Epoxy resin composite insulating material and preparation method thereof

Abstract

The present application belongs to the technical field of polymer insulating material, and particularly relates to an epoxy resin composite insulating material and a preparation method thereof. The composition 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 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 present application effectively reduces the material cost under the premise of ensuring the insulating strength, thermal conductivity and mechanical properties, wherein the micron Al2O3 and nano-SiO2 are compounded to reduce the influence of high-viscosity nano-filler on the processing fluidity; the nano-SiO2 is directionally deposited on the surface of the fiber through electrostatic spraying, and a local high-concentration nano-phase is formed in the interface area, thereby replacing the traditional high-proportion nano-SiO2 addition requirement, effectively reducing the total nano-material consumption, and significantly reducing the cost.

Description

Technical Field

[0001] This invention belongs to the field of polymer insulating materials technology, specifically relating to an epoxy resin composite insulating material and its preparation method. Background Technology

[0002] Epoxy resin is a thermosetting polymer synthesized from epoxy groups (through the condensation reaction of epichlorohydrin and bisphenol A). Since its industrialization in the 1940s, it has become the core matrix of insulating materials due to its excellent adhesion, chemical resistance, mechanical strength, and electrical insulation properties. 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. Multi-scale reinforcement systems are constructed through composite functional fillers: for example, inorganic fillers SiO2 and Al2O3 improve heat resistance and mechanical strength; glass fibers in fiber reinforcement 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 insulation materials are widely used in high-voltage power equipment, such as insulators, GIS (gas-insulated switchgear), and transformer bushings; integrated circuit packaging and LED heat dissipation substrates in electronic packaging; stator insulation for wind turbines and electric vehicle motor insulation systems in the new energy field; and high-voltage cable insulation and high-temperature resistant components in aerospace. Current material performance improvements face a dual technical bottleneck: While traditional reinforcement techniques, such as glass fiber / mica sheet reinforcement, can improve mechanical strength and arc resistance, there is a risk of delamination failure due to weak resin-fiber interfacial bonding. Furthermore, high filler content may lead to deterioration of processing fluidity, a significant decrease in melt flow index, and stress accumulation during curing that induces microcracks. Nano-modification techniques using nano-SiO2 / BN can significantly improve dielectric strength and thermal conductivity, but the tendency for nanoparticle agglomeration may cause localized defects. Coupled with high raw material costs, this severely restricts large-scale application. The core contradictions currently facing epoxy resin composite insulation materials are primarily the contradiction between performance and processability (e.g., high filler content improves performance but impairs processability) and the contradiction between cost and performance (e.g., nano-modification has significant effects but poor economic efficiency). Therefore, based on the above problems, it is extremely necessary to develop a high-performance, low-cost composite epoxy resin insulation material through reasonable raw material matching and process integration. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the purpose of this invention is to provide an epoxy resin composite insulating material and its preparation method.

[0005] The technical effects described in this invention are achieved through the following technical solution: an epoxy resin composite insulating material, comprising the following components by weight: 60-70 parts epoxy resin, 10-12 parts acetone, 12-15 parts modified glass fiber, 1-2 parts nano-SiO2, 5-8 parts polyurethane microspheres, 10-12 parts micron-sized Al2O3, 2-3 parts epoxy monomer microcapsules, 8-10 parts curing agent, and 3-5 parts modifier.

[0006] Preferably, the curing agent is composed of ultrafine modified dicyandiamide and polythiol in a mass ratio of 7-8:2-3;

[0007] Preferably, the modifier is any one of 3-glycidyloxypropyltriethoxysilane, 3-glycidyloxypropylmethyldiethoxysilane, and 3-glycidyloxypropyltrimethoxysilane, and more preferably 3-glycidyloxypropyltriethoxysilane.

[0008] Preferably, the specific preparation steps of the modified glass fiber are as follows:

[0009] S1: Add γ-aminopropyltriethoxysilane to a 95wt% ethanol solution, adjust the pH to 4-5 with acetic acid, stir and mix at 500rpm for 30-50min to obtain a hydrolysate; immerse glass fiber in a 1:1 mixture of acetone and ethanol, sonicate at 60W for 30min, and dry at 120℃ for 2h to obtain pretreated glass fiber;

[0010] S2: Add the pretreated glass fiber prepared in step S1 to the hydrolysate, immerse at 40-50℃ for 15-30 min, pre-dry at 80℃ for 30 min, and then heat to 120℃ to cure for 1-2 h to obtain silane glass fiber.

