Radiation cooling coating for photocuring driven phase separation as well as preparation method and application of radiation cooling coating

Abstract

The invention relates to the technical field of radiation cooling and functional coatings, and particularly discloses a photocuring-driven phase-separated radiation cooling coating as well as a preparation method and application thereof. The coating is composed of a gradient volatilization solvent system composed of an acrylamide monomer, a cross-linking agent, a photoinitiator and water / ethyl alcohol / polyethylene glycol 400, polymerization curing is initiated through ultraviolet light, a micro-nano hierarchical porous structure is formed through induction of the gradient volatilization characteristic of a mixed solvent, synergistic enhancement of the solar reflectivity and the infrared emissivity is achieved, and the coating has the advantages of being high in light transmittance, high in light transmittance and the like. And the efficient passive cooling effect is achieved. The photocuring-phase separation coupling technology is adopted, the pore structure of the coating can be accurately regulated and controlled without complex equipment, the method has the advantages of being simple in technology, environmentally friendly, wide in applicability and the like, the limitation that a traditional material depends on precision machining or multi-layer compounding is overcome, and the method is suitable for building energy saving, electronic heat management and large-scale coating of outdoor equipment.

Description

Technical Field

[0001] This invention relates to the field of radiation cooling and functional coatings, specifically disclosing a photocurable radiation cooling coating with phase separation driven by radiation, its preparation method, and its application. Background Technology

[0002] According to the International Energy Agency (IEA) 2025 Global Building Energy Consumption Report, air conditioning systems account for 36.5% of total energy consumption in the building sector, becoming a key factor contributing to rising global energy pressures. In tropical and subtropical regions (such as Southeast Asia and the Middle East), energy consumption during peak cooling demand periods can reach as high as 58-63% (World Bank 2025 Climate Resilience Buildings data). This high energy consumption directly results in approximately 5.1 million tons of CO2 equivalent greenhouse gas emissions annually (UNEP 2025 Refrigeration Industry Assessment), exacerbating the urban heat island effect (widening the temperature difference between urban and suburban areas to 4-7°C in summer) and releasing large amounts of hydrofluorocarbons (HFCs) through refrigerant leaks—whose global warming potential (GWP) can be 700-4000 times that of CO2 (based on AR6 assessment values). Against this backdrop, passive cooling technologies (such as radiant cooling materials) have been listed as a key area for promotion by the IEA from 2025 to 2030, as their zero-energy characteristics can reduce cooling demand by more than 40%.

[0003] Passive radiation cooling technology, as a zero-energy cooling solution, dissipates heat from objects into the low-temperature outer space through an "atmospheric transparency window" (8-13 μm) in the form of infrared radiation, possessing enormous energy-saving potential and application prospects. However, existing radiation cooling materials still face significant bottlenecks in practical large-scale applications: traditional inorganic materials (such as photonic crystals and multilayer films) rely on complex processes such as high-temperature sintering, precision photolithography, or physical vapor deposition, which are costly and difficult to fabricate on a large scale; while organic polymer coatings are easy to process, they often require the addition of high-refractive-index fillers (such as TiO2) or rely on sacrificial pore-forming agents (such as NH4HCO3) to construct light-scattering structures, which can easily lead to problems such as decreased mechanical properties, poor weather resistance, and environmental residues. Especially in photocuring systems, conventional acrylic resins have a dense structure after curing and lack effective built-in scattering centers, making it difficult to simultaneously achieve high solar reflectivity and high infrared emissivity.

[0004] CN114672205A discloses a radiation cooling coating and a surface coating method. This method utilizes a polymer-containing mixture through a phase inversion process to form a porous structure. Specifically, the polymer is dissolved in a volatile polar solvent (NMP), and then dissolved in deionized water. During the curing process, the volatile polar solvent (NMP) rapidly evaporates, leaving behind the polymer and water in the coating. The polymer and water undergo phase separation, and nanoscale or microscale pores are formed as the water evaporates. However, NMP is not environmentally friendly. Therefore, it is necessary to develop a high-performance radiation cooling coating that is simple to process and environmentally friendly. Summary of the Invention

[0005] To address the problems of complex preparation processes, high costs, and insufficient environmental friendliness in existing radiation cooling materials, this invention aims to provide a photocurable, phase-separation-driven radiation cooling coating with simplified components, simple process, excellent performance, and suitability for large-scale coating, along with its preparation method and applications. Utilizing the synergistic mechanism of photocuring polymerization and solvent evaporation-induced phase separation, a porous structure is formed in situ within the coating, enabling it to exhibit highly efficient solar light reflection and infrared radiation, providing an innovative solution for the industrial-scale preparation of radiation cooling coatings.

