Preparation method of heat-conducting ethylene-propylene-diene monomer rubber based on interface crosslinking vertical penetrating network

Abstract

The invention discloses a preparation method of a heat-conducting ethylene-propylene-diene monomer rubber based on an interface crosslinking vertical penetrating network, which comprises the following steps: firstly, performing high-temperature decomposition on sodium bicarbonate (NaHCO3) to generate CO2 gas to pre-expand hexagonal boron nitride (h-BN); then sea squirt cellulose nanocrystals (TCNCs) prepared through a sulfuric acid hydrolysis method are used for assisting intercalation stripping, hydroxylated boron nitride nanosheets (BNNS-OH) are prepared through high-temperature sodium hydroxide (NaOH) treatment, liquid metal is nanocrystallized through an ultrasonic technology by means of the metal-hydroxyl coordination effect, and the BNNS-OH / liquid metal heat conduction filler is prepared. Liquid metal is uniformly programmed on the surface of a BNNS-OH sheet layer to play a role of a heat conduction bridge, and further vacuum filtration is carried out under the assistance of TCNCs to prepare the boron nitride heat conduction film. An epoxy group is grafted on an ethylene propylene diene monomer (EPDM) molecular chain through in-situ epoxidation, and on the basis of the idea of modular management of heat conduction and mechanical properties, covalent reaction of hydroxyl and the epoxy group and non-covalent bridging effect of liquid metal and the epoxy group are utilized; the EPDM heat-conducting composite material with a vertical penetrating orientation network is prepared by spreading and laminating a heat-conducting film and epoxidized EPDM and performing interface cross-linking hot pressing, so that the contact area of boron nitride and an EPDM matrix is effectively increased, the interface thermal resistance is reduced, and a high-speed channel is provided for phonon transmission. The preparation method is efficient, simple, convenient, adjustable in mechanical property and heat-conducting property and capable of being used in the field of electronic device heat management.

Description

Technical Field

[0001] The invention relates to a method for preparing a heat-conducting EPDM rubber based on an interface cross-linked vertically penetrating network, and belongs to the field of rubber material preparation. Background Art

[0002] With the development of artificial intelligence and chip industries, electronic components are constantly developing in the direction of miniaturization, high speed and high integration. The resulting "thermal barrier" problem is becoming increasingly severe, seriously affecting the stability, reliability and service life of electronic equipment. As one of the key basic materials in the field of thermal control management, thermally conductive polymer materials are used to connect electronic components and external systems to establish effective heat transfer channels, which is crucial to solving the problem of heat dissipation. However, due to the characteristics of random entanglement, high molecular weight and polydispersity of polymer macromolecular chain ends, their thermal conductivity is low, which makes it difficult to meet the needs of efficient heat dissipation of electronic devices. Based on this, the study and preparation of high-performance polymer thermal conductive materials is of great significance for thermal control management.

