Polyimide-based heat-conducting composite material based on heterogeneous interaction structure of core-shell microspheres and heat-conducting filler and preparation method of polyimide-based heat-conducting composite material

Abstract

The invention provides a polyimide-based heat-conducting composite material based on a heterogeneous interaction structure of core-shell microspheres and a heat-conducting filler and a preparation method of the polyimide-based heat-conducting composite material. The method comprises the following steps: preparing Pickering emulsion from a polymer A, an organic solvent, water, a surfactant and a heat-conducting filler A, demulsifying, filtering, washing and drying to obtain core-shell particles; the preparation method comprises the following steps: preparing a polyamic acid solution from aromatic diamine, a polar organic solvent and aromatic dianhydride, performing phase inversion, crushing, washing and drying to prepare polyamic acid salt precursor powder, and preparing a water-based polyamic acid salt solution from the polyamic acid salt precursor powder, triethylamine and water; and dispersing the core-shell particles and the heat-conducting filler B in a water-based polyamide acid salt solution, and heating and drying to obtain the heat-conducting composite material. The method is easy to operate, high-temperature melt blending treatment is not needed, the method is suitable for large-scale industrial production, and the obtained material has high heat conduction performance and mechanical performance and is expected to be widely applied to the field of heat conduction and heat dissipation.

Description

Technical Field

[0001] This invention relates to the field of polymer-based thermally conductive composite materials, and more specifically to a polymer-based thermally conductive composite material prepared based on a heterogeneous interactive structure of a core-shell structure and a thermally conductive filler. Background Technology

[0002] Entering the 21st century, the rapid development of science and technology in my country has driven the continuous innovation of electronic technology and also put forward higher requirements for the heat dissipation performance of materials.

[0003] Polymer-based thermally conductive composites are favored by industry due to their lightweight, ease of processing, corrosion resistance, and excellent thermal conductivity. Currently, the preparation of polymer-based thermally conductive materials often involves simply adding thermally conductive fillers to achieve high thermal conductivity. However, this method has poor thermal conductivity amplification efficiency, often requiring high filler content to establish thermal conduction pathways and improve the overall thermal conductivity of the material. To meet the requirements of low filler content and high thermal conductivity, the academic community has proposed a composite material with an insulating structure as a solution, which has shown some effectiveness.

[0004] Core-shell composite materials with an isolation structure refer to composites in which a coating layer is formed on the polymer surface, which can promote the formation of a continuous structure of thermally conductive filler particles on the outside of the polymer and obtain efficient thermal conduction pathways, thereby forming a continuous thermally conductive network. Studies have found that this approach can maximize the utilization of thermally conductive fillers and improve the unit volume utilization rate of thermally conductive fillers, and forming a core-shell structure is a beneficial strategy. CN 113337077A proposes a high thermal conductivity and electromagnetic shielding polyetheretherketone composite material with an isolation structure and its preparation method. Specifically, carbon nanotubes and graphene are used as synergistic fillers, and polyetheretherketone coated with polybenzoxazine is used to form composite particles. Finally, the polyetheretherketone composite material is prepared by cross-linking curing and hot-pressing. The prepared material has good thermal conductivity and electromagnetic shielding performance. CN115521635A utilizes fluoroplastic microspheres coated with carbon nanotubes and heterostructured magnetic iron compounds. After mechanically blending the composite microspheres with magnetic particles, a high shielding and high thermal conductivity composite material is prepared by hot molding. C116355366A discloses a high thermal conductivity and electrically insulating polymer composite material with an oriented, isolated dual-filler network. This method uses carbon nanotubes and boron nitride as dual fillers, and prepares the composite material with an oriented, isolated dual-network structure through processes such as melt blending, mechanical blending, annealing, and orientation. This material exhibits high thermal conductivity and electrical insulation properties with low filler content, achieving a thermal conductivity and tensile strength of 1.0 W·m⁻¹. -1 ·K -1And 37.7 MPa. Although existing technologies have made some progress, the materials still have many shortcomings. First, the mechanical properties of the prepared thermally conductive materials are poor, and the thermal conductivity is still insufficient. This is because the thermally conductive fillers coated on the polymer surface lack interaction forces during processing, making it difficult to achieve effective bonding, thus leading to poor mechanical properties of the composite material. Second, the density between the thermally conductive fillers in the formed isolation structure is low, and the existing gaps affect the density of the material's thermally conductive network, which is not conducive to improving the overall thermal conductivity of the material. Third, the prepared materials need to be hot-molded at 140-270℃, and for special engineering plastics such as polyetheretherketone, they even need to be melt-pressed at 380℃ and 30MPa. The preparation conditions are harsh, and the preparation process is difficult. Therefore, a more suitable technical solution is needed to complete the preparation of composite materials with high thermal conductivity and high mechanical properties.

[0005] Forming core-shell particles is a feasible strategy to improve thermal conductivity and reduce filler content, but core-shell particles alone cannot meet the overall requirements of the material. Therefore, it is necessary to introduce large-sized heterogeneous fillers and form a synergistic effect with the core-shell particles to complete the design of the overall internal microstructure of the composite material. Thus, how to use an economically feasible solution to simultaneously improve the thermal conductivity and mechanical properties of polymer-based composites is a problem that urgently needs to be solved. Summary of the Invention

[0006] In order to overcome the above-mentioned technical problems, the present invention provides a polymer-based thermally conductive composite material prepared based on a heterogeneous structure of core-shell structure and large-size filler, and a method for preparing the same, so as to solve the above problems.

[0007] This invention first designs a polymer with a surface-coated thermally conductive filler as a thermally conductive core-shell structure, and then distributes another component—a large-sized thermally conductive filler—within the polymer matrix. Utilizing the heterogeneous synergistic interaction between the thermally conductive core-shell structure and the thermally conductive filler, high thermal conductivity is achieved while reducing filler usage. Simultaneously, the polymer, as the resin matrix in the composite material, enhances the mechanical properties within the material. This approach is a feasible method for constructing continuous thermally conductive pathways within a polymer matrix and is suitable for developing next-generation novel thermally conductive materials.

[0008] Therefore, in a first aspect, the present invention provides a method for preparing a polyimide-based thermally conductive composite material based on a heterogeneous interactive structure of core-shell microspheres and thermally conductive fillers, the method comprising the following steps: (1) Preparation of core-shell structure with surface-coated thermally conductive filler A Water and a surfactant are added to a first solution containing polymer A and an organic solvent to prepare an emulsion. Thermally conductive filler A is added to the emulsion and stirred to form a Pickering emulsion. The Pickering emulsion is demulsified in a poor solvent to obtain a suspension. The suspension is filtered, washed, and dried to obtain core-shell particles with a polymer surface coated with thermally conductive filler. (2) Preparation of aqueous polyamic acid salt solution Aromatic dianhydride is added to a second solution containing an aromatic diamine and a polar organic solvent and stirred to obtain a polyamic acid solution. The polyamic acid solution undergoes a phase inversion process in a poor solvent, and after pulverization, washing, and drying, a polyamic acid precursor powder is obtained. An aqueous polyamic acid solution is prepared using the polyamic acid precursor powder, triethylamine, and water. (3) Preparation of polyimide-based thermally conductive composite materials The core-shell particles and thermally conductive filler B are dispersed in the aqueous polyamic acid salt solution to prepare a mixture. The mixture is then heated and dried to obtain a polyimide-based thermally conductive composite material based on the heterogeneous synergistic structure of the core-shell structure and the thermally conductive filler B.