[0006] This invention is achieved through the following technical solution: In a first aspect, the present invention provides a radiation cooling coating for photocuring driven phase separation, comprising, by weight, the following components: 20-35 parts polymer monomer, 0.01-0.2 parts crosslinking agent, 0.01-0.2 parts photoinitiator and 65-80 parts mixed solvent; The polymer monomer is selected from one or more of acrylamide monomer, N-isopropylacrylamide, and acrylic acid; The mixed solvent is selected from one or more of water, ethanol and polyethylene glycol 400.

[0007] Secondly, the present invention provides a method for preparing a radiation-cooled coating with photocurable phase separation, comprising the following steps: (1) Disperse the polymer monomer and crosslinking agent in a mixed solvent to obtain solution A; (2) Under light-protected conditions, a photoinitiator was added to solution A and stirred to obtain a radiation-cooled coating that drives phase separation through photocuring.

[0008] Thirdly, the present invention provides an application of a photocurable phase-separated radiation-cooled coating in the preparation of a coating containing a porous structure.

[0009] The technical solution of the present invention has at least the following advantages and beneficial effects: (1) This invention is based on a polymer monomer / N,N'-methylenebisacrylamide oligomer system. During the photocuring process, the polymer monomer undergoes cross-linking under the action of a cross-linking agent and a photoinitiator to form a polymer. Through polymerization-induced phase separation, the solvent evaporates simultaneously to form a porous structure. Based on the synergistic effect of solvent evaporation and photocuring, the dual processes of "in-situ pore formation" and "cross-linking curing" are achieved simultaneously. Only simple steps such as uniform solution mixing, spraying, and UV / visible light irradiation are required to form a coating network with a micro-nano hierarchical porous structure (pore size adjustable from 50-150 nm) and high cross-linking density within seconds. Compared with traditional preparation methods that rely on high-temperature sintering or multi-step templates, this method truly achieves a high degree of simplification in terms of composition, process, and cost.

[0010] (2) The prepared coating exhibits excellent optical properties. Its high infrared emission characteristics (emissivity ≥95%) originate from the characteristic vibrational absorption of CH and NH bonds in the acrylamide copolymer network within the 8-13 μm atmospheric window band. Furthermore, by precisely controlling the volatilization kinetics of the water / ethanol / polyethylene glycol 400 ternary solvent system, a hierarchical porous structure with multi-scale pore size distribution can be spontaneously formed within the coating. This structure significantly enhances the coating's light scattering ability (reflectivity ≥88%) in the 0.25-2.5 μm solar spectrum range. This synergistic effect of high infrared emission and porous structure enhancing solar reflection enables the coating to achieve efficient passive radiative cooling without external energy input.

[0011] (3) This coating has excellent construction adaptability and wide application potential. It can be applied by conventional spraying combined with photocuring process to quickly form functional coatings on the surfaces of various substrates such as building envelopes, electronic device housings, and outdoor equipment. The photocuring process has extremely low energy consumption and can even be completed by relying on natural light. The curing speed is fast, which greatly improves construction efficiency. At the same time, the coating shows good adhesion and applicability to common substrates such as metal, glass, wood, and concrete.

[0012] (4) This coating features zero-energy operation, zero-pollution emissions, and no moving mechanical parts, demonstrating significant environmental benefits and application prospects in the fields of radiation cooling and energy-saving coatings. The system uses low-cost, non-toxic raw materials, meets the requirements of green manufacturing, and lays a solid technical and environmental foundation for its large-scale industrialization. Attached Figure Description

[0013] Figure 1 The present invention provides a flowchart and a schematic diagram of the preparation of a radiation-cooled coating with photocurable-driven phase separation.

[0014] Figure 2 SEM images of white coatings prepared from the photocurable phase-separated radiation-cooled coatings provided in Examples 1 and 5-7 of this invention.

