WO2024082973A1

WO2024082973A1 - Corona-resistant mica/aramid fiber composite material for new-energy vehicles and preparation method therefor

Info

Publication number: WO2024082973A1
Application number: PCT/CN2023/123390
Authority: WO
Inventors: 郑广会; 王文; 张铃; 赵培振; 郑金宇; 陆松
Original assignee: 天蔚蓝电驱动科技(江苏)有限公司
Priority date: 2022-10-20
Filing date: 2023-10-08
Publication date: 2024-04-25

Abstract

A corona-resistant mica/aramid fiber composite material for new-energy vehicles and a preparation method therefor. Preparation raw materials comprise a modified aramid fiber material, an adhesive, and a modified mica material; the modified mica material comprises mica powder, a hydrochloric acid solution, ethanol, a silane coupling agent, methyl methacrylate, an initiator, and methylbenzene; the mica powder is composed of first mica powder, second mica powder, and third mica powder, the particle size of the first mica powder is 90-110 μm, the particle size of the second mica powder is 130-150 μm, and the particle size of the third mica powder is 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). The modified aramid fiber material and the modified mica material are compounded by using the adhesive, so that the overall compactness, the interpolated paper manufacturability, the corona resistance, the PDIV, and the temperature resistance level of the composite material are improved, and the material can significantly improve the electrical insulation performance and the long-term safe operation life of new-energy vehicles.

Description

Corona-resistant mica/aramid fiber composite material for new energy vehicles and preparation method thereof

This application claims the priority of the Chinese patent application filed with the China Patent Office on October 20, 2022, with application number 202211286443.2, and invention name “A corona-resistant mica/aramid fiber composite material for new energy vehicles and preparation method thereof”, and the priority of the Chinese patent application filed with the China Patent Office on October 20, 2022, with application number 202211286451.7, and invention name “A corona-resistant mica/aramid fiber mixed paper for new energy vehicles and preparation method thereof”. The entire contents of the above two prior applications are incorporated into this application by reference.

Technical Field

The present application relates to the field of insulating materials, especially the technical field of mica composite materials, and more specifically to a corona-resistant mica/aramid fiber composite material for new energy vehicles and a preparation method thereof.

Background technique

Existing high-temperature resistant slot insulation and interphase insulation papers above Class H used in new energy vehicle motors are mostly pure aramid fiber paper, or aramid fiber paper and polyimide film composited with high-temperature resistant adhesives. The typical composite paper structure is Nomex fiber paper/PI film/Nomex fiber paper (NHN), and the composite adhesives are mostly epoxy, polyurethane, or polyacrylate adhesives.

Aramid fiber pure paper or NHN composite paper has high heat resistance and excellent performance in the insulation structure of 400V voltage platform motors for new energy vehicles. However, for 800V voltage platform motors, due to the high voltage level, pulse width modulation spike voltage, and the influence of environmental factors, the maximum safe voltage may reach 2300V or even higher, which is far higher than the partial discharge inception voltage (PDIV) of existing conventional low-voltage motor insulation materials. The probability of partial discharge during motor operation is very high. Therefore, for 800V voltage platform automotive motors, the corona resistance of the insulation material must be considered.

The existing technology improves the corona resistance life of composite paper by adding mica components to organic aramid fiber paper, or by using epoxy, polyurethane or polyacrylate adhesives to composite aramid fiber paper and mica paper. However, the mica-containing composite paper prepared by these two methods generally has problems such as easy powder loss, easy cracking, and delamination. The corona resistance and high temperature resistance are average, and cannot meet the process requirements for large-scale application of new energy vehicle motors.

Summary of the invention

In order to solve the above problems, a corona-resistant mica/aramid fiber composite material for new energy vehicles and a preparation method thereof are provided. The present application provides modified mica materials and modified aramid fiber materials with excellent corona resistance, and uses PFA-tetrafluoroethylene-perfluoroalkoxy vinyl ether copolymer, FEP-fluorinated ethylene propylene copolymer (F46, tetrafluoroethylene and hexafluoropropylene copolymer), ETFE-ethylene-tetrafluoroethylene copolymer, PEEK-polyetheretherketone, PEI-polyetherimide and other high temperature resistant, low dielectric constant adhesives, and hot-presses the modified aramid fiber material and the modified mica material for compounding or mixing, which can improve the overall density and paper insertion processability, corona resistance, partial discharge inception voltage (PDIV) and temperature resistance grade of the composite material. The use of this material as slot bottom insulation paper and interphase insulation paper can significantly improve the electrical insulation performance and long-term safe operation life of new energy vehicle motors.

According to one aspect of the present application, a corona-resistant mica/aramid fiber composite material for new energy vehicles is provided, wherein the raw materials for preparing the composite material include: a modified aramid fiber material, an adhesive and a modified mica material;

The adhesive comprises one or more of tetrafluoroethylene-perfluoroalkoxy vinyl ether copolymer, fluorinated ethylene propylene copolymer, ethylene-tetrafluoroethylene copolymer, polyetheretherketone and polyetherimide,

The modified mica material is prepared from the following raw materials: mica powder, hydrochloric acid solution, ethanol, silane coupling agent, methyl methacrylate, initiator and toluene;

The mica powder consists of a first mica powder, a second mica powder and a third mica powder, the particle size of the first mica powder is 90-110 μm, the particle size of the second mica powder is 130-150 μm, and the particle size of the third mica powder is 200-230 μm; the weight ratio of the first mica powder, the second mica powder and the third mica powder is 1:(3-5):(3-5) respectively.

Further, the adhesive is FEP-fluorinated ethylene propylene copolymer (F46, tetrafluoroethylene and hexafluoropropylene copolymer); further, the adhesive includes FEP-fluorinated ethylene propylene copolymer (F46, tetrafluoroethylene and hexafluoropropylene copolymer) and polyetheretherketone, with a weight ratio of 3:1.

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

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 to methyl methacrylate and the initiator is 1:(0.1-0.15):(0.002-0.005) respectively, and the weight ratio of the mica powder to ethanol and toluene is 1:(6-8):(5-8) respectively.

Optionally, the method for preparing the modified mica material comprises the following steps:

S11, adding a silane coupling agent to ethanol, and adjusting the pH value to 4 using a hydrochloric acid solution;

S12, add mica powder, heat to 60-80°C, stir for 1-3h, filter, wash and dry;

S13, adding the mixture into toluene, adding methyl methacrylate and initiator at the same time, reacting at 70-90°C for 2-4h, filtering and drying at 110-130°C for 05-2h.

Specifically, the mass concentration of the slurry is 3-5%.

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

Optionally, the modified aramid fiber material is prepared from meta-aramid chopped fibers and meta-aramid fibrids, the lengths of the meta-aramid chopped fibers and the 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).

Optionally, the method for preparing the modified aramid fiber material comprises the following steps:

S21, dispersing the meta-aramid chopped fibers and the meta-aramid fibrids to form a slurry,

S22, subjecting the slurry to ultrasonic treatment. Specifically, the mass concentration of the slurry is 0.1-0.5%.