[0011] S3: Disperse nano-SiO2 in anhydrous ethanol and sonicate at 300W and 40kHz for 50-60 min to obtain a sol; electrostatically spray the sol onto the silane glass fiber prepared in step S2 and heat treat at 120℃ for 40-60 min to obtain modified glass fiber.

[0012] Preferably, in step S1, the ratio of the amount of γ-aminopropyltriethoxysilane to the ethanol solution is 2-3 g: 100 mL.

[0013] Preferably, in step S2, the ratio of the amount of pretreated glass fiber to hydrolysate is 1g:3-5mL;

[0014] Preferably, in step S3, the ratio of nano-SiO2 to anhydrous ethanol is 2-3 g: 100 mL; the electrostatic spraying operation is as follows: spraying rate 0.5-1 mL / min, fiber conveying speed 0.5 m / min, voltage 30 kV, spray gun distance 20-25 cm, and repeated spraying 2-3 times.

[0015] Preferably, the specific preparation steps of the epoxy monomer microcapsules are as follows:

[0016] S101: Bisphenol A diglycidyl ether and sodium dodecyl sulfate were added to deionized water and stirred at 2000-3000 rpm for 10-15 min. Then hexamethylene diisocyanate and ethylenediamine were added and stirred at 300 rpm for 2-3 h at 40-50 °C. The mixture was then vacuum filtered, washed three times with ethanol and deionized water, and vacuum dried at 40 °C for 24 h to obtain epoxy monomer microcapsules.

[0017] Preferably, in step S101, the ratio of the amount of bisphenol A diglycidyl ether, sodium dodecyl 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 1:0.4-1:0.3-0.5.

[0018] Preferably, another aspect of the present invention provides a method for preparing an epoxy resin composite insulating material, the specific preparation steps of which are as follows:

[0019] S201: Add the modifier to 50 parts by weight of 90wt% ethanol, adjust the pH to 4-5 with acetic acid, stir at 500 rpm for 30-50 min at 40℃ to obtain the modified hydrolysate; immerse the polyurethane microspheres in the modified hydrolysate, sonicate, centrifuge, wash three times with ethanol, and vacuum dry at 60℃ for 12 h to obtain the grafted polyurethane microspheres.

[0020] S202: Mix epoxy resin and acetone at 35-40℃ and stir at 300 rpm for 10-20 min. Then add nano-SiO2 and ultrasonically disperse it evenly. Add micron-sized Al2O3 and stir at 500 rpm for 20-30 min. Then add the grafted polyurethane microspheres and epoxy monomer microcapsules prepared in step S201 in sequence and stir at 200 rpm for 15-20 min to obtain the epoxy resin matrix.

[0021] S203: Add the curing agent and modified glass fiber to the epoxy resin matrix prepared in step S202, vacuum degassing for 30-60 min, then cure at 60℃ for 1-1.5 h, then heat to 120℃ at a rate of 5℃ / min for 1.5-2 h, and finally heat to 150℃ at a rate of 5℃ / min for 1-1.5 h to obtain epoxy resin composite insulation material;

[0022] Preferably, in step S201, the ultrasonic treatment parameters are: temperature 50°C, 200-300W, 40kHz, and time 40-60min.

[0023] Preferably, in step S202, the ultrasonic processing parameters are 150-200W, 40kHz, and 20-30min.