[0015] Figure 3 The test results of solar reflectance spectrum (0.25-2.5μm) and infrared emission spectrum (8-13μm) for Examples 1 and 5-7 of the present invention are shown. Figure 4 Outdoor cooling performance comparison curves of Examples 1-4 provided by the present invention. Detailed Implementation

[0016] The present invention will be further described below with reference to specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise stated, the raw materials and reagents used in the embodiments of the present invention are conventionally purchased raw materials and reagents.

[0017] As one specific embodiment, the photocurable phase-separation-driven radiation cooling coating provided by the present invention achieves high-efficiency radiation cooling performance by precisely controlling the component ratio and phase separation behavior. Its composition is as follows: by weight, it includes the following components: 20-35 parts polymer monomer, 0.01-0.2 parts crosslinking agent, 0.01-0.2 parts photoinitiator and 65-80 parts mixed solvent.

[0018] Polymer monomer: Acrylamide monomer, as the main body of the hydrophilic polymer network, forms a three-dimensional skeleton through molecular chain cross-linking, endowing the coating with structural stability and intrinsic infrared emission characteristics (achieving thermal radiation in the 8-13μm band by utilizing the CH, NH bond vibration peaks). The polymer monomer can also be N-isopropylacrylamide or acrylic acid.

[0019] Crosslinking agent: N,N'-methylenebisacrylamide, which regulates the polymer network density through crosslinking reaction with acrylamide monomer, thereby optimizing the mechanical properties (such as hardness and flexibility) and pore structure stability of the coating.

[0020] Photoinitiator: 2-hydroxy-4-(2-hydroxyethoxy)-2-methylphenylacetone, which decomposes under 320-400nm ultraviolet light or natural sunlight to generate free radicals, initiating the polymerization of acrylamide monomers and achieving rapid curing of the coating.

[0021] The mixed solvent system is selected from one or more of water, ethanol, and polyethylene glycol 400, preferably composed of water, ethanol, and polyethylene glycol 400 in a mass ratio of 10-20:20-30:25-50. The three components work synergistically: water provides a hydrophilic environment, promoting the dissolution of acrylamide monomers; ethanol regulates the solvent evaporation rate and, as a volatile component, induces early phase separation; polyethylene glycol 400 provides a high-boiling-point, high-viscosity component, delaying solvent evaporation and forming an evaporation gradient with ethanol, balancing phase separation and polymerization rates, ultimately forming a micro-nano hierarchical porous structure (pore size 50nm-5μm, porosity 40-70%). By adjusting the mixed solvent ratio, the pore size distribution and porosity of the porous structure can be precisely controlled, thereby optimizing solar reflectance and infrared radiation performance.

[0022] As one specific implementation method, the preparation process of this coating is based on the mechanism of solution mixing and photocuring-induced phase separation, and the specific steps are as follows: (1) Preparation of mixed solvent system Add deionized water, ethanol, and polyethylene glycol 400 to a container according to the formula. Use a magnetic stirrer to stir at 200-300 rpm for 10-15 minutes at room temperature to ensure that the solvents are evenly mixed and form a transparent and homogeneous mixed solvent system.

[0023] (2) Preparation of prepolymer solution A Add the formulated amounts of acrylamide monomer and N,N'-methylenebisacrylamide to the above mixed solvent system, and stir magnetically at 200-300 r / min for 1-2 h at room temperature until the solid is completely dissolved and the solution is transparent and homogeneous, and label it "solution A".

[0024] (3) Formulation of UV-curable coatings Under light-protected conditions (such as brown bottles or containers wrapped in aluminum foil), add the prescribed amount of 2-hydroxy-4-(2-hydroxyethoxy)-2-methylphenylacetone to solution A, and continue stirring for 30-60 minutes until the photoinitiator is completely dissolved to obtain a photocurable radiation cooling coating that drives phase separation and can be used directly.

[0025] Key control points: Step (2) must ensure that the monomer and crosslinking agent are completely dissolved to avoid residual solids affecting the uniformity of the coating; Step (3) must be strictly operated in the dark to prevent the photoinitiator from decomposing prematurely and causing the coating to fail.

