Insulating flame-retardant weather-resistant polymer composite material and preparation method thereof

Abstract

The invention relates to an insulating flame-retardant weather-resistant polymer composite material and a preparation method thereof, and belongs to the technical field of polymer composite materials. The epoxy resin-based composite material prepared by the preparation method disclosed by the invention has good insulating property, heat dissipation property, mechanical property, ultraviolet aging resistance and heat-resistant and flame-retardant properties at the same time. Functional modification is carried out on the nanometer aluminum oxide and the silicon carbide fibers, the two solid materials are added into the epoxy resin at the same time, and the spherical nanometer aluminum oxide and the fibrous silicon carbide fibers are cross-linked with the epoxy resin to form a more compact and ordered net structure, so that the contact area with an epoxy resin matrix is increased; therefore, a better reinforcing effect is exerted, and the epoxy resin composite material is ensured to have good insulating, flame-retardant, heat-conducting and mechanical properties.

Description

TECHNICAL FIELD

[0001] The present application relates to an insulating flame-retardant weather-resistant polymer composite material and a preparation method thereof, and belongs to the technical field of polymer composite materials. BACKGROUND

[0002] With the rapid development of electrical equipment towards high voltage, high power and high capacity, especially high-voltage motors, extra-high voltage converter valves and high-voltage high-power insulated gate bipolar transistors, etc. electrical equipment, a large amount of heat flow is generated during operation, which makes it face more thermal faults and fire risks, and shortens the service life of electrical equipment. Among them, epoxy resin has the advantages of high insulation, light weight, easy processing, corrosion resistance and low cost, and can be widely used as an insulating dielectric material for electrical equipment. However, most polymers are flammable, and once a fire occurs, the rapid spread of the fire and the possible generation of a large amount of toxic smoke will bring great difficulties to fire rescue and seriously threaten people's production and life safety. And the thermal conductivity of the polymer is small, and the heat dissipation effect is poor, which cannot meet the heat dissipation demand of the electrical equipment.

[0003] In order to improve the thermal conductivity of the polymer, the current method is to add high thermal conductivity fillers to the polymer. The shape, particle size, distribution state, filler concentration and interfacial thermal resistance between the filler and the matrix will affect the thermal conductivity of the filled composite material. In order to obtain a composite material with good heat dissipation effect and insulation effect at the same time, an electrically insulating inorganic thermal conductive filler, such as aluminum oxide, magnesium oxide, silicon carbide, aluminum nitride and zinc oxide, is usually added to the polymer matrix. However, the insulation performance of these electrically insulating inorganic thermal conductive fillers is often poorer than that of the polymer matrix, so that the addition of the thermal conductive filler to improve the thermal conductivity of the composite material often leads to the deterioration of the insulation performance of the composite material. Therefore, there is an urgent need to provide a preparation method of a polymer composite material with good insulation performance and thermal conductivity. SUMMARY

[0004] The purpose of the present application is to provide an insulating flame-retardant weather-resistant polymer composite material and a preparation method thereof, to solve the problem that the current polymer composite material cannot simultaneously obtain good insulation performance and thermal conductivity.

[0005] The present application provides a preparation method of an insulating flame-retardant weather-resistant polymer composite material, comprising the following steps:

[0006] (1) The surface of nano-aluminum oxide is modified by diacetylsilane coupling agent to obtain silane-modified nano-aluminum oxide, and then the alkyne group on the silane-modified nano-aluminum oxide and the azide group in the imidazole azide compound are subjected to click reaction to obtain functionally modified nano-aluminum oxide;

[0007] The surface of the silicon carbide fiber is modified by using a diacetylenic silane coupling agent to obtain silane-modified silicon carbide fiber, and then the acetylenic group on the silane-modified silicon carbide fiber and the azido group in the imidazole azide compound are subjected to click reaction to obtain functionally modified silicon carbide fiber; the chemical structure of the diacetylenic silane coupling agent is as follows:

[0008] ;

[0009] The chemical structure of the imidazole azide compound is as follows:

[0010] ;

[0011] (2) The epoxy resin, curing agent, functionally modified nano-alumina and functionally modified silicon carbide fiber are uniformly mixed and then subjected to hot-pressing curing to obtain an insulating, flame-retardant and weather-resistant polymer composite material.

[0012] Preferably, the surface of the nano-alumina is modified by using a diacetylenic silane coupling agent in the following manner: nano-alumina, diacetylenic silane coupling agent, water and ethanol in a mass ratio of 1:1.2-1.5:2-3:12-15 are mixed and reacted at 80-90°C for 15-20h to obtain silane-modified nano-alumina.

[0013] Preferably, the acetylenic group on the silane-modified nano-alumina and the azido group in the imidazole azide compound are subjected to click reaction in the following manner: the silane-modified nano-alumina and the imidazole azide compound are mixed and reacted in a solvent under the action of sodium ascorbate and copper sulfate pentahydrate for 15-18h to obtain functionally modified nano-alumina; the mass ratio of the silane-modified nano-alumina and the imidazole azide compound is 1:1.5-2, the molar ratio of the imidazole azide compound and sodium ascorbate is 1:1.4-1.8, and the mass ratio of sodium ascorbate and copper sulfate pentahydrate is 0.24:0.15-0.2.

[0014] Preferably, the average particle size of the nano-alumina is 20-30nm.

[0015] Preferably, the surface of the silicon carbide fiber is modified by using a diacetylenic silane coupling agent in the following manner: silicon carbide fiber, diacetylenic silane coupling agent, water and ethanol in a mass ratio of 1:0.8-1.2:2-3:12-15 are mixed and reacted at 80-90°C for 15-20h to obtain silane-modified silicon carbide fiber.

