A weatherable colored radiant refrigeration film and method of making the same

Abstract

A weather-resistant colored radiative cooling film belongs to the field of heat insulation film material preparation technology. The film is a porous film structure with a weather-resistant polymer matrix and uniformly dispersed modified rare earth phosphors and inorganic fillers. This invention modifies the rare earth inorganic phosphors and then synergistically and stably disperses them with silica and zirconium oxide in the polymer system. This suppresses the damage to the porous structure caused by the phase separation of the polymer by each component, which helps to improve the solar reflectivity and mid-infrared emissivity. While maintaining the color display in the visible light region, it improves the passive radiative cooling performance and enhances the weather resistance of the film. After aging, the steady-state temperature drop is relatively stable at around 0.5℃, and it still has excellent radiative cooling effect.

Description

Technical Field

[0001] This invention relates to the field of heat insulation material preparation technology, specifically to a weather-resistant colored radiation cooling film and its preparation method. Background Technology

[0002] With the continuous increase in building energy consumption and the frequent occurrence of high-temperature weather, the demand for passive cooling of building surfaces is becoming increasingly prominent. Daytime radiative cooling materials, by achieving high reflectivity in the solar radiation band and high emission in the mid-infrared atmospheric window band, can achieve passive cooling without external energy input, and have therefore attracted widespread attention. Among existing daytime radiative cooling materials, polymers are the mainstream choice in the industry because the vibrations of chemical bonds such as CF, CO, and Si-O in polymer molecules have strong emission peaks in the 8-13μm atmospheric window, naturally adapting to radiative cooling requirements and exhibiting high composite compatibility. Inorganic fillers are often added to improve solar reflectivity, and radiative cooling materials are mostly white or high-brightness in appearance. However, in practical applications, large areas of white surfaces are prone to glare and have poor environmental coordination in building facades, transportation vehicles, and other scenarios, thus limiting their widespread application. To improve these problems, some existing technologies have begun to explore the introduction of color control functions into radiative cooling materials to achieve dual functions of color and cooling.

[0003] Because traditional pigments increase solar energy absorption, the core challenge of color radiative cooling is balancing color rendering and cooling performance. Existing technologies employ organic fluorescent materials to achieve color display, while others utilize multilayer or composite structures to balance reflectivity and surface functionality. Furthermore, inorganic fluorescent materials have been explored for material display. However, these existing technologies generally suffer from several shortcomings: firstly, organic fluorescent materials are prone to light decay and aging under long-term light exposure and outdoor environments, making it difficult to meet weather resistance requirements; secondly, while multilayer or complex structural designs can improve some performance aspects, they often increase fabrication complexity and hinder the synergistic effect of color display and radiative cooling performance. Simultaneously, existing color radiative cooling materials still exhibit significant deficiencies in balancing high solar reflectivity, high to medium infrared emissivity, stable color performance, and surface durability.

[0004] Therefore, there is an urgent need to provide a colored radiation cooling film with a reasonable structure, simple preparation process, and the ability to achieve stable color display and good weather resistance while maintaining excellent radiation cooling performance, so as to meet the needs of practical engineering applications. Summary of the Invention

[0005] To address the challenge of balancing color display, passive cooling performance, and outdoor durability in existing color radiative cooling materials, this invention provides a highly weather-resistant color radiative cooling film and its preparation method. This film, by introducing multi-component composite functional fillers into a weather-resistant polymer matrix and constructing a porous structure using a phase separation film-forming process, achieves visible light color display while simultaneously maintaining high solar reflectivity, mid-infrared emissivity, and long-term stability. This improves upon the insufficient weather resistance and performance degradation issues of existing color radiative cooling materials.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] A weather-resistant colored radiation-cooling thin film, characterized in that the film has a structure in which a weather-resistant polymer is used as a matrix, and modified phosphor and inorganic filler are uniformly dispersed, wherein the modified phosphor is silane-modified Sr2Si5N8:Eu. 2+ (Sr,Ca)AlSiN3:Eu 2+ Y3Al5O 12 :Ce 3+ Y3(Gd,Al)5O 12 :Ce 3+ (Ba,Sr)2SiO4:Eu 2+ Lu3Al5O 12 :Ce 3+ At least one.