[0026] As one specific implementation method, this coating can form a functional coating on the substrate surface through a simple spraying and UV curing process. The specific implementation process is as follows: (1) Substrate pretreatment The substrate to be coated (such as metal, glass, wood, concrete, etc.) needs to be cleaned to remove oil, dust and loose attachments. If necessary, sandblasting or grinding should be performed to enhance the adhesion of the coating.

[0027] (2) Spraying process The coating is evenly sprayed onto the substrate surface using a spray gun with a nozzle diameter of 0.3-0.8 mm and a pressure of 0.2-0.5 MPa, controlling the wet film thickness to be 100-500 μm. Depending on the size and shape of the substrate, multiple sprays (with intervals of 5-10 minutes between each spray) can be used to achieve the target thickness.

[0028] (3) Photocuring process UV curing: Use a UV lamp with a wavelength of 320-400nm (power density 20-150mW / cm²). 2 Irradiate the coating for 60-180 seconds to ensure the curing energy density reaches 6-15 J / cm³. 2 This allows the coating to fully cross-link and cure.

[0029] Natural sunlight curing: On a sunny day, place the sprayed substrate in the sun for 10-30 minutes (the exact time depends on the light intensity) to initiate curing using the ultraviolet components in natural light.

[0030] Curing Mechanism: During the curing process, the photoinitiator initiates the polymerization of acrylamide to form a polymer network. Simultaneously, ethanol in the mixed solvent system rapidly evaporates, while polyethylene glycol 400 slowly diffuses. Through the synergistic effect of "polymerization-induced phase separation" and "solvent evaporation-induced phase separation," a micro-nano hierarchical porous structure is formed within the coating, ultimately resulting in a white porous coating. The coating preparation process and phase separation process are as follows: Figure 1 As shown.

[0031] As one specific implementation method, the cured white coating achieves efficient radiative cooling through the following mechanism: Solar reflection: The micro-nano porous structure produces multiple scattering and reflection of sunlight in the 0.25-2.5μm wavelength band, with a solar reflectivity ≥88%; Infrared radiation: The CH and NH bond vibrations of the acrylamide polymer network have a high emissivity (≥95%) in the 8-13 μm atmospheric window, which can transfer heat to outer space in the form of infrared radiation.

[0032] As one specific implementation, the application of photocurable phase-separated radiation-cooled coatings includes the following areas: Building: Coated on building exterior walls and roofs to reduce indoor temperature and air conditioning energy consumption; Electronic equipment: Coated on the surface of equipment such as servers, photovoltaic panels, and outdoor displays to improve operational stability through passive cooling; Outdoor equipment: Applied to tents, car bodies, outdoor furniture, etc., to reduce surface temperature and improve user comfort.

[0033] As a specific implementation method, the radiation-cooled coating with photocurable phase separation has the following advantages: Process compatibility: Can be directly sprayed onto various substrates such as metal, glass, wood, and concrete, with strong adhesion; Green and environmentally friendly: It uses non-toxic components (acrylamide, ethanol, etc.), has no VOC emissions, and has low energy consumption during the curing process (the energy consumption of light curing is only 1 / 10 of that of heat curing). Cost-effectiveness: Raw material costs are low, preparation and construction processes are simple, and it is suitable for large-scale industrial applications.

[0034] Synergistic Phase Separation Control: Through synergistic phase separation of photopolymerization and mixed solvent evaporation, micro-nano hierarchical porous structures can be constructed without templates, simplifying the process and reducing costs; High efficiency of light curing: UV or natural light curing can be completed in seconds to tens of minutes, which is much more efficient than traditional thermal curing (which takes several hours). Performance-cost balance: High reflectivity is achieved through structural design rather than adding high-reflectivity fillers (such as TiO2) using low-cost acrylamide as the base material, balancing performance and economy; Universality and environmental friendliness: Applicable to a variety of substrates, operates without energy consumption, and emits zero pollution, in line with the trend of green and energy-saving development.

[0035] Through the above embodiments, the present invention provides a radiation cooling coating with simplified components, simple process, low cost and excellent performance. It is polymerized and cured by ultraviolet light and the gradient evaporation characteristics of the mixed solvent are used to induce the formation of micro-nano hierarchical porous structure, thereby achieving synergistic enhancement of solar reflectivity and infrared emissivity, achieving a highly efficient passive cooling effect, and laying the foundation for the large-scale application of passive cooling technology.

