A thermally conductive interface material and a method of making the same

Abstract

This invention belongs to the technical field of thermally conductive interface materials, specifically relating to a thermally conductive interface material and its preparation method. The preparation method of this thermally conductive interface material includes the following steps: adding pretreated carbon nanotubes and epoxidized Eucommia ulmoides gum to toluene, then adding a catalyst, and heating to react, thereby obtaining modified carbon nanotubes; adding graphene and N-(3-aminopropyl)-1,4-butanediamine to isopropanol, ball milling to obtain pretreated graphene; adding the modified carbon nanotubes and pretreated graphene to epoxy resin, heating and stirring, adding a curing agent to cure and shape, and cooling to room temperature to obtain the final product. The thermally conductive interface material prepared by this invention possesses high thermal conductivity, low interfacial thermal resistance, excellent tensile properties, tear resistance, and aging and temperature resistance, solving the defects of traditional thermally conductive interface materials such as easy aging and rapid mechanical decay, and is suitable for long-term heat dissipation applications in electronic devices.

Description

Technical Field

[0001] This invention pertains to thermally conductive interface materials, specifically relating to a thermally conductive interface material and its preparation method. Background Technology

[0002] With the rapid development of electronic devices towards higher integration, miniaturization, and higher power, the heat generated during device operation is increasing dramatically. Heat accumulation can easily lead to performance degradation, shortened lifespan, or even failure. Thermal interface materials, as key materials for filling the tiny gaps between electronic devices and heat dissipation devices, can effectively reduce interface thermal resistance and improve heat dissipation efficiency, making them a core component for ensuring the stable operation of electronic devices.

[0003] Epoxy resin is an ideal matrix for preparing thermally conductive interface materials due to its excellent mechanical properties, adhesive properties, chemical corrosion resistance, and molding processability. However, pure epoxy resin has an extremely low thermal conductivity, which cannot meet the heat dissipation requirements of high-power electronic devices, necessitating modification by adding thermally conductive fillers. Carbon nanotubes and graphene possess ultra-high intrinsic thermal conductivity, making them excellent fillers for epoxy resin-based thermally conductive composites. However, carbon nanotubes have an inert surface and are prone to aggregation, making it difficult to form continuous thermally conductive pathways in epoxy resin. They also exhibit poor interfacial bonding with the matrix and high interfacial thermal resistance. Graphene sheets have strong van der Waals forces, which easily lead to stacking and aggregation, resulting in the breakage of the thermally conductive network. Furthermore, epoxy resin-based thermally conductive materials modified with ordinary fillers generally suffer from poor toughness, easy cracking, and insufficient aging resistance. After long-term use, their thermal conductivity and mechanical properties deteriorate significantly, limiting their application range.

[0004] To address the aforementioned issues, existing technologies often employ physical blending of single fillers or simple surface modification, which struggles to simultaneously achieve uniform dispersion of the filler in the matrix, low interfacial thermal resistance, high thermal conductivity, and good mechanical stability. Therefore, developing an epoxy resin-based thermally conductive interface material that combines high thermal conductivity, low interfacial thermal resistance, excellent toughness, and aging resistance has significant application value. Summary of the Invention

[0005] The primary objective of this invention is to provide a method for preparing a thermally conductive interface material. By performing two-step modification on carbon nanotubes and amination pretreatment on graphene, a "one-dimensional-two-dimensional" synergistic thermally conductive network is constructed, which solves the problems of easy agglomeration of fillers, high interfacial thermal resistance, poor material toughness, and insufficient aging resistance.

[0006] The second objective of this invention is to provide a thermally conductive interface material that combines high thermal conductivity, low interfacial thermal resistance, excellent mechanical properties, and aging resistance, making it suitable for heat dissipation in high-power electronic devices.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for preparing a thermally conductive interface material includes the following steps: (1) Carbon nanotubes were dispersed in an anhydrous ethanol solution of 4-pyridylthioacetic acid, sonicated, filtered, washed and dried to obtain pretreated carbon nanotubes. (2) Take Eucommia gum and add it to deionized water. After heating and stirring, add acetic acid, raise the temperature and add hydrogen peroxide to continue the reaction to obtain epoxidized Eucommia gum. (3) Add the pretreated carbon nanotubes and epoxidized eucommia gum to toluene, then add a catalyst and heat to react to obtain modified carbon nanotubes; (4) Add graphene and N-(3-aminopropyl)-1,4-butanediamine to isopropanol, and ball mill to obtain pretreated graphene; (5) Add the modified carbon nanotubes and pretreated graphene to the epoxy resin, heat and stir, add curing agent to cure and shape, and cool to room temperature to obtain the product.

