30-50 parts tetraethyl silicate, 5-20 parts 25% ammonia water, 0-5 parts silane coupling agent, and 0-20 parts 30% neutral silica sol; wherein the silane coupling agent is selected from one or more of γ-aminopropyltriethoxysilane, vinyltriethoxysilane, vinyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-methacryloyloxypropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, methacryloyloxysilane, and chloropropylsilane.

[0038] In this embodiment, ammonia water, using tetraethyl silicate as the main silicon source, undergoes a controlled hydrolysis and condensation reaction under the catalysis of anhydrous ethanol solvent and weakly alkaline ammonia water. Ammonia water provides an alkaline environment, catalyzing the hydrolysis of tetraethyl silicate to generate silanols, which then condense to form nanoscale silica primary particles or oligomers. By controlling the concentration of tetraethyl silicate, the amount of ammonia water, and the reaction conditions, the particle size of the generated silica particles and the viscosity of the sol can be controlled, laying the foundation for the subsequent formation of a uniform coating layer on the surface of the microspheres. Furthermore, the silane coupling agent and the neutral silica sol (containing the already formed nanoscale silica particles) constitute a hybrid system combining sol-gel and particle composites. Anhydrous ethanol, as a solvent, can dissolve both tetraethyl silicate and the silane coupling agent and is miscible with water, ensuring a homogeneous reaction system; its amount (100-200 parts) directly affects the concentration of each reactant. In summary, the silica layer generated in situ on the microsphere surface through the sol-gel process is bonded to the microsphere substrate (both silicate materials) by chemical bonds (Si-O-Si), resulting in strong adhesion. The introduction of organic components (from silane coupling agents) gives the gel network a certain degree of flexibility, buffering curing shrinkage stress and avoiding the brittle cracking problem of pure inorganic silica layers, thus ensuring the integrity of the nanoprotrusion structure. Furthermore, by selecting silane coupling agents with different functional groups, specific chemical properties can be customized to the nanoprotrusion surface. For example, the introduction of γ-aminopropyl groups provides amino groups that react with the unreacted isocyanate groups in the undercoat; the introduction of γ-methacryloyloxy groups provides carbon-carbon double bonds that participate in the curing copolymerization of the undercoat, achieving strong chemical bonding between the topcoat functional units and the undercoat at the nanoscale, improving the interlayer adhesion and durability of the composite coating. The sol system at this formulation ratio exhibits good stability and, after subsequent rotary evaporation and drying, can be transformed into a uniformly thick nanostructure coating layer, providing a reliable raw material guarantee for the preparation of superhydrophobic micro / nanostructure units. The final structure formed on the hollow glass microspheres is not a purely inorganic nanoprotrusion, but an organic-inorganic hybrid nanocomposite structure. The inorganic part (derived from tetraethyl silicate and silica sol) provides hardness, heat resistance, and structural stability; the organic part (derived from silane coupling agent) provides flexibility, reactivity, and compatibility with the organic undercoating. This allows the final coating to maintain the roughness and low surface energy required for superhydrophobicity, while also possessing interfacial properties that allow it to adapt to the elastic deformation of the undercoating without pulverizing or peeling off.

[0039] The preparation process of organosilicon-inorganic silica sol includes: mixing anhydrous ethanol, tetraethyl silicate, ammonia water and silane coupling agent, heating in a water bath at 50-80℃, and reacting at a stirring speed of 350 rpm for 2-6 hours to obtain a solution; after the reaction is completed, the solution is rotary evaporated at room temperature until the solution is neutral to obtain nano-silica sol; finally, the neutral silica sol is heated and added to the nano-silica sol and stirred evenly.

[0040] In this embodiment, the temperature range of 50-80°C provides sufficient energy to accelerate the hydrolysis and initial condensation of tetraethyl silicate, generating nano-silica nuclei and oligomers, while avoiding excessively rapid reactions, particle agglomeration, or excessive evaporation of the solvent ethanol due to excessively high temperatures. This ensures the formation of a nanoparticle sol with a narrow particle size distribution and good dispersibility. Continuous mechanical stirring ensures heat transfer and material uniformity in the reaction system, preventing abnormal particle growth or gelation caused by excessively high local concentrations, thus obtaining a uniform and stable sol. After the reaction, unreacted ammonia and the byproduct ethanol remain in the system. Low-boiling-point ethanol and ammonia are selectively removed by rotary evaporation at room temperature. The neutral silica sol provides uniformly sized and highly stable silica nanoparticles. After mixing, under heating and stirring, the active particles and the surface of the pre-formed particles interact and connect through condensation or hydrogen bonding between silanol groups, making the final organosilicon-inorganic silica sol more compact.

