Corona-resistant mica / aramid fiber composite material for new energy vehicles and its manufacturing method

Abstract

A corona-resistant mica / aramid fiber composite material for new energy vehicles and a manufacturing method thereof are provided. The manufacturing raw materials include a modified aramid fiber material, an adhesive, and a modified mica material. The modified mica material includes mica powder, hydrochloric acid solution, ethanol, a silane coupling agent, methyl methacrylate, an initiator, and toluene. The mica powder is composed of a first mica powder, a second mica powder, and a third mica powder, the first mica powder having a particle size of 90-110 μm, the second mica powder having a particle size of 130-150 μm, and the third mica powder having a particle size of 200-230 μm, and the weight ratio of the first mica powder to the second mica powder to the third mica powder is 1:(3-5):(3-5), respectively. By compounding the modified aramid fiber material and the modified mica material with the above adhesive, the overall density, paper insertion processability, corona resistance, PDIV and heat resistance level of the composite material can be improved, and the material can significantly improve the electrical insulation properties of the motor of a new energy vehicle and significantly extend the long-term safe operating life.

Description

[Technical Field]

[0001] This application claims priority from a Chinese patent application filed on October 20, 2022, with application number 202211286443.2, entitled "Corona-resistant mica / aramid fiber composite material for new energy vehicles and manufacturing method thereof," and from a Chinese patent application filed on October 20, 2022, with application number 202211286451.7, entitled "Corona-resistant mica / aramid fiber blended paper for new energy vehicles and manufacturing method thereof," the entire contents of which are incorporated herein by reference.

[0002] The present application relates to the field of insulating materials, in particular the technical field of mica composite materials, more particularly to a corona-resistant mica / aramid fiber composite material for new energy vehicles and a manufacturing method thereof. [Background technology]

[0003] The existing slot insulation paper and interphase insulation paper with high-temperature resistance grade H or above used in the motors of new energy vehicles are mostly made of pure aramid fiber paper or a composite of aramid fiber paper and polyimide film with a high-temperature resistant adhesive. A typical composite paper structure is Nomex fiber paper / PI film / Nomex fiber paper (NHN), and the composite adhesive is mostly an epoxy, polyurethane, or polyacrylate adhesive.

[0004] Pure aramid fiber paper or NHN composite paper has relatively high heat resistance and performs very well when used in the insulation structure of 400V voltage platform motors for new energy vehicles. However, for 800V voltage platform motors, due to high voltage levels, pulse width modulation peak voltages, and environmental factors, the maximum safe voltage can reach 2300V or more, which is much higher than the partial discharge inception voltage (PDIV) of existing insulating materials for conventional low-voltage motors. This increases the likelihood of partial discharges occurring during motor operation. Therefore, for automotive motors on 800V voltage platforms, the corona resistance of insulating materials must be considered.

[0005] In conventional technologies, the corona resistance life of composite paper has been extended by adding mica components to organic aramid fiber paper, or by combining epoxy, aramid fiber paper, and mica paper with polyurethane or polyacrylate adhesives. However, the mica-containing composite paper produced by these two methods generally has problems such as easy powder shedding, cracking, and layer peeling, and its corona resistance and high-temperature resistance are average, and it cannot meet the process requirements for large-scale application in the motors of new energy vehicles. Summary of the Invention [Problem to be solved by the invention]

[0006] To address these issues, we provide a corona-resistant mica / aramid fiber composite material for new energy vehicles and a manufacturing method for the same. This application provides modified mica and aramid fiber materials with excellent corona resistance. The modified aramid fiber and mica materials are hot-pressed or mixed together with adhesives that have high temperature resistance and low dielectric constants, such as PFA-tetrafluoroethylene-perfluoroalkoxyvinyl ether copolymer, FEP-fluorinated ethylene propylene copolymer (F46, tetrafluoroethylene-hexafluoropropylene copolymer), ETFE-ethylene-tetrafluoroethylene copolymer, PEEK-polyether ether ketone, and PEI-polyetherimide, to form a composite. This improves the overall density, paper insertion processability, corona resistance, partial discharge inception voltage (PDIV), and heat resistance of the composite. When used as slot-bottom insulating paper or interphase insulating paper, this material significantly improves the electrical insulation of new energy vehicle motors and significantly extends their long-term safe operating life. [Means for solving the problem]

[0007] According to one aspect of the present application, there is provided a corona-resistant mica / aramid fiber composite material for new energy vehicles, wherein raw materials for manufacturing the composite material include a modified aramid fiber material, an adhesive, and a modified mica material; the adhesive comprises one or more of tetrafluoroethylene-perfluoroalkoxyvinyl ether copolymer, fluorinated ethylene propylene copolymer, ethylene-tetrafluoroethylene copolymer, polyether ether ketone, and polyetherimide; The modified mica material is prepared from raw materials including mica powder, hydrochloric acid solution, ethanol, a silane coupling agent, methyl methacrylate, an initiator, and toluene; The mica powder comprises first, second, and third mica powders, the particle size of the first mica powder being 90-110 μm, the particle size of the second mica powder being 130-150 μm, and the particle size of the third mica powder being 200-230 μm, and the weight ratio of the first mica powder to the second mica powder to the third mica powder being 1:(3-5):(3-5), respectively.

[0008] Furthermore, the adhesive is FEP-fluorinated ethylene propylene copolymer (F46, tetrafluoroethylene-hexafluoropropylene copolymer), and further, the adhesive contains FEP-fluorinated ethylene propylene copolymer (F46, tetrafluoroethylene-hexafluoropropylene copolymer) and polyether ether ketone in a weight ratio of 3:1.

[0009] Specifically, the concentration of the hydrochloric acid solution is 2 mol / L.

[0010] Optionally, the weight ratio of the silane coupling agent to the mica powder is (0.05-0.08):1, the weight ratio of the mica powder, methyl methacrylate, and initiator is 1:(0.1-0.15):(0.002-0.005), respectively, and the weight ratio of the mica powder, ethanol, and toluene is 1:(6-8):(5-8), respectively.

[0011] Optionally, the method of making the modified mica material comprises: Step S11: adding a silane coupling agent to ethanol and adjusting the pH value to 4 using hydrochloric acid solution; Step S12: adding mica powder, heating to 60-80°C, stirring for 1-3 hours, filtering, washing, and drying; The method includes step S13 of adding the mixture to toluene, adding methyl methacrylate and an initiator, reacting at 70 to 90°C for 2 to 4 hours, filtering, and then drying at 110 to 130°C for 0.5 to 2 hours.

[0012] Specifically, the mass concentration of the slurry is 3 to 5%.

[0013] Optionally, the silane coupling agent is A171 and the initiator is benzoyl peroxide.

[0014] Optionally, the modified aramid fiber material is made of meta-aramid chopped fibers and meta-aramid fibrids, the lengths of the meta-aramid chopped fibers and meta-aramid fibrids are both 2 to 3 mm, and the weight ratio of the meta-aramid chopped fibers to the meta-aramid fibrids is 1:(2 to 2.5).

[0015] Optionally, the method for producing the modified aramid fiber material comprises: Step S21 of defibrating and dispersing the meta-aramid chopped fibers and meta-aramid fibrids to form pulp; and step S22 of ultrasonically treating the pulp. Specifically, the mass concentration of the pulp is 0.1 to 0.5%.

[0016] Optionally, the ultrasonic treatment step is performed for 10 seconds at 3-second intervals for a total of 6-9 minutes, with ultrasonic parameters of 10-20 kHz frequency and 500 W power.