[0009] The present invention provides, in a second aspect, a polyimide-based thermally conductive composite material prepared according to the method described in the first aspect of the present invention.

[0010] Compared with other invention patents, this invention has the following advantages: (1) In this invention, no surface chemical treatment is required for the thermally conductive filler. The core-shell filler can be prepared simply by adding chemical additives and mixing with a mixer. The process is simple and convenient. Mixing the core-shell filler as a novel thermally conductive filler with the existing one-dimensional long aspect ratio thermally conductive filler B can fully leverage their synergistic effect: thermally conductive filler B has a large aspect ratio and plays the role of establishing the main thermal conduction pathway; while the core-shell filler promotes the coating of large-sized thermally conductive filler A on the surface of the polymer, which not only acts as a "bridging" for thermal conduction in the composite material, but also increases the proportion of the polymer in the composite material, indirectly reducing the filler utilization rate. The core-shell filler and the thermally conductive filler can fully exert their synergistic interaction within the composite material, improving the thermal conductivity of the material.

[0011] (2) In this invention, the resin matrix is ​​used as the connecting structure between the thermally conductive filler B and the core-shell filler, which improves the density of the thermally conductive network and avoids the unfavorable situation of filler-filler contact that occurs in traditional isolation structures. The polymer itself has strong mechanical properties, and using the polymer as the carrier of the thermally conductive filler B can make up for the lack of mechanical properties. In addition, the polymer A inside the selected core-shell filler has a glass transition temperature of less than 250°C (e.g., the glass transition temperature of polyetherimide is below 250°C). g=217℃), during the heating and drying process, polymer A in the core-shell structure will melt or flow at high temperatures. Combined with the polyimide material, the "anchor point" structure can indirectly improve the overall mechanical properties of the composite material.

[0012] (3) Most operations of this invention are performed at room temperature, with only imidization requiring high temperature. This invention avoids the unfavorable conditions of high-temperature melt blending. The preparation method of this invention is efficient, scientific, and operable, suitable for large-scale industrial production. In summary, this invention provides a method for preparing a thermally conductive composite film using polyimide, a special engineering plastic, as the matrix. It is expected to be applied in the field of thermal conductivity and heat dissipation in future new communication technologies or advanced thermal management technologies. Detailed Implementation

[0013] To clearly and completely describe the purpose, technical solution, and advantages of this invention, the technical solution of this invention will be fully described below in conjunction with embodiments. This detailed description should not be considered a limitation of this invention, but rather an illustrative description of certain aspects, characteristics, and embodiments of this invention. The content of this invention is not limited to the following embodiments; all other embodiments obtained without creative effort are within the scope of protection of this invention.

[0014] In a first aspect, this invention provides a method for preparing a polyimide-based thermally conductive composite material based on a heterogeneous interactive structure of core-shell microspheres and thermally conductive fillers, the method comprising the following steps: (1) Preparation of core-shell structure with surface-coated thermally conductive filler A Water and a surfactant are added to a first solution containing polymer A and an organic solvent to prepare an emulsion. Thermally conductive filler A is added to the emulsion and stirred to form a Pickering emulsion. The Pickering emulsion is demulsified in a poor solvent to obtain a suspension. The suspension is filtered, washed, and dried to obtain core-shell particles with a polymer surface coated with thermally conductive filler. (2) Preparation of aqueous polyamic acid salt solution Aromatic dianhydride is added to a second solution containing an aromatic diamine and a polar organic solvent and stirred to obtain a polyamic acid solution. The polyamic acid solution undergoes a phase inversion process in a poor solvent, and after pulverization, washing, and drying, a polyamic acid precursor powder is obtained. An aqueous polyamic acid solution is prepared using the polyamic acid precursor powder, triethylamine, and water. (3) Preparation of polyimide-based thermally conductive composite materials The core-shell particles and thermally conductive filler B are dispersed in the aqueous polyamic acid salt solution to prepare a mixture. The mixture is then heated and dried to obtain a polyimide-based thermally conductive composite material based on the heterogeneous synergistic structure of the core-shell structure and the thermally conductive filler B.

[0015] The present invention will be further described step by step below.

[0016] Step (1): Preparation of the core-shell structure with surface-coated thermally conductive filler A In this step, water and a surfactant are added to a first solution containing polymer A and an organic solvent to prepare an emulsion. Thermally conductive filler A is added to the emulsion and stirred to form a Pickering emulsion. The Pickering emulsion is demulsified in a poor solvent to obtain a suspension. The suspension is filtered, washed, and dried to obtain core-shell particles with the polymer surface coated with thermally conductive filler.

[0017] Preferably, the polymer A is selected from one or more of polyetherimide, phenolphthalein-type polyetheretherketone, polyethersulfone, polylactic acid, polysulfone, and polyphenylene ether, and more preferably polyetherimide.

[0018] Preferably, the organic solvent is selected from one or a mixture of two of dichloromethane and trichloromethane.

[0019] Preferably, the surfactant is selected from one or more of polyvinyl alcohol, polyvinylpyrrolidone, polyethyleneimine, and chitosan.

[0020] Preferably, the thermally conductive filler A is composed of a two-dimensional material selected from one or more of graphite, graphene nanosheets, graphene oxide, carbon nanotubes, silicon carbide, alumina, boron nitride, MXene, and C3N4. More preferably, the particle size distribution of the two-dimensional material is 1~20 μm (e.g., 5, 10, or 15 μm), and even more preferably 1~10 μm (e.g., 4~10 μm).

[0021] Alternatively, preferably, the thermally conductive filler A is composed of a zero-dimensional material selected from one or more of aluminum nitride, alumina, thermally conductive diamond, boron nitride nanospheres, gallium indium tin alloy, tin-bismuth alloy, and graphite nanoparticles. More preferably, the particle size distribution of the zero-dimensional material is 0.1~10 μm (e.g., 0.5, 1, or 5 μm), and even more preferably 1~5 μm.

[0022] Preferably, the undesirable solvent is selected from one or more of methanol, ethanol, and isopropanol.

[0023] Preferably, the polymer A in the first solution is 1 to 20 wt% (e.g., 5, 10 or 15 wt%), more preferably 5 to 10 wt%.

[0024] Preferably, the volume ratio of the water to the first solution is 3:1 to 20:1 (e.g., 5:1, 10:1 or 15:1), more preferably 3:1 to 9:1.

[0025] Preferably, the surfactant in the emulsion is 0.01 to 5 wt% (e.g., 0.1, 0.5, 1, 2, 3 or 4 wt%), and more preferably 0.1 to 0.5 wt%.

