Preparation method of polymer-based radiation refrigeration material with porous particle nested structure

Abstract

The invention provides a preparation method of a polymer-based radiation refrigeration material with a porous particle nested structure, and belongs to the technical field of radiation cooling energy-saving structural materials. The preparation method comprises the following steps: preparing a pre-emulsion from the polymer matrix, the diluent and the emulsifier; the polymer matrix is water-insoluble polymer polydimethylsiloxane and the like; preparing dispersion liquid from nano particles and water; adding the dispersion liquid into the pre-emulsion, and violently stirring to obtain a water-in-oil emulsion; and obtaining the polymer-based radiation refrigeration material by an emulsion template method. The internal structure of the material is composed of three photon scattering interfaces with refractive index gradients, including air / polymers, nanoparticles / polymers and air / nanoparticles, and the solar reflectivity greater than 93.0% and the atmospheric window emissivity greater than 96.0% are achieved. According to the material, the temperature is reduced by 5.0 DEG C at the lowest environment temperature in the daytime, and the maximum radiation cooling power can reach 61.0 W / m < 2 >; the temperature is reduced by 16.0 DEG C at night compared with the lowest environment temperature, and the maximum radiation cooling power can reach 105.5 / W m < 2 >.

Description

Technical Field

[0001] This invention belongs to the field of radiation cooling materials technology, specifically relating to a polymer-based radiation cooling material with a porous particle nested structure and its preparation method. Background Technology

[0002] Amid the urgent global need to address high temperatures and conserve energy for carbon reduction, passive radiative cooling technology has garnered significant attention due to its potential for zero-energy cooling. Ideal radiative cooling materials must simultaneously possess high emissivity in the atmospheric window wavelength range (8-13 micrometers) and high reflectivity in the solar spectrum range (0.3-2.5 micrometers). Currently, multilayer thin-film structures based on precision coating or deposition exhibit excellent optical performance under laboratory conditions, but face challenges such as complex fabrication processes and high costs. While particle blends with high filler loading (>60wt%) are easier to implement, their optical efficiency has reached a bottleneck, and high filler loading can also lead to material brittleness and nanoparticle agglomeration. Traditional porous materials relying on toxic solvents or complex template removal processes face environmental and scalability bottlenecks. Therefore, the current technological bottleneck lies in how to ingeniously construct a multi-scattering system in which particles, pores, and polymer matrix work together within a material through a green and scalable method. This structure can not only significantly improve light scattering efficiency and the upper limit of optical performance through the huge refractive index difference between air / polymer and particles, but also fundamentally avoid dependence on high filler content and harmful processes. Summary of the Invention

[0003] To address the problems of high cost, use of toxic solvents, and complex preparation methods in existing radiation cooling materials, this invention provides a polymer-based radiation cooling material with a porous particle nested structure, and also provides a method for preparing the polymer-based radiation cooling material with a porous particle nested structure.

[0004] The preparation steps of a polymer-based radiation cooling material with a porous particle nested structure are as follows:

[0005] (1) A pre-emulsion was obtained by mixing polymer matrix, diluent, and emulsifier PEG-10 polydimethylsiloxane in a volume ratio of 1:0.5:0.01 to 0.03;

[0006] The polymer matrix is ​​one of the following: a non-water-soluble polymer, polydimethylsiloxane (PDMS), acrylic resin, and polymethylpentene.

[0007] The diluent is cyclohexane or ethyl acetate;

[0008] (2) The nanoparticles and water were ultrasonically dispersed at a mass ratio of 0.1:1 to obtain a dispersion;

[0009] The nanoparticles are one of nano-silica powder, nano-alumina powder, and nano-zirconia powder, with a particle size of 200nm to 700nm.

[0010] (3) Add the dispersion to the preemulsion at a volume ratio of 1 to 3:1 and stir vigorously to obtain a white water-in-oil emulsion;

[0011] (4) Degas the water-in-oil emulsion under vacuum;

[0012] (5) Pour the degassed water-in-oil emulsion into the mold and coat it into a film. Then cover and seal it with an airtight material such as a glass cover or metal sheet and press it appropriately. Heat it to pre-cur it to obtain a thin plate.

