A multilayer radiative cooling film with a quasi-leaf structure and a method of making the same

Abstract

The present application relates to the technical field of polymer processing forming, in particular to a multilayer radiative cooling film with leaf-like structure and a preparation method thereof. The multilayer radiative cooling film with leaf-like structure takes ultrahigh molecular weight polyolefin as a substrate, and comprises a protective layer and a cooling layer. The protective layer comprises a protective base layer and protective layer inorganic particles for reflecting ultraviolet light. The protective base layer is arranged to imitate the plasmodesmatal structure of leaf epidermal cells. The protective layer inorganic particles are densely filled in the protective base layer to imitate the distribution of flavonoids in leaf epidermal cells, so as to resist ultraviolet radiation and block external pollutants. The cooling layer comprises a cooling base layer and cooling layer inorganic particles for reflecting sunlight. The cooling layer inorganic particles are filled in the cooling base layer to improve the radiative cooling performance. The preparation method of the multilayer radiative cooling film with leaf-like structure is used to prepare the multilayer radiative cooling film with leaf-like structure as described above.

Description

Technical Field

[0001] This invention relates to the field of polymer processing and molding technology, specifically to a multilayer radiative cooling film with a blade-like structure and its preparation method. Background Technology

[0002] With the intensification of global climate change and the continued development of the economy, the demand for refrigeration solutions in fields such as car cover refrigeration, equipment refrigeration, and building refrigeration is constantly growing. However, traditional refrigeration technologies such as air conditioning are gradually failing to meet the needs of modern society due to their high energy consumption, significant environmental impact, and limited application scenarios. To address these issues, Passive Radiative Cooling (PRC) technology, as a cutting-edge green refrigeration method, is receiving increasing attention.

[0003] PRC technology leverages the high transparency of the Earth's atmosphere in the mid-infrared (MIR) band (atmospheric window, λ=8µm~13µm) to infrared radiation, designing surface materials that enhance MIR radiation. This technology allows heat generated by an object to be directly dissipated into outer space as MIR radiation, thus achieving a cooling effect. Furthermore, the PRC film possesses high solar reflectivity, effectively blocking direct sunlight during the day and providing all-weather passive cooling performance.

[0004] In recent years, research on PRC technology has focused primarily on various structural types, including multilayer photonic structures, random media, metamaterials, aerogels, hydrogels, and porous polymers. These materials, due to their unique optical properties, have shown promising applications in photovoltaics, building insulation, food preservation, and electronic heat dissipation, achieving significant cooling effects. However, most existing PRC structures rely on complex and costly manufacturing processes, making large-scale industrial production extremely difficult. Furthermore, existing PRC materials struggle to simultaneously meet high standards in mechanical strength, elongation at break, and toughness, especially in ensuring good ultraviolet (UV) durability and long-term stability. Therefore, developing a simple, cost-effective PRC membrane with a long service life and superior performance has become a critical issue that urgently needs to be addressed. Summary of the Invention

[0005] The purpose of this invention is to overcome the defects and shortcomings of the prior art and provide a multilayer radiative cooling film with a blade-like structure. This multilayer radiative cooling film achieves better radiative cooling effect and higher UV stability by optimizing material composition and structural design, thus providing new possibilities for the practical application of PRC technology.

[0006] Another objective of this invention is to provide a method for preparing a multilayer radiative cooling film with a blade-like structure. This method enables large-scale, efficient, and continuous production of multilayer blade-like porous films based on inexpensive raw materials, resulting in high production efficiency and low production costs.

[0007] The objective of this invention can be achieved through the following technical solutions: A multilayer radiative cooling film with a leaf-like structure, the multilayer radiative cooling film using ultra-high molecular weight polyolefin as a substrate, includes a protective layer and a cooling layer; the protective layer includes a protective base layer and protective layer inorganic particles for reflecting ultraviolet light, the protective base layer is configured to mimic the plasmodesmata structure of leaf epidermal cells, and the protective layer inorganic particles are densely packed within the protective base layer to mimic the distribution of flavonoids in leaf epidermal cells, in order to resist ultraviolet radiation and block external pollutants; the cooling layer includes a cooling base layer and cooling layer inorganic particles for reflecting sunlight, at least two types of cooling layer inorganic particles are packed within the cooling base layer to improve radiative cooling performance.

