Boron nitride-epoxy glass polymer heat-conducting composite material and preparation method thereof

Abstract

The invention relates to a boron nitride-epoxy glass polymer heat-conducting composite material and a preparation method thereof, and belongs to the technical field of heat-conducting composite materials. The boron nitride-epoxy glass polymer heat-conducting composite material prepared by the invention is prepared by curing epoxy resin, a diphenol curing agent containing a silicon-oxygen bond and a Schiff base group, and boron nitride nanosheets grafted with phenolic hydroxyl groups and amino groups on the surfaces. According to the invention, 2, 2, 3-trimethylcyclopentane with a branched structure is introduced into the curing agent, and a phenol amine chemical chain with a branched thioether structure is chemically grafted on the surface of the boron nitride nanosheet, so that in the curing process of the composite material, the branched 2, 2, 3-trimethylcyclopentane in the curing agent can react with the phenol amine chemical chain with the branched thioether structure; the 1, 2, 3-trimethylcyclopentane can form a cross coupling structure with a coupling agent branched chain grafted on the surface of the modified boron nitride nanosheet, so that the dispersion uniformity of the boron nitride nanosheet in the composite material and the bonding strength between the boron nitride nanosheet and an epoxy resin matrix are improved, and the performance of the composite material is improved.

Description

Technical Field

[0001] This invention relates to a boron nitride-epoxy glass polymer thermally conductive composite material and its preparation method, belonging to the field of thermally conductive composite material technology. Background Technology

[0002] Insulating encapsulation materials are core foundational materials for electronic and electrical equipment. With the rapid development of microelectronics integration technology, the assembly density and operating frequency of electronic components and systems are increasing, while their size and volume are shrinking dramatically. The resulting heat dissipation difficulties severely impact the accuracy, reliability, and lifespan of these devices, becoming a bottleneck for the further development of electronic integration technology. Therefore, high thermal conductivity insulating materials provide an important material basis for comprehensively solving the thermal management problems of electronic components and systems.

[0003] Epoxy resins possess numerous advantages, including low curing shrinkage, high structural strength, and easily adjustable processing technology and properties, making them widely used in the insulation and encapsulation of high and low voltage electrical and electronic equipment. However, conventional epoxy resins are poor conductors of heat, exhibiting a low thermal conductivity. To improve the thermal conductivity of epoxy resins, thermally conductive fillers, such as boron nitride, are typically added to the epoxy resin matrix. However, boron nitride has poor affinity with epoxy resins, leading to uneven dispersion and poor bonding strength in the composite material, thus affecting the improvement of the composite's thermal conductivity. Summary of the Invention

[0004] The purpose of this invention is to provide a boron nitride-epoxy glass polymer thermally conductive composite material and its preparation method, so as to solve the problem that the dispersion uniformity and bonding strength deviation of boron nitride in the composite material are affected by the current method of using boron nitride to improve the thermal conductivity of epoxy resin, which affects the thermal conductivity of the composite material.

[0005] This invention provides a method for preparing a boron nitride-epoxy glass polymer thermally conductive composite material, comprising the following steps:

[0006] (1) Dopamine is subjected to an oxidative polymerization reaction on the surface of boron nitride nanosheets to obtain polydopamine-coated boron nitride nanosheets; then, the polydopamine-coated boron nitride nanosheets and a silane coupling agent are mixed and reacted to obtain modified boron nitride nanosheets. The chemical structure of the silane coupling agent is as follows:

[0007] ;

[0008] (2) The functional bisphenol compound, epoxy resin, modified boron nitride nanosheets and catalyst are mixed and then heated and cured to obtain a boron nitride-epoxy glass polymer thermally conductive composite material; the chemical structure of the functional bisphenol compound is as follows:

[0009] .

[0010] Preferably, the method for oxidative polymerization of dopamine on the surface of boron nitride nanosheets is as follows: dopamine hydrochloride, tris(hydroxymethyl)aminomethane, sodium chloride, ethanol and water are mixed to obtain a mixture; then boron nitride nanosheets are added to the mixture and the mixture is reacted for 10-15 hours to obtain polydopamine-coated boron nitride nanosheets.

[0011] Preferably, the mass ratio of dopamine hydrochloride, tris(hydroxymethyl)aminomethane, sodium chloride, ethanol and water is 1.7~2:0.4~0.6:2.3~2.5:70~80:110~120; and the mass ratio of boron nitride nanosheets and the mixture is 1:40~50.

[0012] Preferably, the boron nitride nanosheets have an average sheet diameter of 0.1~0.3μm and an average thickness of 20~40nm.

[0013] Preferably, the method for mixing and reacting polydopamine-coated boron nitride nanosheets and silane coupling agent is as follows: polydopamine-coated boron nitride nanosheets, silane coupling agent, ethanol and water are mixed at 90~95℃ for 12~15h to obtain modified boron nitride nanosheets.

[0014] Preferably, the mass ratio of the polydopamine-coated boron nitride nanosheets, silane coupling agent, ethanol, and water is 1:2~3:60~80:15~25.

