A cross-linked network structure radiation cooling film and a preparation method and application thereof

Abstract

The application discloses a cross-linked network structure radiation cooling film and a preparation method and application thereof, and belongs to the technical field of radiation cooling materials. Bacterial cellulose and water-based acrylic acid are mixed to obtain a bacterial cellulose solution in a state of adhesion; TiO2 is mixed with deionized water, and ultrasonic treatment is performed to obtain a uniformly dispersed TiO2 solution; the TiO2 solution is poured into the bacterial cellulose solution to obtain a white solution; the white solution is poured into a culture dish and dried to obtain a porous bacterial cellulose composite film with a cross-linked network structure; polydimethylsiloxane is melted into cyclohexane, sprayed on one side of the porous bacterial cellulose composite film by using a spray gun, and then subjected to heat treatment to obtain a cross-linked network structure radiation cooling film with hydrophilic on one side and hydrophobic on the other side, which has high solar reflectivity and is beneficial to cooling during the day; the surface hydrophobic treatment of the polydimethylsiloxane is beneficial to dealing with dust and complex weather during daily use, so that the radiation cooling can be maintained for a long time.

Description

Technical Field

[0001] This invention belongs to the field of radiation cooling materials technology, and specifically relates to a cross-linked network structure radiation cooling thin film, its preparation method and application. Background Technology

[0002] Accelerated global industrialization and population growth have led to increased energy consumption. Achieving carbon neutrality is a primary global environmental goal for mitigating the energy crisis. Residential buildings account for 40% of global energy consumption annually, a significant portion of which is consumed by building cooling and air conditioning systems. Therefore, improving the efficiency of existing cooling systems and developing new refrigeration technologies to enhance building energy efficiency is imperative.

[0003] Radiative cooling, as a green cooling strategy, can achieve passive cooling without external energy support. Specifically, it refers to specially designed radiative cooling devices that, while efficiently blocking solar heat, emit infrared radiation into space within an atmospheric window wavelength range (8μm-13μm) thanks to their optimized material surface structure and radiation characteristics, thereby lowering their own temperature. Given the significant temperature difference between the low-temperature environment of outer space (approximately 3K) and the relatively high ambient temperature of the Earth's surface (approximately 300K), this natural temperature difference allows for the ingenious utilization of heat radiation exchange between Earth's objects and space to achieve a cooling effect. Similar to technologies utilizing geothermal energy and other natural energy sources, radiative cooling, as an innovative energy-saving technology that leverages the natural cold source of space, can play a crucial role not only in building temperature control systems, reducing air conditioning energy consumption, but also in numerous other fields such as heat dissipation for temperature-sensitive electronic chips, battery thermal management in new energy vehicles, and temperature control for aerospace equipment. It possesses considerable application potential and development space, and is expected to play an important role in global energy conservation, emission reduction, and sustainable development.

[0004] The abundant functional groups in polymers can vibrate within a specific wavelength range, emitting infrared radiation that matches the atmospheric window band, releasing heat from objects into space as infrared radiation, thus achieving cooling. However, pure polymer-based radiative cooling materials have low solar reflectivity. To address this issue, doping with inorganic nanoparticles or porous structures has been proposed to overcome the shortcomings of polymer-based materials. Nevertheless, challenges such as poor UV resistance, poor mechanical properties, and difficulty in degradation remain to be solved.

[0005] Therefore, finding a more suitable manufacturing method to solve the aforementioned problems of existing polymer-based radiation cooling materials has become one of the focal points of widespread attention among many forward-thinking researchers in the field. Summary of the Invention

[0006] Technical Problem Solved: This application mainly proposes a cross-linked network structure radiation cooling film, its preparation method, and its application. It addresses the technical problems of existing simple polymer-based radiation cooling materials, such as low solar reflectivity, poor UV resistance, poor mechanical properties, and difficulty in degradation. The cross-linked network structure radiation cooling film provided in this application uses bacterial cellulose as a substrate and utilizes functional nanomaterials for composite processing to achieve the cross-linked network structure and porous structure design process of the radiation cooling material. It is a cooling material with high reflectivity and high emissivity, long-term durability, and good UV resistance. Moreover, the preparation method is simple, highly controllable, and suitable for large-scale production and application.

