An asymmetric thermal management composite film with thermal resistance structure and its preparation method and application

Abstract

This application discloses an asymmetric thermal management composite membrane with a thermal resistance structure, its preparation method, and its application. The composite membrane includes a heat insulation layer, a transition layer, and a heat dissipation layer. The heat insulation layer comprises the following raw materials in parts by weight: 10-30 parts graphene, 0.5-4.5 parts dopamine hydrochloride, 70-90 parts polyamic acid, and 5-10 parts hexagonal boron nitride. The transition layer comprises the following raw materials in parts by weight: 40-60 parts graphene, 4-6 parts dopamine hydrochloride, 40-60 parts polyamic acid, 10-20 parts hexagonal boron nitride, 10-15 parts elastomer, and 1-1.5 parts silane coupling agent. The heat dissipation layer comprises the following raw materials in parts by weight: 80-90 parts graphene, 8-9 parts dopamine hydrochloride, 10-20 parts polyamic acid, 20-30 parts hexagonal boron nitride, and 1-1.5 parts silane coupling agent. This application exhibits highly efficient heat insulation and excellent heat dissipation.

Description

Technical Field

[0001] This application relates to the field of heat dissipation technology for electronic devices, and in particular to an asymmetric thermal management composite film with a thermal resistance structure, its preparation method, and its application. Background Technology

[0002] As electronic devices, new energy vehicle battery packs, and high-power consumer electronics (such as curling irons and fast chargers) continue to evolve towards higher power density, miniaturization, and integration, their internal thermal management issues are becoming increasingly acute, becoming a core bottleneck restricting performance improvement and user experience. The essence of this contradiction lies in the fact that the core heat-generating components inside the device (such as chips, power devices, batteries, and heating elements) generate a large amount of Joule heat during operation. If this heat cannot be dissipated in time, it will lead to performance degradation, shortened lifespan, or even thermal failure. At the same time, the device casing, user contact surfaces, or nearby low-temperature sensitive components need to be kept at a low temperature to prevent burns, ensure grip comfort, and protect surrounding materials.

[0003] To meet the combined requirement of "heat dissipation on one side and heat insulation on the other," the current mainstream solution in the industry is to physically composite single-function materials. A typical approach is a "double-layer bonding" structure: this involves combining high thermal conductivity materials (such as graphene films and metal-based composites) with high-performance thermal insulation materials (such as aerogels and polyimide foams) using adhesives or physical pressing. The thermally conductive layer is responsible for contacting the heat source and enabling rapid lateral heat diffusion, while the thermal insulation layer blocks heat transfer to the outside.

[0004] However, this multilayered heterogeneous structure has inherent drawbacks. First, due to the differences in the coefficients of thermal expansion of the materials in each layer, cumulative thermal stress easily accumulates at the interfaces during the thermal cycling caused by frequent equipment start-ups, shutdowns, or load switching. This stress accelerates the aging and failure of the adhesive layers, leading to interface delamination and detachment, ultimately resulting in the loss of thermal management functionality and severely impacting product reliability and lifespan. Second, the clearly defined physical interfaces themselves introduce significant contact thermal resistance, hindering efficient heat transfer from the heat source to the heat dissipation side. More critically, this structure makes precise control of heat flow difficult: heat may accumulate unintended in the insulation layer or leak from the thermally conductive layer into areas that should be insulated. This thermal crosstalk prevents the maximization of heat dissipation efficiency, significantly reducing the insulation effect.

[0005] Therefore, there is an urgent need to develop a new type of thermal management material that combines excellent thermal insulation with efficient heat dissipation. Summary of the Invention

[0006] This application provides an asymmetric thermal management composite film with a thermal resistance structure, its preparation method, and its application, which can solve the problem of integrating heat insulation and heat dissipation in thermal management materials.

[0007] In a first aspect, this application provides an asymmetric thermal management composite film with a thermal resistance structure, employing the following technical solution: An asymmetric thermal management composite membrane with a thermal resistance structure includes a heat insulation layer, a transition layer, and a heat dissipation layer. The heat insulation layer comprises the following raw materials in parts by weight: 10-30 parts graphene, 0.5-4.5 parts dopamine hydrochloride, 70-90 parts polyamic acid, and 5-10 parts hexagonal boron nitride. The transition layer comprises the following raw materials in parts by weight: 40-60 parts graphene, 4-6 parts dopamine hydrochloride, 40-60 parts polyamic acid, 10-20 parts hexagonal boron nitride, 10-15 parts elastomer, and 1-1.5 parts silane coupling agent. The heat dissipation layer comprises the following raw materials in parts by weight: 80-90 parts graphene, 8-9 parts dopamine hydrochloride, 10-20 parts polyamic acid, 20-30 parts hexagonal boron nitride, and 1-1.5 parts silane coupling agent.