[0003] Ethylene propylene diene monomer (EPDM) is a terpolymer formed by random copolymerization of ethylene, propylene and a small amount of non-conjugated dienes under Ziegler-Natta catalyst or metallocene catalytic system. It has unique high flexibility, resilience and chemical stability, and can be used as a candidate material for thermal management. However, its amorphous aggregate structure leads to low intrinsic thermal conductivity (~ 0.2 W / mK), which mainly relies on phonon heat conduction and cannot meet the application performance requirements in the field of heat dissipation of electronic equipment. Yu Pinxuan et al., Insulation Materials, 2021, 54(6):26-31, by filling EPDM rubber with multi-scale alumina / nano zinc oxide composites, when the alumina / zinc oxide filling amount is 200 parts, the thermal conductivity of the composite material reaches 1.16 W / mK; Lu Shaowei et al., Applied Physics A, 2020, 126, 513, by using solution blending method to disperse MXene in EPDM matrix to prepare MXene / EPDM composites, when its content is 6 parts, the in-plane thermal conductivity of the composite material reaches 1.57 W / mK; Chinese patent CN202311812398.4 discloses a method for preparing a thermally reversible cross-linked thermally conductive EPDM rubber composite material, wherein maleic anhydride EPDM rubber is imidized with 2-furanmethylamine, 3-(trimethoxysilyl)propyl methacrylate is grafted on the surface of boron nitride to obtain silylated boron nitride, and a vertically oriented thermally conductive composite material is prepared by solution mixing and stacking hot pressing; Chinese patent CN202410497378.0 discloses a carboxylated boron nitride microsphere composite with high thermal conductivity reinforced EPDM rubber and a preparation method thereof, wherein boron nitride is assembled into boron nitride microspheres, carboxylated boron nitride microspheres are prepared by coating with a dicarboxylic acid compound, and the microspheres are blended with epoxidized EPDM rubber to prepare a thermally conductive EPDM rubber composite material. Low-load thermally conductive fillers made with traditional preparation methods are difficult to form continuous thermal conductive pathways, high-load fillers will sacrifice flexibility and processing performance, and the introduction of more interfaces will increase interfacial thermal resistance. Research on the thermal conductivity of interfacial cross-linking between thermally conductive fillers and the matrix is ​​still very limited.

[0004] Hexagonal boron nitride (h-BN) has excellent thermal conductivity and insulation properties and can be used as an ideal thermal conductive filler for thermal interface materials. However, h-BN is difficult to peel off and disperse in a polymer matrix, so it is necessary to peel it off to prepare boron nitride nanosheets (BNNS) to improve thermal conductivity. Liquid metal (LM) has low interfacial thermal resistance and can be used as a buffer layer between the thermal conductive filler and the rubber matrix to effectively transfer stress. There have been no reports on the preparation of hybrid thermal conductive fillers by assembling boron nitride and liquid metal, while reacting with rubber at the interface, reducing the interfacial thermal resistance, and achieving vertical penetration of the thermal conductive filler through the network. Summary of the invention

[0005] The purpose of the present invention is to provide a preparation method of thermally conductive EPDM rubber based on interface cross-linked vertically penetrating network in view of the deficiencies of the prior art. The method is characterized in that firstly, hexagonal boron nitride (h-BN) is pre-expanded by CO2 gas produced by high-temperature decomposition of sodium bicarbonate (NaHCO3), and then hydroxylated boron nitride nanosheets (BNNS-OH) are prepared by intercalation exfoliation assisted by self-made sea squirt cellulose nanocrystals (TCNCs) in the laboratory and high-temperature sodium hydroxide (NaOH) strong alkali treatment. Through the coordination of metal-hydroxyl, liquid metal is evenly programmed on the surface of BNNS-OH sheet to play the role of "thermal conductive bridge", thereby realizing the nano-crystalization of liquid metal and preparing BNNS-OH. H / liquid metal thermal conductive filler, boron nitride thermal conductive film was prepared by vacuum filtration with the assistance of TCNCs; epoxy groups were grafted on the ethylene propylene diene monomer (EPDM) molecular chain through in-situ epoxidation reaction. Based on the idea of ​​modular management of thermal conductivity and mechanical properties, the covalent reaction of hydroxyl and epoxy groups and the non-covalent bridging effect of liquid metal and epoxy groups were utilized. Boron nitride thermal conductive film and epoxidized EPDM were spread and stacked, and the interface was cross-linked and hot-pressed to prepare EPDM thermal conductive composite materials with a vertical through-oriented network, which effectively increased the contact area between boron nitride and EPDM matrix, reduced the interface thermal resistance, provided a high-speed channel for phonon transmission, and effectively improved the thermal conductivity of EPDM.

[0006] The object of the present invention is achieved by the following technical scheme, wherein the raw material fractions are all mass fractions unless otherwise specified.

