Epoxy resin composite insulating material and preparation method thereof

Abstract

The invention belongs to the technical field of polymer insulating materials, and particularly relates to an epoxy resin composite insulating material and a preparation method thereof. The composite material comprises the following components in parts by weight: 60-70 parts of epoxy resin, 5-8 parts of acetone, 12-15 parts of modified glass fibers, 1-2 parts of nano SiO2, 5-8 parts of polyurethane microspheres, 10-12 parts of micron Al2O3, 2-3 parts of epoxy monomer microcapsules, 8-10 parts of a curing agent and 3-5 parts of a modifier. The material cost is effectively reduced on the premise of ensuring the insulating strength, the thermal conductivity and the mechanical property, and the influence of the high-viscosity nano filler on the processing fluidity is reduced by compounding the micron Al2O3 and the nano SiO2; nano SiO2 is directionally deposited on the surface of the fiber through electrostatic spraying, a local high-concentration nanophase is formed in an interface area, the high-proportion nano SiO2 adding requirement of a traditional matrix is replaced, the total nano material dosage is effectively reduced, and the cost is remarkably reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of polymer insulating materials, and particularly relates to an epoxy resin composite insulating material and a preparation method thereof. Background Art

[0002] Epoxy resin is a thermosetting polymer material synthesized from epoxy groups (the polycondensation reaction of epichlorohydrin and bisphenol A). Since its industrialization in the 1940s, due to its excellent adhesiveness, chemical corrosion resistance, mechanical strength, and electrical insulation properties, it has become the core matrix of insulating materials. Its curing reaction is achieved through amine or anhydride curing agents, forming a three-dimensional cross-linked network structure, which endows the material with high heat resistance and dimensional stability. Epoxy resin composite insulating materials are usually composed of an epoxy resin matrix and functional fillers. By compounding functional fillers, a multi-scale reinforcement system is constructed: for example, inorganic fillers such as SiO2 and Al2O3 improve heat resistance and mechanical strength; glass fibers in fiber reinforcements enhance mechanical properties, and aramid fibers improve impact resistance, forming a macroscopic support structure; carbon nanotubes and boron nitride in nanomaterials optimize thermal conductivity and partial discharge resistance.

[0003] Currently, epoxy resin composite insulating materials are widely used in high-voltage power equipment, such as insulators, GIS (gas-insulated switchgear), transformer bushings, etc.; integrated circuit packaging and LED heat dissipation substrates in electronic packaging, as well as stator insulation of wind turbines and motor insulation systems of electric vehicles in the new energy field; high-voltage cable insulation and high-temperature resistant components in aerospace. There are currently two major technical bottlenecks in improving the performance of current materials: in traditional reinforcement technologies, although glass fiber / mica sheet reinforcement can improve mechanical strength and arc resistance, there is a risk of delamination failure caused by weak interfacial bonding force between the resin and fibers, and a high filler addition amount may lead to deterioration of processing fluidity, a significant decrease in melt flow index, and the accumulation of internal stress during the curing process, inducing microcracks; although the nano-modification technology by adding nano-SiO2 / BN can significantly improve dielectric strength and thermal conductivity, the tendency of nano-particle agglomeration may cause local defects, combined with the high raw material cost, seriously restricting large-scale application. The current epoxy resin composite insulating materials face several core contradictions, mainly the contradiction between performance and processability, such as high filler content improving performance but damaging processability; the contradiction between cost and performance, such as significant nano-modification effects but poor economy. Therefore, based on the above problems, it is extremely necessary to develop a high-performance and low-cost composite epoxy resin insulating material through reasonable raw material adaptation and process combination. Summary of the Invention

[0004] Aiming at the defects of the prior art, the purpose of the present invention is to provide an epoxy resin composite insulating material and a preparation method thereof.

[0005] The technical effects of the present invention are achieved through the following technical solutions: An epoxy resin composite insulating material, the composition of which includes the following components in parts by weight: 60 to 70 parts of epoxy resin, 10 to 12 parts of acetone, 12 to 15 parts of modified glass fiber, 1 to 2 parts of nano-SiO2, 5 to 8 parts of polyurethane microspheres, 10 to 12 parts of micron Al2O3, 2 to 3 parts of epoxy monomer microcapsules, 8 to 10 parts of curing agent, and 3 to 5 parts of modifier.