[0008] Further, in step (1), the mass ratio of carbon nanotubes to 4-pyridylthioacetic acid is (3-6):(0.1-0.15); the concentration of the anhydrous ethanol solution of 4-pyridylthioacetic acid is 0.05-0.12 mg / mL; and the ultrasonication time is 3-5 h.

[0009] Further, in step (2), the ratio of Eucommia gum to deionized water is 1g:20mL; the ratio of Eucommia gum, acetic acid, and hydrogen peroxide is 3g:3-5mL:8-10mL.

[0010] Further, in step (2), the heating and stirring temperature is 40-45℃ and the time is 30-40 min; the temperature of the heating is 50-60℃ and the reaction time is 4-6 h.

[0011] Further, in step (3), the ratio of carbon nanotubes, epoxidized eucommia gum, toluene, and catalyst used in the pretreatment is 2.5-3.0g: 3-4g: 80mL: 0.03-0.05g, and the catalyst is tetrabutylammonium bromide.

[0012] Further, in step (4), the mass ratio of graphene, N-(3-aminopropyl)-1,4-butanediamine, and isopropanol is 1:(3-4):50; the ball milling speed is 300-350 rpm and the time is 48-56 h.

[0013] Further, in step (5), the mass ratio of the modified carbon nanotubes, pretreated graphene, and epoxy resin is 1:(1-2):(15-20), the amount of curing agent is 30%-40% of the mass of epoxy resin, the curing agent is curing agent 5010B, and the epoxy resin is epoxy resin E51.

[0014] Further, the heating reaction in step (3) is carried out at a temperature of 60-70°C for 3-5 hours; the heating and stirring in step (5) is carried out at a temperature of 50-60°C for 1-3 hours.

[0015] A thermally conductive interface material is prepared according to the preparation method described above.

[0016] Compared with the prior art, the main advantages of the present invention are as follows: 1. This invention provides a method for preparing a thermally conductive interface material, wherein modified carbon nanotubes are obtained by modifying carbon nanotubes. Due to their surface inertness and tendency to aggregate, carbon nanotubes are difficult to form continuous thermally conductive pathways in an epoxy resin matrix, and their large interfacial gap and high interfacial thermal resistance limit the improvement of the composite material's thermal conductivity. This invention prepares modified carbon nanotubes through a two-step modification process. The pyridine ring in 4-pyridylthioacetic acid forms a stable non-covalent interaction with the conjugated aromatic ring on the carbon nanotube surface through π-π stacking. Simultaneously, the carboxyl groups can be adsorbed onto defect sites on the carbon nanotube surface through hydrogen bonding. This modification completely preserves the intrinsic structure of the carbon nanotubes. After pretreatment, the carboxyl groups on the carbon nanotube surface can be activated under the action of a catalyst, thereby attacking the epoxy groups on the epoxidized Eucommia ulmoides molecular chains, achieving directional grafting of the epoxidized Eucommia ulmoides molecular chains onto the carbon nanotube surface.

[0017] The above-mentioned modification process, on the one hand, breaks up agglomeration through pretreatment, and the uniform dispersion of modified carbon nanotubes can avoid local overheating, further extending the service life of the thermally conductive interface material; on the other hand, the covalent grafting of epoxidized eucommia gum reduces the interfacial thermal resistance and enhances its surface polarity, which can form a good interfacial bond with the epoxy resin matrix; at the same time, the flexible segments of epoxidized eucommia gum can play a buffering role, alleviate stress concentration inside the composite material, improve the toughness and impact resistance of the material, and prevent cracking during molding or use. In addition, both 4-pyridylthioacetic acid and epoxidized eucommia gum have good aging resistance and temperature resistance, which can improve the stability of modified carbon nanotubes in the composite material system and prevent them from affecting thermal conductivity and mechanical properties due to oxidation and degradation during long-term use.