[0015] Preferably, the mass ratio of the functional bisphenol compound to the epoxy resin is 2.5~2.7:2, and the mass of the modified boron nitride nanosheets is 7~9% of the sum of the masses of the functional bisphenol compound and the epoxy resin.

[0016] Preferably, the epoxy resin is epoxy resin E51; the catalyst is erbium trifluoromethanesulfonate, and the mass of erbium trifluoromethanesulfonate is 0.1~0.2% of the sum of the masses of the functional bisphenol compound and the epoxy resin.

[0017] Preferably, the thermosetting temperature is 110~120℃ and the time is 5~6h.

[0018] The present invention also provides a boron nitride-epoxy glass polymer thermally conductive composite material prepared by the method described above.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0020] (1) The boron nitride-epoxy glass polymer thermally conductive composite material prepared by the present invention is obtained by curing epoxy resin, a bisphenol curing agent containing silicon-oxygen bonds and Schiff base groups, and boron nitride nanosheets grafted with phenolic hydroxyl and amino groups on the surface. It has good mechanical properties, antibacterial properties, dielectric properties, thermal conductivity, self-healing and regeneration capabilities, showing good application prospects.

[0021] (2) This invention prepares a self-healing epoxy resin curing agent by introducing reversible covalent silicon-oxygen bonds and Schiff base groups into a diphenol compound. The curing agent incorporates a branched 2,2,3-trimethylcyclopentane ring and a phenolic amine chemical chain with a branched sulfide structure chemically grafted onto the surface of boron nitride nanosheets. During the curing process, the branched 2,2,3-trimethylcyclopentane ring in the curing agent can form a cross-coupled structure with the coupling agent branched onto the modified boron nitride nanosheet surface, improving the dispersion uniformity of the boron nitride nanosheets in the composite material and the bonding strength between the nanosheets and the epoxy resin matrix, thereby improving the mechanical properties, antibacterial properties, dielectric properties, and thermal conductivity of the composite material. Furthermore, the phenolic hydroxyl and amino groups contained in the chemical chains grafted onto the surface of the boron nitride nanosheets can also cross-link with the epoxy resin, further improving the bonding strength between the boron nitride nanosheets and the epoxy resin matrix. The reversible covalent bonds such as silicon-oxygen bonds and Schiff base groups in composite materials can enable the cross-linked network structure of composite materials to be adjusted and rearranged under high temperature and high pressure, thereby realizing the self-repair and reprocessing of composite materials. Attached Figure Description

[0022] Figure 1 The above is the 1H NMR spectrum of the siloxane compound prepared in Example 1 of this invention;

[0023] Figure 2 The above is the 1H NMR spectrum of the functional bisphenol compound prepared in Example 1 of this invention;

[0024] Figure 3 The above is the 1H NMR spectrum of the diamine compound prepared in Example 1 of this invention;

[0025] Figure 4 This is the 1H NMR spectrum of the silane coupling agent prepared in Example 1 of this invention. Detailed Implementation

[0026] The following examples are intended to further illustrate the content of the present invention, rather than to limit the scope of protection of the present invention.

[0027] Example 1

[0028] The preparation method of the boron nitride-epoxy glass polymer thermally conductive composite material in this embodiment includes the following steps:

[0029] (1) 2,2,3-Trimethylcyclopent-3-ene-1-acetaldehyde, tetramethyldihydrodisiloxane, and anhydrous toluene were added to a reaction vessel, nitrogen gas was introduced into the reaction vessel, and stirring was started. A 1% (w / w) isopropanol solution of chloroplatinic acid was added to the reaction vessel, heated to 90°C, and stirred for 5 h. The solvent was removed by vacuum distillation to obtain a concentrate. The concentrate was purified by column chromatography using a mixed solvent of petroleum ether and ethyl acetate in a volume ratio of 3:1 to obtain siloxane compounds. The molar ratio of 2,2,3-trimethylcyclopent-3-ene-1-acetaldehyde, tetramethyldihydrodisiloxane, and chloroplatinic acid was 2.2:1:0.0001, and the mass of toluene was 3 times the sum of the masses of 2,2,3-trimethylcyclopent-3-ene-1-acetaldehyde and tetramethyldihydrodisiloxane. The 1H NMR spectrum of the siloxane compounds is shown below. Figure 1 As shown, the chemical structure is as follows:

[0030] .

[0031] (2) Add the siloxane compound, 3-(1-aminoethyl)phenol and anhydrous ethanol to a reaction vessel, heat to 40°C, stir for 5 h, remove the solvent by vacuum distillation, and obtain a concentrate. Purify the concentrate by column chromatography using a mixed solvent of petroleum ether, ethyl acetate and methanol in a volume ratio of 6:3:2 to obtain a functional diphenol compound; wherein the molar ratio of the siloxane compound and 3-(1-aminoethyl)phenol is 1:2.1, and the mass of ethanol is 8 times the sum of the masses of the siloxane compound and 3-(1-aminoethyl)phenol. The chemical structure of 3-(1-aminoethyl)phenol is as follows:

[0032] ;

[0033] The 1H NMR spectrum of the functional bisphenol compound is shown below. Figure 2 As shown, the chemical structure is as follows:

[0034] .