[0041] The thickness of the base coating is 50% to 120% of the diameter of the superhydrophobic micro / nano structure unit. The raw material composition of the base coating, by weight, includes the following components: 40-70 parts of polyurethane acrylate prepolymer, 0-20 parts of polyurethane acrylate oligomer, 10-30 parts of norborneol methacrylate, 5-30 parts of isooctyl acrylate, 1-2 parts of photoinitiator, 0-20 parts of ultrafine hollow glass microspheres, 0-3 parts of rutile titanium dioxide, 1-3 parts of alkoxy-containing hindered amine light stabilizer, 0-2 parts of nano zinc oxide, 0.1-0.5 parts of leveling agent, and 0.2-5 parts of tackifier. Among them, the polyurethane acrylate prepolymer is formed by the reaction polymerization of polyester polyol with aliphatic isocyanate prepolymer and hydroxyethyl acrylate. The polyurethane acrylate prepolymer has a molecular weight of 1000-7000 and contains 0.5% to 2% by mass of unreacted isocyanate groups.

[0042] In this embodiment, the thickness of the base coating is 50%-120% of the diameter of the superhydrophobic micro / nano structural unit (i.e., hollow glass microspheres). This ensures that the base coating can form strong mechanical interlocking and chemical bonding with the microspheres while avoiding excessive thickness that could lead to stress concentration. This ensures that the insulating coating can deform with the metal substrate without cracking. The base coating is primarily made of polyurethane acrylate prepolymer with a molecular weight of 1000-7000, guaranteeing the application viscosity and final elasticity. Unreacted isocyanate groups can undergo secondary cross-linking with moisture in the environment after UV curing, making the coating network denser and improving water resistance, strength, and chemical bonding strength to the microspheres. In addition, polyurethane acrylate oligomers can enhance the adhesion and toughness of the base coating; norborneol methacrylate and isooctyl acrylate can act as reactive diluents to adjust viscosity and cured film properties; ultrafine hollow glass microspheres further enhance the thermal insulation of the base coating and reduce internal stress; rutile titanium dioxide provides opacity and reflective thermal insulation; alkoxylated hindered amine light stabilizers and nano-zinc oxide synergistically resist UV aging; leveling agents and tackifiers optimize film appearance and storage stability, respectively. It should be noted that the particle size of the ultrafine hollow glass microspheres should be much smaller than that of hollow glass microspheres.

[0043] The raw material composition of the primer layer, by weight, includes the following components: 50-55 parts of polyurethane acrylate prepolymer, 5-10 parts of polyurethane acrylate oligomer, 20-30 parts of norborneol methacrylate, 10-15 parts of isooctyl acrylate, 1-1.5 parts of photoinitiator TPO, 0-5 parts of ultrafine hollow glass microspheres, 0-2 parts of rutile titanium dioxide, 1-2 parts of alkoxy-containing hindered amine light stabilizer, 0-1 part of nano zinc oxide, 0.1-0.5 parts of leveling agent, and 0.2-3 parts of tackifier; the polyurethane acrylate prepolymer has a molecular weight of 3000-5000 and contains 0.5%~1% by mass of unreacted isocyanate groups.

[0044] In this embodiment, the proportions of each component can be further refined within the aforementioned formulation framework. By setting the polyurethane acrylate prepolymer content to 50-55 parts and narrowing the molecular weight range to 3000-5000, the base coating is ensured to maintain high elasticity while exhibiting better flowability and curing rate. The residual isocyanate group content is limited to 1%-0.5%, minimizing the risk of coating porosity or storage instability due to excessive residual activity, while ensuring sufficient secondary curing reinforcement. Introducing 5-10 parts of polyurethane acrylate oligomer effectively enhances the toughness and adhesion of the resin system and compensates for curing shrinkage. The reactive diluent monomer uses a high proportion of norborneol methacrylate (20-30 parts) and isooctyl acrylate (10-15 parts), the former imparting higher hardness and heat resistance to the coating, while the latter providing excellent flexibility and internal plasticizing effect. Each component has been optimized within a narrower range to ensure that the coating achieves sufficient heat insulation, reflection, UV shielding and application performance, while avoiding the potential negative impact of excessive addition on coating transparency, mechanical properties and interfacial bonding.

[0045] The tackifier is one or more of organic montmorillonite, inorganic gel, and inorganic clay sheet; the hindered amine light stabilizer with alkoxy group includes one or more of Eversorb 60, Eversorb 90, Eversorb 91, HS-625, and Tinuvin PUR866.

[0046] In this embodiment, the organic montmorillonite, inorganic gel, or inorganic clay flakes are all materials with special lamellar or network structures. In the coating system, they can form reversible "kagawa structures" or gel networks through physical interactions (such as hydrogen bonding and electrostatic interactions). This structure imparts a high viscosity to the base coat when stationary, preventing solid filler sedimentation. However, when subjected to shear forces (such as stirring or spraying), the structure is disrupted, and the viscosity rapidly decreases, thus achieving good thixotropy and anti-settling properties, ensuring the stability of the coating during storage, and providing excellent leveling and controllable film thickness during application. The hindered amine light stabilizer molecule contains hindered amine groups and alkoxy groups. During coating service, the hindered amine groups can efficiently capture polymer free radicals induced by ultraviolet light, interrupting the photo-oxidative degradation chain reaction. Simultaneously, its alkoxy structure enhances compatibility with resins such as polyurethane acrylates, reducing the migration and volatilization loss of the stabilizer itself. Compared to ordinary hindered amine light stabilizers, the hindered amine light stabilizer with alkoxy groups exhibits superior longevity and retention in polyurethane systems.