[0036] This invention employs a photocuring-phase separation coupling process, which allows for precise control of the coating's pore structure without the need for complex equipment. It boasts advantages such as simple process, environmental friendliness (no VOC residue, low energy consumption curing), and wide applicability (can be sprayed / brushed onto buildings, electronic devices, and outdoor equipment). It overcomes the limitations of traditional materials that rely on precision machining or multi-layer composites, and is suitable for large-scale coating applications in building energy conservation, electronic thermal management, and outdoor equipment.

[0037] The present invention will be further described below with reference to specific embodiments.

[0038] Example 1 A method for preparing a radiation-cooled coating with a porous structure by photocuring-driven phase separation includes the following steps: (1) Preparation of mixed solvent system Add 15g of deionized water, 23g of ethanol, and 32g of polyethylene glycol 400 to a container. Use a magnetic stirrer to stir at 300r / min for 10min at room temperature to ensure that the solvents are evenly mixed and form a transparent and homogeneous mixed solvent system.

[0039] (2) Preparation of prepolymer solution A Add 30g of acrylamide monomer and 0.036g of N,N'-methylenebisacrylamide to the above mixed solvent system, and stir magnetically at 300r / min for 1h at room temperature until the solid is completely dissolved and the solution is transparent and homogeneous, and label it "solution A".

[0040] (3) Formulation of UV-curable coatings Under light-protected conditions (such as brown bottles or containers wrapped in aluminum foil), add 0.036 g of 2-hydroxy-4-(2-hydroxyethoxy)-2-methylphenylacetone to solution A, and continue stirring for 30 min until the photoinitiator is completely dissolved to obtain a photocurable, phase-separated radiation cooling coating that can be used directly.

[0041] (4) Substrate pretreatment The Al substrate is cleaned to remove oil, dust and loose deposits, and then polished to enhance coating adhesion.

[0042] (5) Spraying process A spray gun with a nozzle diameter of 0.8 mm was used to uniformly spray the radiation cooling coating onto the surface of the Al substrate under a pressure of 0.4 MPa. The coating thickness was controlled to be 500 μm by spraying three times.

[0043] (6) Photocuring process UV curing: Use a 350nm UV lamp (power density 100mW / cm²). 2 Irradiate the coating for 150 seconds to ensure the curing energy density reaches 10 J / cm³. 2 This allows the coating to fully cross-link and cure.

[0044] The test results of the solar reflectance spectrum (0.25-2.5μm) and infrared emission spectrum (8-13μm) of Example 1 are as follows: Figure 3 As shown, the outdoor cooling performance comparison curves of Example 1 are as follows: Figure 4 As shown, the SEM image of the coating in Example 1 is as follows. Figure 2 As shown.

[0045] Example 2 A method for preparing a radiation-cooled coating with a porous structure by photocuring-driven phase separation includes the following steps: (1) Preparation of mixed solvent system Add 10g of deionized water, 30g of ethanol, and 50g of polyethylene glycol 400 to a container. Use a magnetic stirrer to stir at 300 rpm for 10 minutes at room temperature to ensure that the solvents are evenly mixed and form a transparent and homogeneous mixed solvent system.

[0046] (2) Preparation of prepolymer solution A Add 35g of acrylamide monomer and 0.2g of N,N'-methylenebisacrylamide to the above mixed solvent system, and stir magnetically at 300r / min for 1h at room temperature until the solid is completely dissolved and the solution is transparent and homogeneous, and label it "solution A".

[0047] (3) Formulation of UV-curable coatings Under light-protected conditions (such as brown bottles or containers wrapped in aluminum foil), add 0.2 g of 2-hydroxy-4-(2-hydroxyethoxy)-2-methylphenylacetone to solution A, and continue stirring for 30 min until the photoinitiator is completely dissolved to obtain a photocurable, phase-separated radiation cooling coating that can be used directly.

[0048] (4) Substrate pretreatment The glass substrate is cleaned to remove oil, dust and loose deposits, and then polished to enhance coating adhesion.

[0049] (5) Spraying process A radiative cooling coating was uniformly sprayed onto the surface of a glass substrate using a spray gun with a nozzle diameter of 0.5 mm and a pressure of 0.5 MPa. The coating thickness was controlled to be 500 μm through three spraying processes.