[0016] Preferably, the method for carrying out click reaction between the alkyne group on the silane-modified silicon carbide fiber and the azido group in the imidazole azide compound is as follows: the silane-modified silicon carbide fiber and the imidazole azide compound are mixed in a solvent under the action of sodium ascorbate and copper sulfate pentahydrate to obtain the function-modified silicon carbide fiber; the mass ratio of the silane-modified silicon carbide fiber and the imidazole azide compound is 1:1.2-1.5, the molar ratio of the imidazole azide compound and sodium ascorbate is 1:1.4-1.8, and the mass ratio of sodium ascorbate and copper sulfate pentahydrate is 0.24:0.15-2.

[0017] Preferably, the average diameter of the silicon carbide fiber is 0.1-0.5 microns, and the average length is 20-30 microns.

[0018] Preferably, the mass ratio of the function-modified nanometer alumina and the function-modified silicon carbide fiber is 8-10:3-5.

[0019] Preferably, the sum of the mass of the function-modified nanometer alumina and the mass of the function-modified silicon carbide fiber is 3-5% of the mass of the epoxy resin; the epoxy resin is composed of epoxy resin E51 and E44 with a mass ratio of 5-6:1-2; the curing agent is composed of diethylene triamine and tetraethylene pentaamine with a mass ratio of 3-4:1-2; the temperature of the hot-pressing curing is 45-50 DEG C, the pressure is 5-6 MPa, and the time is 25-30 hours.

[0020] An insulating flame-retardant weather-resistant polymer composite prepared by the preparation method of the insulating flame-retardant weather-resistant polymer composite.

[0021] Compared with the prior art, the application has the following beneficial effects:

[0022] (1) The diacetylenic silane coupling agent is used for chemically modifying nano-alumina and silicon carbide fibers, diacetylenic groups are grafted on the surface of the nano-alumina and silicon carbide fibers, then the diacetylenic groups grafted on the surface of the nano-alumina and silicon carbide fibers and imidazole azide compounds are subjected to click reaction, triazole groups and carboxylic imidazole groups are chemically bonded on the surface of the nano-alumina and silicon carbide fibers, finally, the nano-alumina and silicon carbide fibers grafted with organic silicon, triazole groups and carboxylic imidazole groups are added into an epoxy resin system as fillers for hot-pressing curing molding, the epoxy groups in the epoxy resin and the curing agent and the carboxyl groups and imidazole groups on the surface of the nano-alumina and silicon carbide fibers are subjected to chemical crosslinking, and the composite material is obtained. The oleophobic carboxyl groups and imidazole groups and the oleophilic organic silicon and triazole groups can effectively improve the dispersion uniformity of the nano-alumina and silicon carbide fibers in the epoxy system, avoid the aggregation of the fillers, be beneficial to the formation of uniformly distributed heat conduction channels, improve the thermal conductivity of the composite material, and can avoid the internal accumulation of the nano-alumina and silicon carbide fibers in the interface region of the epoxy resin matrix due to overlapping and aggregation, so as to weaken the migration of carriers in the interface region, and further improve the resistivity of the composite material; and the carboxyl groups and imidazole groups can be crosslinked with the epoxy resin, improve the interfacial bonding force between the nano-alumina and silicon carbide fibers and the epoxy resin matrix, make the epoxy composite material form a more compact structure, and further improve the mechanical properties, ultraviolet aging resistance and heat resistance and flame resistance of the composite material.

[0023] (2) The nano-alumina and silicon carbide fibers are functionally modified, and the two kinds of solid materials are simultaneously added into the epoxy resin, the spherical nano-alumina and the fibrous silicon carbide fibers can form a more compact and ordered network structure after being crosslinked with the epoxy resin, improve the contact area with the epoxy resin matrix, and further play a better reinforcing effect, so as to ensure that the epoxy resin composite material has good insulation, flame retardation, thermal conductivity and mechanical properties. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 The nuclear magnetic hydrogen spectrum of the bromo diacetylenic trimethyl silane compound prepared in Example 1 of the present application is shown in the figure;

[0025] Figure 2 The nuclear magnetic hydrogen spectrum of the diacetylenic silane coupling agent prepared in Example 1 of the present application is shown in the figure;

[0026] Figure 3 The nuclear magnetic hydrogen spectrum of the imidazole azide compound prepared in Example 1 of the present application is shown in the figure. DETAILED DESCRIPTION

[0027] The following examples are intended to further illustrate the content of the present application, but not limit the protection scope of the present application.

[0028] Example 1

[0029] The preparation method of the insulating flame-retardant weather-resistant polymer composite of the embodiment comprises the following steps:

[0030] (1) 1-bromo-3,5-diiodobenzene, dichlorobis(triphenylphosphine)palladium, cuprous iodide, triethylamine and anhydrous tetrahydrofuran with a molar ratio of 30:0.12:0.35:150:650 are added into a reaction kettle and stirred uniformly, and a 10% mass fraction of trimethylsilylethynyl anhydrous tetrahydrofuran solution is added dropwise into the reaction kettle (the molar ratio of trimethylsilylethynyl and 1-bromo-3,5-diiodobenzene is 2.2:1), after the dropwise addition is completed, the reaction is stirred at room temperature for 15 min, then heated to 70°C and stirred to reflux for 12 h, cooled to room temperature, filtered, and the filtrate is collected and distilled under reduced pressure to obtain a crude product, which is purified by column chromatography with a mixed solvent of petroleum ether and dichloromethane with a volume ratio of 3:1 to obtain a bromo-diacetylenyl trimethylsilane compound; the nuclear magnetic resonance hydrogen spectrum of the bromo-diacetylenyl trimethylsilane compound is shown in Figure 1 , and the chemical structure is as follows:

[0031] .

