A thermal management film integrating dual functions of radiative cooling and heating and a preparation method thereof

Abstract

This invention belongs to the field of passive radiative cooling materials, specifically relating to a thermal management film that integrates both radiative cooling and heating functions, and its preparation method. It is characterized by preparing a black PPY modified cotton as the heating surface and a white PMMA / NaH2PO2 composite film as the cooling surface, which are then combined by coating and drying to produce a double-sided thermal management film capable of both heating and cooling. This invention addresses the difficulty people have in regulating their temperature in hot or cold environments. The entire temperature regulation process is environmentally friendly and energy-saving, and the preparation method is simple, making it suitable for large-scale production.

Description

Technical Field

[0001] The present invention belongs to the field of passive radiation cooling materials, and in particular relates to a film that integrates radiation cooling and heating functions and can realize personal thermal management, and a preparation method thereof. Background Art

[0002] The normal functioning of the human body's entire life system depends on a relatively constant body temperature. When the ambient temperature rises or falls dramatically, the body's thermoregulatory system struggles to maintain normal operation. Indoors, the ambient temperature can typically be controlled through air conditioners, heaters, fans, and other devices. However, this method of temperature control consumes significant energy, exacerbating the global energy crisis and emitting significant amounts of greenhouse gases. Outdoors, people can only manage their body temperature through external media such as clothing.

[0003] With advances in materials science and the rapid development of textile technology, materials and fabrics for human body temperature control have been reported, such as electric cooling and infrared radiation materials. Radiative cooling refers to a method in which materials achieve cooling by radiating heat through Earth's "atmospheric window" into the cold outer space through their high reflection of sunlight in the 0.3-2.5μm band and high emission in the 8-13μm mid-infrared band. Compared to traditional cooling methods, radiative cooling requires no external energy and does not pollute the environment, making it a green and environmentally friendly passive cooling method. For example, in the patent "A Radiative Cooling Fabric" (Publication No.: CN113136724A), a high-refractive-index material attached to the fibers increases ultraviolet reflectivity by 42%, bringing the reflectivity across the entire solar wavelength range to 95%. The treated fabric can maintain a temperature approximately 3.6°C lower than room temperature in sunlight. Furthermore, photothermal conversion materials are novel functional materials that utilize their inherent optical properties to absorb solar radiation and convert it into heat. They have wide applications in wearable fabrics, biomedicine, building temperature control, and other fields. For example, the patent "Preparation Method and Materials of Wearable Membrane Materials with Triple Thermal Insulation Functions" (Publication No.: CN112341656A) uses biomass cellulose, core-shell nickel / silver nanowires, and boron nitride nanosheets as raw materials, and prepares a wearable membrane material with triple thermal insulation functions through vacuum filtration. The method is simple and environmentally friendly, with the characteristics of energy conservation and emission reduction. However, the human body thermal management materials reported so far still face many problems and challenges, such as a single temperature control mechanism, low efficiency, and poor thermal integration.

[0004] In summary, current smart wearable fabrics have yet to achieve precise human thermal management through functional and structural integration. Therefore, we need to seek a thin film that combines the dual functions of radiative cooling and heating to achieve personal thermal management, as well as a method for its preparation. Summary of the Invention

[0005] Purpose of the invention: The purpose of the invention is to provide a thermal management film that integrates the dual functions of radiation cooling and heating and a preparation method thereof, which not only solves the current problem that individuals have difficulty in achieving immediate human body temperature regulation in excessively hot or cold outdoor environments, but also solves the problem that traditional temperature control methods have a single function and huge energy consumption.

[0006] The technical solution of the present invention is to first modify cotton fabric with PPY (polypyrrole) to form black PPY-modified cotton. A white PMMA (polymethyl methacrylate) / NaH2PO2 (sodium hypophosphite) composite film is then prepared at room temperature using a static method. This composite film is then composited with the PPY-modified cotton to create a film that combines radiant cooling and heating functions for personal thermal management. The specific preparation steps are as follows:

[0007] (1) The cotton fabric was first washed with acetone, then washed with ethanol, and dried. It was then immersed in a solution of ferric chloride hexahydrate (FeCl3·6H2O), then immersed in a pyrrole solution, washed with deionized water, and finally dried in an oven to obtain black PPY-modified cotton.

[0008] (2) A certain amount of NaH2PO2 particles was stirred in DMF (N,N-dimethylformamide) to completely disperse them. Then, a certain amount of PMMA was added to the mixed solution and stirred. After stirring, the dispersion was coated on the prepared PPY modified cotton. After the solvent was completely evaporated, a double-sided thermal management film was obtained.

