Heat-conducting interface material with adjustable crosslinking density as well as preparation method and application of heat-conducting interface material

Abstract

The invention relates to an epoxidized vegetable oil carbon-based heat-conducting interface material with adjustable crosslinking density as well as a preparation method and application of the epoxidized vegetable oil carbon-based heat-conducting interface material. The invention relates to a preparation method of an epoxidized vegetable oil carbon-based heat-conducting interface material with adjustable crosslinking density. The preparation method comprises the following steps: preparing epoxidized vegetable oil resin containing conjugated diene and diolefinophilic functional groups by utilizing epoxy groups of epoxidized vegetable oil and curing agents with different functional groups and different molar ratios under the condition of an epoxy accelerator; the epoxidized vegetable oil carbon-based heat-conducting interface material with the adjustable crosslinking density is constructed by taking the graphene nanosheets, the graphite, the carbon nanotubes and the like as cross-linking agents and heat-conducting fillers, the epoxidized vegetable oil carbon-based heat-conducting interface material has excellent heat-conducting property and relatively low thermal resistance, the heat conductivity coefficient of the material can reach 1.42-5.21 W.m <-1 >. K <-1 >, the interface thermal resistance is 0.65-1.52 cm < 2 >. K.W <-1 >, the contact thermal resistance is 0.31-0.46 cm < 2 >. K.W <-1 >, and the heat-conducting property is good. The shore hardness is 29 to 37, and the crosslinking density can be controllably adjusted in a range of 0.19 to 0.81 mmol.cm <-3 >.

Description

Technical Field

[0001] The present invention belongs to the technical field of thermal conductive interface materials, and relates to a controllable cross-linked epoxidized vegetable oil / carbon-based thermal conductive interface material, a preparation method thereof and an application thereof. Background Art

[0002] The thermal management system of a device generally consists of a heat generating component, a heat dissipating device and a thermal conductive interface material. Among them, the main function of the thermal conductive interface material is to ensure effective heat transfer between the heat generating component and the heat dissipating device. Therefore, the thermal conductive interface material is usually a material used to fill the gas voids between solid materials, effectively improving the interfacial heat conduction and optimizing the thermal conduction performance of power devices, which is an effective way to ensure the reliability and safety of the device. It generally consists of a thermal conductive filler and a flexible silicone elastomer or a phase change. The traditional method has the problem of poor interfacial compatibility between the thermal conductive filler and the matrix during the preparation of the thermal conductive interface material, resulting in a high interfacial thermal resistance. In addition, the silicone resin or the phase change material is prone to oil leakage, resulting in a decline in the material performance and a high contact thermal resistance.

[0003] In the prior art, generally, methods such as surface treatment of thermal conductive fillers or construction of a three-dimensional thermal conductive framework are adopted to avoid the leakage of the matrix and at the same time reduce the interfacial thermal resistance inside the material. For example, CN108192577A discloses a thermal conductive filler and a thermal conductive interface material and a preparation method thereof. By using a compound of gas-phase alumina and micron-sized alumina and simultaneously undergoing dopamine modification treatment, the compatibility between the gas-phase alumina, the micron-sized alumina and the matrix material can be improved, the contact thermal resistance becomes smaller, the thermal conductivity increases, and at the same time, the mechanical properties of the thermal conductive interface material are improved, and the construction performance of the thermal conductive interface material is increased. In addition, CN105385417A discloses a three-dimensional graphene / phase change thermal conductive composite material. Using graphene oxide as an emulsifier, it is mixed with a phase change material to form a graphene oxide / phase change material emulsion, and then using the graphene oxide / phase change material emulsion as a template, and then through a hydrothermal reduction reaction, a three-dimensional graphene / phase change thermal conductive composite material is prepared, effectively improving the thermal conductivity and thermal stability of the phase change composite material, and effectively solving the technical problem of easy leakage.

[0004] Although the above technical solutions reduce the system contact thermal resistance and optimize the interfacial thermal resistance inside the material to a certain extent, there are other problems at the same time:

[0005] 1. The means of reducing the contact thermal resistance by improving the surface characteristics of the thermal conductive filler has strong limitations. Usually, to obtain a high thermal conductivity, a large amount of thermal conductive filler needs to be filled, generally more than 50%, which will change other properties of the thermal conductive interface material. For example, a high modulus will increase the contact thermal resistance between the material and the heat source or the radiator. Secondly, the surface treatment of the filler will reduce the intrinsic thermal conductivity of the filler, thereby reducing the overall thermal conductivity of the thermal conductive interface material.

[0006] 2. The methods of surface treatment of fillers or pre - constructing three - dimensional thermal conductive networks only play a certain role in the distribution state and entanglement of fillers, but do not undergo covalent cross - linking with the components in the matrix, and the effect of reducing the interfacial thermal resistance of heterogeneous interfaces is not as good as that of forming covalent bonds (or other non - covalent bonds, such as hydrogen bonds, coordination bonds, etc.).