[0006] Preferably, the curing agent is composed of ultrafine modified dicyandiamide and polythiol in a mass ratio of 7 to 8:2 to 3; Preferably, the modifier is any one of 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, and 3-glycidoxypropyltrimethoxysilane. Further preferably, it is 3-glycidoxypropyltriethoxysilane; Preferably, the specific preparation steps of the modified glass fiber are as follows: S1: Add γ-aminopropyltriethoxysilane to a 95wt% ethanol solution, adjust the pH to 4 to 5 with acetic acid, stir and mix at 500 rpm for 30 to 50 min to obtain a hydrolyzate; Immerse the glass fiber in a mixed solution of acetone / ethanol in a ratio of 1:1, perform ultrasonic treatment at 60W for 30 min, and dry at 120°C for 2 h to obtain pretreated glass fiber; S2: Add the pretreated glass fiber prepared in step S1 to the hydrolyzate, at a temperature of 40 to 50°C, impregnate for 15 to 30 min, pre-dry at 80°C for 30 min, and then raise the temperature to 120°C to cure for 1 to 2 h to obtain silane glass fiber; S3: Disperse nano-SiO2 in absolute ethanol, perform ultrasonic treatment at 300W and 40kHz for 50 to 60 min to obtain a sol; Electrostatically spray the sol onto the silane glass fiber prepared in step S2, and perform heat treatment at 120°C for 40 to 60 min to obtain modified glass fiber; Preferably, in step S1, the dosage ratio of γ-aminopropyltriethoxysilane to the ethanol solution is 2 to 3 g:100 mL; Preferably, in step S2, the dosage ratio of the pretreated glass fiber to the hydrolyzate is 1 g:3 to 5 mL; Preferably, in step S3, the dosage ratio of nano-SiO2 to absolute ethanol is 2 to 3 g:100 mL; The electrostatic spraying operation is a spraying rate of 0.5 to 1 mL / min, a fiber conveying speed of 0.5 m / min, a voltage of 30 kV, a spray gun distance of 20 to 25 cm, and repeated spraying 2 to 3 times; Preferably, the specific preparation steps of the epoxy monomer microcapsules are as follows: S101: Add bisphenol A diglycidyl ether and sodium dodecyl sulfate into deionized water, stir at 2000 - 3000 rpm for 10 - 15 min, then add hexamethylene diisocyanate and ethylenediamine, keep the temperature at 40 - 50 °C, stir at 300 rpm for 2 - 3 h, perform vacuum filtration, wash repeatedly with ethanol and deionized water for 3 times, and dry in vacuum at 40 °C for 24 h to obtain epoxy monomer microcapsules; Preferably, in step S101, the dosage ratio of bisphenol A diglycidyl ether, sodium dodecyl sulfate and deionized water is 1 g: 0.15 - 0.2 g: 10 mL; the mass dosage ratio of bisphenol A diglycidyl ether, hexamethylene diisocyanate and ethylenediamine is 1: 0.4 - 1: 0.3 - 0.5; Preferably, on the other hand, the present invention provides a preparation method of an epoxy resin composite insulating material, and the specific preparation steps are as follows: S201: Add a modifier into 50 times the weight of 90 wt% ethanol, adjust the pH to 4 - 5 with acetic acid, stir at 500 rpm for 30 - 50 min at 40 °C to obtain a modified hydrolysis solution; immerse polyurethane microspheres into the modified hydrolysis solution, perform ultrasonic treatment, centrifuge, wash repeatedly with ethanol for 3 times, and dry in vacuum at 60 °C for 12 h to obtain grafted polyurethane microspheres; S202: Mix epoxy resin and acetone, keep the temperature at 35 - 40 °C, stir at 300 rpm for 10 - 20 min, then add nano - SiO2, perform ultrasonic treatment to disperse evenly, add micron - Al2O3, stir at 500 rpm for 20 - 30 min, then sequentially add the grafted polyurethane microspheres prepared in step S201 and epoxy monomer microcapsules, stir at 200 rpm for 15 - 20 min to obtain an epoxy resin matrix; S203: Add a curing agent and modified glass fiber into the epoxy resin matrix prepared in step S202, perform vacuum degassing treatment for 30 - 60 min, then cure at 60 °C for 1 - 1.5 h, heat up to 120 °C at a rate of 5 °C / min and cure for 1.5 - 2 h, and then heat up to 150 °C at a rate of 5 °C / min and cure for 1 - 1.5 h to obtain an epoxy resin composite insulating material; Preferably, in step S201, the ultrasonic treatment parameters are temperature 50 °C, 200 - 300 W, 40 kHz, time 40 - 60 min; Preferably, in step S202, the ultrasonic treatment parameters are 150 - 200 W, 40 kHz, time 20 - 30 min.