[0008] Furthermore, the inorganic filler is composed of hydrophobic fumed silica with an average particle size of 10-30 nm and nano-zirconia with an average particle size of 70-80 nm.

[0009] Furthermore, by weight percentage, the weather-resistant polymer is 45%-88%, the modified phosphor is 5-30%, the hydrophobic fumed silica is 2-10%, and the nano-zirconia is 5-15%.

[0010] A method for preparing a weather-resistant colored radiation-cooling thin film, characterized by comprising the following steps: S1. Modification treatment: Inorganic phosphors are modified with silane coupling agents; S2. Preparation of casting solution: The weather-resistant polymer is dissolved in a mixed solvent composed of a good solvent and water to form a polymer solution. Then, the surface-modified inorganic phosphor, hydrophobic fumed silica and nano-zirconia are dispersed in the polymer solution to form a uniform casting solution. S3. Wet film forming: The casting solution is coated onto the substrate to form a wet film; S4. Phase Separation Pore Formation: A non-solvent is introduced into the wet film via a gas or liquid phase to induce phase separation of the weather-resistant polymer, thereby forming a three-dimensional porous polymer framework, and embedding the composite functional filler therein. S5. Drying and curing: Remove residual solvent and perform heat treatment to obtain the radiation cooling film.

[0011] Further, the modification involves weighing inorganic phosphor, adding it to a mixed solvent of ethanol and deionized water, stirring to obtain a suspension, ultrasonically dispersing it, adding silane coupling agent KH-750, adjusting the pH to 4.2-4.8, stirring at 250-350 rpm for 2.5-3.5 hours at 55-65°C, then centrifuging to collect the solid, washing, drying, grinding, and sieving to obtain the modified inorganic phosphor. Furthermore, the ratio of the inorganic phosphor to the mixed solvent is 8~12g:140~160mL, and the volume ratio of ethanol to deionized water in the mixed solvent is 92:8~95:5.

[0012] Furthermore, the inorganic phosphor is selected from Sr2Si5N8:Eu 2+ (Sr,Ca)AlSiN3:Eu 2+ Y3Al5O 12 :Ce 3+ Y3(Gd,Al)5O 12 :Ce 3+ (Ba,Sr)2SiO4:Eu 2+ Lu3Al5O 12 :Ce 3+ At least one.

[0013] Furthermore, the casting solution is formed by dissolving a weather-resistant polymer in a mixed solvent composed of a good solvent and water to form a polymer solution, dispersing modified inorganic phosphor, hydrophobic fumed silica and nano-zirconia in the polymer solution, dispersing at 17000~19000 rpm for 12~18 min, sealing and standing for 2~3 h, and then ultrasonically treating at 350~450W power for 25~35 min to form a uniform casting solution.

[0014] Furthermore, the weather-resistant polymer is selected from at least one of polyvinylidene fluoride-hexafluoroethylene copolymer, polyvinylidene fluoride, polymethyl methacrylate, and thermoplastic polyurethane.

[0015] Furthermore, the good solvent is N,N-dimethylformamide, N,N-dimethylacetamide, or N-methylpyrrolidone, and the volume ratio of the good solvent to water is 4~9:1.

[0016] Furthermore, the solid content of the casting solution is 12-16 wt%, and by mass percentage, the weather-resistant polymer is 45%-88%, the modified phosphor is 5-30%, the hydrophobic fumed silica is 2-10%, and the nano-zirconia is 5-15%.

[0017] Furthermore, the phase separation pore formation is achieved by placing the wet film in an environment of 25°C and 80-85% relative humidity, introducing a non-solvent to induce phase separation of the weather-resistant polymer, and then drying it at 45-55°C for 2 hours to remove the substrate and create a porous radiation-cooling film.

[0018] Furthermore, the non-solvent is selected from water, C1-C4 fatty alcohols, or mixtures thereof.