[0008] As a preferred embodiment, the protective base layer includes multiple micropores and connecting wires, with inorganic particles of the protective layer disposed within the micropores, and multiple connecting wires attached to the outer wall of the inorganic particles of the protective layer.

[0009] As a preferred embodiment, the multilayer radiative cooling film has a two-layer or three-layer structure; when the multilayer radiative cooling film has a three-layer structure, two protective layers are respectively disposed on both sides of the cooling layer, with the protective layer thickness accounting for 10%~25% and the cooling layer thickness accounting for 50%~80%; when the multilayer radiative cooling film has a two-layer structure, one protective layer is disposed on one side of the cooling layer, with the protective layer thickness accounting for 10%~50% and the cooling layer thickness accounting for 50%~90%.

[0010] As a preferred embodiment, the ultra-high molecular weight polyolefin material used as the substrate of the multilayer radiative cooling film includes one or more of ultra-high molecular weight polyethylene, ultra-high molecular weight polypropylene, ultra-high molecular weight polybutene-1, and ultra-high molecular weight polyoctene-1.

[0011] As a preferred embodiment, the particle size range of the inorganic particles in the protective layer is 0.5 μm to 20 μm, and the materials used to prepare the inorganic particles in the protective layer include one or more of silicon dioxide, barium sulfate, calcium fluoride, and aluminum oxide.

[0012] As a preferred embodiment, in the protective layer, the solid content of the inorganic particles in the protective layer is 10% to 80%, and the solid content of the ultra-high molecular weight polyolefin is 20% to 90%.

[0013] As a preferred embodiment, the particle size range of the inorganic particles in the cooling layer is 0.1 μm to 20 μm, and the materials used to prepare the inorganic particles in the cooling layer include two or more of titanium dioxide, zinc oxide, calcium fluoride, and silicon dioxide.

[0014] As a preferred option, the solid content of inorganic particles in the cooling layer is 10% to 80%, and the solid content ratio of inorganic particles in the cooling layer of different materials can vary in the range of 1:9 to 9:1, while the solid content ratio of ultra-high molecular weight polyolefin is 20% to 90%.

[0015] A method for preparing a multilayer radiative cooling film with a blade-like structure, comprising the following steps: S1. Initial Mixing: According to the solid content requirements of the protective layer, inorganic particles, ultra-high molecular weight polyolefin and pore-forming agent are mixed to prepare the initial mixture of the protective layer; according to the solid content requirements of the cooling layer, inorganic particles, ultra-high molecular weight polyolefin and pore-forming agent are mixed to prepare the initial mixture of the cooling layer. S2, Co-extrusion: The protective layer initial mixture and the cooling layer initial mixture prepared in step S1 are placed in a multi-layer co-extrusion equipment with a temperature 40℃~70℃ higher than the melting temperature. Through the co-extrusion process, an ultra-high molecular weight polyolefin network structure containing uniformly distributed inorganic particles is formed to obtain a multi-layer gel film. S3. Removal of pore-forming agents: The multilayer gel membrane is placed in the extractant for extraction and dried to remove the pore-forming agents. The interior of the multilayer gel membrane is formed by the entanglement of ultra-high molecular weight polyolefin molecular chains, which forms a uniformly distributed microporous structure, similar to the intercellular plasmodesmata structure between leaf epidermal cells. Finally, a multilayer radiation cooling membrane with a leaf-like structure is obtained. The thickness of the multilayer radiation cooling film is 10 μm to 10 mm, and the average diameter of the uniformly distributed micropores is 0.01 μm to 1 μm.

[0016] As a preferred embodiment, the pore-forming agent is one or more of polyvinylpyrrolidone, polyethylene glycol, polyvinyl alcohol, mineral oil, petrolatum, vegetable oil, and decahydronaphthalene.

[0017] The working principle of the multilayer radiative cooling film with a blade-like structure of the present invention: This multi-layered radiation cooling film is inspired by the porous structure of plasmodesmata in plant leaf epidermis. The tightly packed epidermal cells form an effective barrier against ultraviolet radiation. It is further enhanced by flavonoids widely embedded in the leaf epidermal cells. Flavonoids possess antioxidant capabilities, protecting key components such as the cell nucleus, cell membrane, and chloroplasts from UV damage. The multi-layered radiation cooling film uses ultra-high molecular weight polyolefin as a substrate and consists of two main layers: a protective layer and a cooling layer. The protective layer is densely filled with inorganic particles (such as silica) with high UV reflectivity, while the cooling layer is doped with various inorganic particles (such as titanium dioxide and silica) possessing high optical properties.