[0026] Preferably, the stirring speed of the emulsion is 12,000 to 18,000 rpm (e.g., 14,000 or 16,000 rpm), the stirring time is 3 to 10 minutes (e.g., 5 or 8 minutes), and the stirring temperature is 0 to 5°C (e.g., 1, 2, 3 or 4°C).

[0027] Preferably, the washing is performed by washing with water three times, followed by washing with alcohol three times.

[0028] Preferably, the drying is carried out in the following manner: under a pressure of 0.5-1 MPa (e.g., 0.75 MPa) and a temperature of 40-80 °C (e.g., 50, 60 or 70 °C), the drying time is 6-12 h (e.g., 9 h).

[0029] Step (2): Preparation of aqueous polyamic acid salt solution In this step, an aromatic dianhydride is added to a second solution containing an aromatic diamine and a polar organic solvent and stirred to obtain a polyamic acid solution. The polyamic acid solution undergoes a phase inversion process in a poor solvent, and after pulverization, washing, and drying, a polyamic acid precursor powder is obtained. An aqueous polyamic acid solution is prepared using the polyamic acid precursor powder, triethylamine, and water.

[0030] Preferably, the aromatic diamine is selected from one or more of 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether and 1,3-bis(3-aminophenoxy)benzene, and is preferably 4,4'-diaminodiphenyl ether.

[0031] Preferably, the polar organic solvent is selected from one or more of N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone.

[0032] Preferably, the aromatic dianhydride is selected from one or more of pyromellitic dianhydride, 2,3,3',4'-biphenyltetracarboxylic dianhydride, 3,3,4',4'-biphenyltetracarboxylic dianhydride, 2,3,3',4'-oxobis(o-tetracarboxylic dianhydride), 3,3,4',4'-oxobis(o-tetracarboxylic dianhydride), 4,4'-hexafluoroisopropylphthalic anhydride, and bisphenol A type diether dianhydride.

[0033] Preferably, the undesirable solvent is selected from one or more of water, methanol, ethanol, isopropanol, and acetone.

[0034] Preferably, the mass ratio of the aromatic diamine to the aromatic dianhydride is (0.97~1.03):1 (for example, 1:1), and more preferably (0.98~1.01):1.

[0035] Preferably, the total mass percentage of the aromatic diamine and the aromatic dianhydride in the polyamic acid solution is 5-30% (e.g., 10, 15, 20 or 25%).

[0036] Preferably, the volume ratio of the polyamic acid solution to the undesirable solvent is 1:5 to 10 (e.g., 1:6, 1:7, 1:8 or 1:9).

[0037] Preferably, based on the total amount of the aqueous polyamic acid salt solution, the mass percentage of the polyamic acid salt precursor powder is 5-25% (e.g., 10, 15, or 20%), the mass percentage of the triethylamine is 3-12% (e.g., 6 or 9%), and the mass percentage of the water is 63-92% (e.g., 65, 70, 75, 80, or 85%).

[0038] Preferably, the stirring speed is 250 rpm to 1500 rpm, the stirring temperature is 0 to 10°C (e.g., 2, 4, 6 or 8°C), and the stirring time is 6 to 48 hours (e.g., 12, 18, 24, 30, 36 or 42 hours), preferably 6 to 12 hours.

[0039] Preferably, after the pulverization, the particle size of the particles in the polyamic acid solution is 50-300 mesh (e.g., 100-200 mesh).

[0040] Preferably, the washing solution is a mixture of water and ethanol, and preferably, the volume ratio of water to ethanol in the mixture is 5:1 to 1:5 (e.g., 4:1, 2:1 or 1:3).

[0041] Preferably, the drying is carried out by drying at a temperature of 45~55°C (e.g., 50°C) and under vacuum for 12~48 hours (e.g., 24 or 36 hours).

[0042] Step (3): Preparation of polyimide-based thermally conductive composite material The core-shell particles and thermally conductive filler B are dispersed in the aqueous polyamic acid salt solution to prepare a mixture. The mixture is then heated and dried to obtain a polyimide-based thermally conductive composite material based on the heterogeneous synergistic structure of the core-shell structure and the thermally conductive filler B.

[0043] Preferably, step (3) is carried out in the following manner: the core-shell particles and the thermally conductive filler B are dispersed in the aqueous polyamic acid salt solution by solution mixing, and after ultrasonic treatment and stirring, a mixture is obtained. Then, the mixture is poured onto a glass plate, coated with a film scraper, and after film laying and heating drying, a polymer-based thermally conductive composite film is obtained as the polyimide-based thermally conductive composite material. Preferably, the thermally conductive filler B is composed of a one-dimensional material, which is selected from one or more of multi-walled carbon nanotubes, single-walled carbon nanotubes, double-walled carbon nanotubes, silicon carbide, silver nanowires, copper nanowires, and chopped carbon fibers. More preferably, the particle size distribution of the one-dimensional material is 20-50 μm, preferably 20-30 μm. Preferably, the polymer B in the mixture is 1 to 20 wt% (e.g., 5, 10 or 15 wt%), and more preferably 5 to 10 wt%.

[0044] Preferably, the core-shell particles account for 1 to 30 wt% of the total mass of all added solid particles (e.g., 5, 10, 15, 20 or 25 wt%).

[0045] Preferably, the thermally conductive filler B accounts for 1 to 30 wt% of the total mass of all added solid particles (e.g., 5, 10, 15, 20 or 25 wt%).

[0046] Preferably, the ultrasonic treatment is performed at 1000W for 3 to 20 minutes (e.g., 5 or 8 minutes).

[0047] Preferably, the stirring speed is 500~2500 rpm (1000, 1500 or 200 rpm), and the stirring time is 1~6h (e.g. 2, 3, 4 or 5 min).

[0048] Preferably, the thickness of the film scraped by the doctor blade is 100~500 μm.

[0049] Preferably, the heating and drying is carried out in the following manner: sequentially maintaining a temperature of 60–70°C for 2–4 hours, 80–90°C for 2–4 hours, 120–130°C for 2–4 hours, 150–180°C for 2–4 hours, and 200–300°C for 2–12 hours. For example, it can be sequentially maintaining a temperature of 60°C for 2 hours, 80°C for 2 hours, 120°C for 2 hours, 150°C for 2 hours, 200°C for 2 hours, 250°C for 2 hours, and 300°C for 2 hours.

[0050] The preferred technical means provided in the above steps can be combined in various ways to form various technical solutions, unless otherwise stated. All of these technical solutions fall within the protection scope of this invention.

[0051] For example, the preparation method provided in the first aspect of the present invention may include a combination of certain preferred technical means described above, including the following steps: (1) Preparation of core-shell structure with surface-coated thermally conductive filler A In this step, a core-shell structure with thermally conductive filler A coated on the surface of polymer A can be prepared using an emulsion method. First, polymer A is dissolved in an organic solvent. The resulting solution is then mixed with water (such as deionized water) and a surfactant to prepare an emulsion. Thermally conductive filler A is added to this emulsion and stirred to obtain a Pickering emulsion. Subsequently, the Pickering emulsion is demulsified in a poor solvent to obtain a suspension. After filtration, washing, and drying, core-shell particles with thermally conductive filler coated on the polymer surface are obtained.