[0032] (2) chlorotrimethoxysilane and anhydrous tetrahydrofuran with a mass ratio of 1:10 are added into a reaction kettle, nitrogen is introduced, and the reaction kettle is placed in an ice water bath, then magnesium powder is added, stirring is started, and a 8% mass fraction of bromo-diacetylenyl trimethylsilane anhydrous tetrahydrofuran solution is added dropwise into the reaction kettle, after the dropwise addition is completed, the ice water bath is removed, heated to 45°C under light shielding conditions, and stirred to react for 25 h, then cooled to room temperature and centrifuged, and the supernatant obtained by centrifugation is distilled under reduced pressure to obtain an intermediate; the molar ratio of chlorotrimethoxysilane, magnesium powder and bromo-diacetylenyl trimethylsilane compound is 1:1:0.85.

[0033] The intermediate, methanol and dichloromethane with a mass ratio of 1:9:5 are added into a reaction kettle, stirred uniformly, and then potassium carbonate (the mass ratio of potassium carbonate and the intermediate is 2.5:1) is added, stirred to react at room temperature for 4 h, water and dichloromethane are sequentially added into the reaction kettle for extraction, the organic phase obtained by extraction is distilled under reduced pressure to obtain a crude product, and the crude product is purified by column chromatography with ethyl acetate, dichloromethane and petroleum ether with a volume ratio of 1:1:2 to obtain a diacetylenyl silane coupling agent; the nuclear magnetic resonance hydrogen spectrum of the diacetylenyl silane coupling agent is shown in Figure 2 , and the chemical structure is as follows:

[0034] .

[0035] (3) adding 2-aminoimidazole-4-carboxylic acid, dilute acetic acid solution, dilute hydrochloric acid and deionized water with a mass ratio of 1:2.5:2.5:2.5 into a reaction kettle, then cooling the materials in the reaction kettle to-5℃, and then adding a 10% sodium nitrite solution dropwise into the reaction kettle, after the dropwise addition is completed, stirring the reaction for 2 hours; then under the condition of avoiding light, adding a 12% sodium azide solution dropwise into the reaction kettle, and continuing to stir until no nitrogen is generated, adding dichloromethane into the reaction kettle for extraction, and then reducing and distilling the organic phase obtained by extraction to obtain a crude product, and then purifying the crude product by column chromatography using methanol, dichloromethane and petroleum ether with a volume ratio of 1:3:2 to obtain an imidazole azide compound; wherein the molar ratio of 2-aminoimidazole-4-carboxylic acid, sodium nitrite and sodium azide is 1:1.05:1.05, the mass fraction of the dilute acetic acid solution is 7%, and the mass fraction of the dilute hydrochloric acid is 4%; the chemical structure of 2-aminoimidazole-4-carboxylic acid is as follows:

[0036] ;

[0037] The nuclear magnetic hydrogen spectrum of the imidazole azide compound is as shown in Figure 3 , and the chemical structure is as follows:

[0038] .

[0039] (4) adding nano-alumina (γ-Al2O3, average particle size of 20 nm), diacetylsilane coupling agent, deionized water and ethanol with a mass ratio of 1:1.2:2:12 into a reaction kettle, then introducing nitrogen into the reaction kettle, heating to 80℃, stirring and refluxing for 15 hours, cooling to room temperature, then filtering, and then washing the filter cake with deionized water and ethanol in sequence, and then drying to obtain silane-modified nano-alumina; then adding the silane-modified nano-alumina and anhydrous tetrahydrofuran with a mass ratio of 1:40 into the reaction kettle, introducing nitrogen into the reaction kettle, then adjusting the temperature of the materials in the reaction kettle to-5℃, then adding a 30% imidazole azide compound solution in anhydrous tetrahydrofuran into the reaction kettle, stirring uniformly, then adding a mixed solution composed of sodium ascorbate, copper sulfate pentahydrate and deionized water with a mass ratio of 0.24:0.15:5 into the reaction kettle, stirring at room temperature for 15 hours, filtering, washing the filter cake with tetrahydrofuran and ethanol in sequence, and then drying to obtain functionally modified nano-alumina; wherein the mass ratio of the silane-modified nano-alumina and the imidazole azide compound is 1:1.5, and the molar ratio of the imidazole azide compound and sodium ascorbate is 1:1.4.

[0040] (5) Put silicon carbide fiber (average diameter 0.1 μm, average length 20 μm), diacetylsilyl coupling agent, deionized water and ethanol with a mass ratio of 1:0.8:2:12 into a reaction kettle, then introduce nitrogen into the reaction kettle, heat to 80℃, and stir to reflux for 15 h. After cooling to room temperature, filter, wash the filter cake with deionized water and ethanol in turn, and dry to obtain silyl-modified silicon carbide fiber. Then put the silyl-modified silicon carbide fiber and anhydrous tetrahydrofuran with a mass ratio of 1:50 into a reaction kettle, introduce nitrogen into the reaction kettle, then adjust the temperature of the material in the reaction kettle to -5℃, and then put a 30% imidazole azide compound solution in anhydrous tetrahydrofuran into the reaction kettle, stir uniformly, then put a mixed solution composed of sodium ascorbate, copper sulfate pentahydrate and deionized water with a mass ratio of 0.24:0.15:5 into the reaction kettle, and stir at room temperature for 15 h. After filtration, wash the filter cake with tetrahydrofuran and ethanol in turn, and dry to obtain function-modified silicon carbide fiber. The mass ratio of the silyl-modified silicon carbide fiber and the imidazole azide compound is 1:1.2, and the molar ratio of the imidazole azide compound and sodium ascorbate is 1:1.4.