[0009] Furthermore, the concentration of the FeCl3·6H2O solution used to prepare the PPY modified cotton in step (1) is 2 mol / L, and the soaking time is 1 h.

[0010] Furthermore, the soaking time in the pyrrole solution in step (1) is 6 hours.

[0011] Furthermore, the drying temperature in step (1) is 60° C. and the drying time is 2 h.

[0012] Furthermore, in step (2), the stirring time of the NaH2PO2 particles in DMF is 1 h.

[0013] Furthermore, in step (2), the stirring temperature of PMMA in the mixed solution is 35° C., and the stirring time is 4 h.

[0014] Furthermore, in the mixed dispersion prepared in step (2), the mass ratio of PMMA to NaH2PO2 is 10:3, and the mass ratio of PMMA to DMF is 1:6.

[0015] The present invention discloses a film that integrates the dual functions of radiative cooling and heating and can achieve personal thermal management, and its preparation method, which solves the problem that people find it difficult to regulate their own temperature in hot or cold outdoor environments. The film includes a white cooling surface and a black heating surface. When the ambient temperature is high, the white PMMA / NaH2PO2 composite film faces outward, thereby achieving radiative cooling of the human body; when the ambient temperature is low, the black PPY modified cotton faces outward, and the photothermal conversion characteristics of the functional material are used to achieve heat preservation and heating of the human body. This invention does not require the consumption of external energy, and personal temperature regulation can be achieved by simply adjusting the front and back of the wearer. The preparation method is simple and suitable for large-scale production.

[0016] Beneficial effects

[0017] 1. The present invention provides a film that integrates the dual functions of radiation cooling and heating and can achieve personal thermal management and its preparation method

[0018] 2. Excellent performance: The average solar reflectivity of the cooling surface in the 0.3-2.5μm band is as high as 93%, the average mid-infrared emissivity in the 8-13μm atmospheric window band is as high as 98%, the absorptivity of the heating surface in the 0.3-2.5μm band is as high as 97%, and the daytime 724W / m 2 Under the sunlight, the temperature can be reduced by 8.6℃.

[0019] 3. This invention has the following advantages:

[0020] (1) It has dual functions of heating and cooling, which can cope with hot and cold environments respectively;

[0021] (2) The cooling / heating process does not consume energy and is safe and environmentally friendly.

[0022] (3) The preparation process is simple and suitable for industrial large-scale production.

[0023] (4) The preparation cost is low and it has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a physical picture of the cooling surface in Example 1.

[0025] Figure 2 This is the SEM image of the cooling surface in Example 1.

[0026] Figure 3 This is a reflection performance diagram of the cooling surface in Example 1.

[0027] Figure 4 This is the emission performance diagram of the cooling surface in Example 1.

[0028] Figure 5 This is a physical picture of the heating surface in Example 1.

[0029] Figure 6 This is the SEM image of the heating surface in Example 1.

[0030] Figure 7 This is the absorption performance diagram of the heating surface in Example 1.

[0031] Figure 8 This is a summary diagram of the heating / cooling performance in Example 1.

[0032] Figure 9 This is a test diagram of the outdoor cooling performance of the cooling surface in Example 1.

[0033] Figure 10 This is a test diagram of the outdoor heating performance of the heating surface in Example 1. DETAILED DESCRIPTION

[0034] The specific implementation methods of the material preparation in the present invention are as follows:

[0035] Example 1: PPY-modified cotton: Cotton fabric was first washed with acetone, then with ethanol, and dried. It was then immersed in a 2 mol / L FeCl₃·6H₂O solution for 1 hour, then immersed in a pyrrole solution for 6 hours, washed with deionized water, and finally dried in a 60°C oven for 2 hours to obtain black PPY-modified cotton. PMMA / NaH₂PO₂ composite membrane: A certain amount of NaH₂PO₂ particles was stirred in DMF at 35°C for 1 hour to completely disperse them. Then, a certain amount of PMMA was added to the mixed solution and stirred at 35°C for 4 hours. The mass ratio of PMMA to DMF was 1:6, and the mass ratio of PMMA to NaH₂PO₂ was 10:3. After stirring, the dispersion was applied to the prepared PPY-modified cotton. After the solvent evaporated completely, a double-sided thermal management film was obtained. The black PPY-modified cotton was the heating side, referred to as PMC-2M; the white PMMA / NaH2PO2 composite film was the cooling side, referred to as PMMA-30%PO2.