Optionally, the ultrasonic treatment step is 10 seconds per ultrasonic treatment, with an interval of 3 seconds, and a total ultrasonic treatment of 6-9 minutes; ultrasonic parameters: frequency is 10-20kHz, power is 500W.

Optionally, the modified aramid fiber material is modified aramid paper, and the modified mica material is modified mica paper.

The weight percentages of the raw materials are: 40-60% of modified aramid fiber paper, 5-20% of adhesive and 40-60% of modified mica paper.

Optionally, the method for preparing the modified mica material further comprises: S14, adding water and stirring evenly to form a slurry, and then passing the slurry through a paper sheet forming machine to obtain the modified mica paper.

Optionally, the method for preparing the modified aramid fiber material further comprises: S23, papermaking the modified aramid fiber paper through a paper sheet forming machine.

Optionally, water is added during the process of "S21, dispersing the meta-aramid chopped fibers and the meta-aramid fibrids to form a slurry".

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 fiber to the modified mica powder is (0.1-0.5):1, and the added amount of the adhesive is 5-10% of the total weight of the modified aramid fiber and the modified mica powder.

According to another aspect of the present application, a method for preparing the above-mentioned corona-resistant mica/aramid fiber composite material for new energy vehicles is provided, comprising the following steps:

S01, unwinding two rolls of modified aramid fiber paper and coating adhesive on the surfaces thereof respectively;

S02, unwinding the modified mica paper, first laminating it on one of the modified aramid fiber papers coated with an adhesive, and then laminating another modified aramid fiber paper coated with an adhesive on the other side of the modified mica paper and drying it;

S03, subjecting the dried composite material to hot rolling and hot pressing, and finally obtaining a corona-resistant mica/aramid fiber composite material for new energy vehicles.

S01, mixing modified mica powder with water to prepare a slurry with a mass concentration of 2-10%, and mixing modified aramid fiber with water to prepare a slurry with a mass concentration of 0.1-1%;

S02, mixing and stirring the modified mica powder slurry, the modified aramid fiber slurry and the adhesive evenly;

S03, adding the mixed pulp into a paper sheet former to form it, drying it after pressing, and then hot pressing it with a hot roller to finally obtain a corona-resistant mica/aramid fiber mixed paper for new energy vehicles.

Optionally, the drying temperature is 120° C., the hot pressing temperature is 265-310° C., and the hot pressing pressure is 20 MPa.

The beneficial effects of this 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, by using PFA-tetrafluoroethylene-perfluoroalkoxy vinyl ether copolymer, FEP-fluorinated ethylene propylene copolymer (F46, tetrafluoroethylene and hexafluoropropylene copolymer), ETFE-copolymer of ethylene and tetrafluoroethylene, PEEK-polyetheretherketone, PEI-polyetherimide and other high-temperature resistant, low dielectric constant adhesives to compound modified aramid fiber materials and modified mica materials, combined with modified mica materials and modified aramid fiber materials with excellent corona resistance, the overall density and paper insertion processability, corona resistance, partial discharge inception voltage (PDIV) and temperature resistance grade of the composite material can be improved.

2. According to the corona-resistant mica/aramid fiber composite material for new energy vehicles of the present application, the mica powder is limited to be composed of three mica powders with different particle sizes, and their respective proportions are limited at the same time. The large-particle mica powder layer is complete in flaky form, which can play a better stress transfer role, avoid the paper from breaking due to concentrated force, and at the same time give the paper a certain stiffness. The small-particle mica with a relatively small proportion is filled between the large mica flakes, which can give the paper better strength properties, reduce the destructive effect on the fibers, and form a "brick and mud" structure, which can give the paper better strength properties.

Among them, the lamellar structure of the two larger mica powders can act as "bricks" to provide more More attachment carriers, and the regular arrangement of two larger particle size mica powders also gives the paper better flatness. It has a larger diameter-to-thickness ratio, and the high insulation effect of the layer in the Z direction has a good blocking effect on the current, delaying the formation of the current channel, effectively delaying the spread of the arc, reducing the fiber carbonization damage, reducing the size and area of the breakdown point, and improving the corona resistance.

3. According to the corona-resistant mica/aramid fiber composite material for new energy vehicles of the present application, a mica material is modified by using a silane coupling agent and a polymer monomer. There are hydroxyl groups on the surface of the mica powder. A silane coupling agent A171 is used to introduce double bonds on the powder surface. Then, the monomer and the initiator are added to the mica powder liquid for polymerization. The vinyl on the surface of the mica powder is copolymerized with the monomer to realize surface grafting of the polymer, thereby improving its dispersibility in the slurry and ultimately improving its interface bonding performance with the modified aramid fiber material.

4. According to the corona-resistant mica/aramid fiber composite material for new energy vehicles of the present application, the grafting rate on the surface of mica powder is increased by limiting the ratio of silane coupling agent to mica powder; and the coverage rate of polymer is increased by limiting the ratio of mica powder to monomer and initiator.

5. According to the corona-resistant mica/aramid fiber composite material for new energy vehicles of the present application, meta-aramid chopped fibers and meta-aramid fibrils are used, and their lengths and ratios are limited. The chopped fibers are rod-shaped structures, while the fibrils are light and thin films. Within this ratio range, the fibrils will adhere to the rod-shaped chopped fibers, which helps the chopped fibers to form a scaffold and become the backbone to which the fibrils depend. When subjected to external force, they can transfer stress. At the same time, the network structure interwoven by the chopped fibers makes the composite material high in density, excellent in corona resistance, and long in 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 surface fibrillation degree of the aramid fibers can be enhanced, the surface active groups and surface energy can be increased, thereby improving the dispersion performance of the aramid chopped fibers. At the same time, the specific surface area and surface roughness of the aramid fibers can be improved, the interweaving force of the chopped fibers and the precipitated fibers can be increased, the aramid fibers can be made into fibrils, and the mechanical interlocking effect between the fiber interfaces can be enhanced, thereby improving the mechanical properties and high temperature resistance of the composite material.

7. According to the first preparation method of the corona-resistant mica/aramid fiber composite material for new energy vehicles of the present application, high-temperature hot pressing is performed and the hot pressing temperature is limited so that the chopped fibers and precipitated fibers are fully softened and bonded, and at the same time, the adhesive is fully penetrated into the pores of the modified aramid fiber paper and the modified mica paper to form an overall dense composite material, thereby improving the tensile strength of the composite material and improving electrical properties.

According to the second preparation method of the corona-resistant mica/aramid fiber mixed paper for new energy vehicles of the present application, By adopting wet papermaking and high-temperature hot pressing molding, and limiting the hot pressing temperature, the adhesive is melted and softened, and fully penetrates into the gaps between the chopped fibers and the precipitated fibers, bonding them into a dense whole, thereby improving the strength of the mixed paper, avoiding problems such as delamination and powdering, and the paper inserting processability and electrical properties are good.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic diagram of the structure of a corona-resistant mica/aramid fiber composite material for new energy vehicles according to an embodiment of the present application;

FIG2 is a schematic diagram of the structure of the corona-resistant mica/aramid fiber blended paper for new energy vehicles involved in an embodiment of the present application.