[0041] (6) Put epoxy resins E51 and E44 with a mass ratio of 5:1 as an epoxy matrix resin into a stirring kettle, heat to 30℃, and stir uniformly. Then put a mixture of function-modified nano-aluminum oxide and function-modified silicon carbide fiber with a mass ratio of 8:3 as a filler, stir uniformly, and then cool to room temperature. Then put a mixture of diethylene triamine and tetraethylene pentaamine with a mass ratio of 3:1 as a curing agent, stir uniformly, pour into a stainless steel mold, and then put the stainless steel mold on a flat vulcanization instrument for heat pressing and curing. The temperature for heat pressing and curing is 45℃, the pressure is 5 MPa, and the time is 25 h. After heat pressing and curing, cool to room temperature, take out the cured mixture, and obtain an insulating, flame-retardant and weather-resistant polymer composite material. The mass of the filler is 3% of the mass of the epoxy matrix resin, the molar ratio of the active hydrogen in the curing agent to the epoxy group in the epoxy matrix resin is 1:1, the molar amount of active hydrogen in 1 mol of diethylene triamine is 5 mol, and the molar amount of active hydrogen in 1 mol of tetraethylene pentaamine is 7 mol.

[0042] Example 2

[0043] The preparation method of the insulating, flame-retardant and weather-resistant polymer composite material of the present embodiment comprises the following steps:

[0044] (1) 1-Bromo-3,5-diiodobenzene, bis(triphenylphosphine)palladium dichloride, cuprous iodide, triethylamine, and anhydrous tetrahydrofuran in a molar ratio of 30:0.14:0.39:155:670 were added to a reaction vessel and stirred until homogeneous. A 12% (w / w) solution of anhydrous tetrahydrofuran in trimethylsilylacetylene was added dropwise to the reaction vessel (the molar ratio of trimethylsilylacetylene to 1-bromo-3,5-diiodobenzene was 2.3:1). After the addition was complete, the mixture was stirred at room temperature for 15 min, then heated to 72 °C and refluxed for 13 h. After cooling to room temperature, the mixture was filtered, and the filtrate was collected and distilled under reduced pressure to obtain a crude product. The crude product was purified by column chromatography using a mixed solvent of petroleum ether and dichloromethane in a volume ratio of 3:1 to obtain a brominated diethynyltrimethylsilane compound. The chemical structure of the brominated diethynyltrimethylsilane compound is as follows:

[0045] .

[0046] (2) Add chlorotrimethoxysilane and anhydrous tetrahydrofuran in a mass ratio of 1:11 to the reaction vessel, purge with nitrogen, place in an ice-water bath, then add magnesium powder, start stirring, and then add an anhydrous tetrahydrofuran solution of 9% bromidediethynyltrimethylsilane compound dropwise to the reaction vessel. After the dropwise addition is completed, remove the ice-water bath, heat to 48°C under light-protected conditions, stir and react for 27 h, cool to room temperature and centrifuge, and distill the supernatant obtained by centrifugation under reduced pressure to obtain the intermediate; wherein, the molar ratio of chlorotrimethoxysilane, magnesium powder and bromidediethynyltrimethylsilane compound is 1:1:0.88.

[0047] An intermediate, methanol, and dichloromethane in a mass ratio of 1:9:5 were added to a reaction vessel and stirred until homogeneous. Potassium carbonate (potassium carbonate to intermediate mass ratio of 2.8:1) was then added, and the mixture was stirred at room temperature for 5 hours. Water and dichloromethane were added sequentially to the reaction vessel for extraction. The extracted organic phase was distilled under reduced pressure to obtain a crude product. The crude product was purified by column chromatography using ethyl acetate, dichloromethane, and petroleum ether in a volume ratio of 1:1:2 to obtain a diynylsilane coupling agent. The chemical structure of the diynylsilane coupling agent is as follows:

[0048] .

[0049] (3) Add 2-aminoimidazole-4-carboxylic acid, dilute acetic acid solution, dilute hydrochloric acid and deionized water in a mass ratio of 1:2.6:2.7:2.5 to the reactor. Then cool the material in the reactor to -2℃. Next, add 11% sodium nitrite solution dropwise to the reactor. After the addition is complete, stir the reaction for 2.5 hours. Then, under light-protected conditions, add 14% sodium azide solution dropwise to the reactor and continue stirring until no more nitrogen gas is generated. Dichloromethane was added to the reactor for extraction. The extracted organic phase was then distilled under reduced pressure to obtain a crude product. The crude product was purified by column chromatography using a mixture of methanol, dichloromethane, and petroleum ether in a volume ratio of 1:3:2 to obtain an imidazole azide compound. The molar ratio of 2-aminoimidazolium-4-carboxylic acid, sodium nitrite, and sodium azide was 1:1.09:1.08, the mass fraction of the dilute acetic acid solution was 7%, and the mass fraction of the dilute hydrochloric acid solution was 5%. The chemical structure of the imidazole azide compound is as follows:

[0050] .

[0051] (4) Nano-alumina (γ-Al2O3, average particle size 25nm), diynylsilane coupling agent, deionized water and ethanol in a mass ratio of 1:1.4:3:14 were added to a reaction vessel. Nitrogen gas was then introduced into the reaction vessel, and the mixture was heated to 85°C and stirred under reflux for 18 hours. After cooling to room temperature, the mixture was filtered. The filter cake was washed sequentially with deionized water and ethanol, and dried to obtain silane-modified nano-alumina. Then, silane-modified nano-alumina and anhydrous tetrahydrofuran in a mass ratio of 1:45 were added to the reaction vessel. Nitrogen gas was introduced into the reaction vessel, and the temperature of the material in the reaction vessel was increased. The temperature was adjusted to -2℃, and then an anhydrous tetrahydrofuran solution of 35% imidazole azide compound was added to the reactor and stirred evenly. Then, a mixture of sodium ascorbate, copper sulfate pentahydrate and deionized water in a mass ratio of 0.24:0.15:5 was added to the reactor and stirred at room temperature for 16 hours. After filtration, the filter cake was washed with tetrahydrofuran and ethanol, respectively, and dried to obtain functionalized nano-alumina. The mass ratio of silane-modified nano-alumina to imidazole azide compound was 1:1.8, and the molar ratio of imidazole azide compound to sodium ascorbate was 1:1.6.

