CN115044079B - Aramid fiber nanofiber doped basalt nanosheet composite insulating film and preparation method thereof - Google Patents

Abstract

The invention provides an aramid nanofiber-doped basalt nanosheet composite insulating film and a preparation method thereof, wherein basalt flakes with low price are used as raw materials, and the basalt flakes are treated by a chemical method combined with a mechanical method to prepare basalt nanosheets; in addition, the chemical method is adopted to carry out nanocrystallization treatment on para-aramid chopped fibers to prepare the aramid nanofibers. And then the basalt nano-sheets are doped in the aramid nano-fibers and then the aramid nano-fibers are subjected to suction filtration to form a film to prepare the insulating film, so that the blank in the application field of the basalt nano-sheets and the technical field of insulating materials at present can be filled. The aramid nanofiber doped basalt nanosheet composite insulating film prepared by the method has excellent insulating property and high temperature resistance, and is high in strength, so that the aramid nanofiber doped basalt nanosheet composite insulating film has a strong development prospect in the field of electric industry. The preparation method is simple and effective, the raw materials are low, the preparation method is simple and easy to operate, large-scale equipment is not needed, industrialization is easy to realize, and the possibility of industrialized mass production is improved.

Description

Aramid fiber nanofiber doped basalt nanosheet composite insulating film and preparation method thereof

technical field

The invention belongs to the technical field of insulating materials, and in particular relates to a composite insulating film doped with aramid fiber nanofibers and basalt nanosheets and a preparation method thereof.

Background technique

Electrical insulating material is a kind of electrical material prepared from organic or inorganic materials with high insulating properties through different forming methods. Because of its high insulating properties, it can block high voltage and effectively protect the safety and stability of electrical equipment. It is widely used in electrical fields such as power transmission cables, traction motors, and high-voltage generators. Electrical insulating materials are classified differently according to different standards. According to the different preparation raw materials, it can be divided into organic insulating materials and inorganic insulating materials. Common organic insulating materials include plastic polyesters, resins, fibers, etc., and inorganic insulating materials include glass, asbestos, ceramics, mica, etc. According to the way in which insulating materials exist, they can be divided into three types: solid, liquid, and gas. Common solid insulating materials include fiber insulating paper, mica products, plastic products, and composite films.

In recent years, with the rapid development of the electrical industry, the industry has been continuously transformed and upgraded, and power generation and transportation, electrical equipment, etc. have gradually developed towards ultra-high voltage and ultra-high voltage. Insulation material performance and environmental adaptability pose a greater test. Basalt scale is a new type of scale material. It is a new type of material processed by selecting natural basalt ore with excellent performance through special processes such as high-temperature melting, clarification, homogenization, and screening. It presents a transparent or dark green sheet structure, and its thickness is generally between About 3 μm, the size is generally between 25 μm and 3mm. Due to the high content of iron oxide, titanium dioxide, aluminum oxide, and calcium oxide in basalt scales, and the low content of alkaline oxides, basalt scales can not only produce a shielding effect, but also have unique advantages in acid and alkali resistance and corrosion resistance. And basalt flakes have good corona resistance and insulation properties. As an important member of high-performance fibers, aramid nanofibers have excellent properties such as high strength and high modulus, good toughness, light weight, acid and alkali resistance, and also have excellent insulation properties and high temperature resistance. Insulation film with high strength and high electrical breakdown strength. However, at this stage, there are few studies on composite insulating films prepared by doping aramid nanofibers with basalt nanosheets in this field. Technology gaps in the industry.

Contents of the invention

Aiming at the problems existing in the prior art, the present invention provides a simple and feasible method for preparing aramid nanofiber-doped basalt nanosheet composite insulating film, so as to fill up the current technical gap in the industry. The present invention uses basalt scales as raw materials, and the Preliminary surface etching to remove part of the metal oxides and impurities on the surface to form a rough structure on the surface, and then use cations with smaller atomic radius to enter the interior of the basalt scales and perform ion exchange with K ⁺ , Na ⁺ , Ca ²⁺ plasma , so that more cavities are formed inside the basalt scales, and then cavitation occurs through mechanical force, so that the basalt scales form a multi-sheet structure, and finally fall off to form basalt nano-sheets. In addition, aramid nanofibers were prepared by passing para-aramid chopped fibers through a potassium hydroxide system. Finally, the insulating film was prepared by mixing aramid nanofibers and basalt nanosheets.

