High-thermal-conductivity graphene composite film for electronic components and preparation method thereof

Abstract

The application belongs to the technical field of graphene materials, and particularly relates to a high-thermal-conductivity graphene composite film for electronic components and a preparation method thereof. The high-thermal-conductivity graphene composite film for electronic components comprises the following raw materials in mass fractions: 80-90 parts of a thermoplastic polyurethane elastomer, 510 parts of expanded graphite, 12 parts of carbon quantum dots, 0.3-0.8 parts of carbon nanotubes, 150-300 parts of a solvent and 0.1-0.3 parts of a dispersing agent; the expanded graphite is prepared by a chemical oxidation method. The graphene composite film prepared by the application has high in-plane and vertical thermal conductivity coefficients and excellent mechanical properties, and is particularly suitable for preparing insulated gate bipolar transistors.

Description

Technical Field

[0001] This invention belongs to the field of thermally conductive thin film technology, specifically relating to a high thermal conductivity graphene composite thin film for electronic components and its preparation method. Background Technology

[0002] Thermal interface materials (TIMs) are widely used between heat-generating elements and heat dissipation structures to fill microscopic gaps, reduce contact thermal resistance, and thus improve overall heat dissipation efficiency. In recent years, graphene has become a popular choice for developing high-performance thermal management materials due to its extremely high intrinsic thermal conductivity, excellent mechanical strength, and good chemical stability. A traditional approach is to composite graphene with a polymer matrix to obtain novel TIMs that combine flexibility and high thermal conductivity.

[0003] However, in traditional composite processes, graphene is often randomly dispersed in the matrix, leading to obstructed phonon transport paths, high interfacial thermal resistance, and difficulty in fully realizing its thermal conductivity potential, ultimately limiting the improvement of the overall thermal conductivity of the composite material. Existing technologies have found an effective method to construct graphene thermally conductive networks with oriented structures. For example, by arranging graphene sheets in an orderly manner on the substrate surface through methods such as solution film formation, blade coating, or filtration, the thermal conductivity of the material in the planar direction (in-plane) can be significantly enhanced. Although such methods are highly effective in improving lateral thermal conductivity, the improvement in thermal conductivity perpendicular to the film surface (through the plane) remains very limited.

[0004] Chinese patent CN118725542B discloses a flexible, high thermal conductivity graphene-filled polyurethane composite film and its preparation method. The material system contains graphene, carbon quantum dots, and a one-dimensional film-forming agent. The graphene, carbon quantum dots, and one-dimensional film-forming agent are interconnected, interpenetrated, and stacked to form a complex three-dimensional network structure. The filler particles are more uniformly and densely distributed in the polyurethane resin matrix, which significantly improves the thermal conductivity of the obtained flexible, high thermal conductivity graphene-filled polyurethane composite film.

[0005] IGBTs (Insulated Gate Bipolar Transistors) are widely used in high-power applications such as electric vehicles, rail transportation, and industrial frequency converters, generating a significant amount of heat during switching. However, the bidirectional thermal conductivity of currently available graphene composite films cannot meet market demands. Furthermore, especially in the automotive and heavy industry sectors, IGBT modules frequently face harsh conditions such as vibration and shock. Excellent bending resistance ensures that the graphene composite film maintains structural integrity and functional stability under these dynamic environments, preventing failures caused by the propagation of microcracks.

[0006] Therefore, there is an urgent need to develop a graphene composite film material with excellent bidirectional thermal conductivity and mechanical properties, and its preparation method. Summary of the Invention

[0007] The purpose of this invention is to provide a high thermal conductivity graphene composite film for electronic components and its preparation method.

[0008] To achieve the above objectives, the present invention provides the following technical solution: A high thermal conductivity graphene composite film for electronic components comprises the following raw materials in parts by weight: 80-90 parts thermoplastic polyurethane elastomer, 5 parts expanded graphite. 10 portions, carbon quantum dots 1 2 parts, carbon nanotubes 0.3-0.8 parts, solvent 150-300 parts and dispersant 0.1-0.3 parts; the expanded graphite is prepared by chemical oxidation.