[0024] The beneficial effects of this invention are as follows:

[0025] This invention utilizes γ-aminopropyltriethoxysilane (KH550) graft-modified glass fiber. The modified surface amino groups (-NH2) form covalent bonds with the epoxy groups of the epoxy resin, enhancing the interfacial chemical bonding. Then, nano-SiO2 is loaded onto the fiber surface by electrostatic spraying to construct a micro-nano rough structure. This mechanical anchoring effect suppresses interfacial slippage and reduces the risk of delamination. The nano-SiO2 layer on the fiber surface has a high dielectric constant, which can disperse the concentration of interfacial electric field and suppress partial discharge. At the same time, the hydroxyl groups on the SiO2 surface match the polarity of the resin, reducing the accumulation of interfacial charge. After being modified with 3-glycidyl etheroxypropyltriethoxysilane (KH560), polyurethane microspheres form chemical bonds between their surface epoxy groups and the resin matrix, preventing phase separation. As elastic units, the microspheres induce crazing and absorb energy under external forces, significantly improving impact toughness. Their elastic deformation can offset the shrinkage stress of resin curing, reducing the initiation of microcracks. In addition, the dispersed distribution of microspheres can block crack propagation paths and form a rigid-flexible interpenetrating network with modified glass fibers, simultaneously improving tensile strength and fracture toughness. Uniformly dispersed nano-SiO2 slows down electrical tree growth and improves overall dielectric strength through interfacial polarization. Its small size effect can fill micro-defects in the resin matrix, suppressing partial discharge. Micron-sized Al2O3 forms a continuous thermally conductive framework, rapidly dissipating local heat and preventing insulation aging caused by temperature rise. It synergistically forms a multi-level thermally conductive network with nano-scale framework and nano-scale filler. In addition, the nano-SiO2 pre-loaded on the modified glass fiber surface can also serve as anchoring points, guiding the directional distribution of SiO2 fillers directly added to the matrix, reducing the risk of agglomeration and improving overall dispersion uniformity. The polyurea shell (HDI / ethylenediamine polymerization) has high mechanical strength and heat resistance, protecting the core material (bisphenol A diglycidyl ether) from being released during processing. When microcracks are generated inside the material, stress concentration at the crack tip causes the microcapsules to rupture, and the released epoxy monomers diffuse in the crack gaps, extending the material's lifespan. Polythiol triggers rapid pre-crosslinking at low temperature (60℃), forming a flexible network to buffer shrinkage stress; dicyandiamide completes deep crosslinking under high temperature, ensuring high crosslinking density and heat resistance; staged curing releases the resin shrinkage gradient, effectively reducing internal stress and preventing curing cracking.

[0026] In summary, this invention effectively reduces material costs while ensuring insulation strength, thermal conductivity, and mechanical properties. Specifically, it employs a blend of micron-sized Al2O3 and nano-sized SiO2, utilizing the skeletal support of the micron-sized filler to reduce the impact of high-viscosity nanofillers on processing flowability. Modified glass fibers, through aminosilane grafting and nano-SiO2 spraying, enhance the interfacial bonding between the monofilament and resin, reducing the fiber content and minimizing resistance to resin flowability. Furthermore, the nano-SiO2 sprayed onto the fiber surface is deposited directionally via electrostatic spraying, forming a locally high-concentration nanophase in the interfacial region, replacing the traditional requirement of adding a high proportion of nano-SiO2 to the matrix. This effectively reduces the total amount of nanomaterials used, significantly lowering costs. The introduction of KH560 modified polyurethane microspheres compensates for the decrease in toughness caused by the reduction in nanofillers through the elastomer toughening effect, avoiding reliance on high-cost toughening agents such as carbon nanotubes. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only for this invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 The graph shows the mechanical strength test results of the epoxy resin composite material samples prepared in Examples 1-3 and Comparative Examples 1-4 of this invention. Detailed Implementation

[0029] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within 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 all purchased through conventional commercial channels.

[0030] Example 1: An epoxy resin composite insulating material, comprising the following components by weight: 70 parts epoxy resin, 10 parts acetone, 12 parts modified glass fiber, 1 part nano SiO2, 5 parts polyurethane microspheres, 10 parts micron Al2O3, 2 parts epoxy monomer microcapsules, 8 parts curing agent and 3 parts modifier.

