Layered gradient porous SMMA radiation cooling film and preparation method and application thereof

Abstract

The invention belongs to the technical field of radiation cooling films, and particularly relates to a layered gradient porous SMMA radiation cooling film and a preparation method and application thereof. The method comprises the following steps: 1) preparing a mixed precursor solution of a styrene dimethyl acrylate copolymer, acetone, tetrahydrofuran and ethanol; 2) pouring the mixed precursor solution onto a smooth substrate, and then standing; and 3) adding ultrapure water to the surface of the mixed precursor solution for soaking, standing and curing, and stripping a film formed by curing from the surface of the substrate. The graded gradient porous polymer is prepared by utilizing a multi-stage solvent replacement method. The provided SMMA film is attached to the surface of a lighting material such as glass, sunlight can be reflected, infrared heat radiation is radiated to cold outer space through an atmosphere window of 8-13 microns, and therefore indoor heat and temperature regulation and control of a building are achieved, and the purpose of saving energy is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of radiation cooling films, and in particular relates to a layered gradient porous SMMA radiation cooling film and a preparation method and application thereof. Background Art

[0002] Refrigeration accounts for 20% of global electricity consumption and is especially necessary in hot weather. However, the use of large numbers of air conditioning systems will significantly increase global energy consumption, thereby accelerating global warming and climate change. Passive daytime radiative cooling (PDRC) is a promising alternative strategy to traditional cooling that can help mitigate global warming. PDRC is mainly achieved by spectrally selective materials that simultaneously reflect sunlight (0.3-2.5μm) and radiate infrared thermal radiation to the cold outer space (3K) through the atmospheric window between 8 and 13μm. Therefore, high solar reflectance (R solar ,λ~0.3-2.5μm) and high infrared thermal emissivity (ε IR ,λ~8-13μm) is the key point in designing efficient PDRC materials. solar and high ε IR Various PDRC structures and materials have been developed, including multilayer photonic structures, particle distribution structures, porous structures, metamaterials, biomaterials, and biomimetic materials. However, most reported PDRC structures have difficulty in achieving an optimal balance between structural design and processing costs, which will hinder the large-scale commercial application of efficient PDRC materials. Therefore, a simple, cost-effective and efficient PDRC manufacturing method is highly desired for the practical application of radiative cooling technology.

[0003] Styrene dimethyl methacrylate copolymer (SMMA) has clear transparency and combines the properties of materials such as polystyrene (PS), polymethyl methacrylate (PMMA) and styrene-acrylonitrile copolymer (SAN), and is often seen as a substitute for transparent plastic or glass. However, using SMMA to efficiently prepare radiative cooling structures remains a problem. Summary of the invention

[0004] In order to solve the deficiencies of the prior art, the present invention provides a hierarchical gradient porous SMMA radiation cooling film and its preparation method and application. The present invention uses a multi-stage solvent replacement method to prepare a graded gradient porous polymer. Furthermore, the SMMA film provided by the present invention is attached to the surface of a lighting material such as glass, which can reflect sunlight and simultaneously radiate infrared heat radiation to the cold outer space through an atmospheric window between 8 and 13 μm, thereby achieving indoor heat and temperature control in buildings and achieving energy saving.

[0005] The technical solution provided by the present invention is as follows:

[0006] A method for preparing a layered gradient porous SMMA radiation cooling film comprises the following steps:

[0007] 1) preparing a mixed precursor solution of styrene dimethyl methacrylate copolymer, acetone, tetrahydrofuran and ethanol;

[0008] 2) pouring the mixed precursor solution obtained in step 1) onto a smooth substrate and then allowing it to stand;

[0009] 3) adding ultrapure water to the surface of the mixed precursor solution for immersion, allowing it to stand and solidify, and peeling the solidified film from the substrate surface to obtain a layered gradient porous SMMA radiation cooling film.