[0017] Optionally, the modified aramid fiber material is a modified aramid paper and the modified mica material is a modified mica paper; The raw materials are 40-60 wt% modified aramid fiber paper, 5-20 wt% adhesive, and 40-60 wt% modified mica paper.

[0018] Optionally, the method for preparing the modified mica material further includes step S14 of adding water and stirring uniformly to form a slurry, which is then made into paper sheets by a paper sheet forming machine to obtain the modified mica paper.

[0019] Optionally, the method for producing the modified aramid fiber material further includes step S23 of forming the modified aramid fiber paper using a paper sheet forming machine.

[0020] Optionally, water is added in the "Step S21 of defibrating and dispersing the meta-aramid chopped fibers and meta-aramid fibrids to form pulp."

[0021] Optionally, the modified aramid fiber material is modified aramid fiber and the modified mica material is modified mica powder; The weight ratio of the modified aramid fibers to the modified mica powder is (0.1 to 0.5):1, and the amount of the adhesive added is 5 to 10% of the total weight of the modified aramid fibers and the modified mica powder.

[0022] According to another aspect of the present application, Step S01: unwinding two modified aramid fiber paper rolls and applying adhesive to their surfaces; Step S02: unwinding the modified mica paper, first laminating it to one piece of modified aramid fiber paper coated with adhesive, and then laminating another piece of modified aramid fiber paper coated with adhesive to the other side of the modified mica paper and drying; and step S03 of hot-pressing the dried composite material with a hot roller to finally obtain the corona-resistant mica / aramid fiber composite material for new energy vehicles.

[0023] According to a further aspect of the present application, Step S01: mixing modified mica powder with water to form a slurry with a mass concentration of 2 to 10%, and mixing modified aramid fiber with water to form a slurry with a mass concentration of 0.1 to 1%; Step S02: Mixing and uniformly stirring the modified mica powder slurry, the modified aramid fiber slurry, and the adhesive; and step S03 of feeding the mixed slurry into a paper sheet forming machine to form it, drying it after pressing, and further hot pressing it with a hot roller to finally obtain the corona-resistant mica / aramid fiber blended paper for new energy vehicles.

[0024] Optionally, the drying temperature is 120°C, the hot pressing temperature is 265-310°C, and the hot pressing pressure is 20 MPa. [Effects of the Invention]

[0025] The beneficial effects of the present application include, but are not limited to: 1. According to the corona-resistant mica / aramid fiber composite material for new energy vehicles of the present application, a modified aramid fiber material and a modified mica material are composited using an adhesive that has high temperature resistance and a low dielectric constant, such as PFA-tetrafluoroethylene-perfluoroalkoxyvinyl ether copolymer, FEP-fluorinated ethylene propylene copolymer (F46, tetrafluoroethylene-hexafluoropropylene copolymer), ETFE-ethylene-tetrafluoroethylene copolymer, PEEK-polyether ether ketone, or PEI-polyetherimide. By combining the modified mica material and the modified aramid fiber material, which have excellent corona resistance, the overall density, paper insertion processability, corona resistance, partial discharge inception voltage (PDIV), and heat resistance level of the composite material can be improved. 2. In the corona-resistant mica / aramid fiber composite material for new energy vehicles of the present application, the mica powder is limited to three types of mica powder with different particle sizes, and the proportions of each are specified. The large particle size mica powder has a perfect flake shape and plays an excellent stress transmission role, preventing the paper from breaking due to concentrated force and imparting a certain stiffness to the paper. The relatively small proportion of small particle size mica fills the spaces between the large mica flakes, imparting excellent strength properties to the paper and reducing the fracture effect between fibers, forming a "brick-and-mud" structure, which imparts excellent strength properties to the paper. Among them, the flake structure of the two types of mica powder with large particle diameters acts as "bricks" and provides more adhesion carriers for the fibrids. In addition, the two types of mica powder with large particle diameters are regularly arranged, which also gives the paper relatively good flatness. The diameter-to-thickness ratio is also large, which gives the flakes a high insulating effect in the Z direction and a high current-blocking effect, delaying the formation of current channels and effectively delaying the spread of arcs, reducing carbonization damage to fibers, reducing the size and area of ​​insulation breakdown points, and improving corona resistance. 3. In the corona-resistant mica / aramid fiber composite material for new energy vehicles, the mica material is modified with a combination of a silane coupling agent and a polymer monomer, and hydroxyl groups are introduced onto the surface of the mica powder. Silane coupling agent A171 is used to introduce double bonds onto the powder surface. Then, monomers and initiators are added to the mica powder solution to carry out a polymerization reaction, copolymerizing the vinyl groups on the mica powder surface with the monomers and grafting the polymer onto the surface, thereby improving the dispersibility of the mica powder in the slurry and ultimately improving the interfacial bonding between the mica powder and the modified aramid fiber material. 4. In the corona-resistant mica / aramid fiber composite material for new energy vehicles of this application, the grafting rate of the mica powder to the surface is improved by limiting the ratio of the silane coupling agent to the mica powder, and the polymer coverage rate is improved by limiting the ratio of the mica powder, monomer, and initiator. 5. In the corona-resistant mica / aramid fiber composite material for new energy vehicles of the present application, meta-aramid chopped fibers and meta-aramid fibrids are used, and their length and ratio are limited. The chopped fibers have a rod-like structure, while the fibrids are a light and thin film. Within this ratio range, the fibrids adhere to the rod-like chopped fibers, and the chopped fibers form a scaffold that serves as the main support for the fibrids, and when subjected to external forces, they play a role in transmitting stress. In addition, the network structure in which the chopped fibers are entangled gives the composite material high density, excellent corona resistance, and a long service life. 6. According to the corona-resistant mica / aramid fiber composite material for new energy vehicles of the present application, by ultrasonically modifying the mixed aramid fibers, the degree of fiberization on the surface of the aramid fibers can be increased, and the surface active groups and surface energy can be increased. This can improve the dispersion of the aramid chopped fibers and also improve the specific surface area and surface roughness of the aramid fibers. This can increase the entanglement force between the chopped fibers and fibrids, fibrillate the aramid fibers, and strengthen the mechanical interlocking action at the fiber interfaces, thereby improving the mechanical properties and high temperature resistance of the composite material. 7. According to the first manufacturing method of the corona-resistant mica / aramid fiber composite material for new energy vehicles of the present application, the chopped fibers and fibrids are sufficiently softened and bonded through high-temperature hot-press molding, in which the hot-press temperature is limited, and the adhesive sufficiently penetrates into the pores of the modified aramid fiber paper and the modified mica paper to form a dense composite material overall, thereby improving the tensile strength of the composite material and providing good electrical properties. According to the second manufacturing method of the corona-resistant mica / aramid fiber blended paper for new energy vehicles of the present application, wet papermaking and high-temperature hot-press molding are adopted, and the hot-press temperature is limited, so that the adhesive melts and softens, allowing it to fully penetrate into the gaps between the chopped fibers and fibrids and bond them to form a dense whole, thereby improving the strength of the blended paper, avoiding problems such as delamination and powder loss, and improving the paper insertion processability and electrical properties. [Brief explanation of the drawings]

[0026] [Figure 1] 1 is a structural schematic diagram of a corona-resistant mica / aramid fiber composite material for new energy vehicles according to an embodiment of the present application; [Figure 2] 1 is a structural schematic diagram of a corona-resistant mica / aramid fiber blend paper for new energy vehicles according to an embodiment of the present application. DETAILED DESCRIPTION OF THE INVENTION

[0027] The present application will be described in detail below with reference to examples, but the present application is not limited to these examples.

