Flexible high-conductivity and high-dissipation phase change composite film with micro-nano structure, and preparation method and application thereof

Abstract

This invention discloses a flexible, highly conductive, heat-dissipating phase change composite film with a micro / nano structure, its preparation method, and its applications, belonging to the field of new energy materials and nanotechnology. A three-dimensional porous foam is prepared by blending carbon thermally conductive material with melamine and foaming. A flexible thermally conductive silicon film is then modified onto the surface of the three-dimensional porous foam. Molten phase change material is filled into the three-dimensional porous foam to obtain a flexible, highly conductive, heat-dissipating phase change composite film with a micro / nano structure. This flexible, highly conductive, heat-dissipating phase change composite film with a micro / nano structure consists of a thermally conductive network and a phase change material. The thermally conductive network is a porous micro / nano structure formed by carbon thermally conductive material and melamine. The carbon thermally conductive material is covered by a flexible thermally conductive silicon layer, and the phase change material is filled in the thermally conductive network. It can actively absorb and dissipate heat, has strong weather resistance, and is particularly suitable for cooling and thermal management of outdoor photovoltaic modules and 5G base station components. It can improve device operating efficiency, has controllable preparation conditions, low equipment requirements, and is suitable for large-scale production.

Description

Technical Field

[0001] This invention belongs to the field of new energy materials and nanotechnology, specifically relating to a flexible, highly conductive heat-dissipating phase change composite thin film with micro-nano structure, its preparation method, and its application. Background Technology

[0002] In photovoltaic power generation, the photoelectric conversion efficiency of solar panels is affected not only by the performance of the semiconductor materials themselves but also by the operating temperature. Because solar panels generate a significant amount of heat during operation, their temperature is higher than the surrounding environment. Excessively high temperatures can reduce the photoelectric conversion efficiency of the solar panels and even shorten their lifespan.

[0003] The heat dissipation performance of a photovoltaic (PV) backsheet directly affects the conversion efficiency and lifespan of the PV panel. Currently, the most widely used thermal interface materials in the industry include sheet-like thermally conductive gap fillers and phase change thermally conductive materials. However, because the direct contact thermal resistance between the thermally conductive material and the PV backsheet is relatively high, and the thermal conductivity of the material in the macroscopic vertical direction is poor, the thermal conductivity is low and the cost is high.

[0004] To address the aforementioned issues, there is an urgent need to find a new thermally conductive material to solve the problems of high thermal resistance in direct contact between the thermally conductive material and the photovoltaic backsheet, as well as poor thermal conductivity of the thermally conductive material in the macroscopic vertical direction. This would improve the thermal conductivity efficiency of the thermally conductive material, increase the operating efficiency of the device, and reduce production costs. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, the present invention aims to provide a high thermal conductivity phase change flexible composite film with micro-nano structure and its preparation method, so as to solve the technical problems of high thermal resistance in direct contact between existing thermal conductive materials and photovoltaic backsheets, poor thermal conductivity of thermal conductive materials in the macroscopic vertical direction, resulting in low thermal conductivity and high cost.

[0006] To achieve the above objectives, the present invention employs the following technical solution:

[0007] This invention discloses a flexible, high-conductivity heat-dissipating phase change composite film with a micro-nano structure, which is composed of a thermally conductive network and a phase change material filled in the thermally conductive network; the mass percentage of the thermally conductive network is 10% to 60%, and the mass percentage of the phase change material is 40% to 90%; the thermally conductive network is a three-dimensional porous micro-nano structure, which is formed by a flexible thermally conductive silicon layer coated with carbon thermally conductive material and melamine.

[0008] Preferably, the flexible, high-conductivity heat-dissipating phase change composite film with micro-nano structure has a thermal conductivity of 0.5–5.0 W / m·K, a phase change temperature of 30–70 °C, and an enthalpy of 150–210 J / g.

[0009] This invention also discloses a method for preparing the above-mentioned flexible, highly conductive, heat-dissipating phase change composite thin film with micro / nano structure, comprising the following steps:

[0010] 1) Mix and disperse the cosolvent and melamine in water, then add additives and carbon thermal conductive material in sequence. After foaming and curing, a porous melamine composite film with carbon thermal conductive material as the skeleton is obtained.