Description of reference numerals:

11: modified aramid fiber powder; 12: adhesive; 13: modified mica paper;

21: modified aramid fiber; 22: adhesive; 23: modified mica powder.

Detailed ways

The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.

Unless otherwise defined, all professional and scientific terms used herein have the same meanings as those familiar to those skilled in the art. The reagents or raw materials used in the present invention can be purchased through conventional channels. Unless otherwise specified, the reagents or raw materials used in the present invention are used in a conventional manner in the art or in accordance with the product instructions. In addition, any method and material similar or equivalent to the described content can be applied to the method of the present invention. The preferred implementation methods and materials in this patent are for demonstration purposes only.

Experimental materials:

1. Three types of mica powder with different particle sizes: Mica raw materials with different particle sizes were prepared by wet grinding in a ball mill, the ball-to-material ratio was controlled to be 4:1, the mass ratio of small and medium balls was 1:1, the speed was set to 300 rpm, and the mica particle size and particle size distribution were measured by a laser particle size analyzer to prepare three types of mica slurries with different particle sizes.

2. Instruments: Ball mill: TCXQM-2, Tianchuang Powder Co., Ltd.; Laser particle size analyzer: BT-9300H, Better Instrument Co., Ltd.; Press: CHYZ-01, Chuchuang Electromechanical; Tensile strength tester: SE-062, Lorentzen Wether, Sweden; Flaker: ZQS4, Lorentzen Wether, Sweden; Paper sheet forming machine, Shenzhen Puyun, PY-Y814B.

3. Reagents: Mica: Hubei Ping'an Electrical Materials Co., Ltd.; silane coupling agent A171, Momentive, USA; methyl methacrylate, Shandong Xinyingshun New Materials Co., Ltd.; benzoyl peroxide, Jiangsu Qiangsheng Functional Chemical Co., Ltd.; aramid fiber: Teijin, Japan.

The present application provides two types of mica/aramid fiber composite materials. The first composite material can be considered as composite paper with a multi-layer structure, and the second composite material can be considered as mixed paper without a multi-layer structure or with an indistinguishable layered structure.

The mica/aramid fiber composite material according to the present application comprises 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 , the first mica/aramid fiber composite material according to the present application is introduced.

Example A1: Composite material A1#

Composite material A1# is prepared from the following raw materials in weight percentage: 40% modified aramid fiber paper, 5% adhesive and 40% modified mica paper, wherein the adhesive is FEP-fluorinated ethylene propylene copolymer (F46, tetrafluoroethylene and hexafluoropropylene copolymer).

Among them, the modified mica paper is prepared from the following raw materials: mica powder, hydrochloric acid solution, ethanol, silane coupling agent, methyl methacrylate, initiator and toluene. The mica powder is composed of the first mica powder, the second mica powder and the third mica powder. The particle size of the first mica powder is 90μm, the particle size of the second mica powder is 130μm, and the particle size of the third mica powder is 200μm; the weight ratio of the first mica powder, the second mica powder and the third mica powder is 1:3:3. The weight ratio of the silane coupling agent to the mica powder is 0.05:1, the weight ratio of the mica powder to methyl methacrylate and the initiator is 1:0.1:0.002, and the weight ratio of the mica powder to ethanol and toluene is 1:6:5.

The preparation method of modified mica paper comprises the following steps:

Add silane coupling agent A171 to ethanol, and use hydrochloric acid solution to adjust the pH value to 4; then add mica powder, heat to 60°C and stir for 1 hour; filter, wash and dry, then add the mixture to toluene, and add methyl methacrylate and benzoyl peroxide at the same time, react at 70°C for 2 hours, filter and dry at 110°C for 0.5 hour; add water and stir evenly to form a slurry with a mass concentration of 3%, and pass it through a paper sheet forming machine to obtain modified mica paper.

The modified aramid fiber paper is made of meta-aramid short-cut fibers and meta-aramid fibrids. The length of the meta-aramid short-cut fibers and meta-aramid fibrids is 2 mm. The weight ratio of nylon precipitated fibers is 1:2.

The preparation method of modified aramid fiber paper comprises the following steps:

The meta-aramid short-cut fibers and meta-aramid precipitated fibers are dispersed and water is added to prepare a slurry with a mass concentration of 0.1%; after ultrasonic treatment, the modified aramid fiber paper is made by a paper sheet forming machine, and the thickness of the aramid fiber paper is 0.05 mm; the ultrasonic treatment steps are 10 seconds each time, 3 seconds interval, and a total of 6 minutes of ultrasonic treatment; ultrasonic parameters: frequency is 10kHz, power is 500W.

The preparation method of composite material A1# comprises the following steps:

(1) unwinding two rolls of modified aramid fiber paper and coating adhesive on the surfaces of the two rolls;

(2) unwinding the modified mica paper, first laminating it on one of the modified aramid fiber papers coated with an adhesive, and then laminating another modified aramid fiber paper coated with an adhesive on the other side of the modified mica paper and drying it;

(3) The dried composite material A is subjected to hot roller hot pressing to finally obtain a corona-resistant mica/aramid fiber composite material A1# for new energy vehicles with a thickness of 0.25 mm.

Among them, the drying temperature is 120°C, the hot pressing temperature is 270°C, and the hot pressing pressure is 20MPa.

Example A2: Composite material A2#

Composite material A2# is prepared from the following raw materials in weight percentage: 50% modified aramid fiber paper, 10% adhesive and 40% modified mica paper, wherein the adhesive is FEP-fluorinated ethylene propylene copolymer (F46, tetrafluoroethylene and hexafluoropropylene copolymer).

The modified mica paper is prepared from the following raw materials: mica powder, hydrochloric acid solution, ethanol, silane coupling agent, methyl methacrylate, initiator and toluene; the mica powder is composed of a first mica powder, a second mica powder and a third mica powder, the particle size of the first mica powder is 110 μm, the particle size of the second mica powder is 150 μm, and the particle size of the third mica powder is 230 μm; the weight ratio of the first mica powder, the second mica powder and the third mica powder is 1:5:5 respectively; the weight ratio of the silane coupling agent to the mica powder is 0.08:1, and the weight ratio of the mica powder to the methyl methacrylate and the initiator is 1:0.15:0.005, the weight ratio of mica powder to ethanol and toluene is 1:8:8 respectively; the preparation method of modified mica paper comprises the following steps: adding silane coupling agent A171 to ethanol, adjusting the pH value to 4 with hydrochloric acid solution, adding mica powder, heating to 80°C and stirring for 3h, filtering, washing and drying, adding the mixture to toluene, adding methyl methacrylate and benzoyl peroxide at the same time, reacting at 90°C for 4h, filtering and drying at 130°C for 2h, adding water and stirring evenly to form a slurry with a mass concentration of 4%, and making the modified mica paper by a paper sheet forming machine. Mother paper.