[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. All reagents or raw materials used in the present invention can be purchased through conventional channels. Unless otherwise specified, all reagents or raw materials used in the present invention are used according to conventional methods in the art or in accordance with the product instructions. Furthermore, any methods and materials similar or equivalent to those described herein can be applied to the methods of the present invention. The preferred methods and materials in this patent are used for illustrative purposes only.

[0029] Experimental ingredients: 1. Three types of mica powder: Mica raw materials with different particle sizes are produced by wet grinding using a ball mill. The ball to material ratio is controlled to 4:1, the mass ratio of small balls to medium balls is set to 1:1, the rotation speed is set to 300 rpm, and the particle size and particle size distribution of the mica are measured using a laser particle size analyzer to prepare three types of mica slurries with different particle sizes. 2. Equipment: Ball mill: TCXQM-2, manufactured by Tianchuang Powder Co., Ltd.; Laser particle size distribution analyzer: BT-9300H, manufactured by Bai Te Instrument Co., Ltd.; Press machine: CHYZ-01, manufactured by Chuchuang Mechanical & Electronics Co., Ltd.; Tensile strength testing machine: SE-062, manufactured by Lorentzen Wettre, Sweden; Disintegrator: ZQS4, manufactured by Lorentzen Wettre, Sweden; Paper sheet forming machine: PY-Y814B, manufactured by Shenzhen Puyun Co., Ltd. 3. Reagents: Mica: manufactured by Hubei Ping'an Electric Materials Co., Ltd., silane coupling agent A171: manufactured by Momentive, USA, methyl methacrylate: manufactured by Shandong Xin Ying Shun New Materials Co., Ltd., benzoyl peroxide: manufactured by Jiangsu Qiangsheng Functional Chemical Co., Ltd., aramid fiber: manufactured by Teijin Limited, Japan. This application provides two types of mica / aramid fiber composites: the first composite can be considered a composite paper with a multilayer structure, and the second composite can be considered a mixed paper without a multilayer structure or with an indistinguishable layer structure. The mica / aramid fiber composite material of the present application includes a modified aramid fiber material, an adhesive, and a modified mica material. Specifically, for the first composite material A, the modified aramid fiber material is modified aramid fiber paper, and the modified mica material is modified mica paper. For the second composite material B, the modified aramid fiber material is modified aramid fiber, and the modified mica material is modified mica powder. First, with reference to FIG. 1, a first type of mica / aramid fiber composite material according to the present invention will be described.

[0030] Example A1: Composite Material A1# Composite material A1# was made from raw materials containing 40 wt% modified aramid fiber paper, 5 wt% adhesive, and 40 wt% modified mica paper, and the adhesive was FEP-fluorinated ethylene propylene copolymer (F46, tetrafluoroethylene-hexafluoropropylene copolymer). The modified mica paper is made from raw materials including mica powder, hydrochloric acid solution, ethanol, a silane coupling agent, methyl methacrylate, an initiator, and toluene. The mica powder consists of first, second, and third mica powders, with the particle size of the first mica powder being 90 μm, the particle size of the second mica powder being 130 μm, and the particle size of the third mica powder being 200 μm. The weight ratio of the first, second, and third mica powders is 1:3:3, respectively. The weight ratio of the silane coupling agent to the mica powder is 0.05:1, the weight ratio of the mica powder, methyl methacrylate, and initiator is 1:0.1:0.002, respectively, and the weight ratio of the mica powder, ethanol, and toluene is 1:6:5, respectively. The method for producing modified mica paper includes the following steps: Silane coupling agent A171 was added to ethanol and the pH was adjusted to 4 using hydrochloric acid solution. Next, mica powder was added, heated to 60°C, and stirred for 1 hour. The mixture was filtered, washed, and dried. Methyl methacrylate and benzoyl peroxide were then added to toluene, and the mixture was reacted at 70°C for 2 hours. After filtration, the mixture was dried at 110°C for 0.5 hours. Water was added and the mixture was stirred uniformly to form a 3% slurry, which was then molded into a paper sheet using a paper-forming machine to obtain modified mica paper. Here, the modified aramid fiber paper is made of meta-aramid chopped fibers and meta-aramid fibrids, and the lengths of the meta-aramid chopped fibers and meta-aramid fibrids are both 2 mm, and the weight ratio of the meta-aramid chopped fibers to the meta-aramid fibrids is 1:2. The method for producing modified aramid fiber paper includes the following steps: The meta-aramid chopped fibers and meta-aramid fibrids were disintegrated and dispersed, and water was added to form a pulp with a mass concentration of 0.1%. After ultrasonic treatment, the mixture was formed into a paper sheet using a paper-forming machine to obtain modified aramid fiber paper with a thickness of 0.05 mm. The ultrasonic treatment steps were 10 seconds per step, with 3-second intervals for a total of 6 minutes. The ultrasonic parameters were a frequency of 10 kHz and a power of 500 W. The manufacturing method of the composite material A1# includes the following steps: (1) Two rolls of modified aramid fiber paper were unwound, and adhesive was applied to the surface of each. (2) The modified mica paper was unwound and first laminated to one sheet of modified aramid fiber paper coated with adhesive, and then another sheet of modified aramid fiber paper coated with adhesive was laminated to the other side of the modified mica paper and dried. (3) The dried composite material A was hot pressed with a hot roller to finally obtain a 0.25 mm thick corona-resistant mica / aramid fiber composite material A1# for new energy vehicles. Here, the drying temperature was 120° C., the hot pressing temperature was 270° C., and the hot pressing pressure was 20 MPa.

[0031] Example A2: Composite Material A2# Composite material A2# was made from raw materials containing 50 wt% modified aramid fiber paper, 10 wt% adhesive, and 40 wt% modified mica paper, and the adhesive was FEP-fluorinated ethylene propylene copolymer (F46, tetrafluoroethylene-hexafluoropropylene copolymer). The modified mica paper is made from raw materials including mica powder, hydrochloric acid solution, ethanol, a silane coupling agent, methyl methacrylate, an initiator, and toluene. The mica powder consists of first, second, and third mica powders, with the particle size of the first mica powder being 110 μm, the particle size of the second mica powder being 150 μm, and the particle size of the third mica powder being 230 μm. The weight ratios of the first, second, and third mica powders are 1:5:5, respectively. The weight ratio of the silane coupling agent to the mica powder is 0.08:1. The weight ratios of the mica powder, methyl methacrylate, and initiator are 1:0.15:0.005, respectively. The weight ratio of the mica powder, ethanol, and toluene is 1:8:8, respectively. The method for producing modified mica paper includes the following steps. Silane coupling agent A171 was added to ethanol, and the pH value was adjusted to 4 using hydrochloric acid solution. Next, mica powder was added, and the mixture was heated to 80°C and stirred for 3 hours. The mixture was then filtered, washed, and dried. After that, the mixture was added to toluene, and methyl methacrylate and benzoyl peroxide were added, and the mixture was reacted at 90°C for 4 hours. After filtering, the mixture was dried at 130°C for 2 hours. Water was added and the mixture was stirred uniformly to form a slurry with a mass concentration of 4%, which was then paper-formed using a paper sheet forming machine to obtain modified mica paper. Here, the modified aramid fiber paper was made from meta-aramid chopped fibers and meta-aramid fibrids, and the length of the meta-aramid chopped fibers and meta-aramid fibrids was both 3 mm, and the weight ratio of the meta-aramid chopped fibers to the meta-aramid fibrids was 1:2.5. The manufacturing method for the modified aramid fiber paper includes the following steps: The meta-aramid chopped fibers and meta-aramid fibrids were disintegrated and dispersed, and water was added to form a pulp with a mass concentration of 0.3%. After ultrasonic treatment, the pulp was formed using a paper sheet forming machine to obtain a modified aramid fiber paper with a thickness of 0.05 mm. The ultrasonic treatment step was performed for 10 seconds at 3-second intervals for a total of 9 minutes, and the ultrasonic parameters were a frequency of 20 kHz and a power of 500 W. The manufacturing method of the composite material A2# includes the following steps: (1) Two rolls of modified aramid fiber paper were unwound, and adhesive was applied to the surface of each. (2) The modified mica paper was unwound and first laminated to one sheet of modified aramid fiber paper coated with adhesive, and then another sheet of modified aramid fiber paper coated with adhesive was laminated to the other side of the modified mica paper and dried. (3) The dried composite material A was hot pressed with a hot roller to finally obtain a 0.25 mm thick corona-resistant mica / aramid fiber composite material A2# for new energy vehicles. Here, the drying temperature was 120°C, the hot pressing temperature was 265°C, and the hot pressing pressure was 20 MPa.