[0052] (5) Add silicon carbide fibers (average diameter 0.3 μm, average length 25 μm), diynylsilane coupling agent, deionized water and ethanol in a mass ratio of 1:0.9:2:13 to a reaction vessel, then introduce nitrogen gas into the reaction vessel, heat to 85°C, stir and reflux for 18 h, cool to room temperature and filter, wash the filter cake with deionized water and ethanol respectively, and dry to obtain silane-modified silicon carbide fibers; then add silane-modified silicon carbide fibers and anhydrous tetrahydrofuran in a mass ratio of 1:55 to the reaction vessel, introduce nitrogen gas into the reaction vessel, and then add the materials in the reaction vessel to the reaction vessel. The temperature was adjusted to -2℃, and then an anhydrous tetrahydrofuran solution of 35% imidazole azide compound was added to the reactor and stirred evenly. Then, a mixture of sodium ascorbate, copper sulfate pentahydrate and deionized water in a mass ratio of 0.24:0.15:5 was added to the reactor and stirred at room temperature for 16 hours. After filtration, the filter cake was washed with tetrahydrofuran and ethanol, respectively, and dried to obtain functional modified silicon carbide fiber. The mass ratio of silane-modified silicon carbide fiber to imidazole azide compound was 1:1.4, and the molar ratio of imidazole azide compound to sodium ascorbate was 1:1.6.

[0053] (6) Epoxy resins E51 and E44 in a mass ratio of 5:2 were added to a mixing tank as epoxy resins, heated to 35°C, and stirred evenly. Then, a mixture of functional modified nano-alumina and functional modified silicon carbide fiber in a mass ratio of 9:4 was added as filler. After stirring evenly, the mixture was cooled to room temperature. Then, a mixture of diethylenetriamine and tetraethylenepentamine in a mass ratio of 3:2 was added as curing agent. After stirring evenly, the mixture was poured into a stainless steel mold. The stainless steel mold was then placed on a flat vulcanizing apparatus for hot pressing curing. The hot pressing curing temperature was 48°C, the pressure was 6 MPa, and the time was 27 h. After hot pressing curing, the mixture was cooled to room temperature and the cured mixture was taken out to obtain an insulating, flame-retardant, and weather-resistant polymer composite material. The mass of the filler was 4% of the mass of the epoxy resin. The ratio of the molar amount of active hydrogen in the curing agent to the molar amount of epoxy groups in the epoxy resin was 1:1. The molar amount of active hydrogen in each mol of diethylenetriamine was 5 mol, and the molar amount of active hydrogen in each mol of tetraethylenepentamine was 7 mol.

[0054] Example 3

[0055] The preparation method of the insulating, flame-retardant, and weather-resistant polymer composite material in this embodiment includes the following steps:

[0056] (1) 1-Bromo-3,5-diiodobenzene, bis(triphenylphosphine)palladium dichloride, cuprous iodide, triethylamine, and anhydrous tetrahydrofuran in a molar ratio of 30:0.15:0.45:160:680 were added to a reaction vessel and stirred until homogeneous. A 15% (w / w) solution of anhydrous tetrahydrofuran in trimethylsilylacetylene was added dropwise to the reaction vessel (the molar ratio of trimethylsilylacetylene to 1-bromo-3,5-diiodobenzene was 2.5:1). After the addition was complete, the mixture was stirred at room temperature for 15 min, then heated to 75 °C and refluxed for 15 h. After cooling to room temperature, the mixture was filtered, and the filtrate was collected and distilled under reduced pressure to obtain a crude product. The crude product was purified by column chromatography using a mixed solvent of petroleum ether and dichloromethane in a volume ratio of 3:1 to obtain a brominated diethynyltrimethylsilane compound. The chemical structure of the brominated diethynyltrimethylsilane compound is as follows:

[0057] .

[0058] (2) Add chlorotrimethoxysilane and anhydrous tetrahydrofuran in a mass ratio of 1:12 to the reaction vessel, purge with nitrogen, place in an ice-water bath, then add magnesium powder, start stirring, and then add a 10% mass fraction of anhydrous tetrahydrofuran solution of bromodiethynyltrimethylsilane compound to the reaction vessel. After the addition is complete, remove the ice-water bath, heat to 50°C under light-protected conditions, stir and react for 30 h, cool to room temperature and centrifuge, and distill the supernatant obtained by centrifugation under reduced pressure to obtain the intermediate; wherein, the molar ratio of chlorotrimethoxysilane, magnesium powder and bromodiethynyltrimethylsilane compound is 1:1:0.9.

[0059] An intermediate, methanol, and dichloromethane in a mass ratio of 1:10:5 were added to a reaction vessel and stirred until homogeneous. Potassium carbonate (in a mass ratio of 3:1 to the intermediate) was then added, and the mixture was stirred at room temperature for 6 hours. Water and dichloromethane were added sequentially to the reaction vessel for extraction. The extracted organic phase was distilled under reduced pressure to obtain a crude product. The crude product was purified by column chromatography using ethyl acetate, dichloromethane, and petroleum ether in a volume ratio of 1:1:2 to obtain a diynylsilane coupling agent. The chemical structure of the diynylsilane coupling agent is as follows:

[0060] .