[0036] Figure 1 This is a real picture of the cooling surface in Example 1, and the cooling surface is white. Figure 2 This is the SEM image of the cooling surface in Example 1. It can be seen that uniform small holes are formed on the surface and inside, and NaH2PO2 particles are attached to the inner wall. Figure 3 This is a reflection performance diagram of the cooling surface in Example 1. The average reflectivity in the 0.3-2.5 μm band is as high as 93%. Figure 4 This is the emissivity performance diagram of the cooling surface in Example 1. The average emissivity in the atmospheric window is as high as 98%. Figure 5 This is a physical picture of the heating surface in Example 1, and the heating surface is black. Figure 6This is the SEM image of the heating surface in Example 1. It can be seen that the PPY powder is evenly coated on the cotton fiber. Figure 7 This is the absorption performance diagram of the heating surface in Example 1. The average absorption rate in the 0.3-2.5μm band is as high as 97%. Figure 8 This is a test diagram of the cooling performance of the cooling surface in Example 1. During the day, 724W / m 2 Under the sunlight, the temperature can be reduced by 8.6℃. Figure 9 This is a test diagram of the heating performance of the heating surface in Example 1. During the day, 724W / m 2 Under strong sunlight, the temperature can rise up to 40℃.

[0037] Example 2

[0038] The concentration of FeCl3·6H2O solution is 1 mol / L, and other conditions are the same as those in Example 1. The average absorption rate of the heating surface in the 0.3-2.5 μm band is 85%, and the average absorption rate at 724 W / m 2 Under strong solar radiation, the temperature can rise by 32℃.

[0039] Example 3

[0040] The concentration of FeCl3·6H2O solution is 4 mol / L, and other conditions are the same as those in Example 1. The average absorption rate of the heating surface in the 0.3-2.5 μm band is 83%, and the average absorption rate at 724 W / m 2 Under strong solar radiation, the temperature can rise by 30℃.

[0041] Example 4

[0042] The mass ratio of PMMA to NaH2PO2 is 10:5, and other conditions are the same as those in Example 1. The average reflectivity of the cooling surface in the 0.3-2.5μm band is 89%, and the average emissivity in the atmospheric window is 97%. 2 Under the sun's radiation, the temperature can be reduced by 6.2℃.

[0043] Example 5

[0044] The mass ratio of PMMA to NaH2PO2 is 10:2, and other conditions are the same as those in Example 1. The average reflectivity of the cooling surface in the 0.3-2.5μm band is 93%, and the average emissivity in the atmospheric window is 96%. 2 Under the sun's radiation, the temperature can be reduced by 7.8℃.

Claims

1. A method for preparing a thermal management film that integrates the dual functions of radiation cooling and heating, characterized in that: First, the cotton fabric is washed with acetone, then washed with ethanol, and dried; then immersed in a ferric chloride hexahydrate FeCl3·6H2O solution, then immersed in a pyrrole solution, washed with deionized water, and finally dried in an oven to obtain black PPY modified cotton; then, NaH2PO2 particles are stirred in DMF to completely disperse them, and then PMMA is added to the mixed solution containing NaH2PO2 and DMF and stirred; after the stirring is completed, the dispersion containing PMMA, NaH2PO2 and DMF is coated on the prepared PPY modified cotton, and after the solvent is completely evaporated, a double-sided thermal management film is obtained; Wherein, the concentration of the FeCl3·6H2O solution used to prepare the PPY modified cotton is 2 mol / L, and the soaking time is 1 h; The mass ratio of PMMA to NaH2PO2 in the dispersion is 10:3, and the mass ratio of PMMA to DMF is 1:

6.

2. The method for preparing a thermal management film integrating the dual functions of radiation cooling and heating according to claim 1, characterized in that: The soaking time in the pyrrole solution is 6 hours.

3. The method for preparing a thermal management film integrating the dual functions of radiation cooling and heating according to claim 1, characterized in that: The drying temperature is 60° C. and the drying time is 2 h.

4. The method for preparing a thermal management film integrating the dual functions of radiation cooling and heating according to claim 1, characterized in that: The stirring time of the NaH2PO2 particles in DMF was 1 h.

5. The method for preparing a thermal management film integrating the dual functions of radiation cooling and heating according to claim 1, characterized in that: The PMMA was stirred in the mixed solution at a temperature of 35° C. for 4 h.

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