[0011] 2) The surface of the melamine porous composite film with carbon thermally conductive material as the skeleton obtained in step 1) is modified with a flexible thermally conductive silicon layer to obtain a flexible high thermal conductivity porous composite film.

[0012] 3) Fill the flexible, highly thermally conductive porous composite film obtained in step 2) with phase change material to obtain a flexible, highly thermally conductive phase change composite film with micro-nano structure.

[0013] Preferably, in step 1), the mass ratio of the co-solvent: melamine: additive: carbon thermal conductive material is (100-140):(120-160):(1-14):(2-10); the dispersion conditions are stirring at 70-85℃ for 20-30 minutes, and the foaming conditions are stirring at 90-105℃ for 40-50 minutes.

[0014] Preferably, in step 1), the carbon thermally conductive material is any one of carbon nanowires, carbon fibers, and carbon nanotubes, and the content of the carbon thermally conductive material is 1-5 wt% of the melamine content; the co-solvent is paraformaldehyde; the additives include a foaming agent, a foam leveling agent, and a curing agent; the mass ratio of the foaming agent: foam leveling agent: curing agent is (5-7):(2-4):(1-1.5). The foaming agent is n-hexane or n-pentane; the foam leveling agent is dimethyl silicone oil; and the curing agent is hydrochloric acid or phosphoric acid.

[0015] Preferably, in step 1), the thickness of the melamine porous composite film with carbon thermal conductive material as the skeleton is 2 to 20 mm.

[0016] Preferably, in step 2), the mass ratio of the melamine porous composite film with carbon thermally conductive material as the skeleton to the flexible thermally conductive silicon layer is (500-2000):(2-20); the flexible thermally conductive silicon layer comprises graphite nanoparticles and organosilicon surfactants; the mass ratio of graphite nanoparticles to organosilicon surfactants is (1-4):(5-16); the size of the graphite nanoparticles is 0.4-1 μm; and the organosilicon surfactant is at least one of polydimethylsiloxane, cyclomethylsiloxane, aminosiloxane, polymethylphenylsiloxane, and polyether polysiloxane copolymer.

[0017] Preferably, in step 2), the thickness of the flexible thermally conductive silicon layer is 1 to 10 μm; the flexible high thermal conductivity porous composite film is a connected, flexible, irregular three-dimensional porous micro / nano structure film.

[0018] Preferably, in step 3), the phase change material is at least one of myristic acid, palmitic acid, decanoic acid, stearic acid, lauric acid, polyethylene glycol, paraffin / SBS, and lauric acid-stearic acid / SiO2.

[0019] The present invention also discloses the application of the above-mentioned flexible high-conductivity heat dissipation phase change composite thin film with micro-nano structure in the preparation of outdoor photovoltaic modules and 5G base station components.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] This invention discloses a high thermal conductivity phase change flexible composite film with a micro / nano structure. This film consists of a thermally conductive network and a phase change material filled within the network. The phase change material can absorb or release a large amount of heat during the phase change process, thus exhibiting excellent heat dissipation and insulation performance. The energy storage performance of the phase change material can be adjusted according to its heat storage and release temperatures to meet different application requirements. The thermally conductive network is composed of a three-dimensional porous micro / nano structure formed by flexible thermally conductive silicon-coated carbon thermally conductive material and melamine. The microstructure in the high thermal conductivity phase change flexible composite film with a micro / nano structure can improve the film's surface area and permeability, facilitating the adsorption and transport of substances. Simultaneously, the micro / nano structure can also enhance the film's mechanical properties and stability. This flexible, high-conductivity phase change composite film with a micro / nano structure comprises a thermally conductive network of 10%–60% by mass and a phase change material of 40%–90% by mass. It exhibits relatively high thermal conductivity and enthalpy, and a wide phase change temperature range, thus demonstrating better stability and reliability, and maintaining its performance over a longer period. Its high thermal conductivity allows for rapid heat transfer and dispersion, effectively improving heat transfer efficiency. Its good flexibility allows it to adapt to surfaces of various shapes and curvatures, expanding its application areas. By combining melamine with a carbon thermally conductive material with a surface-modified flexible thermally conductive silicon layer, it achieves close adhesion to the heat-generating components, resulting in low direct contact thermal resistance and good thermal conductivity in the macroscopic vertical direction. Furthermore, the combination with a material with high latent heat of phase change solves the technical problems of high direct contact thermal resistance between existing thermally conductive materials and photovoltaic backsheets, poor thermal conductivity in the macroscopic vertical direction, leading to low thermal efficiency and high cost.