[0031] 1. The specific preparation steps of modified glass fiber are as follows:

[0032] S1: Add 2g of γ-aminopropyltriethoxysilane to 100mL of 95wt% ethanol solution, adjust the pH to 4 with acetic acid, stir and mix at 500rpm for 30min to obtain hydrolysate; immerse 10g of glass fiber in 100mL of a mixture of acetone and ethanol in a 1:1 ratio, sonicate at 60W for 30min, and dry at 120℃ for 2h to obtain pretreated glass fiber;

[0033] S2: Add 10g of pretreated glass fiber prepared in step S1 to 30mL of hydrolysate, immerse at 40℃ for 15min, pre-dry at 80℃ for 30min, and then heat to 120℃ for 1h to obtain silane glass fiber.

[0034] S3: Disperse 2g of nano-SiO2 in 100mL of anhydrous ethanol and sonicate at 300W and 40kHz for 50min to obtain a sol; electrostatically spray the sol onto the silane glass fiber prepared in step S2 at a spraying rate of 0.5mL / min, a fiber conveying speed of 0.5m / min, a voltage of 30kV, and a spray gun distance of 20cm, repeating the spraying twice; then heat-treat at 120℃ for 40min to obtain modified glass fiber;

[0035] 2. The specific preparation steps of epoxy monomer microcapsules are as follows:

[0036] S101: Add 10g of bisphenol A diglycidyl ether and 1.5g of sodium dodecyl sulfate to 100mL of deionized water, stir at 2000rpm for 10min, then add 4g of hexamethylene diisocyanate and 3g of ethylenediamine, stir at 300rpm for 2h at 40℃, vacuum filter, wash three times with ethanol and deionized water, and vacuum dry at 40℃ for 24h to obtain epoxy monomer microcapsules;

[0037] 3. The specific preparation steps for epoxy resin composite insulation materials are as follows:

[0038] S201: 3-glycidyl etheroxypropylmethyldiethoxysilane was added to 50 parts by weight of 90wt% ethanol, the pH was adjusted to 4 with acetic acid, and the mixture was stirred at 500 rpm for 30 min at 40℃ to obtain a modified hydrolysate. Polyurethane microspheres were immersed in the modified hydrolysate and sonicated at 50℃, 200W, 40kHz for 40 min. After centrifugation, the microspheres were washed three times with ethanol and dried under vacuum at 60℃ for 12 h to obtain grafted polyurethane microspheres.

[0039] S202: Mix epoxy resin and acetone at 35°C and stir at 300 rpm for 10 min. Then add nano-SiO2 and sonicate at 150 W, 40 kHz for 20 min. Add micron-sized Al2O3 and stir at 500 rpm for 20 min. Then add the grafted polyurethane microspheres and epoxy monomer microcapsules prepared in step S201 in sequence and stir at 200 rpm for 15 min to obtain epoxy resin matrix.

[0040] S203: Add the curing agent composed of ultrafine modified dicyandiamide and polythiol in a mass ratio of 7:3 and modified glass fiber to the epoxy resin matrix prepared in step S202, vacuum degassing for 30 min, then curing at 60℃ for 1 h, then heating to 120℃ at a rate of 5℃ / min for 1.5 h, and finally heating to 150℃ at a rate of 5℃ / min for 1 h to obtain epoxy resin composite insulation material.

[0041] Example 2: An epoxy resin composite insulating material, comprising the following components by weight: 70 parts epoxy resin, 11 parts acetone, 15 parts modified glass fiber, 1.5 parts nano SiO2, 6 parts polyurethane microspheres, 11 parts micron Al2O3, 2.5 parts epoxy monomer microcapsules, 9 parts curing agent and 4 parts modifier.

[0042] 1. The specific preparation steps of modified glass fiber are as follows:

[0043] S1: Add 2.5g of γ-aminopropyltriethoxysilane to 100mL of 95wt% ethanol solution, adjust the pH to 5 with acetic acid, stir and mix at 500rpm for 40min to obtain hydrolysate; immerse 10g of glass fiber in 100mL of a mixture of acetone and ethanol in a 1:1 ratio, sonicate at 60W for 30min, and dry at 120℃ for 2h to obtain pretreated glass fiber;

[0044] S2: Add 10g of pretreated glass fiber prepared in step S1 to 40mL of hydrolysate, immerse at 45℃ for 30min, pre-dry at 80℃ for 30min, and then heat to 120℃ for 1.5h to obtain silane glass fiber.

