Radiative cooling microporous elastomer composite membrane, method and application thereof

Abstract

The present application relates to a kind of radiation cooling microporous elastomer composite film and its method and application, belong to the technical field of radiation cooling material.The composite film includes microporous membrane and waterproof coating arranged in the microporous membrane, the microporous membrane has micro-nano pore structure;The microporous membrane includes base layer and at least one functional microporous layer sequentially arranged on the base layer.Because the microporous membrane in the composite film has micro-nano pore structure, so that it has the advantages of light, soft, long service life, and functional microporous layer is by functional filler is through with elastomer composite foaming, without additional use of adhesive, so that functional filler is not easy to peel off during use, with the advantage of long service life.The radiation cooling composite film of the present application is soft, lightweight, and can be applied to the field of outdoor passive cooling in summer, such as building, automobile, clothing, tent, etc.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of radiative cooling materials, in particular to a radiative cooling microporous elastomer composite film and a method and application thereof. BACKGROUND

[0002] Radiative cooling materials can dissipate human heat without external energy input, providing continuous cooling for personal thermal management, and have wide application prospects in the wearable field. However, the radiative cooling conditions required by different environmental conditions are also different. When the environmental temperature is higher than the material temperature, the external environment should be prevented from heating the material itself, and a narrow-band emitter should be used, that is, only in the atmospheric window 8-13 μm wave band has high emissivity, and when the environmental temperature is less than the material temperature, the material should be allowed to dissipate heat as much as possible, that is, a wide-band emitter is used, which has high reflectivity in the full wave band and should also have a good heat dissipation structure.

[0003] The radiative cooling film reported at present with full wave band radiative cooling effect is realized by laminating multiple films with different wave band absorption and / or reflection performance. The selected film substrate is fabric, polymer film, etc., and the selected functional microporous layer is prepared by coating, laminating, etc. In the laminating process of the multi-layer film, an adhesive is usually used for bonding and forming, which leads to the problems of high density and high hardness of the composite film, and the composite film is not easy to bend. At the same time, the bonding process also has the problems of complex processing technology, easy peeling of the bonding layer, and poor air permeability of the composite film, which limits the commercial application range of the composite cooling film, especially it is difficult to meet the requirements of flexibility, light weight, air permeability, etc. of the material in the field of personal thermal management. SUMMARY

[0004] The purpose of the present application is to overcome the shortcomings of the prior art and provide a radiative cooling microporous elastomer composite film and a method and application thereof, which has the characteristics of good spectral selectivity, high reflectivity and high emissivity, can significantly cool in hot outdoor environment in summer, and the microporous elastomer composite film has an integrated structure, does not need to be bonded by an adhesive between layers, has the advantages of light weight, soft texture, waterproof and moisture permeability, can be produced on a large scale, and has high processing efficiency.

[0005] To achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0006] In a first aspect, the present application provides a radiative cooling microporous elastomer composite film, comprising a microporous membrane and a waterproof coating layer arranged on the microporous membrane, the microporous membrane having a microporous structure; the microporous membrane comprises a base layer and at least one functional microporous layer arranged on the base layer in sequence; wherein the base layer is prepared from an elastomer; and the functional microporous layer is prepared from an elastomer and a functional filler.

[0007] The micro-nano-porous membrane of the composite membrane has a micro-nano-cellular structure, which has the advantages of light weight, softness and long service life. Moreover, the functional microporous layer is formed by compounding and foaming the functional filler with the elastomer, so that the functional filler can be embedded in the microporous structure, without the need for additional adhesive, so that the functional filler is not easy to peel off during use, and has the advantage of long service life. Then, the functional microporous layer is attached with a waterproof coating, which can enable the composite membrane to be applied outdoors, enhancing its waterproof and corrosion-resistant properties. The radiation cooling microporous elastomer composite membrane of the present application has a reflectivity of ≥85% in the 0.3-2.5 μm wave band of sunlight, preferably ≥92%; an emissivity of ≥85% in the atmospheric window of 8-13 μm, preferably ≥92%, and a phase change enthalpy of 180.4 KJ / Kg.

[0008] Preferably, the micro-nano-porous membrane comprises the following raw materials by weight: elastomer 70-100 parts, functional filler 5-20 parts, lubricant 2-3 parts, crosslinking agent 0.2-1 part, antioxidant 0.1-0.5 part.

