High-thermal-conductivity super-hydrophobic insulating coating and preparation method thereof

Abstract

The invention discloses a high-thermal-conductivity super-hydrophobic insulating coating and a preparation method, and relates to the field of coatings, the high-thermal-conductivity super-hydrophobic insulating coating is used for protecting a power distribution equipment cabinet shell, and the high-thermal-conductivity super-hydrophobic insulating coating comprises a urethane acrylate bottom coating and a functional surface layer; the polyurethane acrylate bottom coating layer comprises an unreacted isocyanate group; the functional surface layer is formed by arranging a plurality of heat-conducting microspheres with nano bulge structures on the surface on the surface of the urethane acrylate priming coat; and forming a nano bulge structure on the surface of the heat-conducting microsphere by a sol-gel method. The prepared high-thermal-conductivity super-hydrophobic insulating coating has the advantages of being good in thermal conductivity and good in hydrophobic effect.

Description

Technical Field

[0001] This invention relates to the field of coatings, specifically to a high thermal conductivity superhydrophobic insulating coating and its preparation method. Background Technology

[0002] With the rapid development of urbanization and power grids in my country, the application of box-type power equipment such as ring main units in power distribution systems is becoming increasingly widespread. These equipment cabinets operate in complex outdoor environments for extended periods, and condensation frequently occurs inside due to temperature differences between the inside and outside. Condensation droplets adhering to the insulation components and metal surfaces inside the cabinet significantly reduce the equipment's insulation performance, leading to serious faults such as partial discharge, short circuits, and even breakdowns, threatening the safe and stable operation of the power grid. Simultaneously, electrical components inside the cabinet (such as busbars and terminals) generate heat during operation. If this heat cannot be effectively dissipated, it will cause localized temperature increases, accelerating the aging of insulation materials and reducing the equipment's lifespan.

[0003] To address these issues, the industry typically attempts to apply functional protective coatings to the inner walls of power distribution equipment cabinets and the surfaces of electrical components. Among these, coatings combining superhydrophobic and insulating properties have received widespread attention. Superhydrophobic coatings effectively repel liquid water, preventing condensation and fundamentally eliminating water-related hazards. However, the operating environment inside power distribution equipment places more stringent comprehensive performance requirements on the coatings: First, the coating must possess excellent electrical insulation to ensure equipment safety; second, to accommodate the significant thermal expansion and contraction of metal components due to current heating effects and ambient temperature changes, the coating needs high elasticity and flexibility to prevent cracking and peeling; third, the coating should assist in conducting or dissipating heat from electrical components to prevent heat accumulation; furthermore, within the confined and enclosed space of the cabinet, the coating must also meet requirements for flame retardancy, corrosion resistance, and strong adhesion.

[0004] Currently, various technical solutions are being developed to prepare superhydrophobic insulating coatings. For example, surface roughness can be achieved by using template methods, chemical etching, or directly adding hydrophobic nanoparticles (such as hydrophobic silica) to the resin. However, these methods generally have shortcomings: template and etching methods are complex and difficult to implement in complex cabinet structures; the resulting brittle ceramic or inorganic structures cannot adapt to the thermal deformation of the metal substrate, leading to cracking and failure. Coatings made by simply blending nanoparticles have poor hydrophobic durability, the particles are prone to detachment, and they lack active heat dissipation capabilities. Another technical solution (such as patent CN202411353116.3) attempts to use modified graphene and other fillers to simultaneously achieve thermal conductivity and superhydrophobicity; however, graphene-based materials pose a risk of electrical conductivity, limiting their application in high-voltage insulation applications, and the interfacial bonding strength between graphene and the resin matrix, as well as their stability under long-term thermal cycling, still need to be verified.

[0005] Therefore, there is a need to develop a new, multifunctional coating that can meet the requirements of power distribution cabinets. 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 high thermal conductivity superhydrophobic insulating coating and its preparation method. The resulting high thermal conductivity superhydrophobic insulating coating has the advantages of good thermal conductivity and good hydrophobic effect.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A high thermal conductivity superhydrophobic insulating coating for protecting the housing of power distribution equipment cabinet, comprising a polyurethane acrylate base layer and a functional top layer; The polyurethane acrylate undercoat includes unreacted isocyanate groups; The functional surface layer is formed by arranging multiple thermally conductive microspheres with nano-protrusion structures on the surface of the polyurethane acrylate base coating; Nanoprotrusion structures were formed on the surface of thermally conductive microspheres using the sol-gel method.

[0008] In this application, the high thermal conductivity and superhydrophobic insulating coating is a two-layer composite structure. The polyurethane acrylate base layer provides strong adhesion, high elasticity, and basic insulation to the power distribution equipment cabinet housing (such as tinplate, aluminum alloy, or engineering plastics). The functional top layer provides superhydrophobicity and high thermal conductivity. Nanoscale protrusion structures are formed on the surface of the thermally conductive microspheres using a sol-gel method. Multiple nanoscale protrusion structures form a lotus leaf-like biomimetic structure, further improving the surface roughness of the functional top layer. This allows water droplets to be held atop the nanoscale protrusions, resulting in a large contact angle (typically greater than 150°) and a very small roll-off angle (less than 10°), making it easy for the water droplets to roll off. This fundamentally prevents condensation, cuts off the electrolyte channels required for electrochemical corrosion, provides excellent hydrophobicity, and achieves long-term corrosion protection. Simultaneously, the functional top layer, formed by the arrangement of multiple thermally conductive microspheres, significantly improves the coating's thermal conductivity, which is beneficial for heat dissipation of electronic components within the power distribution equipment cabinet housing.

[0009] Optionally, the thermally conductive microspheres are spherical particles with a particle size of 20-1000 μm, a thermal conductivity greater than 30 W / (m·K), and a sphericity greater than 90%. The thermally conductive microspheres are selected from one or more of spherical alumina, spherical magnesium oxide, spherical boron nitride, and hexagonal boron nitride.

[0010] Thermally conductive microspheres are the basic building blocks for constructing functional surface layers. Microspheres with a particle size range of 20-1000 μm are easily electrostatically sprayed onto a polyurethane acrylate primer to form a monolayer. Furthermore, the selected thermally conductive microspheres should have a thermal conductivity greater than 30 W / (m·K) to ensure the overall heat dissipation capacity of the high thermal conductivity superhydrophobic insulating coating. Additionally, the selected microspheres should have a sphericity greater than 90% to ensure smooth rolling and regular arrangement. The high thermal conductivity of the microsphere material itself guarantees the overall thermal conductivity of the coating, and its regular spherical geometry ensures a uniform and regular monolayer arrangement on the primer surface, thereby creating a stable micron-level roughness on the surface of the high thermal conductivity superhydrophobic insulating coating.

[0011] Optionally, the thermally conductive microspheres are spherical boron nitride with a particle size of 50-500 μm.

[0012] Spherical boron nitride not only possesses high thermal conductivity but also excellent insulation and low dielectric loss, making it an ideal filler for coatings used in power equipment, simultaneously meeting the requirements for insulation and heat dissipation. Preferably, spherical boron nitride with a particle size of 50-500 μm is selected. This particle size range ensures that the microspheres are large enough to create micron-level roughness for superhydrophobicity, while avoiding excessively large particle sizes that would affect the thin-layer spraying and flexibility of the high thermal conductivity superhydrophobic insulating coating. Furthermore, thermally conductive microspheres within this particle size range are readily available on the market and have good flowability, making them ideal for subsequent electrostatic spraying onto the surface of a polyurethane acrylate primer.

