Dual-layer structure radiative cooling film and preparation method thereof

Abstract

The application discloses a kind of double-layer structure radiation refrigeration film and preparation method thereof, it includes the following steps: polydimethylsiloxane prepolymer, curing agent and organic solvent are mixed uniformly according to proportion, obtain mixed solution, wherein the proportion of curing agent is 3-20 wt% of polydimethylsiloxane prepolymer, the amount of organic solvent is 0-50 wt%;Coating mixed solution is on polyethylene nanofiber, and dry into film, obtain double-layer structure radiation refrigeration film.The application preparation process is simple, raw material and production cost are low, and easy to carry out macro preparation.Simultaneously the polyethylene nanofiber layer of the application can be high reflection sunlight, polydimethylsiloxane layer can be high emission infrared light, the synergies of polydimethylsiloxane layer and polyethylene nanofiber layer double-layer structure, can make double-layer structure radiation refrigeration film almost not absorb sunlight, and can emit infrared heat in large quantities.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of radiation refrigeration, and in particular to a double-layer structure radiation refrigeration film and a preparation method thereof. BACKGROUND

[0002] In recent years, influenced by global warming, record high temperatures have been frequently set around the world. The rising earth temperature has led to an unprecedented surge in refrigeration demand in various countries. However, the traditional air compression-based refrigeration technology faces a series of problems, such as serious power consumption, causing "net" temperature rise, and exacerbating global warming. Therefore, the exploration of environment-friendly and carbon-reducing cooling technologies is urgent. Radiation refrigeration technology is based on the principle of transmitting specific wavelength heat-carrying infrared radiation through the atmospheric transparent window to the cold outer space, and has the advantages of zero pollution and zero carbon source, and is expected to reduce or replace traditional electric refrigeration systems, and has attracted much attention in recent years. However, the preparation of large-scale, aging-resistant and low-cost radiation refrigeration materials is still a great challenge. SUMMARY

[0003] To solve the above technical problems, the present application provides a double-layer structure radiation refrigeration film and a preparation method thereof. The specific technical solutions are as follows:

[0004] To solve the above technical problems, the present application is implemented as follows:

[0005] In a first aspect, a preparation method of a double-layer structure radiation refrigeration film is provided, which includes the following steps: uniformly mixing polydimethylsiloxane prepolymer, a curing agent and an organic solvent in proportion to obtain a mixed solution, wherein the proportion of the curing agent to the polydimethylsiloxane prepolymer is 3-20 wt%, and the amount of the organic solvent is 0-50 wt%; coating the mixed solution on polyethylene nanofibers and drying into a film to obtain the double-layer structure radiation refrigeration film.

[0006] In a first possible implementation manner of the first aspect, the curing agent uses a transparent silicone curing agent.

[0007] In a second possible implementation manner of the first aspect, the organic solvent includes at least one of toluene, tetrahydrofuran and chloroform.

[0008] In a third possible implementation manner of the first aspect, mechanical stirring, magnetic stirring, homogenizing stirring or ultrasonic stirring is used to stir the mixed solution of the polydimethylsiloxane prepolymer, the curing agent and the organic solvent.

[0009] In a fourth possible implementation manner of the first aspect, a spraying, pouring, roller coating or spin coating method is used to coat the mixed solution on the polyethylene nanofibers.

[0010] In a fifth possible implementation manner of the first aspect, the drying temperature is 80°C, and the drying time is 2h.

[0011] In a sixth possible implementation manner of the first aspect, the average solar reflectivity of the double-layer structure radiative cooling film is ≥ 0.90, and the long-wave infrared emissivity is ≥ 0.90.

[0012] In a seventh possible implementation manner of the first aspect, under the direct sunlight at noon, the temperature of the double-layer structure radiative cooling film can be 2-5°C lower than the ambient temperature.

[0013] In a second aspect, a double-layer structure radiative cooling film prepared by the preparation method in any one of the first aspect is provided, which includes a polydimethylsiloxane layer and a polyethylene nanofiber layer. The polyethylene nanofiber layer has a micro-nano porous structure, and the polyethylene nanofiber layer can highly reflect sunlight. The polydimethylsiloxane layer is arranged on the polyethylene nanofiber layer, and the polydimethylsiloxane layer has multiple extinction peaks at the atmospheric transparent window of 8-13 µm, and can highly emit infrared light.

[0014] In a first possible implementation manner of the second aspect, the pore size distribution range of the polyethylene nanofiber layer is 50-200nm, and the thickness is 20-200 µm.