[0022] Furthermore, this flexible, high-conductivity phase change composite film with a micro / nano structure exhibits a thermal conductivity of 0.5–5.0 W / m·K, resulting in higher heat dissipation efficiency and more effective heat transfer and dispersion. Its phase change temperature ranges from 30 to 70°C, allowing the material to undergo phase change at lower or higher temperatures to meet diverse application requirements. With an enthalpy of 150–210 J / g, the phase change material can absorb or release a significant amount of heat during the phase change process, demonstrating excellent heat dissipation and insulation performance. This flexible, high-conductivity phase change composite film with a micro / nano structure possesses a flexible three-dimensional porous micro / nano structure, exhibiting low thermal resistance in direct contact with the photovoltaic backsheet, good thermal conductivity in the macroscopic vertical direction, and a large latent heat of phase change. This significantly enhances the overall heat dissipation capacity of the photovoltaic module, providing both active heat absorption and dissipation, and exhibiting strong weather resistance.

[0023] This invention also discloses a method for preparing the aforementioned high thermal conductivity phase change flexible composite film with micro / nano structure. A co-solvent and melamine are mixed and dispersed in water, and then additives and a carbon thermally conductive material are added sequentially. After foaming and curing, a porous melamine composite film with the carbon thermally conductive material as its framework is obtained. The carbon thermally conductive material has excellent thermal conductivity, which can rapidly transfer heat energy to the entire composite film, thereby improving the film's heat transfer efficiency. The carbon thermally conductive material also has high strength, high hardness, and wear resistance, providing good mechanical support for the film and enhancing its stability and durability. The pore structure in the porous melamine composite film can increase the film's surface area and permeability, which is beneficial for the adsorption and transport of substances. The carbon thermally conductive material, as a framework, can provide the film with more pore structures, further improving the film's adsorption and transport performance. The carbon thermally conductive material has high thermal stability, allowing it to operate in high-temperature environments without easily melting or deforming, which is beneficial for the film's application under high-temperature conditions. A melamine porous composite film with a carbon thermally conductive material as its framework is used as a carrier, and a flexible thermally conductive silicon layer is applied to its surface to obtain a flexible, highly thermally conductive porous composite film. This facilitates better adhesion of the heating components, resulting in lower direct contact thermal resistance. It also exhibits good thermal conductivity in the macroscopic vertical direction. Finally, a phase change material is used to fill the flexible, highly thermally conductive porous composite film using a melt-filling method, resulting in a flexible, highly thermally conductive phase change composite film. Combining this with a material with high latent heat of phase change enhances the heat absorption and release capabilities. The preparation method provided by this invention features mild and controllable reaction conditions, low equipment requirements, low energy consumption, low cost, and is environmentally friendly and pollution-free, enabling large-scale production.

[0024] This invention also discloses the application of the above-mentioned high thermal conductivity phase change flexible composite film with micro-nano structure in the preparation of outdoor photovoltaic modules and 5G base station components. When the high thermal conductivity phase change flexible composite film with micro-nano structure prepared by this invention is applied to the preparation of outdoor photovoltaic modules and 5G base station components, it has the functions of active heat absorption and heat dissipation, strong weather resistance, and can improve the working efficiency of the device. The material has good flexibility and can adapt to surfaces with various shapes and curvatures, thereby expanding its application fields. Attached Figure Description

[0025] Figure 1 This is a scanning electron microscope image of the flexible, highly conductive, heat-dissipating phase change composite thin film with micro-nano structure prepared in Example 1 of the present invention.

[0026] Figure 2 This is a measured cooling effect of the flexible, highly conductive heat-dissipating phase change composite film with micro-nano structure prepared in Example 1 of the present invention on a solar panel. Detailed Implementation

[0027] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. 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 should fall within the scope of protection of the present invention.

[0028] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0029] The present invention will now be described in further detail with reference to the accompanying drawings:

[0030] This invention discloses a method for preparing a flexible, highly conductive, heat-dissipating phase change composite thin film with a micro / nano structure, comprising the following steps:

[0031] 1) Mix and disperse the cosolvent and melamine in water, then add the additives and carbon thermal conductive material in sequence to obtain a mixture. Disperse, foam and cure the mixture to obtain a porous melamine composite film with carbon thermal conductive material as the skeleton.