[0007] A method for preparing a thermally conductive EPDM rubber based on an interface cross-linked vertically penetrating network, characterized in that the main raw material of the rubber is composed of the following components, calculated by mass fraction: EPDM 100 parts Liquid metal (LM) 0.3-3 parts Hexagonal Boron Nitride (h-BN) 7-12 parts Tuna nanocellulose (TCNCs) 2-5 parts Wherein, the liquid metal (LM) is a gallium indium tin alloy Ga 68.5 -In 21.5 -Sn 10 ; The plane size of the hexagonal boron nitride (h-BN) is 20 μm; The sea squirt nanocellulose (TCNCs) is prepared in the laboratory by hydrolyzing sea squirt with sulfuric acid. The specific preparation method is as follows: 50 parts of ascidian tunicates were cut into pieces, ultrasonically deproteinized, decolorized and impurity-removed in acetone solvent, and then reacted with 150 mL of 62% concentrated sulfuric acid at 50°C for 1.5 h. After that, 100 mL of distilled water was added to terminate the reaction. Finally, the mixture was centrifuged, the supernatant was removed, washed and dialyzed for 5 days, and dried in a vacuum oven at 50°C to obtain ascidian cellulose nanocrystals (TCNCs).

[0008] The preparation method of the thermally conductive EPDM rubber having a vertically penetrating network comprises the following steps: S1: Preparation of Hydroxyboron Nitride Thermally Conductive Film 7-12 parts of hexagonal boron nitride (h-BN) were ultrasonically dispersed in 200-350 parts of deionized water, 2-8 parts of sodium bicarbonate (NaHCO3) were added and stirred to completely dissolve, and the mixture was stirred and reacted in an oil bath at 100-200°C for 2-6 hours. NaHCO3 was decomposed to produce CO2 gas to pre-expand h-BN. After the reaction, 2-5 parts of tunicate cellulose nanocrystals (TCNCs) were added and ultrasonically dispersed for 1 hour. The TCNCs with a large aspect ratio were used for auxiliary intercalation and exfoliation, and the mixture was filtered and washed with deionized water. The obtained product was then ultrasonically dispersed in a 3-6 mol / L sodium hydroxide (NaOH) solution, and the mixture was sealed and stirred for 6 hours in an oil bath at 120°C, filtered and washed with deionized water to obtain hydroxylated boron nitride nanosheets (BNNS-OH).

[0009] The BNNS-OH prepared above was re-dispersed in deionized water with a concentration of 1wt%, and 0.3-3 parts of liquid metal (LM) were added for ultrasonic dispersion for 0.5 h. The liquid metal was evenly programmed on the surface of the BNNS-OH layer to act as a "thermal bridge" by utilizing the coordination effect of metal-hydroxyl. After vacuum filtration and vacuum drying at 40°C, a hydroxyl boron nitride thermal conductive film with a thickness of 0.5 mm was obtained.

[0010] S2: Preparation of high thermal conductivity EPDM rubber Dissolve 100 parts of EPDM in xylene to prepare a 4% EPDM solution, add 0.2-1 parts of epoxy diacetate, stir for 1 min, then add 5-8 parts of formic acid, stir at 55°C for 5 min, then add 8-15 parts of hydrogen peroxide dropwise to form a uniform and stable emulsion system. After continuing the reaction for 6 hours, the product is precipitated in ethanol, soaked in distilled water for 2 days, vacuum dried at 50°C for 6 hours, and transferred to an open mill to be pressed into an epoxidized EPDM rubber film with a thickness of 2 mm.

[0011] Based on the idea of ​​modular management of thermal conductivity and mechanical properties, hydroxyl boron nitride thermal conductive film and epoxidized EPDM rubber film are spread and cross-layered in a mold. The boron nitride thermal conductive film is controlled to be 4 layers and hot pressed at 120-150℃ and 5-15 MPa for 3-12 min. The covalent reaction of hydroxyl and epoxy groups and the non-covalent effect of liquid metal and epoxy groups are used to achieve interfacial cross-linking. The vertical penetration orientation of the boron nitride thermal conductive film in the EPDM matrix is ​​obtained by inverting and flipping, thereby preparing a high thermal conductivity EPDM rubber material.