The modified aramid fiber paper is prepared from meta-aramid chopped fibers and meta-aramid fibrils, the lengths of the meta-aramid chopped fibers and the meta-aramid fibrils are both 3 mm, and the weight ratio of the meta-aramid chopped fibers to the meta-aramid fibrils is 1:2.5; the preparation method of the modified aramid fiber paper comprises the following steps: the meta-aramid chopped fibers and the meta-aramid fibrils are dispersed and water is added to form a slurry with a mass concentration of 0.3%, and the modified aramid fiber paper is obtained by ultrasonic treatment through a paper sheet forming machine, and the thickness of the aramid fiber paper is 0.05 mm; the ultrasonic treatment step is 10 seconds each time, with an interval of 3 seconds, and a total ultrasonic treatment of 9 minutes; ultrasonic parameters: frequency is 20kHz, power is 500W.

The preparation method of composite material A2# comprises the following steps:

(3) The dried composite material A is hot-rolled and hot-pressed to finally obtain a corona-resistant mica/aramid fiber composite material A2# for new energy vehicles with a thickness of 0.25 mm.

Among them, the drying temperature is 120°C, the hot pressing temperature is 265°C, and the hot pressing pressure is 20MPa.

Example A3: Composite material A3#

The composite material A3# is prepared from the following raw materials in weight percentage: 60% of modified aramid fiber paper, 20% of adhesive and 40% of modified mica paper, wherein the adhesive is PFA-tetrafluoroethylene-perfluoroalkoxy vinyl ether copolymer.

The modified mica paper is prepared from the following raw materials: mica powder, hydrochloric acid solution, ethanol, silane coupling agent, methyl methacrylate, initiator and toluene; the mica powder is composed of a first mica powder, a second mica powder and a third mica powder, the particle size of the first mica powder is 100 μm, the particle size of the second mica powder is 140 μm, and the particle size of the third mica powder is 220 μm; the weight ratio of the first mica powder, the second mica powder and the third mica powder is 1:4:4 respectively; the weight ratio of the silane coupling agent to the mica powder is 0.06:1, and the mica powder The weight ratio of mica powder to methyl methacrylate and initiator is 1:0.12:0.003, and the weight ratio of mica powder to ethanol and toluene is 1:7:6. The preparation method of modified mica paper comprises the following steps: adding silane coupling agent A171 to ethanol, adjusting the pH value to 4 with hydrochloric acid solution, adding mica powder, heating to 70°C and stirring for 2h, filtering, washing and drying, adding the mixture to toluene, adding methyl methacrylate and benzoyl peroxide at the same time, reacting at 80°C for 3h, filtering and drying at 120°C After drying for 1 hour, water was added and stirred evenly to form a slurry with a mass concentration of 5%, and the slurry was processed by a paper sheet forming machine to obtain modified mica paper.

The modified aramid fiber paper is prepared from meta-aramid chopped fibers and meta-aramid fibrils, the lengths of the meta-aramid chopped fibers and the meta-aramid fibrils are both 2 mm, and the weight ratio of the meta-aramid chopped fibers to the meta-aramid fibrils is 1:2.2; the preparation method of the modified aramid fiber paper comprises the following steps: the meta-aramid chopped fibers and the meta-aramid fibrils are dispersed and water is added to form a slurry with a mass concentration of 0.5%, and the modified aramid fiber paper is obtained by ultrasonic treatment through a paper sheet forming machine, and the thickness of the aramid fiber paper is 0.05 mm; the ultrasonic treatment step is 10 seconds each time, with an interval of 3 seconds, and a total ultrasonic treatment of 7 minutes; ultrasonic parameters: frequency is 15kHz, power is 500W.

The preparation method of composite material A3# comprises the following steps:

(3) The dried composite material A is hot-rolled and hot-pressed to finally obtain a corona-resistant mica/aramid fiber composite material A3# for new energy vehicles with a thickness of 0.25 mm.

Among them, the drying temperature is 120°C, the hot pressing temperature is 310°C, and the hot pressing pressure is 20MPa.

Example A4: Composite material A4#

The difference between Example A4 and Example A1 is that the adhesive in Example A4 is a fluorinated ethylene propylene copolymer (F46, a copolymer of tetrafluoroethylene and hexafluoropropylene) and polyetheretherketone in a weight ratio of 3:1, which is the same as both.

Comparative Example A1: Comparative Composite Material A1#

The difference between Comparative Example A1 and Example A3 is that the adhesive in Comparative Example A1 is methyl etherified amino resin, and the rest are the same.

Comparative Example A2: Comparative Composite Material A2#

The difference between Comparative Example A2 and Example A3 is that the aramid fiber in Comparative Example A2 is not modified, and the rest is the same.

Comparative Example A3: Comparative Composite Material A3#

The difference between Comparative Example A3 and Example A3 is that the mica powder in Comparative Example A3 has a particle size of 50 μm and 90 μm. The weight ratio of the two mica powders is 1:3, and the rest are the same.

Comparative Example A4: Comparative Composite Material A4#

The difference between Comparative Example A4 and Example A3 is that the weight ratios of the first mica powder, the second mica powder and the third mica powder in Comparative Example A4 are 1:1.5:1.2 respectively, and the rest are the same.

Comparative Example A5: Comparative Composite Material A5#

The difference between Comparative Example A5 and Example A3 is that the weight ratio of the silane coupling agent to the mica powder in Comparative Example A5 is 0.12:1, and the rest are the same.

Comparative Example A6: Comparative Composite Material A6#

The difference between Comparative Example A6 and Example A3 is that in Comparative Example A6, only silane coupling agent KH550 is used to modify the mica powder, and the rest are the same.

Comparative Example A7: Comparative Composite Material A7#

The difference between Comparative Example A7 and Example A3 is that the aramid fiber used in Comparative Example A7 is para-aramid fibrid, and the rest are the same.

Comparative Example A8: Comparative Composite Material A8#

The difference between Comparative Example A8 and Example A3 is that the lengths of the intermediate aramid chopped fibers and the meta-aramid fibrids in Comparative Example A8 are both 5 mm, and the rest are the same.

Comparative Example A9: Comparative Composite Material A9#

The difference between Comparative Example A9 and Example A3 is that the weight ratio of the meso-aramid chopped fibers to the para-aramid fibrids in Comparative Example A9 is 1:1, and the rest are the same.

Comparative Example A10: Comparative Composite Material A10#

The difference between Comparative Example A10 and Example A3 is that the hot pressing molding temperature in Comparative Example A10 is 360° C., and the rest are the same.

Comparative Example A11: Comparative Composite Material A11#

Comparative Example A11 is pure meta-aramid fiber paper with a thickness of 0.25 mm.

Comparative Example A12: Comparative Composite Material A12#

Comparative Example A12 is a composite material A (commercially available material name NHN) prepared by using polyurethane as an adhesive and laminating 0.05 mm thick meta-aramid fiber paper on both sides of a polyimide film, with a thickness of 0.25 mm.

Experimental example

1. Electrical performance

Breakdown voltage: The test was carried out in accordance with the national standard GB/T1408.1-2006. The sample thickness was 0.25 mm. A Φ25 mm/Φ75 mm cylindrical electrode system was used. The test was repeated 5 times and the average value was taken.