[0009] Preferably, the method for preparing the expanded graphite includes the following steps: (1) Add an oxidant to natural flake graphite and add an intercalating agent dropwise. Stir for 50-60 minutes under a constant temperature water bath at 30-40℃, and then cool to room temperature to obtain a mixture. (2) The mixture was slowly added to deionized water, soaked, washed with water until neutral, and freeze-dried to obtain expandable graphite; (3) Expandable graphite is expanded to obtain expanded graphite.

[0010] Preferably, the oxidant is potassium permanganate.

[0011] Preferably, the intercalating agent comprises concentrated sulfuric acid, glacial acetic acid and concentrated phosphoric acid in a volume ratio of (11-13):(7-9):(4-6).

[0012] Preferably, the mass ratio of the flake graphite to potassium permanganate is 5:(0.75-1.0).

[0013] Preferably, the mass-to-volume ratio of the flake graphite to the intercalating agent is 5g:20-24mL.

[0014] Preferably, the particle size of the natural flake graphite is 0.2-0.3 mm.

[0015] The thermal conductivity of commercially available expanded graphite composite films cannot meet market requirements. The expanded graphite prepared in this invention can significantly improve the in-plane thermal conductivity of graphene composite films, and also improves the perpendicular thermal conductivity to a certain extent. Analysis shows that the expanded graphite prepared in this invention, by precisely controlling the reaction conditions in the chemical oxidation process, can better control the number and distribution of molecules inserted between graphite layers, which helps to generate fewer structural defects in the subsequent expansion process, thereby maintaining the high integrity of the graphene sheets and improving thermal conductivity.

[0016] Preferably, the carbon nanotubes include double-walled carbon nanotubes, double-walled carbon nanotubes and whisker carbon nanotubes in a mass ratio of 1:(1.2-1.4):(0.5-0.7).

[0017] This invention utilizes a composite of three types of carbon nanotubes to improve the vertical thermal conductivity of graphene composite films. Analysis shows that carbon nanotubes can form a three-dimensional interconnected network between graphene layers. Shorter carbon nanotubes help fill the tiny gaps between graphene sheets, while longer carbon nanotubes can span greater distances, providing a more direct heat conduction path. Good interfacial contact between carbon nanotubes and graphene is key to achieving high vertical thermal conductivity. The three types of carbon nanotubes provide diverse surface properties, increasing the contact area with graphene and reducing interfacial thermal resistance.

[0018] Preferably, the thermoplastic polyurethane elastomer comprises TPU of type 5080A, TPU of type 786E, and TPU of type 688A10N in a mass ratio of 1:(0.3-0.5):(1.4-1.7).

[0019] This invention utilizes a specific type of thermoplastic polyurethane elastomer, which improves both the bidirectional thermal conductivity and bending properties of graphene composite films. Analysis shows that this particular thermoplastic polyurethane elastomer exhibits excellent interfacial compatibility, forming a good interfacial bond with expanded graphite, carbon quantum dots, and carbon nanotubes. This facilitates the adsorption of carbon nanotubes on the graphene surface, better encapsulates and disperses graphene and other nanomaterials during mixing, reduces voids and defects, and ensures the continuity and uniformity of the heat conduction path. The synergistic effect of expanded graphite, carbon quantum dots, and carbon nanotubes in the TPU matrix not only enhances the thermal conductivity of the material but also improves its mechanical properties.

[0020] This invention also provides a method for preparing a high thermal conductivity graphene composite film for electronic components, comprising the following steps: S1: Expanded graphite, carbon quantum dots, and carbon nanotubes are added to an organic solvent, dispersed in a sand mill, and milled to exfoliate the expanded graphite, obtaining a primary exfoliated material. S2: Add the primary stripping material to a high-pressure homogenizer for secondary stripping to obtain the secondary stripping material; S3: Add thermoplastic polyurethane elastomer to the secondary peeling material, mix evenly, coat it on the surface of the substrate, dry and peel it off to obtain a high thermal conductivity graphene composite film for electronic components.