[0012] The present invention has the following advantages: The interface structure is designed from a molecular perspective to reduce the thermal resistance of the interface between the matrix and the thermally conductive filler to strengthen the heat conduction path, and further modulate the thermally conductive filler network to form an effective long-range heat conduction path. High-quality hydroxyl boron nitride nanosheets were prepared by sodium bicarbonate (NaHCO3) decomposition pre-expansion and sea squirt cellulose nanocrystals (TCNCs) intercalation and exfoliation technology. Through the coordination of metal-hydroxyl groups, liquid metal was evenly programmed on the surface of BNNS-OH sheets to act as a "thermal bridge" to prepare BNNS-OH / liquid metal thermal conductive fillers, and boron nitride thermal conductive films were prepared with the assistance of TCNCs. Based on the idea of ​​modular management of thermal conductivity and mechanical properties, the covalent reaction of hydroxyl groups and epoxy groups and the non-covalent bridging effect of liquid metal and epoxy groups were utilized. Boron nitride thermal conductive films and epoxidized EPDM were spread and stacked, and interface cross-linked hot pressing was used to prepare EPDM thermal conductive composite materials with vertical through-oriented networks, to construct continuous long-range thermal conductive pathways, solve the problem of low-load thermal conductive fillers forming continuous thermal conductive paths, and achieve a balance between high thermal conductivity and high compliance performance through interface cross-linking energy dissipation and stress transfer effects. The invention has a simple preparation process, significantly improved thermal conductivity, and has certain advantages in the field of heat dissipation of electronic devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 Schematic diagram of the reaction process for exfoliating hydroxyboron nitride nanosheets.

[0014] Figure 2 Schematic diagram of the preparation of thermally conductive EPDM rubber with interfacial cross-linking and vertical penetration network. DETAILED DESCRIPTION

[0015] The present invention is further described below through specific examples. It should be noted that the examples are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Those skilled in the art in this field can make non-essential improvements and adjustments to the present invention based on the contents of the present invention described above. Example

[0016] 7 parts of hexagonal boron nitride (h-BN) were ultrasonically dispersed in 200 parts of deionized water, and 2 parts of sodium bicarbonate (NaHCO3) were added and stirred to completely dissolve. The mixture was stirred and reacted in an oil bath at 110°C for 2 h. NaHCO3 was decomposed to produce CO2 gas to pre-expand h-BN. After the reaction, 2 parts of tunicate cellulose nanocrystals (TCNCs) were added and ultrasonically dispersed for 1 h. The mixture was filtered and washed with deionized water. The obtained product was then ultrasonically dispersed in a 3 mol / L sodium hydroxide (NaOH) solution, sealed and stirred for reaction in an oil bath at 120°C for 6 h, filtered and washed with deionized water to obtain hydroxylated boron nitride nanosheets (BNNS-OH). The BNNS-OH prepared above was re-dispersed in deionized water with a concentration of 1wt%, and 0.3 parts of liquid metal (LM) was added for ultrasonic dispersion for 0.5 h. The liquid metal was evenly programmed on the surface of the BNNS-OH layer to act as a "thermal bridge". After vacuum filtration and vacuum drying at 40°C, a 0.5 mm thick hydroxyboron nitride thermal conductive film was obtained.

[0017] 100 parts of EPDM were dissolved in xylene to prepare a 4% EPDM solution, 0.2 parts of epoxy diacetate were added, stirred for 1 min, then 5 parts of formic acid were added, stirred at 55°C for 5 min, and then 10 parts of hydrogen peroxide were added dropwise to form a uniform and stable emulsion system. After continuing the reaction for 6 hours, the product was precipitated in ethanol, soaked in distilled water for 2 days, vacuum dried at 50°C for 6 hours, and transferred to an open mill to be pressed into an epoxidized EPDM rubber film with a thickness of 2 mm.