The present invention is achieved through the following technical solutions:

A method for preparing aramid nanofiber doped basalt nanosheet composite insulating film, characterized in that it comprises the following steps:

(1) Preparation of basalt nanosheets: place basalt scales in hydrochloric acid solution, stir at a set temperature for surface etching reaction, and perform suction filtration and washing to neutrality after the reaction to obtain preliminary surface etched basalt scales ; Place the basalt scales etched on the preliminary surface in lithium chloride solution, carry out stirring reaction at a set temperature, and carry out suction filtration and washing to obtain cation-exchanged basalt scales after the completion of the reaction; the cation-exchanged basalt scales The scales are prepared into a mixed suspension, and then subjected to ultrasonic pulverization, then left to stand, and the upper layer of turbid liquid is taken out, and dried to obtain basalt nanosheets A;

(2) Surface modification of basalt nanosheets: the basalt nanosheets A prepared in step (1) are stirred and reacted with polyvinylpyrrolidone solution, and the surface of basalt nanosheets is modified to obtain basalt nanosheets containing carbonyl groups on the surface B;

(3) Preparation of aramid nanofibers: Stir the para-aramid chopped fibers with potassium hydroxide, dimethyl sulfoxide, and deionized water at room temperature, and add an appropriate amount of deionized water at a uniform speed after the reaction is completed. Protonation reduction, and repeated washing with deionized water and absolute ethanol until no excess dimethyl sulfoxide remains, and aramid nanofibers are obtained.

(4) Preparation of insulating film: Mix the basalt nanosheets B containing carbonyl groups on the surface obtained in step (2) with the aramid nanofibers in step (3) and then filter to form a film. After drying, aramid nanofibers doped Heterobasalt nanosheet composite insulating film.

Preferably, the dosage ratio of basalt flakes and hydrochloric acid solution in the step (1) is 0.4g:30mL, the concentration of hydrochloric acid is 4moL/L, the reaction temperature in water bath is 80°C, and the reaction time is 24h.

Preferably, the concentration of the lithium chloride solution in the step (1) is 0.5mol/L~3mol/L, and the dosage ratio of the initially etched basalt scales and the lithium chloride solution is 1.0g:50mL~200mL. The temperature of the cation exchange reaction was 110° C., the stirring rate was 1000 rpm, and the reaction time was 8 h.

Preferably, the mass ratio of cation-exchanged basalt scales to water in the mixed suspension in the step (1) is 0.1g:50mL~200mL, and the dispersion and pulverization in the step (3) uses a cell pulverizer, and the cells The power of the pulverizer is 600W~1000W, the dispersion time is 60min, and the standing time is 24h.

Preferably, the mass ratio of basalt nanosheets A to polyvinylpyrrolidone in the step (2) is 1:5-20, and the reaction temperature is room temperature.

Preferably, in the step (3), the ratio of para-aramid chopped aramid fiber to potassium hydroxide and dimethyl sulfoxide is 1g: 1.5g: 500mL; the step (3) deprotonation reaction The amount of deionized water in the medium is 200mL.

Preferably, a method for preparing aramid nanofiber doped basalt nanosheet composite insulating film according to claim 1, characterized in that the amount of basalt nanosheet B added in the step (4) is aramid fiber 1.0wt%~10wt% of the solid content of nanofibers;

Preferably, the mixing methods in the step (4) are magnetic stirring, mechanical stirring, and ball milling; the stirring rate of the magnetic stirring and mechanical stirring is 500rpm~1500rpm, and the stirring time is 0.5~2h; the ball milling The time is 10min~30min.