[0035] (3) Add 1-amino-2-methylpropane-2-thiol, phthalic anhydride and pyridine to a reaction vessel, heat to 100℃, stir and react for 5 h, remove pyridine by vacuum distillation to obtain an intermediate; the molar ratio of 1-amino-2-methylpropane-2-thiol and phthalic anhydride is 1:1, and the mass of pyridine is 2.5 times the sum of the masses of 1-amino-2-methylpropane-2-thiol and phthalic anhydride; the chemical structure of the intermediate is as follows:

[0036] .

[0037] The intermediate, p-hydroxybenzaldehyde, and ethyl acetate were added to a reaction vessel, nitrogen gas was introduced into the vessel, and then trifluoroacetic acid was added. The mixture was stirred at room temperature for 5 hours, and the solvent was removed by vacuum distillation to obtain a concentrate. The concentrate and ethanol were added to a stirred tank and heated to 75°C. A 75% (w / w) hydrazine hydrate solution was added to the stirred tank, and the mixture was stirred and refluxed for 6 hours. The solvent was removed by vacuum distillation to obtain a crude product. The crude product was purified by column chromatography using a mixed solvent of petroleum ether, ethyl acetate, and methanol in a volume ratio of 4:5:3 to obtain a diamine compound. The molar ratio of the intermediate, p-hydroxybenzaldehyde, and trifluoroacetic acid was 2.1:1:0.05, the mass of ethyl acetate was 4 times the sum of the masses of the intermediate and p-hydroxybenzaldehyde, and the mass ratio of the concentrate, ethanol, and hydrazine hydrate solution was 1:5:0.7. The 1H NMR spectrum of the diamine compound is shown below. Figure 3 As shown, the chemical structure is as follows:

[0038] .

[0039] (4) The diamine compound, 3-isocyanate-propyltriethoxysilane, and anhydrous tetrahydrofuran were added to a reaction vessel and stirred at room temperature for 3 h. The solvent was removed by vacuum distillation to obtain a crude product. The crude product was purified by column chromatography using a mixed solvent of petroleum ether, ethyl acetate, and methanol in a volume ratio of 5:2:1 to obtain a silane coupling agent. The molar ratio of the diamine compound to 3-isocyanate-propyltriethoxysilane was 1:1, and the mass of anhydrous tetrahydrofuran was 5 times the sum of the masses of the diamine compound and 3-isocyanate-propyltriethoxysilane. The 1H NMR spectrum of the silane coupling agent is shown below. Figure 4 As shown, the chemical structure is as follows:

[0040] .

[0041] (5) Add dopamine hydrochloride, tris(hydroxymethyl)aminomethane, sodium chloride, ethanol and distilled water in a mass ratio of 1.7:0.4:2.3:70:110 to a stirred tank and stir until the solid is fully dissolved to obtain a mixture; then add boron nitride nanosheets (the average diameter of the boron nitride nanosheets is 0.1 μm and the average thickness is 20 nm) to the mixture, disperse them evenly by ultrasonication, stir and react at room temperature for 10 h, filter, wash the filtered solid with ethanol, and dry to obtain polydopamine-coated boron nitride nanosheets; the mass ratio of boron nitride nanosheets to the mixture is 1:40.

[0042] Then, polydopamine-coated boron nitride nanosheets, silane coupling agent, ethanol, and deionized water were added to a reaction vessel, stirred until homogeneous, heated to 90°C, and refluxed for 12 hours. After cooling to room temperature, the mixture was filtered, and the filter cake was washed sequentially with tetrahydrofuran and ethanol, and dried to obtain modified boron nitride nanosheets. The mass ratio of polydopamine-coated boron nitride nanosheets, silane coupling agent, ethanol, and deionized water was 1:2:60:15.

[0043] (6) The functional bisphenol compound, epoxy resin E51, modified boron nitride nanosheets and erbium trifluoromethanesulfonate were added to a stirring vessel and stirred at 40°C for 0.5 h to obtain a mixture. The mixture was then poured into a mold and vacuum degassed at 70°C for 30 min. The mixture was then heated to 110°C and kept at that temperature for 5 h. After cooling to room temperature, a boron nitride-epoxy glass polymer thermally conductive composite material was obtained. The mass ratio of the functional bisphenol compound to epoxy resin E51 was 2.5:2. The mass of the modified boron nitride nanosheets was 7% of the sum of the masses of the functional bisphenol compound and epoxy resin E51. The mass of erbium trifluoromethanesulfonate was 0.1% of the sum of the masses of the functional bisphenol compound and epoxy resin E51.