[0032] Example A3: Composite Material A3# Composite material A3# was made from raw materials containing 60 wt% modified aramid fiber paper, 20 wt% adhesive, and 40 wt% modified mica paper, and the adhesive was a PFA-tetrafluoroethylene-perfluoroalkoxyvinyl ether copolymer. The modified mica paper is made from raw materials including mica powder, hydrochloric acid solution, ethanol, a silane coupling agent, methyl methacrylate, an initiator, and toluene. The mica powder consists of first, second, and third mica powders, with the particle size of the first mica powder being 100 μm, the particle size of the second mica powder being 140 μm, and the particle size of the third mica powder being 220 μm. The weight ratio of the first, second, and third mica powders is 1:4:4, respectively. The weight ratio of the silane coupling agent to the mica powder is 0.06:1. The weight ratio of the mica powder, methyl methacrylate, and initiator is 1:0.12:0.003, respectively. The weight ratio of the mica powder, ethanol, and toluene is 1:7:6, respectively. The method for producing modified mica paper includes the following steps. Silane coupling agent A171 was added to ethanol, and the pH value was adjusted to 4 using hydrochloric acid solution. Next, mica powder was added, and the mixture was heated to 70°C and stirred for 2 hours. The mixture was then filtered, washed, and dried. After that, the mixture was added to toluene, and methyl methacrylate and benzoyl peroxide were added, and the mixture was reacted at 80°C for 3 hours. After filtering, the mixture was dried at 120°C for 1 hour. Water was added and the mixture was stirred uniformly to form a slurry with a mass concentration of 5%, which was then paper-formed using a paper sheet forming machine to obtain modified mica paper. Here, the modified aramid fiber paper was made from meta-aramid chopped fibers and meta-aramid fibrids, and the length of the meta-aramid chopped fibers and meta-aramid fibrids was both 2 mm, and the weight ratio of the meta-aramid chopped fibers to the meta-aramid fibrids was 1:2.2. The manufacturing method for the modified aramid fiber paper includes the following steps: The meta-aramid chopped fibers and meta-aramid fibrids were disintegrated and dispersed, and water was added to form a pulp with a mass concentration of 0.5%. After ultrasonic treatment, the pulp was formed in a paper sheet forming machine to obtain a modified aramid fiber paper with a thickness of 0.05 mm. The ultrasonic treatment step was performed for 10 seconds at 3-second intervals for a total of 7 minutes, and the ultrasonic parameters were a frequency of 15 kHz and a power of 500 W. The manufacturing method of composite material A3# includes the following steps: (1) Two rolls of modified aramid fiber paper were unwound, and adhesive was applied to the surface of each. (2) The modified mica paper was unwound and first laminated to one sheet of modified aramid fiber paper coated with adhesive, and then another sheet of modified aramid fiber paper coated with adhesive was laminated to the other side of the modified mica paper and dried. (3) The dried composite material A was hot pressed with a hot roller to finally obtain a 0.25 mm thick corona-resistant mica / aramid fiber composite material A3# for new energy vehicles. Here, the drying temperature was 120° C., the hot pressing temperature was 310° C., and the hot pressing pressure was 20 MPa.

[0033] Example A4: Composite Material A4# In Example A4, compared to Example A1, the adhesive was a fluorinated ethylene propylene copolymer (F46, tetrafluoroethylene-hexafluoropropylene copolymer) and polyether ether ketone, and the weight ratio thereof was 3:1, except that the rest was the same.

[0034] Comparative Example A1: Comparative Composite Material A1# In Comparative Example A1, all other aspects were the same as in Example A3, except that the adhesive was a methyl-etherified amino resin.

[0035] Comparative example A2: Comparative composite material A2# In Comparative Example A2, the aramid fibers were unmodified compared to Example A3, but all other properties were the same.

[0036] Comparative example A3: Comparative composite material A3# In Comparative Example A3, compared with Example A3, the mica powder was two kinds of mica powder with particle sizes of 50 μm and 90 μm, and the weight ratio thereof was 1:3, and the rest were all the same.

[0037] Comparative example A4: Comparative composite material A4# In Comparative Example A4, the weight ratio of the first mica powder, the second mica powder, and the third mica powder was 1:1.5:1.2, respectively, compared to Example A3, and the rest were all the same.

[0038] Comparative example A5: Comparative composite material A5# In Comparative Example A5, the weight ratio of the silane coupling agent to the mica powder was 0.12:1 compared to Example A3, and all other details were the same.

[0039] Comparative example A6: Comparative composite material A6# In Comparative Example A6, all other aspects were the same as in Example A3, except that the mica powder was modified only with the silane coupling agent KH550.

[0040] Comparative example A7: Comparative composite material A7# In Comparative Example A7, compared to Example A3, all other conditions were the same except that the aramid fiber used was para-aramid fibrid.

[0041] Comparative example A8: Comparative composite material A8# In Comparative Example A8, all other conditions were the same as in Example A3, except that the lengths of the meta-aramid chopped fibers and meta-aramid fibrids were both 5 mm.

[0042] Comparative example A9: Comparative composite material A9# In Comparative Example A9, all other conditions were the same as in Example A3 except that the weight ratio of meta-aramid chopped fibers to para-aramid fibrids was 1:1.

[0043] Comparative example A10: Comparative composite material A10# In Comparative Example A10, the hot press molding temperature was 360°C, and all other conditions were the same as in Example A3.

[0044] Comparative example A11: Comparative composite material A11# Comparative Example A11 is a pure meta-aramid fiber paper with a thickness of 0.25 mm.

[0045] Comparative example A12: Comparative composite material A12# Comparative Example A12 is a 0.25 mm thick composite material A (commercially available as NHN) produced by combining 0.05 mm thick meta-aramid fiber paper on both sides of a polyimide film using polyurethane as an adhesive.