[0015] In the embodiment of the present application, the double-layer structure radiative cooling film is prepared by the polydimethylsiloxane and the polyethylene nanofiber, the preparation process is simple, the raw materials and production cost are low, and it is easy to carry out macro preparation. The polyethylene nanofiber layer can highly reflect sunlight, the polydimethylsiloxane layer can highly emit infrared light, and the synergistic effect of the double-layer structure of the polydimethylsiloxane layer and the polyethylene nanofiber layer can make the double-layer structure radiative cooling film hardly absorb sunlight, and can emit a large amount of infrared heat. BRIEF DESCRIPTION OF DRAWINGS

[0016] The accompanying drawings, which are included to provide a further understanding of the present application and are incorporated in and constitute a part of this application, illustrate embodiments of the present application and serve to explain the present application. In the drawings:

[0017] Figure 1 is a step flow chart of the preparation method of the double-layer structure radiative cooling film of an embodiment of the present application;

[0018] Figure 2 is a schematic diagram of the PDMS / nanoPE radiative cooling film and an electron micrograph of the nanoPE micro-morphology in embodiment 1 of the present application;

[0019] Figure 3is the reflectance spectrum and emission spectrum of the PDMS / nanoPE radiative cooling film in Example 1 of the present application at a wavelength of 0.3-20 pm;

[0020] Figure 4 is the temperature curve of the PDMS / nanoPE radiative cooling film in Example 1 of the present application under direct sunlight at noon. DETAILED DESCRIPTION

[0021] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of the present application.

[0022] Please refer to Figure 1 , which is a step flow chart of the preparation method of the double-layer structure radiative cooling film according to an embodiment of the present application. As shown in the figure, the preparation method of the double-layer structure radiative cooling film includes steps S1 and S2. First, in step S1, polydimethylsiloxane (PDMS) prepolymer, a curing agent, and an organic solvent are mixed uniformly in proportion to obtain a mixed solution. Specifically, the mixed solution of the polydimethylsiloxane prepolymer, the curing agent, and the organic solvent can be stirred by mechanical stirring, magnetic stirring, homogenizing stirring, or ultrasonic stirring. The proportion of the curing agent to the polydimethylsiloxane prepolymer is 3-20 wt%, and the amount of the organic solvent is 0-50 wt%. The curing agent can be a transparent silicone curing agent, such as SYLGARD 184, and the organic solvent includes at least one of toluene, tetrahydrofuran, and chloroform.

[0023] Then, in step S2, the mixed solution is coated on polyethylene (PE) nanofibers and dried into a film to obtain a double-layer structure radiative cooling film. Specifically, the mixed solution can be coated on the polyethylene nanofibers by spraying, pouring, roller coating, or spin coating. The drying temperature is 80°C, and the drying time is 2h. The average solar reflectance of the double-layer structure radiative cooling film prepared above is ≥ 0.90, and the long-wave infrared emissivity is ≥ 0.90. Under direct sunlight at noon, the temperature of the double-layer structure radiative cooling film itself can be 2-5°C lower than the ambient temperature.

[0024] The preparation method in this embodiment first prepares a polydimethylsiloxane (PDMS) mixed solution, then coats the polydimethylsiloxane (PDMS) mixed solution on polyethylene nanofibers and dries it to form a double-layer structure radiative cooling film of polydimethylsiloxane and polyethylene nanofibers. The preparation process in this embodiment is simple, the raw materials and production cost are low, and it is easy to perform macro-preparation.

[0025] Referring to Figure 2 , which is a schematic diagram of a double-layer structure radiation cooling film according to an embodiment of the present application; as shown in the figure, the double-layer structure radiation cooling film comprises a polydimethylsiloxane layer and a polyethylene nanofiber layer. The polyethylene nanofiber layer has a micro-nano porous structure, and the polyethylene nanofiber layer can highly reflect sunlight. The polydimethylsiloxane layer is arranged on the polyethylene nanofiber layer, and the polydimethylsiloxane layer has a plurality of extinction peaks at the atmospheric transparent window of 8-13 μm, and can highly emit infrared light. The pore size distribution range of the polyethylene nanofiber layer is 50-200 nm, and the thickness is 20-200 μm.

[0026] The polyethylene nanofiber layer in the double-layer structure radiation cooling film of the present embodiment highly reflects sunlight, the polydimethylsiloxane layer highly emits infrared light, and the synergistic effect of the polydimethylsiloxane layer and the polyethylene nanofiber layer can make the double-layer structure radiation cooling film hardly absorb sunlight and emit a large amount of infrared heat. The double-layer structure radiation cooling film of the present embodiment has better cooling effect and has potential application value in clothes, car covers and building roofs.

[0027] The beneficial effects of the double-layer structure radiation cooling film and the preparation method thereof according to the present application will be described in specific embodiments below.

[0028] Embodiment 1

[0029] 1. First, 5 g of polydimethylsiloxane prepolymer and 0.5 g of curing agent (SYLGARD 184) were weighed into 3 mL of toluene solvent and stirred uniformly to obtain a PDMS mixed solution. Then, the prepared PDMS mixed solution was dropped on a polyethylene nanofiber with a thickness of about 150 μm, and a spin coater was used to spin coat at a speed of 2000 r / s for 40 s, and then it was placed in a 80 ℃ air blowing box for drying, and after 2 h, the PDMS / nanoPE radiation cooling film (double-layer structure radiation cooling film) was obtained, as shown in Figure 2 , which is a schematic diagram of the PDMS / nanoPE radiation cooling film and an electron micrograph of the nanoPE microstructure in Embodiment 1 of the present application, and it can be seen that the nanoPE has a rich micro-nano porous structure inside.