[0044] Example 2

[0045] The preparation method of the boron nitride-epoxy glass polymer thermally conductive composite material in this embodiment includes the following steps:

[0046] (1) 2,2,3-trimethylcyclopent-3-ene-1-acetaldehyde, tetramethyldihydrodisiloxane and anhydrous toluene were added to a reaction vessel, nitrogen gas was introduced into the reaction vessel, and stirring was started. A 1% (w / w) isopropanol solution of chloroplatinic acid was added to the reaction vessel, heated to 92°C, stirred for 5 h, and the solvent was removed by vacuum distillation to obtain a concentrate. The concentrate was purified by column chromatography using a mixed solvent of petroleum ether and ethyl acetate in a volume ratio of 3:1 to obtain siloxane compounds. The molar ratio of 2,2,3-trimethylcyclopent-3-ene-1-acetaldehyde, tetramethyldihydrodisiloxane and chloroplatinic acid was 2.4:1:0.0001, and the mass of toluene was 3 times the sum of the masses of 2,2,3-trimethylcyclopent-3-ene-1-acetaldehyde and tetramethyldihydrodisiloxane. The chemical structure of the siloxane compounds is as follows:

[0047] .

[0048] (2) The siloxane compound, 3-(1-aminoethyl)phenol and anhydrous ethanol were added to a reaction vessel, heated to 45°C, stirred for 6 h, and the solvent was removed by vacuum distillation to obtain a concentrate. The concentrate was purified by column chromatography using a mixed solvent of petroleum ether, ethyl acetate and methanol in a volume ratio of 6:3:2 to obtain a functional diphenol compound. The molar ratio of the siloxane compound and 3-(1-aminoethyl)phenol was 1:2.2, and the mass of ethanol was 9 times the sum of the masses of the siloxane compound and 3-(1-aminoethyl)phenol. The chemical structure of the functional diphenol compound is as follows:

[0049] .

[0050] (3) Add 1-amino-2-methylpropane-2-thiol, phthalic anhydride and pyridine to a reaction vessel, heat to 102℃, stir and react for 6 h, remove pyridine by vacuum distillation, and obtain the intermediate; the molar ratio of 1-amino-2-methylpropane-2-thiol and phthalic anhydride is 1:1, and the mass of pyridine is 2.8 times the sum of the masses of 1-amino-2-methylpropane-2-thiol and phthalic anhydride; the chemical structure of the intermediate is as follows:

[0051] .

[0052] The intermediate, p-hydroxybenzaldehyde, and ethyl acetate were added to a reaction vessel, nitrogen gas was introduced into the vessel, and then trifluoroacetic acid was added. The reaction was stirred at room temperature for 6 hours, and the solvent was removed by vacuum distillation to obtain a concentrate. The concentrate and ethanol were added to a stirred tank and heated to 77°C. A 78% (w / w) hydrazine hydrate solution was added to the stirred tank, and the mixture was stirred and refluxed for 7 hours. The solvent was removed by vacuum distillation to obtain a crude product. The crude product was purified by column chromatography using a mixed solvent of petroleum ether, ethyl acetate, and methanol in a volume ratio of 4:5:3 to obtain a diamine compound. The molar ratio of the intermediate, p-hydroxybenzaldehyde, and trifluoroacetic acid was 2.1:1:0.06, the mass of ethyl acetate was 5 times the sum of the masses of the intermediate and p-hydroxybenzaldehyde, and the mass ratio of the concentrate, ethanol, and hydrazine hydrate solution was 1:5:0.8. The chemical structure of the diamine compound is as follows:

[0053] .

[0054] (4) The diamine compound, 3-isocyanate-propyltriethoxysilane and anhydrous tetrahydrofuran were added to the reaction vessel and stirred at room temperature for 3 h. The solvent was removed by vacuum distillation to obtain the crude product. The crude product was purified by column chromatography using a mixed solvent of petroleum ether, ethyl acetate and methanol in a volume ratio of 5:2:1 to obtain the silane coupling agent. The molar ratio of the diamine compound and 3-isocyanate-propyltriethoxysilane was 1:1, and the mass of anhydrous tetrahydrofuran was 5 times the sum of the masses of the diamine compound and 3-isocyanate-propyltriethoxysilane. The chemical structure of the silane coupling agent is as follows:

[0055] .

[0056] (5) Add dopamine hydrochloride, tris(hydroxymethyl)aminomethane, sodium chloride, ethanol and distilled water in a mass ratio of 1.9:0.5:2.4:75:115 to a stirred tank and stir until the solid is fully dissolved to obtain a mixture; then add boron nitride nanosheets (the average diameter of the boron nitride nanosheets is 0.2 μm and the average thickness is 30 nm) to the mixture, disperse them evenly by ultrasonication, stir and react at room temperature for 12 h, filter, wash the filtered solid with ethanol, and dry to obtain polydopamine-coated boron nitride nanosheets; the mass ratio of boron nitride nanosheets to the mixture is 1:45.

[0057] Then, polydopamine-coated boron nitride nanosheets, silane coupling agent, ethanol, and deionized water were added to a reaction vessel, stirred until homogeneous, heated to 92°C, and stirred under reflux for 14 hours. After cooling to room temperature, the mixture was filtered, and the filter cake was washed sequentially with tetrahydrofuran and ethanol, and dried to obtain modified boron nitride nanosheets. The mass ratio of polydopamine-coated boron nitride nanosheets, silane coupling agent, ethanol, and deionized water was 1:2:70:19.