[0008] By employing the above technical solution, an asymmetric composite film with a gradient increase in thermal conductivity was constructed. First, through the design of gradient contents of graphene and polyamic acid in the insulation layer, transition layer, and heat dissipation layer (graphene content increases layer by layer, polyamic acid content decreases layer by layer), combined with the construction of a hexagonal boron nitride thermally conductive network, a continuous transition structure from the "insulating matrix" to the "thermally conductive network" was formed in the thickness direction. Second, the self-polymerization modification of dopamine hydrochloride effectively reduced the surface energy of graphene, inhibited its aggregation, and enhanced the interfacial compatibility with the polyimide matrix. At the same time, the silane coupling agent further strengthened the chemical bond between the inorganic filler and the organic matrix, significantly reducing the interfacial thermal resistance. The elastomer introduced in the transition layer effectively buffered the interfacial thermal stress caused by the huge difference in thermal conductivity and thermal expansion coefficient between the upper and lower layers using its flexible chain segments. The synergistic effect of the above components enables the composite film to combine the rapid heat diffusion capability of a high thermal conductivity layer (heat dissipation layer) with the thermal barrier properties of a low thermal conductivity layer (heat insulation layer) in the thickness direction. The transition layer enables a smooth heat flow transition, thereby avoiding local heat concentration and achieving efficient and directional thermal management.

[0009] Optionally, the elastomer includes at least one of thermoplastic polyurethane elastomer and methyl vinyl silicone rubber.

[0010] By adopting the above technical solution, this application selects thermoplastic polyurethane elastomer and methyl vinyl silicone rubber as elastomers. The thermoplastic polyurethane elastomer, with its excellent flexibility and good compatibility with the polyimide matrix, forms a flexible network in the transition layer, effectively buffering the interfacial thermal stress caused by the large difference in thermal conductivity between the insulation layer and the heat dissipation layer. Meanwhile, methyl vinyl silicone rubber, with its excellent high and low temperature stability and low surface energy characteristics, promotes uniform dispersion of fillers and inhibits excessive aggregation of the elastomer phase during processing, while providing reversible deformation recovery capability when the composite film is subjected to thermal shock.

[0011] Optionally, the elastomer comprises thermoplastic polyurethane elastomer and methyl vinyl silicone rubber, wherein the weight ratio of the thermoplastic polyurethane elastomer to the methyl vinyl silicone rubber is (2-4):1.

[0012] By adopting the above technical solution, this application uses a specific weight ratio of thermoplastic polyurethane elastomer and silicone rubber to ensure that the thermoplastic polyurethane elastomer forms a continuous and tough stress buffer network in the polyimide matrix, effectively dissipating the interfacial shear stress caused by the huge difference in thermal expansion coefficient and thermal conductivity between the insulation layer and the heat dissipation layer; while silicone rubber, as a secondary phase, with its excellent compliant segments and low glass transition temperature, on the one hand, acts as a softener of "stress concentration points" in the blend system, avoiding interfacial delamination caused by excessively high modulus of the elastomer phase, and on the other hand, utilizes its low surface energy characteristics to promote the uniform spreading of fillers in the transition layer.

[0013] Optionally, the weight ratio of graphene to dopamine hydrochloride in the transition layer is (8-10):1.

[0014] By adopting the above technical solution, this application uses a specific weight ratio of graphene and dopamine hydrochloride, which can effectively reduce the difference in interlayer interface energy, avoid delamination or peeling defects caused by abrupt changes in hydrophilicity or hydrophobicity, and ensure that heat is not reflected or accumulated due to drastic fluctuations in interfacial thermal resistance during cross-interface transfer. This strengthens the integrity of the asymmetric structure and the continuity of heat flow conduction at the microscale. Specifically, at this ratio, dopamine hydrochloride can completely coat the graphene surface through a self-polymerized polydopamine layer, significantly enhancing its interfacial compatibility with the polyimide matrix and inhibiting graphene aggregation, while also preventing the formation of defects in the matrix by dopamine self-polymers.

[0015] Optionally, the particle size of hexagonal boron nitride in the heat insulation layer is 1-5 μm, the particle size of hexagonal boron nitride in the transition layer is 5-10 μm, and the particle size of hexagonal boron nitride in the heat dissipation layer is 100-200 nm.

[0016] By adopting the above technical solutions, the heat insulation layer uses 1-5μm micron-sized hexagonal boron nitride, which effectively suppresses heat conduction by utilizing the interfacial scattering effect between large-diameter particles, significantly improving the heat insulation performance of the heat insulation layer; the transition layer uses 5-10μm hexagonal boron nitride, which works in conjunction with thermoplastic polyurethane elastomer to construct a gradient buffer structure, which can both relieve thermal stress and provide a bridge for heat flow transition; the heat dissipation layer uses 100-200nm nano-sized hexagonal boron nitride, whose high specific surface area and dense filling characteristics greatly enhance the continuity of the heat conduction path, significantly improving the thermal conductivity of the heat dissipation layer; the gradient design of the three-layer particle size not only forms a dual synergy with the component gradient, further eliminating interlayer interfaces and optimizing the directional heat flow conduction path, but also effectively alleviates thermal expansion mismatch through multi-scale construction, greatly improving the structural stability and long-term reliability of the composite film under thermal cycling.

[0017] Optionally, the thickness of the heat insulation layer is 250-350μm, the thickness of the transition layer is 50-100μm, and the thickness of the heat dissipation layer is 100-150μm.

