Multi-layer radiation cooling film with simulated-leaf structure and preparation method of multi-layer radiation cooling film

Abstract

The invention relates to the technical field of polymer processing and forming, in particular to a multi-layer radiation cooling film with a leaf-imitating structure and a preparation method of the multi-layer radiation cooling film. The invention relates to a multilayer radiation cooling film with a leaf-like structure, which takes ultra-high 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 used for reflecting ultraviolet light, the protective base layer is arranged by simulating an intercellular connecting wire structure of leaf epidermis cells, and the protective layer inorganic particles are tightly filled in the protective base layer by simulating distribution of flavonoid in the leaf epidermis cells so as to resist ultraviolet radiation and block external pollutants; the cooling layer comprises a cooling base layer and cooling layer inorganic particles used for reflecting sunlight, and the cooling layer inorganic particles are filled in the cooling base layer so as to improve radiation cooling performance. The preparation method of the multilayer radiation cooling film with the simulated leaf structure is used for preparing the multilayer radiation cooling film with the simulated leaf structure.

Description

Technical Field

[0001] The invention relates to the technical field of polymer processing and molding, and in particular to a multilayer radiation cooling film with a pseudo-blade structure and a preparation method thereof. Background Art

[0002] With the intensification of global climate change and the continuous development of the economy, the demand for refrigeration solutions in the fields of car clothing refrigeration, equipment refrigeration, building refrigeration, etc. is growing. However, traditional refrigeration technologies such as air conditioning have gradually failed to meet the needs of modern society due to high energy consumption, great environmental impact, and limited use scenarios. In response to these problems, Passive Radiative Cooling (PRC) technology, as a cutting-edge green refrigeration method, is receiving more and more attention.

[0003] PRC technology uses the high transparency of the Earth's atmosphere to infrared radiation in the mid-infrared (MIR) band (atmospheric window, λ=8µm~13µm) to design surface materials that can enhance the MIR radiation effect. This technology can directly dissipate the heat generated by an object into outer space in the form of MIR radiation, thereby achieving a cooling effect. In addition, the PRC film has a high solar reflectivity, which can effectively block direct sunlight during the day and provide all-weather passive cooling performance.

[0004] In recent years, the research focus of PRC technology has been mainly on different types of structures such as multilayer photonic structures, random media, metamaterials, aerogels, hydrogels and porous polymers. Due to their unique optical properties, these materials have shown good application prospects in many fields such as photovoltaics, building insulation, food preservation and electronic heat dissipation, and have achieved significant cooling effects. Despite this, most existing PRC structures often rely on complex and costly manufacturing processes, which makes large-scale industrial production difficult. At the same time, it is difficult for existing PRC materials to simultaneously meet high standards in terms of mechanical strength, elongation at break, toughness, etc., especially under the premise of ensuring good ultraviolet (UV) durability and long-term stability, and they face many challenges. Therefore, developing a PRC film that is both simple and economical, and has a long service life and excellent performance has become one of the key issues that need to be solved urgently. Summary of the invention

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

[0006] Another object of the present invention is to provide a method for preparing a multi-layer radiation cooling film with a pseudo-leaf structure. Based on low-cost raw materials, this method can achieve large-scale, high-efficiency and continuous production of a multi-layer pseudo-leaf porous structure film, with high production efficiency and low production cost.

[0007] The object of the present invention can be achieved by the following technical solutions: A multi-layer radiation cooling film with a pseudo-leaf structure, the multi-layer radiation cooling film uses ultra-high molecular weight polyolefin as the substrate, and includes a protective layer and a cooling layer; the protective layer includes a protective base layer and inorganic particles of the protective layer for reflecting ultraviolet light. The protective base layer is arranged by imitating the plasmodesmata structure of leaf epidermal cells, and the inorganic particles of the protective layer are closely filled in the protective base layer by imitating 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 of the cooling layer for reflecting sunlight. At least two kinds of inorganic particles of the cooling layer are filled in the cooling base layer to improve the radiation cooling performance.

[0008] As a preference, the protective base layer includes a plurality of micropores and connecting filaments, the inorganic particles of the protective layer are arranged in the micropores, and a plurality of connecting filaments are attached to the outer wall of the inorganic particles of the protective layer.