[0018] 2. This invention provides a method for preparing a thermally conductive interface material. During the preparation process, pretreated graphene is introduced: grafting with N-(3-aminopropyl)-1,4-butanediamine not only introduces polar amino groups into the graphene, but its molecular chains also act as steric hindrance, effectively inhibiting the aggregation between graphene sheets and ensuring the continuity and stability of the thermally conductive network. Its two-dimensional sheets can act as a "bridge" for the thermally conductive network, overlapping with the one-dimensional structure of modified carbon nanotubes, filling the gaps between the modified carbon nanotubes, and constructing a "one-dimensional-two-dimensional" synergistic thermally conductive network. This enables rapid heat conduction and dispersion, significantly improving the thermal conductivity efficiency of the composite material. The amino groups (-NH2) grafted onto the surface of pretreated graphene have strong reactivity. They can undergo ring-opening addition reactions with the epoxy groups on the epoxy resin molecular chain to form stable covalent bonds. At the same time, they can form hydrogen bonds with the epoxy groups and hydroxyl groups remaining on the surface of modified carbon nanotubes, further strengthening the interfacial bonding between aminated graphene and epoxy resin matrix, and between aminated graphene and modified carbon nanotubes, and reducing interfacial gaps.

[0019] 3. The thermal interface material prepared by this invention has high thermal conductivity, low interfacial thermal resistance, excellent tensile properties and tear resistance. It does not pulverize or crack after aging, and the thermal resistance value changes little. It solves the defects of traditional thermal interface materials that are easy to age and have rapid mechanical decay, and is suitable for long-term heat dissipation applications of electronic devices. Attached Figure Description

[0020] Figure 1 This is a scanning electron microscope image of the modified carbon nanotubes obtained in Example 1 of the present invention; Figure 2 This is a scanning electron microscope image of the pretreated graphene obtained in Example 1 of the present invention. Detailed Implementation

[0021] The technical solution of the present invention will be further described below with reference to specific embodiments. However, those skilled in the art should understand that the following embodiments are only for illustrating the present invention and should not be regarded as limiting the present invention. Specific conditions not specified in the embodiments are performed according to conventional conditions or conditions recommended by the manufacturer. Unless otherwise specified, the reagents or instruments used are all conventional products obtained through commercial channels. Example 1

[0022] A method for preparing a thermally conductive interface material includes the following steps: (1) Carbon nanotubes were dispersed in an anhydrous ethanol solution of 4-pyridylthioacetic acid (concentration of 0.1 mg / mL), wherein the mass ratio of carbon nanotubes to 4-pyridylthioacetic acid in the anhydrous ethanol solution of 4-pyridylthioacetic acid was 5:0.12; the mixture was sonicated for 4 h, and then filtered, washed and dried to obtain pretreated carbon nanotubes. (2) Take Eucommia gum and add it to deionized water. The ratio of Eucommia gum to deionized water is 1g:20mL. Heat and stir at 45℃ for 35min, then add acetic acid. Raise the temperature to 55℃ and add hydrogen peroxide. The ratio of Eucommia gum, acetic acid and hydrogen peroxide is 3g:4mL:9mL. Control the hydrogen peroxide addition time to 30min. Continue the reaction for 5h. Distill under reduced pressure to obtain epoxidized Eucommia gum. (3) Add the pretreated carbon nanotubes and epoxidized eucommia gum to toluene, and then add the catalyst (tetrabutylammonium bromide). The ratio of the amount of pretreated carbon nanotubes, epoxidized eucommia gum, toluene and tetrabutylammonium bromide is 2.8g:3.5g:80mL:0.04g. Heat the mixture at 65℃ for 4h, and remove the solvent by rotary evaporation to obtain modified carbon nanotubes. (4) Graphene and N-(3-aminopropyl)-1,4-butanediamine were added to isopropanol, wherein the mass ratio of graphene, N-(3-aminopropyl)-1,4-butanediamine and isopropanol was 1:3.5:50. The mixture was ball-milled at 320 rpm for 50 h, and then filtered, washed and vacuum dried to obtain pretreated graphene. (5) The modified carbon nanotubes and pretreated graphene are added to epoxy resin E51, wherein the mass ratio of modified carbon nanotubes, pretreated graphene and epoxy resin E51 is 1:1.5:18. The mixture is heated and stirred at 55°C for 2 hours. Then, curing agent 5010B is added, wherein the amount of curing agent is 35% of the mass of epoxy resin E51. The mixture is cured and cooled to room temperature to obtain the final product.