[0021] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows: 1. This invention uses expanded graphite prepared by chemical oxidation, and combines it with three types of carbon nanotubes to improve the in-plane thermal conductivity and vertical thermal conductivity of graphene composite films.

[0022] 2. This invention uses a specific type of thermoplastic polyurethane elastomer, which can improve the bidirectional thermal conductivity of the graphene composite film while also improving its bending performance. Detailed Implementation

[0023] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] All raw materials used in the following embodiments of the present invention are commercially available products: The natural flake graphite has a particle size of 0.25mm and a carbon content of 99%. Qingdao Nanshu Hongda Graphite Products Co., Ltd.

[0025] Thermoplastic polyurethane elastomers: DuPont's TPU model 5080A (standard grade); DuPont's TPU model 786E (standard grade); BASF's TPU model 688A10N.

[0026] Double-walled carbon nanotubes, 2-4 nm in diameter and 50 μm in length, item number: 100222.

[0027] Multi-walled carbon nanotubes, 0.5-2 micrometers in length and 20-30 nm in diameter. Product number 100270.

[0028] Whisker carbon nanotubes, outer diameter: 20-200nm, inner diameter: 2-5nm, length: 1-15um. Product number 104268.

[0029] Carbon quantum dots, purchased from Jiangsu Xianfeng Nanomaterials Technology Co., Ltd., item number 104848.

[0030] Example 1 This embodiment provides a high thermal conductivity graphene composite film for electronic components, comprising the following raw materials in parts by weight: 85 parts thermoplastic polyurethane elastomer, 8 parts expanded graphite, 1.5 parts carbon quantum dots, 0.6 parts carbon nanotubes, 200 parts solvent, and 0.2 parts dispersant. The thermoplastic polyurethane elastomer includes TPU of type 5080A, type 786E, and type 688A10N in a mass ratio of 1:0.4:1.6. The carbon nanotubes include double-walled carbon nanotubes, double-walled carbon nanotubes, and whisker carbon nanotubes in a mass ratio of 1:1.3:0.6.

[0031] The method for preparing the expanded graphite includes the following steps: (1) Add potassium permanganate as an oxidant to natural flake graphite, with a mass ratio of natural flake graphite to potassium permanganate of 5:0.9; and add an intercalating agent, which consists of 98wt% concentrated sulfuric acid, 99wt% glacial acetic acid and 85wt% concentrated phosphoric acid in a volume ratio of 12:8:5, with a mass-volume ratio of flake graphite to intercalating agent of 5g:22mL; stir for 55min under a constant temperature water bath at 35℃, and cool to room temperature to obtain a mixture; (2) Slowly add the mixture to three times the volume of deionized water, soak at 35°C for 45 min, wash with water until neutral, freeze dry to obtain expandable graphite; (3) Expandable graphite is expanded at a temperature of 1000℃ for 45s to obtain expanded graphite.

[0032] The method for preparing the high thermal conductivity graphene composite film for electronic components includes the following steps: S1: Expanded graphite, carbon quantum dots, and carbon nanotubes were added to N-methylpyrrolidone, and Span 60 was added. The mixture was dispersed at 2500 rpm for 30 min, then milled in a sand mill for 12 h to exfoliate the expanded graphite, obtaining the primary exfoliated material. S2: Add the primary stripping material to a high-pressure homogenizer for secondary stripping. Homogenize 6 times under a pressure of 50MPa to obtain the secondary stripping material. S3: Add thermoplastic polyurethane elastomer to the secondary peeling material, mix evenly at 4000 rpm, coat it on the substrate surface with a coating thickness of 3000 μm, dry at 60°C and then peel it off to obtain a high thermal conductivity graphene composite film for electronic components.