[0009] As a preference, the multi-layer radiation cooling film has a two-layer or three-layer structure; when the multi-layer radiation cooling film has a three-layer structure, two protective layers are respectively arranged on both sides of the cooling layer, the thickness ratio of the protective layer is 10% - 25%, and the thickness ratio of the cooling layer is 50% - 80%; when the multi-layer radiation cooling film has a two-layer structure, one protective layer is arranged on one side of the cooling layer, the thickness ratio of the protective layer is 10% - 50%, and the thickness ratio of the cooling layer is 50% - 90%.

[0010] As a preference, the ultra-high molecular weight polyolefin material used as the substrate of the multi-layer radiation 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 preference, the particle size range of the inorganic particles of the protective layer is 0.5μm - 20μm, and the materials for preparing the inorganic particles of the protective layer include one or more of silica, barium sulfate, calcium fluoride, and alumina.

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

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

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

[0015] A preparation method of a multi-layer radiation cooling film with a pseudo-leaf structure for preparing a multi-layer radiation cooling film with a pseudo-leaf structure as described above, comprising the following steps: S1. Preliminary mixing: According to the solid content requirements of the protective layer, mix the inorganic particles of the protective layer, ultra-high molecular weight polyolefin, and pore-forming agent to prepare a preliminary mixed solution of the protective layer; according to the solid content requirements of the cooling layer, mix the inorganic particles of the cooling layer, ultra-high molecular weight polyolefin, and pore-forming agent to prepare a preliminary mixed solution of the cooling layer; S2. Co-mixing and extrusion: Place the preliminary mixed solution of the protective layer and the preliminary mixed solution of the cooling layer prepared in step S1 into a multi-layer co-extrusion device with a temperature 40°C to 70°C higher than the melting temperature, and through the co-mixing and extrusion process, form a network structure of ultra-high molecular weight polyolefin containing uniformly distributed inorganic particles to obtain a multi-layer gel film; S3. Removing the pore-forming agent: Place the multi-layer gel film in an extractant for extraction, and after drying to remove the pore-forming agent, a uniformly distributed microporous structure is formed inside the multi-layer gel film due to the entanglement of ultra-high molecular weight polyolefin molecular chains, similar to the plasmodesma structure between leaf epidermal cells, and finally obtain a multi-layer radiation cooling film with a pseudo-leaf structure; The thickness of the multi-layer 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 preference, the pore-forming agent is one or more of polyvinylpyrrolidone, polyethylene glycol, polyvinyl alcohol, mineral oil, petrolatum, vegetable oil, and decalin.

[0017] The working principle of the multi-layer radiation cooling film with a pseudo-leaf structure of the present invention: The design inspiration of this multi-layer radiative cooling film comes from the porous structure with plasmodesmata in the leaf epidermis of plants. That is, epidermal cells are closely arranged to form an effective ultraviolet radiation barrier, supplemented by flavonoids widely embedded in leaf epidermal cells. Flavonoids have antioxidant ability and can protect key parts such as the cell nucleus, cell membrane, and chloroplast from damage by ultraviolet radiation. This multi-layer radiative cooling film uses ultra-high molecular weight polyolefin as the substrate and mainly consists of two layers: a protective layer and a cooling layer. The protective layer is tightly filled with inorganic particles of the protective layer with high ultraviolet light reflection performance (such as silica), while the cooling layer is doped with various inorganic particles of the cooling layer with high optical properties (such as titanium dioxide and silica).

[0018] Protective layer: Ultra-high molecular weight polyolefin is used as the base material to form a structure similar to plasmodesmata in leaf epidermal cells, and inorganic particles of the protective layer with high ultraviolet reflectivity are tightly filled in the plasmodesmata structure. For example, ultra-high molecular weight polyethylene is used as the material for preparing the protective base layer, and silica is used as the material for preparing the inorganic particles of the protective layer. Silica shows excellent reflectivity in the ultraviolet wavelength range, and a considerable part of ultraviolet radiation can be attenuated when passing through silica. In addition, silica also shows outstanding chemical stability under ultraviolet radiation, ensuring that the protective layer has good weather resistance under ultraviolet irradiation. Therefore, silica is embedded in the plasmodesmata structure formed by ultra-high molecular weight polyethylene in a form similar to flavonoids to resist ultraviolet radiation and prevent photocatalytic reactions caused by some inorganic particles in the cooling layer.