[0046] Experimental example 1. Electrical characteristics Breakdown voltage: The test was conducted in accordance with the national standard GB / T1408.1-2006. The sample thickness was 0.25 mm. A cylindrical electrode system with a diameter of 25 mm and a diameter of 75 mm was used. Five tests were conducted, and the average value was calculated. PDIV (Partial Discharge Inception Voltage): Tested in accordance with the national standard GB / T7354-2018. AC voltage frequency: 50Hz, boost speed: 50V / s, discharge inception voltage point: partial discharge amount 10PC, experimental temperature: 21~25℃, humidity: 45~55%. 2. Temperature resistance experiment Experimental method: The test was carried out according to the national standard GB / T4074.7-2009, and the heat resistance level of the material was evaluated using a three-point method. 3. Tensile strength Experimental method: Measurements were performed according to national standards GB / T20629.2-2013 and GB / T5591.2-2017. 4. Square wave corona resistance life Test method: Tests were conducted in accordance with the T / CEEIA415-2019 standard. Test conditions: peak-to-peak voltage Vp-p = 3000V, temperature 155±3°C, frequency = 20KHz, rising edge 100±10ns, duty cycle 50%. The composite materials A1# to A4# and the comparative composite materials A1# to A12# were sampled and subjected to the four experimental tests described above. The experimental results are shown in Table 1. [Table 1]

[0047] From the above experimental data, it can be seen that the composite materials A1# to 4# manufactured using the raw materials and methods defined in this application have excellent electrical properties, long square wave corona resistance life, excellent high temperature resistance, and excellent mechanical properties.

[0048] In comparative composite material A1#, a common commercially available adhesive was used, resulting in average electrical properties and high temperature resistance. In comparative composite material A2#, the aramid fibers were not modified, resulting in average electrical properties. Analysis showed that this was because the aramid fibers were relatively inert and had relatively poor interfacial bonding with other matrix materials.

[0049] In composite material A3#, the particle size of the mica powder is smaller than the range limited in this application, and as a result, the electrical properties are normal and the breakdown voltage is low. Analysis showed that the reason for this is that mica with a small particle size generates more mica fragments, most of which are added to the paper as "silt" components. The irregular arrangement loosens the paper structure, increases its thickness, damages the mixed structure of the paper, and reduces the mechanical properties of the paper. In addition, the pores in the paper increase, and when an external voltage is applied to the paper, the high insulating barrier of the large mica fragments in the Z direction is reduced, making it more likely that the paper will be broken down by the electron beam.

[0050] In composite material A4#, the proportion of small and medium particle size mica powder exceeds the range limited by this application, resulting in average electrical properties. Analysis showed that as the amount of relatively small particle size mica increases, the integrity of the mica flakes is destroyed, the size of the vertical structure increases, and the number of fine particles gradually increases and accumulates. The arrangement of the mica sheets also changes from flat to oblique, resulting in a deterioration of mechanical properties. In addition, due to the destruction of the mica flake structure, the large proportion of small particle size mica appears granular. The accumulation of particles creates numerous pores, limiting the insulating effect of the mica. When the paper is subjected to electrical breakdown, the resistance to current becomes lower and the current channel becomes shorter, thereby reducing the insulating properties of the entire paper.

[0051] In the comparative composite material A5#, the ratio of silane coupling agent to mica powder exceeds the range limited by the present application, and as a result, the electrical properties are ordinary. Analysis shows that the reason for this is that if too much coupling agent is used, the coupling efficiency will decrease due to the condensation reaction, resulting in a low grafting rate and poor modification effect; if too little coupling agent is used, the amount of coupling agent grafted to the surface will also be small.

[0052] In the comparative composite material A6#, only a silane coupling agent was used to modify the mica powder, and as a result, the electrical properties were ordinary. Analysis revealed that this was because the dispersibility was limited even after modification, and the interfacial bonding with other materials was not strong.

[0053] In the comparative composite material A7#, para-aramid fibrids are used, and as a result, the mechanical properties are relatively good, but the electrical properties are average. Analysis revealed that the reason for this is that while the para molecular structure exhibits excellent mechanical properties, the electrical properties are inferior to those of the meta structure, and the fibrids have poor coating properties for chopped fibers.

[0054] In the comparative composite material A8#, the length of the fibers used exceeds the range limited in this application, and as a result, the electrical properties are ordinary. Analysis shows that the reason is that as the fibers become longer, the possibility of entanglement between the fibers increases, making the fibers less likely to be dispersed, resulting in greater unevenness in the hot-pressed composite paper and further affecting the strength of the entire paper.

[0055] In the comparative composite material A9#, the ratio of fibrids to chopped fibers used is smaller than the range limited in this application, and as a result, the electrical properties are ordinary. Analysis has shown that this is because the chopped fibers are inserted into the paper structure, making it easier for pores to form in the paper, and when the ratio of fibrids is small, the adhesive effect with the chopped fibers is poor, making it difficult to demonstrate its electrical and thermal properties.

[0056] In the comparative composite material A10#, the hot press molding temperature is higher than the range limited in this application, and as a result, the electrical properties are average. Analysis shows that the reason is that when the temperature is too high, the raw materials age and the adhesive strength between the aramid fiber and the fibrids decreases. Comparative composite materials A11# to A12# are general commercially available composite materials A, and have average high temperature resistance and short corona resistance life.

[0057] Next, a second type of mica / aramid fiber composite material according to the present invention will be described with reference to FIG.

[0058] Example B1: Mixed Paper 1# Mixed paper 1# was made from raw materials containing modified aramid fiber, adhesive, and modified mica powder, the weight ratio of the modified aramid fiber to the modified mica powder was 0.1:1, the amount of adhesive added was 5% of the total weight of the modified aramid fiber and the modified mica powder, and the adhesive was a PFA-tetrafluoroethylene-perfluoroalkoxyvinyl ether copolymer. The modified mica powder is made from raw materials including mica powder, hydrochloric acid solution, ethanol, a silane coupling agent, methyl methacrylate, an initiator, and toluene. The mica powder consists of first, second, and third mica powders, with the particle size of the first mica powder being 90 μm, the particle size of the second mica powder being 130 μm, and the particle size of the third mica powder being 200 μm. The weight ratio of the first, second, and third mica powders is 1:3:3, respectively. The weight ratio of the silane coupling agent to the mica powder is 0.05:1, the weight ratio of the mica powder, methyl methacrylate, and initiator is 1:0.1:0.002, respectively, and the weight ratio of the mica powder, ethanol, and toluene is 1:6:5, respectively. The method for producing modified mica powder includes the following steps: Silane coupling agent A171 was added to ethanol, and the pH value was adjusted to 4 using hydrochloric acid solution. Next, mica powder was added, heated to 60°C and stirred for 1 hour, filtered, washed and dried. Next, the mixture was added to toluene while methyl methacrylate and benzoyl peroxide were added, and the mixture was reacted at 70°C for 2 hours. After filtration, the mixture was dried at 110°C for 0.5 hours to obtain modified mica powder. Here, the modified aramid fiber is made of meta-aramid chopped fiber and meta-aramid fibrid, and the length of the meta-aramid chopped fiber and meta-aramid fibrid is both 2 mm, and the weight ratio of the meta-aramid chopped fiber to the meta-aramid fibrid is 1:2. The method for producing modified aramid fibers includes the following steps: The meta-aramid chopped fibers and meta-aramid fibrids were defibrated and dispersed to form a pulp. After ultrasonic treatment, the resulting modified aramid fibers were dried. Each ultrasonic treatment was performed for 10 seconds, with 3-second intervals for a total of 6 minutes. The ultrasonic parameters were a frequency of 10 kHz and a power of 500 W. The manufacturing method of mixed paper 1# includes the following steps. (1) Modified mica powder was mixed with water to form a slurry with a mass concentration of 2%, and modified aramid fiber was mixed with water to form a slurry with a mass concentration of 0.2%. (2) The modified mica powder slurry, the modified aramid fiber slurry, and the adhesive were mixed and stirred uniformly. (3) The mixed slurry was put into a paper sheet forming machine, molded, pressed, dried, and further hot-pressed with a hot roller to finally obtain a 0.25 mm thick corona-resistant mica / aramid fiber blended paper No. 1 for new energy vehicles. Here, the pressing time was 5 minutes, the pressure was 300 kPa, the hot pressing temperature was 310° C., and the hot pressing pressure was 20 MPa.