[0013] Optionally, the formation of nanoprotrusion structures on the surface of thermally conductive microspheres via the sol-gel method includes the following steps: Hydroxylation treatment was performed on the thermally conductive microspheres; The hydroxylated thermally conductive microspheres were pretreated with a silane coupling agent. The pretreated thermally conductive microspheres were immersed in an organosilicon-inorganic silica sol and dried to form nano-protrusion structures on the surface of the thermally conductive microspheres. Surface treatment of thermally conductive microspheres with nanoprotrusions using organofluorosilane coupling agents can reduce surface energy.

[0014] In preparing nanoprotrusion structures on the surface of thermally conductive microspheres, the microspheres are first hydroxylated using a "piranha solution" (a mixture of concentrated sulfuric acid and hydrogen peroxide), introducing a large number of active -Si-OH groups onto their surface. Next, the microspheres are pretreated with silane coupling agents such as γ-aminopropyltriethoxysilane to enhance the bonding force between the microsphere surface and the subsequent organosilicon-inorganic silica sol. Then, the microspheres are immersed in the pre-prepared organosilicon-inorganic silica sol, allowing the sol on the microsphere surface to solidify, thus forming the nanoprotrusion structure. Specifically, the solidification method is rotary evaporation or spray drying. Rotary evaporation involves placing the sol-soaked microspheres into a rotary evaporator for vacuum distillation, where the solvent (such as ethanol or water) is rapidly evaporated and removed. The sol concentrates on the microsphere surface and undergoes a gelation reaction, ultimately forming a dried nanoprotrusion structure. Finally, the siloxane end of the organofluorosilane coupling agent reacts with the silanol groups on the surface of the nanoprotrusion structure to form a chemical bond, thereby grafting its extremely low surface energy fluorocarbon long chains onto the microsphere surface in the form of covalent bonds, thus reducing the surface energy of the thermally conductive microspheres. The nanoprotrusion structure formed by this method has good chemical stability and is not easily detached.

[0015] Optionally, the organofluorosilane coupling agent is selected from one or more of heptadecafluorodecyltriethoxysilane, heptadecafluorodecyltrimethoxysilane, tridecafluorooctyltrimethoxysilane, and trifluoropropyltrichlorosilane.

[0016] The long fluorocarbon chains in organofluorosilane coupling agents are key to achieving ultra-low surface energy. Heptadecyltriethoxysilane, heptadecyltrimethoxysilane, tridecafluorooctyltrimethoxysilane, and trifluoropropyltrichlorosilane all contain long fluorocarbon chains. Heptadecyltriethoxysilane and tridecafluorooctyltrimethoxysilane are preferred organofluorosilane coupling agents to provide excellent hydrophobic and oleophobic properties to the thermally conductive microspheres. In practical implementation, different organofluorosilane coupling agents can be selected to achieve the goal of low surface energy modification.

[0017] Optionally, the raw materials for preparing organosilicon-inorganic silica sol include, by weight, 100-200 parts of anhydrous ethanol, 30-50 parts of tetraethyl orthosilicate, 5-20 parts of ammonia, and 1-5 parts of silane coupling agent, 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.

[0018] Anhydrous ethanol was used as the solvent, tetraethyl orthosilicate as the silicon source, and ammonia as the catalyst. The addition of silane coupling agents modulates the flexibility and reactivity of the gel network in the organosilicon-inorganic silica sol, forming a nanoprotrusion structure that coats thermally conductive microspheres. Among the silane coupling agents used, γ-aminopropyltriethoxysilane introduces amino groups, γ-glycidoxypropyltrimethoxysilane introduces epoxy groups, and γ-methacryloyloxypropyltrimethoxysilane introduces methacryloyloxy groups. The introduction of these active functional groups gives the formed nanoprotrusion structure a certain organic component, making it more flexible and reducing cracking, thereby further enhancing the interfacial bonding strength between the functional top layer and the polyurethane acrylate base layer.

[0019] Optionally, the organosilicon-inorganic silica sol is prepared by the following steps: anhydrous ethanol, tetraethyl orthosilicate, ammonia and silane coupling agent are mixed to obtain a solution, the solution is heated in a water bath at 55-60℃ and stirred at 350 rpm for 2-6 hours, after the reaction is completed, the solution is rotary evaporated until it is neutral to obtain nano-silica sol, and finally 0-20 parts of neutral silica sol are added to the nano-silica sol to obtain organosilicon-inorganic silica sol.

[0020] These process conditions ensure the stability of the organosilicon-inorganic silica sol and the controllability of the nanoprotrusion structure size. A water bath temperature of 55-60℃ and a reaction time of 2-6 hours guarantee the preparation of a stable organosilicon-inorganic silica sol. Rotary evaporation to neutrality after the reaction removes excess ammonia, preventing prolonged alkaline conditions that could destabilize the sol or adversely affect subsequent processing. Adding neutral silica sol allows for adjustment of the sol's solids content and viscosity.

[0021] Optionally, the thickness of the polyurethane acrylate primer coating is 50%-90% of the diameter of the thermally conductive microspheres.

[0022] This thickness range ensures that the base coating thickness is sufficient to fix the thermally conductive microspheres without affecting the height of the microspheres protruding from the surface due to excessive coating thickness.

[0023] Optionally, the polyurethane acrylate primer is formed by curing a composition of the following raw materials in parts by weight, comprising: 40-60 parts of polyurethane acrylate prepolymer, 5-20 parts of polyurethane acrylate oligomer, 20-30 parts of norborneol methacrylate, 10-20 parts of isooctyl acrylate, 1-2 parts of photoinitiator, 0.2-0.6 parts of low-temperature thermosetting initiator, 0-5 parts of hexagonal boron nitride nanosheets, and 0.1-0.5 parts of leveling agent; wherein the polyurethane acrylate prepolymer is formed by the reaction polymerization of a prepolymer of polyester polyol and aliphatic isocyanate and hydroxyethyl acrylate, and the polyurethane acrylate prepolymer has a molecular weight of 2000-6000 and contains 0.5%-2% by mass of unreacted isocyanate groups.

[0024] The composition of the above-mentioned raw materials in parts by weight constitutes a primer composition. The polyurethane acrylate prepolymer serves as the film-forming matrix and provides unreacted isocyanate groups. Polyurethane acrylate oligomers, norborneol methacrylate, and isooctyl acrylate all adjust the viscosity of the polyurethane acrylate primer layer. A photoinitiator (such as 2,4,6-trimethylbenzoyl-diphenylphosphine oxide) is used to initiate and accelerate the curing of the primer composition. A low-temperature thermosetting initiator can promote further polymerization of unreacted isocyanate groups or other side reactions after UV curing or under heat. The addition of hexagonal boron nitride nanosheets further enhances the thermal conductivity of the primer layer itself. A leveling agent ensures a smooth final film. The primer composition is thoroughly mixed before application to the substrate.