[0009] Preferably, the elastomer in the preparation raw materials of the functional microporous layer and the micro-nano-porous membrane layer is at least one of polyurethane thermoplastic elastomer, polyester thermoplastic polyester elastomer, nylon elastomer, EVA crosslinked elastomer, polyolefin crosslinked elastomer, styrene crosslinked elastomer, and vulcanized rubber.

[0010] Specifically, different vibration modes of polymers with different molecular structures have different extinction peaks in the long-wave infrared window. When the above-mentioned elastomer is selected as the base material, the molecular vibration of the elastomer can be concentrated in the 8-13 μm wave band, which can keep the heat gain from sunlight at a minimum, and help a large amount of infrared absorption and emission in the atmospheric window. At the same time, the pore size distribution of the micro-nano-porous membrane is between 0.1-2.0 μm and far away from the mid-infrared wave band, which can effectively achieve high visible light reflectivity.

[0011] Preferably, the functional filler is at least one of silicon dioxide, chromium dioxide, titanium dioxide, silicon nitride, aluminum phosphate, and aluminum oxide; and the particle size of the functional filler is 0.05-10 μm. Such inorganic oxide functional particles have high emissivity in the mid-to-far infrared wave band, and high reflectivity in the near-infrared wave band, which can further improve the cooling effect in the system.

[0012] Preferably, the preparation raw materials of the coating include at least one of γ-methacryloxypropyltrimethoxysilane (MPTMS), N-methyl perfluorooctylsulfonyl amido acrylate (MPSAEA), and methyl methacrylate. The above-mentioned three materials can improve the wear resistance and water resistance of the composite membrane, so the coating mainly plays the effects of waterproofing, wear resistance and corrosion resistance, thereby improving the service life of the composite membrane.

[0013] Preferably, the average cell size of the micro-nano-porous membrane is 0.3-200 μm, more preferably 0.3-150 μm, and the porosity is 60-97%, more preferably 70-95%.

[0014] Sunlight contains ultraviolet, visible light, infrared and other light waves with a wavelength of 0.3-2.5 μm. When light waves enter a medium, the light waves will be reflected, refracted and scattered at the interface when propagating in a non-uniform medium. Microcellular foaming forms a large number of closed pores in transparent or translucent polymers, and the microcellular material appears white, and the whiteness increases with the decrease of the cell size and the increase of the porosity. When the size of the cell is comparable to the wavelength of the light wave, the cell of the microcellular polymer will cause significant scattering of sunlight, and the white microcellular polymer will exhibit diffuse reflection of sunlight. Based on this, the present application limits the cell size and porosity of the functional microcellular layer and the micro-nano-porous membrane layer, so that they exhibit good reflectivity and emissivity.

[0015] Preferably, the total thickness of the radiation cooling microcellular elastomer composite membrane is 0.3-5.0 mm.

[0016] In a second aspect, the present application provides a preparation method of the radiation cooling microcellular elastomer composite membrane, comprising the following steps:

[0017] (1) preparing an elastomer and a combination of elastomer and functional filler into a composite membrane, respectively;

[0018] (2) foaming the composite membrane to obtain a micro-nano-porous membrane with a micro-nano-cell structure, the micro-nano-porous membrane comprising the base layer and at least one functional microcellular layer attached to the base layer;

[0019] (3) hot pressing and cooling the micro-nano-porous membrane to shape, and then coating the coating layer on the surface of the functional microcellular layer to obtain the radiation cooling microcellular elastomer composite membrane.

[0020] The above method melts and stacks the elastomer, the elastomer / functional filler membrane to form a composite membrane comprising a base film and a functional elastomer film, and then foams the composite membrane to obtain a micro-nano-porous membrane with a micro-nano-cell structure, and then hot presses and cools the micro-nano-porous membrane to shape, and then coats the coating layer on the surface of the functional microcellular layer of the second composite membrane to obtain a micro-nano-porous membrane with an integrated structure, and then coats the coating layer on the surface of the functional microcellular layer to obtain the radiation cooling microcellular elastomer composite membrane. By controlling the stacking structure, the cell structure, the type, the content and the dispersion state of the functional filler, the composite membrane reflects different wave bands of sunlight and emits infrared waves, and a microcellular elastomer radiation cooling composite membrane with good full-waveband sunlight radiation cooling effect, light weight and softness is obtained.

[0021] Preferably, in the step (1), the preparation step of the composite film comprises sequentially mixing the raw materials for preparing the base layer and the functional microporous layer, co-extrusion of double-screw extruder, rolling, cooling, to obtain the composite film. More preferably, the extrusion is performed in an extruder, and the temperature of each temperature zone is 110°C, 180°C, 190°C, 185°C, 180°C in turn.