[0019] In the existing technology, phosphors are directly added to the polymer matrix. However, the addition of phosphors will lead to a decrease in the performance of the matrix. The most obvious result is a worse cooling effect. In addition, the addition of phosphors will destroy the porous structure of the matrix, resulting in a decrease in the film's durability.

[0020] The long organic alkyl chains on the surface of the modified phosphor and the hydrophobic alkyl chains on the surface of silica form a chain segment entanglement network through hydrophobic interaction. Furthermore, the steric hindrance of silica and the electrostatic stabilization of nano-zirconia enable the three fillers to achieve metastable monodispersion in the casting solution. This dispersion state keeps the mass transfer channels inside the wet film continuously unobstructed. During phase separation, the diffusion of good solvent and non-solvent in the two phases is not blocked, and the diffusion rate is uniform, thus forming a complete, interconnected, and size-controllable porous structure, avoiding damage to the pore structure.

[0021] Most specifically, a method for preparing a weather-resistant colored radiation-cooling thin film is characterized by comprising the following steps: S1. Modification Treatment: Weigh the inorganic phosphor and add it to a mixed solvent of ethanol and deionized water in a volume ratio of 92:8~95:5. Stir to obtain a suspension, and ultrasonically disperse at 35~45kHz and 35~45℃ for 25~35min. Then add silane coupling agent KH-750, adjust the pH to 4.2~4.8, and stir at 250~350rpm for 2.5~3.5h at 55~65℃. Then centrifuge at 7000~9000rpm for 8~12min, collect the solid, wash it with anhydrous ethanol at least 3 times, dry the washed solid, grind it, and sieve it to obtain modified inorganic phosphor. The ratio of inorganic phosphor to mixed solvent is 8~12g:140~160mL, and the amount of silane coupling agent added is 2.5~3.5% of the mass of inorganic phosphor. The inorganic phosphor is Sr2Si5N8:Eu. 2+ (Sr,Ca)AlSiN3:Eu 2+ Y3Al5O 12 :Ce3+ Y3(Gd,Al)5O 12 :Ce 3+ (Ba,Sr)2SiO4:Eu 2+ Lu3Al5O 12 :Ce 3+ Any one of them; S2. Preparation of casting solution: Dissolve the weather-resistant polymer in a mixed solvent consisting of a good solvent and water to form a polymer solution. Disperse the modified inorganic phosphor, hydrophobic fumed silica, and nano-zirconia in the polymer solution. Disperse at 17000~19000 rpm for 12~18 min, seal and let stand for 2~3 h, and then sonicate at 350~450W power for 25~35 min to form a homogeneous casting solution. The weather-resistant polymer is selected from polyvinylidene fluoride-hexafluoroethylene copolymer. The coating contains at least one of a polymer, polyvinylidene fluoride, polymethyl methacrylate, and thermoplastic polyurethane, wherein the good solvent is N,N-dimethylformamide, N,N-dimethylacetamide, or N-methylpyrrolidone, the volume ratio of the good solvent to water is 4-9:1, the solid content of the casting solution is 12-16 wt%, and by mass percentage, the weather-resistant polymer is 45%-88%, the modified phosphor is 5-30%, the hydrophobic fumed silica is 2-10%, and the nano-zirconia is 5-15%. S3. Wet film formation: The casting solution is coated onto the substrate to form a wet film. The thickness of the wet film is controlled to be 250~300μm. The coating process is carried out at room temperature, and the coating speed is controlled to be 1.0~3.0 cm·s. -1 ; S4. Phase Separation and Pore Formation: The wet membrane is placed in an environment of 25°C and 80-85% relative humidity. An inducing solvent is introduced to induce phase separation in the weather-resistant polymer. The vapor flow rate is controlled at 0.5-2.0 L / min. -1 The phase separation time is controlled at 20~60 min, and then dried at 45~55℃ for 2 h to remove the porous radiation cooling film from the substrate.