[0025] Furthermore, the present invention also provides a method for preparing a high thermal conductivity superhydrophobic insulating coating, wherein the high thermal conductivity superhydrophobic insulating coating includes any one of the foregoing descriptions, and the preparation method includes the following steps: The polyurethane acrylate composition is sprayed onto the substrate surface through a pressure spray can, and self-leveling is performed for 10-15 minutes after spraying to form a polyurethane acrylate base layer. Before the polyurethane acrylate primer is cured, thermally conductive microspheres with nano-protrusion structures are sprayed onto its surface by electrostatic powder spraying and arranged in a single layer to form an uncured coating. An LED light source is used to initially cure the uncured coating. The LED light source includes a UV-A light source and an infrared heating lamp with a wavelength of 3-6 μm. The curing time is 5-30 minutes. Unreacted isocyanate groups in the initially cured coating react with moisture in the environment, undergoing a second curing process.

[0026] First, the prepared polyurethane acrylate primer composition is loaded into a pressure spray can and evenly sprayed onto a clean substrate surface to form a wet film with a thickness of 50-70 μm. After spraying, it is allowed to stand at room temperature for 10-15 minutes to self-level, forming a smooth wet primer film. Before the wet primer film cures, pre-prepared powdered thermally conductive microspheres are sprayed onto the uncured wet primer film surface using an electrostatic powder spraying device under an electrostatic voltage of 40-80 kV. By adjusting the powder spraying amount and the moving speed, the thermally conductive microspheres can be controlled to spread and adhere to the wet film in a uniform monolayer. Subsequently, the substrate with the microspheres sprayed is placed under a curing device equipped with a UV-A (ultraviolet) band (320-400 nm) light source and a 3-6 μm wavelength infrared heating lamp, and both light sources are turned on simultaneously for curing. The curing time is set to 5-30 minutes. During this process, ultraviolet light induces rapid free radical polymerization and curing of the base coating, locking in the thermally conductive microspheres on the surface; infrared light provides heat to promote the interfacial bonding between the base coating and the functional surface layer and to release internal stress. After curing, any loosely adhered excess thermally conductive microsphere powder is gently removed with a brush or airflow. Finally, the substrate is placed in a room temperature environment, where the unreacted isocyanate groups in the base coating undergo a slow moisture-curing reaction with moisture in the air to form a polyurethane urea structure. This secondary curing process is completed gradually over several days to several weeks, further improving the crosslinking density, mechanical properties, and durability of the coating.

[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 This is an electron microscope image of the thermally conductive microspheres prepared in Example 1 of this invention; Figure 2 This is an electron microscope image of the nanoprotrusion structure of the thermally conductive microspheres prepared 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] Embodiments of the present invention are described in detail below, examples of which are illustrated 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 high thermal conductivity superhydrophobic insulating coating for protecting the housing of power distribution equipment cabinets, including a polyurethane acrylate base coating and a functional top layer; the polyurethane acrylate base coating includes unreacted isocyanate groups; the functional top layer is formed by arranging multiple thermally conductive microspheres with nano-protrusion structures on the surface of the polyurethane acrylate base coating; the nano-protrusion structures are formed on the surface of the thermally conductive microspheres by a sol-gel method.

[0032] In this embodiment, the high thermal conductivity and superhydrophobic insulating coating is a two-layer composite structure. The polyurethane acrylate base layer provides strong adhesion, high elasticity, and basic insulation to the power distribution equipment cabinet housing (such as tinplate, aluminum alloy, or engineering plastics). The functional surface layer provides superhydrophobicity and high thermal conductivity. Nanoscale protrusions are formed on the surface of the thermally conductive microspheres using a sol-gel method. Multiple nanoscale protrusions form a lotus leaf-like biomimetic structure, further improving the surface roughness of the functional surface layer. This allows water droplets to be held atop the nanoscale protrusions, resulting in a large contact angle (typically greater than 150°) and a very small roll-off angle (less than 10°), making it easy for the water droplets to roll off. This fundamentally prevents condensation, cuts off the electrolyte channels required for electrochemical corrosion, provides excellent hydrophobicity, and achieves long-term corrosion protection. Simultaneously, the functional surface layer, formed by the arrangement of multiple thermally conductive microspheres, significantly improves the coating's thermal conductivity, which is beneficial for heat dissipation of electronic components within the power distribution equipment cabinet housing.

[0033] The polyurethane acrylate primer layer is a continuous and uniform film, while the functional top layer is a discontinuous film, composed of a large number of thermally conductive microspheres densely arranged on the surface of the primer layer. For example... Figure 1 and Figure 2As shown, the surface morphology of the coating can be observed using a scanning electron microscope. Observation of a single thermally conductive microsphere reveals that its surface is covered with nanoscale protrusions, nodules, or particle accumulation structures, exhibiting high surface roughness. Therefore, this high thermal conductivity superhydrophobic insulating coating structurally achieves a composite of an elastic polymer underlayer and a surface layer of thermally conductive microspheres with nano-protrusion structures constructed using the sol-gel method. The polyurethane acrylate underlayer can be cured by ultraviolet light to fix the thermally conductive microspheres and secure the entire high thermal conductivity superhydrophobic insulating coating to the distribution box housing. Furthermore, the polyurethane acrylate underlayer includes reserved unreacted isocyanate groups. These unreacted isocyanate groups can further crosslink with trace amounts of moisture in the environment to form a hydrophobic polyurethane urea structure, preventing the penetration of trace amounts of moisture into the coating during equipment use and maintaining the coating's insulation properties.

[0034] The thermally conductive microspheres are spherical particles with a particle size of 20-1000 μm, a thermal conductivity greater than 30 W / (m·K), and a sphericity greater than 90%. The thermally conductive microspheres are selected from one or more of spherical alumina, spherical magnesium oxide, spherical boron nitride, and hexagonal boron nitride.

[0035] In this embodiment, thermally conductive microspheres are the basic building blocks for constructing the functional surface layer. These microspheres, with a particle size range of 20-1000 μm, are easily electrostatically sprayed onto a polyurethane acrylate primer to form a single-layer arrangement. Furthermore, the selected thermally conductive microspheres should have a thermal conductivity greater than 30 W / (m·K) to ensure the overall heat dissipation capacity of the high thermal conductivity superhydrophobic insulating coating. Additionally, the selected thermally conductive microspheres have a sphericity greater than 90%, ensuring smooth rolling and regular arrangement of the microspheres. For example, in one embodiment, spherical boron nitride with a particle size of 100 μm and a thermal conductivity of approximately 60 W / (m·K) can be used. In another embodiment, spherical alumina with a particle size of 200 μm and spherical boron nitride with a particle size of 50 μm can be mixed in a certain proportion to optimize the thermally conductive network filling the functional surface layer. The high thermal conductivity of the thermally conductive microsphere material itself can ensure the overall thermal conductivity of the coating. Its regular spherical geometry can ensure the formation of a uniform and regular single-layer arrangement on the surface of the base coating, thereby building a stable micron-level roughness on the surface of the high thermal conductivity superhydrophobic insulating coating.

[0036] The thermally conductive microspheres are spherical boron nitride with a particle size of 50-500 μm.