[0007] 3. The increasing scarcity of fossil energy has also brought severe energy and resource crises. The resin matrices used in traditional thermal conductive interface materials, such as silicone resins and epoxy matrices, have excellent mechanical properties, structural stability, and solvent resistance due to their covalent network structures. However, permanently cross - linked polymers have the characteristics of being insoluble and infusible, which bring major problems to the sustainable polymer economy, and the single cross - linked structure also cannot play a controllable role in regulating the contact thermal resistance. Summary of the Invention

[0008] In view of the above - mentioned technical problems, the present invention provides a method using epoxidized vegetable oil with biodegradability, low toxicity, low volatility, and environmental friendliness as a precursor, grafting conjugated diene and dienophile functional groups onto the molecular chain segments of epoxidized vegetable oil, using carbon materials such as graphene, graphite, and carbon nanotubes as co - cross - linking agents and thermal conductive fillers, constructing dynamic covalent bonds in situ based on Diels–Alder reaction, strengthening the interfacial interaction between the polymer matrix and the thermal conductive filler, optimizing the phonon transport of heterogeneous interfaces, and thus reducing the thermal resistance. In addition, by regulating the stoichiometric ratio of the active groups in the epoxy modifier to the epoxy groups in epoxidized vegetable oil, a cross - linked network structure with different cross - link densities is constructed to achieve controllable adjustment of the mechanical properties of the material. At the same time, the secondary secondary alcohol hydroxyl groups formed after the reaction of epoxy groups provide good adhesion to the surface of the substrate, thereby effectively reducing the contact thermal resistance of the material.

[0009] To achieve the above - mentioned purpose, the present invention is realized by the following means:

[0010] The present invention provides a preparation method of an epoxidized vegetable oil / carbon - based thermal conductive interface material with adjustable cross - link density, including the following steps:

[0011] (1) Place epoxidized vegetable oil, a modifier containing a conjugated diene functional group, and an epoxy curing accelerator in a container, heat and react to obtain an epoxidized vegetable oil resin containing a conjugated diene.

[0012] (2) Place epoxidized vegetable oil, a modifier containing a dienophile functional group, and an epoxy curing accelerator in a container, heat and react to obtain an epoxidized vegetable oil resin containing a dienophile functional group.

[0013] (3) Mix the epoxidized vegetable oil resin containing conjugated diene obtained in step (1) with the epoxidized vegetable oil resin containing dienophile functional groups obtained in step (2), and continue to add carbon materials and mix them together for heating and stirring reaction; the molar ratio of conjugated diene in the epoxidized vegetable oil resin containing conjugated diene to dienophile in the epoxidized vegetable oil resin containing dienophile functional groups is 1:1;

[0014] (4) After the reaction is completed, place it in a preheated mold for curing reaction, and then cool it to room temperature to obtain the product.

[0015] Preferably, the modifier containing conjugated diene functional groups in step (1) is selected from one or more of furfurylamine, 1-(furan-2-yl)-N-methylmethanamine, 5-methyl-2-furoic acid, methyl 2-furoate, and furfuryl mercaptan.

[0016] Preferably, the molar ratio of the epoxy group of the epoxidized vegetable oil to the active group of the modifier containing conjugated diene functional groups in step (1) is 0.5-2:1; the active groups of the modifier containing conjugated diene functional groups are selected from one or more of amino active hydrogen, secondary amino group, carboxyl group, and mercapto group.

[0017] Preferably, the dosage of the epoxy curing accelerator in step (1) is 1-3% of the mass of the epoxidized vegetable oil.

[0018] Preferably, the temperature of the reaction in step (1) is 90-120 °C.

[0019] Preferably, the reaction time in step (1) is 2-8 h.

[0020] Preferably, the epoxy modifier containing dienophile functional groups in step (2) is selected from one or more of 3-maleimidopropionic acid, 4-maleimidopropionic acid, 5-maleimidopentanoic acid, 6-maleimidohexanoic acid, and 11-maleamidoundecanoic acid.

[0021] Preferably, the molar ratio of the epoxy group of the epoxidized vegetable oil to the active group of the modifier containing dienophile functional groups in step (2) is 0.5-1:1; the active group of the modifier containing dienophile functional groups is selected from carboxyl group.

[0022] Preferably, the epoxidized vegetable oil in steps (1) and (2) is selected from one or more of epoxidized soybean oil, epoxidized olive oil, epoxidized rubber seed oil, and epoxidized linseed oil.

[0023] Preferably, the epoxy curing accelerator described in steps (1) and (2) is selected from one or more of 4-dimethylaminopyridine (DMAP), 1-methylimidazole (1-MI), 2,4,6-tris(dimethylaminomethyl)phenol (DMP-30), and triethylamine.

[0024] Preferably, the dosage of the epoxy curing accelerator described in step (2) is 1-3% of the mass of the epoxidized vegetable oil.