[0050] (6) Photocuring process UV curing: Use a 400nm UV lamp (power density 150mW / cm²). 2 Irradiate the coating for 180 seconds to ensure the curing energy density reaches 15 J / cm³. 2 This allows the coating to fully cross-link and cure.

[0051] The outdoor cooling performance comparison curves of Example 2 are as follows: Figure 4 As shown.

[0052] Example 3 A method for preparing a radiation-cooled coating with a porous structure by photocuring-driven phase separation includes the following steps: (1) Preparation of mixed solvent system Add 20g of deionized water, 20g of ethanol, and 25g of polyethylene glycol 400 to a container. Use a magnetic stirrer to stir at 300 rpm for 10 minutes at room temperature to ensure that the solvents are evenly mixed and form a transparent and homogeneous mixed solvent system.

[0053] (2) Preparation of prepolymer solution A Add 20g of N-isopropylacrylamide and 0.01g of N,N'-methylenebisacrylamide to the above mixed solvent system, and stir magnetically at 300r / min for 1h at room temperature until the solid is completely dissolved and the solution is transparent and homogeneous, and label it "solution A".

[0054] (3) Formulation of UV-curable coatings Under light-protected conditions (such as brown bottles or containers wrapped in aluminum foil), add 0.01 g of 2-hydroxy-4-(2-hydroxyethoxy)-2-methylphenylacetone to solution A, and continue stirring for 30 min until the photoinitiator is completely dissolved to obtain a photocurable radiation-cooling coating that drives phase separation and can be used directly.

[0055] (4) Substrate pretreatment The wooden substrate is cleaned to remove oil, dust and loose deposits, and then sanded to enhance coating adhesion.

[0056] (5) Spraying process A spray gun with a nozzle diameter of 0.3 mm was used to uniformly spray the radiation cooling coating onto the surface of the wood substrate under a pressure of 0.2 MPa. The coating thickness was controlled to be 500 μm by spraying three times.

[0057] (6) Photocuring process UV curing: Use a 320nm UV lamp (power density 20mW / cm²). 2 Irradiate the coating for 60 seconds to ensure the curing energy density reaches 6 J / cm³. 2 This allows the coating to fully cross-link and cure.

[0058] The outdoor cooling performance comparison curves of Example 3 are as follows: Figure 4 As shown.

[0059] Example 4 A method for preparing a radiation-cooled coating with a porous structure by photocuring-driven phase separation includes the following steps: (1) Preparation of mixed solvent system Add 15g of deionized water, 23g of ethanol, and 32g of polyethylene glycol 400 to a container. Use a magnetic stirrer to stir at 300r / min for 10min at room temperature to ensure that the solvents are evenly mixed and form a transparent and homogeneous mixed solvent system.

[0060] (2) Preparation of prepolymer solution A Add 30g of acrylic acid and 0.036g of N,N'-methylenebisacrylamide to the above mixed solvent system, and stir magnetically at 300r / min for 1h at room temperature until the solid is completely dissolved and the solution is transparent and homogeneous, and label it "solution A".

[0061] (3) Formulation of UV-curable coatings Under light-protected conditions (such as brown bottles or containers wrapped in aluminum foil), add 0.036 g of 2-hydroxy-4-(2-hydroxyethoxy)-2-methylphenylacetone to solution A, and continue stirring for 30 min until the photoinitiator is completely dissolved to obtain a photocurable, phase-separated radiation cooling coating that can be used directly.

[0062] (4) Substrate pretreatment The concrete substrate is cleaned to remove oil, dust and loose deposits, and then sanded to enhance coating adhesion.

[0063] (5) Spraying process A spray gun with a nozzle diameter of 0.8 mm was used to uniformly spray the radiation cooling coating onto the surface of the concrete substrate under a pressure of 0.4 MPa. The coating thickness was controlled to be 500 μm by spraying three times.

[0064] (6) Photocuring process UV curing: Use a UV lamp with a wavelength of 320-400nm (power density 20-150mW / cm²). 2 Irradiate the coating for 60-180 seconds to ensure the curing energy density reaches 6-15 J / cm³. 2 This allows the coating to fully cross-link and cure.

[0065] The outdoor cooling performance comparison curve of Example 4 is shown below. Figure 4 As shown.