A method for preparing aramid nanofiber doped basalt nanosheet composite insulating film, which is prepared by the above preparation method.

Preferably, the electrical breakdown strength of the aramid nanofiber-doped basalt nanosheet composite insulating film is 73.30kV/mm-92.42kV/mm.

Compared with the prior art, the present invention has the following beneficial technical effects:

The invention provides an aramid nanofiber doped basalt nanosheet composite insulating film and a preparation method thereof, which uses cheap basalt scales as a raw material, performs preliminary surface etching with hydrochloric acid, and removes some metal oxides and impurities on the surface, so that The rough structure is formed on the surface, and then the cations with smaller atomic radius enter the interior of the basalt scales to perform ion exchange with the K ⁺ , Na ⁺ , and Ca ²⁺ ions in them, so that more cavities are formed inside the basalt scales, and then through mechanical force. The cavitation effect occurs, so that the basalt scales form a multi-layer structure, and finally fall off to form basalt nano-sheets; in addition, the para-aramid chopped fibers are nano-treated to obtain aramid nano-fibers. Afterwards, the aramid fiber nanofibers will be doped with basalt nanosheets and then filtered to form an insulating film, which can fill the gap in the field of preparation and application of basalt nanosheets. The doped basalt nanosheet insulating film prepared by the invention has excellent insulation performance, high temperature resistance and high strength, so that it has a strong development prospect in the field of electric industry.

Further, the present invention applies basalt nanosheets to the technical field of insulating materials for the first time, which enriches the field of preparation of insulating materials.

Further, the present invention adopts a simple and effective preparation method to prepare aramid nanofiber doped basalt nanosheet composite insulating film, the raw material is cheap, the preparation method is simple and easy to operate, no large-scale equipment is required, industrialization is relatively easy to realize, and the possibility of industrialized mass production is improved sex.

Description of drawings

Fig. 1 is the surface topography figure of the basalt nanosheets that make in embodiment 1,3,5,9;

Fig. 2 is a surface topography diagram of the pure aramid nanofiber film and the aramid nanofiber-doped basalt nanosheet composite insulating film prepared in Examples 6 and 7 after electrical breakdown.

Detailed ways

The present invention will be further described in detail below in conjunction with specific embodiments, which are explanations of the present invention rather than limitations.

It should be noted that the following detailed description is exemplary and intended to provide further explanation of the present invention. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

It should be noted that the terminology used here is only for describing specific embodiments, and is not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly dictates otherwise, the singular is intended to include the plural, and it should also be understood that when the terms "comprising" and/or "comprising" are used in this specification, they mean There are features, steps, operations, means, components and/or combinations thereof.

Embodiments of the present invention are described in further detail below:

(1) Preparation of basalt nanosheets: Weigh a certain amount of basalt flakes and place them in a three-neck flask, add hydrochloric acid solution (HCl) to it, and the dosage ratio of basalt flakes and hydrochloric acid solution (HCl) is 0.4g: 30mL, The concentration of the hydrochloric acid solution was 4moL/L, and mechanically stirred for 24 hours in a water bath at 80°C to carry out the surface etching reaction. After the reaction is finished, filter and wash to neutrality (pH test paper test), and obtain preliminary surface etched basalt scales by vacuum drying, oven drying and freeze drying. Then the basalt scales of preliminary surface etching of a certain quality are weighed and placed in a three-neck flask, and a lithium chloride solution with a concentration of 0.5mol/L to 3mol/L is added thereto, the basalt scales of preliminary surface etching and The dosage ratio of lithium chloride solution is 1.0g:50mL~200mL. The reaction temperature is 110° C., the stirring rate is 1000 rpm, and the reaction time is 8 h. After the reaction is finished, filter and wash to neutrality (pH test paper test), and obtain cation-exchanged basalt scales by vacuum drying, oven drying and freeze drying. Take a certain mass of cation-exchanged basalt scales and put them in a plastic beaker, add a certain volume of water to it, the mass ratio of cation-exchanged basalt scales to water is 0.1g:50mL~200mL. Transfer the beaker with the sample to the cell pulverizer, place the bottom of the horn of the cell pulverizer at 2/3 of the sample in the beaker, turn on the cell pulverizer, adjust the power to 600W~1000W to start the reaction, and the reaction time is 60min After the reaction is completed, the sample is taken out and placed in a glass bottle for use. After standing still for 24 hours, the upper cloudy liquid was taken out, and the basalt nanosheets were obtained by vacuum drying, oven drying and freeze drying.