[0013] (6) Further heat and dry the thin plate to completely remove the internal moisture and obtain a polymer-based radiation cooling material with a porous particle nested structure;

[0014] The polymer-based radiative cooling material has a solar reflectivity greater than 93.0% and an atmospheric window emissivity greater than 96.0%.

[0015] During the day, the temperature is 3.0–5.0 °C lower than the ambient temperature, and the daytime radiative cooling power is 45.0–61.0 W / m². 2 The nighttime temperature is 12.0–16.0 °C lower than the ambient temperature, and the nighttime radiative cooling power is 100.0–105.5 W / m. 2 .

[0016] Further technical solutions are as follows:

[0017] In step (2), the ultrasonic dispersion power is 300W and the dispersion time is 15-35min.

[0018] In step (3), the dispersion is added to the pre-emulsion at a rate of 30 ml / min.

[0019] In step (3), the stirring conditions are: stirring speed 1000-12000 r / min, time 20-50 min.

[0020] In step (4), the vacuum degassing conditions are: vacuum degree 200 Pa, time 15 min.

[0021] In step (5), the pre-curing conditions are: temperature 40-60℃, time 3-4h.

[0022] In step (5), the thickness of the thin plate is 1.0 to 2.0 mm.

[0023] In step (6), the heating and drying conditions are: temperature 100-150℃, time 30-70min.

[0024] The beneficial technical effects of this invention are reflected in the following aspects:

[0025] 1. The porous particle nested structure of the polymer-based radiation cooling material of the present invention has inherent stability. In step (3), the lipophilic end of the emulsifier extends into the continuous phase (polymer / diluent), and the hydrophilic end extends into the interior of the droplet (aqueous phase), thereby forming a thermodynamically stable interfacial film. The nanoparticles (such as SiO2) in the aqueous phase are rich in hydroxyl groups on their surface. After ultrasonic dispersion, they tend to remain stably inside the aqueous phase or at the water / oil interface and are encapsulated by the emulsifier. Through the "anchoring" effect of the emulsifier, the nanoparticles are pre-confined in the water droplet template or the edge of the water droplet to form pores, laying the foundation for the subsequent "nested" structure. After emulsification, in step (4), the free bubbles generated by stirring are extracted using a vacuum environment without destroying the already stable water droplet encapsulated by the emulsifier (because the water droplet is protected by the interfacial film). In step (5), as the polymer molecular chains begin to crosslink and solidify to form a solid skeleton, the water droplet template (future pores) is completely preserved. The polymer skeleton solidifies around the water droplet template, forming a composite nested structure where the polymer encapsulates the water droplet, with particles embedded between them. In step (6), the water droplet encapsulated by the polymer skeleton rapidly vaporizes and escapes. Since the polymer skeleton has already been shaped in the pre-curing step, the space left after the water evaporates does not collapse but forms micron- or submicron-sized pores. At this point, the particles are firmly confined within the network formed by the polymer skeleton and the pores, physically suppressing the migration, aggregation, and detachment of nanoparticles. This is a complex structure that traditional blended materials cannot achieve.

[0026] 2. The preparation method of this invention can spontaneously construct a novel porous particle nested structure for polymer-based radiation cooling materials, see [link to previous section]. Figure 1 The constructed three-tiered nested system of "polymer matrix (n≈1.4-1.6) - pores (refractive index n≈1.0) - particles (n≈1.4-2.7)" excites extremely strong multiple scattering in the solar band through the huge refractive index difference between the solid / gas interface and different components. On the one hand, this changes the spatial distribution of incident light from "highly concentrated" to "widely dispersed"; on the other hand, it enhances backscattering. Thus, without relying on high-concentration fillers, it can achieve a solar reflectivity of over 98% and an atmospheric window emissivity of over 96.0%, while simultaneously achieving cooling of 3–16°C and all-day radiative cooling. The maximum radiative cooling power during the day and night can reach 61.0–105.5 W / m², respectively. 2 .