[0018] Protective Layer: A plasmodesmata structure, similar to those found in leaf epidermal cells, is formed using ultra-high molecular weight polyolefin (UHMWPE) as the base material. Highly reflective inorganic particles are tightly packed within this plasmodesmata structure. For example, UHMWPE can be used as the material for the protective base layer, and silica as the material for the inorganic particles. Silica exhibits excellent reflectivity in the ultraviolet wavelength range, allowing a significant portion of ultraviolet radiation to be attenuated upon passing through it. Furthermore, silica demonstrates outstanding chemical stability under ultraviolet radiation, ensuring good weather resistance of the protective layer under UV irradiation. Therefore, silica is embedded in the plasmodesmata structure formed by UHMWPE in a flavonoid-like form to resist ultraviolet radiation and prevent photocatalytic reactions initiated by certain inorganic particles in the cooling layer.

[0019] Cooling Layer: At least two types of inorganic cooling particles are doped into the cooling base layer made of ultra-high molecular weight polyolefin. The inorganic cooling particles of different materials and particle sizes work synergistically. For example, ultra-high molecular weight polyethylene is used as the material for the cooling base layer, while titanium dioxide and silicon dioxide are used as the materials for the inorganic cooling particles. Silicon dioxide compensates for the decrease in solar reflectivity caused by the high absorbance of titanium dioxide in the ultraviolet wavelength range. Simultaneously, titanium dioxide has a large extinction coefficient and high MIR emissivity, which can compensate for the decrease in MIR emissivity caused by the significant decrease in the extinction coefficient of silicon dioxide in the 10μm~12μm wavelength range. Therefore, titanium dioxide also acts as an emissive material, effectively complementing silicon dioxide to achieve high-efficiency, long-lasting passive cooling.

[0020] Compared with the prior art, the present invention has the following advantages and beneficial effects: (1) Significantly improves radiation cooling performance: Through the synergistic effect of inorganic particles in the protective layer and cooling layer, a significant solar reflectivity of over 96% and a mid-infrared (MIR) emissivity of over 94% are achieved. Experimental data show that the multilayer radiation cooling film with a blade-like structure of the present invention can reduce the ambient temperature by up to 10.2℃, providing strong support for the practical application of passive radiation cooling (PRC) technology.

[0021] (2) Excellent UV stability and outdoor durability: The multi-layered blade-like structure has a biomimetic intercellular filament structure formed by the entanglement of ultra-high molecular weight polyolefin molecular chains, and is filled with inorganic particles with high UV reflectivity. This not only improves the material's ability to resist ultraviolet rays, but also ensures that the radiation cooling film can maintain the stability of its mechanical and optical properties even under high-intensity ultraviolet radiation of 7000MJ / m², making it very suitable for long-term outdoor use.

[0022] (3) Structural design optimization: By rationally designing the ratio and thickness of the protective layer and the cooling layer, and by precisely controlling the solid content and particle size distribution of inorganic particles in each layer, the radiation cooling effect is further enhanced.

[0023] (4) Feasibility of large-scale production: The large-scale manufacturing of this multi-layer pseudo-blade porous structure membrane can be achieved by using commercially available multi-layer co-extrusion equipment, which reduces production costs and technical barriers and is conducive to the widespread promotion and application of PRC technology.

[0024] (5) Economic sustainability: The raw materials used are widely available and inexpensive, including a variety of ultra-high molecular weight polyolefin base materials (such as ultra-high molecular weight polyethylene, ultra-high molecular weight polypropylene, etc.) and inorganic particles for protective layer and inorganic particles for cooling layer (such as silicon dioxide, titanium dioxide, etc.), which not only ensures the high performance of the product, but also meets the needs of economic sustainable development.