[0018] By adopting the above technical solution, this application controls the thickness of the heat insulation layer, the transition layer and the heat dissipation layer within the range of 250-350μm, 50-100μm and 100-150μm respectively, which can achieve synergistic optimization of thermal resistance function and mechanical stability. The 250-350μm insulation layer utilizes its low thermal conductivity to construct an effective thermal barrier, significantly extending the heat flow path to block heat transfer to non-target directions. The 50-100μm transition layer acts as a stress buffer zone, completing the gradient transition of thermal conductivity within a very small space, avoiding the introduction of additional thermal resistance or exacerbation of interlayer thermal mismatch due to excessive thickness. The 100-150μm heat dissipation layer ensures sufficient in-plane heat diffusion capacity while preventing the thermal accumulation effect caused by excessive layer thickness. The three layers have a gradient distribution of thickness from thick to thin to medium, which not only ensures the structural strength and processing flatness of the overall membrane material, but also amplifies the heat flow guiding function of the asymmetric structure through precise spatial design, enabling the composite membrane to achieve integrated thermal management of "high-efficiency insulation, stress relief, and rapid heat dissipation" in the vertical direction.

[0019] Optionally, the silane coupling agent in the transition layer and the heat dissipation layer is γ-aminopropyltriethoxysilane.

[0020] By adopting the above technical solution, γ-aminopropyltriethoxysilane is selected as a silane coupling agent. The amino functional groups in its molecular structure can react with polyamic acid and thermoplastic polyurethane elastomers or form hydrogen bonds, while the ethoxy groups can be hydrolyzed and condensed with the hydroxyl groups on the surface of graphene and hexagonal boron nitride, thereby forming a strong chemical bridge between the organic polymer matrix and the inorganic filler. This significantly improves the interfacial compatibility and dispersion uniformity of the components in the transition layer and heat dissipation layer. This enhanced interfacial bonding not only effectively reduces the interfacial thermal resistance between the filler and the matrix, making the heat conduction network more complete, but also improves the mechanical strength and structural density of the composite film through chemical bonding force. During the thermal cycling process, it can better suppress microcracks or interfacial delamination caused by the difference in thermal expansion coefficients, thereby ensuring the long-term stability of the directional heat flow conduction path.

[0021] Secondly, this application provides a method for preparing an asymmetric thermal management composite film with a thermal resistance structure, using the following technical solution: A method for preparing an asymmetric thermal management composite film with a thermal resistance structure includes the following steps: S1. Mix graphene, dopamine hydrochloride and tris(hydroxymethyl)aminomethane hydrochloride buffer solution and stir until homogeneous to obtain graphene dispersion; S2. Mix the graphene dispersion, hexagonal boron nitride and solvent, disperse by ultrasonication, add polyamic acid, and stir evenly to obtain slurry A; S3. Mix the graphene dispersion, hexagonal boron nitride and solvent, disperse by ultrasonication, add silane coupling agent, heat to reflux, then add polyamic acid and elastomer, stir evenly to obtain slurry B; S4. Mix the graphene dispersion, hexagonal boron nitride and solvent, disperse by ultrasonication, add silane coupling agent, heat under reflux, then add polyamic acid, stir evenly to obtain slurry C; S5. Inject the slurry A into the mold, freeze it, then inject the slurry B and slurry C in sequence, freeze dry, heat treat, and hot press to obtain an asymmetric thermal management composite membrane with a thermal resistance structure.

[0022] Optionally, the solvent is N-methylpyrrolidone.

[0023] Optionally, in step S1, the power of ultrasonic dispersion is 400-600W.

[0024] Optionally, in step S2, the ultrasonic dispersion power is 400-600W, and the stirring speed is 100-300rpm.

[0025] Optionally, in step S3, the ultrasonic dispersion power is 200-400W, and the heating reflux temperature is 60-80℃.

[0026] Optionally, in step S4, the ultrasonic dispersion power is 300-500W, and the heating reflux temperature is 70-90℃.

[0027] Optionally, in step S5, the freezing temperature is -50~-30℃, the heating treatment temperature is 200-300℃, and the hot pressing temperature is 300-400℃.

[0028] Thirdly, this application provides an application of an asymmetric thermal management composite film with a thermal resistance structure in heat dissipation of electronic devices.

