A flame-retardant radiant cooling film with excellent durability and preparation method thereof

Abstract

The present invention relates to a flame-retardant radiative cooling film with excellent durability and a preparation method thereof. The radiative cooling film is a layered film with a micro-nano porous structure formed by cross-linking flame-retardant and weather-resistant resin fibers, and the flame-retardant and weather-resistant resin fibers are uniformly coated with inorganic micro-nanoparticles. The flame-retardant radiative cooling film with excellent durability provided by the present invention has excellent radiative cooling performance and thermal stability. On the one hand, it can provide strong molecular vibration in the 8-13 micron band region, enhancing the emission capability of the "atmospheric window" band. In addition, the inorganic micro-nanoparticles themselves have efficient sunlight scattering ability and can improve the emissivity of the "atmospheric window" band, further enhancing the cooling performance of the fiber membrane. On the other hand, it provides high stability of the fiber skeleton, including flame retardancy, UV resistance, and chemical corrosion resistance, and can be used for a long time in harsh environments, with good market application prospects.

Description

Technical Field

[0001] The present invention belongs to the field of refrigeration or cooling technology, and in particular relates to a flame-retardant radiation refrigeration film with excellent durability and a preparation method thereof. Background Art

[0002] In recent years, with global warming, the energy consumption of traditional active cooling technologies has skyrocketed. Furthermore, many refrigeration facilities emit large amounts of pollutants, exacerbating the greenhouse effect and creating a vicious cycle of climate change. Therefore, the refrigeration industry urgently needs to explore efficient and environmentally friendly refrigeration technologies.

[0003] Radiative cooling technology is a technique that achieves passive cooling by exploiting the vast temperature difference between the Earth's surface and outer space. Objects on the Earth's surface emit infrared radiation into space through the "atmospheric window" band (primarily between 8-13μm), thereby cooling themselves. Radiative cooling films have been developed based on the principle of radiative heat transfer. Through appropriate spectral design, they can achieve efficient cooling throughout the day. Currently, radiative cooling films can be designed to meet the needs of specific locations, including roofs, windows, and human fabrics, offering enormous potential for application.

[0004] According to Kirchhoff's law, as long as the designed cooling film has high emissivity in the 8-13 micron band, passive cooling at night can be achieved. All-weather cooling is mostly achieved by adding some highly solar-reflective micro-nano particles or constructing micro-nano porous structures. Based on the regional distribution of infrared molecular vibrations, the high infrared emission of a large number of organic polymer materials is very suitable for the development of radiation cooling materials. For example, the Si-O bond of polydimethylsiloxane will produce a 1120cm -1 Strong vibration absorption at these locations. Radiative cooling membranes fabricated by electrospinning using organic materials as fiber skeletons not only have high emissivity in the "atmospheric window" band, but also reduce daytime heat absorption by strongly scattering sunlight through the porous structure of the fibers. However, most radiative cooling membranes based on organic materials suffer from poor flame retardancy, mechanical properties, and durability, making it difficult to achieve long-term and safe cooling. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to address the deficiencies in the existing technology and provide a flame-retardant radiant cooling film with excellent durability and a preparation method thereof. The radiant cooling film has efficient all-weather cooling effect, excellent flame retardancy, high temperature resistance and super-hydrophobic properties, and can adapt to long-term ultraviolet radiation environment, and has both safety and outdoor durability.

[0006] The present invention provides a flame-retardant radiant cooling film with excellent durability. The radiant cooling film is a layered film with a micro-nano porous structure formed by cross-linking flame-retardant and weather-resistant resin fibers, and the flame-retardant and weather-resistant resin fibers are uniformly coated with inorganic micro-nano particles.

[0007] According to the above solution, the flame-retardant and weather-resistant resin fiber includes one of Teflon AF (amorphous fluoropolymer) resin fiber, polyvinylidene fluoride resin fiber, epoxy resin fiber, polyimide resin fiber, and silicone resin fiber, and has a fiber diameter of 200-800 nm. The flame-retardant and weather-resistant resin fiber has good thermal stability, is difficult to decompose, and has high emissivity in the 8-13 micron band, resulting in excellent radiative cooling effect.