[0007] Technical solution:

[0008] A method for preparing a cross-linked network structure radiation-cooling thin film, the method specifically comprising the following steps:

[0009] Step 1: Mix 5-40 parts of bacterial cellulose and 0.01-1 parts of aqueous acrylic acid at 400 r / min for 1 h at room temperature according to the mass ratio to obtain a bacterial cellulose solution in a gel-like state;

[0010] Step 2: Mix 0.01-2.5 parts of TiO2 with 5-80 parts of deionized water according to the mass ratio, and sonicate at 80 kHz for 1 hour to obtain a uniformly dispersed TiO2 solution.

[0011] The third step is to pour the uniformly dispersed TiO2 solution into the adhesive bacterial cellulose solution and mix and stir at 400 r / min for 2 h to obtain a uniform white solution.

[0012] The fourth step is to pour the white solution into a petri dish and place it in an oven for drying heat treatment at 30℃~60℃ to obtain a porous bacterial cellulose composite membrane with a cross-linked network structure.

[0013] Step 5: Mix 0.5-2 parts of polydimethylsiloxane with 2.5-8 parts of cyclohexane according to the mass ratio, and spray it onto one side of the porous bacterial cellulose composite membrane at a rate of 0.1 mL per square centimeter. Then, perform drying and heat treatment to obtain a porous bacterial cellulose composite membrane with one side being hydrophilic and the other side being hydrophobic, namely a cross-linked network structure radiation cooling film.

[0014] As a preferred embodiment of the present invention, the mass fraction of the aqueous acrylic acid in the first step is 0.5%.

[0015] As a preferred technical solution of the present invention: the mass ratio of TiO2 to deionized water in the second step is 1:20 to 1:80.

[0016] As a preferred technical solution of the present invention: the TiO2 particle size in the second step is 100nm.

[0017] As a preferred embodiment of the present invention, the heat treatment temperature in the fourth step is between 35°C and 50°C.

[0018] As a preferred embodiment of the present invention: the heat treatment temperature in the fifth step is 80°C; the heat treatment time is 120 min.

[0019] As a preferred embodiment of the present invention, the mass ratio of polydimethylsiloxane to cyclohexane in the fifth step is 1:2 to 1:10.

[0020] This application also discloses a cross-linked network structure radiation cooling film prepared by any of the above preparation methods. The cross-linked network structure radiation cooling film is a composite material of bacterial cellulose and TiO2. The interlaced arrangement of fibers in bacterial cellulose forms a highly stable three-dimensional network structure. The cross-linked network structure radiation cooling film has highly permeable channels with a pore size of 100-400 nm.

[0021] As a preferred embodiment of the present invention, the cross-linked network structure radiation cooling film is white.

[0022] Applications of a cross-linked network structure radiation cooling film in building energy conservation, photovoltaic systems, and food packaging.

[0023] Explanation of principle: The cross-linked network structure radiation cooling film provided by this invention is a composite material of bacterial cellulose and TiO2. Due to the absorption vibration of the characteristic molecular bonds of COC and C-OH in bacterial cellulose molecules, bacterial cellulose exhibits significant infrared radiation in the atmospheric transparency window. In addition, the fibrous structure of bacterial cellulose is similar to the wavelength of sunlight, and the 100-400nm porous structure formed during the drying process helps to improve solar reflectivity.

[0024] Beneficial effects: Compared with the prior art, the method for preparing the cross-linked network structure radiation cooling thin film described in this application has the following technical advantages:

[0025] 1. The cross-linked network structure radiation cooling film provided by the present invention has a network structure with interlaced fibers and a large number of porous structures forming air-permeable channels. Unlike other radiation cooling materials, the cross-linked network structure radiation cooling film prepared by the present invention provides a good carrier for the dispersion of TiO2 due to the unique three-dimensional network structure of bacterial cellulose, thereby maximizing the UV resistance of titanium dioxide and obtaining superior anti-aging ability and long-term durability.

[0026] 2. The cross-linked network structure radiation cooling film provided by the present invention has a porous structure of 100-400nm, which effectively enhances the scattering of sunlight. The cross-linked network structure radiation cooling film benefits from the three-dimensional network structure of bacterial cellulose and effectively solves the problems of easy aging and poor mechanical properties of existing radiation cooling materials.