[0025] Preferably, the temperature of the reaction described in step (2) is 90-120 °C.

[0026] Preferably, the reaction time described in step (2) is 2-8 h.

[0027] Preferably, the carbon material described in step (3) is selected from one or more of graphene nanosheets, graphite, and carbon nanotubes; more preferably, the carbon material is selected from a mixture composed of graphene nanosheets and carbon nanotubes; most preferably, the carbon material is selected from a mixture composed of graphene nanosheets and carbon nanotubes, and the mass ratio of graphene nanosheets to carbon nanotubes is 3-7:1.

[0028] Preferably, the dosage of the carbon material described in step (3) is 5-35% of the total mass.

[0029] Preferably, the temperature of the heating and stirring reaction described in step (3) is 90-120 °C, and the time is 5-30 min.

[0030] Preferably, the temperature of the preheated mold described in step (4) is 100-150 °C.

[0031] Preferably, the curing reaction described in step (4) is specifically: first, perform the first-stage curing reaction at 95-130 °C for 2-6 h, and then perform the second-stage curing reaction at 140-160 °C for 1-4 h.

[0032] The second aspect of the present invention provides a crosslinking density adjustable epoxidized vegetable oil / carbon-based thermal conductive interface material prepared according to the above preparation method.

[0033] The third aspect of the present invention provides the application of the crosslinking density adjustable epoxidized vegetable oil / carbon-based thermal conductive interface material prepared according to the above preparation method in the heat dissipation of electronic devices.

[0034] Compared with the existing technology, the present invention has the following beneficial effects:

[0035] (1) The present invention uses bio - low - toxicity, environmentally friendly and renewable epoxidized vegetable oil as the matrix precursor, and constructs epoxidized vegetable oil - based resins containing conjugated diene and dienophile functional groups with different types of curing agents respectively. Based on the Diels–Alder reaction, using graphene nanosheets, graphite, carbon nanotubes, etc. as cross - linkers and thermal conductive fillers, a cross - linked density - adjustable epoxidized vegetable oil - carbon - based thermal conductive interface material is constructed, enabling in - situ bonding reactions between the fillers and the matrix, reducing the surface treatment process of the thermal conductive fillers, optimizing the interaction between the resin matrix and the heterogeneous interface of the thermal conductive fillers, and improving the overall thermal conductivity of the material. At the same time, the epoxy groups of epoxidized vegetable oil and curing agents with different functional groups and different molar ratios endow the material with adjustable cross - linked density, realizing the controllability of the mechanical properties and contact thermal resistance of the material, and expanding the application of the biomass resource epoxidized vegetable oil.

[0036] (2) The present invention prepares an epoxidized vegetable oil resin containing conjugated diene and dienophile functional groups with epoxidized vegetable oil and different types of curing agents, and a thermal conductive interface material prepared with graphene nanosheets, graphite, carbon nanotubes as cross - linkers and thermal conductive fillers, which can effectively improve the thermal conductivity and thermal resistance of the thermal conductive interface material. The thermal conductivity of the material can reach 1.42 - 5.21 W·m -1 ·K -1 , the interfacial thermal resistance is 0.65 - 1.52 cm 2 ·K·W -1 , the contact thermal resistance is 0.31 - 0.46 cm 2 ·K·W -1 , and the Shore hardness is 29 - 37. Brief Description of the Drawings

[0037] Figure 1 Digital photos of the thermal conductive interface materials of Comparative Example 1 (left) and Comparative Example 3 (right) of the present invention.

[0038] Figure 2 DSC spectra of conjugated - diene - containing resins with different epoxidized soybean oil / furfurylamine ratios in Example 1 and Example 6 of the present invention.

[0039] Figure 3 Infrared spectra of conjugated - diene - containing resins with different epoxidized soybean oil / furfurylamine ratios in Example 1 and Example 6 of the present invention. Detailed Description of the Embodiments

[0040] To make the objectives, technical solutions and effects of the present invention clearer and more definite, the present invention will be further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0041] Unless otherwise defined, all technical terms used hereinafter have the same meanings as commonly understood by those skilled in the art. The technical terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention. Unless otherwise specifically stated, various raw materials, reagents, instruments, equipment, etc. used in the present invention can be obtained through market purchase or can be prepared by existing methods.

[0042] Example 1

[0043] A crosslinking density adjustable epoxy vegetable oil / carbon-based thermal conductive interface material, and its preparation method specifically includes the following steps:

[0044] (1) Put 6 g of epoxidized soybean oil, 0.79 g of furfurylamine (where the molar ratio of epoxy groups in epoxidized soybean oil to active hydrogen in amino groups in furfurylamine is 1:1), and 0.06 g of 4-dimethylaminopyridine (the addition amount is 1% of the mass fraction of epoxidized soybean oil) into a round-bottom flask, and magnetically stir and react at 120 °C for 2 h to obtain an epoxidized vegetable oil resin containing conjugated dienes.