[0008] According to the above scheme, the inorganic micro-nanoparticles are selected from BaSO4, Al2O3, AlPO4, SiO2, TiO2, Si3N4, or ZrO2, with a particle size of 0.2-2.5 μm. The inorganic micro-nanoparticles constitute 5-30% by weight of the flame-retardant radiant cooling film. The inorganic micro-nanoparticles selected in the present invention have excellent flame retardancy and high emissivity in the 8-13 μm wavelength range. The radiant cooling film of the present invention utilizes a micro-nano porous flame-retardant and weather-resistant resin fiber as an organic fiber skeleton, and the inorganic micro-nanoparticles are uniformly dispersed within the flame-retardant and weather-resistant resin fiber as fillers, thereby enhancing the film's overall mechanical, flame-retardant, and light-scattering properties. For high-refractive-index particles such as TiO2, only 5-10% of the flame-retardant radiant cooling film's mass is required, while for materials with lower refractive indices such as BaSO4, 10-30% is required.

[0009] According to the above solution, the thickness of the flame-retardant radiant cooling film is 200-1000 μm.

[0010] The present invention also includes a method for preparing the flame-retardant radiant cooling film having excellent durability, and the specific steps are as follows:

[0011] 1) dissolving the spinnable organic polymer in a solvent and stirring thoroughly to obtain a fiber base liquid;

[0012] 2) adding the flame-retardant and weather-resistant resin particles into water and dispersing them uniformly to obtain a flame-retardant and weather-resistant resin dispersion, then adding the obtained flame-retardant and weather-resistant resin dispersion into the fiber base liquid obtained in step 1), adding inorganic micro-nano powder after ultrasonic dispersion treatment, and ultrasonically dispersing them uniformly again to obtain a spinning solution;

[0013] 3) The spinning solution obtained in step 2) is subjected to electrospinning to obtain nanofibers, and the obtained nanofibers are wound layer by layer on a cylindrical shaft to form a nanofiber membrane on the cylindrical shaft. The obtained nanofiber membrane is then peeled off from the cylindrical shaft and sintered in a muffle furnace to obtain a flame-retardant radiant cooling film with excellent durability.

[0014] According to the above scheme, the spinnable organic polymer in step 1) is one of polyvinyl alcohol, polyethylene oxide, polyacrylonitrile, polyamide, polyvinyl chloride, and polyurethane, and has a number average molecular weight of 30-100W.

[0015] According to the above scheme, the solvent in step 1) is one of water, acetone, ethyl acetate, toluene, tetrahydrofuran, N,N-dimethylformamide, and dimethyl sulfoxide (depending on the type of the easily spinnable organic polymer), and the mass ratio of the easily spinnable organic polymer to the solvent is 4-12:100.

[0016] According to the above scheme, the flame-retardant and weather-resistant resin particles in step 2) include one of Teflon AF resin particles and polyvinylidene fluoride resin particles, with a particle size of 100-400 nm. The mass of the flame-retardant and weather-resistant resin particles accounts for 50-70% of the mass of the flame-retardant and weather-resistant resin dispersion. The flame-retardant and weather-resistant resin fibers provide strong scattering of the sun's short-wavelength limit (primarily ultraviolet) and high emission in the "atmospheric window" band.

[0017] According to the above scheme, the mass ratio of the flame retardant and weather-resistant resin dispersion in step 2) to the easily spinnable organic polymer in the fiber base liquid is 12-20:1.

[0018] According to the above scheme, the inorganic micro-nano powder in step 2) is one of BaSO4, Al2O3, AlPO4, SiO2, and TiO2, with a particle size of 0.2-2.5 μm. The mass ratio of the inorganic micro-nano powder to the flame-retardant and weather-resistant resin particles in the flame-retardant and weather-resistant resin dispersion is 0.5-3:10. The amount of filler used must be strictly controlled within an appropriate range to ensure that it does not affect the subsequent electrospinning and sintering processes. The introduction of inorganic micro-nano particles can further enhance reflectivity in the solar wavelength range.

[0019] According to the above scheme, the electrospinning process in step 3) is as follows: a spinning rate of 0.5-1 mL / h, a spinning voltage of 15-25 kV, a distance from the receiver to the needle of 12-15 cm, a drum speed of 500 rpm, a spinning temperature of 22-30°C, and a humidity of 40-60%. By adjusting the concentration of the spinning solution and the electrospinning process parameters, a nanofiber membrane of appropriate thickness is obtained. In this case, the easily spinnable organic polymer serves as the fiber skeleton, the flame-retardant and weather-resistant resin particles are tightly wrapped around the fiber skeleton, and the inorganic micro-nanoparticles are evenly dispersed and adhered to the fiber skeleton.