[0027] 3. The preparation method employed in this invention eliminates toxic solvents and complex template removal steps. Through a controllable emulsion template technology, a porous nested structure is constructed in one step. Furthermore, the pore size, porosity, and particle distribution within the pores can be precisely controlled by adjusting the emulsion formulation (e.g., oil-to-water ratio, emulsifier) ​​and curing parameters. This process is simple, operates under mild conditions, and is environmentally friendly, paving the way for low-cost, large-scale, continuous production of high-performance radiative cooling materials, fundamentally avoiding dependence on high filler content and harmful processes. Attached Figure Description

[0028] Figure 1 This is a schematic diagram illustrating the scattering optical advantages of porous particle nested structures;

[0029] Figure 2 This is a method for preparing a porous particle nested structure radiation cooling material;

[0030] Figure 3 It is a polymer-based radiation cooling material with a large-area porous particle nested structure;

[0031] Figure 4 This is a schematic diagram of a microscopic cross-section of a polymer-based radiation refrigeration material with a porous particle nested structure.

[0032] Figure 5 Solar band reflectivity is used as an example.

[0033] Figure 6 The example uses infrared emissivity.

[0034] Figure 7 This is a schematic diagram of the apparatus used to evaluate the radiative cooling performance of Example 3 and Comparative Example 2 in the same chamber.

[0035] Figure 8 This is a schematic diagram of the temperature curves obtained in the same chamber for Example 3 and Comparative Example 2;

[0036] Figure 9 The diagram shows the cooling effect and temperature curves on the model building for Example 3 and Comparative Example 3.

[0037] Figure 10 This is a schematic diagram of infrared thermal imaging on the surfaces of different objects in Example 4. Detailed Implementation

[0038] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] Example 1

[0040] See Figure 2 The preparation steps of a polymer-based radiation cooling material with a porous nested structure are as follows:

[0041] (1) Mix 100 ml of non-water-soluble polymer polydimethylsiloxane (PDMS), 50 ml of diluent cyclohexane and 1 ml of emulsifier PEG-10 polydimethylsiloxane directly at a volume ratio of 1:0.5:0.01 to obtain a pre-emulsion;

[0042] (2) Disperse 13.7g of nano-silica powder with a diameter of 500-700nm and 137.3ml of deionized water by ultrasonication at a mass ratio of 0.1:1. The ultrasonic dispersion power is 300W and the dispersion time is 15min to obtain a dispersion.

[0043] (3) Add the dispersion to the pre-emulsion at a speed of 30 ml / min, and stir vigorously for 30 min at a speed of 1000-12000 r / min to obtain a white water-in-oil emulsion.

[0044] (4) Degas the water-in-oil emulsion under a vacuum of 200 Pa for 15 min.

[0045] (5) Pour the degassed water-in-oil emulsion into the mold and coat it into a film. Then cover and seal it with a metal sheet and press it appropriately. Heat it at 55°C for 3 hours to pre-cur it and obtain a thin plate. The thickness of the thin plate is 1.5 mm.

[0046] (6) Under a temperature of 150℃, further heat and dry for 30 minutes to completely remove the water inside the PDMS. See [link to relevant documentation]. Figure 3 A porous nested polymer-based radiation cooling material with a thickness of 1.5 ± 0.1 mm was obtained.

[0047] The microscopic cross-sectional structure of the porous particle-nested polymer-based radiation cooling material prepared in Example 1 has a porosity of up to 60% and pore diameters between 0.1 and 15 micrometers. (See [link to example 1]). Figure 4 (a) wherein silica particles with a diameter of 500 nm are also nested at the interface between the polymer and the pores, see [reference]. Figure 4 (b). Unlike traditional porous structures, see [reference needed]. Figure 4 (c) and (d) The structure of the present invention contains three scattering interfaces: polymer matrix / air, air / nanoparticles, and nanoparticles / polymer matrix. It makes great use of the scattering characteristics between different interfaces. Combined with the high emission characteristics of the polymer matrix in the mid-infrared band, it can simultaneously achieve high solar reflectivity and high infrared emissivity.