[0022] Preferably, in the step (1), the preparation step of the composite film comprises sequentially mixing the raw materials for preparing the base layer and the functional microporous layer, co-extrusion of double-screw extruder, rolling, cooling, to obtain the composite film. More preferably, the extrusion is performed in an extruder, and the temperature of each temperature zone is 110°C, 180°C, 190°C, 185°C, 180°C in turn.

[0023] More preferably, in the functional elastic film, in order to improve the dispersion state of the functional filler in the elastomer, the functional filler is pre-processed into a polymer / inorganic oxide powder master batch by using a polymer resin as a carrier through double-screw melting processing. The polymer / inorganic oxide nano-powder master batch is processed by double-screw melting extrusion. The polymer carrier used in the master batch is the same as or similar to the elastomer. The content of the functional filler in the polymer master batch is 1-10wt%.

[0024] More preferably, in the step (1), the content of the functional filler in the composite film can vary in a single gradient, a double gradient, or no gradient.

[0025] Preferably, in the step (2), the foaming treatment comprises the following steps: first, immersing the composite film in a supercritical fluid for the first foaming, and then continuing to heat for the second foaming, to obtain a micro-nano-porous film with micro-nano-cellular structure.

[0026] More preferably, the supercritical fluid is CO2 fluid, N2 fluid, and a mixture of the two fluids, wherein the solubility of the supercritical fluid in the polymer is 0.8-15wt%.

[0027] More preferably, in order to ensure that the integrated multilayer elastomer composite film is uniformly expanded during the supercritical foaming process, the elastomers used in the base layer and the functional microporous layer are of the same type and have the same or similar resin hardness, or the elastomers in each layer are of different types but are compatible and have similar foaming behaviors. This is because the hardness or modulus affects the expansion behavior of the elastomer supercritical fluid micro-foaming process. In general, the foaming temperature of a plastic elastomer with high hardness or modulus is high, while the foaming temperature of an elastomer with low hardness or modulus is low. At the same time, the compatibility of the multilayer system affects the internal uniformity of the integrated microporous material. For example, if the compatibility of the multilayer system is poor, it will result in holes in the integrated microporous material.

[0028] Preferably, in step (3), the temperature of the hot pressing is 130-160°C, and the temperature of the cooling is 4-15°C. The hot pressing / cooling shaping can change the thickness of the micro-nano-porous film with micro-nano-porous structure, so that the thickness of the micro-nano-porous film is controllable.

[0029] Preferably, in step (3), each coating layer can be compounded on the surface of the functional microporous layer of the micro-nano-porous film by using an adhesive through dipping, padding or high-pressure spraying. The adhesive is an elastic glue, including polyurethane glue and the like.

[0030] In a third aspect, the present application provides the use of the radiation cooling composite film in the preparation of buildings, cars, clothes, tents.

[0031] Compared with the prior art, the present application has the following advantages:

[0032] (1) The micro-nano-porous film of the radiation cooling elastomer composite film of the present application has a micro-nano-cell structure, so that it has the advantages of light weight, softness and long service life. Moreover, the functional microporous layer is formed by compounding and foaming the functional filler with the elastomer, so that the functional filler can be embedded in the microporous structure without the need for additional adhesive. Therefore, the functional filler is not easy to peel off during use, and has the advantage of long service life. Then, the functional microporous layer is attached with a coating layer with different functions, which can further improve the cooling effect. The radiation cooling composite film of the present application is soft and lightweight, and can be applied to the outdoor passive cooling field in summer, such as buildings, cars, clothes and tents.

[0033] (2) The preparation method of the radiation cooling elastomer composite film of the present application first melts and stacks the elastomer and the elastomer / functional filler to form a composite film, then foams the composite film to obtain a micro-nano-porous film with a base layer and a functional microporous layer, and then performs hot pressing and cooling setting, and then coats a coating layer on the surface of the functional microporous layer to prepare a structure-integrated radiation cooling microporous elastomer composite film, which realizes the reflection of different wave bands of sunlight and the emission of infrared waves, and obtains a light-weight, soft microporous elastomer radiation cooling composite film with good full-waveband sunlight radiation cooling effect. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 The radiation cooling elastomer composite film structure of Examples 1-9 is shown in the schematic diagram.