[0020] According to the above scheme, the thickness of the nanofiber membrane in step 3) is 100-200 μm.

[0021] According to the above scheme, the sintering process conditions of step 3) are: heating at room temperature at a heating rate of 5-20℃ / min to a temperature between the decomposition temperature of the easy-spinning organic polymer and the decomposition temperature of the flame-retardant and weather-resistant resin particles (at this temperature, the easy-spinning organic polymer is completely decomposed, and the flame-retardant and weather-resistant resin particles begin to melt but do not decompose), keeping warm for 10-60 minutes, and then cooling to room temperature with the furnace. By sintering above the decomposition temperature of the easy-spinning organic polymer, on the one hand, the easy-spinning organic polymer material serving as the fiber skeleton can be effectively removed, and on the other hand, the difficult-spinning organic polymer particles can begin to melt along the fiber skeleton, adhere to each other and self-assemble to form a fiber skeleton structure with a cavity in theory, and the inorganic micro-nanoparticles are also coated by the molten difficult-spinning organic polymer and adhere to the inside or surface of the fiber skeleton structure. This process uses the technology of easy-spinning belt and difficult-spinning to achieve the preparation of difficult-spinning organic polymer nanofiber membrane.

[0022] The present invention also includes the use of the flame-retardant radiant cooling film with excellent durability in the preparation of energy-saving building materials, heat dissipation and cooling equipment or outdoor products.

[0023] The present invention uses an electrospinning process to use an easy-to-spin organic polymer as a fiber skeleton, disperses a difficult-to-spin organic polymer (flame retardant and weather-resistant resin) and an inorganic micro-nano powder therein to obtain a spinning solution, and prepares a nanofiber membrane that highly scatters sunlight by controlling the concentration of the spinning solution and the electrospinning process conditions. Thereafter, a sintering process is used to remove the organic fiber skeleton formed by the easy-to-spin organic polymer, and at the same time, the flame retardant and weather-resistant resin attached to the organic fiber skeleton melts and self-assembles to coat the inorganic micro-nano particles to form a micro-nano porous fiber network (the micro-nano pore structure formed by the network has strong scattering properties for both short-wave and long-wave photons from the sun). That is, the original nanofiber membrane is converted into an organic-inorganic hybrid rough porous fiber membrane through the sintering process. On the one hand, the difficult-to-spin flame retardant and weather-resistant resin particles are melted and bonded to enhance the mechanical properties of the fiber membrane, and on the other hand, the roughness of the fiber skeleton is increased, thereby increasing the hydrophobicity of the radiant refrigeration membrane. The application scenario of flame-retardant radiant cooling film is outdoor environment. Its surface is highly hydrophobic, which is conducive to achieving self-cleaning effect and preventing dirt and water from being adsorbed on the surface of the cooling film, causing a decrease in cooling effect. The rough hydrophobic surface can also increase the reflection or refraction of sunlight.

[0024] The beneficial effects of the present invention are:

[0025] 1. The durable, flame-retardant radiative cooling film provided by the present invention exhibits excellent radiative cooling performance and thermal stability. It provides strong molecular vibrations in the 8-13 micron wavelength range, enhancing emission in the "atmospheric window" band. Furthermore, the inorganic micro-nanoparticles themselves possess efficient sunlight scattering capabilities, increasing the emissivity in the "atmospheric window" band, further enhancing the cooling performance of the fiber film. Furthermore, the fiber skeleton exhibits high stability, including flame retardancy, UV resistance, and chemical corrosion resistance, enabling long-term use in harsh environments and promising market application prospects.