[0052] (2) Preparation of aqueous polyamic acid salt solution This step involves preparing an aqueous polyamic acid salt solution. An aromatic diamine is added to a polar organic solvent, and after dissolution, an aromatic dianhydride is added and stirred to obtain a polyamic acid solution. The resulting polyamic acid solution is poured into a poor solvent to complete the phase inversion process, and after pulverization, washing, and drying, a polyamic acid salt precursor powder is obtained. The polyamic acid salt precursor powder is then mixed with triethylamine and water to prepare an aqueous polyamic acid salt solution.

[0053] (3) Preparation of polyimide-based thermally conductive composite materials This step prepares a polymer-based thermally conductive composite material based on a heterogeneous synergistic structure of a core-shell structure and thermally conductive filler B. The core-shell particles obtained in step (1) and the thermally conductive filler B are dispersed in the aqueous polyamic acid salt solution obtained in step (2) by solution blending. After ultrasonic treatment and stirring, a uniformly dispersed mixture of thermally conductive filler is obtained. Subsequently, the mixture is poured onto a glass plate, treated with a film scraper, and then laid, heated, and dried to obtain a polymer-based thermally conductive composite film.

[0054] The present invention provides, in a second aspect, a polyimide-based thermally conductive composite material prepared according to the method described in the first aspect of the present invention. Example

[0055] The present invention will be further described below by way of examples, but the scope of protection of the present invention is not limited to these embodiments.

[0056] Example 1 First, 5 g of polyetherimide (PEI) was dissolved in 20 mL of dichloromethane. 80 mL of deionized water and 0.5 g of polyvinylpyrrolidone were added to form a mixture, followed by 1.25 g of graphite nanosheets (GNP, average size 5 μm). The mixture was stirred at 0 °C and 14000 rpm for 5 min to form an O / W emulsion (oil-in-water emulsion). The emulsion was then demulsified in 500 mL of methanol, and the core-shell particle powder in the suspension was collected. The powder was then filtered. After drying at 0.5 MPa and 60 °C for 12 h, graphite nanosheet-coated polyetherimide (PEI@GNP) core-shell particles were obtained.

[0057] 10.01 g (5 mmol) of 4,4'-diaminodiphenyl ether and 500 ml of N,N-dimethylacetamide were dissolved in a container, followed by the addition of 15.51 g (5 mmol) of 3,3,4',4'-oxobis(o-tetracarboxylic acid) dianhydride. The mixture was stirred at 500 rpm for 9 hours at 0°C to obtain a polyamic acid solution. The polyamic acid solution was poured into 3 L of ethanol to precipitate filamentous solids. These solids were then pulverized to 300 mesh, washed with 3 L of deionized water and ethanol (1:1 volume ratio), and vacuum dried at 50°C for 12 hours to obtain a polyamic acid precursor powder. An aqueous solution of polyamic acid was prepared by dissolving 10 g of the precursor powder, 4.8 g of triethylamine, and 90 ml of deionized water.

[0058] 2.5 g of PEI@GNP core-shell particles and 2.5 g of multi-walled carbon nanotubes (average particle size distribution 20 μm) were dispersed in 100 ml of the above-mentioned aqueous polyamic acid salt solution. The mixture was ultrasonically treated at 1000 W and 50 Hz for 20 min, followed by continuous stirring at 1500 rpm for 30 min to obtain a uniformly dispersed mixture. The mixture was poured onto a glass plate, treated with a 200 μm doctor blade, and then placed in an oven. The film was then heated to 60℃, 80℃, 120℃, 150℃, 200℃, 250℃, and 300℃ for 2 h each to obtain a polyimide-based thermally conductive composite film. The thermally conductive filler A in the composite material was graphite nanosheets, and the thermally conductive filler B was multi-walled carbon nanotubes. The total content of all thermally conductive fillers was 20 wt%, and the vertical thermal conductivity of the composite material was 1.63 W·m. -1 ·K -1 The horizontal thermal conductivity is 3.18 W·m. -1 ·K -1 .

[0059] Example 2 5 g of phenolphthalein-type polyaryletherketone (PEK-C) was dissolved in 20 mL of dichloromethane. 80 mL of deionized water and 0.5 g of polyethyleneimine were added to form a mixture, followed by 1.25 g of boron nitride (BN, average size 10 μm). The mixture was stirred continuously at 15000 rpm for 5 min at 2 °C to form an O / W emulsion (oil-in-water emulsion). The emulsion was then demulsified in 500 mL of ethanol, and the core-shell particle powder in the suspension was collected. The powder was then filtered. After drying at 0.5 MPa and 60 °C for 12 h, boron nitride-coated phenolphthalein-type polyaryletherketone (PEK-C@BN) core-shell particles were obtained.

[0060] 10.01 g (5 mmol) of 3,4'-diaminodiphenyl ether and 500 ml of N,N-dimethylacetamide were dissolved in a container, followed by the addition of 15.51 g (5 mmol) of 3,3,4',4'-oxobis(o-tetracarboxylic acid) dianhydride. The mixture was stirred at 500 rpm for 9 hours at 0°C to obtain a polyamic acid solution. The solution was poured into 3 L of methanol to precipitate filamentous solids, which were then pulverized to 300 mesh. After washing with 4 L of deionized water and ethanol (volume ratio 1:2), the mixture was vacuum dried at 50°C for 12 hours to obtain a polyamic acid precursor powder. 10 g of the precursor powder, 4.8 g of triethylamine, and 90 ml of deionized water were used to prepare an aqueous polyamic acid solution.

[0061] 2.5 g of PEK-C@BN core-shell particles and 2.5 g of single-walled carbon nanotubes (average particle size distribution 10 μm) were dispersed in 100 ml of the above-mentioned aqueous polyamic acid salt solution. The mixture was ultrasonically treated at 1000 W and 50 Hz for 20 min, followed by continuous stirring at 1500 rpm for 30 min to obtain a uniformly dispersed mixture. The mixture was poured onto a glass plate, treated with a 200 μm doctor blade, and then placed in an oven. The film was then heated to 60℃, 80℃, 120℃, 150℃, 200℃, 250℃, and 300℃ for 2 h each time to obtain a polyimide-based thermally conductive composite film. The thermally conductive filler A in the composite material was boron nitride, and the thermally conductive filler B was single-walled carbon nanotubes. The total content of all thermally conductive fillers was 20 wt%, and the vertical thermal conductivity of the composite material was 0.67 W·m. -1 ·K -1 The horizontal thermal conductivity is 1.53 W·m. -1 ·K -1 .

[0062] Example 3 5 g of polyethersulfone (PES) was dissolved in 20 mL of dichloromethane. 80 mL of deionized water and 0.5 g of polyethyleneimine were added to form a mixture, followed by 1.25 g of graphene (GP, average size 7 μm). The mixture was stirred continuously at 14000 rpm for 10 min at 0 °C to form an O / W emulsion. The emulsion was then demulsified in 500 mL of ethanol, and the core-shell particle powder was collected from the suspension. The powder was then filtered. After drying at 0.5 MPa and 60 °C for 12 h, graphene-coated polyethersulfone (PES@GP) core-shell particles were obtained.