PDIV (partial discharge initiation voltage): The test is carried out in accordance with the national standard GB/T 7354-2018, AC voltage frequency: 50hz; boost speed: 50V/s; partial discharge quantity 10PC is used as the starting discharge voltage point; experimental temperature: 21-25℃, humidity: 45-55%.

2. Temperature resistance test

Experimental method: The test was carried out in accordance with the national standard GB/T 4074.7-2009, and the three-point method was used to evaluate the heat resistance grade of the material.

3. Tensile strength

Experimental method: Determined in accordance with national standards GB/T 20629.2-2013 and GB/T 5591.2-2017.

4. Square wave corona resistance life

Experimental method: The test was carried out in accordance with T/CEEIA 415-2019 standard. Test conditions: peak-to-peak voltage Vp-p = 3000V, temperature 155±3℃, frequency = 20KHz, rising edge 100±10ns, duty cycle 50%.

Composite materials A1#-4# and comparative composite materials A1#-12# were sampled and tested for the above four tests. The experimental results are shown in Table 1.

It can be seen from the above experimental data that the composite materials A1#-4# prepared by the raw materials and methods specified in this application have good electrical properties, long square wave corona resistance life, excellent high temperature resistance and excellent mechanical properties.

The comparison composite material A1# used a commonly used adhesive on the market, and the final result was average electrical performance and average high temperature resistance; in the comparison composite material A2#, the aramid fiber was not modified, and the final result was average electrical performance. The reason for this was analyzed to be that the aramid fiber was relatively inert and had poor interface bonding with other matrix materials.

In comparison, the particle size of mica powder in composite material A3# is smaller than the range specified in this application. The final result is that the electrical performance is average and the breakdown voltage is low. The reason is analyzed as follows: mica with small particle size will produce more mica fragments, most of which act as "mud and sand" components when added to paper. The irregular arrangement leads to loose paper structure, increased thickness, damaged paper mixed structure, decreased mechanical properties of paper, and increased porosity of paper. When the paper is subjected to external voltage, the electron beam is more likely to cause breakdown of the paper due to the reduction of the high insulation barrier of large pieces of mica in the Z direction.

In comparison, the proportion of small and medium-sized mica powder in the composite material A4# exceeds the range specified in this application, and the final electrical performance is average. The reason is analyzed as follows: as the amount of mica with smaller particles increases, the integrity of the mica layer is destroyed, the size of the longitudinal structure increases, the number of fine particles increases and gradually accumulates, the arrangement of mica sheets also changes from flat to oblique, and the mechanical properties decrease; at the same time, due to the damage of the mica layer structure, the small-particle mica with a large proportion appears granular, and the accumulation of particles produces a large number of pores, which limits the insulating effect of mica. When the paper is subjected to electrical breakdown, the current is less obstructed and the current channel is shorter, resulting in a decrease in the overall insulation performance of the paper.

In comparison, the ratio of silane coupling agent to mica powder in composite material A5# exceeds the range specified in this application, and the final electrical performance is average. The reason is analyzed as follows: excessive amount of coupling agent will reduce the coupling efficiency due to condensation reaction, the grafting rate is low, and the modification effect is poor. Small amount of coupling agent will result in less coupling agent grafted on the surface.

In contrast, in composite material A6#, only silane coupling agent was used to modify mica powder. The final electrical performance was average. The reason was analyzed to be that the dispersion performance was still limited after modification, and the interface bonding performance with other materials was not high.

The composite material A7# uses para-aramid fiber precipitation, which has good mechanical properties, but poor electrical properties. The gas performance is average. The reason is that the para-molecular structure has excellent mechanical properties, but its electrical properties are poorer than those of the meta-structure. At the same time, its precipitated fibers have poor coating properties on short-cut fibers.

The fiber length used in the comparative composite material A8# exceeds the range specified in this application, and the final electrical performance is average. The reason is analyzed as follows: the lengthening of the fibers increases the probability of entanglement between the fibers, making them difficult to disperse, increasing the unevenness of the hot-pressed composite paper, and further affecting the overall strength of the paper.

The ratio of precipitated fibers to chopped fibers used in the comparative composite material A9# is smaller than the range specified in the present application, and the final electrical performance is average. The reason for this is that the chopped fibers are interspersed in the paper structure, which easily leads to the formation of pores in the paper. The small ratio of precipitated fibers results in poor bonding with the chopped fibers, making it difficult to exert their electrical and thermal properties.

The hot pressing molding temperature of the comparative composite material A10# was higher than the range specified in this application, and the final electrical performance was average. The reason was that the high temperature caused the raw materials to age and the bonding force between the aramid fiber and the precipitated fiber decreased. The comparative composite materials A11#-12# were common composite materials A on the market, with average high temperature resistance and short corona resistance life.

Next, in conjunction with FIG. 2 , a second mica/aramid fiber composite material according to the present application is introduced.

Example B1: Mixed Paper 1#

Mixed paper 1# is prepared from the following raw materials: modified aramid fiber, adhesive and modified mica powder; the weight ratio of modified aramid fiber to modified mica powder is 0.1:1, the added amount of adhesive is 5% of the total weight of modified aramid fiber and modified mica powder, and the adhesive is PFA-tetrafluoroethylene-perfluoroalkoxy vinyl ether copolymer.

Among them, the modified mica powder is prepared from the following raw materials: mica powder, hydrochloric acid solution, ethanol, silane coupling agent, methyl methacrylate, initiator and toluene. The mica powder is composed of the first mica powder, the second mica powder and the third mica powder. The particle size of the first mica powder is 90μm, the particle size of the second mica powder is 130μm, and the particle size of the third mica powder is 200μm. The weight ratio of the first mica powder, the second mica powder and the third mica powder is 1:3:3. The weight ratio of the silane coupling agent to the mica powder is 0.05:1, the weight ratio of the mica powder to methyl methacrylate and the initiator is 1:0.1:0.002, and the weight ratio of the mica powder to ethanol and toluene is 1:6:5.

The preparation method of modified mica powder comprises the following steps:

Add silane coupling agent A171 to ethanol and adjust the pH value to 4 using hydrochloric acid solution;

Add mica powder, heat to 60℃ and stir for 1h, filter, wash and dry;

The mixture was then added to toluene, and methyl methacrylate and benzoyl peroxide were added at the same time, and the mixture was reacted at 70°C for 2 hours. After filtering, the mixture was dried at 110°C for 0.5 hours to obtain the modified mica powder.

The modified aramid fiber is prepared from meta-aramid chopped fibers and meta-aramid fibrils, the lengths of the meta-aramid chopped fibers and the meta-aramid fibrils are both 2 mm, and the weight ratio of the meta-aramid chopped fibers to the meta-aramid fibrils is 1:2.