[0047] Furthermore, this embodiment also provides a method for preparing a superhydrophobic insulating coating, wherein the superhydrophobic insulating coating includes the superhydrophobic insulating coating for the housing of the power distribution equipment cabinet as described above, and the preparation method includes the following steps: A polyurethane acrylate primer composition containing unreacted isocyanate groups is sprayed onto the surface of the power distribution equipment cabinet housing to form a wet primer film; Before the wet primer film is cured, multiple powdered superhydrophobic micro-nano structure units are applied to the surface of the primer film by electrostatic spraying and formed into a single layer arrangement. The coating after electrostatic spraying is irradiated with ultraviolet light to cause the primer composition to undergo initial curing and fix the superhydrophobic micro-nano structure unit to form the top coating. Unreacted isocyanate groups in the initially cured coating react with moisture in the environment, undergoing a second curing process.

[0048] In this embodiment, a liquid primer composition containing unreacted isocyanate groups is first sprayed onto the surface of the power distribution equipment cabinet housing to form a continuous and uniform wet film. Before the wet film cures, powdered superhydrophobic micro / nano structural units are applied by electrostatic spraying. Electrostatic action causes negatively charged powder particles to be uniformly adsorbed onto the positively charged wet film surface, achieving a single-layer or quasi-single-layer arrangement. At this point, the lower half of the powder particles is embedded in the wet film, while the upper half is exposed. The resin in the wet film initially contacts and wets the active groups (such as amino and hydroxyl groups) on the surface of the microspheres, laying the foundation for subsequent chemical bonding. Subsequently, the composite wet film is irradiated with ultraviolet light, causing the wet primer film to transform from a liquid state into a solid elastomer, while simultaneously mechanically locking the embedded surface layer micro / nano structural units. After initial curing, the unreacted isocyanate groups reserved in the coating begin to play their role, undergoing a slow chemical reaction with trace amounts of moisture in the environment (or within the coating): water first reacts with the unreacted isocyanate groups to generate unstable carbamic acid, which then decomposes into amine and releases carbon dioxide. The newly generated amine then rapidly reacts with another unreacted isocyanate group to form a stable urea bond, increasing the crosslinking density and thus improving the mechanical strength, abrasion resistance, chemical resistance, and barrier properties of the coating.

[0049] The ultraviolet light irradiation uses a UV-A band light source with a power of not less than 2000W, and the curing time is 5-30 minutes; the voltage for electrostatic spraying is 40-80 kV.

[0050] In this embodiment, a UV-A band (320-400nm) light source with a power of not less than 2000W is used. The UV-A band light source is a lamp or device specifically designed to emit UV-A ultraviolet light. The wavelength range of UV-A ultraviolet light is 315 nm to 400 nm to provide sufficient light intensity and penetration depth to the coating, avoiding incomplete curing. The electrostatic spraying voltage is 40-80kV. Under this electric field, corona discharge occurs at the tip of the spray gun electrode, ionizing the air and generating a large number of ions that adhere to the surface of the powder particles, charging them. 40kV is the lower threshold threshold that allows the microspheres to be fully charged and generate sufficient electric field force to overcome gravity and inertia, achieving directional flight and adsorption onto the surface of the wetted base coating with the opposite charge. 80kV is the upper limit considering equipment safety, avoiding air breakdown, and preventing excessive repulsion between powder particles due to excessive charge, which could affect the tight arrangement of the single layer. This voltage range ensures high powder deposition efficiency, uniform distribution, and the formation of an ideal single-layer or quasi-single-layer structure.

[0051] The primer composition is applied by spraying with a self-spraying pressure can or a pneumatic pressure tank, and self-leveling is allowed for 10-15 minutes after spraying. After electrostatic spraying, any superhydrophobic micro / nano structural units that are not firmly attached are removed.

[0052] In this embodiment, a self-spraying pressure can or a pneumatic pressure tank is used to apply the primer coating to provide a stable, controllable, and well-atomized spraying effect. After spraying, self-leveling is allowed for 10-15 minutes. During this period, the wet primer coating automatically smooths out surface undulations such as orange peel and ripples caused by spraying under surface tension. Simultaneously, air bubbles trapped within the coating escape, resulting in a uniform, smooth, and defect-free primer coating. Excess superhydrophobic micro / nano structure unit powder remains after electrostatic spraying. If not removed, this powder cannot form effective bonds with the primer coating during subsequent UV curing, easily detaching during coating service life and affecting its lifespan.