(2) Surface modification of basalt nanosheets: Weigh basalt nanosheets A prepared in step (1) with a solid content of 0.1 g and place them in a three-necked flask, then add polyvinylpyrrolidone, basalt nanosheets A and polyvinylpyrrolidone The mass ratio of vinylpyrrolidone is 1:5~20, and the stirring reaction is carried out at room temperature. After the reaction is completed, it is washed with deionized water and ethanol several times and stored for later use.

(3) Preparation of aramid nanofibers: Stir 1.0 g of para-aramid chopped fibers with 1.5 g of potassium hydroxide, 500 mL of dimethyl sulfoxide, and 20 mL of deionized water at room temperature for 12 hours, and then add 1000mL of deionized water was used for protonation reduction, and repeated washing with deionized water and absolute ethanol until no excess dimethyl sulfoxide remained, and aramid nanofibers were obtained, which were stored in a refrigerator at 4°C for later use.

(4) Preparation of insulating film: Mix basalt nanosheets B containing carbonyl groups on the surface obtained in step (2) with aramid nanofibers in step (3), and the amount of basalt nanosheets B added is equal to the amount of aramid nanofiber solids The content is 1.0wt%~10wt%, the mixing method is magnetic stirring, mechanical stirring, ball milling; the stirring rate of magnetic stirring and mechanical stirring is 500rpm~1500rpm, the stirring time is 0.5~2h; the ball milling time is 10min~30min. After the reaction is completed, a film is formed by suction filtration, and after drying, a composite insulating film doped with aramid fiber nanofibers and basalt nanosheets is obtained.

Below in conjunction with embodiment the present invention is described in further detail:

Example 1

A preparation method for aramid nanofiber doped basalt nanosheet composite insulating film, comprising the following steps:

(1) Preparation of basalt nanosheets: Weigh a certain amount of basalt flakes and place them in a three-neck flask, add hydrochloric acid solution (HCl) to it, and the dosage ratio of basalt flakes and hydrochloric acid solution (HCl) is 0.4g: 30mL, The concentration of the hydrochloric acid solution was 4moL/L, and mechanically stirred for 24 hours in a water bath at 80°C to carry out the surface etching reaction. After the reaction is finished, filter and wash to neutrality (pH test paper test), and obtain preliminary surface etched basalt scales by vacuum drying, oven drying and freeze drying. Then take the basalt scales of preliminary surface etching of a certain quality and place them in a three-neck flask, add the lithium chloride solution with a concentration of 0.5mol/L to it, the basalt scales and lithium chloride solution of preliminary surface etching The dosage ratio is 1.0g: 50mL. The reaction temperature is 110° C., the stirring rate is 1000 rpm, and the reaction time is 8 h. After the reaction is finished, filter and wash to neutrality (pH test paper test), and obtain cation-exchanged basalt scales by vacuum drying, oven drying and freeze drying. Take a certain mass of cation-exchanged basalt scales and put them in a plastic beaker, add a certain volume of water to it, the mass ratio of cation-exchanged basalt scales to water is 0.1g:200mL. Transfer the beaker with the sample to the cell pulverizer, place the bottom of the horn of the cell pulverizer at 2/3 of the sample in the beaker, turn on the cell pulverizer, adjust the power to 600W to start the reaction, and the reaction time is 60min. After completion, the samples were taken out and placed in glass bottles for later use. After standing still for 24 hours, the upper cloudy liquid was taken out, and the basalt nanosheets were obtained by vacuum drying, oven drying and freeze drying.