[0022] The present invention has the following technical effects: This invention modifies rare-earth inorganic phosphors and then synergistically and stably disperses them with silica and zirconium oxide in a polymer system. This suppresses the damage to the porous structure caused by the phase separation of the polymer by each component, which helps to improve solar reflectivity and mid-infrared emissivity. While maintaining the color display in the visible light region, it also improves the passive radiative cooling performance and enhances the weather resistance of the film. After aging, the steady-state temperature drop is relatively stable at around 0.5℃, and it still has excellent radiative cooling effect. Attached Figure Description

[0023] Figure 1Scanning electron microscope images of the modified phosphors in various embodiments of the present invention.

[0024] Figure 2 : Physical images of the cooling film samples prepared according to various embodiments of the present invention.

[0025] Figure 3 Scanning electron microscope image of the radiation-cooling thin film prepared in Example 3 of this invention.

[0026] Figure 4 Contact angle test results of the radiation-cooling thin films prepared in various embodiments of the present invention.

[0027] Figure 5 Comparison of actual cooling test curves before and after aging of the radiation cooling film prepared in Embodiment 2 of the present invention. Detailed Implementation

[0028] The present invention will be specifically described below through embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Those skilled in the art can make some non-essential improvements and adjustments to the present invention based on the above description.

[0029] Example 1 A method for preparing a weather-resistant colored radiation-cooling thin film includes the following steps: S1. Modification treatment: Weigh out the inorganic phosphor Sr2Si5N8:Eu 2+ The silane coupling agent was added to a mixed solvent of ethanol and deionized water in a volume ratio of 95:5, and the mixture was stirred to obtain a suspension. The suspension was ultrasonically dispersed at 40 kHz and 40 °C for 30 min. Then, silane coupling agent KH-750 was added, and the pH was adjusted to 4.5. The mixture was stirred at 300 rpm for 3 h at 60 °C, and then centrifuged at 8000 rpm for 10 min. The solid was collected, washed at least three times with anhydrous ethanol, and dried in a vacuum drying oven at 70 °C for 8 h. The solid was then ground and passed through a 400-mesh sieve to obtain modified inorganic phosphor. The ratio of inorganic phosphor to mixed solvent was 10 g: 150 mL, and the amount of silane coupling agent added was 3% of the mass of the inorganic phosphor. S2. Preparation of casting solution: Polyvinylidene fluoride-hexafluoroethylene copolymer is dissolved in a mixed solvent composed of a good solvent and water to form a polymer solution. Modified inorganic phosphor, hydrophobic fumed silica and nano-zirconia are dispersed in the polymer solution. The dispersion is carried out at 18000 rpm for 15 min, sealed and allowed to stand for 2.5 h, and then ultrasonically treated at 400 W for 30 min to form a homogeneous casting solution. The good solvent is N,N-dimethylformamide, and the volume ratio of good solvent to water is 9:1. The solid content of the casting solution is 15 wt%. By mass percentage, the weather-resistant polymer is 65%, the modified phosphor is 20%, the hydrophobic fumed silica is 5%, and the nano-zirconia is 10%. S3. Wet film formation: The casting solution is coated onto the substrate to form a wet film. The thickness of the wet film is controlled to be 250~300μm. The coating process is carried out at room temperature, and the coating speed is controlled at 2.0 cm·s. -1 ; S4. Phase Separation Pore Formation: The wet membrane is placed in an environment of 25°C and 85% relative humidity. An inducing solvent is introduced to induce phase separation in the weather-resistant polymer. The vapor flow rate is controlled at 1.0 L·min. -1 The phase separation time was controlled at 40 min, and then dried at 50℃ for 2 h. The substrate was removed to obtain a porous cooling film, and the prepared film was red.