[0045] (2) Put 6 g of epoxidized soybean oil, 8.32 g of 3-maleimidopropionic acid (where the molar ratio of epoxy groups in epoxidized corn oil to carboxyl groups in 3-maleimidopropionic acid is 0.5:1), and 0.06 g of 4-dimethylaminopyridine (the addition amount is 1% of the mass fraction of epoxidized soybean oil) into a round-bottom flask, and magnetically stir and react at 120 °C for 2 h to obtain an epoxidized vegetable oil resin containing dienophile functional groups.

[0046] (3) Mix the epoxidized vegetable oil resin containing conjugated dienes obtained in step (1) and the epoxidized vegetable oil resin containing dienophile functional groups obtained in step (2) according to the molar ratio of conjugated dienes to dienophiles of 1:1, and further mix them together with graphene nanosheets as thermal conductive fillers and crosslinking agents in a round-bottom flask, and heat and stir and react at 120 °C for 30 min; the dosage of graphene nanosheets is 10% of the total mass.

[0047] (4) After the reaction is completed, place it in a silicone mold preheated to 120 °C, first carry out the first-stage curing reaction at 120 °C for 2 h, then carry out the second-stage curing reaction at 150 °C for 2 h, and then cool to room temperature to obtain a crosslinking density adjustable epoxy vegetable oil / carbon-based thermal conductive interface material.

[0048] Example 2

[0049] A crosslinking density adjustable epoxy vegetable oil / carbon-based thermal conductive interface material, and its preparation method specifically includes the following steps:

[0050] (1) Place 5 g of epoxidized olive oil, 1.44 g of 1-(furan-2-yl)-N-methylmethanamine (where the molar ratio of the epoxy groups in epoxidized soybean oil to the active hydrogen of the amino group in 1-(furan-2-yl)-N-methylmethanamine is 1:1), and 0.025 g of 1-methylimidazole (the addition amount is 0.5% of the mass fraction of epoxidized olive oil) in a round-bottom flask, and magnetically stir and react at 95 °C for 3 h to obtain an epoxidized vegetable oil resin containing conjugated dienes.

[0051] (2) Place 5 g of epoxidized olive oil, 2.20 g of 4-maleimidylpropionic acid (where the molar ratio of the epoxy groups in epoxidized soybean oil to the carboxyl group in 4-maleimidylpropionic acid is 1:1), and 0.025 g of 1-methylimidazole (the addition amount is 0.5% of the mass fraction of epoxidized olive oil) in a round-bottom flask, and magnetically stir and react at 95 °C for 3 h to obtain an epoxidized vegetable oil resin containing dienophile functional groups.

[0052] (3) Mix the epoxidized vegetable oil resin containing conjugated dienes obtained in step (1) and the epoxidized vegetable oil resin containing dienophile functional groups obtained in step (2) according to a molar ratio of conjugated dienes to dienophiles of 1:1, and place them in a round-bottom flask together with graphite as a heat-conducting filler and cross-linking agent for co-mixing, and heat and stir and react at 90 °C for 25 min; the amount of graphite used is 30% of the total mass.

[0053] (4) After the reaction is completed, place it in a silicone mold with a preheating temperature of 110 °C, first carry out the first-stage curing reaction at 110 °C for 3 h, then carry out the second-stage curing reaction at 160 °C for 3 h, and then cool to room temperature to obtain an epoxidized vegetable oil / carbon-based thermally conductive interface material with adjustable crosslinking density.

[0054] Example 3

[0055] An epoxidized vegetable oil / carbon-based thermally conductive interface material with adjustable crosslinking density, and its preparation method specifically includes the following steps:

[0056] (1) Place 7 g of epoxidized olive oil, 4.59 g of 5-methyl-2-furoic acid (where the molar ratio of the epoxy groups in epoxidized olive oil to the carboxyl group in 5-methyl-2-furoic acid is 0.5:1), and 0.053 g of 2,4,6-tris(dimethylaminomethyl)phenol (the addition amount is 0.75% of the mass fraction of epoxidized olive oil) in a round-bottom flask, and magnetically stir and react at 105 °C for 5 h to obtain an epoxidized vegetable oil resin containing conjugated dienes.

[0057] (2) Place 7 g of epoxidized olive oil, 3.59 g of 5-maleimidopentanoic acid (where the molar ratio of the epoxy groups in the epoxidized olive oil to the carboxyl groups in 5-maleimidopentanoic acid is 1:1), and 0.053 g of 2,4,6-tris(dimethylaminomethyl)phenol (the addition amount is 0.75% of the mass fraction of the epoxidized olive oil) in a round-bottom flask, and magnetically stir and react at 105 °C for 5 h to obtain an epoxidized vegetable oil resin containing dienophile functional groups.