[0066] Example 5 A method for preparing a radiation-cooled coating with a porous structure by photocuring-driven phase separation includes the following steps: (1) Preparation of mixed solvent system Add 15g of deionized water and 55g of polyethylene glycol 400 to a container, and stir with a magnetic stirrer at 300r / min for 10min at room temperature to ensure uniform mixing of the solvents and form a transparent and homogeneous mixed solvent system.

[0067] (2) Preparation of prepolymer solution A Add 30g of acrylamide monomer and 0.036g of N,N'-methylenebisacrylamide to the above mixed solvent system, and stir magnetically at 300r / min for 1h at room temperature until the solid is completely dissolved and the solution is transparent and homogeneous, and label it "solution A".

[0068] (3) Formulation of UV-curable coatings Under light-protected conditions (such as brown bottles or containers wrapped in aluminum foil), add 0.036 g of 2-hydroxy-4-(2-hydroxyethoxy)-2-methylphenylacetone to solution A, and continue stirring for 30 min until the photoinitiator is completely dissolved to obtain a photocurable, phase-separated radiation cooling coating that can be used directly.

[0069] (4) Substrate pretreatment The Al substrate is cleaned to remove oil, dust and loose deposits, and then polished to enhance coating adhesion.

[0070] (5) Spraying process A spray gun with a nozzle diameter of 0.8 mm was used to uniformly spray the radiation cooling coating onto the surface of the Al substrate under a pressure of 0.4 MPa. The coating thickness was controlled to be 500 μm by spraying three times.

[0071] (6) Photocuring process UV curing: Use a 350nm UV lamp (power density 100mW / cm²). 2 Irradiate the coating for 150 seconds to ensure the curing energy density reaches 10 J / cm³. 2 This allows the coating to fully cross-link and cure.

[0072] Example 6 A method for preparing a radiation-cooled coating with a porous structure by photocuring-driven phase separation includes the following steps: (1) Preparation of mixed solvent system Add 15g of deionized water and 55g of ethanol to a container, and stir with a magnetic stirrer at 300r / min for 10min at room temperature to ensure uniform mixing of the solvents and form a transparent and homogeneous mixed solvent system.

[0073] (2) Preparation of prepolymer solution A Add 30g of acrylamide monomer and 0.036g of N,N'-methylenebisacrylamide to the above mixed solvent system, and stir magnetically at 300r / min for 1h at room temperature until the solid is completely dissolved and the solution is transparent and homogeneous, and label it "solution A".

[0074] (3) Formulation of UV-curable coatings Under light-protected conditions (such as brown bottles or containers wrapped in aluminum foil), add 0.036 g of 2-hydroxy-4-(2-hydroxyethoxy)-2-methylphenylacetone to solution A, and continue stirring for 30 min until the photoinitiator is completely dissolved to obtain a photocurable, phase-separated radiation cooling coating that can be used directly.

[0075] (4) Substrate pretreatment The Al substrate is cleaned to remove oil, dust and loose deposits, and then polished to enhance coating adhesion.

[0076] (5) Spraying process A spray gun with a nozzle diameter of 0.8 mm was used to uniformly spray the radiation cooling coating onto the surface of the Al substrate under a pressure of 0.4 MPa. The coating thickness was controlled to be 500 μm by spraying three times.

[0077] (6) Photocuring process UV curing: Use a 350nm UV lamp (power density 100mW / cm²). 2 Irradiate the coating for 150 seconds to ensure the curing energy density reaches 10 J / cm³. 2 This allows the coating to fully cross-link and cure.

[0078] Example 7 A method for preparing a radiation-cooled coating with a porous structure by photocuring-driven phase separation includes the following steps: (1) Preparation of prepolymer solution A Add 30g of acrylamide monomer and 0.036g of N,N'-methylenebisacrylamide to 70g of deionized water. Stir magnetically at 300r / min for 1h at room temperature until the solid is completely dissolved and the solution is transparent and homogeneous. Label this solution as "Solution A".

[0079] (2) Formulation of UV-curable coatings Under light-protected conditions (such as brown bottles or containers wrapped in aluminum foil), add 0.036 g of 2-hydroxy-4-(2-hydroxyethoxy)-2-methylphenylacetone to solution A, and continue stirring for 30 min until the photoinitiator is completely dissolved to obtain a photocurable, phase-separated radiation cooling coating that can be used directly.