[0033] Example 2 This embodiment provides a high thermal conductivity graphene composite film for electronic components, comprising the following raw materials in parts by weight: 80 parts thermoplastic polyurethane elastomer, 10 parts expanded graphite, 1 part carbon quantum dots, 0.8 parts carbon nanotubes, 150 parts solvent, and 0.3 parts dispersant. The thermoplastic polyurethane elastomer includes TPU of type 5080A, type 786E, and type 688A10N in a mass ratio of 1:(0.3-0.5):(1.4-1.7). The carbon nanotubes include double-walled carbon nanotubes, double-walled carbon nanotubes, and whisker carbon nanotubes in a mass ratio of 1:1.2:0.7.

[0034] The method for preparing the expanded graphite includes the following steps: (1) Add potassium permanganate as an oxidant to natural flake graphite, with a mass ratio of natural flake graphite to potassium permanganate of 5:0.75; and add an intercalating agent, which consists of 98wt% concentrated sulfuric acid, 99wt% glacial acetic acid, and 85wt% concentrated phosphoric acid in a volume ratio of 13:7:6, with a mass-volume ratio of flake graphite to intercalating agent of 5g:20mL; stir for 50min under a constant temperature water bath at 40℃, and cool to room temperature to obtain a mixture; (2) The mixture was slowly added to four times the volume of deionized water, soaked at 30°C for 50 min, washed with water until neutral, and freeze-dried to obtain expandable graphite; (3) Expandable graphite is expanded at a temperature of 1000℃ for 40s to obtain expanded graphite.

[0035] The method for preparing the high thermal conductivity graphene composite film for electronic components includes the following steps: S1: Expanded graphite, carbon quantum dots, and carbon nanotubes were added to N-methylpyrrolidone, and Span 60 was added. The mixture was dispersed at 2500 rpm for 30 min, then milled in a sand mill for 12 h to exfoliate the expanded graphite, obtaining the primary exfoliated material. S2: Add the primary stripping material to a high-pressure homogenizer for secondary stripping. Homogenize 6 times under a pressure of 50MPa to obtain the secondary stripping material. S3: Add thermoplastic polyurethane elastomer to the secondary peeling material, mix evenly at 4000 rpm, coat it on the substrate surface with a coating thickness of 3000 μm, dry at 60°C and then peel it off to obtain a high thermal conductivity graphene composite film for electronic components.

[0036] Example 3 This embodiment provides a high thermal conductivity graphene composite film for electronic components, comprising the following raw materials in parts by weight: 90 parts thermoplastic polyurethane elastomer, 5 parts expanded graphite, 2 parts carbon quantum dots, 0.3 parts carbon nanotubes, 300 parts solvent, and 0.1 parts dispersant. The thermoplastic polyurethane elastomer includes TPU of type 5080A, type 786E, and type 688A10N in a mass ratio of 1:(0.3-0.5):(1.4-1.7). The carbon nanotubes include double-walled carbon nanotubes, double-walled carbon nanotubes, and whisker carbon nanotubes in a mass ratio of 1:1.4:0.5.

[0037] The method for preparing the expanded graphite includes the following steps: (1) Add potassium permanganate as an oxidant to natural flake graphite, with a mass ratio of natural flake graphite to potassium permanganate of 5:1; and add an intercalating agent, which consists of 98wt% concentrated sulfuric acid, 99wt% glacial acetic acid and 85wt% concentrated phosphoric acid in a volume ratio of 11:9:4, with a mass-volume ratio of flake graphite to intercalating agent of 5g:24mL; stir for 60min under a constant temperature water bath at 30℃, and cool to room temperature to obtain a mixture; (2) The mixture is slowly added to twice the volume of deionized water, soaked at 40°C for 40 min, washed with water until neutral, and freeze-dried to obtain expandable graphite; (3) Expandable graphite is expanded at a temperature of 1000℃ for 50s to obtain expanded graphite.