[0058] (3) Mix the epoxidized vegetable oil resin containing conjugated dienes obtained in step (1) and the epoxidized vegetable oil resin containing dienophile functional groups obtained in step (2) according to a molar ratio of conjugated dienes to dienophiles of 1:1, and place them in a round-bottom flask together with carbon nanotubes as a thermal conductive filler and cross-linking agent for co-mixing, and heat and stir and react at 100 °C for 15 min; the amount of carbon nanotubes used is 5% of the total mass.

[0059] (4) After the reaction is completed, place it in a silicone mold with a preheating temperature of 120 °C, first carry out the first-stage curing reaction at 120 °C for 4 h, then carry out the second-stage curing reaction at 140 °C for 4 h, and then cool to room temperature to obtain an epoxidized vegetable oil / carbon-based thermal conductive interface material with adjustable crosslinking density.

[0060] Example 4

[0061] An epoxidized vegetable oil / carbon-based thermal conductive interface material with adjustable crosslinking density, and its preparation method specifically includes the following steps:

[0062] (1) Place 4.5 g of epoxidized linseed oil, 3.13 g of furfuryl mercaptan (where the molar ratio of the epoxy groups in the epoxidized sunflower oil to the mercapto groups in furfuryl mercaptan is 1:1), and 0.045 g of triethylamine (the addition amount is 1% of the mass fraction of the epoxidized linseed oil) in a round-bottom flask, and magnetically stir and react at 115 °C for 6 h to obtain an epoxidized vegetable oil resin containing conjugated dienes.

[0063] (2) Place 4.5 g of epoxidized linseed oil, 5.80 g of 6-maleimidohexanoic acid (where the molar ratio of the epoxy groups in the epoxidized sunflower oil to the carboxyl groups in 6-maleimidohexanoic acid is 1:1), and 0.045 g of triethylamine (the addition amount is 1% of the mass fraction of the epoxidized linseed oil) in a round-bottom flask, and magnetically stir and react at 115 °C for 6 h to obtain an epoxidized vegetable oil resin containing dienophile functional groups.

[0064] (3) Mix the epoxy vegetable oil resin containing conjugated dienes obtained in step (1) and the epoxy vegetable oil resin containing dienophile functional groups obtained in step (2) at a molar ratio of conjugated dienes to dienophiles of 1:1, and co-mix them with graphene nanosheets and carbon nanotubes as thermal conductive fillers and crosslinking agents in a round-bottom flask, and heat and stir the reaction at 100 °C for 10 min; wherein the dosage of graphene nanosheets and carbon nanotubes is 15% of the total mass, and the mass ratio of graphene nanosheets to carbon nanotubes is 5:1.

[0065] (4) After the reaction is completed, place it in a silicone mold preheated to 95 °C, first carry out the first-stage curing reaction at 95 °C for 4 h, then carry out the second-stage curing reaction at 150 °C for 4 h, and then cool to room temperature to obtain an epoxy vegetable oil / carbon-based thermal conductive interface material with adjustable crosslinking density.

[0066] Example 5

[0067] An epoxy vegetable oil / carbon-based thermal conductive interface material with adjustable crosslinking density, and its preparation method specifically includes the following steps:

[0068] (1) Place 9 g of epoxy linseed oil, 3.05 g of 1-(furan-2-yl)-N-methylmethanamine (wherein the molar ratio of epoxy groups in epoxy linseed oil to secondary amino groups in 1-(furan-2-yl)-N-methylmethanamine is 2:1), and 0.18 g of 4-dimethylaminopyridine (the addition amount is 2% of the mass fraction of epoxy linseed oil) in a round-bottom flask, and magnetically stir and react at 90 °C for 8 h to obtain an epoxy vegetable oil resin containing conjugated dienes.

[0069] (2) Place 9 g of epoxy linseed, 15.45 g of 11-maleamidoundecanoic acid (wherein the molar ratio of epoxy groups in epoxy linseed oil to carboxyl groups in 11-maleamidoundecanoic acid is 1:1), and 0.18 g of 4-dimethylaminopyridine (the addition amount is 2% of the mass fraction of epoxy linseed oil) in a round-bottom flask, and magnetically stir and react at 90 °C for 8 h to obtain an epoxy vegetable oil resin containing dienophile functional groups.

[0070] (3) Mix the epoxy vegetable oil resin containing conjugated dienes obtained in step (1) and the epoxy vegetable oil resin containing dienophile functional groups obtained in step (2) at a molar ratio of conjugated dienes to dienophiles of 1:1, and co-mix them with graphene nanosheets and carbon nanotubes as thermal conductive fillers and crosslinking agents in a round-bottom flask, and heat and stir the reaction at 100 °C for 25 min; wherein the dosage of graphene nanosheets and carbon nanotubes is 20% of the total mass, and the mass ratio of graphene nanosheets to carbon nanotubes is 7:1.