[0045] S3: Disperse 2.5g of nano-SiO2 in 100mL of anhydrous ethanol and sonicate at 300W and 40kHz for 55min to obtain a sol; electrostatically spray the sol onto the silane glass fiber prepared in step S2 at a spraying rate of 0.8mL / min, a fiber conveying speed of 0.5m / min, a voltage of 30kV, and a spray gun distance of 22cm, repeating the spraying 3 times; then heat-treat at 120℃ for 50min to obtain modified glass fiber;

[0046] 2. The specific preparation steps of epoxy monomer microcapsules are as follows:

[0047] S101: Add 10g of bisphenol A diglycidyl ether and 1.8g of sodium dodecyl sulfate to deionized water, stir at 2500rpm for 14min, then add 8g of hexamethylene diisocyanate and 4g of ethylenediamine, stir at 300rpm for 2.5h at 45℃, vacuum filter, wash three times with ethanol and deionized water, and vacuum dry at 40℃ for 24h to obtain epoxy monomer microcapsules;

[0048] 3. The specific preparation steps for epoxy resin composite insulation materials are as follows:

[0049] S201: 3-glycidoxypropyltrimethoxysilane was added to 50 parts by weight of 90wt% ethanol, the pH was adjusted to 5 with acetic acid, and the mixture was stirred at 500 rpm for 40 min at 40℃ to obtain a modified hydrolysate. Polyurethane microspheres were immersed in the modified hydrolysate and sonicated at 50℃, 250W, 40kHz for 50 min. After centrifugation, the microspheres were washed three times with ethanol and dried under vacuum at 60℃ for 12 h to obtain grafted polyurethane microspheres.

[0050] S202: Mix epoxy resin and acetone at 38℃ and stir at 300 rpm for 15 min. Then add nano SiO2 and sonicate at 180 W, 40 kHz for 25 min. Add micron Al2O3 and stir at 500 rpm for 25 min. Then add the grafted polyurethane microspheres and epoxy monomer microcapsules prepared in step S201 in sequence and stir at 200 rpm for 18 min to obtain epoxy resin matrix.

[0051] S203: Add the 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. Vacuum degassing treatment for 50 min, then curing treatment at 60℃ for 1.2 h, heating to 120℃ at a rate of 5℃ / min for 1.8 h, and then heating to 150℃ at a rate of 5℃ / min for 1.2 h to obtain epoxy resin composite insulation material.

[0052] Example 3: An epoxy resin composite insulating material, comprising the following components by weight: 65 parts epoxy resin, 12 parts acetone, 14 parts modified glass fiber, 2 parts nano SiO2, 8 parts polyurethane microspheres, 12 parts micron Al2O3, 3 parts epoxy monomer microcapsules, 10 parts curing agent and 5 parts modifier.

[0053] 1. The specific preparation steps of modified glass fiber are as follows:

[0054] S1: Add 3g of γ-aminopropyltriethoxysilane to 100mL of 95wt% ethanol solution, adjust the pH to 4.5 with acetic acid, stir and mix at 500rpm for 50min to obtain hydrolysate; immerse 10g of glass fiber in 100mL of a mixture of acetone and ethanol in a 1:1 ratio, sonicate at 60W for 30min, and dry at 120℃ for 2h to obtain pretreated glass fiber;

[0055] S2: Add 10g of pretreated glass fiber prepared in step S1 to 50mL of hydrolysate, immerse at 50℃ for 25min, pre-dry at 80℃ for 30min, and then heat to 120℃ for 2h to obtain silane glass fiber.