[0029] In summary, this application includes at least one of the following beneficial technical effects: 1. This application constructs an asymmetric composite film with a gradient increase in thermal conductivity. First, by designing a gradient content of graphene and polyamic acid in the insulation layer, transition layer, and heat dissipation layer (graphene content increases layer by layer, polyamic acid content decreases layer by layer), and constructing a thermally conductive network of hexagonal boron nitride, a continuous transition structure from the "insulating matrix" to the "thermally conductive network" is formed in the thickness direction. Second, the self-polymerization modification of dopamine hydrochloride effectively reduces the surface energy of graphene, inhibits its aggregation, and enhances the interfacial compatibility with the polyimide matrix. At the same time, the silane coupling agent further strengthens the chemical bond between the inorganic filler and the organic matrix, significantly reducing the interfacial thermal resistance. The elastomer introduced in the transition layer effectively buffers the interfacial thermal stress caused by the huge difference in thermal conductivity and thermal expansion coefficient between the upper and lower layers using its flexible segments. The synergistic effect of the above components enables the composite film to combine the rapid heat diffusion capability of a high thermal conductivity layer (heat dissipation layer) with the thermal barrier properties of a low thermal conductivity layer (heat insulation layer) in the thickness direction. The transition layer enables a smooth heat flow transition, thereby avoiding local heat concentration and achieving efficient and directional thermal management. 2. This application uses a combination of thermoplastic polyurethane elastomer and silicone rubber, which can improve the stress dissipation efficiency of the transition layer while avoiding the risk of interfacial delamination caused by excessively high or low modulus of a single elastomer. The thermoplastic polyurethane elastomer, with its excellent flexibility and good compatibility with the polyimide matrix, forms a flexible network in the transition layer, effectively buffering the interfacial thermal stress caused by the large difference in thermal conductivity between the insulation layer and the heat dissipation layer. Meanwhile, the silicone rubber, with its excellent high and low temperature stability and low surface energy characteristics, promotes uniform dispersion of fillers and inhibits excessive aggregation of the elastomer phase during processing, while providing reversible deformation recovery capability when the composite film is subjected to thermal shock. 3. This application employs a specific weight ratio of graphene and dopamine hydrochloride, which effectively reduces the interfacial energy difference between layers, avoids delamination or peeling defects caused by abrupt changes in hydrophilicity or hydrophobicity, and ensures that heat transfer across the interface does not result in reflection or accumulation due to drastic fluctuations in interfacial thermal resistance. This, in turn, enhances the integrity of the asymmetric structure and the continuity of heat flow at the microscale. Specifically, at this ratio, dopamine hydrochloride can completely coat the graphene surface through a self-polymerized polydopamine layer, significantly enhancing its interfacial compatibility with the polyimide matrix and inhibiting graphene aggregation, while also preventing the formation of defects in the matrix by dopamine self-polymers. 4. The thermal insulation layer uses 1-5μm micron-sized hexagonal boron nitride, which effectively suppresses heat conduction by utilizing the interfacial scattering effect between large-diameter particles, significantly improving the thermal insulation performance of the thermal insulation layer; the transition layer uses 5-10μm hexagonal boron nitride, which works in conjunction with thermoplastic polyurethane elastomer to construct a gradient buffer structure, which can both relieve thermal stress and provide a bridge for heat flow transition; the heat dissipation layer uses 100-200nm nano-sized hexagonal boron nitride, whose high specific surface area and dense filling characteristics greatly enhance the continuity of the heat conduction path, significantly improving the thermal conductivity of the heat dissipation layer; the gradient design of the three-layer particle size not only forms a dual synergy with the component gradient, further eliminating interlayer interfaces and optimizing the directional heat flow conduction path, but also effectively alleviates thermal expansion mismatch through multi-scale construction, greatly improving the structural stability and long-term reliability of the composite film under thermal cycling. Attached Figure Description

[0030] Figure 1 This is a heat dissipation surface view of the asymmetric thermal management composite film with a thermal resistance structure in Embodiment 2 of this application; Figure 2 This is a thermal insulation surface view of the asymmetric thermal management composite membrane with a thermal resistance structure according to Embodiment 1 of this application. Detailed Implementation

[0031] The technical solutions of the present invention will be clearly and completely described below with reference to 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0032] This application discloses an asymmetric thermal management composite membrane with a thermal resistance structure, comprising a heat insulation layer, a transition layer, and a heat dissipation layer. The heat insulation layer comprises the following raw materials in parts by weight: 10-30 parts graphene, 0.5-4.5 parts dopamine hydrochloride, 70-90 parts polyamic acid, and 5-10 parts hexagonal boron nitride. The transition layer comprises the following raw materials in parts by weight: 40-60 parts graphene, 4-6 parts dopamine hydrochloride, 40-60 parts polyamic acid, 10-20 parts hexagonal boron nitride, 10-15 parts elastomer, and 1-1.5 parts silane coupling agent. The heat dissipation layer comprises the following raw materials in parts by weight: 80-90 parts graphene, 8-9 parts dopamine hydrochloride, 10-20 parts polyamic acid, 20-30 parts hexagonal boron nitride, and 1-1.5 parts silane coupling agent.

[0033] This application discloses a method for preparing an asymmetric thermal management composite film with a thermal resistance structure, comprising the following steps: S1. Mix graphene, dopamine hydrochloride and tris(hydroxymethyl)aminomethane hydrochloride buffer, and sonicate at 400-600W for 10-20 minutes to obtain graphene dispersion. S2. Mix the graphene dispersion, hexagonal boron nitride and solvent, ultrasonically disperse at 400-600W for 10-20 min, add polyamic acid, and stir at 100-300 rpm for 20-30 min to obtain slurry A; S3. Mix the graphene dispersion, hexagonal boron nitride and solvent, ultrasonically disperse at 200-400W for 20-30 minutes, add silane coupling agent, heat and reflux at 60-80℃ for 2-4 hours, then add polyamic acid and elastomer, stir at 400-600rpm for 30-60 minutes to obtain slurry B. S4. Mix the graphene dispersion, hexagonal boron nitride and solvent, ultrasonically disperse at 300-500W for 20-30 minutes, add silane coupling agent, heat and reflux at 70-90℃ for 5-6 hours, then add polyamic acid, stir at 300-500rpm for 10-20 minutes to obtain slurry C. S5. Inject the slurry A into the mold and freeze it at -50~-30℃. Then, inject the slurry B and slurry C in sequence, freeze-dry at -50~-30℃ for 1-2 days, heat-treat at 200-300℃ for 1-3 hours, and hot-press the slurry A side at 8-12MPa and 300-400℃ for 10-30 minutes to obtain an asymmetric thermal management composite membrane with a thermal resistance structure.