[0030] Example 2 A method for preparing a weather-resistant colored radiation-cooling thin film includes the following steps: S1. Modification treatment: Weigh out the inorganic phosphor (Ba,Sr)2SiO4:Eu 2+ The silane coupling agent was added to a mixed solvent of ethanol and deionized water in a volume ratio of 94:6, and the mixture was stirred to obtain a suspension. The suspension was ultrasonically dispersed at 45 kHz and 35 °C for 35 min. Then, silane coupling agent KH-750 was added, the pH was adjusted to 4.8, and the mixture was stirred at 350 rpm for 2.5 h at 65 °C. The mixture was then centrifuged at 9000 rpm for 8 min, the solid was collected, and washed at least three times with anhydrous ethanol. The washed solid was dried in a vacuum drying oven at 70 °C for 8 h, ground, and passed through a 400-mesh sieve to obtain modified inorganic phosphor. The ratio of inorganic phosphor to mixed solvent was 12 g: 160 mL, and the amount of silane coupling agent added was 3.5% of the mass of the inorganic phosphor. S2. Preparation of casting solution: Polymethyl methacrylate is dissolved in a mixed solvent consisting of a good solvent and water to form a polymer solution. Modified inorganic phosphor, hydrophobic fumed silica, and nano-zirconia are dispersed in the polymer solution. The dispersion is carried out at 17000 rpm for 18 min, sealed and allowed to stand for 2 h, and then ultrasonically treated at 450 W for 25 min to form a homogeneous casting solution. The good solvent is N,N-dimethylformamide, and the volume ratio of the good solvent to water is 6:1. The solid content of the casting solution is 12 wt%. By mass percentage, the weather-resistant polymer is 45%, the modified phosphor is 30%, the hydrophobic fumed silica is 10%, and the nano-zirconia is 15%. S3. Wet film formation: The casting solution is coated onto the substrate to form a wet film. The thickness of the wet film is controlled to be 250~300μm. The coating process is carried out at room temperature, and the coating speed is controlled at 1.0 cm·s. -1 ; S4. Phase Separation Pore Formation: The wet membrane is placed in an environment of 25°C and 80% relative humidity. An inducing solvent is introduced to induce phase separation in the weather-resistant polymer. The vapor flow rate is controlled at 0.5 L·min. -1 The phase separation time was controlled at 60 min, and then dried at 45℃ for 2 h. The substrate was removed to obtain a porous cooling film, and the resulting film was yellow.

[0031] Example 3 A method for preparing a weather-resistant colored radiation-cooling thin film includes the following steps: S1. Modification treatment: Weigh out inorganic phosphor Lu3Al5O 12 :Ce 2+ The silane coupling agent was added to a mixed solvent of ethanol and deionized water in a volume ratio of 92:8, and the mixture was stirred to obtain a suspension. The suspension was ultrasonically dispersed at 35 kHz and 45 °C for 25 min. Then, silane coupling agent KH-750 was added, and the pH was adjusted to 4.2. The mixture was stirred at 55 °C and 250 rpm for 3.5 h, followed by centrifugation at 7000 rpm for 12 min. The solid was collected, washed at least three times with anhydrous ethanol, and dried in a vacuum drying oven at 70 °C for 8 h. The solid was then ground and passed through a 400-mesh sieve to obtain modified inorganic phosphor. The ratio of inorganic phosphor to mixed solvent was 8 g:140 mL, and the amount of silane coupling agent added was 2.5% of the mass of the inorganic phosphor. S2. Preparation of casting solution: Polyvinylidene fluoride is dissolved in a mixed solvent consisting of a good solvent and water to form a polymer solution. Modified inorganic phosphor, hydrophobic fumed silica, and nano-zirconia are dispersed in the polymer solution. The dispersion is carried out at 19000 rpm for 12 min, sealed and allowed to stand for 3 h, and then ultrasonically treated at 350 W for 35 min to form a homogeneous casting solution. The good solvent is N-methylpyrrolidone, and the volume ratio of the good solvent to water is 4:1. The solid content of the casting solution is 16 wt%. By mass percentage, the weather-resistant polymer is 88%, the modified phosphor is 5%, the hydrophobic fumed silica is 2%, and the nano-zirconia is 5%. S3. Wet film formation: The casting solution is coated onto the substrate to form a wet film. The thickness of the wet film is controlled to be 250~300μm. The coating process is carried out at room temperature, and the coating speed is controlled at 3.0 cm·s. -1 ; S4. Phase Separation and Pore Formation: The wet membrane is placed in an environment of 25°C and 82% relative humidity. An inducing solvent is introduced to induce phase separation in the weather-resistant polymer. The vapor flow rate is controlled at 2.0 L·min. -1 The phase separation time was controlled to be 20 min, and then dried at 55℃ for 2 h. The substrate was removed to obtain a porous cooling film, and the resulting film was green.