[0010] The above technical solution uses a multi-stage solvent replacement method to prepare a graded gradient porous polymer. Specifically, in step 3), based on the "driving force principle of forming micro / nanopores during solvent replacement", solvent replacement is performed during the immersion in ultrapure water, and the SMMA deposited in the SMMA (polymer) precursor solution gradually generates gradient micro / nanopores in the film, and finally solidifies during the immersion in ultrapure water. The film is peeled off from the substrate surface to obtain a porous SMMA film.

[0011] The film is bonded to the surface of glass or other lighting materials and assembled into energy-saving windows, which can reflect sunlight (0.3-2.5μm) and simultaneously radiate infrared thermal radiation to the cold outer space (3K) through the atmospheric window between 8 and 13μm.

[0012] Specifically, in step 1), the mass ratio of styrene dimethyl methacrylate copolymer, acetone, tetrahydrofuran and ethanol is 1:(1-5):(1-5):(3-10).

[0013] In the above technical solution, SMMA is a polymer component, acetone is a solvent component, tetrahydrofuran is a solvent component, and ethanol is a non-solvent component.

[0014] Specifically, in step 2), the thickness of the casting liquid is 0.05-1.0 mm, and the size can be 50×50 cm.

[0015] Specifically, in step 2), the standing time is 8-12 minutes. Depending on the area and thickness of the SMMA film, the solution is allowed to stand for tens of minutes to prevent irregular deformation of the sample due to the buoyancy of water during the subsequent immersion process.

[0016] Specifically, in step 3), the curing time is 10-60 minutes.

[0017] In the above technical scheme, since SMMA is insoluble in ethanol, and ethanol, acetone and tetrahydrofuran are mutually soluble, the concentrations of acetone and tetrahydrofuran are reduced by adding ethanol to the precursor solution. Finally, the concentrations of acetone, tetrahydrofuran and ethanol all drop sharply during the water immersion process. The local supersaturation of the hydrophobic SMMA molecules leads to spontaneous nucleation in the form of small structures over time, thereby forming abundant micro / nanopores in the SMMA film. Therefore, during the entire curing process of SMMA, the external traction force that gradually decreases from bottom to top contributes to the formation of graded gradient micro / nanopores in the SMMA film. And the size of the pores can be controlled according to different solution ratios. In this way, a hierarchical gradient porous SMMA radiation cooling film is obtained through the "driving force principle for the formation of micro / nanopores during solvent replacement".

[0018] The molecular weight of the SMMA polymer is usually between several thousand and hundreds of thousands. Preferably, the molecular weight of the SMMA polymer is 12,000 and can be purchased from Aladdin Reagent Company.

[0019] Specifically, in step 3), the curing is performed at room temperature.

[0020] Specifically, the smooth substrate is selected from glass, polished silicon wafer or stainless steel sheet, and the preferred smooth substrate is glass.

[0021] The present invention also provides a layered gradient porous SMMA radiation cooling film prepared according to the above preparation method.

[0022] The gradient micro / nanopore structure of the layered gradient porous SMMA radiation cooling film provided by the present invention has a wide distribution of pore sizes at the bottom layer, which is concentrated around 0-3.0 μm, and can effectively scatter sunlight. Nanopores with a size of less than 1.0 μm will further increase R solar , which enhances the scattering of shorter and visible wavelengths. The hemispherical spectral reflectance of the porous SMMA film exhibits an ultra-high solar reflectivity R solar =0.98. At the same time, the SMMA film has an ultra-high thermal emissivity of 0.96 in the atmospheric transparent window (8-13μm), thereby ensuring that infrared radiation passes through the atmospheric window to the cold outer space to achieve radiation cooling.

[0023] The present invention also provides an application of a layered gradient porous SMMA radiation cooling film for preparing a radiation cooling structural part.

[0024] Specifically, the layered gradient porous SMMA radiation cooling film is bonded and fixed to a smooth substrate with glue to obtain a radiation cooling structure.

[0025] In the above technical solution, the bonding glue can be made of a material having physical and chemical properties close to those of glass and SMMA, and preferably SMMA prepolymer can be used.