[0026] 2. The preparation method of the present invention is relatively simple and easy to industrialize. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 SEM image of the nanofiber membrane prepared in step 3) of Example 1 of the present invention

[0028] Figure 2 This is a SEM image of the flame-retardant radiant cooling film prepared in Example 1;

[0029] Figure 3 This is a fiber diameter distribution diagram of the flame-retardant radiant cooling film prepared in Example 1;

[0030] Figure 4 This is a comparison chart of the thickness test of the nanofiber membrane prepared in step 3) of Example 1 and the flame-retardant radiative cooling membrane;

[0031] Figure 5 This is a photograph of the surface water contact angle of the flame-retardant radiative cooling film prepared in Example 1;

[0032] Figure 6 This is a diagram showing the radiative cooling effect of the flame-retardant radiative cooling film prepared in Example 1;

[0033] Figure 7 This is a test curve of the emissivity of the flame-retardant radiative cooling film prepared in Example 1 within the 2.5-25 μm band;

[0034] Figure 8 The combustion effect diagram of the nanofiber membrane prepared in Comparative Example 1 is the combustion effect diagram of the nanofiber membrane prepared in Comparative Example 1;

[0035] Figure 9 This is a comparison chart of the combustion effects of the flame-retardant radiant cooling film prepared in Example 1 and a conventional radiant cooling film;

[0036] Figure 10 This is a self-cleaning test diagram of the flame-retardant radiant cooling film prepared in Example 1;

[0037] Figure 11This is a photo of the load-bearing test of the flame-retardant radiant cooling film prepared in Example 1;

[0038] Figure 12 Graphs showing stress-strain curves of the flame-retardant radiative cooling film prepared in Example 1 and the nanofiber membrane prepared in Comparative Example 1;

[0039] Figure 13 This is a graph showing the aging resistance test of the flame-retardant radiant cooling film prepared in Example 1;

[0040] Figure 14 This is the UV-visible-near-infrared reflection pattern of the flame-retardant radiative cooling film prepared in Example 5. DETAILED DESCRIPTION

[0041] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is further described in detail below using embodiments and in conjunction with the accompanying drawings.

[0042] Comparative Example 1

[0043] A nanofiber membrane without inorganic particles, the preparation method of which has the following specific steps

[0044] 1) Mix 0.4 g of polyvinyl alcohol (number average molecular weight 60W) with 9.6 g of deionized water and stir at 60°C for 3 h to obtain a fiber base solution;

[0045] 2) Add 9.6 g of Teflon AF nanoparticles (purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., particle size 100-300 nm) to the above fiber base solution, ultrasonically vibrate for 2 hours, and magnetically stir at room temperature for 2 hours to obtain a spinning solution;

[0046] 3) The obtained spinning solution was electrospun, a No. 22 needle was selected, the needle tip was 15 cm away from the receiving roller, the temperature was maintained at 22-28°C, the humidity was about 60%, the spinning voltage was 20KV, the roller speed was 500rpm, the injection speed was 0.4mL / h, the injection liquid was 6mL, and the nanofibers obtained by electrospinning were wound layer by layer on a cylindrical shaft (the radius of the shaft was 5cm) to form a nanofiber membrane on the cylindrical shaft. The obtained nanofiber membrane was then placed in a muffle furnace, heated to 380°C at a heating rate of 20°C / min at room temperature, kept warm for 10 minutes, and cooled to room temperature with the furnace to obtain a nanofiber membrane free of inorganic particles (denoted as Teflon AF membrane) with a thickness of 382μm.

[0047] Example 1

[0048] A flame-retardant radiant cooling film with excellent durability, the preparation method of which comprises the following specific steps:

[0049] 1) Mix 0.69 g of polyvinyl alcohol (number average molecular weight 60W) with 11.50 g of deionized water and stir at 60°C for 3 h to obtain a fiber base solution;

[0050] 2) 60 g of Teflon AF nanoparticles (purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., particle size 100-300 nm) were added to 40 g of deionized water and ultrasonically dispersed for 10 h to prepare a flame retardant and weather-resistant resin dispersion. Then, 10.35 g of the obtained flame retardant and weather-resistant resin dispersion was added to the fiber base liquid obtained in step 1) and ultrasonically vibrated for 2 h. Then, 0.621 g of BaSO4 powder (particle size 2 μm) was added thereto, and ultrasonically vibrated for another 1 h to obtain a spinning solution;

[0051] 3) The obtained spinning solution was subjected to electrospinning, a No. 22 needle was selected, the needle tip was 18 cm away from the receiving drum, the temperature was maintained at 22-28 ° C, the humidity was about 60%, the spinning voltage was 22KV, the drum speed was 500 rpm, the injection speed was 1 mL / h, the injection liquid was 6 mL, and the nanofibers obtained by electrospinning were wound layer by layer on a cylindrical shaft (axis radius 5 cm) to form a nanofiber membrane on the cylindrical shaft, and then the obtained nanofiber membrane was placed in a muffle furnace and heated at room temperature at 20 ° C.