[0027] 3. This invention designs a simple spraying method to prepare a hydrophobic cross-linked network structure radiation cooling film. A mixed solution of polydimethylsiloxane and cyclohexane is prepared and sprayed onto one side of a bacterial cellulose composite mold through a spray gun. After drying in an oven at 80°C for 120 minutes, a porous bacterial cellulose composite film with one hydrophilic side and the other hydrophobic side is obtained. By stirring and spraying, a porous bacterial cellulose composite film with a cross-linked network structure is synthesized. The interlaced arrangement of fibers forms a three-dimensional network structure with pore sizes of 100-400 nm, which has high solar reflectivity and is beneficial for daytime cooling. The surface hydrophobic treatment of polydimethylsiloxane is beneficial for coping with dust and complex weather during daily use, so as to maintain radiation cooling for a long time.

[0028] 4. The preparation method provided by this invention is simple and economical, has good controllability, and is suitable for large-scale production and application. It has broad application prospects in fields such as building energy conservation, photovoltaic systems, and food packaging.

[0029] 5. The cross-linked network structure radiation cooling film provided by the present invention has long-term stable anti-aging ability and high-performance cooling effect when used for daytime and nighttime cooling. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the cross-linked network structure radiation cooling thin film of this application;

[0031] Figure 2 Here is a photograph of the cross-linked network structure radiation-cooling thin film sample prepared in this application;

[0032] Figure 3 The images are scanning electron microscope (SEM) images of the cross-linked network structure radiation cooling film prepared in this application. The left image is the top view of the film coated with polydimethylsiloxane, the middle image is the bottom view of the film without polydimethylsiloxane coating, and the right image is the bottom view of the film without polydimethylsiloxane coating.

[0033] Figure 4 The spectral emissivity of the cross-linked network structure radiation-cooling thin film prepared in this application is shown in the range of 0.3-20 μm.

[0034] Figure 5 A schematic diagram of a self-made device for testing the cooling performance of the cross-linked network structure radiation cooling film prepared in this application outdoors;

[0035] Figure 6The cooling performance of the cross-linked network structure radiation cooling film prepared for this application is shown in the graphs during the day and at night, where the left graph is the cooling performance during the day and the right graph is the cooling performance at night.

[0036] Figure 7 A schematic diagram of the apparatus for testing the UV resistance of the cross-linked network structure radiation-cooling thin film prepared in this application;

[0037] Figure 8 The image shows the spectral emissivity of the cross-linked network structure radiation-cooling thin film prepared in this application after ultraviolet irradiation in the 0.3-20 μm range. Detailed Implementation

[0038] To further illustrate the present invention, the preferred embodiments provided by the present invention are described below in conjunction with examples. However, it should be understood that these embodiments are implemented under the premise of the technical solution of the present invention, and detailed implementation methods and specific operation processes are given. They are only for further illustrating the features and advantages of the present invention, and are not intended to limit the scope of the claims of the present invention. The scope of protection of the present invention is not limited to the following embodiments.

[0039] There are no particular restrictions on the source of any raw materials used in this invention; they can be purchased from the market or prepared using conventional methods known to those skilled in the art.

[0040] There are no particular limitations on the purity of any raw materials used in this invention; however, analytical grade or purity commonly used in the field of photothermal interface materials is preferred. The bacterial cellulose used in this application was purchased from Flash Semiconductor.

[0041] Example 1

[0042] A method for preparing a cross-linked network structure radiation-cooling thin film, the specific method comprising the following steps:

[0043] Step 1: Mix 10 parts of bacterial cellulose and 0.06 parts of aqueous acrylic acid at 400 r / min for 1 h at room temperature according to the mass ratio to obtain a bacterial cellulose solution in a gel-like state;

[0044] Step 2: Mix 2 parts TiO2 with 60 parts deionized water according to the mass ratio, and sonicate at 80 kHz for 1 hour to obtain a uniformly dispersed TiO2 solution; the mass ratio of TiO2 to deionized water is 1:30, and the TiO2 particle size is 100 nm.

[0045] The third step is to pour the uniformly dispersed TiO2 solution into the adhesive bacterial cellulose solution and mix and stir at 400 r / min for 2 h to obtain a uniform white solution.

[0046] The fourth step is to pour the white solution into a petri dish and place it in an oven for drying heat treatment at 30℃~60℃ to obtain a porous bacterial cellulose composite membrane with a cross-linked network structure.