[0063] 10.01 g (5 mmol) of 4,4'-diaminodiphenyl ether and 500 ml of N,N-dimethylacetamide were dissolved in a container, followed by the addition of 15.51 g (5 mmol) of 2,3,3',4'-oxobis(o-tetracarboxylic acid) dianhydride. The mixture was stirred at 750 rpm for 9 hours at 0°C to obtain a polyamic acid solution. The solution was poured into 3 L of deionized water to precipitate filamentous solids, which were then pulverized to 300 mesh. After washing with 3 L of deionized water and ethanol (volume ratio 3:1), the mixture was vacuum dried at 50°C for 12 hours to obtain a polyamic acid precursor powder. 10 g of the precursor powder, 4.8 g of triethylamine, and 90 ml of deionized water were used to prepare an aqueous polyamic acid solution.

[0064] 2.5 g of PES@GP core-shell particles and 2.5 g of double-walled carbon nanotubes (average particle size distribution 18 μm) were dispersed in 100 ml of the above-mentioned aqueous polyamic acid salt solution. The mixture was ultrasonically treated at 1000 W and 50 Hz for 20 min at 1500 rpm to obtain a uniformly dispersed mixture. The mixture was poured onto a glass plate, treated with a 200 μm doctor blade, and then placed in an oven. The film was then heated to 60℃, 80℃, 120℃, 150℃, 200℃, 250℃, and 300℃ for 2 h each to obtain a polyimide-based thermally conductive composite film. The thermally conductive filler A in the composite material is graphene, and the thermally conductive filler B is double-walled carbon nanotubes. The total content of all thermally conductive fillers is 20 wt%, and the vertical thermal conductivity of the composite material is 1.66 W·m. -1 ·K -1 The horizontal thermal conductivity is 3.32 W·m. -1 ·K -1 .

[0065] Example 4 5 g of polylactic acid (PLA) was dissolved in 20 mL of chloroform. 80 mL of deionized water and 0.5 g of polyethyleneimine were added to form a mixture, followed by 1.25 g of graphene oxide (GO, average size 10 μm). The mixture was stirred continuously at 14000 rpm for 5 min at 0 °C to form an O / W emulsion. The emulsion was then demulsified in 500 mL of ethanol, and the core-shell particles in the suspension were collected. The powder was then filtered. The resulting graphene-coated polyethersulfone (PLA@GO) core-shell particles were obtained by drying at 0.5 MPa and 60 °C for 12 h.

[0066] 14.62 g (5 mmol) of 1,3-bis(3-aminophenoxy)benzene and 500 ml of N,N-dimethylformamide were weighed and dissolved in a container. Then, 22.21 g (5 mmol) of 4,4'-hexafluoroisopropylphthalic anhydride was added. The mixture was stirred at 500 rpm for 9 hours at 0°C to obtain a polyamic acid solution. The solution was poured into 3 L of deionized water to precipitate filamentous solids, which were then pulverized to 300 mesh. After washing with 4 L of deionized water and ethanol (volume ratio of 1:3), the mixture was vacuum dried at 50°C for 12 hours to obtain polyamic acid precursor powder. 10 g of the precursor powder, 4.8 g of triethylamine, and 90 ml of deionized water were used to prepare an aqueous polyamic acid solution.

[0067] 2.5 g of PLA@GO core-shell particles and 2.5 g of silicon carbide (average particle size distribution 30 μm) were dispersed in 100 ml of the above-mentioned aqueous polyamic acid salt solution. The mixture was ultrasonically treated at 1000 W and 50 Hz for 20 min, followed by ultrasonic treatment at 1500 rpm for 30 min to obtain a uniformly dispersed mixture. The mixture was poured onto a glass plate, treated with a 200 μm doctor blade, and then placed in an oven. The film was then heated to 60℃, 80℃, 120℃, 150℃, 200℃, 250℃, and 300℃ for 2 h each time to obtain a polyimide-based thermally conductive composite film. The thermally conductive filler A in the composite material is graphene oxide, and the thermally conductive filler B is silicon carbide. The total content of all thermally conductive fillers is 20 wt%, and the vertical thermal conductivity of the composite material is 1.01 W·m. -1 ·K -1 The horizontal thermal conductivity is 2.21 W·m. -1 ·K -1 .

[0068] Example 5 5 g of polysulfone (PSF) was dissolved in 20 mL of chloroform. 80 mL of deionized water and 0.5 g of polyethyleneimine were added to form a mixture, followed by 1.25 g of alumina (Al₂O₃, average size 1 μm). The mixture was stirred continuously at 14000 rpm for 5 min at 0 °C to form an O / W emulsion. The emulsion was then demulsified in 500 mL of ethanol, and the core-shell particle powder in the suspension was collected. The powder was then filtered. After drying at 0.5 MPa and 60 °C for 12 h, alumina-coated polysulfone (PSF@Al₂O₃) core-shell particles were obtained.

[0069] 14.62 g (5 mmol) of 1,3-bis(3-aminophenoxy)benzene and 500 ml of N,N-dimethylformamide were weighed and dissolved in a container. Then, 22.21 g (5 mmol) of 4,4'-hexafluoroisopropylphthalic anhydride was added. The mixture was stirred at 500 rpm for 9 hours at 0°C to obtain a polyamic acid solution. The solution was poured into 3 L of deionized water to precipitate filamentous solids, which were then pulverized to 300 mesh. After washing with 4 L of deionized water and ethanol (volume ratio of 1:3), the mixture was vacuum dried at 50°C for 12 hours to obtain polyamic acid precursor powder. 10 g of the precursor powder, 4.8 g of triethylamine, and 90 ml of deionized water were used to prepare an aqueous polyamic acid solution.

[0070] 2.5 g of PSF@Al2O3 core-shell particles and 2.5 g of silver nanowires (average size 40 μm) were dispersed in 100 ml of the above-mentioned aqueous polyamic acid salt solution. The mixture was ultrasonically treated at 1000 W and 50 Hz for 20 min, followed by continuous stirring at 1500 rpm for 30 min to obtain a uniformly dispersed mixture. The mixture was poured onto a glass plate, treated with a 200 μm doctor blade, and then placed in an oven. The film was then heated to 60℃, 80℃, 120℃, 150℃, 200℃, 250℃, and 300℃ for 2 h each to obtain a polyimide-based thermally conductive composite film. The thermally conductive filler A in the composite material was alumina, and the thermally conductive filler B was silver nanowires. The total content of all thermally conductive fillers was 20 wt%, and the vertical thermal conductivity of the composite material was 1.07 W·m. -1 ·K -1 The horizontal thermal conductivity is 2.12 W·m. -1 ·K -1 .