[0052] The temperature was raised to 380°C at a heating rate of 1 / min, kept at that temperature for 10 min, and then cooled to room temperature in the furnace to obtain a flame-retardant radiant cooling film with excellent durability.

[0053] Figure 1 This is the SEM image of the nanofiber membrane prepared in step 3) of this embodiment. It can be seen that the fiber membrane is obtained by winding layers of fibers with uniform thickness, and Teflon AF nanoparticles are densely attached to the fiber surface, and BaSO4 particles are evenly dispersed and adhered to the fibers.

[0054] Figure 2 This is an SEM image of the flame-retardant radiant cooling film prepared in this embodiment. It can be seen from the image that the flame-retardant radiant cooling film has a porous network structure formed by cross-linking resin fibers, and the resin fibers are uniformly coated with inorganic micro-nanoparticles with a particle size of about 2 μm.

[0055] Figure 3 This is a fiber diameter distribution diagram of the flame-retardant radiant cooling film prepared in this embodiment (obtained from the SEM image using computer software statistics). It can be seen that the resin fiber diameter is approximately 200-800 nm.

[0056] Figure 4 This is a thickness test comparison chart of the nanofiber membrane prepared in step 3) of this embodiment and the flame-retardant radiant cooling membrane. It can be seen that the thickness of the nanofiber membrane is 202 μm, and the thickness of the flame-retardant radiant cooling membrane is 326 μm. The sintering process increases the membrane thickness.

[0057] Figure 5 This is a photograph of the surface water contact angle of the flame-retardant radiative cooling film prepared in this example. The water contact angle is 150.8°, indicating that it has superhydrophobicity.

[0058] The radiant cooling effect of the flame-retardant radiant cooling film prepared in this example was tested. The flame-retardant radiant cooling film prepared in this example was placed in a hollow foam box (5 cm × 5 cm × 1 cm). The top of the foam box was sealed with polyethylene film to avoid the influence of convection. The temperature below the flame-retardant radiant cooling film was measured with a thermocouple and compared with the ambient temperature (measured by a thermocouple placed in a louvered box at a weather station). The temperature difference between the two was measured within one day. The comparison chart is shown in FIG. Figure 6 As shown in the figure, the red curve is the ambient temperature, and the blue curve is the temperature below the flame retardant radiant cooling film. It can be seen that during the day and at night, the temperature below the flame retardant radiant cooling film is significantly lower than the ambient temperature, indicating that it has a good cooling effect.

[0059] Figure 7 The emissivity test curve of the flame-retardant radiative cooling film prepared in this embodiment in the 2.5-25μm band shows that the cooling film has high emissivity in the entire mid-infrared band (2.5-25μm), reaching a maximum of 98%, demonstrating strong high-temperature cooling capability.

[0060] Figure 8 This is a combustion effect diagram of the nanofiber membrane prepared in comparative example 1. It can be seen from the figure that the nanofiber membrane is ignited and burns rapidly under standard vertical flame combustion. After the flame is removed, the fiber membrane carbonizes and turns black and shrinks rapidly, with only a small amount remaining, and the flame retardancy is poor.

[0061] Figure 9 The flame retardant radiant cooling film (Teflon AF-BaSO4) prepared in this example is compared with the conventional radiant cooling film (PDMS-BaSO4). It can be seen that after the PDMS-BaSO4 is ignited, the film continues to burn when the flame is removed, and has no flame retardant effect. However, the Teflon AF-BaSO4 does not burn under the flame and extinguishes immediately when the flame is removed. Figure 7The results show that the flame-retardant resin Teflon AF combined with the flame-retardant particles BaSO4 can achieve a good flame-retardant effect. The preparation method of PDMS-BaSO4 is as follows: 9.88g of the common organic radiation refrigeration material PDMS (polydimethylsiloxane) and 0.988g of curing agent (PDMS and curing agent are Dow Corning SYLGARD 184 two-component kit products) are mixed, and then 20g of solvent cyclohexane is added. The mixture is placed on a magnetic stirrer and stirred at 60°C for 2 hours. Then, 0.988g of BaSO4 powder (particle size 2μm) is added to the mixture. After stirring until it becomes viscous, it is coated on an aluminum plate, and then placed in an 80°C drying oven for 12 hours and peeled off from the aluminum plate.