[0019] Cooling layer: At least two inorganic particles of the cooling layer are doped in the cooling base layer made of ultra-high molecular weight polyolefin. Different inorganic particles of the cooling layer with different materials and different particle sizes act synergistically. For example, ultra-high molecular weight polyethylene is used as the material for preparing the cooling base layer, and titanium dioxide and silica are used as the materials for preparing the inorganic particles of the cooling layer. Silica compensates for the decrease in the solar light reflectivity caused by the high light absorption rate of titanium dioxide in the ultraviolet wavelength range. At the same time, titanium dioxide has a large extinction coefficient and a high MIR emissivity, which can compensate for the decrease in the MIR emissivity caused by the significant decrease in the extinction coefficient of silica in the wavelength range of 10μm - 12μm. Therefore, titanium dioxide can also be used as an emissive material to well supplement silica to achieve high-efficiency and long-lasting passive cooling.

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

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

[0022] (3) Optimized structural design: By reasonably designing the ratio and thickness of the protective layer and the cooling layer, and precisely controlling the solid content and particle size distribution of the inorganic particles in each layer, the radiative cooling effect is further enhanced.

[0023] (4) Feasibility of large-scale production: The large-scale manufacturing of this multi-layer pseudo-leaf porous structure film can be achieved using commercially available multi-layer coextrusion equipment, reducing production costs and technical thresholds, which is conducive to the wide promotion and application of PRC technology.

[0024] (5) Economic sustainability: The raw materials used are extensive and inexpensive, including various ultra-high molecular weight polyolefin base materials (such as ultra-high molecular weight polyethylene, ultra-high molecular weight polypropylene, etc.) and inorganic particles in the protective layer and inorganic particles in the cooling layer (such as silica, titanium dioxide, etc.), which not only ensure the high performance of the product but also meet the requirements of economic sustainable development.

[0025] (6) Easy to process and manufacture: The preparation method is simple and feasible. Each step from initial mixing to co-mixing extrusion and then to porogen removal is clear and specific, ensuring the uniformity and consistency of the final product. In addition, various types of porogens can be used, and the most suitable one or several combinations can be selected according to actual needs, increasing the flexibility of the process. Brief Description of the Drawings

[0026] Figure 1 is a schematic structural diagram of a multi-layer radiative cooling film with a pseudo-leaf-like structure of a two-layer structure; Figure 2 is an EDS cross-sectional schematic diagram of a multi-layer radiative cooling film with a pseudo-leaf-like structure of a two-layer structure; Figure 3 is a SEM cross-sectional schematic diagram of the protective base layer of a multi-layer radiative cooling film with a pseudo-leaf-like structure of a two-layer structure; Figure 4 It is a schematic SEM cross-section view of the cooling base layer of a multi-layer radiation cooling film with a quasi-blade structure and a two-layer structure; Figure 5 It is a schematic structural view of a multi-layer radiation cooling film with a quasi-blade structure and a three-layer structure; Figure 6 It is the solar reflectance and MIR emissivity spectra of a two-layer multi-layer radiation cooling film with a quasi-blade structure prepared in Example 1; Figure 7 It is the temperature reduction effect diagram of a two-layer multi-layer radiation cooling film with a quasi-blade structure prepared in Example 1; Figure 8 It is the mechanical property diagram of a two-layer multi-layer radiation cooling film with a quasi-blade structure prepared in Example 1 under ultraviolet light irradiation; Figure 9 It is the solar reflectance and MIR emissivity spectra of a two-layer multi-layer radiation cooling film with a quasi-blade structure prepared in Example 2; Figure 10 It is the temperature reduction effect diagram of a two-layer multi-layer radiation cooling film with a quasi-blade structure prepared in Example 2; Figure 11 It is the mechanical property diagram of a two-layer multi-layer radiation cooling film with a quasi-blade structure prepared in Example 2 under ultraviolet light irradiation; Figure 12 It is the solar reflectance and MIR emissivity spectra of a single-layer radiation cooling film with the synergistic effect of inorganic particles prepared in Comparative Example 1; Figure 13 It is the mechanical property diagram of a single-layer radiation cooling film with the synergistic effect of inorganic particles prepared in Comparative Example 1 under ultraviolet light irradiation; Figure 14 It is the solar reflectance, infrared emissivity and weather resistance tests of each example and comparative example; Wherein: 1. protective base layer; 2. cooling base layer; 3. inorganic particles in the protective layer; 4. inorganic particles in the cooling layer; 5. first protective layer; 6. cooling layer; 7. second protective layer. Detailed implementation manners

[0027] Example 1 A multi-layer radiative cooling film with a leaf-like structure, the multi-layer radiative cooling film uses ultra-high molecular weight polyolefin as the substrate, and includes a protective layer and a cooling layer; the protective layer includes a protective base layer and inorganic particles of the protective layer for reflecting ultraviolet light, the protective base layer is arranged by imitating the plasmodesmata structure of leaf epidermal cells, and the inorganic particles of the protective layer are tightly filled in the protective base layer by imitating 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 of the cooling layer for reflecting sunlight, and at least two kinds of inorganic particles of the cooling layer are filled in the cooling base layer to improve the radiative cooling performance.