[0034] All raw materials used in the embodiments of this application are commercially available, wherein: Graphene, Shanghai McLean Biochemical Technology Co., Ltd. Dopamine hydrochloride, Shanghai Aladdin Biochemical Technology Co., Ltd. Thermoplastic polyurethane elastomers, Shanghai Lianjing Polymer Materials Co., Ltd.; Methyl vinyl silicone rubber, Shenzhen Muwei Technology Co., Ltd.; Tris-HCl buffer, 10 mM, pH 8.5, Shanghai Maclean Biotechnology Co., Ltd. N-Methylpyrrolidone, Shanghai Maclean Biochemical Technology Co., Ltd.; γ-aminopropyltriethoxysilane, Shanghai Maclean Biochemical Technology Co., Ltd. Polyamic acid, Jiangsu Junhua Special Polymer Materials Co., Ltd.; Hexagonal boron nitride, particle size 1-5μm, 5-10μm, 100-200nm, Xi'an Qiyue Biotechnology Co., Ltd.

[0035] Example 1 S1. Mix 10g graphene, 1g dopamine hydrochloride and 100mL Tris-HCl buffer, and sonicate at 400W for 10min to obtain graphene dispersion A1; mix 40g graphene, 4g dopamine hydrochloride and 400mL Tris-HCl buffer, and sonicate at 400W for 10min to obtain graphene dispersion B1; mix 80g graphene, 8g dopamine hydrochloride and 800mL Tris-HCl buffer, and sonicate at 400W for 10min to obtain graphene dispersion C1. S2. Mix graphene dispersion A1, 5g hexagonal boron nitride (particle size 1-5μm) and 50mL N-methylpyrrolidone, ultrasonically disperse at 400W for 10min, add 70g polyamic acid, stir at 100rpm for 20min to obtain slurry A; S3. Mix graphene dispersion B1, 10g hexagonal boron nitride (particle size 5-10μm) and 100mL N-methylpyrrolidone, sonicate at 200W for 20min, add 1g γ-aminopropyltriethoxysilane, heat and reflux at 60℃ for 2h, then add 40g polyamic acid and 10g thermoplastic polyurethane elastomer, stir at 400rpm for 30min to obtain slurry B; S4. Mix graphene dispersion C1, 20g hexagonal boron nitride (particle size 100-200nm) and 200mL N-methylpyrrolidone, sonicate at 300W for 20min, add 1g γ-aminopropyltriethoxysilane, heat under reflux at 70℃ for 5h, then add 10g polyamic acid, stir at 300rpm for 10min to obtain slurry C; S5. Inject slurry A into the mold and freeze at -50℃ to form a heat insulation layer with a thickness of 250μm. Then inject slurry B and freeze at -50℃ to form a transition layer with a thickness of 50μm. Then inject slurry C and freeze at -50℃ to form a heat dissipation layer with a thickness of 100μm. Freeze-dry at -50℃ for 1 day, heat-treat at 200℃ for 1 hour, and hot-press the slurry A side at 8MPa and 300℃ for 10 minutes to obtain an asymmetric thermal management composite film with a thermal resistance structure (the thickness of the heat insulation layer is 250μm, the thickness of the transition layer is 50μm, and the thickness of the heat dissipation layer is 100μm).

[0036] Example 2 S1. Mix 20g graphene, 2g dopamine hydrochloride and 200mL Tris-HCl buffer, and sonicate at 500W for 15min to obtain graphene dispersion A2; mix 50g graphene, 5g dopamine hydrochloride and 500mL Tris-HCl buffer, and sonicate at 500W for 15min to obtain graphene dispersion B2; mix 85g graphene, 8.5g dopamine hydrochloride and 850mL Tris-HCl buffer, and sonicate at 500W for 15min to obtain graphene dispersion C2. S2. Mix graphene dispersion A2, 7.5g hexagonal boron nitride (particle size 1-5μm) and 75mL N-methylpyrrolidone, ultrasonically disperse at 500W for 15min, add 80g polyamic acid, stir at 200rpm for 25min to obtain slurry A; S3. Mix graphene dispersion B2, 15g hexagonal boron nitride (particle size 5-10μm) and 150mL N-methylpyrrolidone, sonicate at 300W for 25min, add 1.25g γ-aminopropyltriethoxysilane, heat under reflux at 70℃ for 3h, then add 50g polyamic acid and 12.5g thermoplastic polyurethane elastomer, stir at 500rpm for 45min to obtain slurry B; S4. Mix graphene dispersion C2, 25g hexagonal boron nitride (particle size 100-200nm) and 250mL N-methylpyrrolidone, sonicate at 400W for 25min, add 1.25g γ-aminopropyltriethoxysilane, heat under reflux at 80℃ for 5.5h, then add 15g polyamic acid, stir at 400rpm for 15min to obtain slurry C; S5. Inject slurry A into the mold and freeze at -40℃ to form a heat insulation layer with a thickness of 300μm. Then inject slurry B and freeze at -40℃ to form a transition layer with a thickness of 75μm. Then inject slurry C and freeze at -40℃ to form a heat dissipation layer with a thickness of 125μm. Freeze-dry at -40℃ for 1.5 days, heat-treat at 250℃ for 2 hours, and hot-press the heat insulation layer side at 10MPa and 350℃ for 20 minutes to obtain an asymmetric thermal management composite film with a thermal resistance structure (the thickness of the heat insulation layer is 300μm, the thickness of the transition layer is 75μm, and the thickness of the heat dissipation layer is 125μm).