[0018] Based on the idea of ​​modular management of thermal conductivity and mechanical properties, hydroxyl boron nitride thermal conductive film and epoxidized EPDM rubber film were spread and cross-layered in the mold, and the boron nitride thermal conductive film was controlled to be 4 layers. It was hot pressed at 120℃ and 5 MPa for 4 minutes to achieve interfacial cross-linking, and the vertical penetration orientation of the boron nitride thermal conductive film in the EPDM matrix was obtained by inverting and flipping, and a high thermal conductivity EPDM rubber material was prepared. After testing, the tensile strength of the EPDM composite rubber was 1.14 MPa, the elongation at break was 238%, the Young's modulus was 586 kPa, and the thermal conductivity was 1.471 W / mK. Example

[0019] 8 parts of hexagonal boron nitride (h-BN) were ultrasonically dispersed in 250 parts of deionized water, 3 parts of sodium bicarbonate (NaHCO3) were added and stirred to completely dissolve, and the mixture was stirred and reacted in an oil bath at 130°C for 3 h. NaHCO3 was decomposed to produce CO2 gas to pre-expand h-BN. After the reaction, 2 parts of tunicate cellulose nanocrystals (TCNCs) were added and ultrasonically dispersed for 1 h, filtered and washed with deionized water; the obtained product was then ultrasonically dispersed in 4 mol / L sodium hydroxide (NaOH) solution, sealed and stirred for reaction in an oil bath at 120°C for 6 h, filtered and washed with deionized water to obtain hydroxylated boron nitride nanosheets (BNNS-OH). The BNNS-OH prepared above was re-dispersed in deionized water with a concentration of 1wt%, and 0.5 parts of liquid metal (LM) was added for ultrasonic dispersion for 0.5 h. The liquid metal was evenly programmed on the surface of the BNNS-OH layer to act as a "thermal bridge". Vacuum filtration and vacuum drying at 40°C obtained a hydroxyboron nitride thermal conductive film with a thickness of 0.5 mm.

[0020] 100 parts of EPDM were dissolved in xylene to prepare a 4% EPDM solution, 0.5 parts of epoxy diacetate were added, stirred for 1 min, then 6 parts of formic acid were added, stirred at 55°C for 5 min, and then 10 parts of hydrogen peroxide were added dropwise to form a uniform and stable emulsion system. After continuing the reaction for 6 hours, the product was precipitated in ethanol, soaked in distilled water for 2 days, vacuum dried at 50°C for 6 hours, and transferred to an open mill to be pressed into an epoxidized EPDM rubber film with a thickness of 2 mm.

[0021] Based on the idea of ​​modular management of thermal conductivity and mechanical properties, the hydroxyl boron nitride thermal conductive film and the epoxidized EPDM rubber film were spread and cross-layered in the mold, and hot pressed at 130℃ and 5 MPa for 5 min to achieve interfacial cross-linking, and inverted to obtain the vertical penetration orientation of the boron nitride thermal conductive film in the EPDM matrix, and a high thermal conductivity EPDM rubber material was prepared. After testing, the tensile strength of the EPDM composite rubber was 1.02 MPa, the elongation at break was 277%, the Young's modulus was 516 kPa, and the thermal conductivity was 1.825 W / mK. Example