[0080] (3) Substrate pretreatment The Al substrate is cleaned to remove oil, dust and loose deposits, and then polished to enhance coating adhesion.

[0081] (4) Spraying process A spray gun with a nozzle diameter of 0.8 mm was used to uniformly spray the radiation cooling coating onto the surface of the Al substrate under a pressure of 0.4 MPa. The coating thickness was controlled to be 500 μm by spraying three times.

[0082] (5) Photocuring process UV curing: Use a 350nm UV lamp (power density 100mW / cm²). 2 Irradiate the coating for 150 seconds to ensure the curing energy density reaches 10 J / cm³.2 This allows the coating to fully cross-link and cure.

[0083] Reference Figure 2 According to the SEM images (voltage 3kV, Mag 1KX) of Examples 1 and 5-7, it can be seen that the pores formed by using water as a solvent are not easy to observe. Using water + ethanol as a solvent can form pores that are easy to observe, but the porosity is low and the pore size is not uniform. Using water + polyethylene glycol 400 as a solvent can improve the porosity, but the pore size is not uniform. Using a specific mixed solvent system of water + ethanol + polyethylene glycol 400 can form a porous structure with uniform pore size and high porosity.

[0084] Reference Figure 3 According to the solar reflectance spectrum (0.25-2.5μm) and infrared emission spectrum (8-13μm) test results of Examples 1 and Examples 5-7, it can be seen that using a specific mixed solvent system of deionized water, ethanol and polyethylene glycol 400 can improve the solar reflectance and infrared emissivity of the coating.

[0085] Reference Figure 4 According to the outdoor cooling performance test results of Examples 1-4, the coatings used in Examples 1-4 can reduce the surface temperature of the substrate and have a good radiative cooling effect.

[0086] The foregoing has described in detail representative embodiments and comparative examples of the present invention. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without inventive effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A radiation-cooling coating that undergoes photocuring-driven phase separation, characterized in that, By weight, it comprises the following components: 20-35 parts polymer monomer, 0.01-0.2 parts crosslinking agent, 0.01-0.2 parts photoinitiator and 65-80 parts mixed solvent; The polymer monomer is selected from one or more of acrylamide monomer, N-isopropylacrylamide, and acrylic acid; The mixed solvent is selected from one or more of water, ethanol and polyethylene glycol 400.

2. The radiation-cooled coating with photocurable phase separation as described in claim 1, characterized in that, The mixed solvent consists of water, ethanol and polyethylene glycol 400.

3. The radiation-cooling coating with photocurable driven phase separation according to claim 2, characterized in that, The mass ratio of water, ethanol and polyethylene glycol 400 is 10-20:20-30:25-50.

4. The radiation-cooling coating with photocurable phase separation as described in claim 1, characterized in that, The crosslinking agent includes N,N'-methylenebisacrylamide.

5. The radiation-cooled coating with photocurable phase separation as described in claim 1, characterized in that, The photoinitiator includes 2-hydroxy-4-(2-hydroxyethoxy)-2-methylphenylacetone.

6. The method for preparing a radiation-cooled coating with photocurable driven phase separation according to any one of claims 1-5, characterized in that, Includes the following steps: (1) Disperse the polymer monomer and crosslinking agent in a mixed solvent to obtain solution A; (2) Under light-protected conditions, a photoinitiator was added to solution A and stirred to obtain a radiation-cooled coating that drives phase separation through photocuring.

7. The application of the photocurable phase-separated radiation-cooled coating according to any one of claims 1-5 in the preparation of coatings containing porous structures.

8. The application according to claim 7, characterized in that, A radiation-cooling coating with a photocurable phase separation is sprayed onto a substrate and then photocured to form a white coating with radiation-cooling function.

9. The application according to claim 8, characterized in that, The spraying process involves using a spray gun with a nozzle diameter of 0.3-0.8 mm and a pressure of 0.2-0.5 MPa to spray, resulting in a wet film thickness of 100-500 μm.

10. The application according to claim 8, characterized in that, The white coating has a micro-nano hierarchical porous structure with a pore size of 50 nm-5 μm and a porosity of 40-70%.

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