[0061] (3) 2-Aminoimidazol-4-carboxylic acid, dilute acetic acid solution, dilute hydrochloric acid and deionized water in a mass ratio of 1:2.8:2.8:2.8 were added to the reaction vessel. The material in the reaction vessel was then cooled to 0°C. A 12% sodium nitrite solution was then added dropwise to the reaction vessel. After the addition was completed, the reaction was stirred for 3 hours. Then, under light-protected conditions, a 15% sodium azide solution was added dropwise to the reaction vessel. The mixture was stirred until no more nitrogen gas was generated. Dichloromethane was added to the reaction vessel for extraction. The organic phase obtained from the extraction was distilled under reduced pressure to obtain a crude product. The crude product was purified by column chromatography using methanol, dichloromethane and petroleum ether in a volume ratio of 1:3:2 to obtain an imidazole azide compound. The molar ratio of 2-aminoimidazol-4-carboxylic acid, sodium nitrite and sodium azide was 1:1.1:1.1. The mass fraction of the dilute acetic acid solution was 8%, and the mass fraction of the dilute hydrochloric acid was 5%. The chemical structure of the imidazole azide compound is as follows:

[0062] .

[0063] (4) Nano-alumina (γ-Al2O3, average particle size 30nm), diynylsilane coupling agent, deionized water and ethanol in a mass ratio of 1:1.5:3:15 were added to a reaction vessel. Nitrogen gas was then introduced into the reaction vessel, and the mixture was heated to 90°C and stirred under reflux for 20 hours. After cooling to room temperature, the mixture was filtered. The filter cake was washed sequentially with deionized water and ethanol, and dried to obtain silane-modified nano-alumina. Then, silane-modified nano-alumina and anhydrous tetrahydrofuran in a mass ratio of 1:50 were added to the reaction vessel. Nitrogen gas was introduced into the reaction vessel, and the mixture in the reaction vessel was then... The temperature was adjusted to 0℃, and then an anhydrous tetrahydrofuran solution of 40% imidazole azide compound was added to the reaction vessel and stirred evenly. Then, a mixture of sodium ascorbate, copper sulfate pentahydrate and deionized water in a mass ratio of 0.24:0.15:5 was added to the reaction vessel and stirred at room temperature for 18 hours. After filtration, the filter cake was washed with tetrahydrofuran and ethanol, respectively, and dried to obtain functional modified nano-alumina. The mass ratio of silane-modified nano-alumina to imidazole azide compound was 1:2, and the molar ratio of imidazole azide compound to sodium ascorbate was 1:1.8.

[0064] (5) Add silicon carbide fibers (average diameter 0.5 μm, average length 30 μm), diynylsilane coupling agent, deionized water and ethanol in a mass ratio of 1:1.2:3:15 to a reaction vessel. Then, introduce nitrogen gas into the reaction vessel, heat to 90°C, stir and reflux for 20 h, cool to room temperature and filter. Wash the filter cake with deionized water and ethanol respectively, and dry to obtain silane-modified silicon carbide fibers. Then, add silane-modified silicon carbide fibers and anhydrous tetrahydrofuran in a mass ratio of 1:60 to the reaction vessel, introduce nitrogen gas into the reaction vessel, and then add the materials in the reaction vessel to the reaction vessel. The temperature was adjusted to 0℃, and then an anhydrous tetrahydrofuran solution of 40% imidazole azide compound was added to the reaction vessel and stirred evenly. Then, a mixture of sodium ascorbate, copper sulfate pentahydrate and deionized water in a mass ratio of 0.24:0.15:5 was added to the reaction vessel and stirred at room temperature for 18 hours. After filtration, the filter cake was washed with tetrahydrofuran and ethanol, respectively, and dried to obtain functional modified silicon carbide fiber. The mass ratio of silane modified silicon carbide fiber to imidazole azide compound was 1:1.5, and the molar ratio of imidazole azide compound to sodium ascorbate was 1:1.8.

[0065] (6) Epoxy resins E51 and E44 in a mass ratio of 6:2 were added to a mixing tank as epoxy resins, heated to 40°C, and stirred evenly. Then, a mixture of functional modified nano-alumina and functional modified silicon carbide fiber in a mass ratio of 10:5 was added as filler. After stirring evenly, the mixture was cooled to room temperature. Then, a mixture of diethylenetriamine and tetraethylenepentamine in a mass ratio of 4:2 was added as curing agent. After stirring evenly, the mixture was poured into a stainless steel mold. The stainless steel mold was then placed on a flat vulcanizing apparatus for hot pressing curing. The hot pressing curing temperature was 50°C, the pressure was 6 MPa, and the time was 30 h. After hot pressing curing, the mixture was cooled to room temperature and the cured mixture was taken out to obtain an insulating, flame-retardant, and weather-resistant polymer composite material. The filler mass was 5% of the epoxy resin mass, the molar ratio of active hydrogen in the curing agent to the molar ratio of epoxy groups in the epoxy resin was 1:1, the molar amount of active hydrogen in each mol of diethylenetriamine was 5 mol, and the molar amount of active hydrogen in each mol of tetraethylenepentamine was 7 mol.

[0066] Comparative Example 1

[0067] The difference between the preparation method of the insulating, flame-retardant and weather-resistant polymer composite material of this comparative example and the preparation method of the insulating, flame-retardant and weather-resistant polymer composite material of Example 1 is that in step (3) of the preparation method of the insulating, flame-retardant and weather-resistant polymer composite material of this comparative example, 2-aminoimidazole-4-carboxylic acid is replaced with 2-amino-4,5-dicarboxylic acid imidazole.

[0068] Comparative Example 2

[0069] The difference between the preparation method of the insulating, flame-retardant and weather-resistant polymer composite material in this comparative example and the preparation method of the insulating, flame-retardant and weather-resistant polymer composite material in Example 1 is that the imidazole azide compound in steps (4) and (5) of the preparation method of the insulating, flame-retardant and weather-resistant polymer composite material in this comparative example is 2-azidoimidazole.