[0022] 10 parts of hexagonal boron nitride (h-BN) were ultrasonically dispersed in 300 parts of deionized water, 6 parts of sodium bicarbonate (NaHCO3) were added and stirred to completely dissolve, and stirred in an oil bath at 150℃ for 5 hours. NaHCO3 decomposed to produce CO2 gas to pre-expand h-BN. After the reaction, 4 parts of sea squirt cellulose nanocrystals (TCNCs) were added and ultrasonically dispersed for 1 hour, filtered and washed with deionized water; then the obtained product was ultrasonically dispersed in 5 mol / L sodium hydroxide (NaOH) solution, sealed and stirred in an oil bath at 120℃ for 6 hours, filtered and washed with deionized water to obtain hydroxylated boron nitride nanosheets (BNNS-OH). The BNNS-OH prepared above was re-dispersed in deionized water with a concentration of 1wt%, and 1 part of liquid metal (LM) was added and ultrasonically dispersed for 0.5 hours. The liquid metal was evenly programmed on the surface of the BNNS-OH sheet to act as a "thermal bridge", vacuum filtered and vacuum dried at 40℃ to obtain a hydroxyl boron nitride thermal conductive film with a thickness of 0.5mm.

[0023] 100 parts of EPDM were dissolved in xylene to prepare a 4% EPDM solution, 0.6 parts of epoxy diacetate were added, stirred for 1 min, then 6 parts of formic acid were added, stirred at 55°C for 5 min, and then 12 parts of hydrogen peroxide were added dropwise to form a uniform and stable emulsion system. After continuing the reaction for 6 hours, the product was precipitated in ethanol, soaked in distilled water for 2 days, vacuum dried at 50°C for 6 hours, and transferred to an open mill to be pressed into an epoxidized EPDM rubber film with a thickness of 2 mm.

[0024] Based on the idea of ​​modular management of thermal conductivity and mechanical properties, the hydroxyl boron nitride thermal conductive film and the epoxidized EPDM rubber film were spread and cross-layered in the mold, and hot pressed at 140℃ and 8 MPa for 6 min to achieve interfacial cross-linking, and inverted to obtain the vertical penetration orientation of the boron nitride thermal conductive film in the EPDM matrix, and a high thermal conductivity EPDM rubber material was prepared. After testing, the tensile strength of the EPDM composite rubber was 1.23 MPa, the elongation at break was 281%, the Young's modulus was 493 kPa, and the thermal conductivity was 2.142 W / mK. Example

[0025] 10 parts of hexagonal boron nitride (h-BN) were ultrasonically dispersed in 300 parts of deionized water, and 8 parts of sodium bicarbonate (NaHCO3) were added and stirred to completely dissolve. The mixture was stirred and reacted in an oil bath at 180°C for 5 h. NaHCO3 was decomposed to produce CO2 gas to pre-expand h-BN. After the reaction, 5 parts of tunicate cellulose nanocrystals (TCNCs) were added and ultrasonically dispersed for 1 h. The TCNCs with a large aspect ratio were used for auxiliary intercalation and exfoliation, and the mixture was filtered and washed with deionized water. The obtained product was then ultrasonically dispersed in a 6 mol / L sodium hydroxide (NaOH) solution, sealed and stirred for reaction in an oil bath at 120°C for 6 h, filtered and washed with deionized water to obtain hydroxylated boron nitride nanosheets (BNNS-OH). The BNNS-OH prepared above was re-dispersed in deionized water with a concentration of 1wt%, and 1.5 parts of liquid metal (LM) was added for ultrasonic dispersion for 0.5 h. The liquid metal was evenly programmed on the surface of the BNNS-OH layer to act as a "thermal bridge". After vacuum filtration and vacuum drying at 40°C, a 0.5 mm thick hydroxyboron nitride thermal conductive film was obtained.

[0026] 100 parts of EPDM were dissolved in xylene to prepare a 4% EPDM solution, 1 part of epoxy diacetate was added, stirred for 1 min, then 8 parts of formic acid were added, stirred at 55°C for 5 min, and then 15 parts of hydrogen peroxide were added dropwise to form a uniform and stable emulsion system. After continuing the reaction for 6 hours, the product was precipitated in ethanol, soaked in distilled water for 2 days, vacuum dried at 50°C for 6 hours, and transferred to an open mill to be pressed into an epoxidized EPDM rubber film with a thickness of 2 mm.