[0007] The beneficial effects of the present invention are as follows: The present invention graft-modifies glass fibers with γ-aminopropyltriethoxysilane (KH550). The surface amino groups (-NH2) after modification form covalent bonds with the epoxy groups of epoxy resin, enhancing the interfacial chemical bonding. Then, nano-SiO2 is loaded on the fiber surface by electrostatic spraying to construct a micro-nano rough structure, and the interfacial slip is inhibited through the mechanical anchoring effect, reducing the delamination risk. The nano-SiO2 layer on the fiber surface has a high dielectric constant, which can disperse the concentration of the interfacial electric field and inhibit partial discharge. At the same time, the hydroxyl groups on the surface of SiO2 match the polarity of the resin, reducing the interfacial charge accumulation. After the polyurethane microspheres are modified with 3-glycidoxypropyltriethoxysilane (KH560), the surface epoxy groups form chemical bonding with the resin matrix, avoiding phase separation. As elastic units, the microspheres initiate crazes and absorb energy under external forces, significantly improving the impact toughness. Their elastic deformation can offset the resin curing shrinkage stress and reduce the initiation of microcracks. In addition, the dispersed distribution of the microspheres can also block the crack propagation path and form a rigid-flexible interpenetrating network with the modified glass fibers, simultaneously improving the tensile strength and fracture toughness. The uniformly dispersed nano-SiO2 delays the growth of electrical treeing through the interfacial polarization effect and improves the overall dielectric strength. Its small size effect can fill the microdefects of the resin matrix and inhibit partial discharge. The micron-sized Al2O3 forms a continuous heat conduction skeleton, quickly conducting away the local heat and avoiding insulation aging caused by temperature rise. It forms a multi-level heat conduction network in coordination with nano-SiO2 with a micron-level skeleton-nano-level filling synergy. In addition, the nano-SiO2 pre-loaded on the surface of the modified glass fibers can also serve as an anchor point to guide the directional arrangement of the SiO2 fillers directly added to the matrix, reducing the risk of agglomeration and improving the overall dispersion uniformity. The polyurea shell layer (HDI / ethylenediamine polymerization) has high mechanical strength and heat resistance, which can protect the core material (bisphenol A diglycidyl ether) from being released during processing. When microcracks occur inside the material, the stress concentration at the crack tip causes the microcapsules to rupture, and the released epoxy monomers diffuse in the crack gap, prolonging the material life. Polythiol triggers rapid pre-crosslinking at low temperature (60 °C) to form a flexible network to buffer the shrinkage stress. Dicyandiamide completes deep crosslinking under high-temperature action to ensure high crosslinking density and heat resistance. The staged curing releases the resin shrinkage gradient, effectively reducing the internal stress and avoiding curing cracking.

[0008] In summary, on the premise of ensuring the insulation strength, thermal conductivity and mechanical properties, the present invention effectively reduces the material cost. Among them, micron Al2O3 and nano SiO2 are compounded. Through the skeleton support of micron-scale fillers, the influence of high-viscosity nano-fillers on processing fluidity is reduced; the modified glass fiber is grafted with amino silane and sprayed with nano SiO2 to improve the interfacial bonding force between the single filament and the resin, reduce the fiber dosage ratio, and reduce the hindrance to the resin fluidity. Moreover, the nano SiO2 sprayed on the fiber surface is directionally deposited by electrostatic spraying to form a local high-concentration nano-phase in the interface region, replacing the need for a high proportion of nano SiO2 addition in the traditional matrix. The total nano-material dosage is effectively reduced, significantly reducing the cost; KH560-modified polyurethane microspheres are introduced, and the toughness reduction caused by the reduction of nano-fillers is compensated by the elastomer toughening effect, avoiding reliance on high-cost toughening agents such as carbon nanotubes. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only those of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0010] Figure 1 It is a graph of the mechanical strength test results of the epoxy resin composite material samples prepared in Examples 1 to 3 and Comparative Examples 1 to 4 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0011] The following will combine the embodiments of the present invention to clearly and completely describe the technical solutions of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments; based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention. It should be noted that unless otherwise specified, the raw materials involved in the present invention are purchased through conventional commercial channels.

[0012] Example 1: An epoxy resin composite insulating material, the composition of which includes the following components in parts by weight: 70 parts of epoxy resin, 10 parts of acetone, 12 parts of modified glass fiber, 1 part of nano SiO2, 5 parts of polyurethane microspheres, 10 parts of micron Al2O3, 2 parts of epoxy monomer microcapsules, 8 parts of curing agent and 3 parts of modifier.