[0026] Compared with the prior art, the technical solution of the present invention can achieve the following beneficial effects:

[0027] 1) The provided SMMA film has a layered gradient porous structure, in which the pore size gradually decreases from the bottom layer to the top layer. When the bottom layer of the SMMA film directly faces the sun, this structure can simultaneously achieve high R solar and ε IR The bottom layer has a wide distribution of pore sizes, concentrated around 0 to 3.0 μm, which can effectively scatter sunlight.

[0028] 2) In the provided SMMA film, nanopores with a size less than 1.0 μm will further improve R solar , which enhances the scattering of shorter and visible wavelengths. The porous SMMA film exhibits an ultra-high solar reflectivity R in the hemispherical spectral reflectivity. solar =0.98. At the same time, the SMMA film has an ultra-high thermal emissivity of 0.96 in the atmospheric transparent window (8-13μm), thereby ensuring that infrared radiation passes through the atmospheric window to the cold outer space to achieve radiation cooling.

[0029] 3) The provided preparation method is a simple, cost-effective and efficient PDRC manufacturing method, which is conducive to the practical application of radiation cooling technology.

[0030] 4) The prepared polymer film can realize indoor heat and temperature regulation of buildings, achieving the purpose of energy saving. DETAILED DESCRIPTION

[0031] The principles and features of the present invention are described below. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0032] Unless otherwise specified, the test methods used in the embodiments of the present invention are all conventional methods; the materials, reagents, etc. used are reagents and materials that can be obtained from commercial channels unless otherwise specified.

[0033] Example 1

[0034] The preparation method of the layered gradient porous SMMA radiation cooling film specifically comprises the following steps:

[0035] 1) preparing a mixed precursor solution of styrene dimethyl methacrylate copolymer, acetone, tetrahydrofuran and ethanol;

[0036] 2) pouring the mixed precursor solution obtained in step 1) onto a smooth substrate and then allowing it to stand;

[0037] 3) adding ultrapure water to the surface of the mixed precursor solution for immersion, allowing it to stand and solidify, and peeling the solidified film from the substrate surface to obtain a layered gradient porous SMMA radiation cooling film.

[0038] In step 1), the mass ratio of styrene dimethyl methacrylate copolymer, acetone, tetrahydrofuran and ethanol is 1:3:3:7.

[0039] In step 2), the thickness of the casting liquid is 0.6 mm and the area is 50×50 cm.

[0040] In step 2), the standing time is 10 min.

[0041] In step 3), the curing time is 30 minutes.

[0042] The whole process was carried out at room temperature.

[0043] The obtained layered gradient porous SMMA radiation cooling film was tested for solar reflectivity and thermal emissivity in the atmospheric transparent window, and the results are as follows:

[0044] Solar reflectivity R solar =0.98.

[0045] The thermal emissivity in the atmospheric transparent window is 0.96.

[0046] Example 2

[0047] The preparation method of the layered gradient porous SMMA radiation cooling film specifically comprises the following steps:

[0048] 1) preparing a mixed precursor solution of styrene dimethyl methacrylate copolymer, acetone, tetrahydrofuran and ethanol;

[0049] 2) pouring the mixed precursor solution obtained in step 1) onto a smooth substrate and then allowing it to stand;

[0050] 3) adding ultrapure water to the surface of the mixed precursor solution for immersion, allowing it to stand and solidify, and peeling the solidified film from the substrate surface to obtain a layered gradient porous SMMA radiation cooling film.

[0051] In step 1), the mass ratio of styrene dimethyl methacrylate copolymer, acetone, tetrahydrofuran and ethanol is 1:3:3:7.

[0052] In step 2), the thickness of the casting liquid is 0.2 mm and the area is 50×50 cm.

[0053] In step 2), the standing time is 10 min.

[0054] In step 3), the curing time is 30 minutes.

[0055] The whole process was carried out at room temperature.