[0056] S3: Disperse 3g of nano-SiO2 in 100mL of anhydrous ethanol and sonicate at 300W and 40kHz for 60min to obtain a sol; electrostatically spray the sol onto the silane glass fiber prepared in step S2 at a spraying rate of 1mL / min, a fiber conveying speed of 0.5m / min, a voltage of 30kV, and a spray gun distance of 25cm, repeating the spraying 3 times; then heat-treat at 120℃ for 60min to obtain modified glass fiber;

[0057] 2. The specific preparation steps of epoxy monomer microcapsules are as follows:

[0058] S101: Add 10g of bisphenol A diglycidyl ether and 2g of sodium dodecyl sulfate to 100mL of deionized water, stir at 3000rpm for 15min, then add 10g of hexamethylene diisocyanate and 5g of ethylenediamine, stir at 300rpm for 3h at 50℃, vacuum filter, wash three times with ethanol and deionized water, and vacuum dry at 40℃ for 24h to obtain epoxy monomer microcapsules;

[0059] 3. The specific preparation steps for epoxy resin composite insulation materials are as follows:

[0060] S201: 3-glycidyl etheroxypropyltriethoxysilane was added to 50 parts by weight of 90 wt% ethanol, the pH was adjusted to 4.5 with acetic acid, and the mixture was stirred at 500 rpm for 50 min at 40℃ to obtain a modified hydrolysate. Polyurethane microspheres were immersed in the modified hydrolysate and sonicated at 50℃, 300 W, 40 kHz for 60 min. After centrifugation, the microspheres were washed three times with ethanol and dried under vacuum at 60℃ for 12 h to obtain grafted polyurethane microspheres.

[0061] S202: Mix epoxy resin and acetone at 40℃ and stir at 300 rpm for 20 min. Then add nano SiO2 and sonicate at 200 W, 40 kHz for 30 min. Add micron Al2O3 and stir at 500 rpm for 30 min. Then add the grafted polyurethane microspheres and epoxy monomer microcapsules prepared in step S201 in sequence and stir at 200 rpm for 20 min to obtain epoxy resin matrix.

[0062] S203: Add the 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, vacuum degassing for 60 min, then curing at 60℃ for 1.5 h, then heating to 120℃ at a rate of 5℃ / min for 2 h, and finally heating to 150℃ at a rate of 5℃ / min for 1.5 h to obtain epoxy resin composite insulation material.

[0063] Comparative Example 1: This comparative example provides an epoxy resin composite insulation material, which is basically the same as the operation of Example 3, except that the glass fiber is not treated with nano-SiO2 spraying in Comparative Example 1.

[0064] Comparative Example 2: This comparative example provides an epoxy resin composite insulation material, which is basically the same as the operation of Example 3. The difference is that no polyurethane microspheres and modifiers are added in Comparative Example 2, and the amount of nano SiO2 is increased to 8 parts.

[0065] Comparative Example 3: This comparative example provides an epoxy resin composite insulation material, which is basically the same as the one used in Example 3, except that only dicyandiamide is used as a curing agent in Comparative Example 3.

[0066] Comparative Example 4: This comparative example provides an epoxy resin composite insulation material, which is basically the same as the operation of Example 3, except that epoxy monomer microcapsules are not added in Comparative Example 4.

[0067] Performance testing:

[0068] Mechanical strength testing: The interfacial shear strength of the epoxy resin composite samples prepared in Examples 1-3 and Comparative Examples 1-4 was tested using a universal testing machine according to ASTM D1002. The impact strength of the epoxy resin composite samples prepared in Example 3 and Comparative Examples 1-4 was tested using a pendulum impact tester according to GB / T 2567-2021. The test results are as follows: Figure 1 As shown.

[0069] Depend on Figure 1The results show that the epoxy resin composite material prepared by this invention has excellent mechanical strength and can effectively adapt to various high-strength application scenarios, especially the sample prepared according to the ratio in Example 3. The results of Comparative Example 1 and Example 3 show that the mechanical anchoring effect and interfacial electric field dispersion function of the sprayed nano-SiO2 are lacking. Although the chemical bonding of the silane coupling agent still exists, the interfacial bonding strength is affected to some extent by the lack of physical anchoring. The decreased interfacial bonding force makes cracks more likely to propagate along the fiber-resin interface, leading to a significant decrease in mechanical strength. The results of Comparative Example 2 and Example 3 show that the elastic stress buffering and chemical bonding of the polyurethane microspheres are lacking due to the KH560 modification, resulting in increased interfacial stress concentration. The increased proportion of nano-SiO2 may have led to the formation of clusters. Aggregation weakens the uniformity of dispersion and instead forms interfacial defects. In addition, the toughening mechanism of elastic microspheres completely disappears, the impact energy absorption capacity decreases significantly, the increased proportion of nano-SiO2 leads to increased matrix brittleness, reduced crack propagation resistance, and thus a significant decrease in mechanical strength. As can be seen from the results of Comparative Example 3 and Example 3, due to the action of only one curing agent, staged curing failure may occur, and the residual stress at the interface may be present. In addition, although the high-temperature curing of dicyandiamide still ensures the crosslinking density, the microcracks caused by internal stress may weaken the interfacial bonding, thus leading to a significant decrease in mechanical strength. As can be seen from the results of Comparative Example 4 and Example 3, when the material is damaged by impact, it cannot release epoxy monomers to repair cracks, the crack propagation rate may be slightly faster than in Example 3, and its impact strength is slightly affected.