(2) Surface modification of basalt nanosheets: Weigh basalt nanosheets A prepared in step (1) with a solid content of 0.1 g and place them in a three-necked flask, then add polyvinylpyrrolidone, basalt nanosheets A and polyvinylpyrrolidone The mass ratio of vinylpyrrolidone is 1:5, and the stirring reaction is carried out at room temperature. After the reaction is completed, it is washed with deionized water and ethanol several times and stored for later use.

(3) Preparation of aramid nanofibers: Stir 1.0 g of para-aramid chopped fibers with 1.5 g of potassium hydroxide, 500 mL of dimethyl sulfoxide, and 20 mL of deionized water at room temperature for 12 hours, and then add 1000mL of deionized water was used for protonation reduction, and repeated washing with deionized water and absolute ethanol until no excess dimethyl sulfoxide remained, and aramid nanofibers were obtained, which were stored in a refrigerator at 4°C for later use.

(4) Preparation of insulating film: Mix basalt nanosheets B containing carbonyl groups on the surface obtained in step (2) with aramid nanofibers in step (3), and the amount of basalt nanosheets B added is equal to the amount of aramid nanofiber solids The content is 1.0wt%, the mixing method is magnetic stirring, the stirring speed is 500rpm, and the stirring time is 0.5h. After the reaction is completed, a film is formed by suction filtration, and after drying, a composite insulating film doped with aramid fiber nanofibers and basalt nanosheets is obtained.

Figure 1a is the SEM image of the nanosheets in step (1). It can be seen from Figure 1a that the basalt scales have been broken to form a lamellar structure, but the agglomeration effect is obvious. It is found that the Z direction is a nanostructure when zoomed in. It can be seen from Table 1 that after the above-prepared nanosheets are added to the aramid nanofiber solution to form a film, the film has a breakdown strength of 42.107kV/mm and a stress of 60.15MPa.

Example 2

A preparation method of aramid nanofiber doped basalt nanosheet composite insulating film, comprising the following steps:

(1) Preparation of basalt nanosheets: Weigh a certain amount of basalt flakes and place them in a three-neck flask, add hydrochloric acid solution (HCl) to it, and the dosage ratio of basalt flakes and hydrochloric acid solution (HCl) is 0.4g: 30mL, The concentration of the hydrochloric acid solution was 4moL/L, and mechanically stirred for 24 hours in a water bath at 80°C to carry out the surface etching reaction. After the reaction is finished, filter and wash to neutrality (pH test paper test), and obtain preliminary surface etched basalt scales by vacuum drying, oven drying and freeze drying. Then the basalt scales of preliminary surface etching of a certain quality are weighed and placed in a three-neck flask, and the lithium chloride solution whose concentration is 1mol/L is added to it, the basalt scales of preliminary surface etching and lithium chloride solution The dosage ratio is 1.0g:100mL. The reaction temperature is 110° C., the stirring rate is 1000 rpm, and the reaction time is 8 h. After the reaction is finished, filter and wash to neutrality (pH test paper test), and obtain cation-exchanged basalt scales by vacuum drying, oven drying and freeze drying. Take a certain mass of cation-exchanged basalt scales and put them in a plastic beaker, add a certain volume of water to it, the mass ratio of cation-exchanged basalt scales to water is 0.1g:200mL. Transfer the beaker with the sample to the cell pulverizer, place the bottom of the horn of the cell pulverizer at 2/3 of the sample in the beaker, turn on the cell pulverizer, adjust the power to 800W to start the reaction, and the reaction time is 60min. After completion, the samples were taken out and placed in glass bottles for later use. After standing still for 24 hours, the upper cloudy liquid was taken out, and the basalt nanosheets were obtained by vacuum drying, oven drying and freeze drying.