[0070] Comparative Example 3

[0071] The difference between the preparation method of the insulating, flame-retardant, and weather-resistant polymer composite material in this comparative example and the preparation method of the insulating, flame-retardant, and weather-resistant polymer composite material in Example 1 is that in steps (4) and (5) of the preparation method of the insulating, flame-retardant, and weather-resistant polymer composite material in this comparative example, the diynylsilane coupling agent is replaced with (4-ethynylphenyl)trimethoxysilane. The chemical structure of (4-ethynylphenyl)trimethoxysilane is as follows:

[0072] .

[0073] Comparative Example 4

[0074] The difference between the preparation method of the insulating, flame-retardant and weather-resistant polymer composite material in this comparative example and the preparation method of the insulating, flame-retardant and weather-resistant polymer composite material in Example 1 is that the amount of functionally modified nano-alumina in step (6) of the preparation method of the insulating, flame-retardant and weather-resistant polymer composite material in this comparative example is 0.

[0075] Comparative Example 5

[0076] The difference between the preparation method of the insulating, flame-retardant and weather-resistant polymer composite material in this comparative example and the preparation method of the insulating, flame-retardant and weather-resistant polymer composite material in Example 1 is that the amount of functionally modified silicon carbide fiber in step (6) of the preparation method of the insulating, flame-retardant and weather-resistant polymer composite material in this comparative example is 0.

[0077] Example of effect

[0078] To evaluate the insulation, flame retardant, mechanical, thermal conductivity, and weather resistance of the insulating, flame-retardant, and weather-resistant polymer composites prepared in the various embodiments and comparative examples, the volume resistivity, limiting oxygen index, tensile strength, elongation at break, impact strength, thermal conductivity, and UV aging resistance of the composites were tested. Specifically, volume resistivity was tested according to ASTM D6095-1999; limiting oxygen index was tested according to ISO 4589-1999; tensile strength and elongation at break were tested according to GB / T 1040-1992; impact strength was tested according to GB / T 1843-2008; the thermal conductivity was tested as follows: first, the thermal diffusivity of the composite was measured using a laser thermal conductivity meter; then, the density and specific heat capacity of the composite were measured; finally, the product of the thermal diffusivity, density, and specific heat capacity was calculated to obtain the thermal conductivity; the UV aging resistance was tested as follows: the composite was subjected to UV irradiation at 60°C and an intensity of 45 μW / cm². 2 The composite material was aged for 800 hours under certain conditions, and then the volume resistivity of the aged composite material was tested. The ratio of the volume resistivity of the aged composite material to that of the composite material before aging was calculated, and this ratio was used to characterize the UV aging resistance. The test results of volume resistivity, limiting oxygen index, tensile strength, elongation at break, impact strength, thermal conductivity, and UV aging resistance of the insulating, flame-retardant, and weather-resistant polymer composite materials prepared in each embodiment and comparative example are shown in Table 1.

[0079] Table 1. Volume resistivity, limiting oxygen index, and tensile strength of composite materials

[0080] Strength, elongation at break, impact strength, thermal conductivity and UV aging resistance

[0081]

[0082] As shown in Table 1, this invention chemically modifies nano-alumina and silicon carbide fibers using a diynylsilane coupling agent. After grafting diynyl groups onto the surface of nano-alumina and silicon carbide fibers, a click reaction is performed using the grafted diynyl groups and imidazole azide compounds to chemically bond triazole groups and carboxylic acid imidazole groups onto the surface of nano-alumina and silicon carbide fibers. Finally, the nano-alumina and silicon carbide fibers with organosilicon, triazole, and carboxylic acid imidazole groups grafted onto their surfaces are added as fillers to an epoxy resin system for hot pressing and curing. The epoxy groups in the epoxy resin, the curing agent, and the carboxyl and imidazole groups on the surface of the nano-alumina and silicon carbide fibers undergo chemical cross-linking to obtain a composite material. Oleophobic carboxyl and imidazole groups, as well as lipophilic organosilicon and triazole groups, can effectively improve the dispersion uniformity of nano-alumina and silicon carbide fibers in epoxy systems, prevent filler agglomeration, facilitate the formation of uniformly distributed thermally conductive pathways, and improve the thermal conductivity of composite materials. Simultaneously, they can prevent the internal accumulation of nano-alumina and silicon carbide fibers in the epoxy resin matrix due to overlap and agglomeration, thereby weakening carrier migration in the interfacial region and increasing the resistivity of the composite material. Furthermore, carboxyl and imidazole groups can crosslink with epoxy resin, increasing the interfacial bonding force between nano-alumina and silicon carbide fibers and the epoxy resin matrix, enabling the epoxy composite material to form a more compact structure, thus improving the mechanical properties, UV aging resistance, and heat resistance and flame retardancy of the composite material.

[0083] As shown in Example 1 and Comparative Examples 1-2, the number of carboxyl groups in the imidazole azide compound has a significant impact on the performance of the composite material. When 2-aminoimidazolium-4-carboxylic acid is replaced with 2-amino-4,5-dicarboxylic acid imidazole, the number of carboxyl groups grafted onto the filler surface increases, hydrophilicity is enhanced, surface activity is weakened, and the number of crosslinking sites with epoxy resin increases, leading to an increase in the degree of crosslinking of the composite material, increased shrinkage, and decreased performance. When 2-azidoimidazolium is used as the imidazole azide compound, only imidazole groups are grafted onto the filler surface, hydrophilicity is weakened, and the number of crosslinking sites with epoxy resin is reduced, resulting in a lower degree of crosslinking of the composite material. The bonding strength between nano-alumina and silicon carbide fibers in the epoxy resin matrix is ​​weakened, leading to a decrease in the performance of the composite material.