[0070] 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 according to ASTM E1461; according to 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℃ / 95% humidity for 48h; after being removed, the surface moisture was wiped off, and the samples were allowed to recover in a standard environment of 23℃ / 50% humidity for 24h; the volume resistivity was measured using a high-resistivity meter, and the insulation resistance recovery rate (%) was calculated as: recovery resistance / initial resistance × 100%. The results are shown in Table 1 below.

[0071] Table 1. Insulation / thermal conductivity test results of epoxy resin composites

[0072]

[0073] As shown in Table 1, the epoxy resin composite material prepared by this invention exhibits excellent dielectric strength and resistance recovery, and can be effectively used even under high temperature and high pressure conditions. The results of Comparative Example 1 and Example 3 show that the absence of nano-SiO2 spraying on the fiber surface leads to increased interfacial electric field concentration and the disappearance of the micro-nano anchoring effect, potentially increasing the risk of partial discharge. Furthermore, the absence of nano-SiO2 on the fiber surface results in enhanced interfacial hygroscopicity, and the concentrated electric field accelerates moisture penetration, thus significantly affecting resistance recovery. The results of Comparative Example 2 and Example 3 indicate that a high proportion of nano-SiO2 may lead to hygroscopicity. Agglomeration exacerbates interfacial stress concentration and easily forms conductive channels. Furthermore, the removal of polyurethane microspheres eliminates stress buffering, intensifying hygrothermal expansion and cracking, leading to a significant decrease in insulation resistance recovery rate. Results from Comparative Example 3 and Example 3 show that staged curing failure results in internal stress accumulation and an increase in microcracks. These internal stress microcracks provide moisture absorption pathways, but the filler system still partially blocks moisture diffusion, resulting in a certain degree of decrease in insulation resistance recovery rate. Results from Comparative Example 4 and Example 3 show that the absence of microcapsules prevents the self-repair of moisture-absorbing microcracks, but nano-SiO2 and Al2O3 still effectively suppress the moisture absorption effect to a certain extent.

[0074] Insulation test: The volume resistivity of the epoxy resin composite material samples prepared in Example 3 and Comparative Examples 1-4 was tested according to standard GB / T 10582-2008. The epoxy resin composite material samples prepared in Example 3 and Comparative Examples 1-4 were treated at 45℃ / 85% humidity for 48h. Then the surface resistivity of the epoxy resin composite material samples prepared in Example 3 and Comparative Examples 1-4 was tested according to standard IEC 60093. The results are shown in Table 2 below.

[0075] Table 2. Insulation test results of epoxy resin composite materials

[0076]

[0077] As shown in Table 2, the epoxy resin composite material prepared by this invention has excellent insulation properties. The excellent insulation effect is achieved through the synergistic addition of multiple components and reasonable proportions. As shown in the results of Comparative Example 1 and Example 3, the interfacial bonding force of the glass fiber without nano-SiO2 coating decreases, and the electric field concentration leads to the risk of partial discharge. As shown in the results of Comparative Example 2 and Example 3, the lack of polyurethane microspheres leads to interfacial air gaps, and the increased amount of nano-SiO2 may lead to uneven dispersion of fillers, which in turn causes agglomeration and the formation of leakage paths. As shown in the results of Comparative Example 3 and Example 3, curing with dicyandiamide alone may lead to the propagation of microcracks. Although the filler system still maintains some insulation, the lack of polythiol flexible network leads to leakage after moisture absorption by surface microcracks.