[0025] (6) Easy to process and manufacture: The preparation method is simple and easy to implement. From initial mixing to co-extrusion and then to pore-forming agent removal, each step is clear and specific, ensuring the uniformity and consistency of the final product. In addition, a variety of pore-forming agents can be used, and the most suitable one or several combinations can be selected according to actual needs, which increases the flexibility of the process. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of a two-layer multilayer radiative cooling film with a blade-like structure. Figure 2 This is a schematic diagram of the cross-section of a two-layer multilayer radiative cooling film with a blade-like structure. Figure 3 This is a schematic diagram of the SEM cross-section of the protective substrate of a two-layer multilayer radiative cooling film with a blade-like structure. Figure 4 This is a schematic SEM cross-section of the cooling substrate of a two-layer multilayer radiative cooling film with a blade-like structure. Figure 5 This is a schematic diagram of a three-layer multilayer radiative cooling film with a blade-like structure. Figure 6 The solar reflectance and MIR emissivity spectra of the two-layer multilayer radiative cooling film with a blade-like structure prepared in Example 1 are shown. Figure 7 This is a diagram showing the cooling effect of the two-layer multilayer radiative cooling film with a blade-like structure prepared in Example 1; Figure 8 This is a graph showing the mechanical properties of the two-layer multilayer radiation cooling film with a blade-like structure prepared in Example 1 under ultraviolet light irradiation. Figure 9 The solar reflectance and MIR emissivity spectra of the two-layer multilayer radiative cooling film with a pseudo-blade structure prepared in Example 2 are shown. Figure 10 This is a diagram showing the cooling effect of the two-layer multilayer radiative cooling film with a blade-like structure prepared in Example 2; Figure 11 This is a graph showing the mechanical properties of the two-layer multilayer radiation cooling film with a blade-like structure prepared in Example 2 under ultraviolet light irradiation. Figure 12 The solar reflectance and MIR emissivity spectra of the monolayer radiative cooling film with inorganic particle synergistic effect prepared in Comparative Example 1 are shown. Figure 13 The graph shows the mechanical properties of the monolayer radiation cooling film with inorganic particle synergistic effect prepared in Comparative Example 1 under ultraviolet light irradiation. Figure 14 These are tests of solar reflectance, infrared emissivity, and weather resistance for each embodiment and comparative example; The layers are: 1. Protective base layer; 2. Cooling base layer; 3. Protective layer inorganic particles; 4. Cooling layer inorganic particles; 5. First protective layer; 6. Cooling layer; 7. Second protective layer. Detailed Implementation

[0027] Example 1 A multilayer radiative cooling film with a leaf-like structure, the multilayer radiative cooling film using ultra-high molecular weight polyolefin as a substrate, includes a protective layer and a cooling layer; the protective layer includes a protective base layer and protective layer inorganic particles for reflecting ultraviolet light, the protective base layer is configured to mimic the plasmodesmata structure of leaf epidermal cells, and the protective layer inorganic particles are densely packed within the protective base layer to mimic the distribution of flavonoids in leaf epidermal cells, in order to resist ultraviolet radiation and block external pollutants; the cooling layer includes a cooling base layer and cooling layer inorganic particles for reflecting sunlight, at least two types of cooling layer inorganic particles are packed within the cooling base layer to improve radiative cooling performance.

[0028] like Figure 1 and Figure 2 As shown, the multilayer radiative cooling film has a two-layer structure, with a protective layer disposed on one side of the cooling layer. The protective layer accounts for 50% of the total thickness, and the cooling layer accounts for 50% of the total thickness. Figure 3 As shown, the protective layer includes inorganic particles with high ultraviolet reflectivity, a protective base layer, and micropores. The protective base layer includes multiple micropores and connecting filaments. The inorganic particles are disposed within the micropores, and multiple connecting filaments are attached to the outer walls of the inorganic particles. The inorganic particles located in different micropores are connected by the connecting filaments, forming the intercellular plasmodesmata structure of the protective base layer. The synergistic effect of the intercellular plasmodesmata structure of the protective base layer and the high ultraviolet reflectivity of the inorganic particles ensures its ultraviolet stability. Figure 4 As shown, the cooling layer includes two types of inorganic particles with high optical performance, a cooling base layer, and micropores. It can enhance the radiation cooling performance of the multilayer radiation cooling film by utilizing the synergistic effect between the inorganic particles of the two different materials and different particle sizes.