[0053] Preparation Example 1: At room temperature, 200g of anhydrous ethanol was mixed with 50g of tetraethyl silicate, 20g of 25% ammonia water, and 5g of silane coupling agent A151 (vinyltrimethoxysilane). The mixture was stirred until homogeneous, then heated in a water bath at 60°C with a stirring speed of 300 rpm for 4 hours. After the reaction was complete, the ethanol and ammonia water were rotary evaporated at room temperature until the solution was neutral. Then, 5g of 30% neutral silica sol was added to obtain an organosilicon-inorganic silica sol for later use.

[0054] Hollow glass microspheres with an average particle size of 150 μm were then ultrasonically cleaned in anhydrous ethanol and deionized water to remove surface impurities. They were then immersed in a piranha etching solution prepared with 98% concentrated sulfuric acid and 30% hydrogen peroxide at a volume ratio of 3:1 for 6 hours for hydroxylation treatment. After rinsing in deionized water, they were dried. Next, the hydroxylated hollow glass microspheres were immersed in an alcoholic aqueous solution of KH560 (γ-glycidyl etheroxypropyltrimethoxysilane) for 2 hours, then dried to enhance surface adhesion. Finally, they were dispersed in the self-made organosilicon-inorganic silica sol for 30 minutes, followed by rotary evaporation drying at a temperature gradually increased from 50°C to 150°C. After cooling, they were wet-activated with an ethanol solution of heptadecafluorodecyltriethoxysilane and dried to obtain superhydrophobic micro / nano structure units for later use. Electron microscopy images of the superhydrophobic micro / nano structure units are shown below. Figure 1 and Figure 2 As shown.

[0055] Meanwhile, 50g of polyurethane acrylate prepolymer (with a number average molecular weight of 6000 and a residual isocyanate group content of 1%), 10g of Ebecryl 8413 (a polyurethane acrylate oligomer), 25g of norborneol methacrylate, 15g of isooctyl acrylate, 1.5g of photoinitiator TPO, 5g of ultrafine hollow glass microspheres, 1g of rutile titanium dioxide, 1g of hindered amine light stabilizer Eversorb 60 (an alkoxy-based hindered amine light stabilizer), 0.5g of nano zinc oxide, and 0.2g of leveling agent TEGO100 (a surface control additive based on polyether-modified polysiloxane) were stirred and dispersed, and then thickened to the required viscosity and rheological properties with organomontmorillonite as a thickener. Subsequently, the mixture was cooled and ground to obtain the base coating composition.

[0056] The primer coating composition was sprayed onto a tinplate test plate using a self-spraying press, with the wet film thickness controlled at 80-120 μm. After spraying, the mixture was allowed to self-level for 10-15 minutes to form a primer wet film. Subsequently, superhydrophobic micro / nano structure units were sprayed onto the uncured primer wet film surface using electrostatic powder coating, aiming for a uniform single-layer spread of the superhydrophobic micro / nano structure units. After the primer coating was completely covered, it was cured by ultraviolet light irradiation using a high-power LED UV-A (320-400nm) spherical lamp for 15 minutes.

[0057] The static water contact angle of the superhydrophobic insulating coating was tested after complete curing, and the results are as follows: Figure 4 As shown.

[0058] In addition, the fracture strength and elongation at break of the primer composition were tested after curing it separately as a primer. Figure 3 As shown, the horizontal axis represents the fracture elongation and the vertical axis represents the fracture strength.

[0059] Preparation Example 2: At room temperature, 150g of anhydrous ethanol was mixed with 50g of tetraethyl silicate, 10g of 25% ammonia water, and 5g of silane coupling agent KH560 (γ-glycidoxypropyltrimethoxysilane). The mixture was stirred until homogeneous, then heated in a water bath at 60℃ with a stirring speed of 300 rpm for 4 hours. After the reaction was complete, the ethanol and ammonia water were rotary evaporated at room temperature until the solution was neutral. Then, 5g of 30% neutral silica sol was added to obtain an organosilicon-inorganic silica nanosol for later use.

[0060] Hollow glass microspheres with average particle sizes of 50 μm and 100 μm were then mixed at a mass ratio of 7:3 and ultrasonically cleaned in anhydrous ethanol and deionized water to remove surface impurities. They were then immersed in a piranha etching solution prepared with 98% concentrated sulfuric acid and 30% hydrogen peroxide at a volume ratio of 3:1 for 12 hours for hydroxylation treatment. After rinsing in deionized water, they were dried. The hydroxylated hollow glass microspheres were then immersed in an alcoholic aqueous solution of KH570 (γ-methacryloyloxypropyltrimethoxysilane) for 4 hours, dried, and then used to enhance surface adhesion. Finally, they were dispersed in the self-made organosilicon-inorganic silicon nanosol for 30 minutes, followed by rotary evaporation drying at a temperature gradually increased from 50°C to 150°C. After cooling, they were wet-activated with an ethanol solution of heptadecafluorodecyltrimethoxysilane and dried to obtain superhydrophobic micro / nano structural units for later use.