[0059] Example B2: Mixed Paper 2# Mixed paper 2# was made from raw materials containing modified aramid fiber, adhesive, and modified mica powder. The weight ratio of the modified aramid fiber to the modified mica powder was 0.5:1, the amount of adhesive added was 10% of the total weight of the modified aramid fiber and the modified mica powder, and the adhesive was FEP-fluorinated ethylene propylene copolymer (F46, tetrafluoroethylene-hexafluoropropylene copolymer). The modified mica powder is made from raw materials including mica powder, hydrochloric acid solution, ethanol, silane coupling agent, methyl methacrylate, initiator, and toluene. The mica powder is composed of first, second, and third mica powders, with the particle size of the first mica powder being 110 μm, the particle size of the second mica powder being 150 μm, and the particle size of the third mica powder being 230 μm. The weight ratio of the first, second, and third mica powders is 1:5:5, respectively. The weight ratio of the silane coupling agent to the mica powder is 0.08:1. The weight ratio of the mica powder, methyl methacrylate, and initiator is 1:0.15:0.005, respectively. The weight ratio of the mica powder, ethanol, and toluene is 1:8:8, respectively. The method for producing the modified mica powder includes the following steps: Silane coupling agent A171 was added to ethanol, and the pH was adjusted to 4 using hydrochloric acid solution. Mica powder was then added, and the mixture was heated to 80°C and stirred for 3 hours. The mixture was then filtered, washed, and dried. The mixture was then added to toluene, while methyl methacrylate and benzoyl peroxide were added, and the mixture was reacted at 90°C for 4 hours. After filtering, the mixture was dried at 130°C for 2 hours to obtain modified mica powder. Here, the modified aramid fiber is made from meta-aramid chopped fiber and meta-aramid fibrid, and the length of the meta-aramid chopped fiber and meta-aramid fibrid are both 3 mm, and the weight ratio of the meta-aramid chopped fiber to the meta-aramid fibrid is 1:2.5. The method for producing the modified aramid fiber includes the following steps: The meta-aramid chopped fiber and meta-aramid fibrid are disintegrated and dispersed to form a pulp, which is then ultrasonicated and dried to obtain the modified aramid fiber. The ultrasonic treatment step is performed for 10 seconds per step, with 3-second intervals, for a total of 9 minutes, and the ultrasonic parameters are a frequency of 20 kHz and a power of 500 W. The manufacturing method of mixed paper 2# includes the following steps. (1) Modified mica powder was mixed with water to form a slurry with a mass concentration of 2%, and modified aramid fiber was mixed with water to form a slurry with a mass concentration of 1%. (2) The modified mica powder slurry, the modified aramid fiber slurry, and the adhesive were mixed and stirred uniformly. (3) The mixed slurry was put into a paper sheet forming machine to form it, pressed, dried, and then hot-pressed with a press plate to finally obtain a 0.25 mm thick corona-resistant mica / aramid fiber blended paper 2# for new energy vehicles. Here, the pressing time was 5 minutes, the pressure was 300 kPa, the hot pressing temperature was 265° C., and the hot pressing pressure was 20 MPa.

[0060] Example B3: Mixed Paper 3# Mixed paper 3# was made from raw materials containing modified aramid fiber, adhesive, and modified mica powder. The weight ratio of the modified aramid fiber to the modified mica powder was 0.3:1, the amount of adhesive added was 8% of the total weight of the modified aramid fiber and the modified mica powder, and the adhesive was a PFA-tetrafluoroethylene-perfluoroalkoxyvinyl ether copolymer. The modified mica powder is made from raw materials including mica powder, hydrochloric acid solution, ethanol, silane coupling agent, methyl methacrylate, initiator, and toluene. The mica powder is composed of first, second, and third mica powders, with the particle size of the first mica powder being 100 μm, the particle size of the second mica powder being 140 μm, and the particle size of the third mica powder being 220 μm. The weight ratio of the first, second, and third mica powders is 1:4:4, respectively. The weight ratio of the silane coupling agent to the mica powder is 0.06:1. The weight ratio of the mica powder, methyl methacrylate, and initiator is 1:0.12:0.003, respectively. The weight ratio of the mica powder, ethanol, and toluene is 1:7:6, respectively. The method for producing the modified mica powder includes the following steps: Silane coupling agent A171 was added to ethanol, and the pH was adjusted to 4 using hydrochloric acid solution. Mica powder was then added, and the mixture was heated to 70°C and stirred for 2 hours. The mixture was then filtered, washed, and dried. The mixture was then added to toluene, while methyl methacrylate and benzoyl peroxide were added, and the mixture was reacted at 80°C for 3 hours. After filtering, the mixture was dried at 120°C for 1 hour to obtain modified mica powder. Here, the modified aramid fiber is made from meta-aramid chopped fiber and meta-aramid fibrid, and the length of the meta-aramid chopped fiber and meta-aramid fibrid are both 2 mm, and the weight ratio of the meta-aramid chopped fiber to the meta-aramid fibrid is 1:2.2. The method for producing the modified aramid fiber includes the following steps: The meta-aramid chopped fiber and meta-aramid fibrid are disintegrated and dispersed to form a pulp, which is then ultrasonicated and dried to obtain the modified aramid fiber. The ultrasonic treatment step is performed for 10 seconds at 3-second intervals for a total of 7 minutes, and the ultrasonic parameters are a frequency of 15 kHz and a power of 500 W. The manufacturing method of mixed paper 3# includes the following steps. (1) Modified mica powder was mixed with water to form a slurry with a mass concentration of 2%, and modified aramid fiber was mixed with water to form a slurry with a mass concentration of 0.4%. (2) The modified mica powder slurry, the modified aramid fiber slurry, and the adhesive were mixed and stirred uniformly. (3) The mixed slurry was put into a paper sheet forming machine to form, press, dry, and then hot-press with a press plate to finally obtain a 0.25 mm thick corona-resistant mica / aramid fiber blended paper 3# for new energy vehicles. Here, the pressing time was 5 minutes, the pressure was 300 kPa, the hot pressing temperature was 302° C., and the hot pressing pressure was 20 MPa.

[0061] Example B4: Mixed paper 4# In Example B4, compared to Example B1, the adhesives were FEP-fluorinated ethylene propylene copolymer (F46, tetrafluoroethylene-hexafluoropropylene copolymer) and PEEK-polyether ether ketone, and the weight ratio was 3:1, but the rest was all the same.

[0062] Comparative example B1: Comparative mixed paper 1# In Comparative Example B1, all other properties were the same as in Example B3 except that the adhesive was a methyl-etherified amino resin.

[0063] Comparative example B2: Comparative mixed paper 2# In Comparative Example B2, the aramid fibers were not modified compared to Example B3, but everything else was the same.