[0030] As shown in Figure 3 , which is the reflectance spectrum and emission spectrum of the PDMS / nanoPE radiation cooling film in Embodiment 1 of the present application at a wavelength of 0.3-20 μm, it can be seen that the average solar reflectivity and long-wave infrared emissivity of the PDMS / nanoPE radiation cooling film are as high as 0.94, indicating that it hardly absorbs sunlight and emits a large amount of infrared light through the atmospheric transparent window.

[0031] As shown in Figure 4As shown, it is the temperature curve of the PDMS / nanoPE radiation cooling film in Example 1 of the present application under the direct sunlight at noon, and it can be seen that the temperature of the PDMS / nanoPE film is always lower than the ambient temperature under the direct sunlight at noon, and the average cooling is about 4.5℃.

[0032] Example 2

[0033] First, 5g of polydimethylsiloxane prepolymer and 1g of curing agent (SYLGARD 184) were weighed and stirred uniformly in 5mL of chloroform solvent to obtain a PDMS mixed solution. Then, the prepared PDMS mixed solution was dropped on the polyethylene nanofiber with a thickness of about 100µm, and uniformly scraped by an automatic film coating machine. After the solution was naturally leveled, it was placed in a 80℃ air blowing box for drying, and taken out after 2h to obtain the PDMS / nanoPE radiation cooling film.

[0034] In summary, the present application provides a double-layer structure radiation cooling film and a preparation method thereof. The present application prepares a double-layer structure radiation cooling film by polydimethylsiloxane and polyethylene nanofiber, which has simple preparation process, low raw material and production cost, and is easy to prepare in large quantities. The polyethylene nanofiber layer can highly reflect sunlight, the polydimethylsiloxane layer can highly emit infrared light, and the synergistic effect of the double-layer structure of the polydimethylsiloxane layer and the polyethylene nanofiber layer can make the double-layer structure radiation cooling film hardly absorb sunlight and emit a large amount of infrared heat.

[0035] It should be noted that in this document, the terms "comprising", "containing", or any other variant thereof are intended to cover non-exclusive inclusions, so that a process, method, article or apparatus that includes a series of elements not only includes those elements, but also includes other elements not explicitly listed, or inherent to such a process, method, article or apparatus. Without more limitations, the element defined by the statement "comprising a" does not exclude the presence of other identical elements in the process, method, article or apparatus that includes the element.

[0036] The embodiments of the present application are described above in conjunction with the drawings, but the present application is not limited to the above specific embodiments, and the above specific embodiments are only illustrative, not restrictive, and those skilled in the art can make many forms under the inspiration of the present application without departing from the purpose of the present application and the scope protected by the claims.

Claims

1. A method for preparing a dual-layer structure radiative cooling film, characterized in that, The method comprises the following steps: mixing a polydimethylsiloxane prepolymer, a curing agent and an organic solvent in proportion to obtain a mixed solution, wherein the proportion of the curing agent to the polydimethylsiloxane prepolymer is 3-20 wt%, the amount of the organic solvent is 0-50 wt% and is not 0, the organic solvent comprises at least one of toluene, tetrahydrofuran and chloroform, and the curing agent is a transparent silica gel curing agent; coating the mixed solution on a polyethylene nanofiber layer and drying into a film at a drying temperature of 80°C for 2 h to obtain a double-layer structure radiation refrigeration film, wherein the polyethylene nanofiber layer has a micro-nano porous structure, the polyethylene nanofiber layer can highly reflect sunlight, the pore size distribution range of the polyethylene nanofiber layer is 50-200 nm, and the thickness of the polyethylene nanofiber layer is 20-200 μm.

2. The method of claim 1, wherein the dual-layer structure RRF is prepared by a process comprising: The mixed solution of the polydimethylsiloxane prepolymer, the curing agent and the organic solvent is stirred by mechanical stirring, magnetic stirring, homogenizing stirring or ultrasonic stirring.

3. The method of claim 1, wherein the dual-layer structure RRF is prepared by a process comprising: The mixed solution is coated on the polyethylene nanofiber layer by a spraying, pouring, rolling or spin coating method.

4. A dual-layer radiative cooling film prepared according to the method of any one of claims 1-3, wherein, The method comprises: a polyethylene nanofiber layer having a micro-nano porous structure, the polyethylene nanofiber layer can highly reflect sunlight; a polydimethylsiloxane layer arranged on the polyethylene nanofiber layer, the polydimethylsiloxane layer has a plurality of extinction peaks at an atmospheric transparent window of 8-13 μm and can highly emit infrared light, wherein the average solar reflectance of the double-layer structure radiation refrigeration film is ≥0.90, the long-wave infrared emissivity is ≥0.90, and the temperature of the double-layer structure radiation refrigeration film is 2-5°C lower than the ambient temperature under direct sunlight at noon.

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