[0058] (6) The functional bisphenol compound, epoxy resin E51, modified boron nitride nanosheets and erbium trifluoromethanesulfonate were added to a stirring vessel and stirred at 45°C for 0.7 h to obtain a mixture. The mixture was then poured into a mold and vacuum degassed at 75°C for 30 min. The mixture was then heated to 115°C and kept at that temperature for 5 h. After cooling to room temperature, a boron nitride-epoxy glass polymer thermally conductive composite material was obtained. The mass ratio of the functional bisphenol compound to epoxy resin E51 was 2.6:2. The mass of the modified boron nitride nanosheets was 8% of the sum of the masses of the functional bisphenol compound and epoxy resin E51, and the mass of erbium trifluoromethanesulfonate was 0.1% of the sum of the masses of the functional bisphenol compound and epoxy resin E51.

[0059] Example 3

[0060] The preparation method of the boron nitride-epoxy glass polymer thermally conductive composite material in this embodiment includes the following steps:

[0061] (1) 2,2,3-trimethylcyclopent-3-ene-1-acetaldehyde, tetramethyldihydrodisiloxane and anhydrous toluene were added to a reaction vessel, nitrogen gas was introduced into the reaction vessel, and stirring was started. A 1% (w / w) isopropanol solution of chloroplatinic acid was added to the reaction vessel, heated to 95°C, stirred for 6 h, and the solvent was removed by vacuum distillation to obtain a concentrate. The concentrate was purified by column chromatography using a mixed solvent of petroleum ether and ethyl acetate in a volume ratio of 3:1 to obtain siloxane compounds. The molar ratio of 2,2,3-trimethylcyclopent-3-ene-1-acetaldehyde, tetramethyldihydrodisiloxane and chloroplatinic acid was 2.4:1:0.0002, and the mass of toluene was 4 times the sum of the masses of 2,2,3-trimethylcyclopent-3-ene-1-acetaldehyde and tetramethyldihydrodisiloxane. The chemical structure of the siloxane compounds is as follows:

[0062] .

[0063] (2) Add the siloxane compound, 3-(1-aminoethyl)phenol and anhydrous ethanol to a reaction vessel, heat to 50°C, stir and react for 7 h, remove the solvent by vacuum distillation to obtain a concentrate, and purify the concentrate by column chromatography using a mixed solvent of petroleum ether, ethyl acetate and methanol in a volume ratio of 6:3:2 to obtain the functional diphenol compound; wherein the molar ratio of the siloxane compound and 3-(1-aminoethyl)phenol is 1:2.3, and the mass of ethanol is 10 times the sum of the masses of the siloxane compound and 3-(1-aminoethyl)phenol. The chemical structure of the functional diphenol compound is as follows:

[0064] .

[0065] (3) Add 1-amino-2-methylpropane-2-thiol, phthalic anhydride and pyridine to a reaction vessel, heat to 105℃, stir and react for 6 h, remove pyridine by vacuum distillation to obtain an intermediate; the molar ratio of 1-amino-2-methylpropane-2-thiol and phthalic anhydride is 1:1, and the mass of pyridine is 3 times the sum of the masses of 1-amino-2-methylpropane-2-thiol and phthalic anhydride; the chemical structure of the intermediate is as follows:

[0066] .

[0067] The intermediate, p-hydroxybenzaldehyde, and ethyl acetate were added to a reaction vessel, nitrogen gas was introduced into the vessel, and then trifluoroacetic acid was added. The mixture was stirred at room temperature for 7 hours, and the solvent was removed by vacuum distillation to obtain a concentrate. The concentrate and ethanol were added to a stirred tank and heated to 80°C. An 80% (w / w) hydrazine hydrate solution was added to the stirred tank, and the mixture was stirred and refluxed for 8 hours. The solvent was removed by vacuum distillation to obtain a crude product. The crude product was purified by column chromatography using a mixed solvent of petroleum ether, ethyl acetate, and methanol in a volume ratio of 4:5:3 to obtain a diamine compound. The molar ratio of the intermediate, p-hydroxybenzaldehyde, and trifluoroacetic acid was 2.2:1:0.06, the mass of ethyl acetate was 5 times the sum of the masses of the intermediate and p-hydroxybenzaldehyde, and the mass ratio of the concentrate, ethanol, and hydrazine hydrate solution was 1:6:0.9. The chemical structure of the diamine compound is as follows:

[0068] .

[0069] (4) The diamine compound, 3-isocyanopropyltriethoxysilane and anhydrous tetrahydrofuran were added to the reaction vessel and stirred at room temperature for 4 h. The solvent was removed by vacuum distillation to obtain the crude product. The crude product was purified by column chromatography using a mixed solvent of petroleum ether, ethyl acetate and methanol in a volume ratio of 5:2:1 to obtain the silane coupling agent. The molar ratio of the diamine compound and 3-isocyanopropyltriethoxysilane was 1:1, and the mass of anhydrous tetrahydrofuran was 6 times the sum of the masses of the diamine compound and 3-isocyanopropyltriethoxysilane. The chemical structure of the silane coupling agent is as follows:

[0070] .