[0035] Among them, Figure 1 In the middle: 1, base layer; 2, functional microporous layer; 3, waterproof coating. DETAILED DESCRIPTION

[0036] In order to better illustrate the purpose, technical scheme and advantages of the present application, the present application will be further described below in conjunction with specific examples.

[0037] In the following examples, the experimental methods used are conventional methods unless otherwise specified, and the materials, reagents, etc. used are commercially available unless otherwise specified.

[0038] In the following examples, the materials of the radiation cooling microporous elastomer composite film are as follows:

[0039] Polyolefin elastomer 1: EVA, 360, USA DuPont;

[0040] Polyolefin elastomer 2: EVA, 410, USA DuPont;

[0041] Polyethylene elastomer: POE, 8150, USA Dow Chemical Company;

[0042] Styrene elastomer: SEBS, H1053, Japan Asahi Kasei;

[0043] Thermoplastic polyurethane elastomer: TPU, HF-1385AX, Huafeng;

[0044] Functional powder: micron-sized SiO2, average size 1 μm, commercially available

[0045] Functional powder: nano-sized SiO2, average size 20 nm, commercially available

[0046] Crosslinking agent: BIPB, commercially available

[0047] Antioxidant: antioxidant 1010, BASF.

[0048] Examples 1-9

[0049] Examples 1-9 are radiation-cooled microporous elastomer composite membranes, such as Figure 1 As shown, the composite membrane comprises a microporous membrane and a waterproof coating 3 disposed on the microporous membrane, i.e., the composite membrane has a three-layer structure. The microporous membrane has a micro-nano pore structure. The microporous membrane includes a base layer 1 and a functional microporous layer 2 sequentially disposed on the base layer 1. The base layer 1 is prepared from an elastomer. The functional microporous layer 2 is prepared from an elastomer and a functional filler. The functional microporous layer 2 also includes at least one of the following raw materials: lubricant, crosslinking agent, and antioxidant. The base layer 1 and the functional microporous layer 2 use the same type of elastomer. The formulations of the raw materials for each layer are shown in Table 1.

[0050] The preparation method of the radiation-cooled microporous elastomer composite membrane is as follows:

[0051] (1) The raw materials for preparing the base layer 1 and the functional microporous layer 2 are highly mixed, and then subjected to open milling and twin-screw extrusion casting to obtain the base elastic membrane and the functional elastic membrane. After rolling and cooling, a composite membrane is obtained, which is an integrated cross-linked multilayer elastomer composite membrane. The composite membrane adopts a three-layer co-extrusion step. The base layer 1 does not contain functional fillers, and the functional fillers in the composite membrane exhibit a gradient change, so it actually contains two layers of functional elastic membrane. The extrusion temperature is 100℃.

[0052] (2) The composite membrane is immersed in CO2 fluid to obtain a specific solubility, as detailed in Table 1. Then, the temperature is raised to 100°C and the pressure is controlled at 20MPa to induce the nucleation and growth of the foam pores, which is the second foaming, to obtain an expanded microporous membrane with a micro-foam structure. The microporous membrane includes the base layer 1 and the functional microporous layer 2 to which the base layer 1 and the functional microporous layer are attached.

[0053] (3) The microporous membrane is hot-pressed and cooled for shaping, and then a waterproof coating 3 is coated on the surface of the functional microporous layer 2 to obtain a radiation-cooled microporous elastomer composite membrane. The hot-pressing temperature is 150°C and the cooling temperature is 10°C.

[0054] Table 1. Formulations (parts by weight) used for the composite membranes in Examples 1-9.

[0055]

[0056]

[0057] Comparative Example 1

[0058] Comparative Example 1 differs from Example 1 in that the functional filler in Comparative Example 1 is formed into a functional layer in Base Layer 1 using a binder, and the functional layer does not have a microcellular structure.

[0059] Comparative Example 2

[0060] Comparative Example 2 differs from Example 1 in that Comparative Example 2 does not contain Functional Microcellular Layer 2.

[0061] Comparative Example 3

[0062] Comparative Example 3 differs from Example 1 in that Comparative Example 3 does not contain Coating Layer 3.

[0063] Comparative Example 4

[0064] Comparative Example 4 differs from Example 1 in that in Step (3) of Comparative Example 4, the micro-nanoporous film is not first heat-pressed and cooled to set the shape, but is directly coated with Functional Coating Layer 3 on the surface of Functional Microcellular Layer 2.