[0078] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An epoxy resin composite insulating material, characterized in that, Its composition includes the following components by weight: 60-70 parts epoxy resin, 10-12 parts acetone, 12-15 parts modified glass fiber, 1-2 parts nano SiO2, 5-8 parts polyurethane microspheres, 10-12 parts micron Al2O3, 2-3 parts epoxy monomer microcapsules, 8-10 parts curing agent and 3-5 parts modifier; The specific preparation steps of the modified glass fiber are as follows: S1: Add γ-aminopropyltriethoxysilane to an ethanol solution, adjust the pH with acetic acid, stir and mix to obtain a hydrolysate; immerse glass fiber in an acetone / ethanol mixture, sonicate, and dry to obtain pretreated glass fiber; S2: Add the pretreated glass fiber prepared in step S1 to the hydrolysate, increase the temperature, impregnate, pre-dry, and then heat up to cure to obtain silane glass fiber; S3: Disperse nano-SiO2 in anhydrous ethanol, sonicate to obtain a sol; electrostatically spray the sol onto the silane glass fiber prepared in step S2, and heat-treat at a higher temperature to obtain modified glass fiber; In step S1, the ratio of γ-aminopropyltriethoxysilane to ethanol solution is 2-3 g: 100 mL; in step S2, the ratio of pretreated glass fiber to hydrolysate is 1 g: 3-5 mL. In step S3, the ratio of nano-SiO2 to anhydrous ethanol is 2-3 g: 100 mL; the electrostatic spraying operation is as follows: spraying rate 0.5-1 mL / min, fiber conveying speed 0.5 m / min, voltage 30 kV, spray gun distance 20-25 cm, and repeated spraying 2-3 times. The curing agent is composed of ultrafine modified dicyandiamide and polythiol in a mass ratio of 7-8:2-3; The modifier is any one of 3-glycidyloxypropyltriethoxysilane, 3-glycidyloxypropylmethyldiethoxysilane, and 3-glycidyloxypropyltrimethoxysilane. The specific preparation steps of the epoxy monomer microcapsules are as follows: S101: Bisphenol A diglycidyl ether and sodium dodecyl sulfate were added to deionized water and stirred. Then hexamethylene diisocyanate and ethylenediamine were added, the temperature was increased, and the mixture was stirred. The mixture was then vacuum filtered, washed repeatedly with ethanol and deionized water, and dried under vacuum to obtain epoxy monomer microcapsules. The ratio of bisphenol A diglycidyl ether, sodium dodecyl sulfate, and deionized water is 1 g: 0.15–0.2 g: 10 mL; the mass ratio of bisphenol A diglycidyl ether, hexamethylene diisocyanate, and ethylenediamine is 1:0.4–1:0.3–0.

5. The preparation steps of the epoxy resin composite insulating material are as follows: S201: Add the modifier to ethanol, adjust the pH with acetic acid, increase the temperature, and stir to obtain a modified hydrolysate; immerse polyurethane microspheres in the modified hydrolysate, sonicate, centrifuge, wash repeatedly with ethanol, and vacuum dry to obtain grafted polyurethane microspheres. S202: Mix epoxy resin and acetone, increase the temperature, stir, then add nano-SiO2, ultrasonically disperse evenly, add micron-sized Al2O3, stir, then add the grafted polyurethane microspheres and epoxy monomer microcapsules prepared in step S201 in sequence, stir to obtain epoxy resin matrix. S203: Add the curing agent and modified glass fiber to the epoxy resin matrix prepared in step S202, perform vacuum degassing treatment, then cure at 60℃ for 1 to 1.5 h, then heat to 120℃ at a rate of 5℃ / min for 1.5 to 2 h, and finally heat to 150℃ at a rate of 5℃ / min for 1 to 1.5 h to obtain epoxy resin composite insulation material; In step S201, the ultrasonic treatment parameters are: temperature 50℃, 200~300W, 40kHz, and time 40~60min; In step S202, the ultrasonic processing parameters are 150-200W, 40kHz, and 20-30min.

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