[0013] 1. The specific preparation steps of the modified glass fiber are as follows: S1: Add 2 g of γ-aminopropyltriethoxysilane into 100 mL of 95 wt% ethanol solution, adjust the pH to 4 with acetic acid, stir and mix at 500 rpm for 30 min to obtain a hydrolysis solution; Immerse 10 g of glass fiber into a mixed solution of 100 mL of acetone / ethanol with a ratio of 1:1, perform ultrasonic treatment at 60 W for 30 min, and dry at 120 °C for 2 h to obtain pretreated glass fiber; S2: Add 10 g of the pretreated glass fiber prepared in step S1 into 30 mL of the hydrolysis solution, at a temperature of 40 °C, impregnate for 15 min, pre-dry at 80 °C for 30 min, and then heat up to 120 °C for curing for 1 h to obtain silane glass fiber; S3: Disperse 2 g of nano-SiO₂ in 100 mL of absolute ethanol, perform ultrasonic treatment at 300 W and 40 kHz for 50 min to obtain a sol; Electrostatically spray the sol onto the silane glass fiber prepared in step S2, with a spraying rate of 0.5 mL / min, a fiber conveying speed of 0.5 m / min, a voltage of 30 kV, and a spray gun distance of 20 cm, repeat spraying 2 times; Then perform heat treatment at 120 °C for 40 min to obtain modified glass fiber; 2. The specific preparation steps of the epoxy monomer microcapsules are as follows: S101: Add 10 g of bisphenol A diglycidyl ether and 1.5 g of sodium dodecyl sulfate into 100 mL of deionized water, stir at 2000 rpm for 10 min, then add 4 g of hexamethylene diisocyanate and 3 g of ethylenediamine, at a temperature of 40 °C, stir at 300 rpm for 2 h, perform vacuum filtration, wash repeatedly with ethanol and deionized water 3 times, and vacuum dry at 40 °C for 24 h to obtain epoxy monomer microcapsules; 3. The specific preparation steps of the epoxy resin composite insulating material are as follows: S201: Add 3-glycidylethoxypropylmethyldiethoxysilane into 50 times the weight of 90 wt% ethanol, adjust the pH to 4 with acetic acid, at a temperature of 40 °C, stir at 500 rpm for 30 min to obtain a modified hydrolysis solution; Immerse the polyurethane microspheres into the modified hydrolysis solution, perform ultrasonic treatment, at a temperature of 50 °C, 200 W, 40 kHz, for 40 min; Centrifuge, wash repeatedly with ethanol 3 times, and vacuum dry at 60 °C for 12 h to obtain grafted polyurethane microspheres; S202: Mix epoxy resin and acetone, at a temperature of 35 °C, stir at 300 rpm for 10 min, then add nano-SiO₂, perform ultrasonic treatment at 150 W, 40 kHz, for 20 min, add micron-sized Al₂O₃, stir at 500 rpm for 20 min, and then sequentially add the grafted polyurethane microspheres prepared in step S201 and the epoxy monomer microcapsules, stir at 200 rpm for 15 min to obtain an epoxy resin matrix; S203: Add a curing agent composed of ultrafine modified dicyandiamide and polythiol in a mass ratio of 7:3 and modified glass fibers into the epoxy resin matrix prepared in step S202, perform vacuum degassing treatment for 30 min, then cure at 60 °C for 1 h, raise the temperature to 120 °C at a rate of 5 °C / min and cure for 1.5 h, and then raise the temperature to 150 °C at a rate of 5 °C / min and cure for 1 h to obtain an epoxy resin composite insulating material.

[0014] Example 2: An epoxy resin composite insulating material, whose composition includes the following components by weight: 70 parts of epoxy resin, 11 parts of acetone, 15 parts of modified glass fibers, 1.5 parts of nano-SiO₂, 6 parts of polyurethane microspheres, 11 parts of micron Al₂O₃, 2.5 parts of epoxy monomer microcapsules, 9 parts of curing agent, and 4 parts of modifier.