[0064] Comparative example B3: Comparative mixed paper 3# In Comparative Example B3, the weight ratio of the modified aramid fiber to the modified mica powder was 1.2:1 compared to Example B3, and the rest were all the same.

[0065] Comparative example B4: Comparative mixed paper 4# In Comparative Example B4, compared with Example B3, the mica powder was two types of mica powder with particle sizes of 50 μm and 90 μm, and the weight ratio was 1:3, except that the rest were all the same.

[0066] Comparative Example B5: Comparative mixed paper 5# In Comparative Example B5, the weight ratio of the first mica powder, the second mica powder, and the third mica powder was 1:1.5:1.2, respectively, compared with Example B3, and the rest were all the same.

[0067] Comparative example B6: Comparative mixed paper 6# In Comparative Example B6, the weight ratio of the silane coupling agent to the mica powder was 0.12:1 compared to Example B3, and all other details were the same.

[0068] Comparative example B7: Comparative mixed paper 7# In Comparative Example B7, all other conditions were the same as in Example B3, except that the mica powder was modified only with the silane coupling agent KH550.

[0069] Comparative example B8: Comparative mixed paper 8# In Comparative Example B8, compared to Example B3, all other conditions were the same except that the aramid fiber used was para-aramid fibrid.

[0070] Comparative example B9: Comparative mixed paper 9# In Comparative Example B9, all other conditions were the same as in Example B3, except that the lengths of the meta-aramid chopped fibers and meta-aramid fibrids were both 5 mm.

[0071] Comparative Example B10: Comparative mixed paper 10# In Comparative Example B10, the weight ratio of meta-aramid chopped fibers to meta-aramid fibrids was 1:1 compared to Example B3, but the rest was all the same.

[0072] Comparative Example B11: Comparative mixed paper 11# In Comparative Example B11, the hot press molding temperature was 380°C, and all other conditions were the same as in Example B3.

[0073] Comparative Example B12: Meta-aramid fiber paper Comparative Example B12 is a commercially available pure meta-aramid fiber paper having a thickness of 0.25 mm.

[0074] Experimental example 1. Electrical characteristics Breakdown voltage: The test was conducted in accordance with the national standard GB / T1408.12006. The sample thickness was 0.25 mm. A cylindrical electrode system with a diameter of 25 mm and a diameter of 75 mm was used. Five tests were conducted, and the average value was calculated. PDIV (Partial Discharge Inception Voltage): Tested in accordance with the national standard GB / T7354-2018. AC voltage frequency: 50Hz, boost speed: 50V / s, discharge inception voltage point: partial discharge amount 10PC, experimental temperature: 21~25℃, humidity: 45~55%. 2. Temperature resistance experiment Experimental method: The test was carried out according to the national standard GB / T4074.7-2009, and the heat resistance level of the material was evaluated using a three-point method. 3. Tensile strength Experimental method: Measurements were performed according to national standards GB / T20629.2-2013 and GB / T5591.2-2017. Corona-resistant life Test method: Tests were conducted in accordance with the T / CEEIA415-2019 standard. Test conditions: peak-to-peak voltage Vp-p = 3000V, temperature 155±3°C, frequency = 20KHz, rising edge 100±10ns, duty cycle 50%. The composite materials B1# to B4#, comparative composite materials B1# to B11#, and meta-aramid fiber paper were sampled and the four experimental tests described above were carried out. The experimental results are shown in Table 2. [Table 2]

[0075] From the above experimental data, it was found that the mixed papers 1# to 4# manufactured using the raw materials and methods specified in this application have excellent electrical properties, long square wave corona resistance life, excellent high temperature resistance, and excellent mechanical properties.

[0076] In comparative mixed paper 1#, a common commercially available adhesive was used, and as a result, the electrical properties and high temperature resistance were common. In comparative mixed paper 2#, the aramid fiber was not modified, and as a result, the electrical properties were common. Analysis showed that this was because the aramid fiber was relatively inert and had relatively poor interfacial bonding action with other matrix materials.

[0077] In comparative blended paper 3#, the ratio of modified aramid fiber to modified mica powder exceeds the range limited by this application, and as a result, the electrical properties are ordinary. Analysis shows that the reason for this is that the bonding state between aramid fiber and mica becomes saturated, and excess fiber accumulates in the gaps between the mica flakes or on the surface of the flakes, which increases the thickness of the paper and makes the electric field distribution within the paper structure uneven. This generates a large amount of heat that cannot be dissipated, and reduces the strength of the dielectric breakdown field.

[0078] In comparative mixed paper 4#, the particle size of the mica powder was smaller than the range limited by this application, and as a result, the electrical properties were average. Analysis showed that the reason for this was that mica with a small particle size produced more mica fragments, most of which were added to the paper as ``silt'' components. The irregular arrangement reduced the adhesion between the mica and the fibers, loosened the paper structure, increased the paper thickness, damaged the mixed structure of the paper, and reduced the mechanical properties of the paper. In addition, the pores in the paper increased, and when an external voltage was applied to the paper, the high insulating barrier in the Z direction of the large mica fragments was reduced, making it more likely that the paper would be subjected to electrical breakdown by the electron beam.

[0079] In the comparative blended paper 5#, the proportion of small and medium particle size mica powder exceeded the range limited by this application, resulting in average electrical properties. Analysis showed that as the amount of relatively small particle size mica increased, the integrity of the mica flakes was destroyed, the size of the vertical structure increased, and the number of fine particles gradually increased and accumulated. The arrangement of the mica sheets also changed from flat to oblique, weakening the bond between the fibers and mica and reducing the mechanical properties. In addition, due to the destruction of the mica flake structure, the large proportion of small particle size mica appeared granular. As the particles accumulated, numerous pores were generated, limiting the insulating effect of the mica. When the paper was subjected to electrical breakdown, the resistance to current became lower and the current channel became shorter, resulting in a deterioration of the insulating properties of the entire paper.

[0080] In the comparative mixed paper 6#, the ratio of silane coupling agent to mica powder exceeds the range limited by this application, and as a result, the electrical properties are ordinary. Analysis showed that the reason for this is that if too much coupling agent is used, the coupling efficiency decreases due to the condensation reaction, the grafting rate decreases, and the modification effect is poor; if too little coupling agent is used, the amount of coupling agent grafted to the surface also decreases.

[0081] In the comparative mixed paper 7#, only a silane coupling agent was used to modify the mica powder, and as a result, the electrical properties were ordinary. Analysis revealed that this was because the dispersibility was limited even after modification, and the interfacial bonding strength with other materials was not high.

[0082] In comparative mixed paper 8#, para-aramid fibrids are used, and as a result, the mechanical properties are relatively good, but the electrical properties are average. Analysis revealed that the reason for this is that while the para molecular structure exhibits excellent mechanical properties, the electrical properties are inferior to those of the meta structure, and the fibrids have poor coating properties for chopped fibers.

[0083] In the comparative blended paper 9#, the length of the fibers used exceeds the range limited by this application, and as a result, the electrical properties are ordinary. Analysis shows that the reason is that as the fibers become longer, the possibility of entanglement between the fibers increases, making the fibers less likely to disperse, which increases the unevenness of the hot-pressed composite paper and further affects the strength of the entire paper.