[0028] As Figure 1 and Figure 2 shown, the multi-layer radiative cooling film has a two-layer structure, a protective layer is arranged on one side of the cooling layer, the thickness ratio of the protective layer is 50%, and the thickness ratio of the cooling layer is 50%. As Figure 3 shown, the protective layer includes inorganic particles of the protective layer with high ultraviolet light reflectivity, a protective base layer and micropores, the protective base layer includes a plurality of micropores and connecting filaments, the inorganic particles of the protective layer are arranged in the micropores, and a plurality of connecting filaments are attached to the outer wall of the inorganic particles of the protective layer. The inorganic particles of the protective layer located in different micropores are adhered by connecting filaments to form the plasmodesmata structure of the protective base layer. Through the synergistic effect of the plasmodesmata structure of the protective base layer and the high ultraviolet light reflectivity of the inorganic particles of the protective layer, its ultraviolet stability can be guaranteed. As Figure 4 shown, the cooling layer includes two kinds of inorganic particles of the cooling layer with high optical properties, a cooling base layer and micropores, and the synergistic effect between two different materials and different particle sizes of the inorganic particles of the cooling layer can be used to enhance the radiative cooling performance of the multi-layer radiative cooling film.

[0029] As Figure 5 shown, in addition to the two-layer structure mentioned above, the multi-layer radiative cooling film can also be set into a three-layer structure. Specifically, the multi-layer radiative cooling film includes a first protective layer, a cooling layer and a second protective layer arranged in sequence, and the two protective layers are respectively arranged on both sides of the cooling layer. The first protective layer and the second protective layer include inorganic particles of the protective layer with high ultraviolet light reflectivity, a protective base layer and micropores. Through the synergistic effect of the plasmodesmata structure of the protective base layer and the high ultraviolet light reflectivity of the inorganic particles of the protective layer, its ultraviolet stability can be guaranteed. The cooling layer includes inorganic particles of the cooling layer with high optical properties, a cooling base layer and micropores, and the synergistic effect between two different materials and different particle sizes of the inorganic particles of the cooling layer can be used to enhance the radiative cooling performance of the multi-layer radiative cooling film.

[0030] A preparation method of a multi-layer radiative cooling film with a leaf-like structure, which is specifically completed according to the following steps: A method for preparing a multi-layer radiative cooling film with a pseudo-leaf structure, which is used to prepare a multi-layer radiative cooling film with a pseudo-leaf structure as described above, includes the following steps: S1. Initial mixing: According to the solid content requirements of the protective layer, mix the inorganic particles of the protective layer, ultra-high molecular weight polyolefin, and pore-forming agent to prepare the initial mixed solution of the protective layer; according to the solid content requirements of the cooling layer, mix the inorganic particles of the cooling layer, ultra-high molecular weight polyolefin, and pore-forming agent to prepare the initial mixed solution of the cooling layer; S2. Co-extrusion blending: Place the initial mixed solution of the protective layer and the initial mixed solution of the cooling layer prepared in step S1 into a multi-layer co-extrusion device with a temperature 60 °C higher than the melting temperature, and form a network structure of ultra-high molecular weight polyolefin containing uniformly distributed inorganic particles through the co-extrusion blending process to obtain a multi-layer gel film.

[0031] S3. Removal of pore-forming agent: Place the multi-layer gel film in an extractant for extraction, and after drying to remove the pore-forming agent, a uniformly distributed microporous structure is formed inside the multi-layer gel film due to the entanglement of ultra-high molecular weight polyolefin molecular chains, similar to the plasmodesmata structure between leaf epidermal cells, and finally obtain a multi-layer radiative cooling film with a pseudo-leaf structure; In this embodiment, the thickness of the multi-layer radiative 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 ratio 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, and the solid content ratio is 40%. In addition, the solid content ratio of barium sulfate and zinc oxide is 1:4; the ultra-high molecular weight polyolefin is ultra-high molecular weight polypropylene.