[0032] 2) Using a carbon thermally conductive material as a framework, a melamine porous composite film is used as a carrier, and a flexible thermally conductive silicon layer is modified on the surface to obtain a flexible high thermal conductivity porous composite film.

[0033] 3) The flexible high thermal conductivity porous composite film is filled with phase change material by melt filling to obtain a flexible high thermal conductivity phase change composite film.

[0034] In step 1), the mass ratio of water: co-solvent: melamine: carbon thermal conductive material is (70-100): (50-70): (60-80): (1-5).

[0035] The dispersion conditions are 70-85℃ and stirring for 20-30 minutes, and the foaming conditions are 90-105℃ and stirring for 40-50 minutes.

[0036] Carbon thermal conductive materials include any one of carbon nanowires, carbon fibers, and carbon nanotubes.

[0037] The content of carbon thermal conductive material is 1-5 wt% of the melamine content.

[0038] The thickness of the melamine porous composite film with carbon thermal conductive material as the skeleton is 2-20 mm.

[0039] The cosolvent is paraformaldehyde; the additives include a foaming agent, a foam leveling agent, and a curing agent; the foaming agent is n-hexane or n-pentane; the foam leveling agent is dimethyl silicone oil; and the curing agent is hydrochloric acid or phosphoric acid.

[0040] The mass ratio of foaming agent: foam leveling agent: curing agent is (5-7): (2-4): (1-1.5).

[0041] In step 2), the mass ratio of the melamine porous composite film with carbon thermal conductive material as the skeleton to the flexible thermal conductive silicon layer is (500-2000):(2-20).

[0042] The flexible thermally conductive silicon layer comprises organosilicon surfactants and graphite nanoparticles.

[0043] The mass ratio of organosilicon surfactant to graphite nanoparticles is (5-16):(1-4).

[0044] The size of the graphite nanoparticles is 0.4–1 μm.

[0045] The organosilicon surfactant is at least one of polydimethylsiloxane, cyclomethylsiloxane, aminosiloxane, polymethylphenylsiloxane, and polyether polysiloxane copolymer.

[0046] The thickness of the flexible thermally conductive silicon layer is 1–10 μm.

[0047] Flexible, high thermal conductivity porous composite films are interconnected, flexible, and irregular three-dimensional porous micro / nano structures.

[0048] In step 3), the phase change material includes at least one of myristic acid, palmitic acid, decanoic acid, stearic acid, lauric acid, polyethylene glycol, paraffin / SBS, and lauric acid-stearic acid / SiO2.

[0049] The flexible, high-conductivity heat-dissipating phase change composite film with a micro / nano structure, prepared by the above method, consists of a thermally conductive network and a phase change material. The thermally conductive network is composed of a three-dimensional porous micro / nano structure formed by a flexible, thermally conductive silicon-coated carbon thermally conductive material and melamine. The phase change material fills the porous thermally conductive network. The thermally conductive network content in the flexible, high-conductivity heat-dissipating phase change composite film with a micro / nano structure is 10–60 wt%, and the phase change material content is 40–90 wt%. This flexible, high-conductivity heat-dissipating phase change composite film with a micro / nano structure possesses active heat absorption and dissipation functions. The thermal conductivity of this flexible, high-conductivity heat-dissipating phase change composite film with a micro / nano structure is 0.5–5.0 W / m·K, the phase change temperature is 30–70 °C, and the enthalpy value is 150–210 J / g.

[0050] Example 1

[0051] A method for preparing a flexible, highly conductive, heat-dissipating phase change composite thin film with a micro / nano structure includes the following steps:

[0052] 1) Under 80℃ water bath conditions, deionized water, paraformaldehyde, and melamine with a mass ratio of 71:51:60 were mixed evenly, and the total mass of the selected materials was 182g; the solution was stirred until it became clear, the pH was adjusted to 8, and the mixture was cooled to 25℃. 2g of dimethyl silicone oil (a foaming agent), 5g of n-hexane (a foaming agent), 1g of hydrochloric acid (a curing agent), and 1wt% carbon nanowires were added sequentially. The mixture was stirred thoroughly at 70℃ for 30min and placed in a mold. It was then dried in an oven at 100℃ for 45min, demolded, and the resulting porous melamine composite film with carbon thermal conductive material as the skeleton had a thickness of 2mm.