[0029] like Figure 5 As shown, in addition to the two-layer structure mentioned above, the multilayer radiation cooling film can also be configured as a three-layer structure. Specifically, the multilayer radiation cooling film includes a first protective layer, a cooling layer, and a second protective layer arranged sequentially, with the two protective layers respectively disposed on both sides of the cooling layer. The first and second protective layers include inorganic particles with high ultraviolet light reflectivity, a protective base layer, and micropores. The synergistic effect of the intercellular plasmodesmata structure of the protective base layer and the high ultraviolet light reflectivity of the inorganic particles in the protective layer ensures its ultraviolet stability. The cooling layer includes inorganic particles with high optical performance, a cooling base layer, and micropores, which can enhance the radiation cooling performance of the multilayer radiation cooling film by utilizing the synergistic effect between two different materials and different particle sizes of inorganic particles in the cooling layer.

[0030] A method for preparing a multilayer radiative cooling film with a blade-like structure is specifically carried out according to the following steps: A method for preparing a multilayer radiative cooling film with a blade-like structure, comprising the following steps: S1. Initial Mixing: According to the solid content requirements of the protective layer, inorganic particles, ultra-high molecular weight polyolefin and pore-forming agent are mixed to prepare the initial mixture of the protective layer; according to the solid content requirements of the cooling layer, inorganic particles, ultra-high molecular weight polyolefin and pore-forming agent are mixed to prepare the initial mixture of the cooling layer. S2, Co-extrusion: The protective layer initial mixture and the cooling layer initial mixture prepared in step S1 are placed in a multi-layer co-extrusion device with a temperature 60°C higher than the melting temperature. Through the co-extrusion process, an ultra-high molecular weight polyolefin network structure containing uniformly distributed inorganic particles is formed to obtain a multi-layer gel film.

[0031] S3. Removal of pore-forming agents: The multilayer gel membrane is placed in the extractant for extraction and dried to remove the pore-forming agents. The interior of the multilayer gel membrane is formed by the entanglement of ultra-high molecular weight polyolefin molecular chains, which forms a uniformly distributed microporous structure, similar to the intercellular plasmodesmata structure between leaf epidermal cells. Finally, a multilayer radiation cooling membrane with a leaf-like structure is obtained. In this embodiment, the thickness of the multilayer radiation cooling film is 500 μm, and the average diameter of the uniformly distributed micropores is 0.65 μm; the inorganic particles of the protective layer in step S1 are barium sulfate with a particle size of 1 μm and a solid content of 40%; the inorganic particles of the cooling layer are barium sulfate with a particle size of 1 μm and zinc oxide with a particle size of 0.1 μm, with a solid content of 40%, and the solid content ratio of barium sulfate to zinc oxide is 1:4; the ultra-high molecular weight polyolefin is ultra-high molecular weight polypropylene.

[0032] Figure 6 The solar reflectance and MIR emissivity spectra of the two-layer multilayer radiative cooling film with a pseudo-blade structure prepared in Example 1 are shown. Figure 6 It can be seen that the multilayer radiative cooling film achieves a significant solar reflectivity of over 96% and a MIR emissivity of over 95%, which meets the spectral requirements of daytime radiative cooling materials.

[0033] Figure 7 This is a diagram illustrating the cooling effect of the two-layer, multi-layered radiative cooling film with a blade-like structure prepared in Example 1. (The diagram is presented in the original text.) Figure 7 It can be seen that the multi-layer radiative cooling film can reduce the temperature by 8.9°C during the day, and has a good radiative cooling effect.

[0034] Figure 8 This is a graph showing the mechanical properties of a two-layer, blade-like multilayer radiative cooling film prepared in Example 1 under ultraviolet light irradiation. Figure 8 It can be seen that the multilayer radiation cooling film has a total radiation dose of 7000 MJ / m.2 Even under ultraviolet radiation, the multilayer pseudo-leaf porous membrane can still maintain excellent mechanical properties.

[0035] Example 2 The difference between this embodiment and Embodiment 1 is that the thickness of the multilayer radiative cooling film is 500 μm, and the average diameter of the uniformly distributed micropores is 0.95 μm.

[0036] In step S1, the solid content of the inorganic particles in the protective layer is 60%; the solid content of the inorganic particles in the cooling layer is 60%, and the solid content ratio of barium sulfate and zinc oxide is 2:3.