[0048] Depend on Figure 5 It can be seen that by using a UV-Vis-NIR spectrophotometer to analyze the polymer-based radiation cooling material prepared in Example 1, its spectral reflectance in the range of 0.3 to 2.5 micrometers can be obtained, and further weighted calculation shows that its reflectance is 93.8%.

[0049] Depend on Figure 6 It can be seen that the polymer-based radiation cooling material prepared in Example 1 was analyzed using a Fourier transform infrared spectrometer with an integrating sphere, and its weighted average emissivity in the 2-20 micrometer band was 96.0%.

[0050] It achieves a temperature reduction of 3.5 °C below ambient temperature during the day, with a daytime radiative cooling power of 46.0 W / m². 2 The nighttime cooling rate is 14.4 °C lower than the ambient temperature, with a nighttime radiative cooling power of 102.0 W / m. 2 .

[0051] Example 2

[0052] The preparation method of the porous nested polymer-based radiation cooling material in Example 2 differs from that in Example 1 only in that:

[0053] In step (1), 100 ml of non-water-soluble polymer polydimethylsiloxane (PDMS), 50 ml of diluent cyclohexane and 2 ml of emulsifier PEG-10 polydimethylsiloxane are directly mixed at a volume ratio of 1:0.5:0.02 to obtain a pre-emulsion.

[0054] In step (2), 27.3g of nano-silica powder with a diameter of 500-700nm and 272.6ml of deionized water are ultrasonically dispersed at a mass ratio of 0.1:1. The ultrasonic dispersion power is 300W and the dispersion time is 25min to obtain a dispersion.

[0055] In step (3), the mixture is stirred vigorously for 40 minutes to obtain a white water-in-oil emulsion.

[0056] In step (5), the heating pre-curing time is 50 min.

[0057] The thickness of the polymer-based radiative cooling material was 1.3 ± 0.1 mm.

[0058] Depend on Figure 5 It can be seen that the weighted average solar reflectance of the radiation cooling material prepared in Example 2 is 96.0%, which is derived from... Figure 6 It can be seen that the polymer-based radiation cooling material prepared in Example 2 has a weighted average emissivity of 96.0% in the 8-13 micrometer wavelength band.

[0059] It achieves a temperature reduction of 4.2 °C below ambient temperature during the day, with a daytime radiative cooling power of 54.0 W / m². 2 The nighttime cooling rate is 15.0 °C lower than the ambient temperature, with a nighttime radiative cooling power of 103.0 / Wm. 2 .

[0060] Example 3

[0061] The preparation method of the porous particle nested structure polymer-based radiation cooling material in Example 3 differs from that in Example 1 only in that:

[0062] In step (1), 100 ml of non-water-soluble polymer polydimethylsiloxane (PDMS), 50 ml of diluent cyclohexane and 3 ml of emulsifier PEG-10 polydimethylsiloxane are directly mixed at a volume ratio of 1:0.5:0.03 to obtain a pre-emulsion.

[0063] In step (2), 41.7g of nano-silica powder with a diameter of 500-700nm and 417.3ml of deionized water are ultrasonically dispersed at a mass ratio of 0.1:1. The ultrasonic dispersion power is 300W and the dispersion time is 35min to obtain a dispersion.

[0064] In step (3), the mixture is stirred vigorously for 50 minutes to obtain a white water-in-oil emulsion.

[0065] In step (5), the heating and pre-curing time is 70 min.

[0066] The thickness of the polymer-based radiative cooling material was 1.1 ± 0.1 mm.

[0067] Depend on Figure 5 It can be seen that the polymer-based radiative cooling material prepared in Example 3 has a weighted average solar reflectance of 98.5%. Figure 6 It can be seen that the polymer-based radiation cooling material prepared in Example 3 has a weighted average emissivity of 96.1% in the 8-13 micrometer wavelength band.