[0084] As can be seen from Example 1 and Comparative Example 3, after replacing the diynylsilane coupling agent with (4-ethynylphenyl)trimethoxysilane, the number and density of triazole groups and carboxyimidazole groups grafted on the surface of nano-alumina and silicon carbide fibers decreased. On the one hand, this led to a reduction in the crosslinking sites between the filler and the resin matrix. On the other hand, the reduction in the number of organic triazole groups on the surface of the filler resulted in poorer dispersion uniformity of the filler in the epoxy resin matrix, thereby affecting the overall performance of the composite material.

[0085] As can be seen from Example 1 and Comparative Examples 4-5, when functionally modified nano-alumina or functionally modified silicon carbide fibers are used alone, the overall performance of the composite material deviates. This is because the combination of spherical nano-alumina and fibrous silicon carbide fibers can form a more dense and orderly network structure after crosslinking with epoxy resin, thereby increasing the contact area with the epoxy resin matrix and thus exerting a better reinforcing effect.

Claims

1. A method for preparing an insulating, flame-retardant, and weather-resistant polymer composite material, characterized in that, Includes the following steps: (1) Nano-alumina is surface modified with diyne-silane coupling agent to obtain silane-modified nano-alumina. Then, the alkynyl group on the silane-modified nano-alumina and the azide group in the imidazole azide compound are clicked to obtain functionally modified nano-alumina. Silicon carbide fibers were surface-modified using a diynylsilane coupling agent to obtain silane-modified silicon carbide fibers. Then, the ynyl groups on the silane-modified silicon carbide fibers and the azide groups in the imidazole azide compound underwent a click reaction to obtain functionally modified silicon carbide fibers. The chemical structure of the diynylsilane coupling agent is as follows: ； The chemical structure of the imidazole azide compound is as follows: ； (2) After mixing epoxy resin, curing agent, functional modified nano alumina and functional modified silicon carbide fiber, hot pressing curing is performed to obtain an insulating, flame-retardant and weather-resistant polymer composite material.

2. The preparation method of the insulating, flame-retardant, and weather-resistant polymer composite material as described in claim 1, characterized in that, The method for surface modification of nano-alumina using a diynylsilane coupling agent is as follows: nano-alumina, diynylsilane coupling agent, water and ethanol in a mass ratio of 1:1.2~1.5:2~3:12~15 are mixed and reacted at 80~90℃ for 15~20h to obtain silane-modified nano-alumina.

3. The preparation method of the insulating, flame-retardant, and weather-resistant polymer composite material as described in claim 1, characterized in that, The method for click reaction of alkynyl groups on silane-modified nano-alumina and azido groups in imidazole azide compounds is as follows: silane-modified nano-alumina and imidazole azide compounds are mixed and reacted in a solvent with sodium ascorbate and copper sulfate pentahydrate for 15-18 hours to obtain functionalized nano-alumina; the mass ratio of silane-modified nano-alumina to imidazole azide compounds is 1:1.5-2, the molar ratio of imidazole azide compounds to sodium ascorbate is 1:1.4-1.8, and the mass ratio of sodium ascorbate to copper sulfate pentahydrate is 0.24:0.15-0.

2.

4. The method for preparing the insulating, flame-retardant, and weather-resistant polymer composite material according to any one of claims 1-3, characterized in that, The average particle size of the nano-alumina is 20~30nm.

5. The method for preparing the insulating, flame-retardant, and weather-resistant polymer composite material as described in claim 1, characterized in that, The method for surface modification of silicon carbide fibers using a diynylsilane coupling agent is as follows: silicon carbide fibers, diynylsilane coupling agent, water and ethanol in a mass ratio of 1:0.8~1.2:2~3:12~15 are mixed and reacted at 80~90℃ for 15~20h to obtain silane-modified silicon carbide fibers.

6. The method for preparing the insulating, flame-retardant, and weather-resistant polymer composite material as described in claim 1, characterized in that, The method for click reaction of alkynyl groups on silane-modified silicon carbide fibers and azido groups in imidazole azide compounds is as follows: silane-modified silicon carbide fibers and imidazole azide compounds are mixed and reacted in a solvent under the action of sodium ascorbate and copper sulfate pentahydrate to obtain functional modified silicon carbide fibers; the mass ratio of silane-modified silicon carbide fibers to imidazole azide compounds is 1:1.2~1.5, the molar ratio of imidazole azide compounds to sodium ascorbate is 1:1.4~1.8, and the mass ratio of sodium ascorbate to copper sulfate pentahydrate is 0.24:0.15~2.

7. The method for preparing the insulating, flame-retardant, and weather-resistant polymer composite material according to any one of claims 1, 5-6, characterized in that, The silicon carbide fibers have an average diameter of 0.1–0.5 μm and an average length of 20–30 μm.

8. The method for preparing the insulating, flame-retardant, and weather-resistant polymer composite material as described in claim 1, characterized in that, The mass ratio of the functional modified nano-alumina to the functional modified silicon carbide fiber is 8~10:3~5.

9. The method for preparing the insulating, flame-retardant, and weather-resistant polymer composite material as described in claim 1 or 8, characterized in that, The sum of the mass of the functional modified nano-alumina and the functional modified silicon carbide fiber is 3-5% of the mass of the epoxy resin; the epoxy resin is composed of epoxy resin E51 and E44 in a mass ratio of 5-6:1-2; the curing agent is composed of diethylenetriamine and tetraethylenepentamine in a mass ratio of 3-4:1-2; the hot-press curing temperature is 45-50℃, the pressure is 5-6MPa, and the time is 25-30h.

10. An insulating, flame-retardant, and weather-resistant polymer composite material prepared by the method of any one of claims 1-9.

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