[0071] (4) After the reaction is completed, it is placed in a silicone mold preheated to 120 °C. First, the first-stage curing reaction is carried out at 120 °C for 6 h, then the second-stage curing reaction is carried out at 150 °C for 1 h, and then it is cooled to room temperature to obtain an epoxidized vegetable oil / carbon-based thermal conductive interface material with adjustable crosslinking density.

[0072] Example 6

[0073] An epoxidized vegetable oil / carbon-based thermal conductive interface material with adjustable crosslinking density, and its preparation method specifically includes the following steps:

[0074] (1) 3.5 g of epoxidized rubber seed oil, 1.09 g of furfurylamine (the molar ratio of epoxy groups in epoxidized soybean oil to active hydrogen in amine groups of furfurylamine is 0.5:1), and 0.061 g of 1-methylimidazole (the addition amount is 2% of the mass fraction of epoxidized rubber seed oil) are placed in a round-bottom flask, and a magnetic stirring reaction is carried out at 100 °C for 6 h to obtain an epoxidized vegetable oil resin containing conjugated dienes.

[0075] (2) 3.5 g of epoxidized rubber seed oil, 1.18 g of 6-maleimidocaproic acid (the molar ratio of epoxy groups in epoxidized soybean oil to carboxyl groups in 6-maleimidocaproic acid is 0.5:1), and 0.061 g of 1-methylimidazole (the addition amount is 2% of the mass fraction of epoxidized rubber seed oil) are placed in a round-bottom flask, and a magnetic stirring reaction is carried out at 100 °C for 6 min to obtain an epoxidized vegetable oil resin containing dienophile functional groups.

[0076] (3) The epoxidized vegetable oil resin containing conjugated dienes obtained in step (1) and the epoxidized vegetable oil resin containing dienophile functional groups obtained in step (2) are mixed according to the molar ratio of conjugated dienes to dienophiles of 1:1, and are placed in a round-bottom flask together with graphene nanosheets and carbon nanotubes as thermal conductive fillers and crosslinking agents for co-mixing, and a heating and stirring reaction is carried out at 105 °C for 5 min; the dosage of graphene nanosheets and carbon nanotubes is 35% of the total mass, and the mass ratio of graphene nanosheets to carbon nanotubes is 3:1.

[0077] (4) After the reaction is completed, it is placed in a silicone mold preheated to 130 °C. First, the first-stage curing reaction is carried out at 130 °C for 6 h, then the second-stage curing reaction is carried out at 150 °C for 1 h, and then it is cooled to room temperature to obtain an epoxidized vegetable oil / carbon-based thermal conductive interface material with adjustable crosslinking density.

[0078] Comparative Example 1

[0079] An epoxidized vegetable oil / carbon-based thermal conductive interface material, and its preparation method specifically includes the following steps:

[0080] (1) Place 6 g of epoxidized soybean oil, 2.39 g of furfurylamine (where the molar ratio of epoxy groups in epoxidized soybean oil to active hydrogen of amino groups in furfurylamine is 0.5:1), and 0.06 g of 1-methylimidazole (the addition amount is 1% of the mass fraction of epoxidized soybean oil) into a round-bottom flask, and carry out a magnetic stirring reaction at 105 °C for 2 h to obtain a vegetable oil resin.

[0081] (2) Place the vegetable oil resin obtained in step (1) and graphene nanosheets as a thermal conductive filler and cross-linking agent into a round-bottom flask and mix them together, and carry out a heating and stirring reaction at 105 °C for 15 min; the dosage of graphene nanosheets is 5% of the total mass.

[0082] (3) After the reaction is completed, place it in a silicone mold with a preheating temperature of 120 °C, first carry out the first-stage curing reaction at 120 °C for 3 h, then carry out the second-stage curing reaction at 150 °C for 3 h, and then cool to room temperature to obtain the epoxidized vegetable oil / carbon-based thermal conductive interface material.

[0083] Comparative Example 2

[0084] A preparation method of an epoxidized vegetable oil / carbon-based thermal conductive interface material specifically includes the following steps:

[0085] (1) Place 6 g of epoxidized soybean oil, 0.79 g of furfurylamine (where the molar ratio of epoxy groups in epoxidized soybean oil to active hydrogen of amino groups in furfurylamine is 1:1), and 0.06 g of 1-methylimidazole (the addition amount is 1% of the mass fraction of epoxidized soybean oil) into a round-bottom flask, and carry out a magnetic stirring reaction at 105 °C for 2 h to obtain a vegetable oil resin.

[0086] (2) Place the vegetable oil resin obtained in step (1) and graphene nanosheets as a thermal conductive filler and cross-linking agent into a round-bottom flask and mix them together, and carry out a heating and stirring reaction at 105 °C for 15 min; the dosage of graphene nanosheets is 5% of the total mass.

[0087] (3) After the reaction is completed, place it in a silicone mold with a preheating temperature of 120 °C, first carry out the first-stage curing reaction at 120 °C for 3 h, then carry out the second-stage curing reaction at 150 °C for 3 h, and then cool to room temperature to obtain the epoxidized vegetable oil / carbon-based thermal conductive interface material.