[0037] Figure 9 The solar reflectance and MIR emissivity spectra of the two-layer multilayer radiative cooling film with a pseudo-blade structure prepared in Example 2 are shown. Figure 9 It can be seen that the multilayer radiative cooling film achieves a significant solar reflectivity of over 98% and a MIR emissivity of over 94%, which meets the spectral requirements of daytime radiative cooling materials.

[0038] Figure 10 This is a diagram illustrating the cooling effect of the two-layer, multi-layered radiative cooling film with a blade-like structure prepared in Example 2. (The diagram is presented in the original text.) Figure 10 It can be seen that the multi-layer radiative cooling film can reduce the temperature by 9.5°C during the day, and has a good radiative cooling effect.

[0039] Figure 11 This is a graph showing the mechanical properties of a two-layer, blade-like multilayer radiative cooling film prepared in Example 2 under ultraviolet light irradiation. Figure 11 It can be seen that the multilayer radiation cooling film has a total radiation dose of 7000 MJ / m. 2 Even under ultraviolet radiation, the multilayer pseudo-leaf porous membrane can still maintain excellent mechanical properties.

[0040] Comparative Example 1 Compared with Example 1, the difference in this comparative example is that: a single-layer radiation cooling film with synergistic effect of inorganic particles is prepared by mixing inorganic particles with high optical performance, ultra-high molecular weight polypropylene and pore-forming agent according to the solid content requirements of the cooling layer to prepare a single-layer radiation cooling film initial mixture; the prepared single-layer radiation cooling film initial mixture is placed in a co-extrusion device at a temperature 60°C higher than the melting temperature, and a gel film is obtained through a co-extrusion process; the gel film is placed in a pore-forming agent for extraction, and after drying to remove the pore-forming agent, a single-layer radiation cooling film with synergistic effect of inorganic particles is finally obtained.

[0041] In this comparative example, the thickness of the single-layer radiation cooling film is 500 μm; the inorganic particles with high optical performance are barium sulfate with a particle size of 1 μm and zinc oxide with a particle size of 0.1 μm, and the solid content accounts for 60%. In addition, the solid content ratio of barium sulfate and zinc oxide is 2:3.

[0042] Figure 12 The solar reflectance and MIR emissivity spectra of the monolayer radiative cooling film with synergistic effect of inorganic particles prepared in Comparative Example 1 are shown. (The last sentence appears to be incomplete and possibly refers to a different topic.) Figure 12 It can be seen that the single-layer radiation cooling film achieves a solar reflectivity of 91.45% and a MIR emissivity of 88.24%.

[0043] Figure 13 This is a graph showing the mechanical properties of the monolayer radiation cooling film with synergistic effect of inorganic particles prepared in Comparative Example 1 under ultraviolet light irradiation. Through... Figure 13 It can be seen that this single-layer radiation cooling film is effective against a total radiation dose exceeding 850 MJ / m. 2 When exposed to ultraviolet radiation, the mechanical properties of the single-layer radiation cooling film begin to decline significantly.

[0044] Figure 14 These are tests of solar reflectivity, infrared emissivity, and weather resistance for each embodiment and comparative example.

[0045] In summary, the multilayer radiative cooling film with a blade-like structure of the present invention exhibits an average reflectivity greater than 96% in the 0.28μm~2.5μm wavelength range and an average mid-infrared emissivity greater than 94% in the 8μm~13μm wavelength range. It maintains excellent mechanical and optical properties even when exposed to ultraviolet radiation with a total radiation dose of 7000 MJ / m².

[0046] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A multilayer radiative cooling film with a blade-like structure, characterized in that, The multilayer radiative cooling film uses ultra-high molecular weight polyolefin as a base and includes a protective layer and a cooling layer. The protective layer includes a protective base layer and inorganic particles for reflecting ultraviolet light. The protective base layer is designed to mimic the plasmodesmata structure of leaf epidermal cells, and the inorganic particles are densely packed within the protective base layer, mimicking the distribution of flavonoids in leaf epidermal cells, to resist ultraviolet radiation and block external pollutants. The cooling layer includes a cooling base layer and inorganic particles for reflecting sunlight. At least two types of inorganic particles are packed within the cooling base layer to improve radiative cooling performance. The protective base layer includes multiple micropores and connecting wires. The inorganic particles of the protective layer are placed inside the micropores, and multiple connecting wires are attached to the outer wall of the inorganic particles of the protective layer. The inorganic particles in the protective layer are either silicon dioxide or barium sulfate. When the inorganic particles of the protective layer are silicon dioxide, the inorganic particles of the cooling layer are a combination of titanium dioxide and silicon dioxide; When the inorganic particles of the protective layer are barium sulfate, the inorganic particles of the cooling layer are a combination of zinc oxide and barium sulfate.