[0032] Figure 6 is the solar reflectance and MIR emissivity spectra of the two-layer structured multi-layer radiative cooling film with a pseudo-leaf structure prepared in Example 1. By Figure 6 It can be seen that the multi-layer radiative cooling film achieves a significant solar reflectance of more than 96% and an MIR emissivity of more than 95%, meeting the spectral requirements of daytime radiative cooling materials.

[0033] Figure 7 is the cooling effect diagram of the two-layer structured multi-layer radiative cooling film with a pseudo-leaf structure prepared in Example 1. By 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 is the mechanical property diagram of the two-layer structured multi-layer radiative cooling film with a pseudo-leaf structure prepared in Example 1 under ultraviolet light irradiation. By Figure 8 It can be seen that when the multi-layer radiative cooling film faces a total radiation dose of 7000 MJ / m2 When exposed to ultraviolet radiation, the multi-layer quasi-leaf-like porous structure film can still maintain excellent mechanical properties.

[0035] Example 2 Compared with Example 1, the difference in this example is that: the thickness of the multi-layer 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 ratio of the inorganic particles in the protective layer is 60%; the solid content ratio 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 are the solar reflectance and MIR emissivity spectra of the two-layer structured multi-layer radiative cooling film with a quasi-leaf-like structure prepared in Example 2. By Figure 9 It can be seen that the multi-layer radiative cooling film achieves a remarkable solar reflectance of more than 98% and an MIR emissivity of more than 94%, meeting the spectral requirements of daytime radiative cooling materials.

[0038] Figure 10 are the cooling effect diagrams of the two-layer structured multi-layer radiative cooling film with a quasi-leaf-like structure prepared in Example 2. By Figure 10 It can be seen that the multi-layer radiative cooling film can reduce the temperature by 9.5 °C during the day, having a good radiative cooling effect.

[0039] Figure 11 are the mechanical property diagrams of the two-layer structured multi-layer radiative cooling film with a quasi-leaf-like structure prepared in Example 2 under ultraviolet light irradiation. By Figure 11 It can be seen that when facing ultraviolet radiation with a total radiation dose of 7000 MJ / m 2 the multi-layer quasi-leaf-like porous structure film 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 radiative cooling film with the synergistic effect of inorganic particles is prepared by mixing inorganic particles with high optical properties, ultra-high molecular weight polypropylene, and a pore-forming agent according to the solid content requirements of the cooling layer to obtain a primary mixed solution of the single-layer radiative cooling film; the prepared primary mixed solution of the single-layer radiative cooling film is placed in a co-extrusion device with a temperature 60 °C higher than the melting temperature, and a gel film is obtained through a co-blending and 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 radiative cooling film with the synergistic effect of inorganic particles is finally obtained.

[0041] In this comparative example, the thickness of the single-layer radiative cooling film is 500 μm; the inorganic particles with high optical properties 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 ratio is 60%. In addition, the solid content ratio of barium sulfate to zinc oxide is 2:3.

[0042] Figure 12 are the solar reflectance and MIR emissivity spectra of the single-layer radiative cooling film with the synergistic effect of inorganic particles prepared in Comparative Example 1. By Figure 12 It can be seen that the single-layer radiative cooling film achieves a solar reflectance of 91.45% and a MIR emissivity of 88.24%.

[0043] Figure 13 is the mechanical property diagram of the single-layer radiative cooling film with the synergistic effect of inorganic particles prepared in Comparative Example 1 under ultraviolet light irradiation. By Figure 13 It can be seen that when the single-layer radiative cooling film faces ultraviolet radiation with a total radiation dose exceeding 850 MJ / m 2 , the mechanical properties of the single-layer radiative cooling film begin to decline significantly.

[0044] Figure 14 are the solar reflectance, infrared emissivity, and weather resistance tests of each example and comparative example.

[0045] Generally speaking, the multi-layer radiative cooling film with a pseudo-blade structure of the present invention has an average reflectance greater than 96% in the wavelength range of 0.28 μm to 2.5 μm and an average mid-infrared emissivity greater than 94% in the wavelength range of 8 μm to 13 μm. Even when facing ultraviolet radiation with a total radiation dose of 7000 MJ / m2, it can still maintain excellent mechanical and optical properties.

[0046] The above-described embodiments merely represent several implementation manners of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the patent of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention should be subject to the appended claims.