[0027] Based on the idea of ​​modular management of thermal conductivity and mechanical properties, the hydroxyl boron nitride thermal conductive film and the epoxidized EPDM rubber film were spread and cross-layered in the mold, and hot pressed at 150℃ and 10 MPa for 8 minutes to achieve interfacial cross-linking, and inverted to obtain the vertical penetration orientation of the boron nitride thermal conductive film in the EPDM matrix, thereby preparing a high thermal conductivity EPDM rubber material. According to the test, the tensile strength of the EPDM composite rubber is 1.21 MPa, the elongation at break is 321%, the Young's modulus is 452kPa, and the thermal conductivity is 2.446 W / mK. Example

[0028] 10 parts of hexagonal boron nitride (h-BN) were ultrasonically dispersed in 350 parts of deionized water, 8 parts of sodium bicarbonate (NaHCO3) were added and stirred to completely dissolve, and stirred in an oil bath at 180℃ for 6 hours. NaHCO3 decomposed to produce CO2 gas to pre-expand h-BN. After the reaction, 5 parts of sea squirt cellulose nanocrystals (TCNCs) were added and ultrasonically dispersed for 1 hour, filtered and washed with deionized water; then the obtained product was ultrasonically dispersed in 6 mol / L sodium hydroxide (NaOH) solution, sealed and stirred in an oil bath at 120℃ for 6 hours, filtered and washed with deionized water to obtain hydroxylated boron nitride nanosheets (BNNS-OH). The BNNS-OH prepared above was re-dispersed in deionized water with a concentration of 1wt%, and 3 parts of liquid metal (LM) were added and ultrasonically dispersed for 0.5 hours. The liquid metal was evenly programmed on the surface of the BNNS-OH sheet to act as a "thermal bridge", vacuum filtered and vacuum dried at 40℃ to obtain a hydroxyl boron nitride thermal conductive film with a thickness of 0.5mm.

[0029] 100 parts of EPDM were dissolved in xylene to prepare a 4% EPDM solution, 1 part of epoxy diacetate was added, stirred for 1 min, then 8 parts of formic acid were added, stirred at 55°C for 5 min, and then 15 parts of hydrogen peroxide were added dropwise to form a uniform and stable emulsion system. After continuing the reaction for 6 hours, the product was precipitated in ethanol, soaked in distilled water for 2 days, vacuum dried at 50°C for 6 hours, and transferred to an open mill to be pressed into an epoxidized EPDM rubber film with a thickness of 2 mm.

[0030] Based on the idea of ​​modular management of thermal conductivity and mechanical properties, the hydroxyl boron nitride thermal conductive film and the epoxidized EPDM rubber film were spread and cross-layered in the mold, and hot pressed at 150℃ and 10 MPa for 10 min to achieve interfacial cross-linking, and inverted to obtain the vertical penetration orientation of the boron nitride thermal conductive film in the EPDM matrix, thereby preparing a high thermal conductivity EPDM rubber material. According to the test, the tensile strength of the EPDM composite rubber is 1.14 MPa, the elongation at break is 389%, the Young's modulus is 414kPa, and the thermal conductivity is 2.871 W / mK.

[0031] In summary, the embodiment of the present invention prepares a thermally conductive EPDM rubber with a vertically penetrating network, which has adjustable mechanical properties and thermal conductivity, and at the same time has a low modulus, and can be used in the field of thermal management of electronic devices. The above are all preferred embodiments of the present invention. For ordinary technicians in this technical field, without departing from the principle of the present invention, modifications to various equivalent forms of the present invention all belong to the scope of protection of the claims attached to this application.