[0088] Comparative Example 3

[0089] A preparation method of an epoxidized vegetable oil / carbon-based thermal conductive interface material specifically includes the following steps:

[0090] (1) Place 7 g of epoxidized olive oil, 3.59 g of 5-maleimidopentanoic acid (where the molar ratio of epoxy groups in epoxidized olive oil to carboxyl groups in 5-maleimidopentanoic acid is 1:1), and 0.053 g of 2,4,6-tris(dimethylaminomethyl)phenol (the addition amount is 0.75% of the mass fraction of epoxidized olive oil) in a round-bottom flask, and magnetically stir and react at 105 °C for 5 h to obtain a vegetable oil resin.

[0091] (2) Place the vegetable oil resin obtained in step (1) and a mixture of graphene nanosheets and carbon nanotubes as thermal conductive fillers and cross-linking agents in a round-bottom flask and mix them together. Heat and stir at 105 °C for 15 min; the amount of graphene nanosheets and carbon nanotubes used is 10% of the total mass (the mass ratio of graphene to carbon nanotubes is 3:1).

[0092] (3) After the reaction, place it in a silicone mold preheated to 120 °C. First, carry out the first-stage curing reaction at 120 °C for 3 h, then carry out the second-stage curing reaction at 150 °C for 3 h, and then cool to room temperature to obtain an epoxidized vegetable oil / carbon-based thermal conductive interface material.

[0093] Comparative Example 4

[0094] (1) Place 5 g of epoxidized soybean oil, 4.06 g of 4,4'-diaminodiphenylmethane (where the molar ratio of epoxy groups in epoxidized soybean oil to amine active hydrogens in 4,4'-diaminodiphenylmethane is 0.5:1), and 0.038 g of 4-dimethylaminopyridine (the addition amount is 0.75% of the mass fraction of epoxidized soybean oil) in a round-bottom flask, and magnetically stir and react at 105 °C for 4 h to obtain a vegetable oil resin.

[0095] (2) Place the vegetable oil resin obtained in step (1) and a mixture of graphene nanosheets and carbon nanotubes as thermal conductive fillers and cross-linking agents in a round-bottom flask and mix them together. Heat and stir at 105 °C for 15 min; the amount of graphene nanosheets and carbon nanotubes used is 15% of the total mass (the mass ratio of graphene to carbon nanotubes is 5:1).

[0096] (3) After the reaction, place it in a silicone mold preheated to 120 °C. First, carry out the first-stage curing reaction at 120 °C for 3 h, then carry out the second-stage curing reaction at 150 °C for 3 h, and then cool to room temperature to obtain an epoxidized vegetable oil / carbon-based thermal conductive interface material.

[0097] Verification Example 1

[0098] Take the thermal conductive interface materials prepared in Examples 1-6 and Comparative Examples 1-4 and observe their physical and chemical forms. Among them, Comparative Examples 1 and 3 cannot be cured and are in a liquid or paste state before and after the reaction (see Figure 1), which does not meet the morphological requirements of the solid thermal conductive interface material to be prepared in the present invention, so subsequent performance tests are no longer carried out. In Comparative Example 2, the amounts of epoxidized soybean oil and furfurylamine were adjusted, but the obtained thermal conductive interface material was still in a semi-fluid state and could not be cured, and a crosslinked network could not be formed; that is, simply adjusting the amounts of epoxidized vegetable oil and the modifier containing conjugated diene functional groups could not form a crosslinked network nor adjust the crosslinking density. Subsequently, the thermal conductive interface materials prepared in Examples 1-6 and Comparative Example 4 were respectively tested for their thermal conductivity (W·m -1 ·K -1 ), interface thermal resistance (cm 2 ·K·W -1 ), and contact thermal resistance (cm 2 ·K·W -1 ) according to the ASTM D5470 standard. At the same time, the crosslinking density (mmol·cm -3 ) and Shore hardness physical and chemical properties were characterized. The test results are shown in Table 1 below.

[0099] Table 1 Detection Results of Physical and Chemical Properties of Thermal Conductive Composites in Examples 1-6 and Comparative Example 4

[0100]