[0071] Example 6 5 g of polyphenylene oxide (PPE) was dissolved in 20 mL of chloroform. 80 mL of deionized water and 0.5 g of polyethyleneimine were added to form a mixture, followed by 1.25 g of aluminum nitride (AlN, average size 2 μm). The mixture was stirred at 0 °C and 14000 rpm for 5 min to form an O / W emulsion. The emulsion was then demulsified in 500 mL of ethanol, and the core-shell particle powder in the suspension was collected. The powder was filtered and dried at 0.5 MPa and 60 °C for 12 h to obtain alumina-coated polysulfone (PPE@AlN) core-shell particles.

[0072] 14.62 g (5 mmol) of 1,3-bis(3-aminophenoxy)benzene and 500 ml of N,N-dimethylformamide were weighed and dissolved in a container. Then, 22.21 g (5 mmol) of 4,4'-hexafluoroisopropylphthalic anhydride was added. The mixture was stirred at 500 rpm for 9 hours at 0°C to obtain a polyamic acid solution. The solution was poured into 3 L of deionized water to precipitate filamentous solids, which were then pulverized to 300 mesh. After washing with 3 L of deionized water and ethanol (1:1 volume ratio), the mixture was vacuum dried at 50°C for 12 hours to obtain polyamic acid precursor powder. 10 g of the precursor powder, 4.8 g of triethylamine, and 90 ml of deionized water were used to prepare an aqueous polyamic acid solution.

[0073] 2.5 g of PPE@AlN core-shell particles and 2.5 g of copper nanowires (average size 25 μm) were dispersed in 100 ml of the above-mentioned aqueous polyamic acid salt solution. The mixture was ultrasonically treated at 1000 W and 50 Hz for 20 min, followed by continuous stirring at 1500 rpm for 30 min to obtain a uniformly dispersed mixture. The mixture was poured onto a glass plate, treated with a 200 μm doctor blade, and then placed in an oven. The film was then heated to 60℃, 80℃, 120℃, 150℃, 200℃, 250℃, and 300℃ for 2 h each time to obtain a polyimide-based thermally conductive composite film. The thermally conductive filler A in the composite material was aluminum nitride, and the thermally conductive filler B was copper nanowires. The total content of all thermally conductive fillers was 20 wt%, and the vertical thermal conductivity of the composite material was 1.11 W·m. -1 ·K -1 The horizontal thermal conductivity is 2.46 W·m. -1 ·K -1 .

[0074] Example 7 5 g of polyetherimide (PEI) was dissolved in 20 mL of dichloromethane. 80 mL of deionized water and 0.5 g of polyethyleneimine were added to form a mixture, followed by 1.25 g of carbon nitride (C3N4, average size 5 μm). The mixture was stirred at 0 °C and 14000 rpm for 3 minutes to form an O / W emulsion. The emulsion was then demulsified in 500 mL of ethanol, and the core-shell particle powder in the suspension was collected. The powder was then filtered. After drying at 0.5 MPa and 60 °C for 12 hours, carbon nitride-coated polyetherimide (PEI@C3N4) core-shell particles were obtained.

[0075] 14.62 g (5 mmol) of 1,3-bis(3-aminophenoxy)benzene and 500 ml of N,N-dimethylformamide were weighed and dissolved in a container. Then, 22.21 g (5 mmol) of 4,4'-hexafluoroisopropylphthalic anhydride was added. The mixture was stirred at 500 rpm for 9 hours at 0°C to obtain a polyamic acid solution. The solution was poured into 3 L of deionized water to precipitate filamentous solids, which were then pulverized to 300 mesh. After washing with 4 L of deionized water and ethanol (volume ratio of 1:5), the mixture was vacuum dried at 50°C for 12 hours to obtain polyamic acid precursor powder. 10 g of the precursor powder, 4.8 g of triethylamine, and 90 ml of deionized water were used to prepare an aqueous polyamic acid solution.

[0076] 2.5 g of PEI@C3N4 core-shell particles and 2.5 g of chopped carbon fibers (average particle size distribution 50 μm) were dispersed in 100 ml of the above-mentioned aqueous polyamic acid salt solution. The mixture was ultrasonically treated at 1000 W and 50 Hz for 20 min, followed by continuous stirring at 1500 rpm for 30 min to obtain a uniformly dispersed mixture. The mixture was poured onto a glass plate, treated with a 200 μm doctor blade, and then placed in an oven. The film was then heated to 60℃, 80℃, 120℃, 150℃, 200℃, 250℃, and 300℃ for 2 h each time to obtain a polyimide-based thermally conductive composite film. The thermally conductive filler A in the composite material is carbon nitride, and the thermally conductive filler B is chopped carbon fibers. The total content of all thermally conductive fillers is 20 wt%, and the vertical thermal conductivity of the composite material is 0.96 W·m. -1 ·K -1 The horizontal thermal conductivity is 1.93 W·m. -1 ·K -1 .

[0077] Example 8 5 g of polyetherimide (PEI) was dissolved in 20 mL of dichloromethane. 80 mL of deionized water and 0.5 g of polyethyleneimine were added to form a mixture, followed by 1.25 g of boron nitride nanospheres (average size 5 μm). The mixture was stirred continuously at 14000 rpm for 5 min at 0 °C to form an O / W emulsion. The emulsion was then demulsified in 500 mL of ethanol, and the core-shell particle powder in the suspension was collected. The powder was then filtered. After drying at 0.5 MPa and 60 °C for 12 h, boron nitride nanospheres coated with polyetherimide core-shell particles were obtained.

[0078] 14.62 g (5 mmol) of 1,3-bis(3-aminophenoxy)benzene and 500 ml of N,N-dimethylformamide were weighed and dissolved in a container. Then, 22.21 g (5 mmol) of 4,4'-hexafluoroisopropylphthalic anhydride was added. The mixture was stirred at 500 rpm for 9 hours at 0°C to obtain a polyamic acid solution. The solution was poured into 3 L of deionized water to precipitate filamentous solids, which were then pulverized to 300 mesh. After washing with 3 L of deionized water and ethanol (volume ratio of 1:3), the mixture was vacuum dried at 50°C for 12 hours to obtain polyamic acid precursor powder. 10 g of the precursor powder, 4.8 g of triethylamine, and 90 ml of deionized water were used to prepare an aqueous polyamic acid solution.

[0079] 2.5 g of core-shell particles and 2.5 g of short-cut carbon fibers (average particle size distribution 50 μm) were dispersed in 100 ml of the above-mentioned aqueous polyamic acid salt solution. The mixture was ultrasonically treated at 1000 W and 50 Hz for 20 min, followed by continuous stirring at 1500 rpm for 30 min to obtain a uniformly dispersed mixture. The mixture was poured onto a glass plate, treated with a 200 μm doctor blade, and then placed in an oven. After being heated to 60℃, 80℃, 120℃, 150℃, 200℃, 250℃, and 300℃ for 2 h each, a polyimide-based thermally conductive composite film was obtained. The thermally conductive filler A in the composite material was boron nitride nanospheres, and the thermally conductive filler B was short-cut carbon fibers. The total content of all thermally conductive fillers was 20 wt%, and the vertical thermal conductivity of the composite material was 1.25 W·m. -1 ·K -1 The horizontal thermal conductivity is 2.14 W·m. -1 ·K -1 .