[0037] In this embodiment, spherical boron nitride not only possesses high thermal conductivity but also excellent insulation and low dielectric loss, making it an ideal filler for coatings used in power equipment, simultaneously meeting the requirements for insulation and heat dissipation. Preferably, spherical boron nitride with a particle size of 50-500 μm is selected. This particle size range ensures that the microspheres are large enough to create micron-level roughness for superhydrophobicity, while avoiding excessively large particle sizes that could affect the thin-layer spraying and flexibility of the high thermal conductivity superhydrophobic insulating coating. Furthermore, thermally conductive microspheres within this particle size range are readily available on the market and have good flowability, making them ideal for subsequent electrostatic spraying onto the surface of a polyurethane acrylate primer.

[0038] The formation of nanoprotrusion structures on the surface of thermally conductive microspheres via the sol-gel method includes the following steps: hydroxylating the thermally conductive microspheres; pretreating the hydroxylated thermally conductive microspheres with a silane coupling agent; immersing the pretreated thermally conductive microspheres in an organosilicon-inorganic silica sol, and forming nanoprotrusion structures on the surface of the thermally conductive microspheres after drying; and surface treating the thermally conductive microspheres with nanoprotrusions with an organofluorosilane coupling agent to reduce surface energy.

[0039] In this embodiment, when preparing the nanoprotrusion structure on the surface of the thermally conductive microspheres, the microspheres are first hydroxylated using a "piranha solution" (a mixed solution of concentrated sulfuric acid and hydrogen peroxide), introducing a large number of active -Si-OH groups onto the surface of the microspheres. Next, the microspheres are pretreated with silane coupling agents such as γ-aminopropyltriethoxysilane to enhance the bonding force between the microsphere surface and the subsequent organosilicon-inorganic silica sol. Then, the microspheres are immersed in the pre-prepared organosilicon-inorganic silica sol, allowing the sol on the surface of the microspheres to solidify, thereby forming the nanoprotrusion structure. Specifically, the solidification method is rotary evaporation or spray drying. Rotary evaporation refers to placing the sol-soaked thermally conductive microspheres into a rotary evaporator for vacuum distillation, where the solvent (such as ethanol, water, etc.) is rapidly evaporated and removed, the sol concentrates on the surface of the microspheres and undergoes a gelation reaction, ultimately forming a dried nanoprotrusion structure. Finally, the siloxane end of the organofluorosilane coupling agent reacts with the silanol groups on the surface of the nanoprotrusion structure to form a chemical bond, thereby grafting its extremely low surface energy fluorocarbon long chains onto the microsphere surface in the form of covalent bonds, thus reducing the surface energy of the thermally conductive microspheres. The nanoprotrusion structure formed by this method has good chemical stability and is not easily detached.

[0040] The organofluorosilane coupling agent is selected from one or more of heptadecafluorodecyltriethoxysilane, heptadecafluorodecyltrimethoxysilane, tridecafluorooctyltrimethoxysilane, and trifluoropropyltrichlorosilane.

[0041] In this embodiment, the long fluorocarbon chain in the organofluorosilane coupling agent is key to obtaining ultra-low surface energy. Heptadecyltriethoxysilane, heptadecyltrimethoxysilane, tridecafluorooctyltrimethoxysilane, and trifluoropropyltrichlorosilane all contain long fluorocarbon chains. Heptadecyltriethoxysilane and tridecafluorooctyltrimethoxysilane are preferred as the organofluorosilane coupling agents to provide excellent hydrophobic and oleophobic properties to the heat-conducting microspheres. In specific implementations, different organofluorosilane coupling agents can be selected to achieve the purpose of low surface energy modification.

[0042] The raw materials for preparing organosilicon-inorganic silica sol include, by weight, 100-200 parts of anhydrous ethanol, 30-50 parts of tetraethyl orthosilicate, 5-20 parts of ammonia, and 1-5 parts of silane coupling agent, wherein the silane coupling agent is selected from one or more of γ-aminopropyltriethoxysilane, vinyltriethoxysilane, vinyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-methacryloyloxypropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, and chloropropylsilane.

[0043] In this embodiment, anhydrous ethanol is used as the solvent, tetraethyl orthosilicate as the silicon source, and ammonia as the catalyst. The addition of silane coupling agents can adjust the flexibility and reactivity of the gel network in the organosilicon-inorganic silica sol to form a nanoprotrusion structure coating thermally conductive microspheres. Among the silane coupling agents used, γ-aminopropyltriethoxysilane can introduce amino groups, γ-glycidoxypropyltrimethoxysilane can introduce epoxy groups, and γ-methacryloyloxypropyltrimethoxysilane can introduce methacryloyloxy groups. The introduction of these active functional groups makes the formed nanoprotrusion structure more flexible due to the presence of certain organic components, reducing cracking and further enhancing the interfacial bonding strength between the functional top layer and the polyurethane acrylate base layer.

[0044] Organosilicon-inorganic silica sol is prepared by the following steps: anhydrous ethanol, tetraethyl orthosilicate, ammonia and silane coupling agent are mixed to obtain a solution. The solution is heated in a water bath at 55-60℃ and stirred at 350 rpm for 2-6 hours. After the reaction is completed, the solution is rotary evaporated until it is neutral to obtain nano-silica sol. Finally, 0-20 parts of neutral silica sol are added to the nano-silica sol to obtain organosilicon-inorganic silica sol.

[0045] In this embodiment, the process conditions ensured the stability of the organosilicon-inorganic silica sol and the controllability of the nanoprotrusion structure size. A water bath temperature of 55-60°C and a reaction time of 2-6 hours guaranteed the preparation of a stable organosilicon-inorganic silica sol. Rotary evaporation to neutrality after the reaction was to remove excess ammonia and prevent the prolonged presence of an alkaline environment from causing sol instability or adverse effects on subsequent processing. Adding neutral silica sol can adjust the solid content and viscosity of the sol.

[0046] The thickness of the polyurethane acrylate primer is 50%-90% of the diameter of the thermally conductive microspheres.

[0047] In this embodiment, the thickness range ensures that the base coating thickness is sufficient to fix the thermally conductive microspheres without affecting the height of the microspheres protruding from the surface due to excessive coating thickness. For example, for 100μm microspheres, a wet film thickness of 50-90μm for the base coating is suitable. During the spraying of the thermally conductive microspheres to the polyurethane acrylate base coating, by controlling the spraying parameters and the thickness of the polyurethane acrylate base coating, the final cured base coating thickness meets this proportional relationship.

[0048] The polyurethane acrylate primer coating is formed by curing a composition of the following raw materials in parts by weight, including: 40-60 parts of polyurethane acrylate prepolymer, 5-20 parts of polyurethane acrylate oligomer, 20-30 parts of norborneol methacrylate, 10-20 parts of isooctyl acrylate, 1-2 parts of photoinitiator, 0.2-0.6 parts of low-temperature thermosetting initiator, 0-5 parts of hexagonal boron nitride nanosheets, and 0.1-0.5 parts of leveling agent; wherein, 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 2000-6000 and contains 0.5%-2% by mass of unreacted isocyanate groups.