[0056] The obtained layered gradient porous SMMA radiation cooling film was tested for solar reflectivity and thermal emissivity in the atmospheric transparent window, and the results are as follows:

[0057] Solar reflectivity R solar =0.96.

[0058] The thermal emissivity in the atmospheric transparent window is 0.95.

[0059] Example 3

[0060] The preparation method of the layered gradient porous SMMA radiation cooling film specifically comprises the following steps:

[0061] 1) preparing a mixed precursor solution of styrene dimethyl methacrylate copolymer, acetone, tetrahydrofuran and ethanol;

[0062] 2) pouring the mixed precursor solution obtained in step 1) onto a smooth substrate and then allowing it to stand;

[0063] 3) adding ultrapure water to the surface of the mixed precursor solution for immersion, allowing it to stand and solidify, and peeling the solidified film from the substrate surface to obtain a layered gradient porous SMMA radiation cooling film.

[0064] In step 1), the mass ratio of styrene dimethyl methacrylate copolymer, acetone, tetrahydrofuran and ethanol is 1:1:1:4.

[0065] In step 2), the thickness of the casting liquid is 0.6 mm and the area is 50×50 cm.

[0066] In step 2), the standing time is 10 min.

[0067] In step 3), the curing time is 30 minutes.

[0068] The whole process was carried out at room temperature.

[0069] The obtained layered gradient porous SMMA radiation cooling film was tested for solar reflectivity and thermal emissivity in the atmospheric transparent window, and the results are as follows:

[0070] Solar reflectivity R solar =0.96.

[0071] The thermal emissivity in the atmospheric transparent window is 0.93.

[0072] Comparative Example 1

[0073] Refer to Example 1, the difference is that the styrene dimethyl methacrylate copolymer is replaced by PMMA with a molecular weight of 12000, and the other experimental parameters are the same as Example 1.

[0074] The test results are as follows:

[0075] Solar reflectivity R solar =0.92.

[0076] The thermal emissivity in the atmospheric transparent window is 0.94.

[0077] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a layered gradient porous SMMA radiation cooling film, characterized in that: The following steps are involved: 1) preparing a mixed precursor solution of styrene dimethyl methacrylate copolymer, acetone, tetrahydrofuran and ethanol; 2) pouring the mixed precursor solution obtained in step 1) onto a smooth substrate and then allowing it to stand; 3) adding ultrapure water to the surface of the mixed precursor solution for immersion, allowing it to stand and solidify, and peeling the solidified film from the substrate surface to obtain a layered gradient porous SMMA radiation cooling film.

2. The method for preparing the layered gradient porous SMMA radiation cooling film according to claim 1, characterized in that: In step 1), the mass ratio of styrene dimethyl methacrylate copolymer, acetone, tetrahydrofuran and ethanol is 1:(1-5):(1-5):(3-10).

3. The method for preparing the layered gradient porous SMMA radiation cooling film according to claim 1, characterized in that: In step 2), the thickness of the casting liquid is 0.05-1.0 mm.

4. The method for preparing the layered gradient porous SMMA radiation cooling film according to claim 3, characterized in that: In step 2), the standing time is 8-12 minutes.

5. The method for preparing the layered gradient porous SMMA radiation cooling film according to claim 1, characterized in that: In step 3), the curing time is 10-60 minutes.

6. The method for preparing the layered gradient porous SMMA radiation cooling film according to claim 1, characterized in that: In step 3), the curing is carried out at room temperature.

7. The method for preparing the layered gradient porous SMMA radiation cooling film according to any one of claims 1 to 6, characterized in that: The smooth substrate is selected from glass, polished silicon wafer or stainless steel wafer.

8. A layered gradient porous SMMA radiation cooling film prepared according to the preparation method according to any one of claims 1 to 7.

9. An application of the layered gradient porous SMMA radiation cooling film according to claim 8, characterized in that: Used to prepare radiation cooling structures.

10. The use according to claim 9, characterized in that: The layered gradient porous SMMA radiation cooling film is bonded and fixed to a smooth substrate by glue to obtain a radiation cooling structure.