[0065] Comparative Example 5

[0066] Comparative Example 5 differs from Example 1 in that the composite film obtained in Step 1) is not subjected to the impregnation of supercritical CO2 fluid in Step 2).

[0067] Performance Test

[0068] The composite films of Examples 1-9 and Comparative Examples 1-5 were tested for the type of microcellular elastomer, the composite structure, the average cell size, the porosity, and the solar reflectivity, and the test results are shown in Table 2, with the test methods as follows:

[0069] Porosity: tested by the drainage method, with the standard being HG / T 2872-2009.

[0070] Average Cell Size: the cross-section of the foamed sample was tested by SEM, and the average value of the size of more than 100 cells was counted.

[0071] Reflectivity: determined according to the ball integration method of LAMBDA 950 ultraviolet-visible spectrophotometer, with the standard being JG / T 235-2014.

[0072] Emissivity: determined according to the ball integration test method of Nicolet iS50 Fourier transform infrared spectrometer, with the standard being JG / T 235-2014.

[0073] Table 2: Test Data of Each Group

[0074]

[0075]

[0076] As shown in Table 2, the micro-nano porous membranes in the radiation cooling micro-porous elastomer composite films in Examples 1-9 all have micro-nano porous structures, which have the advantages of light weight, softness and long service life, and the functional micro-porous layer 2 is formed by foaming the functional filler with the elastomer, so that the functional filler can be embedded in the micro-porous structure, and the functional filler can further improve the cooling effect. Since the functional filler is compounded without the need for additional adhesive, the functional filler is not prone to peeling during use, and has the advantage of long service life. Then the functional micro-porous layer 2 is attached with a waterproof coating 3, which can impart water and corrosion resistance to the micro-nano porous membrane. The radiation cooling micro-porous elastomer composite film has a light reflectivity of up to 88% in the 8-13 μm wave band, and a maximum of 93%, which shows that the radiation cooling composite film of the present application helps a large amount of infrared absorption and emission in the atmospheric window, and at the same time, the pore size distribution of the micro-porous elastomer composite film is between 0.3-200 μm and far away from the mid-infrared wave band, which can effectively realize high visible light reflectivity.

[0077] The functional filler in Comparative Example 1 is used to form a functional layer in the base layer 1 using an adhesive. The functional layer does not have a micro-porous structure, and its visible light reflectivity and emissivity are lower than those of Example 1, which shows that embedding the functional filler in the micro-porous structure not only has a bonding effect, but also improves the visible light reflectivity and emissivity, thereby improving the radiation cooling performance of the product.

[0078] Comparative Example 2 does not contain a functional micro-porous layer 2, and its visible light reflectivity and emissivity are much lower than those of Example 1, which shows that the functional micro-porous layer 2 has the advantages of micro-porous structure and functional filler in radiation cooling.

[0079] Comparative Example 3 does not contain a waterproof coating 3, and the waterproof coating 3 has little effect on the visible light reflectivity and emissivity of the composite film, so the waterproof coating 3 mainly has the effects of water resistance and corrosion resistance.

[0080] In Comparative Example 4, the functional micro-porous layer 2 on the micro-nano porous membrane is not first subjected to hot pressing and cooling to set the shape, but a waterproof coating 3 is directly coated on the surface of the functional micro-porous layer 2, so that the pore size and thickness of the micro-porous elastomer composite film are significantly higher than those of Example 1, which shows that hot pressing / cooling setting can cause the micro-nano porous elastomer film 1 to change in thickness to a certain extent, and the thickness of the micro-porous elastomer composite film can be controlled. Pore sizes exceeding 1 μm will affect the reflectivity and emissivity of the radiation cooling composite film in the 8-13 μm wavelength range, thereby reducing the radiation cooling effect of the product.

[0081] The composite film of Comparative Example 5 is not impregnated with supercritical fluid in step 2) in the foaming treatment, i.e. only induced foaming by temperature increase, resulting in the pore size of the elastic film after foaming increasing, thus causing the visible light reflectivity greatly decreasing, which shows that the pore size of the micro-nano-porous film greatly influences the visible light reflectivity and emissivity, and the twice foaming can control the pore size of the micro-nano-porous film in 0.3-1.0 μm, thus obtaining the best radiation cooling effect.