[0015] 1. The specific preparation steps of the modified glass fibers are as follows: S1: Add 2.5 g of γ-aminopropyltriethoxysilane into 100 mL of 95 wt% ethanol solution, adjust the pH to 5 with acetic acid, stir and mix at 500 rpm for 40 min to obtain a hydrolysis solution; immerse 10 g of glass fibers into a mixed solution of 100 mL of acetone / ethanol with a ratio of 1:1, perform ultrasonic treatment at 60 W for 30 min, and dry at 120 °C for 2 h to obtain pretreated glass fibers; S2: Add 10 g of the pretreated glass fibers prepared in step S1 into 40 mL of the hydrolysis solution, at a temperature of 45 °C, impregnate for 30 min, pre-dry at 80 °C for 30 min, and then raise the temperature to 120 °C and cure for 1.5 h to obtain silane glass fibers; S3: Disperse 2.5 g of nano-SiO₂ in 100 mL of absolute ethanol, perform ultrasonic treatment at 300 W and 40 kHz for 55 min to obtain a sol; electrostatically spray the sol onto the silane glass fibers prepared in step S2, with a spraying rate of 0.8 mL / min, a fiber conveying speed of 0.5 m / min, a voltage of 30 kV, and a spray gun distance of 22 cm, and repeat spraying 3 times; then perform heat treatment at 120 °C for 50 min to obtain modified glass fibers; 2. The specific preparation steps of the epoxy monomer microcapsules are as follows: S101: Add 10 g of bisphenol A diglycidyl ether and 1.8 g of sodium dodecyl sulfate into deionized water, stir at 2500 rpm for 14 min, then add 8 g of hexamethylene diisocyanate and 4 g of ethylenediamine, at a temperature of 45 °C, stir at 300 rpm for 2.5 h, perform vacuum filtration, wash repeatedly with ethanol and deionized water 3 times, and vacuum dry at 40 °C for 24 h to obtain epoxy monomer microcapsules; 3. The specific preparation steps of the epoxy resin composite insulating material are as follows: S201: Add 3-glycidoxypropyltrimethoxysilane to 50 times the weight of 90 wt% ethanol, adjust the pH to 5 with acetic acid, stir at 500 rpm for 40 min at 40 °C to obtain a modified hydrolysis solution; immerse the polyurethane microspheres in the modified hydrolysis solution, perform ultrasonic treatment at 50 °C, 250 W, 40 kHz for 50 min; centrifuge, wash with ethanol 3 times repeatedly, and dry in vacuum at 60 °C for 12 h to obtain grafted polyurethane microspheres; S202: Mix epoxy resin and acetone, stir at 38 °C and 300 rpm for 15 min, then add nano-SiO2, perform ultrasonic treatment at 180 W, 40 kHz for 25 min, add micron Al2O3, stir at 500 rpm for 25 min, and then successively add the grafted polyurethane microspheres prepared in step S201 and epoxy monomer microcapsules, stir at 200 rpm for 18 min to obtain an epoxy resin matrix; S203: Add a curing agent composed of ultrafine modified dicyandiamide and polythiol in a mass ratio of 7.5:2.5 and modified glass fiber to the epoxy resin matrix prepared in step S202, perform vacuum degassing treatment for 50 min, then cure at 60 °C for 1.2 h, raise the temperature to 120 °C at a rate of 5 °C / min and cure for 1.8 h, and then raise the temperature to 150 °C at a rate of 5 °C / min and cure for 1.2 h to obtain an epoxy resin composite insulating material.

[0016] Example 3: An epoxy resin composite insulating material, the composition of which includes the following components in parts by weight: 65 parts of epoxy resin, 12 parts of acetone, 14 parts of modified glass fiber, 2 parts of nano-SiO2, 8 parts of polyurethane microspheres, 12 parts of micron Al2O3, 3 parts of epoxy monomer microcapsules, 10 parts of curing agent, and 5 parts of modifier.