[0062] Figure 10 This is a self-cleaning test image of the flame-retardant radiant cooling membrane prepared in this example. Dry soil was covered on the surface of the flame-retardant radiant cooling membrane to simulate dust accumulation. Then, water was sprayed through a syringe to simulate rainwater to flush the flame-retardant radiant cooling membrane. Finally, the soil on the membrane surface was washed away, indicating that the flame-retardant radiant cooling membrane prepared in this example has a self-cleaning effect.

[0063] The flame-retardant radiant cooling film prepared in this embodiment was cut into 7mm×42mm strips. A weight of 779g was hung on the strips without breaking. See the test photos. Figure 11 , which shows that the flame-retardant radiant cooling film prepared in this embodiment has high mechanical strength and good stretchability.

[0064] The flame-retardant radiative cooling film prepared in this example was cut into 7mm×42mm strips and compared with the Teflon AF film prepared in comparative example 1 of the same size. The stress-strain curves of the two were tested. The comparison diagram is shown in FIG. Figure 12 As can be seen from the figure, the flame-retardant radiant cooling film prepared in this embodiment can be stretched to 250% of its own length and can withstand a maximum tensile force of 1 MPa, while the Teflon AF film of comparative document 1 breaks after only about 10% deformation and can withstand a maximum tensile force of 0.8 MPa.

[0065] The flame-retardant radiant cooling film prepared in this example was subjected to an aging resistance test. Referring to the national standard "GBT16422.3-2022 Plastics Laboratory Light Source Exposure Test Method Part 3: Fluorescent Ultraviolet Lamp", the lamp model used in the test was UVA-340, and the irradiation intensity was 0.76w / m 2 (340nm), the test cycle is 8 hours of drying (60℃), 4 hours of condensation (50℃), and the test time is 120h. The flame retardant radiant cooling film prepared in this embodiment is compared before and after the test. Figure 13 As shown, no obvious changes were observed.

[0066] Example 2

[0067] A flame-retardant radiant cooling film with excellent durability, the preparation method of which comprises the following specific steps:

[0068] 1) Mix 0.7447 g of polyvinyl alcohol (number average molecular weight 60W) with 12.413 g of deionized water and stir at 60°C for 3 h to obtain a fiber base solution;

[0069] 2) 60 g of polyvinylidene fluoride (purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., particle size 100-300 nm, molecular weight 60W) was added to 40 g of deionized water and ultrasonically dispersed for 10 hours to prepare a flame retardant and weather-resistant resin dispersion. Then, 14.895 g of the obtained flame retardant and weather-resistant resin dispersion was added to the fiber base liquid obtained in step 1) and ultrasonically vibrated for 2 hours. Then, 2.6812 g of Al2O3 powder (particle size 300 nm) was added thereto, and ultrasonically vibrated for another hour to obtain a spinning solution;

[0070] 3) The obtained spinning solution was electrospun, a No. 23 needle was selected, the needle tip was 15 cm away from the receiving roller, the temperature was maintained at 22-28°C, the humidity was about 60%, the spinning voltage was 22KV, the roller speed was 500rpm, the injection rate was 1mL / h, the injection liquid was 9mL, and the nanofibers obtained by electrospinning were wound layer by layer on a cylindrical shaft (axis radius 5cm) to form a nanofiber membrane on the cylindrical shaft. The obtained nanofiber membrane was then placed in a muffle furnace and heated to 360°C at a heating rate of 10°C / min at room temperature, kept warm for 10 minutes, and cooled to room temperature with the furnace to obtain a flame-retardant radiation cooling film with excellent durability. The thickness was 435μm, and the fiber diameters in the cooling film were distributed between 200-800nm. According to the classical Mie scattering theory, it was confirmed that it had a strong scattering effect on sunlight.

[0071] Example 3

[0072] A flame-retardant radiant cooling film with excellent durability, the preparation method of which comprises the following specific steps:

[0073] 1) Mix 0.712 g of polyvinyl alcohol (number average molecular weight 60W, particle size 300-400 nm) with 12.235 g of deionized water and stir at 60°C for 3 h to obtain a fiber base solution;

[0074] 2) 60 g of Teflon AF nanoparticles were added to 40 g of deionized water and ultrasonically dispersed for 10 h to prepare a flame retardant and weather-resistant resin dispersion. 10.68 g of the obtained flame retardant and weather-resistant resin dispersion was then added to the fiber base liquid obtained in step 1) and ultrasonically vibrated for 2 h. 1.281 g of TiO2 powder (particle size 200 nm) was then added thereto and ultrasonically vibrated for another 1 h to obtain a spinning solution.