[0071] (5) Add dopamine hydrochloride, tris(hydroxymethyl)aminomethane, sodium chloride, ethanol and distilled water in a mass ratio of 2:0.6:2.5:80:120 to a stirred tank and stir until the solid is fully dissolved to obtain a mixture; then add boron nitride nanosheets (the average diameter of the boron nitride nanosheets is 0.3 μm and the average thickness is 40 nm) to the mixture, disperse them evenly by ultrasonication, stir and react at room temperature for 15 h, filter, wash the filtered solid with ethanol, and dry to obtain polydopamine-coated boron nitride nanosheets; the mass ratio of boron nitride nanosheets to the mixture is 1:50.

[0072] Then, polydopamine-coated boron nitride nanosheets, silane coupling agent, ethanol, and deionized water were added to a reaction vessel, stirred until homogeneous, heated to 95°C, and refluxed for 15 hours. After cooling to room temperature, the mixture was filtered, and the filter cake was washed sequentially with tetrahydrofuran and ethanol, and dried to obtain modified boron nitride nanosheets. The mass ratio of polydopamine-coated boron nitride nanosheets, silane coupling agent, ethanol, and deionized water was 1:3:80:25.

[0073] (6) The functional bisphenol compound, epoxy resin E51, modified boron nitride nanosheets and erbium trifluoromethanesulfonate were added to a stirring vessel and stirred at 50°C for 1 h to obtain a mixture. The mixture was then poured into a mold and vacuum degassed at 80°C for 30 min. The mixture was then heated to 120°C and kept at that temperature for 6 h. After cooling to room temperature, a boron nitride-epoxy glass polymer thermally conductive composite material was obtained. The mass ratio of the functional bisphenol compound to epoxy resin E51 was 2.7:2. The mass of the modified boron nitride nanosheets was 9% of the sum of the masses of the functional bisphenol compound and epoxy resin E51. The mass of erbium trifluoromethanesulfonate was 0.2% of the sum of the masses of the functional bisphenol compound and epoxy resin E51.

[0074] Comparative Example 1

[0075] The difference between the preparation method of the boron nitride-epoxy glass polymer thermally conductive composite material in this comparative example and the preparation method of the boron nitride-epoxy glass polymer thermally conductive composite material in Example 1 is that in step (1) of the preparation method of the boron nitride-epoxy glass polymer thermally conductive composite material in this comparative example, 2,2,3-trimethylcyclopent-3-ene-1-acetaldehyde is replaced with 5-norbornene-2-carboxaldehyde.

[0076] Comparative Example 2

[0077] The difference between the preparation method of the boron nitride-epoxy glass polymer thermally conductive composite material in this comparative example and the preparation method of the boron nitride-epoxy glass polymer thermally conductive composite material in Example 1 is that in step (1) of the preparation method of the boron nitride-epoxy glass polymer thermally conductive composite material in this comparative example, 2,2,3-trimethylcyclopent-3-en-1-acetaldehyde is replaced with 2-methylpent-4-enal.

[0078] Comparative Example 3

[0079] The difference between the preparation method of the boron nitride-epoxy glass polymer thermally conductive composite material in this comparative example and the preparation method of the boron nitride-epoxy glass polymer thermally conductive composite material in Example 1 is that in step (2) of the preparation method of the boron nitride-epoxy glass polymer thermally conductive composite material in this comparative example, 3-(1-aminoethyl)phenol is replaced with 4-(1-aminoethyl)phenol.

[0080] Comparative Example 4

[0081] The difference between the preparation method of the boron nitride-epoxy glass polymer thermally conductive composite material in this comparative example and the preparation method of the boron nitride-epoxy glass polymer thermally conductive composite material in Example 1 is that in step (3) of the preparation method of the boron nitride-epoxy glass polymer thermally conductive composite material in this comparative example, 1-amino-2-methylpropane-2-thiol is replaced with 3-aminopropanethiol.

[0082] Comparative Example 5

[0083] The preparation method of the boron nitride-epoxy glass polymer thermally conductive composite material in this comparative example differs from that in Example 1 only in that the silane coupling agent used in step (5) of the preparation method of the boron nitride-epoxy glass polymer thermally conductive composite material in this comparative example is prepared as follows: 4-amino-3-(3-aminopropyl)phenol, 3-isocyanate-propyltriethoxysilane and anhydrous tetrahydrofuran are added to the reaction vessel and stirred at room temperature for 3 hours. The solvent was removed by vacuum distillation to obtain a crude product. The crude product was then purified by column chromatography using a mixed solvent of petroleum ether, ethyl acetate, and methanol in a volume ratio of 5:2:1 to obtain a silane coupling agent. The molar ratio of 4-amino-3-(3-aminopropyl)phenol to 3-isocyanate-propyltriethoxysilane was 1:1, and the mass of anhydrous tetrahydrofuran was five times the sum of the masses of 4-amino-3-(3-aminopropyl)phenol and 3-isocyanate-propyltriethoxysilane. The chemical structure of the silane coupling agent is as follows:

[0084] .