[0032] Scanning electron microscope (SEM) images of the modified phosphors in Examples 1-3 are shown below. Figure 1 As shown. The porous cooling films prepared in Examples 1-3 are shown in the figures. Figure 2 As shown, from left to right, they are a red film, a yellow film, and a green film.

[0033] Scanning electron microscope (SEM) image of the radiation-cooled thin film prepared in Example 3 is shown below. Figure 3 As shown.

[0034] Blank control group: The same amount of polymer as in Example 1 was used to prepare a casting solution. Compared with Example 1, the casting solution did not contain modified phosphor, hydrophobic fumed silica and nano-zirconia. The remaining steps were the same as in Example 1. The prepared film was colorless and transparent.

[0035] Comparative Example 1 Compared to Example 1, the casting solution contained only polymer, with the addition of an equal amount of unmodified inorganic phosphor Sr2Si5N8:Eu. 2+ Without adding hydrophobic fumed silica and nano-zirconia, the remaining steps are the same as in Example 1, and the prepared film is red.

[0036] Comparative Example 2 Compared with Example 1, the casting solution contained polymers, an equal amount of unmodified inorganic phosphors, and an equal amount of hydrophobic fumed silica and nano-zirconia. The remaining steps were the same as in Example 1, and the prepared film was red.

[0037] Comparative Example 3 Compared with Example 1, the casting solution contained only polymer and modified phosphor, without the addition of hydrophobic fumed silica and nano-zirconia. The remaining steps were the same as in Example 1, and the prepared film was red.

[0038] Comparative Example 4 Compared to Example 1, the casting solution only lacks the addition of hydrophobic fumed silica; the remaining steps are the same as in Example 1.

[0039] Comparative Example 5 Compared to Example 1, only nano-zirconia was not added to the casting solution; the remaining steps were the same as in Example 1.

[0040] The thin films obtained in all the above embodiments and comparative examples were subjected to performance tests. The test items included solar reflectivity, mid-infrared emissivity, surface water contact angle, initial steady-state surface temperature drop, and steady-state surface temperature drop after 1000 h of accelerated aging under a xenon lamp. The specific test results for each embodiment and comparative example are listed in Table 1.

[0041] Table 1:

[0042] Mid-infrared emissivity is one of the most critical performance indicators of radiation-cooled thin films. This indicator directly reflects the film's radiative heat dissipation capacity, structural stability, and weather resistance. The actual cooling effect of radiation cooling is the result of the combined effect of these two core indicators: solar reflectivity and mid-infrared emissivity. Only by simultaneously satisfying high solar reflectivity and mid-infrared emissivity can the film achieve optimal passive cooling. It can be seen that the blank group film contains only polymers, resulting in low solar reflectivity and mid-infrared emissivity. The steady-state temperature drop data from the back surface also indicates poor radiation cooling performance, although its aging resistance is relatively excellent. Further addition of unmodified inorganic phosphor (Comparative Example 1) further reduced the cooling effect and significantly decreased the aging resistance. This is because the addition of inorganic phosphor disrupts the porous structure generated by phase separation, leading to a decrease in the film's radiation cooling effect. Comparative Example 2 added fillers to Comparative Example 1. The addition of fillers significantly improved the hydrophobicity of the film, but the improvement in solar reflectivity and mid-infrared emissivity was not ideal. Compared to Comparative Example 1, Comparative Example 3 involved modification of the inorganic phosphor. The addition of the modified phosphor effectively improved the radiative cooling efficiency of the film. Comparative Examples 4 and 5 were based on Comparative Example 3 with the addition of a single filler. It can be seen that the aging resistance of the films in each comparative example was not ideal. The steady-state temperature drop of the films after aging treatment was significantly lower than before aging (above 1°C), significantly higher than the blank control group. Furthermore, the solar reflectivity of each example was higher than 93.5%, the mid-infrared emissivity was higher than 0.93, and the water contact angle was greater than 145°. This indicates that the obtained films, while maintaining visible light color display, still possess high solar reflectivity, mid-infrared radiation capability, and good surface hydrophobic properties, thus achieving a significant passive radiative cooling effect. The initial steady-state surface temperature drop exceeded 8.0°C. Further, after 1000 hours of xenon lamp accelerated aging testing, the steady-state surface temperature drop of each example only decreased slightly, with no significant change in steady-state temperature drop (around 0.5°C). The temperature drop retention rate was higher than 94%, significantly better than the blank group. Therefore, this invention, by modifying rare-earth inorganic phosphors and synergistically dispersing them with silica and zirconium oxide in a system, suppresses the damage to the porous structure caused by phase separation of each component. This helps to improve solar reflectivity and mid-infrared emissivity, improves passive radiative cooling performance while maintaining visible light color display, and enhances the weather resistance of the film. Without surface modification of the inorganic phosphors, or without any functional filler from hydrophobic fumed silica or nano-zirconia, the resulting film would struggle to achieve a synergistic improvement in solar reflectivity, hydrophobicity, or radiative cooling performance.