[0082] In summary, the micro-nano-porous film of the radiation cooling elastic composite film of the present application has micro-nano-cellular structure, and has the advantages of light weight, softness and long service life, and can also cause strong Rayleigh scattering and Mie scattering when the composite film is irradiated by sunlight, thus scattering the sunlight to the environment, greatly avoiding heat absorption, thus achieving the passive radiation cooling effect. The functional micro-porous layer 2 is formed by the functional filler being compounded and foamed with the elastomer, so that the functional filler can be embedded in the micro-porous structure, without the need of using additional adhesive, thus the functional filler is not easy to peel off during use, and has the advantage of long service life. Then, a coating layer with different functions is attached to the functional micro-porous layer, which can further improve the cooling effect. The radiation cooling composite film of the present application is soft and light in weight, and can be applied to the passive cooling field in summer outdoors, such as buildings, automobiles, clothes, tents, etc.

[0083] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present application, and are not intended to limit the protection scope of the present application. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present application.

Claims

1. A radiative cooling microporous elastomeric composite film, characterized in that, The micro-nano-porous membrane and the waterproof coating arranged on the micro-nano-porous membrane, the micro-nano-porous membrane has a micro-nano-cell structure; the micro-nano-porous membrane comprises a base layer and at least one functional microporous layer arranged on the base layer in sequence; wherein the base layer is prepared from an elastomer; the functional microporous layer is prepared from an elastomer and a functional filler; The preparation method of the radiation cooling microporous elastomer composite membrane comprises the following steps: (1) preparing the elastomer and the combination of the elastomer and the functional filler into a composite membrane respectively; (2) performing foaming treatment on the composite membrane to obtain a micro-nano-porous membrane with a micro-nano-cell structure, the micro-nano-porous membrane comprises the base layer and at least one functional microporous layer attached to the base layer; the foaming treatment comprises the following steps: first, immersing the composite membrane in a supercritical fluid for the first foaming, then continuing to heat for the second foaming to obtain the micro-nano-porous membrane with the micro-nano-cell structure; (3) performing hot pressing and cooling setting on the micro-nano-porous membrane, then compounding the coating on the surface of the functional microporous layer to obtain the radiation cooling microporous elastomer composite membrane.

2. The radiative cooling microcellular elastomeric composite film of claim 1, wherein, The micro-nano-porous membrane comprises the following raw materials by weight: 70-100 parts of the elastomer, 5-20 parts of the functional filler, 2-3 parts of the lubricant, 0.2-1 part of the crosslinking agent and 0.1-0.5 part of the antioxidant.

3. The radiative cooling microcellular elastomeric composite film according to claim 1 or 2, wherein, The elastomer in the preparation raw materials of the functional microporous layer and the micro-nano-porous membrane layer is at least one of polyurethane thermoplastic elastomer, polyester thermoplastic polyester elastomer, nylon elastomer, EVA crosslinked elastomer, polyolefin crosslinked elastomer, styrene crosslinked elastomer and vulcanized rubber.

4. The radiative cooling microcellular elastomeric composite film of claim 1, wherein, The functional filler is at least one of silicon dioxide, chromium dioxide, titanium dioxide, silicon nitride, aluminum phosphate and aluminum oxide; the particle size of the functional filler is 0.05-10 μm.

5. The radiative cooling microcellular elastomeric composite film of claim 1, wherein, The preparation raw materials of the waterproof coating comprise at least one of γ-methacryloxypropyltrimethoxysilane, N-methyl perfluorooctyl sulfonamide acrylate and methyl methacrylate.

6. The radiative cooling microcellular elastomeric composite film of claim 1, wherein, The average cell size of the micro-nano-porous membrane is 0.3-200 μm, and the porosity is 60-97%.

7. The radiative cooling microcellular elastomeric composite film of claim 1, wherein, One of the following (I)-(II): (I) in the step (1), the preparation steps of the composite membrane in sequence comprise mixing the preparation raw materials of the base layer and the functional microporous layer respectively, co-extruding a double-screw extruder, rolling, cooling and obtaining the composite membrane; (II) in the step (1), the preparation steps of the composite membrane in sequence comprise: first, preparing the base layer and the functional microporous layer into a film, then, layering the obtained film, and finally, vulcanizing to obtain the composite membrane; wherein the film forming temperature is 90-130 ℃, and the vulcanization temperature is 160-190 ℃.

8. The radiative cooling microcellular elastomeric composite film of claim 1, wherein, In the step (3), the hot pressing temperature is 130-160 ℃, and the cooling temperature is 4-15 ℃.

9. The radiation cooling microporous elastomer composite membrane according to any one of claims 1-8 is applied in the preparation of building outer walls, automobile interiors, clothing, tents.

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