The preparation method of modified aramid fiber comprises the following steps:

The meta-aramid short fibers and the meta-aramid fibrids are dispersed to form a slurry;

The modified aramid fiber was obtained by drying after ultrasonic treatment; the ultrasonic treatment steps were 10 seconds each time, 3 seconds interval, and a total of 6 minutes of ultrasonic treatment; the ultrasonic parameters were: frequency of 10 kHz and power of 500 W.

The preparation method of mixed paper 1# comprises the following steps:

(1) mixing the modified mica powder with water to prepare a slurry with a mass concentration of 2%, and mixing the modified aramid fiber with water to prepare a slurry with a mass concentration of 0.2%;

(2) mixing and stirring the modified mica powder slurry, the modified aramid fiber slurry and the adhesive evenly;

(3) The mixed slurry is added to a paper sheet former for forming, pressed and dried, and then hot-pressed by a hot roller to finally obtain corona-resistant mica/aramid fiber mixed paper 1# for new energy vehicles with a thickness of 0.25 mm.

Among them, the pressing time is 5 minutes, the pressure is 300 kPa; the hot pressing temperature is 310°C, and the hot pressing pressure is 20 MPa.

Example B2: Mixed Paper 2#

Mixed paper 2# is prepared from the following raw materials: modified aramid fiber, adhesive and modified mica powder; the weight ratio of modified aramid fiber to modified mica powder is 0.5:1, the added amount of adhesive is 10% of the total weight of modified aramid fiber and modified mica powder, and the adhesive is FEP-fluorinated ethylene propylene copolymer (F46, tetrafluoroethylene and hexafluoropropylene copolymer).

The modified mica powder is prepared from the following raw materials: mica powder, hydrochloric acid solution, ethanol, silane coupling agent, methyl methacrylate, initiator and toluene; the mica powder is composed of a first mica powder, a second mica powder and a third mica powder, the particle size of the first mica powder is 110 μm, the particle size of the second mica powder is 150 μm, and the particle size of the third mica powder is 230 μm; the weight ratio of the first mica powder, the second mica powder and the third mica powder is 1:5:5 respectively; the weight ratio of the silane coupling agent to the mica powder is 0.08:1, and the mica powder The weight ratio of mica powder to methyl methacrylate and initiator is 1:0.15:0.005, and the weight ratio of mica powder to ethanol and toluene is 1:8:8. The preparation method of modified mica powder comprises the following steps: adding silane coupling agent A171 to ethanol, adjusting the pH value to 4 with hydrochloric acid solution, adding mica powder, heating to 80°C and stirring for 3h, filtering, washing and drying, adding the mixture to toluene, adding methyl methacrylate and benzoyl peroxide at the same time, reacting at 90°C for 4h, filtering and drying at 130°C The modified mica powder was obtained after drying for 2 hours.

The modified aramid fiber is prepared from meta-aramid chopped fibers and meta-aramid fibrils, the lengths of the meta-aramid chopped fibers and the meta-aramid fibrils are both 3 mm, and the weight ratio of the meta-aramid chopped fibers to the meta-aramid fibrils is 1:2.5; the preparation method of the modified aramid fiber comprises the following steps: the meta-aramid chopped fibers and the meta-aramid fibrils are dispersed to form a slurry, and the slurry is dried after ultrasonic treatment to obtain the modified aramid fiber; the ultrasonic treatment step is 10 seconds each time, with an interval of 3 seconds, and a total ultrasonic treatment of 9 minutes; ultrasonic parameters: frequency is 20 kHz, and power is 500 W.

The preparation method of mixed paper 2# comprises the following steps:

(1) mixing the modified mica powder with water to prepare a slurry with a mass concentration of 2%, and mixing the modified aramid fiber with water to prepare a slurry with a mass concentration of 1%;

(3) The mixed slurry is added to a paper sheet former for forming, pressed and dried, and then hot-pressed with a flat press to finally obtain corona-resistant mica/aramid fiber mixed paper 2# for new energy vehicles with a thickness of 0.25 mm.

Among them, the pressing time is 5 minutes, the pressure is 300kPa; the hot pressing temperature is 265°C, and the hot pressing pressure is 20MPa.

Example B3: Mixed Paper 3#

Mixed paper 3# is prepared from the following raw materials: modified aramid fiber, adhesive and modified mica powder; the weight ratio of modified aramid fiber to modified mica powder is 0.3:1, the added amount of adhesive is 8% of the total weight of modified aramid fiber and modified mica powder, and the adhesive is PFA-tetrafluoroethylene-perfluoroalkoxy vinyl ether copolymer.

The modified mica powder is prepared from the following raw materials: mica powder, hydrochloric acid solution, ethanol, silane coupling agent, methyl methacrylate, initiator and toluene; the mica powder is composed of a first mica powder, a second mica powder and a third mica powder, the particle size of the first mica powder is 100 μm, the particle size of the second mica powder is 140 μm, and the particle size of the third mica powder is 220 μm; the weight ratio of the first mica powder, the second mica powder and the third mica powder is 1:4:4 respectively; the weight ratio of the silane coupling agent to the mica powder is 0.06:1, and the weight ratio of the mica powder to the methyl methacrylate is 0.06:1. The weight ratio of methyl ester and initiator is 1:0.12:0.003, and the weight ratio of mica powder to ethanol and toluene is 1:7:6. The preparation method of modified mica powder comprises the following steps: adding silane coupling agent A171 to ethanol, adjusting the pH value to 4 with hydrochloric acid solution, adding mica powder, heating to 70°C and stirring for 2h, filtering, washing and drying, adding the mixture to toluene, adding methyl methacrylate and benzoyl peroxide at the same time, reacting at 80°C for 3h, filtering and drying at 120°C for 1h to obtain modified mica powder.

The modified aramid fiber is prepared from meta-aramid chopped fibers and meta-aramid fibrils, the lengths of the meta-aramid chopped fibers and the meta-aramid fibrils are both 2 mm, and the weight ratio of the meta-aramid chopped fibers to the meta-aramid fibrils is 1:2.2; the preparation method of the modified aramid fiber comprises the following steps: the meta-aramid chopped fibers and the meta-aramid fibrils are dispersed to form a slurry, and the slurry is dried after ultrasonic treatment to obtain the modified aramid fiber; the ultrasonic treatment step is 10 seconds each time, with an interval of 3 seconds, and a total ultrasonic treatment of 7 minutes; ultrasonic parameters: frequency is 15 kHz, and power is 500 W.

The preparation method of mixed paper 3# comprises the following steps:

(1) mixing the modified mica powder with water to prepare a slurry with a mass concentration of 2%, and mixing the modified aramid fiber with water to prepare a slurry with a mass concentration of 0.4%;

(3) The mixed slurry is added to a paper sheet former for forming, pressed and dried, and then hot-pressed with a flat press to finally obtain corona-resistant mica/aramid fiber mixed paper 3# for new energy vehicles with a thickness of 0.25 mm.

Among them, the pressing time is 5 minutes, the pressure is 300 kPa; the hot pressing temperature is 302°C, and the hot pressing pressure is 20 MPa.