[0037] Example 3 S1. Mix 30g graphene, 3g dopamine hydrochloride and 300mL Tris-HCl buffer, and sonicate at 600W for 20min to obtain graphene dispersion A3; mix 60g graphene, 6g dopamine hydrochloride and 600mL Tris-HCl buffer, and sonicate at 600W for 20min to obtain graphene dispersion B3; mix 90g graphene, 9g dopamine hydrochloride and 900mL Tris-HCl buffer, and sonicate at 600W for 20min to obtain graphene dispersion C3. S2. Mix graphene dispersion A3, 10g hexagonal boron nitride (particle size 1-5μm) and 100mL N-methylpyrrolidone, ultrasonically disperse at 600W for 20min, add 90g polyamic acid, stir at 300rpm for 30min to obtain slurry A; S3. Mix graphene dispersion B3, 20g hexagonal boron nitride (particle size 5-10μm) and 200mL N-methylpyrrolidone, sonicate at 400W for 30min, add 1.5g γ-aminopropyltriethoxysilane, heat and reflux at 80℃ for 4h, then add 60g polyamic acid and 15g thermoplastic polyurethane elastomer, stir at 600rpm for 60min to obtain slurry B; S4. Mix graphene dispersion C3, 30g hexagonal boron nitride (particle size 100-200nm) and 300mL N-methylpyrrolidone, sonicate at 500W for 30min, add 1.5g γ-aminopropyltriethoxysilane, heat under reflux at 90℃ for 6h, then add 20g polyamic acid, stir at 500rpm for 20min to obtain slurry C; S5. Inject slurry A into the mold and freeze at -30℃ to form a heat insulation layer with a thickness of 350μm. Then inject slurry B and freeze at -30℃ to form a transition layer with a thickness of 100μm. Then inject slurry C and freeze at -30℃ to form a heat dissipation layer with a thickness of 150μm. Freeze-dry at -30℃ for 2 days, heat-treat at 300℃ for 3 hours, and hot-press the heat insulation layer side at 12MPa and 400℃ for 30 minutes to obtain an asymmetric thermal management composite film with a thermal resistance structure (the thickness of the heat insulation layer is 350μm, the thickness of the transition layer is 100μm, and the thickness of the heat dissipation layer is 150μm).

[0038] Comparative Example 1 The difference between this comparative example and Example 2 is that the mass of dopamine hydrochloride in Example 2 is replaced with graphene in this comparative example.

[0039] Comparative Example 2 The difference between this comparative example and Example 2 is that the graphene in Example 2 is replaced with dopamine hydrochloride in this comparative example.

[0040] Performance Test 1 The thermal conductivity and thermal shock properties of the asymmetric thermal management composite films with thermal resistance structures prepared in Examples 1-3 and Comparative Examples 1-2 were tested, and the results are shown in Table 1.

[0041] Thermal conductivity: The thermal conductivity of the insulation layer side and the heat dissipation layer side was tested in accordance with GB / T 10294-2008 "Determination of steady-state thermal resistance and related properties of thermal insulation materials - protective hot plate method".

[0042] Thermal shock test: The composite membrane is placed in a temperature chamber ranging from -40℃ to 200℃ and cycled 1000 times. Then, micro-CT is used to observe whether there is delamination, cracks, or blistering inside.

[0043] Table 1. Performance of the composites of Examples 1-3 and Comparative Examples 1-2

[0044] As shown in Examples 1-3 and Table 1, the thermal conductivity of the asymmetric thermal management composite membrane with thermal resistance structure of this application is below 0.07 W / m / K on the insulation layer side and above 112 W / m / K on the heat dissipation layer side. No delamination was observed in the thermal shock test. This indicates that by designing the gradient content of graphene and polyamic acid in the insulation layer, transition layer and heat dissipation layer, synergistically constructing the thermally conductive network of hexagonal boron nitride, and modifying the filler interface with dopamine hydrochloride, an asymmetric structure with gradually increasing thermal conductivity can be formed, enabling the composite membrane to have both high-efficiency thermal conductivity and excellent heat dissipation.

[0045] As shown in Example 2, Comparative Examples 1-2, and Table 1, the thermal conductivity of the asymmetric thermal management composite film with a thermal resistance structure in Example 2 of this application is 0.05 W / m / K on the insulation layer side and 120 W / m / K on the heat dissipation layer side. No delamination was observed during thermal shock testing, significantly better than Comparative Examples 1-2. This indicates that coating the graphene surface with dopamine hydrochloride enhances its interfacial compatibility with the polyimide matrix and inhibits graphene aggregation, effectively reducing interlayer interfacial energy differences and avoiding delamination or peeling defects caused by abrupt changes in hydrophilicity or hydrophobicity. Compared to Example 2, the pure graphene in Comparative Example 1 is prone to aggregation, forming localized thermal conductivity pathways and thus compromising the insulation effect. Compared to Example 2, the pure dopamine hydrochloride in Comparative Example 2 lacks highly efficient thermally conductive fillers, easily becoming stress concentration points during thermal cycling, leading to blistering and delamination.