[0047] Step 5: Mix 1 part of polydimethylsiloxane with 4 parts of cyclohexane according to the mass ratio, and spray 0.1 mL per square centimeter onto one side of the porous bacterial cellulose composite membrane. Then dry it in an oven at 80℃ for 120 min to obtain a porous bacterial cellulose composite membrane with one side hydrophilic and the other side hydrophobic, namely a cross-linked network structure radiation cooling film.

[0048] See Figure 1 , Figure 1 This is a simplified structural diagram of the porous bacterial cellulose composite membrane with a cross-linked network structure prepared according to the present invention.

[0049] Example 2

[0050] A method for preparing a cross-linked network structure radiation-cooling thin film, the specific method comprising the following steps:

[0051] Step 1: Mix 15 parts of bacterial cellulose and 0.08 parts of aqueous acrylic acid at 400 r / min for 1 h at room temperature according to the mass ratio to obtain a bacterial cellulose solution in a gel-like state;

[0052] Step 2: Mix 1 part TiO2 with 50 parts deionized water according to the mass ratio, and sonicate at 80 kHz for 1 hour to obtain a uniformly dispersed TiO2 solution; the mass ratio of TiO2 to deionized water is 1:50, and the TiO2 particle size is 100 nm.

[0053] The third step is to pour the uniformly dispersed TiO2 solution into the adhesive bacterial cellulose solution and mix and stir at 400 r / min for 2 h to obtain a uniform white solution.

[0054] The fourth step is to pour the white solution into a petri dish and place it in an oven for drying heat treatment at 35℃~50℃ to obtain a porous bacterial cellulose composite membrane with a cross-linked network structure.

[0055] Step 5: Mix 1 part of polydimethylsiloxane with 4 parts of cyclohexane according to the mass ratio, and spray 0.1 mL per square centimeter onto one side of the porous bacterial cellulose composite membrane. Then dry it in an oven at 80℃ for 120 min to obtain a porous bacterial cellulose composite membrane with one side hydrophilic and the other side hydrophobic, namely a cross-linked network structure radiation cooling film.

[0056] Example 3

[0057] A method for preparing a cross-linked network structure radiation-cooling thin film, wherein the cross-linked network structure radiation-cooling thin film is prepared by a template-free method, and the specific method includes the following steps:

[0058] Step 1: Mix 30 parts of bacterial cellulose BC and 0.15 parts of aqueous acrylic acid AA at 400 r / min for 1 h at room temperature according to the mass ratio to obtain a bacterial cellulose solution in a gel state, denoted as ABC;

[0059] Step 2: Mix 0.5 parts TiO2 with 30 parts deionized water according to the mass ratio, and sonicate at 80 kHz for 1 hour to obtain a uniformly dispersed TiO2 solution; the mass ratio of TiO2 to deionized water is 1:60, and the TiO2 particle size is 100 nm.

[0060] The third step is to pour the uniformly dispersed TiO2 solution into the adhesive bacterial cellulose solution and mix and stir at 400 r / min for 2 h to obtain a uniform white solution.

[0061] The fourth step is to pour the white solution into a petri dish and place it in an oven for drying heat treatment at 40℃~45℃ to dehydrate the mixed solution of bacterial cellulose, aqueous acrylic acid and TiO2 to form a membrane, thus obtaining a porous bacterial cellulose composite membrane ABCT with a three-dimensional network structure.

[0062] Step 5: Mix 1 part polydimethylsiloxane with 4 parts cyclohexane according to the mass ratio, and spray 0.1 mL per square centimeter onto one side of the porous bacterial cellulose composite membrane ABCT. Then dry in an oven at 80℃ for 120 min to cure the polydimethylsiloxane and obtain a porous bacterial cellulose composite membrane PABCT, which is a cross-linked network structure radiation cooling film, that is, a hydrophilic membrane on one side and a hydrophobic membrane on the other side.

[0063] Specifically, the composite membrane has a pore structure of 100-400 nm, which enhances solar scattering and improves air permeability.

[0064] This invention simply involves mixing and stirring commercial bacterial cellulose and aqueous acrylic acid, injecting a well-dispersed TiO2 solution via ultrasound, heat-treating to dehydrate and form a film, then spraying a layer of a mixed solution of polydimethylsiloxane and cyclohexane, and finally heat-treating to obtain a hydrophobic porous bacterial cellulose composite membrane.

[0065] This invention also provides the application of the porous bacterial cellulose composite membrane described in any one of the above technical solutions or the porous bacterial cellulose composite membrane prepared by the preparation method described in any one of the above technical solutions in building energy conservation, photovoltaic systems, and food packaging.