[0053] 2) 4 wt% of 1 μm graphite nanoparticles were dispersed in 10 mL of n-hexane. 16 wt% of polymethylphenylsiloxane was added to the dispersion and ultrasonically mixed for 5 min. The melamine porous composite film with carbon thermally conductive material as the skeleton obtained in step 1) was immersed in the dispersion for 15 s, removed, and dried at 75 °C for 1 h to obtain a flexible high thermal conductivity porous composite film. The mass ratio of the melamine porous composite film with carbon thermally conductive material as the skeleton to the flexible thermally conductive silicon layer was 500:20, and the thickness of the flexible thermally conductive silicon layer was 10 μm.

[0054] 3) The flexible, highly thermally conductive porous composite film obtained in step 2) is placed in the molten palmitic acid phase change material and immersed in a vacuum environment at 60°C until no more bubbles emerge from the foam, to ensure that the palmitic acid is fully immersed in the foam, thus obtaining a flexible, highly thermally conductive phase change composite film with a micro-nano structure, wherein the thermally conductive network content is 10wt% and the phase change material content is 90wt%.

[0055] The flexible, highly conductive heat-dissipating phase change composite film with micro-nano structure has a thermal conductivity of 0.5 W / m·K, a phase change temperature of 50℃, and an enthalpy of 150 J / g.

[0056] See Figure 1 This is a scanning electron microscope (SEM) image of the flexible, highly conductive, heat-dissipating phase change composite thin film with a micro / nano structure prepared in Example 1 of this invention. As can be seen from the image, the surface of the composite thin film exhibits a micrometer-scale structure covered with numerous tiny pores, resulting in a large specific surface area, which is beneficial for increasing the material's adsorption and transport properties. The structure is very stable, without significant deformation or damage, which helps maintain the film's stability and long-term performance.

[0057] See Figure 2 This image shows the measured cooling effect of the flexible, high-conductivity heat-dissipating phase change composite film with micro-nano structure prepared in Example 1 of this invention on a solar panel. As can be seen from the image, under high-temperature conditions, the temperature of the uncoated flexible, high-conductivity heat-dissipating phase change composite film with micro-nano structure is significantly higher than that of the coated film. During the heat absorption process, the phase change material undergoes a phase change, absorbing a large amount of thermal energy, thereby effectively reducing the surface temperature of the solar panel, protecting the solar panel, and extending its service life. This measured image demonstrates that the flexible, high-conductivity heat-dissipating phase change composite film with micro-nano structure has good heat dissipation and phase change energy storage performance, and can play an effective cooling role in high-temperature applications such as solar panels.

[0058] Example 2

[0059] A method for preparing a flexible, highly conductive, heat-dissipating phase change composite thin film with a micro / nano structure includes the following steps:

[0060] 1) Under 80℃ water bath conditions, deionized water, paraformaldehyde and melamine with a mass ratio of 8:6:7 were mixed evenly, and the total mass of the selected materials was 185g; the solution was stirred until it became clear, the pH was adjusted to 8, and the mixture was cooled to 25℃. Then, 3g of foaming agent dimethyl silicone oil, 6g of foaming agent n-hexane, 1g of curing agent hydrochloric acid and 3wt% carbon nanotubes were added in sequence. The mixture was stirred thoroughly at 80℃ for 25min and placed in a mold. The mixture was then dried in a 95℃ oven for 40min and demolded to obtain a porous melamine composite film with carbon thermal conductive material as the skeleton. The thickness of the porous melamine composite film with carbon thermal conductive material as the skeleton was 17mm.

[0061] 2) 4 wt% of 0.6 μm graphite nanoparticles were dispersed in 10 mL of n-hexane. 12 wt% of polydimethylsiloxane was added to the dispersion and ultrasonically mixed for 5 min. The melamine porous composite film with carbon thermally conductive material as the skeleton obtained in step 1) was immersed in the dispersion for 20 s, removed, and dried at 75 °C for 1 h to obtain a flexible high thermal conductivity porous composite film. The mass ratio of the melamine porous composite film with carbon thermally conductive material as the skeleton to the flexible thermally conductive silicon layer was 900:17, and the thickness of the flexible thermally conductive silicon layer was 7 μm.