[0046] Example 4 The difference between this embodiment and Embodiment 2 is that in this embodiment, the thermoplastic polyurethane elastomer in Embodiment 2 is replaced by methyl vinyl silicone rubber.

[0047] Example 5 The difference between this embodiment and Embodiment 2 is that in this embodiment, 12.5g of thermoplastic polyurethane elastomer in Embodiment 2 is replaced with 6.25g of thermoplastic polyurethane elastomer and 6.25g of methyl vinyl silicone rubber.

[0048] Examples 6-7 Based on Example 5, except for the weight ratio of thermoplastic polyurethane elastomer and methyl vinyl silicone rubber, the other components and preparation methods are the same as in Example 5, and the total weight of thermoplastic polyurethane elastomer and methyl vinyl silicone rubber remains unchanged.

[0049] Example 6 The difference between this embodiment and embodiment 5 is that the weight ratio of thermoplastic polyurethane elastomer to methyl vinyl silicone rubber in this embodiment is 2:1. Specifically, the weight of thermoplastic polyurethane elastomer is 8.33g and the weight of methyl vinyl silicone rubber is 4.17g.

[0050] Example 7 The difference between this embodiment and embodiment 5 is that the weight ratio of thermoplastic polyurethane elastomer to methyl vinyl silicone rubber in this embodiment is 3:1. Specifically, the weight of thermoplastic polyurethane elastomer is 9.375g and the weight of methyl vinyl silicone rubber is 3.125g.

[0051] Examples 8-9 Based on Example 6, except for the weight ratio of graphene and dopamine hydrochloride in the transition layer, the other components and preparation methods are the same as in Example 6, and the total weight of graphene and dopamine hydrochloride in the transition layer remains unchanged.

[0052] Example 8 The difference between this embodiment and Embodiment 6 is that the weight ratio of graphene to dopamine hydrochloride in the transition layer in this embodiment is 9:1. Specifically, the weight of graphene in the transition layer is 49.5g and the weight of dopamine hydrochloride is 5.5g. Step S1 of this embodiment is as follows: 49.5g of graphene, 5.5g of dopamine hydrochloride and 500mL of Tris-HCl buffer are mixed and ultrasonically dispersed at 500W for 15min to obtain graphene dispersion B2.

[0053] Example 9 The difference between this embodiment and Embodiment 6 is that the weight ratio of graphene to dopamine hydrochloride in the transition layer in this embodiment is 8:1. Specifically, the weight of graphene in the transition layer is 48.89g and the weight of dopamine hydrochloride is 6.11g. Step S1 of this embodiment is as follows: 48.89g of graphene, 6.11g of dopamine hydrochloride and 500mL of Tris-HCl buffer are mixed and ultrasonically dispersed at 500W for 15min to obtain graphene dispersion B2.

[0054] Performance Test 2 The asymmetric thermal management composite films with thermal resistance structures prepared in Examples 4-9 were tested for thermal conductivity and thermal shock. The test methods were the same as those in Performance Test 1, and the test results are shown in Table 2 below.

[0055] Table 2 Performance of the composite membranes in Examples 2 and 4-9

[0056] As shown in Examples 2, 4-5, and Table 2, the thermal conductivity of the asymmetric thermal management composite film with a thermal resistance structure in Example 5 of this application is 0.05 W / m / K on the insulation layer side and 120 W / m / K on the heat dissipation layer side. No delamination was observed during thermal shock testing, significantly superior to Examples 2 and 4. This indicates that the combination of thermoplastic polyurethane elastomer and silicone rubber in this application can improve the stress dissipation efficiency of the transition layer while avoiding the risk of interface delamination caused by excessively high or low modulus of a single elastomer. Compared to Example 5, the pure silicone rubber in Example 4 has too low a modulus, failing to form an effective stress transfer network, resulting in stress concentration at the interface during thermal cycling that cannot be effectively dissipated. Compared with Example 5, although the simple thermoplastic polyester elastomer in Example 2 can form a continuous stress buffer network due to its excellent flexibility and good compatibility with the polyimide matrix, it lacks the low surface energy characteristics of silicone rubber, resulting in slightly poorer dispersion uniformity of graphene and hexagonal boron nitride in the transition layer, and local agglomeration of fillers limits the continuity of the thermally conductive network.

[0057] As shown in Examples 5-7 and Table 2, the thermal conductivity of the asymmetric thermal management composite film with a thermal resistance structure in Example 6 of this application is 0.02 W / m / K on the insulation layer side and 146 W / m / K on the heat dissipation layer side, which is significantly better than that in Examples 5 and 7. This indicates that the use of a specific weight ratio of thermoplastic polyurethane elastomer and silicone rubber in this application can ensure that TPU forms a continuous and tough stress buffer network in the polyimide matrix, while silicone rubber, as a secondary phase, utilizes its low surface energy characteristics to promote the uniform spreading of fillers in the transition layer. Compared with Example 6, the excessively high proportion of silicone rubber in Example 5 leads to an increased tendency for separation from the TPU phase, and there is a significant modulus change at the interface. Compared with Example 6, the excessively low proportion of silicone rubber in Example 7 weakens the filler dispersion aid effect, and the thermal conductivity of the heat dissipation layer decreases slightly.