[0061] Meanwhile, 60g of polyurethane acrylate prepolymer (with a number average molecular weight of 6000 and a residual isocyanate group content of 1%), 20g of norborneol methacrylate, 20g of isooctyl acrylate, 1.5g of photoinitiator TPO, 10g of ultrafine hollow glass microspheres, 1g of rutile titanium dioxide, 1g of hindered amine light stabilizer Eversorb 90, 0.5g of nano zinc oxide, and 0.3g of leveling agent TEGO100 were stirred and dispersed, and then thickened to the required viscosity and rheological properties with organomontmorillonite as a thickener. After cooling and grinding, the base coating composition was obtained.

[0062] The primer coating composition was sprayed onto a tinplate test plate using a self-spraying press, with the wet film thickness controlled at 40-60 μm. After spraying, the mixture was allowed to self-level for 10-15 minutes to form a primer wet film. Subsequently, superhydrophobic micro / nano structure units were sprayed onto the uncured primer wet film surface using electrostatic powder coating, aiming for a uniform single-layer spread of the superhydrophobic micro / nano structure units. After the primer coating was completely covered, it was cured by UV-A (320-400 nm) ultraviolet spherical lamp irradiation for 15 minutes.

[0063] Preparation Example 3: At room temperature, 150g of anhydrous ethanol was mixed with 45g of tetraethyl silicate, 20g of 25% ammonia water, 1g of silane coupling agent KH560 (γ-glycidoxypropyltrimethoxysilane), and 6g of A151 (vinyltriethoxysilane). The mixture was stirred until homogeneous, then heated in a water bath at 70°C with a stirring speed of 300 rpm for 4 hours. After the reaction was complete, the ethanol and ammonia water were rotary evaporated at room temperature until the solution was neutral. Then, 10g of 30% neutral silica sol was added to obtain an organosilicon-inorganic silica nanosol for later use.

[0064] Hollow glass microspheres with average particle sizes of 50 μm, 150 μm, and 300 μm were then mixed in a mass ratio of 6:3:1 and ultrasonically cleaned in anhydrous ethanol and deionized water to remove surface impurities. They were then immersed in a piranha etching solution prepared with 98% concentrated sulfuric acid and 30% hydrogen peroxide in a volume ratio of 3:1 for 12 hours for hydroxylation treatment. After rinsing in deionized water, they were dried. The hydroxylated hollow glass microspheres were then immersed in an alcoholic aqueous solution of KH590 (γ-mercaptopropyltrimethoxysilane) for 4 hours, dried, and then further dried to enhance surface adhesion. Finally, they were dispersed in the self-made organosilicon-inorganic silicon nanosol for 30 minutes, followed by rotary evaporation drying at a temperature gradually increased from 50°C to 150°C. After cooling, they were wet-activated with an ethanol solution of tridecafluorooctyltrimethoxysilane and dried to obtain superhydrophobic micro / nano structural units for later use.

[0065] Meanwhile, 60g of polyurethane acrylate prepolymer (with a number average molecular weight of 4000 and a residual isocyanate group content of 0.5%), 10g of Ebecryl 8413, 15g of norborneol methacrylate, 15g of isooctyl acrylate, 1.5g of photoinitiator TPO, 6g of ultrafine hollow glass microspheres, 1g of rutile titanium dioxide, 1g of hindered amine light stabilizer Eversorb 91, 0.5g of nano zinc oxide, and 0.3g of leveling agent TEGO100 were stirred and dispersed, and then thickened to the required viscosity and rheological properties using an organic-inorganic composite gel as a thickener. After cooling and grinding, the base coating composition was obtained.

[0066] The primer coating composition was sprayed onto the tinplate test plate using a self-spraying press, with the wet film thickness controlled at 60-80 μm. After spraying, the mixture self-leveled for 5-10 minutes to form the primer wet film. Subsequently, superhydrophobic micro-nano structure units were sprayed onto the uncured primer wet film surface using electrostatic powder spraying, with the goal of uniformly spreading the superhydrophobic micro-nano structure units in a single layer. After the primer was completely covered, it was cured by ultraviolet light irradiation with a high-power UV-A (320-400nm) spherical lamp for 20 minutes.

[0067] Preparation Example 4: At room temperature, 200g of anhydrous ethanol was mixed with 50g of tetraethyl silicate, 20g of 25% ammonia water, 5g of silane coupling agent KH560 (γ-glycidoxypropyltrimethoxysilane), and 2g of methacryloxysilane. The mixture was stirred until homogeneous, then heated in a water bath at 55°C with a stirring speed of 300 rpm for 6 hours. After the reaction was complete, the ethanol and ammonia water were rotary evaporated at room temperature until the solution was neutral. Then, 10g of 30% neutral silica sol was added to obtain an organosilicon-inorganic silica nanosol for later use.