[0068] It achieves a temperature reduction of 5.0 °C below ambient temperature during the day, with a daytime radiative cooling power of 61.0 W / m². 2 The nighttime cooling rate is 16.0 °C lower than the ambient temperature, with a nighttime radiative cooling power of 105.5 W / m. 2 .

[0069] Example 4

[0070] The preparation method of the porous particle nested structure polymer-based radiation cooling material in Example 4 differs from that in Example 1 only in that:

[0071] In step (1), the polymer matrix used is acrylic resin and the diluent is ethyl acetate;

[0072] In step (5), the heating pre-curing temperature is 45℃ and the pre-curing time is 3h;

[0073] In step (6), the heating and drying temperature is 110℃ and the drying time is 60min.

[0074] The thickness of the polymer-based radiative cooling material was 1.7 ± 0.1 mm.

[0075] The radiation cooling material prepared in Example 4 has a weighted average reflectivity of 94.5% in the 0.3–2.5 micrometer band and a weighted average emissivity of 96.7% in the 8–13 micrometer band.

[0076] Example 5

[0077] The preparation method of the porous particle nested structure polymer-based radiation cooling material in Example 5 differs from that in Example 1 only in that:

[0078] In step (1), the polymer matrix used is polymethylpentene;

[0079] In step (5), the heating pre-curing temperature is 160℃ and the pre-curing time is 20min.

[0080] The thickness of the polymer-based radiative cooling material was 1.2 ± 0.1 mm.

[0081] The radiation cooling material prepared in Example 5 has a weighted average reflectivity of 95.5% in the 0.3–2.5 micrometer wavelength range and a weighted average emissivity of 96.2% in the 8–13 micrometer wavelength range.

[0082] Example 6

[0083] The preparation method of the porous particle nested structure polymer-based radiation cooling material in Example 6 differs from that in Example 1 only in that:

[0084] In step (2), nano-alumina powder is used, and the particle size of the nano-alumina powder is 400-600 nm;

[0085] In step (5), the pre-curing time is 70 min at a temperature of 55℃.

[0086] The thickness of the polymer-based radiative cooling material was 1.5 ± 0.1 mm.

[0087] The polymer-based radiation cooling material prepared in Example 6 has a weighted average reflectivity of 95.0% in the 0.3–2.5 micrometer wavelength range and a weighted average emissivity of 96.6% in the 8–13 micrometer wavelength range.

[0088] Example 7

[0089] The preparation method of the porous particle nested structure polymer-based radiation cooling material in Example 6 differs from that in Example 1 only in that:

[0090] In step (2), nano-zirconia powder is used, and the particle size of the nano-zirconia powder is 200-400 nm;

[0091] In step (5), the pre-curing time is 70 min at a temperature of 55℃.

[0092] The thickness of the polymer-based radiative cooling material is 1.0 ± 0.1 mm.

[0093] The polymer-based radiation cooling material prepared in Example 7 has a weighted average reflectivity of 95.3% in the 0.3–2.5 micrometer wavelength range and a weighted average emissivity of 96.0% in the 8–13 micrometer wavelength range.

[0094] Comparative Example 1

[0095] A typical porous radiative cooling material, measuring 5 cm × 5 cm and 2 mm thick, has an average solar band reflectivity of 90.0% and an atmospheric window emissivity of 95.0%.

[0096] Comparative Example 2

[0097] Commercial radiative cooling coating, measuring 5 cm × 5 cm and 2 mm thick, with an average solar band reflectivity of 91.0% and an atmospheric window emissivity of 95.0%.

[0098] Comparative Example 3

[0099] The untreated foam board measures 15 cm × 30 cm and is 2 mm thick. It has an average solar band reflectivity of 80.0% and an atmospheric window emissivity of 92.0%.