2. The multilayer radiative cooling film with a blade-like structure according to claim 1, characterized in that, The multilayer radiative cooling film has a two-layer or three-layer structure; when the multilayer radiative cooling film has a three-layer structure, two protective layers are respectively set on both sides of the cooling layer, the thickness of the protective layer accounts for 10%~25%, and the thickness of the cooling layer accounts for 50%~80%; when the multilayer radiative cooling film has a two-layer structure, one protective layer is set on one side of the cooling layer, the thickness of the protective layer accounts for 10%~50%, and the thickness of the cooling layer accounts for 50%~90%.

3. The multilayer radiative cooling film with a blade-like structure according to claim 1, characterized in that, The ultra-high molecular weight polyolefin material used as the substrate of the multilayer radiative cooling film is any one or a combination of ultra-high molecular weight polyethylene and ultra-high molecular weight polypropylene.

4. A multilayer radiative cooling film with a pseudo-blade structure according to claim 1, characterized in that, The particle size range of the inorganic particles in the protective layer is 0.5 μm to 20 μm.

5. A multilayer radiative cooling film with a blade-like structure according to claim 4, characterized in that, In the protective layer, the solid content of the inorganic particles in the protective layer is 10% to 80%, and the solid content of the ultra-high molecular weight polyolefin is 20% to 90%.

6. A multilayer radiative cooling film with a blade-like structure according to claim 1, characterized in that, The particle size range of the inorganic particles in the cooling layer is 0.1 μm to 20 μm.

7. A multilayer radiative cooling film with a pseudo-blade structure according to claim 6, characterized in that, In the cooling layer, the solid content of inorganic particles in the cooling layer is 10% to 80%, and the solid content ratio of inorganic particles in the cooling layer of different materials varies in the range of 1:9 to 9:1, while the solid content ratio of ultra-high molecular weight polyolefin is 20% to 90%.

8. A method for preparing a multilayer radiative cooling film with a blade-like structure, characterized in that, The preparation of a multilayer radiative cooling film with a blade-like structure as described in any one of claims 1-7 includes the following steps: S1. Initial Mixing: According to the solid content requirements of the protective layer, inorganic particles, ultra-high molecular weight polyolefin and pore-forming agent are mixed to prepare the initial mixture of the protective layer; according to the solid content requirements of the cooling layer, inorganic particles, ultra-high molecular weight polyolefin and pore-forming agent are mixed to prepare the initial mixture of the cooling layer. S2, Co-extrusion: The protective layer initial mixture and the cooling layer initial mixture prepared in step S1 are placed in a multilayer co-extrusion equipment with a temperature 40℃~70℃ higher than the melting temperature. Through the co-extrusion process, an ultra-high molecular weight polyolefin network structure containing uniformly distributed inorganic particles is formed to obtain a multilayer gel film. S3. Removal of pore-forming agents: The multilayer gel membrane is placed in the extractant for extraction and dried to remove the pore-forming agents. The interior of the multilayer gel membrane is formed by the entanglement of ultra-high molecular weight polyolefin molecular chains, which forms a uniformly distributed microporous structure, similar to the intercellular plasmodesmata structure between leaf epidermal cells. Finally, a multilayer radiation cooling membrane with a leaf-like structure is obtained. The thickness of the multilayer radiation cooling film is 10 μm to 10 mm, and the average diameter of the uniformly distributed micropores is 0.01 μm to 1 μm.

9. The method for preparing a multilayer radiative cooling film with a blade-like structure according to claim 8, characterized in that, The pore-forming agent is one or more of the following: polyvinylpyrrolidone, polyethylene glycol, polyvinyl alcohol, mineral oil, petrolatum, vegetable oil, and decahydronaphthalene.

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