[0049] In this embodiment, the composition of the above-mentioned raw materials in parts by weight constitutes a primer composition. The polyurethane acrylate prepolymer serves as the film-forming matrix and provides unreacted isocyanate groups. The polyurethane acrylate oligomer, norborneol methacrylate, and isooctyl acrylate all adjust the viscosity of the polyurethane acrylate primer coating. A photoinitiator (such as 2,4,6-trimethylbenzoyl-diphenylphosphine oxide) is used to initiate and accelerate the curing of the primer composition. A low-temperature thermosetting initiator can promote further polymerization of unreacted isocyanate groups or other side reactions after UV curing or under heat. The addition of hexagonal boron nitride nanosheets further enhances the thermal conductivity of the primer coating itself. A leveling agent ensures a smooth final film. The primer composition is mixed uniformly before being applied to the substrate.

[0050] As a preferred embodiment, the high-elasticity UV primer made of polyurethane acrylate is composed of the following raw materials in parts by weight: 50-55 parts of polyurethane acrylate prepolymer, 5-10 parts of polyurethane acrylate oligomer, 25-30 parts of norborneol methacrylate, 10-15 parts of isooctyl acrylate, 1-1.5 parts of photoinitiator, 0.2-0.6 parts of low-temperature thermosetting initiator, 0-2 parts of hexagonal boron nitride nanosheets, and 0.1-0.5 parts of leveling agent. The polyurethane acrylate prepolymer is produced by reacting polyester polyol with aliphatic isocyanate to form a prepolymer, which is then grafted and copolymerized with hydroxyethyl acrylate. Its number-average molecular weight is 4000-6000, and it contains 0.5%-1% by mass of unreacted isocyanate groups. Each component is optimized within a narrower range to ensure sufficient thermal conductivity, reflectivity, UV shielding, and application performance of the coating, while avoiding the potential negative impact of excessive addition on coating transparency, mechanical properties, and interfacial bonding.

[0051] Furthermore, the present invention also provides a method for preparing a high thermal conductivity superhydrophobic insulating coating, wherein the high thermal conductivity superhydrophobic insulating coating includes any of the foregoing high thermal conductivity superhydrophobic insulating coatings, and the preparation method includes the following steps: The polyurethane acrylate composition is sprayed onto the substrate surface through a pressure spray can, and self-leveling is performed for 10-15 minutes after spraying to form a polyurethane acrylate base layer. Before the polyurethane acrylate primer is cured, thermally conductive microspheres with nano-protrusion structures are sprayed onto its surface by electrostatic powder spraying and arranged in a single layer to form an uncured coating. The uncured coating is initially cured using an LED light source, which includes a UV-A light source and an infrared heating lamp with a wavelength of 3-6µm. The curing time is 5-30 minutes. Unreacted isocyanate groups in the initially cured coating react with moisture in the environment, undergoing a second curing process.

[0052] In this embodiment, the prepared polyurethane acrylate primer composition is first loaded into a pressure spray can and uniformly sprayed onto a clean substrate surface to form a wet film with a thickness of 50-70 μm. After spraying, the film is allowed to stand at room temperature for 10-15 minutes to self-level, forming a smooth wet primer film. Before the wet primer film cures, pre-prepared powdered thermally conductive microspheres are sprayed onto the uncured wet primer film surface using an electrostatic powder spraying device under an electrostatic voltage of 40-80 kV. By adjusting the powder spraying amount and the moving speed, the thermally conductive microspheres can be controlled to spread and adhere to the wet film in a uniform monolayer. Subsequently, the substrate with the microspheres sprayed is placed under a curing device equipped with a UV-A (i.e., ultraviolet light) band (320-400 nm) light source and a 3-6 μm wavelength infrared heating lamp. Both light sources are turned on simultaneously for irradiation and curing, with the curing time set to 5-30 minutes. During this process, ultraviolet light induces rapid free radical polymerization and curing of the base coating, locking in the thermally conductive microspheres on the surface; infrared light provides heat to promote the interfacial bonding between the base coating and the functional surface layer and to release internal stress. After curing, any loosely adhered excess thermally conductive microsphere powder is gently removed with a brush or airflow. Finally, the substrate is placed in a room temperature environment, where the unreacted isocyanate groups in the base coating undergo a slow moisture-curing reaction with moisture in the air to form a polyurethane urea structure. This secondary curing process is completed gradually over several days to several weeks, further improving the crosslinking density, mechanical properties, and durability of the coating.

[0053] Preparation Example 1: At room temperature, 200 g of anhydrous ethanol was placed in a reaction vessel, and 50 g of tetraethyl orthosilicate, 20 g of 30% ammonia solution, and 5 g of γ-aminopropyltriethoxysilane were added sequentially with stirring. The mixture was placed in a water bath at 55-60°C and stirred at 350 rpm for 4 hours. After the reaction was complete, the ethanol and ammonia solution were removed from the system at room temperature using a rotary evaporator until the solution was neutral. Subsequently, 5 g of neutral silica sol with a solid content of 35% was added to the resulting neutral sol and stirred until homogeneous to obtain an organosilicon-inorganic silica sol for later use.

[0054] Spherical boron nitride microspheres with an average particle size of 100 micrometers were ultrasonically cleaned sequentially in anhydrous ethanol and deionized water to remove physically adsorbed impurities from the surface. After cleaning, the microspheres were immersed in a freshly prepared strong oxidizing solution for surface hydroxylation treatment. The strong oxidizing solution was prepared by mixing 98% concentrated sulfuric acid and 30% hydrogen peroxide in a volume ratio of 3:1. The treatment conditions were: immersion at room temperature for 12 hours. After treatment, the microspheres were repeatedly washed with a large amount of deionized water until the washing solution was neutral, and then dried in an oven at 80 degrees Celsius. The dried hydroxylated microspheres were immersed in an ethanol-water solution of γ-glycidyl etheroxypropyltrimethoxysilane for 2 hours, then removed and dried again to complete the surface pretreatment. The pretreated microspheres were immersed in the aforementioned prepared organosilicon-inorganic silica sol and dispersed for 30 minutes. Subsequently, the microspheres were dried using a spray dryer, causing the sol to gel on the surface of the microspheres and form nano-protrusion structures. After drying, the microspheres were dried again at 100 degrees Celsius. Finally, the microspheres were immersed in an ethanol solution of heptadecafluorodecyltriethoxysilane at room temperature for 1 hour to modify their surface hydrophobicity. After immersion, they were dried at 80°C to obtain low surface energy thermally conductive microspheres for later use. Electron microscopy images of the low surface energy thermally conductive microspheres are shown below. Figure 1 and Figure 2 As shown.

[0055] Take 50g of polyurethane acrylate prepolymer, 10g of polyurethane acrylate oligomer, 25g of norborneol methacrylate, 15g of isooctyl acrylate, 1.5g of photoinitiator (TPO), 0.5g of hexagonal boron nitride nanosheets, 0.5g of leveling agent (TEGO100), and 0.5g of low-temperature thermosetting initiator (benzoyl peroxide). Place them in a container and stir until completely dissolved and mixed evenly to obtain a primer composition. Before spraying, add 0.3g of N,N-dimethylaniline to the composition and stir again until evenly mixed.