[0075] 3) The obtained spinning solution was electrospun, a No. 23 needle was selected, the needle tip was 15 cm away from the receiving roller, the temperature was maintained at 22-28°C, the humidity was about 60%, the spinning voltage was 22KV, the roller speed was 500rpm, the injection speed was 1mL / h, the injection liquid was 9mL, and the nanofibers obtained by electrospinning were wound layer by layer on a cylindrical shaft (axis radius 5cm) to form a nanofiber membrane on the cylindrical shaft. The obtained nanofiber membrane was then placed in a muffle furnace, heated to 380°C at a heating rate of 10°C / min at room temperature, kept warm for 10 minutes, and cooled to room temperature with the furnace to obtain a flame-retardant radiation refrigeration film with excellent durability and a thickness of 492μm.

[0076] Example 4

[0077] A flame-retardant radiant cooling film with excellent durability, the preparation method of which comprises the following specific steps:

[0078] 1) Mix 0.84 g of polyethylene oxide (purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., number average molecular weight 50W) with 10.50 g of deionized water and stir at 40°C for 3 h to obtain a fiber base solution;

[0079] 2) adding 60 g of polyvinylidene fluoride nanoparticles (molecular weight 60W, particle size 100-200 nm) to 40 g of deionized water and ultrasonically dispersing them for 10 h to prepare a flame retardant and weather-resistant resin dispersion; then taking 21 g of the obtained flame retardant and weather-resistant resin dispersion and adding it to the fiber base liquid obtained in step 1) and ultrasonically vibrating it for 2 h; then adding 1.26 g of AlPO4 powder (particle size 2 μm) thereto, and ultrasonically vibrating it for another 1 h to obtain a spinning solution;

[0080] 3) The obtained spinning solution was electrospun, a No. 23 needle was selected, the needle tip was 15 cm away from the receiving roller, the temperature was maintained at 22-28°C, the humidity was about 60%, the spinning voltage was 22KV, the roller speed was 500rpm, the injection speed was 1mL / h, the injection liquid was 9mL, and the nanofibers obtained by electrospinning were wound layer by layer on a cylindrical shaft (axis radius 5cm) to form a nanofiber membrane on the cylindrical shaft. The obtained nanofiber membrane was then placed in a muffle furnace, heated to 340°C at a heating rate of 10°C / min at room temperature, kept warm for 10 minutes, and cooled to room temperature with the furnace to obtain a flame-retardant radiation refrigeration film with excellent durability and a thickness of 488μm.

[0081] Example 5

[0082] A flame-retardant radiant cooling film with excellent durability, the preparation method of which comprises the following specific steps:

[0083] 1) Mix 0.9192 g of polyvinyl alcohol (number average molecular weight 60W) with 15.321 g of deionized water and stir at 40°C for 3 h to obtain a fiber base solution;

[0084] 2) 60 g of Teflon AF nanoparticles (particle size 100-300 nm) were added to 40 g of deionized water and ultrasonically dispersed for 10 h to prepare a flame retardant and weather-resistant resin dispersion. 14.7081 g of the obtained flame retardant and weather-resistant resin dispersion was then added to the fiber base liquid obtained in step 1) and ultrasonically vibrated for 2 h. 0.8824 g of SiO2 powder (particle size 200 nm) was then added thereto, and ultrasonically vibrated for another 1 h to obtain a spinning solution.

[0085] 3) The obtained spinning solution was electrospun, a No. 23 needle was selected, the needle tip was 15 cm away from the receiving roller, the temperature was maintained at 22-28°C, the humidity was about 60%, the spinning voltage was 22KV, the roller speed was 500rpm, the injection speed was 1mL / h, the injection liquid was 9mL, and the nanofibers obtained by electrospinning were wound layer by layer on a cylindrical shaft (axis radius 5cm) to form a nanofiber membrane on the cylindrical shaft. The obtained nanofiber membrane was then placed in a muffle furnace, heated to 360°C at a heating rate of 10°C / min at room temperature, kept warm for 10 minutes, and cooled to room temperature with the furnace to obtain a flame-retardant radiation refrigeration film with excellent durability and a thickness of 498μm.