[0038] The method for preparing the high thermal conductivity graphene composite film for electronic components includes the following steps: S1: Expanded graphite, carbon quantum dots, and carbon nanotubes were added to N-methylpyrrolidone, and Span 60 was added. The mixture was dispersed at 2500 rpm for 30 min, then milled in a sand mill for 12 h to exfoliate the expanded graphite, obtaining the primary exfoliated material. S2: Add the primary stripping material to a high-pressure homogenizer for secondary stripping. Homogenize 6 times under a pressure of 50MPa to obtain the secondary stripping material. S3: Add thermoplastic polyurethane elastomer to the secondary peeling material, mix evenly at 4000 rpm, coat it on the substrate surface with a coating thickness of 3000 μm, dry at 60°C and then peel it off to obtain a high thermal conductivity graphene composite film for electronic components.

[0039] Comparative Example 1 The difference between this comparative example and Example 1 is that the expanded graphite is a commercially available product purchased from Qingdao Yanhai Carbon Materials Co., Ltd., and its grade is YH. 100.

[0040] Comparative Example 2 The difference between this comparative example and Example 1 is that the intercalating agent includes HClO4 and H3PO4 in a volume ratio of 16:9.

[0041] Comparative Example 3 The difference between this comparative example and Example 1 is that the intercalating agent includes concentrated sulfuric acid, glacial acetic acid and concentrated phosphoric acid in a volume ratio of 14:6:3.

[0042] Comparative Example 4 The difference between this comparative example and Example 1 is that the intercalating agent includes concentrated sulfuric acid, glacial acetic acid and concentrated phosphoric acid in a volume ratio of 10:10:7.

[0043] Comparative Example 5 The difference between this comparative example and Example 1 is that the mass ratio of the flake graphite to potassium permanganate is 5:0.5.

[0044] Comparative Example 6 The difference between this comparative example and Example 1 is that the mass ratio of the flake graphite to potassium permanganate is 5:1.2.

[0045] Comparative Example 7 The difference between this comparative example and Example 1 is that the thermoplastic polyurethane elastomer used is purchased from BASF in Germany, and its grade is 1185A.

[0046] Comparative Example 8 The difference between this comparative example and Example 1 is that the thermoplastic polyurethane elastomer includes TPU of model 1254DU (DuPont, USA), TPU of model 770A15CS000 (DuPont, USA), and TPU of model 1185A (BASF, Germany) in a mass ratio of 1:0.4:1.6.

[0047] Comparative Example 9 The difference between this comparative example and Example 1 is that the thermoplastic polyurethane elastomer includes TPU of type 5080A, type 786E, and type 688A10N in a mass ratio of 0.4:1.6:1.

[0048] Comparative Example 10 The difference between this comparative example and Example 1 is that the thermoplastic polyurethane elastomer includes TPU of type 5080A, type 786E, and type 688A10N in a mass ratio of 1.6:1:0.4.

[0049] Comparative Example 11 The difference between this comparative example and Example 1 is that the carbon nanotubes include double-walled carbon nanotubes and double-walled carbon nanotubes with a mass ratio of 1:1.3.

[0050] Comparative Example 12 The difference between this comparative example and Example 1 is that the carbon nanotubes include double-walled carbon nanotubes, double-walled carbon nanotubes and whisker carbon nanotubes in a mass ratio of 1:1:1.

[0051] Performance testing The performance of the graphene composite films prepared in Examples 1-3 and Comparative Examples 1-12 was tested.

[0052] 1. In-plane thermal conductivity: Measured using the laser method according to the test standard ASTM E1461.

[0053] 2. Vertical thermal conductivity: Determined using the steady-state heat flow method, referring to the test standard ASTM D5470.

[0054] 3. Flexibility: The composite film is bent 180 degrees around a cylinder with a diameter of 10 mm. If there is no damage after 1000 bends, it is considered qualified; otherwise, it is considered unqualified.

[0055] The results are shown in Table 1.

[0056] Table 1 Performance Test Results

[0057] As shown in Table 1, the graphene composite films of Examples 1-3 have excellent bidirectional thermal conductivity, good bending resistance, and their overall performance is significantly improved compared with commercially available products.