[0056] The above-mentioned primer composition was filled into a pressure spray can and sprayed onto a clean tinplate test plate, controlling the wet film thickness to be 50-70 micrometers. After spraying, the test plate was placed horizontally at room temperature for self-leveling for 10-15 minutes. Immediately afterwards, using an electrostatic powder coating device, the aforementioned prepared thermally conductive microsphere powder was sprayed onto the uncured primer wet film surface. The electrostatic voltage was set to 60 kV, and the spraying parameters were adjusted to ensure a uniform and dense monolayer arrangement of the thermally conductive microspheres on the surface. After spraying, the test plate was transferred to a curing device and simultaneously cured using a high-power LED light source containing UV-A and infrared bands for 15 minutes. After curing, any loosely adhered microsphere powder was gently brushed off the surface. The resulting coating was left at room temperature for 7 days, allowing the ambient humidity to cause secondary curing. After complete curing, the static water contact angle of the superhydrophobic insulating coating was tested, and the results are as follows: Figure 4 As shown.

[0057] In addition, the fracture strength and elongation at break of the primer composition were tested after curing it separately into a primer layer. Figure 3 As shown, the horizontal axis represents the fracture elongation and the vertical axis represents the fracture strength.

[0058] Preparation Example 2: At room temperature, 150 g of anhydrous ethanol was placed in a reaction vessel, and 30 g of tetraethyl orthosilicate, 10 g of 30% ammonia solution, and 5 g of γ-methacryloyloxypropyltrimethoxysilane were added sequentially with stirring. The mixture was placed in a water bath at 55-60°C and stirred at 350 rpm for 6 hours. After the reaction was complete, the ethanol and ammonia solution were removed from the system at room temperature using a rotary evaporator until the solution was neutral. Subsequently, 15 g of neutral silica sol with a solid content of 35% was added to the resulting neutral sol and stirred until homogeneous to obtain an organosilicon-inorganic silica sol for later use.

[0059] Spherical alumina particles with an average diameter of 50 micrometers were ultrasonically cleaned sequentially in anhydrous ethanol and deionized water to remove physically adsorbed impurities from the surface. After cleaning, the particles were immersed in a freshly prepared strong oxidizing solution for surface hydroxylation treatment. The strong oxidizing solution was prepared by mixing 98% concentrated sulfuric acid and 30% hydrogen peroxide in a volume ratio of 3:1. The treatment conditions were: soaking at room temperature for 6 hours. After treatment, the particles were repeatedly washed with a large amount of deionized water until the washing solution was neutral, and then dried in an oven at 80 degrees Celsius. The dried hydroxylated microspheres were immersed in an ethanol-water solution of γ-glycidyl etheroxypropyltrimethoxysilane for 2 hours, then removed and dried again to complete the surface pretreatment. The pretreated microspheres were immersed in the aforementioned prepared organosilicon-inorganic silica sol and dispersed for 30 minutes. Subsequently, the microspheres were dried using a spray dryer, causing the sol to gel on the surface of the microspheres and form nano-protrusion structures. After drying, the microspheres were dried again at 100 degrees Celsius. Finally, the microspheres were placed in an ethanol solution of heptadecafluorodecyltrimethoxysilane and immersed at room temperature for 1 hour to modify the surface hydrophobicity. After removal, they were dried at 80 degrees Celsius to obtain low surface energy thermally conductive microspheres for later use.

[0060] Take 50 g of polyurethane acrylate prepolymer (molecular weight 5000, residual isocyanate group mass fraction 1%), 20 g of polyurethane acrylate oligomer (Ebecryl 8413), 20 g of norborneol methacrylate, 10 g of isooctyl acrylate, 0.8 g of photoinitiator (TPO), 0.3 g of leveling agent (TEGO100), and 0.5 g of low-temperature thermosetting initiator (benzoyl peroxide). Place them in a container and stir until completely dissolved and mixed evenly to obtain the primer composition. Before spraying, add 0.3 g of N,N-dimethylaniline to the composition and stir again until homogeneous.

[0061] The aforementioned primer composition was filled into a pressure spray can and sprayed onto a clean tinplate test panel, controlling the wet film thickness to be 35-40 micrometers. After spraying, the test panel was placed horizontally at room temperature and allowed to self-level for 10 minutes. Immediately afterwards, using an electrostatic powder coating device, the aforementioned prepared thermally conductive microsphere powder was sprayed onto the uncured primer wet film surface. The electrostatic voltage was set to 50 kV, and the spraying parameters were adjusted to ensure a uniform and dense monolayer arrangement of the thermally conductive microspheres on the surface. After spraying, the test panel was transferred to a curing device and simultaneously cured using a high-power LED light source containing UV-A and infrared bands for 15 minutes. After curing, any loosely adhered microsphere powder was gently brushed away with a soft brush. The resulting coating was left at room temperature for 7 days, allowing the ambient humidity to cause secondary curing.

[0062] Preparation Example 3: At room temperature, 200 g of anhydrous ethanol was placed in a reaction vessel, and 50 g of tetraethyl orthosilicate, 20 g of 30% ammonia solution, and 5 g of γ-aminopropyltriethoxysilane were added sequentially with stirring. The mixture was placed in a water bath at 55-60°C and stirred at 350 rpm for 4 hours. After the reaction was complete, the ethanol and ammonia solution were removed from the system at room temperature using a rotary evaporator until the solution was neutral. Subsequently, 5 g of neutral silica sol with a solid content of 35% was added to the resulting neutral sol and stirred until homogeneous to obtain an organosilicon-inorganic silica sol for later use.

[0063] Spherical magnesium oxide particles with an average particle size of 100 micrometers were ultrasonically cleaned sequentially in anhydrous ethanol and deionized water to remove physically adsorbed impurities from the surface. After cleaning, the particles were immersed in a freshly prepared strong oxidizing solution for surface hydroxylation treatment. The strong oxidizing solution was prepared by mixing 98% concentrated sulfuric acid and 30% hydrogen peroxide in a volume ratio of 3:1. The treatment conditions were: soaking at room temperature for 2 hours. After treatment, the particles were repeatedly washed with a large amount of deionized water until the washing solution was neutral, and then dried in an oven at 80 degrees Celsius. The dried hydroxylated microspheres were immersed in an ethanol-water solution of γ-methacryloyloxypropyltrimethoxysilane for 2 hours, then removed and dried again to complete the surface pretreatment. The pretreated microspheres were immersed in the aforementioned prepared organosilicon-inorganic silica sol and dispersed for 30 minutes. Subsequently, the microspheres were dried using a spray dryer, causing the sol to gel on the surface of the microspheres and form nano-protrusion structures. After drying, the microspheres were dried again at 100 degrees Celsius. Finally, the microspheres were placed in an ethanol solution of tridecafluorooctyltrimethoxysilane and immersed at room temperature for 1 hour to modify the surface hydrophobicity. After being removed, they were dried at 80 degrees Celsius to obtain low surface energy thermally conductive microspheres for later use.

[0064] Take 50 g of polyurethane acrylate prepolymer (molecular weight 5000, residual isocyanate group mass fraction 1%), 10 g of polyurethane acrylate oligomer (Ebecryl 8413), 25 g of norborneol methacrylate, 15 g of isooctyl acrylate, 0.8 g of photoinitiator (TPO), 1.0 g of hexagonal boron nitride nanosheets, 0.5 g of leveling agent (TEGO100), and 0.5 g of low-temperature thermosetting initiator (benzoyl peroxide). Place them in a container and stir until completely dissolved and mixed evenly to obtain the primer composition. Before spraying, add 0.3 g of N,N-dimethylaniline to the composition and stir again until homogeneous.