[0023] This embodiment 1 also provides a thermally conductive interface material, which is prepared according to the preparation method described above. Example 2

[0024] A method for preparing a thermally conductive interface material includes the following steps: (1) Carbon nanotubes were dispersed in an anhydrous ethanol solution of 4-pyridylthioacetic acid (concentration of 0.05 mg / mL), wherein the mass ratio of carbon nanotubes to 4-pyridylthioacetic acid in the anhydrous ethanol solution of 4-pyridylthioacetic acid was 3:0.1; the mixture was sonicated for 3 h, and then filtered, washed and dried to obtain pretreated carbon nanotubes. (2) Take Eucommia gum and add it to deionized water. The ratio of Eucommia gum to deionized water is 1g:20mL. Heat and stir at 40℃ for 40min, then add acetic acid. Raise the temperature to 50℃ and add hydrogen peroxide. The ratio of Eucommia gum, acetic acid and hydrogen peroxide is 3g:3mL:8mL. Control the dropping time of hydrogen peroxide to 30min, continue the reaction for 4h, and distill under reduced pressure to obtain epoxidized Eucommia gum. (3) Add the pretreated carbon nanotubes and epoxidized eucommia gum to toluene, and then add the catalyst (tetrabutylammonium bromide). The ratio of the amount of pretreated carbon nanotubes, epoxidized eucommia gum, toluene and tetrabutylammonium bromide is 2.5g:3g:80mL:0.03g. Heat the mixture at 60℃ for 5h, and remove the solvent by rotary evaporation to obtain modified carbon nanotubes. (4) Graphene and N-(3-aminopropyl)-1,4-butanediamine were added to isopropanol, wherein the mass ratio of graphene, N-(3-aminopropyl)-1,4-butanediamine and isopropanol was 1:3:50. The mixture was ball-milled at 300 rpm for 56 h, and then filtered, washed and vacuum dried to obtain pretreated graphene. (5) The modified carbon nanotubes and pretreated graphene are added to epoxy resin E51, wherein the mass ratio of modified carbon nanotubes, pretreated graphene and epoxy resin E51 is 1:1:15. The mixture is heated and stirred at 50°C for 3 hours. Then, curing agent 5010B is added, wherein the amount of curing agent is 30% of the mass of epoxy resin E51. The mixture is cured and cooled to room temperature to obtain the final product.

[0025] This embodiment 2 also provides a thermally conductive interface material, which is prepared according to the preparation method described above. Example 3

[0026] A method for preparing a thermally conductive interface material includes the following steps: (1) Carbon nanotubes were dispersed in an anhydrous ethanol solution of 4-pyridylthioacetic acid (concentration of 0.12 mg / mL), wherein the mass ratio of carbon nanotubes to 4-pyridylthioacetic acid in the anhydrous ethanol solution of 4-pyridylthioacetic acid was 6:0.15; after sonication for 5 h, the carbon nanotubes were obtained by filtration, washing and drying. (2) Take Eucommia gum and add it to deionized water. The ratio of Eucommia gum to deionized water is 1g:20mL. Heat and stir at 45℃ for 30min, then add acetic acid. Raise the temperature to 60℃ and add hydrogen peroxide. The ratio of Eucommia gum, acetic acid and hydrogen peroxide is 3g:5mL:10mL. Control the dropping time of hydrogen peroxide to 30min, continue the reaction for 6h, and distill under reduced pressure to obtain epoxidized Eucommia gum. (3) Add the pretreated carbon nanotubes and epoxidized eucommia gum to toluene, and then add the catalyst (tetrabutylammonium bromide). The ratio of the amount of pretreated carbon nanotubes, epoxidized eucommia gum, toluene and tetrabutylammonium bromide is 3.0g:4g:80mL:0.05g. Heat the mixture at 70℃ for 3h, and remove the solvent by rotary evaporation to obtain modified carbon nanotubes. (4) Graphene and N-(3-aminopropyl)-1,4-butanediamine were added to isopropanol, wherein the mass ratio of graphene, N-(3-aminopropyl)-1,4-butanediamine and isopropanol was 1:4:50. The mixture was ball-milled at 350 rpm for 48 h, and then filtered, washed and vacuum dried to obtain pretreated graphene. (5) The modified carbon nanotubes and pretreated graphene are added to epoxy resin E51, wherein the mass ratio of modified carbon nanotubes, pretreated graphene and epoxy resin E51 is 1:2:20. The mixture is heated and stirred at 60°C for 1 hour, and then curing agent 5010B is added, wherein the amount of curing agent is 40% of the mass of epoxy resin E51. The mixture is cured and cooled to room temperature to obtain the final product.