Claims

1. A weather-resistant colored radiation-cooling thin film, characterized in that, The film is a film structure with weather-resistant polymer as matrix, uniformly dispersed modified fluorescent powder and inorganic filler, the modified fluorescent powder is silane-modified Sr2Si5N8:Eu 2+ , (Sr,Ca)AlSiN3:Eu 2+ , Y3Al5O 12 :Ce 3+ , Y3(Gd,Al)5O 12 :Ce 3+ , (Ba,Sr)2SiO4:Eu 2+ , Lu3Al5O 12 :Ce 3+ at least one.

2. The weather-resistant colored radiation-cooling thin film as described in claim 1, characterized in that: The inorganic filler is composed of hydrophobic fumed silica with an average particle size of 10-30 nm and nano-zirconia with an average particle size of 70-80 nm. By mass percentage, the weather-resistant polymer is 45-88%, the modified phosphor is 5-30%, the hydrophobic fumed silica is 2-10%, and the nano-zirconia is 5-15%.

3. A method for preparing a weather-resistant colored radiation-cooling thin film, characterized in that, Includes the following steps: S1. Modification treatment: Inorganic phosphors are modified with silane coupling agents; S2. Preparation of casting solution: The weather-resistant polymer is dissolved in a mixed solvent composed of a good solvent and water to form a polymer solution. Then, the surface-modified inorganic phosphor, hydrophobic fumed silica and nano-zirconia are dispersed in the polymer solution to form a uniform casting solution. S3. Wet film forming: The casting solution is coated onto the substrate to form a wet film; S4. Phase Separation Pore Formation: A non-solvent is introduced into the wet film via a gas or liquid phase to induce phase separation of the weather-resistant polymer, thereby forming a three-dimensional porous polymer framework, and embedding the composite functional filler therein. S5. Drying and curing: Remove residual solvent and perform heat treatment to obtain the radiation cooling film.

4. The method for preparing a weather-resistant colored radiation-cooling thin film as described in claim 3, characterized in that: The inorganic phosphor is selected from Sr2Si5N8:Eu 2+ (Sr,Ca)AlSiN3:Eu 2+ Y3Al5O 12 :Ce 3+ Y3(Gd,Al)5O 12 :Ce 3+ (Ba,Sr)2SiO4:Eu 2+ Lu3Al5O 12 :Ce 3+ At least one.

5. The method for preparing a weather-resistant colored radiation-cooled thin film as described in claim 3 or 4, characterized in that: The casting solution is formed by dissolving a weather-resistant polymer in a mixed solvent consisting of a good solvent and water to form a polymer solution. Modified inorganic phosphor, hydrophobic fumed silica, and nano-zirconia are dispersed in the polymer solution and dispersed at 17000~19000 rpm for 12~18 min. The solution is then sealed and allowed to stand for 2~3 h, and then ultrasonically treated at 350~450W power for 25~35 min to form a uniform casting solution.