[0084] In comparative mixed paper 10#, the ratio of fibrids to chopped fibers used is smaller than the range limited in this application, and as a result, the electrical properties are ordinary. Analysis has shown that the reason for this is that the chopped fibers have no bonding strength with the mica, and the chopped fibers are relatively thicker than the mica, so they are inserted into the paper structure, causing some damage to the bond between the fibrids and mica, making it easier for pores to form in the paper. When the ratio of fibrids is small, the chopped fibers have a poor adhesive effect with the mica, making it difficult for them to exert their electrical and thermal properties.

[0085] In the comparative mixed paper 11#, the hot press molding temperature was higher than the range limited in this application, and as a result, the electrical properties were average. Analysis showed that the reason was that if the temperature was too high, the raw materials would age and the adhesive strength between the aramid fibers, fibrids, and mica would decrease. The meta-aramid fiber paper of comparative example B12 did not contain mica components, and as a result, the electrical properties and high temperature resistance were average, but the mechanical properties were relatively good.

[0086] The above description is merely an example of the present application, and the scope of protection of the present application is not limited by these specific examples, but is determined by the scope of the claims of the present application. Those skilled in the art can make various modifications and changes to the present application. Any changes, equivalent replacements, improvements, etc. made within the technical idea and principle of the present application shall be included in the scope of protection of the present application. [Explanation of symbols]

[0087] 11 Modified aramid fiber powder 12 Adhesive 13 Modified mica paper 21 Modified aramid fiber 22 Adhesive 23 Modified mica powder

Claims

1. A corona-resistant mica / aramid fiber composite material for new energy vehicles, comprising: The raw materials for producing the composite material include a modified aramid fiber material, an adhesive, and a modified mica material; the adhesive comprises one or more of tetrafluoroethylene-perfluoroalkoxyvinyl ether copolymer, fluorinated ethylene propylene copolymer, ethylene-tetrafluoroethylene copolymer, polyether ether ketone, and polyetherimide; the modified mica material is made from raw materials including mica powder, hydrochloric acid solution, ethanol, a silane coupling agent, methyl methacrylate, an initiator, and toluene; the mica powder comprises first mica powder, second mica powder, and third mica powder, the particle size of the first mica powder being 90-110 μm, the particle size of the second mica powder being 130-150 μm, and the particle size of the third mica powder being 200-230 μm; and the weight ratio of the first mica powder to the second mica powder to the third mica powder is 1:(3-5):(3-5), respectively.

2. 2. The corona-resistant mica / aramid fiber composite material for new energy vehicles according to claim 1, wherein the weight ratio of the silane coupling agent to the mica powder is (0.05-0.08):1, the weight ratio of the mica powder, methyl methacrylate, and initiator is 1:(0.1-0.15):(0.002-0.005), respectively, and the weight ratio of the mica powder, ethanol, and toluene is 1:(6-8):(5-8), respectively.

3. The method for producing the modified mica material includes: Step S11: adding a silane coupling agent to ethanol and adjusting the pH value to 4 using hydrochloric acid solution; Step S12: adding mica powder, heating to 60-80°C, stirring for 1-3 hours, filtering, washing, and drying; and step S13 of adding methyl methacrylate and an initiator while adding the mixture to toluene, reacting at 70-90°C for 2-4 hours, filtering, and then drying at 110-130°C for 0.5-2 hours.

4. 4. The corona-resistant mica / aramid fiber composite material for new energy vehicles as claimed in claim 3, wherein the silane coupling agent is A171 and the initiator is benzoyl peroxide.

5. The corona-resistant mica / aramid fiber composite material for new energy vehicles according to claim 1, characterized in that the modified aramid fiber material is made of meta-aramid chopped fibers and meta-aramid fibrids, the lengths of the meta-aramid chopped fibers and meta-aramid fibrids are both 2-3 mm, and the weight ratio of the meta-aramid chopped fibers to the meta-aramid fibrids is 1:(2-2.5).

6. The method for producing the modified aramid fiber material includes: Step S21 of defibrating and dispersing the meta-aramid chopped fibers and meta-aramid fibrids to form pulp; and (S22) ultrasonically treating the pulp. The corona-resistant mica / aramid fiber composite material for new energy vehicles according to claim 5 .

7. The corona-resistant mica / aramid fiber composite material for new energy vehicles according to claim 6, characterized in that the ultrasonic treatment step is performed for 10 seconds at an interval of 3 seconds for a total of 6 to 9 minutes, and the ultrasonic parameters are a frequency of 10 to 20 kHz and a power of 500 W.

8. The modified aramid fiber material is a modified aramid paper, and the modified mica material is a modified mica paper; The corona-resistant mica / aramid fiber composite material for new energy vehicles according to any one of claims 1 to 7, characterized in that the raw materials are 40-60 wt% modified aramid fiber paper, 5-20 wt% adhesive, and 40-60 wt% modified mica paper.

9. The modified aramid fiber material is modified aramid paper, the modified mica material is modified mica paper, and the raw materials are 40 to 60% by weight of modified aramid fiber paper, 5 to 20% by weight of adhesive, and 40 to 60% by weight of modified mica paper; The corona-resistant mica / aramid fiber composite material for new energy vehicles according to claim 3, characterized in that the method for producing the modified mica material further comprises step S14 of adding water and stirring uniformly to form a slurry, and then using a paper sheet forming machine to form the modified mica paper.

10. The modified aramid fiber material is modified aramid paper, the modified mica material is modified mica paper, and the raw materials are 40 to 60% by weight of modified aramid fiber paper, 5 to 20% by weight of adhesive, and 40 to 60% by weight of modified mica paper; 7. The corona-resistant mica / aramid fiber composite material for new energy vehicles according to claim 6, wherein the method for producing the modified aramid fiber material further comprises step S23 of forming the modified aramid fiber paper using a paper sheet forming machine.

11. A method for producing the corona-resistant mica / aramid fiber composite material for new energy vehicles according to any one of claims 8 to 10, comprising: Step S01: unwinding two modified aramid fiber paper rolls and applying adhesive to their surfaces; Step S02: unwinding the modified mica paper, first laminating it to one sheet of modified aramid fiber paper coated with adhesive, and then laminating another sheet of modified aramid fiber paper coated with adhesive to the other side of the modified mica paper and drying them; and step S03: hot-pressing the dried composite material with a hot roller to finally obtain a corona-resistant mica / aramid fiber composite material for new energy vehicles.

12. The modified aramid fiber material is a modified aramid fiber, and the modified mica material is a modified mica powder; 8. The corona-resistant mica / aramid fiber composite material for new energy vehicles according to claim 1, wherein the weight ratio of the modified aramid fiber to the modified mica powder is (0.1-0.5):1, and the amount of the adhesive added is 5-10% of the total weight of the modified aramid fiber and the modified mica powder.

13. The method for producing the corona-resistant mica / aramid fiber composite material for new energy vehicles according to claim 12, comprising: Step S01: mixing modified mica powder with water to form a slurry with a mass concentration of 2 to 10%, and mixing modified aramid fiber with water to form a slurry with a mass concentration of 0.1 to 1%; Step S02: Mixing and uniformly stirring the modified mica powder slurry, the modified aramid fiber slurry, and the adhesive; and step S03, wherein the mixed slurry is put into a paper sheet forming machine to form, press, dry, and then hot-press with a hot roller to finally obtain a corona-resistant mica / aramid fiber blended paper for new energy vehicles.

14. 14. The method according to claim 13, wherein in step S03, the drying temperature is 120° C., the hot pressing temperature is 265 to 310° C., and the hot pressing pressure is 20 MPa.

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