[0080] Example 9 5 g of polyetherimide (PEI) was dissolved in 20 mL of dichloromethane. 80 mL of deionized water and 0.5 g of polyethyleneimine were added to form a mixture, followed by 1.25 g of MXene (average size 15 μm). The mixture was stirred continuously at 14000 rpm for 5 min at 0 °C to form an O / W emulsion. The emulsion was then demulsified in 500 mL of ethanol, and the core-shell particle powder in the suspension was collected. The powder was then filtered. After drying at 0.5 MPa and 60 °C for 12 h, MXene-coated polyetherimide (PEI@MXene) core-shell particles were obtained.

[0081] 14.62 g (5 mmol) of 1,3-bis(3-aminophenoxy)benzene and 500 ml of N,N-dimethylformamide were weighed and dissolved in a container. Then, 22.21 g (5 mmol) of 4,4'-hexafluoroisopropylphthalic anhydride was added, and the mixture was stirred at 0 °C for 9 h to obtain a polyamic acid solution. The solution was poured into 3 L of deionized water to precipitate filamentous solids, which were then pulverized to 300 mesh. After washing with 3.5 L of deionized water and ethanol (volume ratio of 3:1), the mixture was vacuum dried at 50 °C for 12 h to obtain a polyamic acid precursor powder. 10 g of the precursor powder, 4.8 g of triethylamine, and 90 ml of deionized water were used to prepare an aqueous polyamic acid solution.

[0082] 2.5 g of PEI@MXene core-shell particles and 2.5 g of multi-walled carbon nanotubes (average particle size distribution 12 μm) were dispersed in 100 ml of the above-mentioned aqueous polyamic acid salt solution. The mixture was ultrasonically treated for 20 min at 1000 W and 50 Hz, and then stirred at 1500 rpm for 20 min to obtain a uniformly dispersed mixture. The mixture was poured onto a glass plate, treated with a 200 μm doctor blade, and then placed in an oven. After being heated to 60℃, 80℃, 120℃, 150℃, 200℃, 250℃, and 300℃ for 2 h each, a polyimide-based thermally conductive composite film was obtained. In the composite material, thermally conductive filler A was PEI@MXene, and thermally conductive filler B was multi-walled carbon nanotubes. The total content of all thermally conductive fillers was 20 wt%, and the vertical thermal conductivity of the composite material was 0.97 W·m. -1 ·K -1 The horizontal thermal conductivity is 1.94 W·m. -1 ·K -1 .

[0083] Example 10 5 g of polyetherimide (PEI) was dissolved in 20 mL of dichloromethane. 80 mL of deionized water and 0.5 g of polyethyleneimine were added to form a mixture, followed by 1.25 g of boron nitride (average size 8 μm). The mixture was stirred continuously at 14000 rpm for 5 min at 0 °C to form an O / W emulsion. This emulsion was then demulsified in 500 mL of ethanol, and the core-shell particle powder in the suspension was collected. The powder was then filtered. After drying at 0.5 MPa and 60 °C for 12 h, boron nitride-coated polyetherimide core-shell particles were obtained.

[0084] 14.62 g (5 mmol) of 1,3-bis(3-aminophenoxy)benzene and 500 ml of N,N-dimethylformamide were weighed and dissolved in a container. Then, 22.21 g (5 mmol) of 4,4'-hexafluoroisopropylphthalic anhydride was added. The mixture was stirred at 500 rpm for 9 hours at 0°C to obtain a polyamic acid solution. The solution was poured into 3 L of deionized water to precipitate filamentous solids, which were then pulverized to 300 mesh. After washing with 5 L of deionized water and ethanol (volume ratio of 2:1), the mixture was vacuum dried at 50°C for 12 hours to obtain polyamic acid precursor powder. 10 g of the precursor powder, 4.8 g of triethylamine, and 90 ml of deionized water were used to prepare an aqueous polyamic acid solution.

[0085] 2.5 g of core-shell particles and 2.5 g of multi-walled carbon nanotubes (average particle size distribution 15 μm) were dispersed in 100 ml of the above-mentioned aqueous polyamic acid salt solution. The mixture was ultrasonically treated at 1000 W and 50 Hz for 20 min, followed by continuous stirring at 1500 rpm for 30 min to obtain a uniformly dispersed mixture. The mixture was poured onto a glass plate, treated with a 200 μm doctor blade, and then placed in an oven. After being heated to 60℃, 80℃, 120℃, 150℃, 200℃, 250℃, and 300℃ for 2 h each, a polyimide-based thermally conductive composite film was obtained. The thermally conductive filler A in the composite material was boron nitride, and the thermally conductive filler B was multi-walled carbon nanotubes. The total content of all thermally conductive fillers was 20 wt%, and the vertical thermal conductivity of the composite material was 1.29 W·m. -1 ·K -1 The horizontal thermal conductivity is 2.41 W·m. -1 ·K -1 .

[0086] Comparative Example 1 The procedure was basically the same as in Example 1, except that the preparation and introduction of core-shell particles were omitted. The specific operation process is as follows: 40.04 g (20 mmol) of 4,4'-diaminodiphenyl ether and 900 ml of N,N-dimethylacetamide (DMAc) were added to a flask and stirred continuously for 30 min in an ice-water bath. Then, 43.64 g (20 mmol) of pyromellitic anhydride was added all at once, and the mixture was stirred at 500 rpm for 5 h to obtain a polyamic acid solution with a solid content of 10 wt%. The prepared solution was poured into ethanol to complete the phase inversion and obtain a solid. The solid was pulverized to 300 mesh and washed three times each with a mixture of 1 L deionized water and 1 L ethanol. After vacuum drying at 50 °C for 12 h, a polyamic acid precursor powder was obtained. 8 g of the polyamic acid precursor powder, 2 g of polyetherimide, 2 g of graphene powder, and 0.5 g of multi-walled carbon nanotubes were dispersed in 500 ml of ethanol and magnetically stirred for 30 min. After filtration, washing, and drying, a composite powder was obtained. The composite powder is placed in a hot molding press and hot-molded at 300℃ and 5MPa for 30 minutes to obtain a thermally conductive composite material. The thermally conductive filler A in the composite material is graphene, and the thermally conductive filler B is multi-walled carbon nanotubes, with a filler content of 20 wt%. The vertical thermal conductivity of the composite material is 0.59 W·m. -1 ·K -1 The horizontal thermal conductivity is 1.07 W·m. -1 ·K -1 .

[0087] The electromagnetic shielding test was conducted using an R&S ZNB8 vector network analyzer (Germany). The results are shown in Table 1.

[0088] Table 1. Thermal conductivity test results of the composite materials prepared in Examples 1-10 and Comparative Example 1 As can be seen from the data of Examples 1 to 10 and Comparative Example 1 in Table 1, the composite material prepared by the present invention has excellent thermal conductivity.

[0089] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made to the present invention without departing from the scope of the present invention patent should also be considered as protection of the present invention.