[0062] 3) The flexible, high thermal conductivity porous composite film obtained in step 2) is placed in the stearic acid phase change material melt and immersed in the vacuum environment at 60°C until no more bubbles emerge from the foam, to ensure that the stearic acid is completely immersed in the foam, and a flexible, high thermal conductivity phase change composite film with micro-nano structure is obtained, wherein the thermally conductive network content is 28wt% and the phase change material content is 72wt%.

[0063] The flexible, high-conductivity heat-dissipating phase change composite film with micro-nano structure has a thermal conductivity of 1.6 W / m·K, a phase change temperature of 54℃, and an enthalpy of 180 J / g.

[0064] Example 3

[0065] A method for preparing a flexible, highly conductive, heat-dissipating phase change composite thin film with a micro / nano structure includes the following steps:

[0066] 1) Under 80℃ water bath conditions, deionized water, paraformaldehyde and melamine with a mass ratio of 7:5:8 were mixed evenly, and the total mass of the selected materials was 190g; the solution was stirred until it became clear, the pH was adjusted to 8, and the mixture was cooled to 25℃. 4g of foaming agent dimethyl silicone oil, 7g of foaming agent n-hexane, 1g of curing agent hydrochloric acid, and 5wt% carbon fiber nanowires were added in sequence. The mixture was stirred thoroughly at 85℃ for 20min and placed in a mold. It was then dried in a 95℃ oven for 50min to foam and cure. The material was then demolded to obtain a porous melamine composite film with carbon thermal conductive material as the skeleton. The thickness of this porous melamine composite film with carbon thermal conductive material as the skeleton was 20mm.

[0067] 2) Disperse 4 wt% of 0.4 μm graphite particles in 10 mL of n-hexane, add 11 wt% of cyclomethylsiloxane to the dispersion, and ultrasonically mix for 5 min. Immerse the melamine porous composite film with carbon thermally conductive material as the skeleton obtained in step 1) into the above dispersion for 10 s, take it out, and dry it at 75 °C for 1 h to obtain a flexible high thermal conductivity porous composite film. The mass ratio of the melamine porous composite film with carbon thermally conductive material as the skeleton to the flexible thermally conductive silicon layer is 2000:14, and the thickness of the flexible thermally conductive silicon layer is 5 μm.

[0068] 3) The flexible, highly thermally conductive porous composite film obtained in step 2) is placed in the molten lauric acid-stearic acid / SiO2 phase change material and immersed in a vacuum environment at 50°C until no more bubbles emerge from the foam, to ensure that the lauric acid-stearic acid / SiO2 is completely immersed in the foam, thus obtaining a flexible, highly thermally conductive phase change composite film with a micro-nano structure, wherein the thermally conductive network content is 60wt% and the phase change material content is 40wt%.

[0069] The flexible, high-conductivity heat-dissipating phase change composite film with micro-nano structure has a thermal conductivity of 5 W / m·K, a phase change temperature of 44℃, and an enthalpy of 175 J / g.

[0070] Example 4

[0071] A method for preparing a flexible, highly conductive, heat-dissipating phase change composite thin film with a micro / nano structure includes the following steps:

[0072] 1) Under 80℃ water bath conditions, deionized water, paraformaldehyde and melamine with a mass ratio of 10:5:7 were mixed evenly, and the total mass of the selected materials was 195g; the solution was stirred until it became clear, the pH was adjusted to 8, and the mixture was cooled to 25℃. 2g of foaming agent dimethyl silicone oil, 6g of foaming agent n-pentane, 1.5g of curing agent phosphoric acid, and 1wt% carbon fiber were added in sequence. The mixture was stirred thoroughly at 80℃ for 30min and placed in a mold. It was then foamed and cured in an oven at 105℃ for 45min. The material was demolded and discharged to obtain a porous melamine composite film with carbon thermal conductive material as the skeleton. The thickness of this porous melamine composite film with carbon thermal conductive material as the skeleton was 10mm.