[0085] Comparative Example 6

[0086] The difference between the preparation method of the boron nitride-epoxy glass polymer thermally conductive composite material in this comparative example and the preparation method of the boron nitride-epoxy glass polymer thermally conductive composite material in Example 1 is that the silane coupling agent used in step (5) of the preparation method of the boron nitride-epoxy glass polymer thermally conductive composite material in this comparative example is 3-aminopropyltriethoxysilane.

[0087] Experimental Example

[0088] To examine the comprehensive performance of the boron nitride-epoxy glass-based thermally conductive composite materials prepared in each embodiment and comparative example, the bending properties, impact resistance, antibacterial properties, dielectric properties, and thermal conductivity of the boron nitride-epoxy glass-based thermally conductive composite materials prepared in each embodiment and comparative example were tested. Specifically, bending strength and fracture bending strain were tested according to the provisions of standard GB / T9341-2008 "Determination of Bending Properties of Plastics"; impact strength was tested according to the provisions of standard GB / T1043.1-2008 "Determination of Impact Properties of Simply Supported Beams of Plastics"; antibacterial rate was tested according to the provisions of standard GB / T31402-2015 "Test Method for Antibacterial Properties of Plastic Surfaces"; dielectric strength was tested according to the provisions of standard GB-T 1408.1-2016 "Test Methods for Electrical Strength of Insulating Materials Part 1: Tests at Power Frequency"; and thermal conductivity was determined using a thermal conductivity meter. The test results of the flexural properties, impact resistance, antibacterial properties, dielectric properties and thermal conductivity of the boron nitride-epoxy glass polymer thermally conductive composite materials prepared in each embodiment and comparative example are shown in Table 1.

[0089] Table 1. Comprehensive performance of boron nitride-epoxy glass polymer thermally conductive composite materials

[0090]

[0091] As shown in Table 1, the boron nitride-epoxy glass polymer thermally conductive composite material prepared by this invention has good mechanical properties, antibacterial properties, dielectric properties and thermal conductivity, showing good application prospects.

[0092] As shown in Example 1 and Comparative Examples 1-2, when 2,2,3-trimethylcyclopent-3-en-1-acetaldehyde is replaced with 5-norbornene-2-carboxaldehyde or 2-methylpent-4-enal, the 2,2,3-trimethylcyclopentane ring in the prepared functional diphenol compound is replaced by the norbornene ring or the 2-methylpentane ring. This results in a decrease in the mechanical, antibacterial, dielectric, and thermal properties of the composite material. This indicates that the 2,2,3-trimethylcyclopentane ring in the composite material is beneficial for improving its mechanical, antibacterial, dielectric, and thermal properties. This is because the 2,2,3-trimethylcyclopentane ring has a branched structure, which can form a cross-coupled structure with the coupling agent branches grafted onto the surface of the modified boron nitride nanosheets during the curing process. This improves the dispersion uniformity of the boron nitride nanosheets in the composite material and the bonding strength with the epoxy resin matrix, thereby enhancing the mechanical, antibacterial, dielectric, and thermal properties of the composite material.

[0093] As can be seen from Example 1 and Comparative Example 3, when 3-(1-aminoethyl)phenol is replaced with 4-(1-aminoethyl)phenol, the amino and phenolic hydroxyl groups change from meta to para positions, the steric hindrance between them decreases, the structural regularity increases, which leads to a decrease in the mechanical interlocking force between the epoxy resin cured product and the boron nitride nanosheets, and consequently a weakening of the bonding strength of the boron nitride nanosheets, resulting in a decrease in the overall performance of the composite material.

[0094] As can be seen from Example 1 and Comparative Example 4, when 1-amino-2-methylpropane-2-thiol is replaced with 3-aminopropanethiol, the branched chains in the coupling agent are reduced, which weakens the cross-coupling effect between the modified boron nitride nanosheets and the epoxy resin cured product, affecting the dispersion uniformity and bonding strength of the boron nitride nanosheets in the composite material, and thus affecting the overall performance of the composite material.

[0095] As can be seen from Example 1 and Comparative Examples 5-6, the structure of the coupling agent grafted on the surface of the modified boron nitride nanosheets also has an important influence on the overall performance of the composite material. When the coupling agent only contains amino groups or lacks branched sulfide structures, the overall performance of the composite material decreases.