Claims

1. A method for preparing a polyimide-based thermally conductive composite material based on a heterogeneous interaction structure of core-shell microspheres and thermally conductive fillers, characterized in that, The method comprises the following steps: (1) Preparation of core-shell structure of surface-coated thermal conductive filler A An emulsion is prepared by adding water and a surfactant to a first solution comprising polymer A and an organic solvent, and a Pickering emulsion is formed by adding thermal conductive filler A to the emulsion and stirring. The Pickering emulsion is broken in a poor solvent to obtain a suspension, and the suspension is filtered, washed, and dried to obtain core-shell particles of polymer surface-coated thermal conductive filler; (2) Preparation of aqueous polyamic acid salt solution An aromatic dianhydride is added to a second solution comprising an aromatic diamine and a polar organic solvent, and the solution is stirred to obtain a polyamic acid solution. The polyamic acid solution is subjected to a phase inversion process in a poor solvent, and is then crushed, washed, and dried to obtain polyamic acid salt precursor powder. The aqueous polyamic acid salt solution is prepared by using the polyamic acid salt precursor powder, triethylamine, and water. (3) Preparation of polyimide-based thermal conductive composite material The core-shell particles and thermal conductive filler B are dispersed in the aqueous polyamic acid salt solution to obtain a mixture, and the mixture is heated and dried to obtain a polyimide-based thermal conductive composite material based on a core-shell structure and a heterogeneous synergistic structure of thermal conductive filler B.

2. The method of claim 1, wherein, In step (1): The polymer A is selected from one or more of polyetherimide, phenolphthalein polyether ether ketone, polyether sulfone, polylactic acid, polysulfone, and polyphenylene ether, and is more preferably polyetherimide; The organic solvent is selected from one or both of dichloromethane and trichloromethane; The surfactant is selected from one or more of polyvinyl alcohol, polyvinylpyrrolidone, polyethyleneimine, and chitosan; The thermal conductive filler A is composed of a two-dimensional material selected from one or more of graphite, graphene graphite nanoplatelets, graphene oxide, carbon nanotubes, silicon carbide, aluminum oxide, boron nitride, MXene, and C3N4. Preferably, the average particle size distribution of the two-dimensional material is 4-20 μm, and more preferably 1-10 μm. Alternatively, the thermal conductive filler A is composed of a zero-dimensional material selected from one or more of aluminum oxide, aluminum nitride, thermal conductive diamond, boron nitride nanospheres, gallium-indium-tin alloy, tin-bismuth alloy, and graphite nanoparticles. Preferably, the particle size distribution of the zero-dimensional material is 0.1-10 μm, and more preferably 1-5 μm; and / or The poor solvent is selected from one or more of methanol, ethanol, and isopropanol.

3. The method of claim 1, wherein, In step (1): The mass percentage of the polymer A in the first solution is 1-20 wt%, and more preferably 5-10 wt%; The volume ratio of water to the first solution is 3:1-20:1, and more preferably 3:1-9:1; and / or The mass percentage of the surfactant in the emulsion is 0.01-5 wt%, and preferably 0.1-0.5 wt%.

4. The method of claim 1, wherein, In step (1): The stirring speed is 12,000-18,000 rpm, the stirring time is 3-10 min, and the stirring temperature is 0-5℃; The washing is performed by water washing 3 times and then alcohol washing 3 times; and / or The drying is performed by drying for 6-12 h at a pressure of 0.5-1 MPa and a temperature of 40-80 ℃.

5. The method of claim 1, wherein, In step (2): The aromatic diamine is selected from one or more of 3,4´-diaminodiphenyl ether, 4,4´-diaminodiphenyl ether, and 1,3-bis(3-aminophenoxy)benzene, preferably 4,4´-diaminodiphenyl ether; The polar organic solvent is selected from one or more of N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone; The aromatic dianhydride is selected from one or more of pyromellitic dianhydride, 2,3,3´,4´-biphenyltetracarboxylic dianhydride, 3,3,4´,4´-biphenyltetracarboxylic dianhydride, 2,3,3´,4´-oxydiphthalic dianhydride, 3,3,4´,4´-oxydiphthalic dianhydride, 4,4´-hexafluoroisopropyl phthalic anhydride, and bisphenol A type diether dianhydride; and / or The poor solvent is selected from one or more of water, methanol, ethanol, isopropanol, and acetone.

6. The method of claim 1, wherein, In step (2): The mass ratio of the aromatic diamine to the aromatic dianhydride is (0.97-1.03):1, preferably (0.98-1.01):1; The total mass percentage of the aromatic diamine and the aromatic dianhydride in the polyamic acid solution is 5-30%; The volume ratio of the polyamic acid solution to the poor solvent is 1:5-10; and / or The mass percentage of the polyamic acid salt precursor powder is 5-25%, the mass percentage of the triethylamine is 3-12%, and the mass percentage of the water is 63-92%, based on the total amount of the aqueous polyamic acid salt solution.

7. The method of claim 1, wherein, In step (2): The stirring speed is 250 rpm-1500 rpm, the stirring temperature is 0-10 ℃, and the stirring time is 6-48 h, preferably 6-12 h; After the pulverization, the particle size of the particles in the polyamic acid solution is 50-300 mesh; The washing solution is a mixture of water and ethanol, and preferably, the volume ratio of water to ethanol in the mixture is 5:1 to 1:5; The drying is performed by drying for 12-48 h at a temperature of 45-55 ℃ in a vacuum environment.

8. The method of claim 1, wherein, In step (3): Step (3) is performed by dispersing the core-shell particles and the thermally conductive filler B in the aqueous polyamic acid salt solution by solution blending, treating by ultrasonic treatment and stirring to obtain a mixture, pouring the mixture on a glass plate, performing a doctor blade coating process, performing a film laying and heating drying process to obtain a polymer-based thermally conductive composite film as the polyimide-based thermally conductive composite material; The thermally conductive filler B is composed of one-dimensional materials selected from one or more of multi-walled carbon nanotubes, single-walled carbon nanotubes, double-walled carbon nanotubes, silicon carbide, silver nanowires, copper nanowires, and short carbon fibers; preferably, the particle size distribution of the one-dimensional materials is 20-50 μm, preferably 20-30 μm; The mass percentage of the polymer B in the mixture is 1-20 wt%, preferably 5-10 wt%; The mass percentage of the core-shell particles in all added solid particles is preferably 1-30 wt%; The mass percentage of the heat-conducting filler B in all added solid particles is 1-30 wt%.

9. The method of claim 8, wherein, In step (3): The ultrasonic treatment is for 3-20 min under the condition of 1000 W; The stirring speed is 500-2500 rpm, and the stirring time is 1-6 h; The thickness of the wiped film is 100-500 μm; The heating drying is performed by sequentially maintaining at 60-70℃ for 2-4 h, at 80-90℃ for 2-4 h, at 120-130℃ for 2-4 h, at 150-180℃ for 2-4 h, and at 200-300℃ for 2-12 h.

10. A polyimide-based heat-conducting composite material prepared by the method according to any one of claims 1-9.

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