[0017] 1. The specific preparation steps of the modified glass fiber are as follows: S1: Add 3 g of γ-aminopropyltriethoxysilane to 100 mL of 95 wt% ethanol solution, adjust the pH to 4.5 with acetic acid, stir and mix at 500 rpm for 50 min to obtain a hydrolysis solution; immerse 10 g of glass fiber in a mixed solution of 100 mL of acetone / ethanol mixed in a 1:1 ratio, perform ultrasonic treatment at 60 W for 30 min, and dry at 120 °C for 2 h to obtain pretreated glass fiber; S2: Add 10 g of the pretreated glass fiber prepared in step S1 to 50 mL of the hydrolysis solution, soak at 50 °C for 25 min, pre-dry at 80 °C for 30 min, and then raise the temperature to 120 °C and cure for 2 h to obtain silane glass fiber; S3: Disperse 3 g of nano - SiO₂ in 100 mL of absolute ethanol, and perform ultrasonic treatment at 300 W and 40 kHz for 60 min to obtain a sol; electrostatically spray the sol onto the silane glass fiber prepared in step S2 at a spraying rate of 1 mL / min, a fiber conveying speed of 0.5 m / min, a voltage of 30 kV, and a spray gun distance of 25 cm, and repeat spraying 3 times; then perform heat treatment at 120 °C for 60 min to obtain modified glass fiber; 2. The specific preparation steps of the epoxy monomer microcapsules are as follows: S101: Add 10 g of bisphenol A diglycidyl ether and 2 g of sodium dodecyl sulfate to 100 mL of deionized water, stir at 3000 rpm for 15 min, then add 10 g of hexamethylene diisocyanate and 5 g of ethylenediamine, keep the temperature at 50 °C, stir at 300 rpm for 3 h, perform vacuum filtration, wash repeatedly with ethanol and deionized water 3 times, and dry in vacuum at 40 °C for 24 h to obtain epoxy monomer microcapsules; 3. The specific preparation steps of the epoxy resin composite insulating material are as follows: S201: Add 3 - glycidoxypropyltriethoxysilane to 50 times the weight part of 90 wt% ethanol, adjust the pH to 4.5 with acetic acid, stir at 500 rpm at 40 °C for 50 min to obtain a modified hydrolysis solution; immerse the polyurethane microspheres in the modified hydrolysis solution, perform ultrasonic treatment at 50 °C, 300 W, and 40 kHz for 60 min; centrifuge, wash repeatedly with ethanol 3 times, and dry in vacuum at 60 °C for 12 h to obtain grafted polyurethane microspheres; S202: Mix epoxy resin and acetone, stir at 300 rpm at 40 °C for 20 min, then add nano - SiO₂, perform ultrasonic treatment at 200 W and 40 kHz for 30 min, add micron - sized Al₂O₃, stir at 500 rpm for 30 min, and then sequentially add the grafted polyurethane microspheres prepared in step S201 and epoxy monomer microcapsules, and stir at 200 rpm for 20 min to obtain an epoxy resin matrix; S203: Add a curing agent composed of ultrafine modified dicyandiamide and polythiol in a mass ratio of 8:2 and modified glass fiber to the epoxy resin matrix prepared in step S202, perform vacuum degassing treatment for 60 min, then cure at 60 °C for 1.5 h, raise the temperature to 120 °C at a rate of 5 °C / min and cure for 2 h, and then raise the temperature to 150 °C at a rate of 5 °C / min and cure for 1.5 h to obtain the epoxy resin composite insulating material.

[0018] Comparative Example 1: This comparative example provides an epoxy resin composite insulating material, which is basically the same as that in Example 3, except that in Comparative Example 1, the glass fiber is not subjected to nano - SiO₂ spraying treatment.

[0019] Comparative Example 2: This comparative example provides an epoxy resin composite insulating material, which is basically the same as that of Example 3, except that in Comparative Example 2, polyurethane microspheres and modifiers are not added, and the dosage of nano-SiO2 is increased to 8 parts.

[0020] Comparative Example 3: This comparative example provides an epoxy resin composite insulating material, which is basically the same as that of Example 3, except that in Comparative Example 3, only dicyandiamide is used as the curing agent.

[0021] Comparative Example 4: This comparative example provides an epoxy resin composite insulating material, which is basically the same as that of Example 3, except that in Comparative Example 4, epoxy monomer microcapsules are not added.

[0022] Performance test: Mechanical strength test: Using a universal testing machine, the interfacial shear strength of the epoxy resin composite material samples prepared in Examples 1-3 and Comparative Examples 1-4 was tested according to ASTM D1002. Using a pendulum impact testing machine, the impact strength of the epoxy resin composite material samples prepared in Example 3 and Comparative Examples 1-4 was tested according to GB / T 2567-2021. The test results are as Figure 1 shown.

[0023] It can be seen from Figure 1 the results that the epoxy resin composite material prepared by the present invention has excellent mechanical strength and can effectively adapt to various high-strength scenario applications. Especially, the sample prepared according to the ratio in Example 3 has the best effect. It can be seen from the results of Comparative Example 1 and Example 3 that the mechanical anchoring effect and the interfacial electric field dispersion function of the sprayed nano-SiO2 are missing. Although the chemical bonding of the silane coupling agent still exists, the interfacial bonding strength lacks physical anchoring and is affected to a certain extent. The decrease in the interfacial bonding force leads to cracks being more likely to propagate along the fiber-resin interface, resulting in a significant decrease in mechanical strength. It can be seen from the results of Comparative Example 2 and Example 3 that the elastic stress buffering of the polyurethane microspheres and the modification of KH560 by chemical bonding are missing, and the interfacial stress concentration is aggravated. The increase in the proportion of nano-SiO2 used may lead to agglomeration, weakening the dispersion uniformity, and instead forming interfacial defects. In addition, the elastic microsphere toughening mechanism completely disappears, the impact energy absorption ability drops significantly, and the increase in the proportion of nano-SiO2 leads to an increase in the brittleness of the matrix and a decrease in the crack propagation resistance, resulting in a significant decrease in mechanical strength. It can be seen from the results of Comparative Example 3 and Example 3 that due to the action of only one curing agent, the staged curing fails, and the interfacial residual stress may be reviewed. In addition, although the high-temperature curing of dicyandiamide still ensures the crosslinking density, the microcracks caused by the internal stress may weaken the interfacial bonding, resulting in a significant decrease in mechanical strength. It can be seen from the results of Comparative Example 4 and Example 3 that when the material is damaged by impact, the epoxy monomer cannot be released to repair the cracks, and the crack propagation rate may be slightly faster than that of Example 3, and its impact strength is slightly affected.