[0100] Example of effect 1

[0101] Microstructure analysis

[0102] The porous particle nested structure radiation cooling material prepared in Example 1 and the ordinary porous radiation cooling material of Comparative Example 1 were characterized at the microscopic level using a scanning electron microscope. The testing methods are as follows:

[0103] The material was cut into strips measuring 3 cm × 0.5 cm, and then cryogenically frozen with liquid nitrogen to embrittle it. Further brittle fracture was then performed to obtain a complete fracture surface, which was subsequently imaged using a scanning electron microscope (SEM). Figure 4 As shown in (a), the random distribution of air pores and nanoparticles within the material forms three scattering interfaces with refractive index gradients (air-polymer, polymer-nanoparticle, and nanoparticle-air), which can significantly enhance the material's solar reflectivity. The regular spherical pores in the image are pores retained within the polydimethylsiloxane matrix framework after the evaporation of micro / nano-sized droplets. Its porosity is as high as 60%, with pore sizes mainly distributed between 0.1 and 15 μm. Nanoparticles in the material are significantly distributed at the interface between the polymer framework and the air pores, such as... Figure 4 As shown in (b). The main reason for this distribution is that some nanoparticles can act as emulsifiers to stabilize the oil-water interface. At the same time, the hydrophilic groups on their surface can form hydrogen bonds with the polymer, which promotes the aggregation of nanoparticles at the oil-water interface and their fixation after the droplets evaporate. This is very important and is the key element that distinguishes this structure from traditional porous structures.

[0104] Example 2

[0105] Analysis of actual cooling effect

[0106] The porous nested particle structure radiation cooling material prepared in Example 3 and Comparative Example 2 were tested in an open area under clear weather conditions. The test methods are as follows:

[0107] (1) Take the material with an area of ​​5 cm × 5 cm obtained in Example 3 above, and place it together with Comparative Example 1. Figure 7 In the same chamber of (a) in the diagram, the cross-section of the chamber is as follows: Figure 7 As shown in (b), the sample was supported by insulating columns to reduce the influence of external heat transfer. T-type thermocouples were used to measure the temperature of the lower surfaces of both samples, while data acquisition instruments monitored ambient temperature, humidity, temperature at the center of the sample bottom, solar irradiance, and wind speed. See also Figure 8 Example 3 maintained the lowest temperature throughout the day's experiment, approximately 750 W / m at noon. 2 Under sunlight, the surface temperature of the material is 6.3°C lower than the ambient temperature and 7.7°C lower than that of control example 2. At night, the radiative cooling material can achieve a maximum temperature drop of 11.2°C.

[0108] (2) Take the 10 cm × 30 cm large-area material prepared in Example 3 above and Comparative Example 3 for experimentation. Lay the material on the roof of the building model and expose it directly to the ambient air. See Figure 9(a) Two small building models were constructed using white foam and with transparent polyethylene film used as windows. Thermocouples were attached to the back of the roof and the interior environment to measure the roof temperature and the interior air temperature. Figure 9 As shown in (b), at an average solar irradiance of 900 W / m 2 Under these conditions, the average roof temperature from 11:00 to 13:00 was 1.2 °C lower than the ambient temperature, and 6.7 °C lower than the roof temperature in Comparative Example 3. Furthermore, the maximum temperature difference between the roof of the building covered in Example 3 and the exposed roof reached 8.2 °C, and the maximum indoor temperature difference throughout the day reached 4.2 °C, which is the passive cooling effect achieved in Example 3.

[0109] (3) A circular material with a diameter of 5 cm prepared in Example 7 was directly tested. Under direct sunlight, the application of Example 7 on different object surfaces was photographed using an infrared thermal imaging camera. See [link to relevant documentation] Figure 10 In example (a), when the surface temperature of human skin is 34.3°C, the surface temperature in Example 7 can be maintained at 29.0°C. See also Figure 10 In example (b), the temperature on the asphalt pavement exposed to direct sunlight can reach 54.4°C, while the surface temperature covering Example 7 is only 37.6°C. See also Figure 10 In example (c), even with a substrate temperature as high as 59.0°C, the surface temperature of Example 7 on the metal surface was only 38.9°C. Thermal imaging images from three different scenarios all show a significant temperature difference between the porous particle nested structure radiative cooling material and the surrounding object surfaces, visually demonstrating the excellent cooling effect of this structured radiative cooling material. This result verifies that the material can effectively reduce the surface temperature of objects and maintain a relatively low temperature in practical applications. This has significant practical implications for scenarios requiring efficient heat dissipation, such as building exterior walls and outdoor equipment.