[0058] In Comparative Example 1, commercially available expanded graphite was used, which reduced the thermal conductivity and bending resistance of the graphene composite film.

[0059] In Comparative Examples 2-4, changing the proportion or composition of the intercalating agent decreased the thermal conductivity of the graphene composite film. This demonstrates that only by using the intercalating agent with the specific ratio specified in this invention can expanded graphite with fewer structural defects be prepared, allowing the graphite to expand completely without damaging its crystal structure.

[0060] Comparative Examples 5-6 illustrate that in the expansion system of the present invention, flake graphite and potassium permanganate can only achieve complete oxidation at specific dosages while ensuring that over-oxidation is not achieved.

[0061] In Comparative Examples 7-10, changing the type and ratio of thermoplastic polyurethane elastomers resulted in a decrease in the thermal conductivity and flexibility of the graphene composite film.

[0062] Comparative Examples 11-12 illustrate that the composition and ratio of carbon nanotubes affect thermal conductivity.

[0063] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A high thermal conductivity graphene composite film for electronic components, characterized in that, The raw materials include the following parts by weight: 80-90 parts thermoplastic polyurethane elastomer, 5 parts expanded graphite. 10 portions, carbon quantum dots 1 2 parts, carbon nanotubes 0.3-0.8 parts, solvent 150-300 parts and dispersant 0.1-0.3 parts; the expanded graphite is prepared by chemical oxidation.

2. The high thermal conductivity graphene composite film for electronic components according to claim 1, characterized in that, The method for preparing the expanded graphite includes the following steps: (1) Add an oxidant to the flake graphite and add an intercalating agent dropwise. Stir for 50-60 minutes under a constant temperature water bath at 30-40℃, and then cool to room temperature to obtain a mixture. (2) The mixture was slowly added to deionized water, soaked, washed with water until neutral, and freeze-dried to obtain expandable graphite; (3) Expandable graphite is expanded to obtain expanded graphite.

3. The high thermal conductivity graphene composite film for electronic components according to claim 2, characterized in that, The oxidant is potassium permanganate.

4. The high thermal conductivity graphene composite film for electronic components according to claim 3, characterized in that, The intercalating agent comprises concentrated sulfuric acid, glacial acetic acid, and concentrated phosphoric acid in a volume ratio of (11-13):(7-9):(4-6).

5. The high thermal conductivity graphene composite film for electronic components according to claim 4, characterized in that, The mass ratio of the flake graphite to potassium permanganate is 5:(0.75-1.0).

6. The high thermal conductivity graphene composite film for electronic components according to claim 5, characterized in that, The mass-to-volume ratio of the flake graphite to the intercalating agent is 5g:20-24mL.

7. The high thermal conductivity graphene composite film for electronic components according to claim 1, characterized in that, The particle size of the natural flake graphite is 0.2-0.3 mm.

8. The high thermal conductivity graphene composite film for electronic components according to claim 1, characterized in that, The thermoplastic polyurethane elastomer includes TPU of model 5080A, TPU of model 786E, and TPU of model 688A10N in a mass ratio of 1:(0.3-0.5):(1.4-1.7).

9. The high thermal conductivity graphene composite film for electronic components according to claim 1, characterized in that, The carbon nanotubes include double-walled carbon nanotubes, double-walled carbon nanotubes and whisker carbon nanotubes with a mass ratio of 1:(1.2-1.4):(0.5-0.7).

10. A method for preparing a high thermal conductivity graphene composite film for electronic components according to any one of claims 1-9, characterized in that, Includes the following steps: S1: Expanded graphite, carbon quantum dots, and carbon nanotubes are added to an organic solvent, dispersed, and then exfoliated using a sand mill to obtain a primary exfoliated material. S2: Add the primary stripping material to a high-pressure homogenizer for secondary stripping to obtain the secondary stripping material; S3: Add thermoplastic polyurethane elastomer to the secondary peeling material, mix evenly, coat it on the surface of the substrate, dry and peel it off to obtain a high thermal conductivity graphene composite film for electronic components.

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