[0027] This embodiment 3 also provides a thermally conductive interface material, which is prepared according to the preparation method described above.

[0028] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that the modified carbon nanotubes in step (5) are replaced with carbon nanotubes and epoxidized Eucommia ulmoides gum; otherwise, they are the same as in Example 1.

[0029] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that the pretreated graphene in step (5) is replaced with graphene; otherwise, it is the same as Example 1.

[0030] Test case (1) Scanning electron microscopy was performed on the modified carbon nanotubes obtained in Example 1 of the present invention and the pretreated graphene. The results are as follows: Figure 1 and Figure 2 As shown.

[0031] (2) The thermal conductivity of the interface materials obtained in Examples 1-3 and Comparative Examples 1-2 of the present invention was determined according to ASTM D5470. The elongation at break of the interface materials obtained in Examples 1-3 and Comparative Examples 1-2 of the present invention was tested according to GB / T528-2009. The tear resistance of the interface materials obtained in Examples 1-3 and Comparative Examples 1-2 of the present invention was tested according to GB / T529-2008.

[0032] (3) The interface materials obtained in Examples 1-3 and Comparative Examples 1-2 of the present invention were aged at 125°C for 1000 hours. The thermal conductivity after aging was tested, the change rate of thermal conductivity after aging was statistically analyzed, and it was observed whether the interface materials after aging showed signs of pulverization and cracking. The above results are shown in Table 1.

[0033] As shown in Table 1, the thermally conductive interface materials prepared in Examples 1-3 of the present invention have significantly higher elongation at break, tear strength, and thermal conductivity than those in Comparative Examples 1-2. After aging at 125℃ for 1000h, the thermal conductivity changes little and there is no pulverization or cracking, demonstrating excellent mechanical properties, thermal conductivity, and high-temperature stability.

[0034] Compared to Example 1, Comparative Example 1 showed a decrease in both elongation at break and tear strength, indicating that the epoxidized eucommia gum flexible chain grafted onto the surface of the modified carbon nanotubes effectively alleviated stress concentration. Comparative Example 2 also showed a decrease in both elongation at break and tear strength to varying degrees compared to Example 1. This is because the amino groups grafted onto the surface of the pretreated graphene can form strong interfacial bonds with the epoxy resin and modified carbon nanotubes, reducing interfacial gaps.

[0035] Compared to Example 1, the thermal conductivity of Comparative Examples 1 and 2 was significantly reduced. This result indicates that, on the one hand, the epoxidized Eucommia ulmoides grafted onto the surface of the modified carbon nanotubes can reduce interfacial thermal resistance, and the modified carbon nanotubes exhibit good interfacial bonding with the epoxy resin matrix. On the other hand, the N-(3-aminopropyl)-1,4-butanediamine introduced into the pretreated graphene can act as a steric hindrance, effectively inhibiting the aggregation between graphene sheets and ensuring the continuity and stability of the thermally conductive network. Furthermore, it can also serve as a bridge in the thermally conductive network, constructing a "one-dimensional-two-dimensional" synergistic thermally conductive network with the one-dimensional structure of the modified carbon nanotubes, achieving rapid heat conduction and dispersion, and effectively improving the thermal conductivity efficiency of the composite material.