[0068] Hollow glass microspheres with an average particle size of 100 μm were then ultrasonically cleaned in anhydrous ethanol and deionized water to remove surface impurities. They were then immersed in a piranha etching solution prepared with 98% concentrated sulfuric acid and 30% hydrogen peroxide at a volume ratio of 3:1 for 12 hours for hydroxylation treatment. After rinsing in deionized water, they were dried. Next, the hydroxylated hollow glass microspheres were immersed in a mixed alcohol-water solution of KH560 and A171 (vinyltrimethoxysilane) for 4 hours, then dried to enhance surface adhesion. Finally, they were dispersed in the self-made organosilicon-inorganic silicon nanosol for 30 minutes, followed by rotary evaporation drying at a temperature gradually increased from 50°C to 150°C. After cooling, they were wet-activated with an ethanol solution of trifluoropropyltrichlorosilane and dried to obtain superhydrophobic micro / nano structural units for later use.

[0069] Meanwhile, 60g of polyurethane acrylate prepolymer (with a number average molecular weight of 3000 and a residual isocyanate group content of 0.8%), 25g of norborneol methacrylate, 15g of isooctyl acrylate, 1.5g of photoinitiator TPO, 5g of ultrafine hollow glass microspheres, 1g of rutile titanium dioxide, 1g of hindered amine light stabilizer HS-625, 1.0g of nano zinc oxide, and 1.1g of leveling agent TEGO1000 were stirred and dispersed. Then, organic modified clay sheets were used as a thickener to thicken the mixture to the required viscosity and rheological properties. The mixture was then cooled and ground to obtain the base coating composition.

[0070] The primer composition was sprayed onto a tinplate test plate using a self-spraying press, with the wet film thickness controlled at 60-80 μm. After spraying, the film was allowed to self-level for 10-15 minutes to form a primer wet film. Subsequently, superhydrophobic micro / nano structure units were sprayed onto the uncured primer wet film surface using electrostatic powder coating, aiming for a uniform single-layer spread of the superhydrophobic micro / nano structure units. After the primer was completely covered, it was cured by UV-A (320-400 nm) ultraviolet spherical lamp irradiation for 15 minutes.

[0071] Preparation Example 5: At room temperature, 200g of anhydrous ethanol was mixed with 50g of tetraethyl silicate, 10g of 25% ammonia water, and 5g of silane coupling agent KH560 (γ-glycidoxypropyltrimethoxysilane). The mixture was stirred until homogeneous, then heated in a water bath at 60℃ with a stirring speed of 300 rpm for 4 hours. After the reaction was complete, the ethanol and ammonia water were rotary evaporated at room temperature until the solution was neutral. Then, 5g of 30% neutral silica sol was added to obtain an organosilicon-inorganic silica nanosol for later use.

[0072] Hollow glass microspheres with an average particle size of 100 μm were then ultrasonically cleaned in anhydrous ethanol and deionized water to remove surface impurities. They were then immersed in a piranha etching solution prepared with 98% concentrated sulfuric acid and 30% hydrogen peroxide at a volume ratio of 3:1 for 24 hours for hydroxylation treatment. After rinsing in deionized water, they were dried. Next, the hydroxylated hollow glass microspheres were immersed in a mixed alcohol-water solution of KH570 (γ-methacryloyloxypropyltrimethoxysilane) and A151 (vinyltriethoxysilane) for 4 hours, then dried to enhance surface adhesion. Finally, they were dispersed in the aforementioned self-made organosilicon-inorganic silica sol solution for 30 minutes and then rotary dried by gradually increasing the rotary evaporation temperature from 50℃ to 150℃. After cooling, they were wet-activated with an ethanol solution of heptadecafluorodecyltrimethoxysilane and dried to obtain superhydrophobic micro / nano structural units for later use.

[0073] Meanwhile, 60g of polyurethane acrylate prepolymer (with a number average molecular weight of 5000 and a residual isocyanate group content of 1%), 10g of norborneol methacrylate, 8g of Ebecryl 8413, 15g of isooctyl acrylate, 1.5g of photoinitiator TPO, 10g of ultrafine hollow glass microspheres, 1g of rutile titanium dioxide, 1g of hindered amine light stabilizer Eversorb 90, 0.5g of nano zinc oxide, and 0.3g of leveling agent TEGO100 were stirred and dispersed, and then thickened to the required viscosity and rheological properties with organomontmorillonite as a thickener. After cooling and grinding, the base coating composition was obtained.

[0074] The primer coating composition was sprayed onto a tinplate test plate using a self-spraying press, with the wet film thickness controlled at 60-80 μm. After spraying, the film was allowed to self-level for 10-15 minutes to form the first primer coating wet film. Subsequently, superhydrophobic micro-nano structure units were sprayed onto the uncured first primer coating wet film surface using electrostatic powder spraying, aiming for a uniform single-layer spread of the superhydrophobic micro-nano structure units. After the first primer coating was completely covered, it was cured by UV-A (320-400 nm) UV spherical lamp with a high-power UV mercury lamp for 15 minutes. The above process of spraying the primer coating composition, self-leveling, electrostatic powder spraying of superhydrophobic micro-nano structure units, and UV curing was repeated to obtain a multilayer composite superhydrophobic thermal insulation coating.