6. A method for preparing a weather-resistant colored radiation-cooling thin film as described in any one of claims 3-5, characterized in that: The weather-resistant polymer is selected from at least one of polyvinylidene fluoride-hexafluoroethylene copolymer, polyvinylidene fluoride, polymethyl methacrylate, and thermoplastic polyurethane.

7. A method for preparing a weather-resistant colored radiation-cooling thin film as described in any one of claims 3-6, characterized in that: The good solvent is N,N-dimethylformamide, N,N-dimethylacetamide or N-methylpyrrolidone, and the volume ratio of the good solvent to water is 4~9:

1.

8. The method for preparing a weather-resistant colored radiation-cooled thin film as described in claim 7, characterized in that: The solid content of the casting solution is 12-16 wt%, and by mass percentage, the weather-resistant polymer is 45%-88%, the modified phosphor is 5-30%, the hydrophobic fumed silica is 2-10%, and the nano-zirconia is 5-15%.

9. The method for preparing a weather-resistant colored radiation-cooled thin film as described in claim 8, characterized in that: The phase separation pore formation is achieved by placing the wet film in an environment of 25°C and 80-85% relative humidity, introducing a non-solvent to induce phase separation of the weather-resistant polymer, and then drying it at 45-55°C for 2 hours to remove the substrate and create a porous radiation-cooling film.

10. A method for preparing a weather-resistant colored radiation-cooling thin film, characterized in that, Includes the following steps: S1. Modification Treatment: Weigh the inorganic phosphor and add it to a mixed solvent of ethanol and deionized water in a volume ratio of 92:8~95:

5. Stir to obtain a suspension, and ultrasonically disperse at 35~45kHz and 35~45℃ for 25~35min. Then add silane coupling agent KH-750, adjust the pH to 4.2~4.8, and stir at 250~350rpm for 2.5~3.5h at 55~65℃. Then centrifuge at 7000~9000rpm for 8~12min, collect the solid, wash it with anhydrous ethanol at least 3 times, dry the washed solid, grind it, and sieve it to obtain modified inorganic phosphor. The ratio of inorganic phosphor to mixed solvent is 8~12g:140~160mL, and the amount of silane coupling agent added is 2.5~3.5% of the mass of inorganic phosphor. The inorganic phosphor is Sr2Si5N8:Eu. 2+ (Sr,Ca)AlSiN3:Eu 2+ Y3Al5O 12 :Ce 3+ Y3(Gd,Al)5O 12 :Ce 3+ (Ba,Sr)2SiO4:Eu 2+ Lu3Al5O 12 :Ce 3+ Any one of them; S2. Preparation of casting solution: The weather-resistant polymer is dissolved in a mixed solvent consisting of a good solvent and water to form a polymer solution. The modified inorganic phosphor, hydrophobic fumed silica, and nano-zirconia are dispersed in the polymer solution and dispersed at 17000~19000 rpm for 12~18 min. The solution is then sealed and allowed to stand for 2~3 h, followed by ultrasonic treatment at 350~450W power for 25~35 min to form a homogeneous casting solution. The good solvent is N,N-dimethylformamide, N,N-dimethylacetamide, or N-methylpyrrolidone. The volume ratio of the good solvent to water is 4~9:

1. The solid content of the casting solution is 12~16wt%. By mass percentage, the weather-resistant polymer is 45%~88%, the modified phosphor is 5~30%, the hydrophobic fumed silica is 2~10%, and the nano-zirconia is 5~15%. S3. Wet film forming: The casting solution is coated onto the substrate to form a wet film, and the thickness of the wet film is controlled to be 250~300μm; S4. Phase separation and pore formation: The wet film is placed in an environment of 25°C and 80-85% relative humidity, and an inducing solvent is introduced to induce phase separation of the weather-resistant polymer. Then, it is dried at 45-55°C for 2 hours to remove the substrate and form a porous radiation-cooling film.

Images