[0065] The aforementioned primer composition was filled into a pressure spray can and sprayed onto a clean tinplate test panel, controlling the wet film thickness to be 50-70 micrometers. After spraying, the test panel was placed horizontally at room temperature for 10-15 minutes to self-level. Immediately afterwards, using an electrostatic powder coating device, the aforementioned prepared thermally conductive microsphere powder was sprayed onto the uncured primer wet film surface. The electrostatic voltage was set to 60 kV, and the spraying parameters were adjusted to ensure a uniform and dense monolayer arrangement of the thermally conductive microspheres on the surface. After spraying, the test panel was transferred to a curing device and simultaneously cured using a high-power LED light source containing UV-A bands (wavelength 320-400 nm) and infrared bands (wavelength 3-6 micrometers) for 15 minutes. After curing, any loosely adhered microsphere powder was gently brushed away with a soft brush. The resulting coating was left at room temperature for 7 days, allowing the ambient humidity to cause secondary curing.

[0066] Preparation Example 4: At room temperature, 200 g of anhydrous ethanol was placed in a reaction vessel, and 50 g of tetraethyl orthosilicate, 20 g of 30% ammonia solution, and 5 g of γ-glycidoxypropyltrimethoxysilane were added sequentially with stirring. The mixture was placed in a water bath at 55-60°C and stirred at 350 rpm for 4 hours. After the reaction was complete, the ethanol and ammonia solution were removed from the system at room temperature using a rotary evaporator until the solution was neutral, yielding nano-silica sol for later use.

[0067] Spherical boron nitride particles with average particle sizes of 100 μm and 300 μm were mixed at a mass ratio of 7:3. The mixed microspheres were then ultrasonically cleaned sequentially in anhydrous ethanol and deionized water to remove surface-adsorbed impurities. After cleaning, the mixed microspheres were immersed in a freshly prepared strong oxidizing solution for surface hydroxylation treatment. The strong oxidizing solution was prepared by mixing 98% concentrated sulfuric acid and 30% hydrogen peroxide at a volume ratio of 3:1. The treatment conditions were: immersion at room temperature for 12 hours. After treatment, the microspheres were repeatedly washed with a large amount of deionized water until the washing solution was neutral, and then dried in an oven at 80°C. The dried hydroxylated mixed microspheres were then immersed in an ethanol-water solution of γ-glycidyl etheroxypropyltrimethoxysilane for 2 hours, removed, and dried again to complete the surface pretreatment. The pretreated mixed microspheres were then immersed in the aforementioned prepared nano-silica sol and dispersed for 30 minutes. The microspheres were then dried using a spray dryer, causing the sol to gel on the surface of the microspheres and form nanoprotrusion structures. After drying, they were further dried at 100 degrees Celsius. Finally, the microspheres were placed in an ethanol solution of heptadecafluorodecyltriethoxysilane and immersed at room temperature for 1 hour to modify their surface hydrophobicity. After removal, they were dried at 80 degrees Celsius to obtain low surface energy thermally conductive microspheres for later use.

[0068] Take 60 g of polyurethane acrylate prepolymer (molecular weight 6000, residual isocyanate group mass fraction 1%), 25 g of norborneol methacrylate, 15 g of isooctyl acrylate, 0.8 g of photoinitiator (TPO), 0.5 g of leveling agent (TEGO100), and 0.5 g of low-temperature thermosetting initiator (benzoyl peroxide). Place them in a container and stir until completely dissolved and mixed evenly to obtain a primer composition. Before spraying, add 0.3 g of N,N-dimethylaniline to the composition and stir again until evenly mixed.

[0069] The aforementioned primer composition was filled into a pressure spray can and sprayed onto a clean tinplate test panel, controlling the wet film thickness to be 150-200 micrometers. After spraying, the test panel was placed horizontally at room temperature for 10-15 minutes to self-level. Immediately afterwards, using an electrostatic powder coating device, the aforementioned mixed-size thermally conductive microsphere powder was sprayed onto the uncured primer wet film surface. The electrostatic voltage was set to 70 kV, and the spraying parameters were adjusted to ensure a uniform and dense monolayer arrangement of the thermally conductive microspheres on the surface. After spraying, the test panel was transferred to a curing device and simultaneously cured using a high-power LED light source containing UV-A bands (wavelength 320-400 nm) and infrared bands (wavelength 3-6 micrometers) for 30 minutes. After curing, any loosely adhered microsphere powder was gently brushed away with a soft brush. The resulting coating was left at room temperature for 7 days, allowing the ambient humidity to cause secondary curing.

[0070] Preparation Example 5: At room temperature, 200 g of anhydrous ethanol was placed in a reaction vessel, and 50 g of tetraethyl orthosilicate, 20 g of 30% ammonia solution, and 5 g of γ-aminopropyltriethoxysilane were added sequentially with stirring. The mixture was placed in a water bath at 55-60°C and stirred at 350 rpm for 4 hours. After the reaction was complete, the ethanol and ammonia solution were removed from the system at room temperature using a rotary evaporator until the solution was neutral. Subsequently, 5 g of neutral silica sol with a solid content of 35% was added to the resulting neutral sol and stirred until homogeneous to obtain an organosilicon-inorganic silica sol for later use.

[0071] Spherical alumina particles with an average diameter of 50 μm, spherical boron nitride particles with an average diameter of 100 μm, and spherical alumina particles with an average diameter of 200 μm were mixed in a mass ratio of 3:5:2. The mixed particles were then ultrasonically cleaned sequentially in anhydrous ethanol and deionized water to remove physically adsorbed impurities from the surface. After cleaning, the mixed particles were immersed in a freshly prepared strong oxidizing solution for surface hydroxylation treatment. The strong oxidizing solution was prepared by mixing 98% concentrated sulfuric acid and 30% hydrogen peroxide in a volume ratio of 3:1. The treatment conditions were: immersion at room temperature for 12 hours. After treatment, the particles were repeatedly washed with a large amount of deionized water until the washing solution was neutral, and then dried in an oven at 80°C. The dried hydroxylated mixed microspheres were immersed in an ethanol-water solution of γ-glycidyl etheroxypropyltrimethoxysilane for 2 hours, then removed and dried again to complete the surface pretreatment. The pretreated mixed microspheres were then immersed in the aforementioned prepared organosilicon-inorganic silica sol and dispersed for 30 minutes. The microspheres were then dried using a spray dryer, causing the sol to gel on the surface of the microspheres and form nanoprotrusion structures. After drying, they were further dried at 100 degrees Celsius. Finally, the microspheres were placed in an ethanol solution of heptadecafluorodecyltriethoxysilane and immersed at room temperature for 1 hour to modify their surface hydrophobicity. After removal, they were dried at 80 degrees Celsius to obtain low surface energy thermally conductive microspheres for later use.

[0072] Take 50 g of polyurethane acrylate prepolymer (molecular weight 5000, residual isocyanate group mass fraction 1%), 10 g of polyurethane acrylate oligomer (Ebecryl 8413), 25 g of norborneol methacrylate, 15 g of isooctyl acrylate, 0.8 g of photoinitiator (TPO), 0.5 g of leveling agent (TEGO100), and 0.5 g of low-temperature thermosetting initiator (benzoyl peroxide). Place them in a container and stir until completely dissolved and mixed evenly to obtain the primer composition. Before spraying, add 0.3 g of N,N-dimethylaniline to the composition and stir again until homogeneous.