[0110] In summary, the porous nested structure material prepared in the above embodiments has excellent radiative cooling performance and can be mass-produced to reduce the cost of use. It can achieve a temperature lower than the ambient temperature under direct sunlight and can also be used as an auxiliary cooling material to help cool objects without consuming any energy.

[0111] Those skilled in the art will readily understand that the above embodiments 1 to 7 are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a polymer-based radiative cooling material with a porous particle nested structure, characterized in that: (1) The polymer matrix, diluent, and emulsifier PEG-10 polydimethylsiloxane were mixed in a volume ratio of 1:0.5:0.01 to 0.03 to obtain a pre-emulsion; The polymer matrix is ​​one of the following: a non-water-soluble polymer polydimethylsiloxane (PDMS), acrylic resin, and polymethylpentene. The diluent is cyclohexane or ethyl acetate; (2) The nanoparticles and water were ultrasonically dispersed at a mass ratio of 0.1:1 to obtain a dispersion; The nanoparticles are one of nano-silica powder, nano-alumina powder, and nano-zirconia powder, with a particle size of 200nm to 700nm. (3) Add the dispersion to the preemulsion at a volume ratio of 1 to 3:1 and stir vigorously to obtain a white water-in-oil emulsion; (4) Degas the water-in-oil emulsion under vacuum; (5) Pour the degassed water-in-oil emulsion into the mold and coat it into a film. Then cover and seal it with an airtight material such as a glass cover or metal sheet and press it appropriately. Heat it to pre-cur it to obtain a thin plate. (6) Further heat and dry the thin plate to completely remove the internal moisture and obtain a polymer-based radiation cooling material with a porous particle nested structure; The polymer-based radiative cooling material has a solar reflectivity greater than 93.0% and an atmospheric window emissivity greater than 96.0%. During the day, the temperature is 3.0–5.0 °C lower than the ambient temperature, and the daytime radiative cooling power is 45.0–61.0 W / m². 2 The nighttime temperature is 12.0–16.0 °C lower than the ambient temperature, and the nighttime radiative cooling power is 100.0–105.5 W / m. 2 .

2. The method for preparing a polymer-based radiative cooling material with a porous particle nested structure according to claim 1, characterized in that: In step (2), the ultrasonic dispersion power is 300W and the dispersion time is 15-35min.

3. The method for preparing a polymer-based radiative cooling material with a porous particle nested structure according to claim 1, characterized in that: In step (3), the dispersion is added to the pre-emulsion at a rate of 30 ml / min.

4. The method for preparing a polymer-based radiative cooling material with a porous particle nested structure according to claim 1, characterized in that: In step (3), the vigorous stirring conditions are: stirring speed 1000-12000 r / min. Time: 10–30 min .

5. The method for preparing a polymer-based radiative cooling material with a porous particle nested structure according to claim 1, characterized in that: In step (4), the vacuum degassing conditions are: vacuum degree 200 Pa, time 15 min.

6. The method for preparing a polymer-based radiative cooling material with a porous particle nested structure according to claim 1, characterized in that: In step (5), the pre-curing conditions are: temperature 40-60℃, time 3-4h.

7. The method for preparing a polymer-based radiative cooling material with a porous particle nested structure according to claim 1, characterized in that: In step (5), the thickness of the thin plate is 1.0 to 2.0 mm.

8. The method for preparing a polymer-based radiative cooling material with a porous particle nested structure according to claim 1, characterized in that: In step (6), the heating and drying conditions are: temperature 100-150℃, time 30-70min.

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