Claims

1. A method for preparing a thermally conductive EPDM rubber based on an interface cross-linked vertically penetrating network, characterized in that The main raw materials of the rubber are composed of the following components, calculated by weight: EPDM 100 parts Liquid Metal LM 0.3-3 parts Hexagonal Boron Nitride h-BN 7-12 parts Ascidian nanocellulose TCNCs 2-5 parts Wherein, the liquid metal LM is a gallium indium tin alloy Ga 68.5 -In 21.5 -Sn 10 ; The plane size of the hexagonal boron nitride h-BN is 20 μm; The sea squirt nanocellulose TCNCs are prepared in the laboratory by hydrolyzing sea squirt with sulfuric acid. The specific preparation method is as follows: 50 parts of ascidian cysts were cut into pieces, ultrasonically deproteinized, decolorized and impurity-removed in acetone solvent, and then reacted with 150 mL of 62% concentrated sulfuric acid at 50°C for 1.5 h. After that, 100 mL of distilled water was added to terminate the reaction. Finally, the mixture was centrifuged, the supernatant was removed, washed and dialyzed for 5 days, and dried in a vacuum oven at 50°C to obtain ascidian cellulose nanocrystals TCNCs.

2. The method for preparing a thermally conductive EPDM rubber based on an interface cross-linked vertically penetrating network according to claim 1, characterized in that: The preparation method of the thermally conductive EPDM rubber vertically penetrating the network is as follows: S1: Preparation of Hydroxyboron Nitride Thermally Conductive Film Ultrasonic dispersion of 7-12 parts of hexagonal boron nitride h-BN in 200-350 parts of deionized water, adding 2-8 parts of sodium bicarbonate NaHCO3 and stirring to completely dissolve, stirring and reacting in an oil bath at 100-200°C for 2-6 hours, NaHCO3 decomposes to produce CO2 gas to pre-expand h-BN, after the reaction, adding 2-5 parts of sea squirt cellulose nanocrystals TCNCs and continuing ultrasonic dispersion for 1 hour, using the auxiliary intercalation exfoliation of TCNCs with a large aspect ratio, filtering and washing with deionized water; then ultrasonically dispersing the obtained product in a 3-6 mol / L sodium hydroxide NaOH solution, sealing and stirring in an oil bath at 120°C for 6 hours, filtering and washing with deionized water to obtain hydroxylated boron nitride nanosheets BNNS-OH; The BNNS-OH prepared above was re-dispersed in deionized water with a concentration of 1wt%, and 0.3-3 parts of liquid metal LM were added for ultrasonic dispersion for 0.5 h. The liquid metal was evenly programmed on the surface of the BNNS-OH layer to act as a "thermal bridge" by the coordination effect of metal-hydroxyl. The film was vacuum filtered and dried at 40°C to obtain a hydroxyl boron nitride thermal conductive film with a thickness of 0.5 mm. S2: Preparation of high thermal conductivity EPDM rubber Dissolve 100 parts of EPDM in xylene to prepare a 4% EPDM solution, add 0.2-1 parts of epoxy diacetate, stir for 1 min, then add 5-8 parts of formic acid, stir at 55°C for 5 min, then drop 8-15 parts of hydrogen peroxide to form a uniform and stable emulsion system, continue to react for 6 hours, precipitate the product in ethanol, soak it in distilled water for 2 days, vacuum dry it at 50°C for 6 hours, transfer it to an open mill and press it into an epoxidized EPDM rubber film with a thickness of 2 mm; Based on the idea of ​​modular management of thermal conductivity and mechanical properties, hydroxyl boron nitride thermal conductive film and epoxidized EPDM rubber film are spread and cross-layered in a mold. The boron nitride thermal conductive film is controlled to be 4 layers and hot pressed at 120-150℃ and 5-15 MPa for 3-12 min. The covalent reaction of hydroxyl and epoxy groups and the non-covalent effect of liquid metal and epoxy groups are used to achieve interfacial cross-linking. The vertical penetration orientation of the boron nitride thermal conductive film in the EPDM matrix is ​​obtained by inverting and flipping, thereby preparing a high thermal conductivity EPDM rubber material.

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