(2) Surface modification of basalt nanosheets: Weigh basalt nanosheets A prepared in step (1) with a solid content of 0.1 g and place them in a three-necked flask, then add polyvinylpyrrolidone, basalt nanosheets A and polyvinylpyrrolidone The mass ratio of vinylpyrrolidone is 1:5, and the stirring reaction is carried out at room temperature. After the reaction is completed, it is washed with deionized water and ethanol several times and stored for later use.

(3) Preparation of aramid nanofibers: Stir 1.0 g of para-aramid chopped fibers with 1.5 g of potassium hydroxide, 500 mL of dimethyl sulfoxide, and 20 mL of deionized water at room temperature for 12 hours, and then add 1000mL of deionized water was used for protonation reduction, and repeated washing with deionized water and absolute ethanol until no excess dimethyl sulfoxide remained, and aramid nanofibers were obtained, which were stored in a refrigerator at 4°C for later use.

(4) Preparation of insulating film: Mix basalt nanosheets B containing carbonyl groups on the surface obtained in step (2) with aramid nanofibers in step (3), and the amount of basalt nanosheets B added is equal to the amount of aramid nanofiber solids The content is 3.0wt%, the mixing method is magnetic stirring, the stirring speed is 1000rpm, and the stirring time is 0.5h. After the reaction is completed, a film is formed by suction filtration, and after drying, a composite insulating film doped with aramid fiber nanofibers and basalt nanosheets is obtained.

It can be seen from Table 1 that after the above-prepared nanosheets are added to the aramid nanofiber solution to form a film, the film has a breakdown strength of 48.635kV/mm and a stress of 59.61MPa.

Example 3

1. A method for preparing aramid nanofiber doped basalt nanosheet composite insulating film, comprising the following steps:

(1) Preparation of basalt nanosheets: Weigh a certain amount of basalt flakes and place them in a three-neck flask, add hydrochloric acid solution (HCl) to it, and the dosage ratio of basalt flakes and hydrochloric acid solution (HCl) is 0.4g: 30mL, The concentration of the hydrochloric acid solution was 4moL/L, and mechanically stirred for 24 hours in a water bath at 80°C to carry out the surface etching reaction. After the reaction is finished, filter and wash to neutrality (pH test paper test), and obtain preliminary surface etched basalt scales by vacuum drying, oven drying and freeze drying. Then the basalt scales of preliminary surface etching of a certain quality are weighed and placed in a three-neck flask, and the lithium chloride solution whose concentration is 2mol/L is added to it, the basalt scales of preliminary surface etching and lithium chloride solution The dosage ratio is 1.0g: 150mL. The reaction temperature is 110° C., the stirring rate is 1000 rpm, and the reaction time is 8 h. After the reaction is finished, filter and wash to neutrality (pH test paper test), and obtain cation-exchanged basalt scales by vacuum drying, oven drying and freeze drying. A certain mass of cation-exchanged basalt scales was placed in a plastic beaker, and a certain volume of water was added thereto. The mass ratio of cation-exchanged basalt scales to water was 0.1 g: 100 mL. Transfer the beaker with the sample to the cell pulverizer, place the bottom of the horn of the cell pulverizer at 2/3 of the sample in the beaker, turn on the cell pulverizer, adjust the power to 800W to start the reaction, and the reaction time is 60min. After completion, the samples were taken out and placed in glass bottles for later use. After standing still for 24 hours, the upper cloudy liquid was taken out, and the basalt nanosheets were obtained by vacuum drying, oven drying and freeze drying.

(2) Surface modification of basalt nanosheets: Weigh basalt nanosheets A prepared in step (1) with a solid content of 0.1 g and place them in a three-necked flask, then add polyvinylpyrrolidone, basalt nanosheets A and polyvinylpyrrolidone The mass ratio of vinylpyrrolidone is 1:10, and the stirring reaction is carried out at room temperature. After the reaction is completed, it is washed with deionized water and ethanol several times and stored for later use.