Example B4: Mixed Paper 4#

The difference between Example B4 and Example B1 is that the adhesive in Example B4 is FEP-fluorinated ethylene propylene copolymer (F46, tetrafluoroethylene and hexafluoropropylene copolymer) and PEEK-polyetheretherketone, the weight ratio is 3:1, and the rest are the same.

Comparative Example B1: Comparative Mixed Paper 1#

The difference between Comparative Example B1 and Example B3 is that the adhesive in Comparative Example B1 is methyl etherified amino resin, and the rest are the same.

Comparative Example B2: Comparative Mixed Paper 2#

The difference between Comparative Example B2 and Example B3 is that the aramid fiber in Comparative Example B2 is not modified, and the rest is the same.

Comparative Example B3: Comparative Mixed Paper 3#

The difference between Comparative Example B3 and Example B3 is that the weight ratio of the modified aramid fiber to the modified mica powder in Comparative Example B3 is 1.2:1, and the rest are the same.

Comparative Example B4: Comparative Mixed Paper 4#

The difference between Comparative Example B4 and Example B3 is that the mica powder in Comparative Example B4 has a particle size of 50 μm and 90 μm. The weight ratio of the two mica powders is 1:3, and the rest are the same.

Comparative Example B5: Comparative Mixed Paper 5#

The difference between Comparative Example B5 and Example B3 is that the weight ratios of the first mica powder, the second mica powder and the third mica powder in Comparative Example B5 are 1:1.5:1.2 respectively, and the rest are the same.

Comparative Example B6: Comparative Mixed Paper 6#

The difference between Comparative Example B6 and Example B3 is that the weight ratio of the silane coupling agent to the mica powder in Comparative Example B6 is 0.12:1, and the rest are the same.

Comparative Example B7: Comparative Mixed Paper 7#

The difference between Comparative Example B7 and Example B3 is that in Comparative Example B7, only silane coupling agent KH550 is used to modify the mica powder, and the rest are the same.

Comparative Example B8: Comparative Mixed Paper 8#

The difference between Comparative Example B8 and Example B3 is that the aramid fiber used in Comparative Example B8 is para-aramid fibrid, and the rest are the same.

Comparative Example B9: Comparative Mixed Paper 9#

The difference between Comparative Example B9 and Example B3 is that the lengths of the intermediate aramid chopped fibers and the meta-aramid fibrids in Comparative Example B9 are both 5 mm, and the rest are the same.

Comparative Example B10: Comparative Mixed Paper 10#

The difference between Comparative Example B10 and Example B3 is that the weight ratio of the meso-aramid chopped fibers to the meta-aramid fibrids in Comparative Example B10 is 1:1, and the rest are the same.

Comparative Example B11: Comparative Mixed Paper 11#

The difference between Comparative Example B11 and Example B3 is that the hot pressing molding temperature in Comparative Example B11 is 380° C., and the rest are the same.

Comparative Example B12: Meta-aramid Fiber Paper

Comparative Example B12 is commercially available meta-aramid fiber paper, pure paper, with a thickness of 0.25 mm.

Experimental example

1. Electrical performance

Breakdown voltage: The test was carried out in accordance with the national standard GB/T1408.1 2006. The sample thickness was 0.25 mm. A Φ25 mm/Φ75 mm cylindrical electrode system was used. The test was repeated 5 times and the average value was taken.

2. Temperature resistance test

3. Tensile strength

Square wave corona resistance life

Composite materials B1#-4#, comparative composite materials B1#-11#, and meta-aramid fiber paper were sampled and tested for the above four tests. The experimental results are shown in Table 2.

Table 2

From the above experimental data, it can be seen that the mixed paper 1#-4# prepared by the raw materials and methods specified in this application has good electrical properties, long square wave corona resistance life, excellent high temperature resistance and excellent mechanical properties.

The comparison mixed paper 1# used a commonly used adhesive on the market, and the final result was average electrical properties and average high temperature resistance; the comparison mixed paper 2# did not modify the aramid fiber, and the final result was average electrical properties. The reason was analyzed as the aramid fiber is relatively inert and has poor interface bonding with the matrix material.

In contrast, the ratio of modified aramid fiber to modified mica powder in mixed paper 3# exceeds the range specified in this application, and the final electrical performance is average. The reason is analyzed to be that the combination of aramid fiber and mica has been saturated, and excessive fibers accumulate in the gaps formed by mica scales or on the surface of the scales, causing the paper thickness to increase, resulting in uneven distribution of the electric field in the paper structure, generating a large amount of heat that cannot be dissipated, resulting in a decrease in the breakdown field strength.

In contrast, the particle size of mica powder in mixed paper 4# is smaller than the range specified in this application, and the final electrical performance is average. The reason is analyzed as follows: mica with small particle size will produce more mica fragments, most of which act as "silt" components when added to paper. The irregular arrangement leads to a decrease in the fit between mica and fiber, a loose paper structure, increased thickness, damaged paper mixed structure, and a decrease in paper mechanical properties. At the same time, the porosity of the paper increases. When the paper is subjected to external voltage, the electron beam is more likely to cause breakdown of the paper due to the reduction of the high insulation barrier of large pieces of mica in the Z direction.

In contrast, the proportion of small and medium-sized mica powder in mixed paper 5# exceeds the range specified in this application, and the final electrical performance is average. The reason is analyzed as follows: as the amount of mica with smaller particles increases, the integrity of the mica layer is destroyed, the size of the longitudinal structure increases, the number of fine particles increases and gradually accumulates, and the arrangement of mica sheets also changes from flat to oblique, resulting in poor bonding between fibers and mica and decreased mechanical properties; at the same time, due to the damage of the mica layer structure, the small-particle mica with a large proportion is granular, and the accumulation of particles produces a large number of pores, which limits the insulating effect of mica. When the paper is subjected to electrical breakdown, the current is less obstructed and the current channel is shorter, resulting in a decrease in the overall insulation performance of the paper.

The ratio of silane coupling agent to mica powder in mixed paper 6# exceeds the range specified in this application, and the final electrical performance is average. The reason is that the excessive amount of coupling agent reduces the coupling efficiency due to condensation reaction, and the grafting rate is low. The modification effect is poor, and the smaller the amount of coupling agent used, the less coupling agent is grafted on the surface.

In contrast, in mixed paper 7#, only silane coupling agent was used to modify the mica powder. The final electrical performance was average. The reason was analyzed to be that the dispersion performance was still limited after modification, and the interface bonding strength with other materials was not high.

In contrast, para-aramid fibrils are used in mixed paper 8#, and the final result shows good mechanical properties, but average electrical properties. The reason is that the para-molecular structure shows excellent mechanical properties, but the electrical properties are poorer than those of the meta-structure. At the same time, the fibrils have poor coating properties on short-cut fibers.

The fiber length used in the mixed paper 9# exceeds the range specified in this application, and the final electrical performance is average. The reason is analyzed to be that the lengthening of the fibers increases the probability of entanglement between the fibers, making them difficult to disperse, increasing the unevenness of the hot-pressed composite paper, and thus affecting the overall strength of the paper.