[0066] The cross-linked network structure radiation cooling film provided by this invention has a network structure with interlaced fibers and numerous porous channels for air permeability. Due to the unique three-dimensional network structure of bacterial cellulose, it provides an excellent carrier for TiO2 dispersion, thereby maximizing the UV resistance of titanium dioxide to achieve superior anti-aging capabilities and long-term durability. Furthermore, this composite film has a porous structure with a diameter of 100-400 nm, effectively enhancing the scattering of sunlight. The porous bacterial cellulose composite film with a cross-linked network structure provided by this invention effectively solves the problems of easy aging and poor mechanical properties of existing radiation cooling materials, thanks to the three-dimensional network structure of bacterial cellulose.

[0067] Example 4

[0068] A method for preparing a cross-linked network structure radiation-cooling thin film, wherein the cross-linked network structure radiation-cooling thin film is prepared by a template-free method, and the specific method includes the following steps:

[0069] Step 1: Mix 20 mL of bacterial cellulose BC and 0.1 mL of aqueous acrylic acid AA at 400 r / min for 1 h at room temperature to obtain a bacterial cellulose solution in a gel-like state, denoted as ABC;

[0070] Step 2: Mix 0.2 parts TiO2 with 10 parts deionized water according to the mass ratio, and sonicate at 80 kHz for 1 hour to obtain a uniformly dispersed TiO2 solution; the TiO2 particle size is 100 nm.

[0071] The third step is to pour the uniformly dispersed TiO2 solution into the adhesive bacterial cellulose solution and mix and stir at 400 r / min for 2 h to obtain a uniform white solution.

[0072] The fourth step is to pour the white solution into a petri dish and place it in an oven for drying heat treatment at 40℃~45℃ to dehydrate the mixed solution of bacterial cellulose, aqueous acrylic acid and TiO2 to form a membrane, thus obtaining a porous bacterial cellulose composite membrane ABCT with a three-dimensional network structure.

[0073] Step 5: Mix 1 part polydimethylsiloxane with 4 parts cyclohexane according to the mass ratio, and spray 0.1 mL per square centimeter onto one side of the porous bacterial cellulose composite membrane ABCT. Then dry in an oven at 80℃ for 120 min to cure the polydimethylsiloxane and obtain a porous bacterial cellulose composite membrane PABCT, which is a cross-linked network structure radiation cooling film, that is, a hydrophilic membrane on one side and a hydrophobic membrane on the other side.

[0074] See Figure 2 , Figure 2The images show physical samples of the cross-linked network structure radiation cooling thin film prepared in this application; from left to right, they are a porous bacterial cellulose composite membrane (PABCT) coated with polydimethylsiloxane and a porous bacterial cellulose composite membrane (ABCT) without polydimethylsiloxane coating.

[0075] See Figure 3 , Figure 3 The images shown are scanning electron microscope (SEM) images of the cross-linked network structure radiation cooling thin film prepared in this application. The left image is a porous bacterial cellulose composite membrane (PABCT) coated with polydimethylsiloxane, the middle image is a porous bacterial cellulose composite membrane (ABCT) without polydimethylsiloxane coating, and the right image is a porous bacterial cellulose composite membrane (ABCT) without polydimethylsiloxane coating.

[0076] See Figure 4 , Figure 4 The spectral emissivity of the cross-linked network structure radiation-cooling thin film prepared in this application is shown in the range of 0.3-20 μm.

[0077] See Figure 5 , Figure 5 A schematic diagram of a self-made device for testing the cooling performance of the cross-linked network structure radiation cooling film prepared in this application outdoors;

[0078] To further illustrate this, the cooling performance of the prepared cross-linked network structure radiation cooling film was characterized.

[0079] See Figure 6 , Figure 6 The cooling performance of the cross-linked network structure radiation cooling film prepared for this application is shown in the graphs during the day and at night, where the left graph is the cooling performance during the day and the right graph is the cooling performance at night.

[0080] See Figure 7 , Figure 7 A schematic diagram of the apparatus for testing the UV resistance of the cross-linked network structure radiation-cooling thin film prepared in this application;

[0081] See Figure 8 , Figure 8 The image shows the spectral emissivity of the cross-linked network structure radiation-cooling thin film prepared in this application after ultraviolet irradiation in the 0.3-20 μm range.