[0075] Comparative example: The difference between this comparative example and Example 1 is that no nano-protrusion structure is prepared on the surface of the hollow glass microspheres. The specific preparation process is as follows: Hollow glass microspheres of the specifications used in Example 1 were ultrasonically cleaned in anhydrous ethanol and deionized water to remove surface impurities, and then dried. The cleaned and dried hollow glass microspheres were then directly immersed in an ethanol aqueous solution of KH560 for 2 hours, and then dried. They were then immersed in an ethanol aqueous solution of trifluoropropyltrichlorosilane for 2 hours, and then dried to obtain surface-modified microspheres for comparison.

[0076] The formulation, preparation method, and application process of the primer coating composition are exactly the same as those in Example 1.

[0077] The same coating process as in Example 1 was used. The primer composition was sprayed onto the tinplate test plate, and the thickness of the wet primer was controlled at 80-120 μm. Self-leveling was performed for 10-15 min. Then, the surface-modified microspheres used for comparison were sprayed onto the uncured wet primer surface by electrostatic powder spraying, and the microspheres were controlled to be uniformly arranged in a single layer on the wet primer surface. After the primer was completely covered, ultraviolet light curing was performed using the same high-power LED light source UV-A (320-400 nm) ultraviolet spherical lamp for 15 min to obtain a superhydrophobic insulating coating.

[0078] Test example: 1. The superhydrophobic insulating coatings prepared in Examples 1-5 were tested for tensile properties using a Zwick / Roell Z020 (Zwick GmbH, Germany) universal testing machine, according to GB / T1040-2006; test conditions: tensile speed 10 mm / min. The test results are shown in Table 1. Table 1: Tensile breaking strength test results of the superhydrophobic insulating coatings prepared in Examples 1-5 2. The static contact angles of the superhydrophobic insulating coatings prepared in Examples 1-5 and the comparative examples were tested using an SDC-100 semi-automatic contact angle measuring instrument. The results are shown in Table 2.

[0079] Table 2: Surface water droplet test results of the superhydrophobic insulating coatings prepared in Examples 1-5 and Comparative Example 1 3. The flame retardant properties of the superhydrophobic insulating coatings prepared in Examples 1 to 5 were tested using the GB12441-2018 standard, and the results are shown in Table 3.

[0080] Table 3: Adhesion and flame retardant properties of the superhydrophobic insulating coatings prepared in Examples 1-5 4. The thermal conductivity of the superhydrophobic insulating coatings prepared in Examples 1-5 was tested using a thermal conductivity meter in standard mode. The results are shown in Table 4.

[0081] Table 4: Test results of thermal conductivity of the superhydrophobic insulating coatings prepared in Examples 1-5 5. The superhydrophobic insulating coatings prepared in Examples 1-5 were tested according to the test methods in standard GB / T 31838.2—2019 "Dielectric and resistive properties of solid insulating materials - Part 2: Resistive properties (DC method) - Volume resistivity and volume resistivity". The test conditions were constant temperature 25 ℃. The test results are shown in Table 5.

[0082] Table 5: Volume resistivity of the superhydrophobic insulating coatings prepared in Examples 1-5 The corrosion resistance of the superhydrophobic insulating coatings prepared in Examples 1-5 was tested using a neutral salt spray test, in accordance with GB / T10125-2021. For all salt spray tests, three parallel samples were placed in a salt spray chamber for testing. The coatings were photographed and recorded at regular intervals. The coating was considered to have achieved the desired effect if all three samples met the requirements. The results are shown in Table 6.

[0083] Table 6: The corrosion resistance of the superhydrophobic insulating coatings prepared in Examples 1-5 was tested using neutral salt spray. The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that the present invention includes, but is not limited to, the contents described in the accompanying drawings and the specific embodiments above. Any modifications that do not depart from the functional and structural principles of the present invention will be included within the scope of the claims.

Claims

1. A superhydrophobic insulating coating for the housing of a power distribution equipment cabinet, characterized in that, Includes a base coat and a top coat; The base layer is a polyurethane acrylate elastomer layer that can be cured by ultraviolet light and contains unreacted isocyanate groups; The topcoat is formed by fixing multiple superhydrophobic micro / nano structure units to the surface of the bottom coating, and the superhydrophobic micro / nano structure units are arranged in a single layer on the surface of the bottom coating. The superhydrophobic micro / nano structure unit is a hollow glass microsphere with a nano-protrusion structure on its surface.

2. The superhydrophobic insulating coating according to claim 1, characterized in that, The method for forming the superhydrophobic micro / nano structure unit includes the following steps: Surface hydroxylation treatment of hollow glass microspheres; Hollow glass microspheres after hydroxylation were pretreated with silane coupling agents. Pretreated hollow glass microspheres were immersed in organosilicon-inorganic silica sol and dried by rotary evaporation to form nano-protrusion structures on the hollow glass microspheres. Surface hydrophobic modification of hollow glass microspheres with nanoprotrusions was performed using organofluorosilane coupling agents.