[0036] After high-temperature aging, the thermal conductivity of Examples 1-3 showed a small change rate, with no cracking or pulverization. Comparative Example 1, compared to Example 1, exhibited poorer aging resistance, with a larger change in thermal conductivity after aging, and showed cracking and pulverization. This is because the 4-pyridylthioacetic acid and epoxidized eucommia gum introduced into the modified carbon nanotubes both possess good aging resistance and temperature resistance, which can improve the stability of the modified carbon nanotubes in the composite material system, preventing their thermal conductivity and mechanical properties from being affected by oxidation and degradation during long-term use. Comparative Example 2, which replaced the pretreated graphene with graphene, also showed inferior aging resistance compared to Example 1. This is because the N-(3-aminopropyl)-1,4-butanediamine introduced into the pretreated carbon nanotubes not only maintains the stability of the thermally conductive network but also works synergistically with the modified carbon nanotubes to form a thermally conductive network, improving the material's thermal conductivity efficiency.

[0037] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. The basic principles and main features of the present invention have been described above with specific implementation schemes. Based on the present invention, some modifications or substitutions can be made, but these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of protection claimed by the present invention.

Claims

1. A method for preparing a thermally conductive interface material, characterized in that, Includes the following steps: (1) Carbon nanotubes were dispersed in an anhydrous ethanol solution of 4-pyridylthioacetic acid, sonicated, filtered, washed and dried to obtain pretreated carbon nanotubes. (2) Take Eucommia gum and add it to deionized water. After heating and stirring, add acetic acid, raise the temperature and add hydrogen peroxide to continue the reaction to obtain epoxidized Eucommia gum. (3) Add the pretreated carbon nanotubes and epoxidized eucommia gum to toluene, then add a catalyst and heat to react to obtain modified carbon nanotubes; (4) Add graphene and N-(3-aminopropyl)-1,4-butanediamine to isopropanol, and ball mill to obtain pretreated graphene; (5) Add the modified carbon nanotubes and pretreated graphene to the epoxy resin, heat and stir, add curing agent to cure and shape, and cool to room temperature to obtain the product.

2. The method for preparing a thermally conductive interface material according to claim 1, characterized in that, In step (1), the mass ratio of carbon nanotubes to 4-pyridylthioacetic acid is (3-6):(0.1-0.15); the concentration of the anhydrous ethanol solution of 4-pyridylthioacetic acid is 0.05-0.12 mg / mL; and the ultrasonication time is 3-5 h.

3. The method for preparing a thermally conductive interface material according to claim 1, characterized in that, In step (2), the ratio of Eucommia gum to deionized water is 1g:20mL; the ratio of Eucommia gum, acetic acid, and hydrogen peroxide is 3g:3-5mL:8-10mL.

4. The method for preparing a thermally conductive interface material according to claim 1, characterized in that, The heating and stirring temperature in step (2) is 40-45℃, and the time is 30-40 min; the temperature of the heating is 50-60℃, and the reaction time is 4-6 h.

5. The method for preparing a thermally conductive interface material according to claim 1, characterized in that, In step (3), the ratio of carbon nanotubes, epoxidized eucommia gum, toluene, and catalyst used in the pretreatment is 2.5-3.0g: 3-4g: 80mL: 0.03-0.05g, and the catalyst is tetrabutylammonium bromide.

6. The method for preparing a thermally conductive interface material according to claim 1, characterized in that, In step (4), the mass ratio of graphene, N-(3-aminopropyl)-1,4-butanediamine, and isopropanol is 1:(3-4):50; the ball milling speed is 300-350 rpm and the time is 48-56 h.

7. The method for preparing a thermally conductive interface material according to claim 1, characterized in that, In step (5), the mass ratio of the modified carbon nanotubes, pretreated graphene, and epoxy resin is 1:(1-2):(15-20), and the amount of curing agent is 30%-40% of the mass of epoxy resin; the curing agent is curing agent 5010B; and the epoxy resin is epoxy resin E51.

8. The method for preparing a thermally conductive interface material according to claim 1, characterized in that, The heating reaction in step (3) is carried out at a temperature of 60-70℃ for 3-5 hours; the heating and stirring in step (5) is carried out at a temperature of 50-60℃ for 1-3 hours.

9. A thermally conductive interface material, characterized in that, It is prepared according to any one of claims 1-8.

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