[0024] Dielectric strength / thermal conductivity test: The dielectric strength of the epoxy resin composite samples prepared in Example 3 and Comparative Examples 1-4 was tested according to GB / T 1408.1-2006; the thermal conductivity of the epoxy resin composite samples prepared in Example 3 and Comparative Examples 1-4 was tested with reference to the standard ASTM E1461; with reference to the standard GB / T 10582-2008, the epoxy resin composite samples prepared in Example 3 and Comparative Examples 1-4 were placed in an environment of 85 °C / 95% humidity for 48 h; after taking out, the surface moisture was wiped dry and restored in a standard environment of 23 °C / 50% humidity for 24 h; a high resistance meter was used to measure the volume resistivity, and the insulation resistance recovery rate (%) = resistance after recovery / initial resistance × 100% was calculated. The above results are shown in Table 1 below.

[0025] Table 1. Insulation / thermal conductivity test results of epoxy resin composites

[0026] It can be seen from the results in Table 1 that the epoxy resin composite prepared by the present invention has excellent dielectric strength and resistance recovery effect, and can also be effectively used in high temperature and high pressure environments; from the results of Comparative Example 1 and Example 3, it can be seen that the lack of nano-SiO2 spraying on the fiber surface intensifies the concentration of the interfacial electric field, and the micro-nano anchoring effect disappears, which may lead to an increase in the risk of partial discharge. In addition, the lack of nano-SiO2 on the fiber surface enhances the interfacial moisture absorption, and the electric field concentration accelerates the moisture penetration, thereby significantly affecting the resistance recovery; from the results of Comparative Example 2 and Example 3, it can be seen that the high proportion of nano-SiO2 may lead to moisture absorption and agglomeration, intensify the interfacial stress concentration, and easily form a conductive channel. Moreover, after the removal of the polyurethane microspheres, the stress buffer disappears, and the hygrothermal expansion and cracking are aggravated, thereby significantly decreasing the insulation resistance recovery rate; from the results of Comparative Example 3 and Example 3, it can be seen that the failure of staged curing leads to the accumulation of internal stress and the increase of microcracks. The internal stress microcracks provide a moisture absorption path, but the filler system still partially blocks the moisture diffusion, and the insulation resistance recovery rate decreases to a certain extent; from the results of Comparative Example 4 and Example 3, it can be seen that the lack of microcapsules makes the moisture absorption microcracks unable to self-repair, but nano-SiO2 and Al2O3 still inhibit the moisture absorption effect to a certain extent. Insulation test: The volume resistivity of the epoxy resin composite samples prepared in Example 3 and Comparative Examples 1-4 was tested according to the standard GB / T 10582-2008. The epoxy resin composite samples prepared in Example 3 and Comparative Examples 1-4 were treated at 45 °C / 85% humidity for 48 h, and then the surface resistivity of the epoxy resin composite samples prepared in Example 3 and Comparative Examples 1-4 was tested according to the standard IEC 60093. The results are shown in Table 2 below.

[0027] Table 2. Insulation test results of epoxy resin composites

[0028] As can be seen from the results in Table 2, the epoxy resin composite prepared by the present invention has excellent insulation performance, and excellent insulation effect is achieved through the addition of multiple components and reasonable proportioning; from the results of Comparative Example 1 and Example 3, it can be seen that the interfacial bonding force of the glass fiber without spraying nano-SiO2 decreases, and the electric field concentration leads to the risk of partial discharge; from the results of Comparative Example 2 and Example 3, it can be seen that the lack of polyurethane microspheres leads to interfacial air gaps, and the increase in the amount of nano-SiO2 used may lead to uneven dispersion of fillers, thus causing agglomeration to form leakage paths; from the results of Comparative Example 3 and Example 3, it can be seen that curing only with dicyandiamide may lead to the expansion of microcracks. Although the filler system still maintains partial insulation, the lack of a polythiol flexible network causes leakage conduction after the surface microcracks absorb moisture.