[0101] Further analysis of Example 1 and Example 6 found that different ratios of epoxy groups and active groups of the modifier can react, which can be proved by DSC and infrared results, and different ratios of epoxy curing accelerators can effectively reduce the reaction temperature of the system (see Figures 2-3 ). In Comparative Example 4, the epoxidized vegetable oil resin matrix does not contain conjugated diene and dienophile functional groups, and only has physical contact with the thermal conductive filler, and cannot form covalent bonding with carbon materials such as graphene, graphite, and carbon nanotubes. The interface interaction between the resin matrix and the filler is weak, and the crosslinked structure is single. Therefore, the thermal conductivity of this material is only 0.77 W·m -1 ·K -1 , the interface thermal resistance is 1.76 cm 2 ·K·W -1 , the contact thermal resistance is 0.69 cm 2 ·K·W -1 , the Shore hardness is as high as 57, and the crosslinking density cannot be regulated, which is 0.73 mmol·cm -3In contrast, the thermal interface material prepared according to the embodiments of the present invention not only introduces groups that can react with graphene or carbon nanotubes, improves the compatibility between graphene, carbon nanotubes or a mixture of the two and the resin, effectively reduces the interfacial thermal resistance of the material, and significantly improves the thermal conductivity. In addition, by regulating the dosage ratio of the active groups in the epoxy groups and the active amino groups of the substance containing conjugated diene and dienophile functional groups, the crosslinking density of the material can be effectively regulated, and then the Shore hardness of the material can be adjusted. By regulating the hardness of the material, more contact areas for heat transfer can be given, enabling the effective transfer of heat flow from the contact interface, thereby greatly reducing the contact thermal resistance of the material.

[0102] The above specific embodiments have specifically introduced the analysis method involved in the present invention. It should be noted that the above introduction is only to help those skilled in the art better understand the method and idea of the present invention, rather than a limitation on the relevant content. Without departing from the principle of the present invention, those skilled in the art can also make appropriate adjustments or modifications to the present invention, and such adjustments and modifications should also fall within the protection scope of the present invention.

Claims

1. A preparation method of an epoxidized vegetable oil / carbon-based thermal conductive interface material with adjustable crosslinking density, characterized in that, It includes the following steps: (1) Place epoxidized vegetable oil, a modifier containing a conjugated diene functional group, and an epoxy curing accelerator in a container, heat them for reaction to obtain an epoxidized vegetable oil resin containing a conjugated diene. (2) Place epoxidized vegetable oil, a modifier containing a dienophile functional group, and an epoxy curing accelerator in a container, heat them for reaction to obtain an epoxidized vegetable oil resin containing a dienophile functional group. (3) Mix the epoxidized vegetable oil resin containing a conjugated diene obtained in step (1) and the epoxidized vegetable oil resin containing a dienophile functional group obtained in step (2), and continue to add a carbon material and mix them together for heating and stirring reaction; the molar ratio of the conjugated diene in the epoxidized vegetable oil resin containing a conjugated diene to the dienophile in the epoxidized vegetable oil resin containing a dienophile functional group is 1:

1. (4) After the reaction is completed, place it in a preheated mold for curing reaction, and then cool it to room temperature to obtain the product.

2. The preparation method according to claim 1, characterized in that, In step (1), the modifier containing a conjugated diene functional group is selected from one or more of furfurylamine, 1-(furan-2-yl)-N-methylmethanamine, 5-methyl-2-furoic acid, methyl 2-furoate, and furfuryl mercaptan.

3. The preparation method according to claim 1, characterized in that, In step (1), the molar ratio of the epoxy group of the epoxidized vegetable oil to the active group of the modifier containing a conjugated diene functional group is 0.5-2:1; the active group of the modifier containing a conjugated diene functional group is selected from one or more of amino active hydrogen, secondary amino group, carboxyl group, and mercapto group.

4. The preparation method according to claim 1, characterized in that, In step (2), the modifier containing a dienophile functional group is selected from one or more of 3-maleimidopropionic acid, 4-maleimidopropionic acid, 5-maleimidopentanoic acid, 6-maleimidohexanoic acid, and 11-maleamidoundecanoic acid.

5. The preparation method according to claim 1, wherein In step (2), the molar ratio of the epoxy group of the epoxidized vegetable oil to the active group of the modifier containing a dienophile functional group is 0.5-1:1; the active group of the modifier containing a dienophile functional group is selected from carboxyl group.

6. The preparation method according to claim 1, characterized in that, In steps (1) and (2), the epoxy curing accelerator is selected from one or more of 4-dimethylaminopyridine, 1-methylimidazole, 2,4,6-tris(dimethylaminomethyl)phenol, and triethylamine.

7. The preparation method according to claim 1, wherein In steps (1) and (2), the epoxidized vegetable oil is selected from one or more of epoxidized soybean oil, epoxidized corn oil, epoxidized olive oil, epoxidized sunflower oil, and epoxidized linseed oil.

8. The preparation method according to claim 1, wherein, In step (4), the curing reaction specifically is: first carry out the first-stage curing reaction at 95-130°C for 2-6 h, and then carry out the second-stage curing reaction at 140-160°C for 1-4 h.

9. A crosslinking density adjustable epoxidized vegetable oil / carbon-based thermal conductive interface material prepared by the preparation method according to any one of claims 1-8.

10. Application of a crosslinking density adjustable epoxidized vegetable oil / carbon-based thermal conductive interface material prepared by the preparation method according to any one of claims 1-8 in heat dissipation of electronic devices.

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