[0073] The aforementioned primer composition was filled into a pressure spray can and sprayed onto a clean tinplate test panel, controlling the wet film thickness to be 50-70 micrometers. After spraying, the test panel was placed horizontally at room temperature for 10-15 minutes to self-level. Immediately afterwards, using an electrostatic powder coating device, the aforementioned mixed thermally conductive microsphere powder was sprayed onto the uncured primer wet film surface. The electrostatic voltage was set to 60 kV, and the spraying parameters were adjusted to ensure a uniform and dense monolayer arrangement of the thermally conductive microspheres on the surface. After spraying, the test panel was transferred to a curing device and simultaneously cured using a high-power LED light source containing UV-A bands (wavelength 320-400 nm) and infrared bands (wavelength 3-6 micrometers) for 15 minutes. After curing, any loosely adhered microsphere powder was gently brushed away with a soft brush. The resulting coating was left at room temperature for 7 days, allowing the ambient humidity to cause secondary curing.

[0074] Comparative example: This comparative example prepared spherical boron nitride microspheres (average particle size 100 μm) of the same specifications as in Preparation Example 1, but without the sol-gel method for constructing nanoprotrusion structures. Specifically, the cleaned boron nitride microspheres were directly immersed in an ethanol-water solution of γ-glycidoxypropyltrimethoxysilane for 2 hours, then removed and dried at 80°C. Subsequently, they were immersed in an ethanol-water solution of trifluoropropyltrichlorosilane for another 2 hours, then spray-dried and dried to obtain comparative microspheres with only silane surface modification. The formulation, preparation method, and subsequent spraying application process of the primer composition were exactly the same as in Preparation Example 1.

[0075] 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 Comparative Example 1 were tested using an SDC-100 semi-automatic contact angle measuring instrument. The results are shown in Table 2.

[0076] Table 2: Surface water droplet test results of the superhydrophobic insulating coatings prepared in Examples 1-5 and Comparative Examples 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.

[0077] 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.

[0078] 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.

[0079] 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.

[0080] 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 high thermal conductivity superhydrophobic insulating coating for protecting the housing of power distribution equipment cabinets, characterized in that, Includes a polyurethane acrylate base coat and a functional top coat; The polyurethane acrylate undercoat includes unreacted isocyanate groups; The functional surface layer is formed by arranging multiple thermally conductive microspheres with nano-protrusion structures on the surface of the polyurethane acrylate base coating; Nanoprotrusion structures were formed on the surface of thermally conductive microspheres using the sol-gel method.

2. The high thermal conductivity superhydrophobic insulating coating according to claim 1, characterized in that, The thermally conductive microspheres are spherical particles with a particle size of 20-1000 μm, a thermal conductivity greater than 30 W / (m·K), and a sphericity greater than 90%. The thermally conductive microspheres are selected from one or more of spherical alumina, spherical magnesium oxide, spherical boron nitride, and hexagonal boron nitride.

3. The high thermal conductivity superhydrophobic insulating coating according to claim 2, characterized in that, The thermally conductive microspheres are spherical boron nitride with a particle size of 50-500 μm.

4. The high thermal conductivity superhydrophobic insulating coating according to claim 1, characterized in that, The process of forming nanoprotrusion structures on the surface of thermally conductive microspheres via the sol-gel method includes the following steps: Hydroxylation treatment was performed on the thermally conductive microspheres; The hydroxylated thermally conductive microspheres were pretreated with a silane coupling agent. The pretreated thermally conductive microspheres were immersed in an organosilicon-inorganic silica sol and dried to form nano-protrusion structures on the surface of the thermally conductive microspheres. Surface treatment of thermally conductive microspheres with nanoprotrusions using organofluorosilane coupling agents can reduce surface energy.

5. The high thermal conductivity superhydrophobic insulating coating according to claim 4, characterized in that, The organofluorosilane coupling agent is selected from one or more of heptadecafluorodecyltriethoxysilane, heptadecafluorodecyltrimethoxysilane, tridecafluorooctyltrimethoxysilane, and trifluoropropyltrichlorosilane.

6. The high thermal conductivity superhydrophobic insulating coating according to claim 4, characterized in that, The raw materials for preparing organosilicon-inorganic silica sol include, by weight, 100-200 parts of anhydrous ethanol, 30-50 parts of tetraethyl orthosilicate, 5-20 parts of ammonia, and 1-5 parts of silane coupling agent, wherein the silane coupling agent is selected from one or more of γ-aminopropyltriethoxysilane, vinyltriethoxysilane, vinyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-methacryloyloxypropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, and chloropropylsilane.

7. The high thermal conductivity superhydrophobic insulating coating according to claim 4, characterized in that, Organosilicon-inorganic silica sol is prepared by the following steps: anhydrous ethanol, tetraethyl orthosilicate, ammonia and silane coupling agent are mixed to obtain a solution. The solution is heated in a water bath at 55-60℃ and stirred at 350 rpm for 2-6 hours. After the reaction is completed, the solution is rotary evaporated until it is neutral to obtain nano-silica sol. Finally, 0-20 parts of neutral silica sol are added to the nano-silica sol to obtain organosilicon-inorganic silica sol.

8. The high thermal conductivity superhydrophobic insulating coating according to claim 1, characterized in that, The thickness of the polyurethane acrylate base coating is 50%-90% of the diameter of the thermally conductive microspheres.

9. The high thermal conductivity superhydrophobic insulating coating according to claim 1, characterized in that, The polyurethane acrylate primer coating is formed by curing a composition of the following raw materials in parts by weight, including: 40-60 parts of polyurethane acrylate prepolymer, 5-20 parts of polyurethane acrylate oligomer, 20-30 parts of norborneol methacrylate, 10-20 parts of isooctyl acrylate, 1-2 parts of photoinitiator, 0.2-0.6 parts of low-temperature thermosetting initiator, 0-5 parts of hexagonal boron nitride nanosheets, and 0.1-0.5 parts of leveling agent; wherein, the polyurethane acrylate prepolymer is formed by the reaction polymerization of a prepolymer of polyester polyol and aliphatic isocyanate and hydroxyethyl acrylate, the polyurethane acrylate prepolymer has a molecular weight of 2000-6000 and contains 0.5%-2% by mass of unreacted isocyanate groups.

10. A method for preparing a high thermal conductivity superhydrophobic insulating coating, characterized in that, The high thermal conductivity superhydrophobic insulating coating comprises the high thermal conductivity superhydrophobic insulating coating according to any one of claims 1 to 9, and the preparation method comprises the following steps: The polyurethane acrylate composition is sprayed onto the substrate surface using a pressure spray can. After spraying, it self-levels for 10-15 minutes to form a polyurethane acrylate base layer. Before the polyurethane acrylate base layer cures, thermally conductive microspheres with nano-protrusion structures are sprayed onto its surface by electrostatic powder spraying and arranged in a single layer to form an uncured coating. An LED light source is used to initially cure the uncured coating. The LED light source includes a UV-A light source and an infrared heating lamp with a wavelength of 3-6 μm. The curing time is 5-30 minutes. Unreacted isocyanate groups in the initially cured coating react with moisture in the environment, undergoing a second curing process.

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