[0082] The results show that PABCT, benefiting from its interwoven fiber network structure and numerous porous structures, exhibits low absorptivity in the solar radiation band and high emissivity in the atmospheric window band. As a radiative cooler, PABCT has a solar absorptivity of 10.9% and an atmospheric window emissivity of 94.6%. In outdoor cooling performance tests, the maximum daytime temperature drop relative to ambient temperature was 7.15℃, with an average drop of 4.85℃; the maximum daytime temperature drop relative to ambient temperature was 2.7℃, with an average drop of 2.32℃. It also exhibits excellent UV resistance. This invention opens up new avenues for the further development of anti-aging, high-efficiency radiative cooling materials.

[0083] The preparation method and application of a cross-linked network structure porous bacterial cellulose composite membrane provided by the present invention have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention, including the best mode, and also to enable any person skilled in the art to practice the present invention, including manufacturing and using any device or system, and implementing any combined method. It should be noted that for those skilled in the art, several improvements and modifications can be made to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention. The scope of protection of this patent is defined by the claims and may include other embodiments that can be conceived by those skilled in the art. If these other embodiments have structural elements that are not different from the textual description of the claims, or if they include equivalent structural elements that are not substantially different from the textual description of the claims, then these other embodiments should also be included within the scope of the claims.

[0084] The embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A method for preparing a cross-linked network structure radiation-cooling thin film, characterized in that, The preparation method specifically includes the following steps: Step 1: Mix 5-40 parts of bacterial cellulose and 0.01-1 parts of aqueous acrylic acid at 400 r / min for 1 h at room temperature according to the mass ratio to obtain a bacterial cellulose solution in a gel state. The bacterial cellulose was purchased from Flash Technology. Step 2: Mix 0.01-2.5 parts of TiO2 with 5-80 parts of deionized water according to the mass ratio, and sonicate at 80 kHz for 1 hour to obtain a uniformly dispersed TiO2 solution. The third step is to pour the uniformly dispersed TiO2 solution into the adhesive bacterial cellulose solution and mix and stir at 400 r / min for 2 h to obtain a uniform white solution. The fourth step is to pour the white solution into a petri dish and place it in an oven for drying heat treatment at 30℃~60℃ to obtain a porous bacterial cellulose composite membrane with a cross-linked network structure. Step 5: Mix 0.5-2 parts of polydimethylsiloxane with 2.5-8 parts of cyclohexane according to the mass ratio, and spray 0.1 mL per square centimeter onto one side of the porous bacterial cellulose composite membrane. Then, perform drying and heat treatment to obtain a porous bacterial cellulose composite membrane with one side hydrophilic and the other side hydrophobic, namely a cross-linked network structure radiation cooling film. The cross-linked network structure radiation cooling film is a composite material of bacterial cellulose and TiO2. The interlaced arrangement of fibers in bacterial cellulose forms a highly stable three-dimensional network structure. The cross-linked network structure radiation cooling film has highly permeable channels with a pore size of 100-400nm.

2. The method for preparing the cross-linked network structure radiation-cooling thin film according to claim 1, characterized in that: The mass fraction of the aqueous acrylic acid in the first step is 0.5%.

3. The method for preparing the cross-linked network structure radiation-cooling thin film according to claim 1, characterized in that: The mass ratio of TiO2 to deionized water in the second step is 1:20 to 1:

80.

4. The method for preparing a cross-linked network structure radiation-cooling thin film according to claim 1, characterized in that: The TiO2 particle size in the second step is 100 nm.

5. The method for preparing a cross-linked network structure radiation-cooling thin film according to claim 1, characterized in that: The heat treatment temperature in the fourth step is 35℃~50℃.

6. The method for preparing a cross-linked network structure radiation-cooling thin film according to claim 1, characterized in that: The fifth step of the heat treatment is performed at a temperature of 80°C for 120 minutes.

7. The method for preparing a cross-linked network structure radiation-cooling thin film according to claim 1, characterized in that: The mass ratio of polydimethylsiloxane to cyclohexane in the fifth step is 1:2 to 1:

10.

8. A cross-linked network structure radiation-cooling thin film prepared by the preparation method according to any one of claims 1-7, characterized in that: The cross-linked network structure radiation cooling film is white.

9. The application of the cross-linked network structure radiation cooling film as described in claim 8 in building energy conservation, photovoltaic systems, and food packaging.

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