[0073] 2) Disperse 1 wt% of 0.4 μm graphite nanoparticles in 10 mL of n-pentane, add 5 wt% of aminosiloxane to the dispersion, and sonicate for 5 min. Immerse the melamine porous composite film with carbon thermally conductive material as the skeleton obtained in step 1) into the dispersion for 15 s, take it out, and dry it at 75 °C for 1 h to obtain a flexible high thermal conductivity porous composite film. The mass ratio of the melamine porous composite film with carbon thermally conductive material as the skeleton to the flexible thermally conductive silicon layer is 1400:2, and the thickness of the flexible thermally conductive silicon layer is 1 μm.

[0074] 3) The flexible, highly thermally conductive porous composite film obtained in step 2) is placed in the molten myristic acid phase change material and immersed in a vacuum environment at 40°C until no more bubbles emerge from the foam, to ensure that the myristic acid is completely immersed in the foam, thus obtaining a flexible, highly thermally conductive phase change composite film with a micro-nano structure, wherein the thermally conductive network content is 45wt% and the phase change material content is 55wt%.

[0075] The flexible, high-conductivity heat-dissipating phase change composite film with micro-nano structure has a thermal conductivity of 2.3 W / m·K, a phase change temperature of 30℃, and an enthalpy of 160 J / g.

[0076] Example 5

[0077] A method for preparing a flexible, highly conductive, heat-dissipating phase change composite thin film with a micro / nano structure includes the following steps:

[0078] 1) Under 80℃ water bath conditions, deionized water, paraformaldehyde, and melamine with a mass ratio of 7:5:6 were mixed evenly, and the total mass of the selected materials was 200g; the solution was stirred until it became clear, the pH was adjusted to 9, and the mixture was cooled to 25℃. Then, 3g of foaming agent dimethyl silicone oil, 5g of foaming agent n-pentane, 1.5g of curing agent phosphoric acid, and 5wt% carbon nanowires were added in sequence. The mixture was stirred thoroughly at 85℃ for 25min and placed in a mold. The mixture was then dried in a 90℃ oven for 50min to foam and cure. The material was then demolded and discharged to obtain a porous melamine composite film with carbon thermal conductive material as the skeleton. The thickness of the porous melamine composite film with carbon thermal conductive material as the skeleton was 8mm.

[0079] 2) Disperse 2 wt% of 1 μm graphite nanoparticles in 10 mL of n-pentane, add 16 wt% of polyether polysiloxane to the dispersion, and ultrasonically mix for 5 min. Immerse the melamine porous composite film with carbon thermally conductive material as the skeleton obtained in step 1) into the dispersion for 15 s, take it out, and dry it at 75 °C for 1 h to obtain a flexible high thermal conductivity porous composite film. The mass ratio of the melamine porous composite film with carbon thermally conductive material as the skeleton to the flexible thermally conductive silicon layer is 1600:15, and the thickness of the flexible thermally conductive silicon layer is 8 μm.

[0080] 3) The flexible, high thermal conductivity porous composite film obtained in step 2) is placed in the molten polyethylene glycol phase change material and immersed in a vacuum environment at 75°C until no more bubbles emerge from the foam, to ensure that the polyethylene glycol is completely immersed in the foam, thus obtaining a flexible, high thermal conductivity phase change composite film with a micro-nano structure, wherein the thermally conductive network content is 25wt% and the phase change material content is 75wt%.

[0081] The flexible, high-conductivity heat-dissipating phase change composite film with micro-nano structure has a thermal conductivity of 1.1 W / m·K, a phase change temperature of 70℃, and an enthalpy of 210 J / g.

[0082] This invention proposes a flexible, highly conductive, heat-dissipating phase change composite film with a micro / nano structure, its preparation method, and its applications. The prepared flexible, highly conductive, heat-dissipating phase change composite film with a micro / nano structure exhibits low direct contact thermal resistance with the photovoltaic backsheet, good thermal conductivity in the macroscopic vertical direction, and a large latent heat of phase change, which can significantly improve the overall heat dissipation capacity of photovoltaic modules. The obtained flexible phase change composite film has active heat absorption and dissipation functions, strong weather resistance, and is particularly suitable for cooling and thermal management of outdoor photovoltaic modules and 5G base station components, improving device efficiency. Moreover, the preparation method allows for controllable reaction conditions, low equipment requirements, and is suitable for large-scale production.

[0083] All the raw materials listed in this invention, as well as the upper and lower limits and ranges of the raw materials and the upper and lower limits and ranges of the process parameters, can realize this invention. They will not be listed one by one here.