Claims

1. A multilayer radiation cooling film with a pseudo-blade structure, characterized in that: The multilayer radiation cooling film is based on ultra-high molecular weight polyolefin, and 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 imitates the intercellular filament structure of leaf epidermal cells, and the protective layer inorganic particles imitate the distribution of flavonoids in leaf epidermal cells and are tightly filled in the protective base layer to resist ultraviolet radiation and block external pollutants; the cooling layer includes a cooling base layer and cooling layer inorganic particles for reflecting sunlight, and at least two cooling layer inorganic particles are filled in the cooling base layer to improve the radiation cooling performance.

2. The multilayer radiation cooling film with a pseudo-blade structure according to claim 1, characterized in that: The protective base layer comprises a plurality of micropores and connecting filaments, the protective layer inorganic particles are arranged in the micropores, and a plurality of connecting filaments are attached to the outer walls of the protective layer inorganic particles.

3. The multilayer radiation cooling film with a pseudo-blade structure according to claim 1, characterized in that: The multilayer radiation cooling film has a two-layer or three-layer structure; when the multilayer radiation cooling film has a three-layer structure, two protective layers are respectively arranged 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 radiation cooling film has a two-layer structure, one protective layer is arranged 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%.

4. The multilayer radiation cooling film with a pseudo-blade structure according to claim 1, characterized in that: The ultra-high molecular weight polyolefin material used as the substrate of the multi-layer 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.

5. The multilayer radiation cooling film with a pseudo-blade structure according to claim 1, characterized in that: The particle size of the inorganic particles of the protective layer ranges from 0.5 μm to 20 μm, and the material for preparing the inorganic particles of the protective layer includes one or more of silicon dioxide, barium sulfate, calcium fluoride, and aluminum oxide.

6. The multilayer radiation cooling film with a pseudo-blade structure according to claim 5, characterized in that: In the protective layer, the solid content of the inorganic particles in the protective layer accounts for 10% to 80%, and the solid content of the ultra-high molecular weight polyolefin accounts for 20% to 90%.

7. The multilayer radiation cooling film with a pseudo-blade structure according to claim 6, characterized in that: The particle size of the cooling layer inorganic particles ranges from 0.1 μm to 20 μm, and the materials used to prepare the cooling layer inorganic particles include two or more of titanium dioxide, zinc oxide, calcium fluoride and silicon dioxide.

8. The multilayer radiation cooling film with a pseudo-blade structure according to claim 7, characterized in that: In the cooling layer, the solid content of the cooling layer inorganic particles accounts for 10%~80%, wherein the solid content ratio of the cooling layer inorganic particles of different materials can vary in the range of 1:9~9:1, and the solid content of the ultra-high molecular weight polyolefin accounts for 20%~90%.

9. A method for preparing a multilayer radiation cooling film having a pseudo-blade structure, characterized in that: The method for preparing a multilayer radiation cooling film having a pseudo-blade structure as claimed in claim 8 comprises the following steps: S1. Preliminary mixing: according to the solid content requirement of the protective layer, inorganic particles of the protective layer, ultra-high molecular weight polyolefin and porogen are mixed to prepare a preliminary mixed solution of the protective layer; according to the solid content requirement of the cooling layer, inorganic particles of the cooling layer, ultra-high molecular weight polyolefin and porogen are mixed to prepare a preliminary mixed solution of the cooling layer; S2, co-extrusion: the protective layer pre-mixed liquid and the cooling layer pre-mixed liquid prepared in step S1 are placed in a multi-layer co-extrusion device at a temperature 40°C to 70°C higher than the melting temperature, and a co-extrusion process is performed to form an ultra-high molecular weight polyolefin network structure containing uniformly distributed inorganic particles, thereby obtaining a multi-layer gel film; Removal of porogens: The multilayer gel membrane is placed in an extractant for extraction, and after drying and removing the porogens, the interior of the multilayer gel membrane forms a uniformly distributed microporous structure due to the entanglement of ultra-high molecular weight polyolefin molecular chains, which is similar to the intercellular filament structure between leaf epidermal cells, and finally a multilayer radiation cooling membrane with a pseudo-leaf 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.

10. The method for preparing a multilayer radiation cooling film having a pseudo-blade structure according to claim 9, characterized in that: The porogen is one or more of polyvinyl pyrrolidone, polyethylene glycol, polyvinyl alcohol, mineral oil, vaseline, vegetable oil, and decahydronaphthalene.

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