[0086] The UV-visible-near infrared reflection pattern of the flame-retardant radiative cooling film prepared in this embodiment is shown in FIG. Figure 14 As shown, it is shown that the flame-retardant radiant cooling film prepared in this embodiment has high reflectivity in the 200-2500nm band, and the average solar reflection exceeds 95%, thereby greatly reducing the absorption of sunlight heat during the day.

[0087] The specific embodiments described above only show several preferred embodiments, but the invention is not limited to the above embodiments. There may be various changes and improvements around the basic principles of the invention. Any changes based on the concepts and principles of the invention should be included in the scope of protection of the invention.

Claims

1. A method for preparing a flame-retardant radiant cooling film with excellent durability, characterized in that: The specific steps are as follows: 1) Dissolve the easy-to-spin organic polymer in a solvent and stir thoroughly to obtain a fiber base liquid; 2) adding the flame-retardant and weather-resistant resin particles into water and dispersing them uniformly to obtain a flame-retardant and weather-resistant resin dispersion; then adding the obtained flame-retardant and weather-resistant resin dispersion into the fiber base liquid obtained in step 1); adding inorganic micro-nano powder after ultrasonic dispersion treatment; and again ultrasonically dispersing the particles uniformly to obtain a spinning solution; 3) The spinning solution obtained in step 2) is subjected to electrospinning to obtain nanofibers, and the obtained nanofibers are wound layer by layer on a cylindrical shaft to form a nanofiber membrane on the cylindrical shaft. The obtained nanofiber membrane is then peeled off from the cylindrical shaft and sintered in a muffle furnace to obtain a flame-retardant radiant cooling membrane with excellent durability. The sintering process conditions are: heating at a heating rate of 5-20°C / min at room temperature to a temperature between the decomposition temperature of the easy-to-spin organic polymer and the decomposition temperature of the flame-retardant and weather-resistant resin particles. At this temperature, the easy-to-spin organic polymer is completely decomposed, and the flame-retardant and weather-resistant resin particles begin to melt but do not decompose. The temperature is kept for 10-60 minutes, and then cooled to room temperature with the furnace.

2. The method for preparing a flame-retardant radiant cooling film with excellent durability according to claim 1, characterized in that: Step 1) the spinnable organic polymer is one of polyvinyl alcohol, polyethylene oxide, polyacrylonitrile, polyamide, polyvinyl chloride, polyurethane, and has a number average molecular weight of 30-100W; Step 1) the solvent is water, acetone, ethyl acetate, toluene, tetrahydrofuran, N, N - one of dimethylformamide and dimethyl sulfoxide, the mass ratio of the easy-to-spin organic polymer to the solvent is 4-12:

100.

3. The method for preparing a flame-retardant radiant cooling film with excellent durability according to claim 1, wherein: Step 2) the flame retardant and weather-resistant resin particles include one of Teflon AF resin particles and polyvinylidene fluoride resin particles, with a particle size of 100-400 nm, and the mass of the flame retardant and weather-resistant resin particles accounts for 50-70% of the mass of the flame retardant and weather-resistant resin dispersion; step 2) the mass ratio of the flame retardant and weather-resistant resin dispersion to the easy-to-spin organic polymer in the fiber base liquid is 12-20:1; step 2) the inorganic micro-nano powder is one of BaSO4, Al2O3, AlPO4, SiO2, and TiO2, with a particle size of 0.2-2.5 μm, and the mass ratio of the inorganic micro-nano powder to the flame retardant and weather-resistant resin particles in the flame retardant and weather-resistant resin dispersion is 0.5-3:

10.

4. The method for preparing a flame-retardant radiant cooling film with excellent durability according to claim 1, wherein: Step 3) The electrospinning process is as follows: spinning rate 0.5-1 mL / h, spinning voltage 15-25 kV, distance from receiver to needle 12-15 cm, drum speed 500 rpm, spinning temperature 22-30° C., humidity 40-60%; Step 3) The nanofiber membrane has a thickness of 100-200 μm.

5. A flame-retardant radiant cooling film with excellent durability obtained according to the preparation method according to any one of claims 1 to 4.

6. Use of the flame-retardant radiant cooling film with excellent durability according to claim 5 in the preparation of energy-saving building materials, heat dissipation and cooling equipment or outdoor products.

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