[0029] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. An epoxy resin composite insulating material, characterized in that: The composition includes the following components by weight: 60-70 parts of epoxy resin, 10-12 parts of acetone, 12-15 parts of modified glass fiber, 1-2 parts of nano-SiO2, 5-8 parts of polyurethane microspheres, 10-12 parts of micron Al2O3, 2-3 parts of epoxy monomer microcapsules, 8-10 parts of curing agent and 3-5 parts of modifier; The specific preparation steps of the modified glass fiber are as follows: S1: adding γ-aminopropyltriethoxysilane to an ethanol solution, adjusting the pH with acetic acid, stirring and mixing to obtain a hydrolyzate; immersing the glass fiber in an acetone / ethanol mixture, ultrasonically treating, and drying to obtain a pretreated glass fiber; S2: adding the pretreated glass fiber prepared in step S1 into the hydrolyzate, increasing the temperature, performing an immersion treatment, pre-drying, and then heating and curing to obtain silane glass fiber; S3: dispersing nano-SiO2 in anhydrous ethanol, ultrasonically treating, and obtaining a sol; electrostatically spraying the sol onto the silane glass fiber prepared in step S2, and performing heat treatment at a high temperature to obtain a modified glass fiber.

2. The epoxy resin composite insulating material according to claim 1, characterized in that: In step S1, the ratio of the amount of γ-aminopropyltriethoxysilane to the ethanol solution is 2-3 g:100 mL; in step S2, the ratio of the amount of the pretreated glass fiber to the hydrolyzate is 1 g:3-5 mL.

3. The epoxy resin composite insulating material according to claim 2, characterized in that: In step S3, the ratio of nano-SiO2 to anhydrous ethanol is 2-3 g:100 mL; the electrostatic spraying operation is a spraying rate of 0.5-1 mL / min, a fiber transmission speed of 0.5 m / min, a voltage of 30 kV, a spray gun distance of 20-25 cm, and the spraying is repeated 2-3 times.

4. The epoxy resin composite insulating material according to claim 3, characterized in that: The curing agent is composed of ultrafine modified dicyandiamide and polythiol in a mass ratio of 7-8:2-3.

5. The epoxy resin composite insulating material according to claim 4, characterized in that: The modifier is any one of 3-glycidyloxypropyltriethoxysilane, 3-glycidyloxypropylmethyldiethoxysilane and 3-glycidyloxypropyltrimethoxysilane.

6. The epoxy resin composite insulating material according to claim 5, characterized in that: The specific preparation steps of the epoxy monomer microcapsules are as follows: S101: Add bisphenol A diglycidyl ether and sodium dodecyl sulfate into deionized water, stir, then add hexamethylene diisocyanate and ethylenediamine, increase the temperature, stir, vacuum filter, repeatedly wash with ethanol and deionized water, and vacuum dry to obtain epoxy monomer microcapsules.

7. The epoxy resin composite insulating material according to claim 6, characterized in that: In step S101, the ratio of the amount of bisphenol A diglycidyl ether, sodium lauryl sulfate and deionized water is 1g:0.15-0.2g:10mL; the mass ratio of the amount of bisphenol A diglycidyl ether, hexamethylene diisocyanate and ethylenediamine is 1:0.4-1:0.3-0.

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8. A method for preparing the epoxy resin composite insulating material according to any one of claims 1 to 7, characterized in that: The specific preparation steps are as follows: S201: adding a modifier to ethanol, adjusting the pH with acetic acid, increasing the temperature, stirring, and obtaining a modified hydrolyzate; immersing the polyurethane microspheres in the modified hydrolyzate, ultrasonically treating, centrifuging, repeatedly washing with ethanol, and vacuum drying to obtain grafted polyurethane microspheres; S202: mixing epoxy resin and acetone, raising the temperature, stirring, then adding nano-SiO2, ultrasonically dispersing them evenly, adding micron-Al2O3, stirring, then sequentially adding the grafted polyurethane microspheres prepared in step S201 and epoxy monomer microcapsules, stirring, and obtaining an epoxy resin matrix; S203: adding a curing agent and modified glass fiber to the epoxy resin matrix prepared in step S202, performing vacuum degassing, and then curing at 60° C. for 1 to 1.5 h, heating to 120° C. at a rate of 5° C. / min for curing for 1.5 to 2 h, and then heating to 150° C. at a rate of 5° C. / min for curing for 1 to 1.5 h to obtain an epoxy resin composite insulating material; In step S201, the ultrasonic treatment parameters are temperature 50°C, 200-300W, 40kHz, and time 40-60min; In step S202, the ultrasonic treatment parameters are 150-200W, 40kHz, and time 20-30min.

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