3. The superhydrophobic insulating coating according to claim 2, characterized in that, The organosilicon-inorganic silica sol raw material composition comprises the following components in parts by weight: The mixture comprises 100-200 parts anhydrous ethanol, 30-50 parts tetraethyl silicate, 5-20 parts 25% ammonia water, 0-5 parts silane coupling agent, and 0-20 parts 30% neutral silica sol; wherein the silane coupling agent is selected from one or more of γ-aminopropyltriethoxysilane, vinyltriethoxysilane, vinyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-methacryloyloxypropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, methacryloyloxysilane, and chloropropylsilane.

4. The superhydrophobic insulating coating according to claim 2, characterized in that, The preparation process of the organosilicon-inorganic silica sol includes: mixing anhydrous ethanol, tetraethyl silicate, ammonia water and silane coupling agent, heating in a water bath at 50-80℃, and reacting at a stirring speed of 350 rpm for 2-6 hours to obtain a solution; after the reaction is completed, the solution is rotary evaporated at room temperature until the solution is neutral to obtain nano-silica sol; finally, the neutral silica sol is heated and added to the nano-silica sol and stirred evenly.

5. The superhydrophobic insulating coating according to claim 1, characterized in that, The thickness of the base coating is 50% to 120% of the diameter of the superhydrophobic micro / nano structure unit. The raw material composition of the base coating, by weight, includes the following components: 40-70 parts of polyurethane acrylate prepolymer, 0-20 parts of polyurethane acrylate oligomer, 10-30 parts of norborneol methacrylate, 5-30 parts of isooctyl acrylate, 1-2 parts of photoinitiator, 0-20 parts of ultrafine hollow glass microspheres, 0-3 parts of rutile titanium dioxide, 1-3 parts of alkoxy-containing hindered amine light stabilizer, 0-2 parts of nano zinc oxide, 0.1-0.5 parts of leveling agent, and 0.2-5 parts of tackifier. The polyurethane acrylate prepolymer is formed by the reaction polymerization of polyester polyol with aliphatic isocyanate prepolymer and hydroxyethyl acrylate. The polyurethane acrylate prepolymer has a molecular weight of 1000-7000 and contains 0.5% to 2% by mass of unreacted isocyanate groups.

6. The superhydrophobic insulating coating according to claim 5, characterized in that, The raw material composition of the base coating comprises, by weight, the following components: 50-55 parts of polyurethane acrylate prepolymer, 5-10 parts of polyurethane acrylate oligomer, 20-30 parts of norborneol methacrylate, 10-15 parts of isooctyl acrylate, 1-1.5 parts of photoinitiator TPO, 0-5 parts of ultrafine hollow glass microspheres, 0-2 parts of rutile titanium dioxide, 1-2 parts of alkoxy-containing hindered amine light stabilizer, 0-1 part of nano zinc oxide, 0.1-0.5 parts of leveling agent, and 0.2-3 parts of tackifier; the polyurethane acrylate prepolymer has a molecular weight of 3000-5000 and contains 0.5%~1% by mass of unreacted isocyanate groups.

7. The superhydrophobic insulating coating according to claim 5, characterized in that, The tackifier is one or more of organic montmorillonite, inorganic gel, and inorganic clay flakes; the hindered amine light stabilizer with alkoxy group includes one or more of Eversorb 60, Eversorb 90, Eversorb 91, HS-625, and Tinuvin PUR866.

8. A method for preparing a superhydrophobic insulating coating, characterized in that, The superhydrophobic insulating coating comprises the superhydrophobic insulating coating for power distribution equipment cabinet housing as described in any one of claims 1 to 7, and the preparation method comprises the following steps: A polyurethane acrylate primer composition containing unreacted isocyanate groups is sprayed onto the surface of the power distribution equipment cabinet housing to form a wet primer film; Before the wet primer film is cured, multiple powdered superhydrophobic micro-nano structure units are applied to the surface of the primer film by electrostatic spraying and formed into a single layer arrangement. The coating after electrostatic spraying is irradiated with ultraviolet light to cause the primer composition to undergo initial curing and fix the superhydrophobic micro-nano structure unit to form the top coating. Unreacted isocyanate groups in the initially cured coating react with moisture in the environment, undergoing a second curing process.

9. The preparation method according to claim 8, characterized in that, The ultraviolet irradiation uses a UV-A band light source with a power of not less than 2000W, and the curing time is 5-30 minutes; the voltage of the electrostatic spraying is 40-80 kV.

10. The preparation method according to claim 8, characterized in that, The primer composition is applied by spraying with a self-spraying pressure can or a pneumatic pressure barrel, and self-leveling is performed for 10-15 minutes after spraying. After electrostatic spraying, any superhydrophobic micro / nano structural units that are not firmly attached are removed.

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