In contrast, the ratio of precipitated fibers to chopped fibers used in mixed paper 10# is smaller than the range specified in the present application, and the final electrical performance is average. The reason is analyzed to be that the chopped fibers have no bonding force with mica. At the same time, the chopped fibers have a relatively large thickness relative to mica, and are interspersed in the paper structure, which has a certain degree of damage to the bonding between precipitated fibers and mica, resulting in easy formation of pores in the paper. A small ratio of precipitated fibers will result in poor bonding between the chopped fibers and mica, making it difficult to exert their electrical and thermal properties.

The hot pressing molding temperature of the mixed paper 11# was higher than the range specified in this application, and the final result had average electrical properties. The reason for this was that the high temperature caused the raw materials to age, and the bonding force between the aramid fiber, precipitated fiber and mica powder decreased. The meta-aramid fiber paper of comparative example B12 did not contain mica components, and the final result had average electrical properties and average high temperature resistance, but good mechanical properties.

The above is only the embodiment of the present application, and the protection scope of the present application is not limited by these specific embodiments, but is determined by the claims of the present application. For those skilled in the art, the present application can have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the technical ideas and principles of the present application should be included in the protection scope of the present application.

Claims

A corona-resistant mica/aramid fiber composite material for new energy vehicles, characterized in that:

The raw materials for preparing the composite material include: modified aramid fiber material, adhesive and modified mica material;

The adhesive comprises one or more of tetrafluoroethylene-perfluoroalkoxy vinyl ether copolymer, fluorinated ethylene propylene copolymer, ethylene-tetrafluoroethylene copolymer, polyetheretherketone and polyetherimide;

The modified mica material is prepared from the following raw materials: mica powder, hydrochloric acid solution, ethanol, silane coupling agent, methyl methacrylate, initiator and toluene; the mica powder consists of a first mica powder, a second mica powder and a third mica powder, the particle size of the first mica powder is 90-110 μm, the particle size of the second mica powder is 130-150 μm, and the particle size of the third mica powder is 200-230 μm; the weight ratio of the first mica powder, the second mica powder and the third mica powder is 1:(3-5):(3-5) respectively.
The corona-resistant mica/aramid fiber composite material for new energy vehicles according to claim 1, characterized in that 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 to methyl methacrylate and the initiator is 1:(0.1-0.15):(0.002-0.005) respectively, and the weight ratio of the mica powder to ethanol and toluene is 1:(6-8):(5-8) respectively.
The corona-resistant mica/aramid fiber composite material for new energy vehicles according to claim 2, characterized in that the preparation method of the modified mica material comprises the following steps:

S11, adding silane coupling agent to ethanol, adjusting pH value to 4 with hydrochloric acid solution,

S12, add mica powder, heat to 60-80℃, stir for 1-3h, filter, wash and dry.

S13, adding the mixture into toluene, adding methyl methacrylate and an initiator at the same time, reacting at 70-90° C. for 2-4 hours, filtering and drying at 110-130° C. for 0.5-2 hours.
The corona-resistant mica/aramid fiber composite material for new energy vehicles according to claim 3, characterized in that the silane coupling agent is A171 and the initiator is benzoyl peroxide.
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 prepared from meta-aramid chopped fibers and meta-aramid fibrils, the lengths of the meta-aramid chopped fibers and the meta-aramid fibrils are both 2-3 mm, and the weight ratio of the meta-aramid chopped fibers to the meta-aramid fibrils is 1:(2-2.5).
The corona-resistant mica/aramid fiber composite material for new energy vehicles according to claim 5, characterized in that the preparation method of the modified aramid fiber material comprises the following steps:

S21, dispersing the meta-aramid chopped fibers and the meta-aramid fibrids to form a slurry,

S22, subjecting the slurry to ultrasonic treatment.
The corona-resistant mica/aramid fiber composite material for new energy vehicles according to claim 6, characterized in that the ultrasonic treatment step is 10 seconds per ultrasonic treatment, with an interval of 3 seconds, and a total ultrasonic treatment of 6-9 minutes; the ultrasonic parameters are: frequency of 10-20kHz, power of 500W.
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 modified aramid fiber material is modified aramid paper, the modified mica material is modified mica paper,

The weight percentages of the raw materials are: 40-60% of modified aramid fiber paper, 5-20% of adhesive and 40-60% of modified mica paper.
The corona-resistant mica/aramid fiber composite material for new energy vehicles according to claim 3 is characterized in that the modified aramid fiber material is modified aramid paper, the modified mica material is modified mica paper, the weight percentages of the raw materials are: 40-60% of modified aramid fiber paper, 5-20% of adhesive and 40-60% of modified mica paper, and the preparation method of the modified mica material further includes: S14, adding water and stirring evenly to form a slurry, and the modified mica paper is obtained by papermaking through a paper sheet forming machine.
The corona-resistant mica/aramid fiber composite material for new energy vehicles according to claim 6, characterized in that the modified aramid fiber material is modified aramid paper, the modified mica material is modified mica paper, and the weight percentages of the raw materials are: 40-60% of modified aramid fiber paper, 5-20% of adhesive and 40-60% of modified mica paper,

The method for preparing the modified aramid fiber material further comprises: S23, papermaking the modified aramid fiber paper through a paper sheet forming machine.
A method for preparing a corona-resistant mica/aramid fiber composite material for new energy vehicles as claimed in any one of claims 8 to 10, characterized in that it comprises the following steps:

S01, unwinding two rolls of modified aramid fiber paper and coating adhesive on the surfaces thereof respectively;

S02, unwinding the modified mica paper, first laminating it on one of the modified aramid fiber papers coated with an adhesive, and then laminating another modified aramid fiber paper coated with an adhesive on the other side of the modified mica paper and drying it;

S03, subjecting the dried composite material to hot rolling and hot pressing, and finally obtaining a corona-resistant mica/aramid fiber composite material for new energy vehicles.
The corona-resistant mica/aramid fiber composite for new energy vehicles according to any one of claims 1 to 7 The material is characterized in that the modified aramid fiber material is modified aramid fiber, the modified mica material is modified mica powder,

The weight ratio of the modified aramid fiber to the modified mica powder is (0.1-0.5):1, and the added amount of the adhesive is 5-10% of the total weight of the modified aramid fiber and the modified mica powder.
A method for preparing a corona-resistant mica/aramid fiber composite material for new energy vehicles as claimed in claim 12, characterized in that it comprises the following steps:

S01, mixing modified mica powder with water to prepare a slurry with a mass concentration of 2-10%, and mixing modified aramid fiber with water to prepare a slurry with a mass concentration of 0.1-1%;

S02, mixing and stirring the modified mica powder slurry, the modified aramid fiber slurry and the adhesive evenly;

S03, adding the mixed pulp into a paper sheet former to form it, drying it after pressing, and then hot-pressing it with a hot roller to finally obtain a corona-resistant mica/aramid fiber mixed paper for new energy vehicles.
The preparation method according to claim 13 is characterized in that in the step S03, the drying temperature is 120°C, the hot pressing temperature is 265-310°C, and the hot pressing pressure is 20MPa.