[0058] As shown in Examples 6, 8-9, and Table 2, the thermal conductivity of the asymmetric thermal management composite film with a thermal resistance structure in Example 8 of this application is 152 W / m / K, which is significantly better than that in Examples 6 and 9. This indicates that the specific ratio of graphene and dopamine hydrochloride in the transition layer of this application can ensure that polydopamine can completely coat the graphene surface to provide sufficient polar functional group density, without hindering phonon transmission between graphene sheets due to excessive thickness. Compared with Example 8, the proportion of dopamine hydrochloride in Example 6 is too low, the polydopamine coating layer is incomplete, and the compatibility between graphene and the substrate interface is poor. Compared with Example 8, the proportion of dopamine hydrochloride in Example 9 is too high, and the thicker polydopamine layer weakens the intrinsic thermal conductivity of graphene to a certain extent.

[0059] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. An asymmetric thermal management composite membrane with a thermal resistance structure, characterized in that, The device comprises a heat insulation layer, a transition layer, and a heat dissipation layer. The heat insulation layer comprises the following raw materials in parts by weight: 10-30 parts graphene, 0.5-4.5 parts dopamine hydrochloride, 70-90 parts polyamic acid, and 5-10 parts hexagonal boron nitride. The transition layer comprises the following raw materials in parts by weight: 40-60 parts graphene, 4-6 parts dopamine hydrochloride, 40-60 parts polyamic acid, 10-20 parts hexagonal boron nitride, 10-15 parts elastomer, and 1-1.5 parts silane coupling agent. The heat dissipation layer comprises the following raw materials in parts by weight: 80-90 parts graphene, 8-9 parts dopamine hydrochloride, 10-20 parts polyamic acid, 20-30 parts hexagonal boron nitride, and 1-1.5 parts silane coupling agent.

2. The asymmetric thermal management composite membrane with a thermal resistance structure according to claim 1, characterized in that, The elastomer includes at least one of thermoplastic polyurethane elastomer and methyl vinyl silicone rubber.

3. The asymmetric thermal management composite membrane with a thermal resistance structure according to claim 2, characterized in that, The elastomer comprises thermoplastic polyurethane elastomer and methyl vinyl silicone rubber, wherein the weight ratio of the thermoplastic polyurethane elastomer to the methyl vinyl silicone rubber is (2-4):

1.

4. The asymmetric thermal management composite membrane with a thermal resistance structure according to claim 1, characterized in that, The weight ratio of graphene to dopamine hydrochloride in the transition layer is (8-10):

1.

5. The asymmetric thermal management composite membrane with a thermal resistance structure according to claim 1, characterized in that, The particle size of hexagonal boron nitride in the heat insulation layer is 1-5 μm, the particle size of hexagonal boron nitride in the transition layer is 5-10 μm, and the particle size of hexagonal boron nitride in the heat dissipation layer is 100-200 nm.

6. The asymmetric thermal management composite membrane with a thermal resistance structure according to claim 1, characterized in that, The thickness of the heat insulation layer is 250-350μm, the thickness of the transition layer is 50-100μm, and the thickness of the heat dissipation layer is 100-150μm.

7. The asymmetric thermal management composite membrane with a thermal resistance structure according to claim 1, characterized in that, The silane coupling agent in the transition layer and the heat dissipation layer is γ-aminopropyltriethoxysilane.

8. A method for preparing an asymmetric thermal management composite film with a thermal resistance structure as described in any one of claims 1-7, characterized in that, Includes the following steps: S1. Graphene, dopamine hydrochloride, and tris(hydroxymethyl)aminomethane hydrochloride buffer are mixed and stirred until homogeneous to obtain a graphene dispersion. S2. The graphene dispersion, hexagonal boron nitride, and solvent are mixed, ultrasonically dispersed, and polyamic acid is added and stirred until homogeneous to obtain slurry A. S3. The graphene dispersion, hexagonal boron nitride, and solvent are mixed, ultrasonically dispersed, a silane coupling agent is added, and the mixture is heated to reflux. Then, polyamic acid and elastomer are added and stirred until homogeneous to obtain slurry B. S4. The graphene dispersion, hexagonal boron nitride, and solvent are mixed, ultrasonically dispersed, a silane coupling agent is added, and the mixture is heated to reflux. Then, polyamic acid is added and stirred until homogeneous to obtain slurry C. S5. Slurry A is injected into a mold and frozen. Then, slurry B and slurry C are injected sequentially, freeze-dried, heated, and hot-pressed to obtain an asymmetric thermal management composite membrane with a thermal resistance structure.

9. The method for preparing an asymmetric thermal management composite film with a thermal resistance structure according to claim 8, characterized in that, The solvent is N-methylpyrrolidone.

10. The application of an asymmetric thermal management composite film with a thermal resistance structure as described in any one of claims 1-7 in heat dissipation of electronic devices.

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