[0096] Example of effect

[0097] To investigate the self-healing and reprocessing properties of the boron nitride-epoxy glass-polymer thermally conductive composite materials prepared in each embodiment and Comparative Examples 1-3, the boron nitride-epoxy glass-polymer thermally conductive composite materials were cut in the middle, with the cross-sections of the cut materials in complete contact. A clamping force was applied to the two cut pieces, and they were placed in a 95°C oven for 1 hour to undergo self-healing. After removal, the flexural strength W2 of the self-healed thermally conductive composite material was tested, and the ratio of W2 to the original flexural strength W1 of the thermally conductive composite material was calculated to obtain the repair efficiency. Additionally... The boron nitride-epoxy glass polymer thermally conductive composite material was pulverized to obtain pulverized material with an average particle size of 1 mm. The pulverized material was then placed in a hot press and hot-pressed at 135°C and 8 MPa for 30 min to obtain a regenerated thermally conductive composite material. The flexural strength W3 of the regenerated thermally conductive composite material was tested, and the ratio of W3 to the original flexural strength W1 of the thermally conductive composite material was calculated to obtain the regeneration efficiency. The self-healing and reprocessing properties of the boron nitride-epoxy glass polymer thermally conductive composite materials prepared in each example and comparative examples 1-3 are shown in Table 2.

[0098] Table 2 Self-healing and reprocessing properties of boron nitride-epoxy glass-polymer thermally conductive composites

[0099]

[0100] As shown in Table 2, the boron nitride-epoxy glass-like polymer thermally conductive composite material prepared in this invention exhibits good self-healing and regeneration capabilities. This is because the composite material contains reversible covalent bonds such as silicon-oxygen bonds and Schiff base groups, which enable the composite material to adjust and rearrange its network structure under high temperature and pressure, thus demonstrating self-healing and reprocessing capabilities. Furthermore, as shown in Example 1 and Comparative Examples 1-3, the 2,2,3-trimethylcyclopentane and 3-(1-aminoethyl)phenol units in the functional bisphenol compounds also have a certain influence on the self-healing and regeneration capabilities of the composite material.

Claims

1. A method for preparing a boron nitride-epoxy glass polymer thermally conductive composite material, characterized in that, Includes the following steps: (1) Dopamine is subjected to an oxidative polymerization reaction on the surface of boron nitride nanosheets to obtain polydopamine-coated boron nitride nanosheets; then, the polydopamine-coated boron nitride nanosheets and a silane coupling agent are mixed and reacted to obtain modified boron nitride nanosheets. The chemical structure of the silane coupling agent is as follows: ； (2) The functional bisphenol compound, epoxy resin, modified boron nitride nanosheets and catalyst are mixed and then heated and cured to obtain a boron nitride-epoxy glass polymer thermally conductive composite material; the chemical structure of the functional bisphenol compound is as follows: 。 2. The preparation method of the boron nitride-epoxy glass-like polymer thermally conductive composite material as described in claim 1, characterized in that, The method for oxidative polymerization of dopamine on boron nitride nanosheets is as follows: Dopamine hydrochloride, tris(hydroxymethyl)aminomethane, sodium chloride, ethanol and water are mixed to obtain a mixture; then boron nitride nanosheets are added to the mixture and the mixture is reacted for 10-15 hours to obtain polydopamine-coated boron nitride nanosheets.

3. The preparation method of the boron nitride-epoxy glass-like polymer thermally conductive composite material as described in claim 2, characterized in that, The mass ratio of dopamine hydrochloride, tris(hydroxymethyl)aminomethane, sodium chloride, ethanol and water is 1.7~2:0.4~0.6:2.3~2.5:70~80:110~120; the mass ratio of boron nitride nanosheets and the mixture is 1:40~50.

4. The preparation method of the boron nitride-epoxy glass-like polymer thermally conductive composite material as described in claim 2, characterized in that, The boron nitride nanosheets have an average diameter of 0.1~0.3μm and an average thickness of 20~40nm.

5. The preparation method of the boron nitride-epoxy glass-like polymer thermally conductive composite material as described in claim 1, characterized in that, The method for mixing and reacting polydopamine-coated boron nitride nanosheets and silane coupling agents is as follows: polydopamine-coated boron nitride nanosheets, silane coupling agents, ethanol and water are mixed at 90~95℃ for 12~15h to obtain modified boron nitride nanosheets.

6. The method for preparing the boron nitride-epoxy glass-like thermally conductive composite material as described in claim 5, characterized in that, The mass ratio of the polydopamine-coated boron nitride nanosheets, silane coupling agent, ethanol, and water is 1:2~3:60~80:15~25.

7. The method for preparing the boron nitride-epoxy glass-like thermally conductive composite material as described in claim 1, characterized in that, The mass ratio of the functional bisphenol compound to the epoxy resin is 2.5~2.7:2, and the mass of the modified boron nitride nanosheets is 7~9% of the sum of the masses of the functional bisphenol compound and the epoxy resin.

8. The method for preparing the boron nitride-epoxy glass-like thermally conductive composite material as described in claim 7, characterized in that, The epoxy resin is epoxy resin E51; the catalyst is erbium trifluoromethanesulfonate, and the mass of erbium trifluoromethanesulfonate is 0.1~0.2% of the sum of the masses of the functional bisphenol compound and the epoxy resin.

9. The method for preparing the boron nitride-epoxy glass-based thermally conductive composite material as described in claim 1, 7, or 8, characterized in that, The thermosetting temperature is 110~120℃, and the time is 5~6h.

10. A boron nitride-epoxy glass-polymer thermally conductive composite material prepared by the method described in any one of claims 1-9.

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