[0084] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A flexible, highly conductive, heat-dissipating phase change composite thin film with a micro / nano structure, characterized in that, It consists of a thermally conductive network and a phase change material filled in the thermally conductive network; the mass percentage of the thermally conductive network is 10%~60%, and the mass percentage of the phase change material is 40%~90%; the thermally conductive network is a three-dimensional porous micro-nano structure, formed by a flexible thermally conductive silicon layer coated with carbon thermally conductive material and melamine; The method for preparing the flexible, highly conductive, heat-dissipating phase change composite thin film with micro / nano structure includes the following steps: 1) Mix and disperse the cosolvent and melamine in water, then add additives and carbon thermal conductive material in sequence. After foaming and curing, a porous melamine composite film with carbon thermal conductive material as the skeleton is obtained. 2) Modify the surface of the melamine porous composite film with carbon thermally conductive material as the skeleton obtained in step 1) with a flexible thermally conductive silicon layer to obtain a flexible high thermal conductivity porous composite film. 3) Fill the flexible, highly thermally conductive porous composite film obtained in step 2) with phase change material to obtain a flexible, highly thermally conductive phase change composite film with micro-nano structure. In step 1), the mass ratio of the co-solvent: melamine: additive: carbon thermal conductive material is (100~140):(120~160):(1~14):(2~10); the carbon thermal conductive material is any one of carbon nanowires, carbon fibers and carbon nanotubes; the co-solvent is paraformaldehyde; In step 2), the mass ratio of the melamine porous composite film with carbon thermally conductive material as the skeleton to the flexible thermally conductive silicon layer is (500~2000):(2~20); the flexible thermally conductive silicon layer includes graphite nanoparticles and organosilicon surfactants; the mass ratio of graphite nanoparticles to organosilicon surfactants is (1~4):(5~16); the size of the graphite nanoparticles is 0.4~1 μm; the organosilicon surfactant is at least one of polydimethylsiloxane, cyclomethylsiloxane, aminosiloxane, polymethylphenylsiloxane, and polyether polysiloxane copolymer. In step 3), the phase change material is at least one of myristic acid, palmitic acid, decanoic acid, stearic acid, lauric acid, polyethylene glycol, paraffin / SBS, and lauric acid-stearic acid / SiO2.

2. The flexible, highly conductive, heat-dissipating phase change composite thin film with a micro / nano structure according to claim 1, characterized in that, The flexible, high-conductivity heat-dissipating phase change composite film with micro-nano structure has a thermal conductivity of 0.5~5.0 W / m·K, a phase change temperature of 30~70℃, and an enthalpy of 150~210 J / g.

3. The flexible, high-conductivity heat-dissipating phase change composite thin film with micro / nano structure according to claim 1, characterized in that, In step 1), the dispersion conditions are stirring at 70-85℃ for 20-30 minutes, and the foaming conditions are stirring at 90-105℃ for 40-50 minutes.

4. The flexible, high-conductivity heat-dissipating phase change composite thin film with micro / nano structure according to claim 1, characterized in that, In step 1), the content of the carbon thermal conductive material is 1-5 wt% of the melamine content; the additives include a foaming agent, a foam leveling agent, and a curing agent; the mass ratio of the foaming agent: foam leveling agent: curing agent is (5-7):(2-4):(1-1.5), the foaming agent is n-hexane or n-pentane; the foam leveling agent is dimethyl silicone oil; the curing agent is hydrochloric acid or phosphoric acid.

5. The flexible, highly conductive, heat-dissipating phase change composite thin film with a micro / nano structure according to claim 1, characterized in that, In step 1), the thickness of the melamine porous composite film with carbon thermal conductive material as the skeleton is 2~20 mm.

6. The flexible, highly conductive, heat-dissipating phase change composite thin film with a micro / nano structure according to claim 1, characterized in that, In step 2), the thickness of the flexible thermally conductive silicon layer is 1~10 μm; the flexible high thermal conductivity porous composite film is a connected, flexible, irregular three-dimensional porous micro-nano structure film.

7. The application of the flexible, high-conductivity heat-dissipating phase change composite thin film with micro-nano structure as described in any one of claims 1 to 6 in the preparation of outdoor photovoltaic modules and 5G base station components.

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