(3) Preparation of aramid nanofibers: Stir 1.0 g of para-aramid chopped fibers with 1.5 g of potassium hydroxide, 500 mL of dimethyl sulfoxide, and 20 mL of deionized water at room temperature for 12 hours, and then add 1000mL of deionized water was used for protonation reduction, and repeated washing with deionized water and absolute ethanol until no excess dimethyl sulfoxide remained, and aramid nanofibers were obtained, which were stored in a refrigerator at 4°C for later use.

(4) Preparation of insulating film: Mix basalt nanosheets B containing carbonyl groups on the surface obtained in step (2) with aramid nanofibers in step (3), and the amount of basalt nanosheets B added is equal to the amount of aramid nanofiber solids The content is 5.0wt%, the mixing method is magnetic stirring, the stirring speed is 1000rpm, and the stirring time is 1h. After the reaction is completed, a film is formed by suction filtration, and after drying, a composite insulating film doped with aramid fiber nanofibers and basalt nanosheets is obtained.

Figure 1b is the SEM image of the nanosheets in step (1). From Figure 1a, it can be found that the basalt scales are more severely broken, and the sheet structure is more obvious. Zooming in and observing, it is found that the Z direction is a nanostructure. It can be seen from Table 1 that after the above-prepared nanosheets are added to the aramid nanofiber solution to form a film, the film has a breakdown strength of 51.187kV/mm and a stress of 58.75MPa.

Example 4

A preparation method of aramid nanofiber doped basalt nanosheet composite insulating film, comprising the following steps:

(1) Preparation of basalt nanosheets: Weigh a certain amount of basalt flakes and place them in a three-neck flask, add hydrochloric acid solution (HCl) to it, and the dosage ratio of basalt flakes and hydrochloric acid solution (HCl) is 0.4g: 30mL, The concentration of the hydrochloric acid solution was 4moL/L, and mechanically stirred for 24 hours in a water bath at 80°C to carry out the surface etching reaction. After the reaction is finished, filter and wash to neutrality (pH test paper test), and obtain preliminary surface etched basalt scales by vacuum drying, oven drying and freeze drying. Then the basalt scales of preliminary surface etching of a certain quality are weighed and placed in a three-necked flask, and the lithium chloride solution whose concentration is 3mol/L is added to it, the basalt scales of preliminary surface etching and lithium chloride solution The dosage ratio is 1.0g: 200mL. The reaction temperature is 110° C., the stirring rate is 1000 rpm, and the reaction time is 8 h. After the reaction is finished, filter and wash to neutrality (pH test paper test), and obtain cation-exchanged basalt scales by vacuum drying, oven drying and freeze drying. A certain mass of cation-exchanged basalt scales was placed in a plastic beaker, and a certain volume of water was added thereto. The mass ratio of cation-exchanged basalt scales to water was 0.1 g: 100 mL. Transfer the beaker with the sample to the cell pulverizer, place the bottom of the horn of the cell pulverizer at 2/3 of the sample in the beaker, turn on the cell pulverizer, adjust the power to 1000W to start the reaction, and the reaction time is 60min. After completion, the samples were taken out and placed in glass bottles for later use. After standing still for 24 hours, the upper cloudy liquid was taken out, and the basalt nanosheets were obtained by vacuum drying, oven drying and freeze drying.

(2) Surface modification of basalt nanosheets: Weigh basalt nanosheets A prepared in step (1) with a solid content of 0.1 g and place them in a three-necked flask, then add polyvinylpyrrolidone, basalt nanosheets A and polyvinylpyrrolidone The mass ratio of vinylpyrrolidone is 1:15, and the stirring reaction is carried out at room temperature. After the reaction is completed, it is washed with deionized water and ethanol several times and stored for later use.

(3) Preparation of aramid nanofibers: Stir 1.0 g of para-aramid chopped fibers with 1.5 g of potassium hydroxide, 500 mL of dimethyl sulfoxide, and 20 mL of deionized water at room temperature for 12 hours, and then add 1000mL of deionized water was used for protonation reduction, and repeated washing with deionized water and absolute ethanol until no excess dimethyl sulfoxide remained, and aramid nanofibers were obtained, which were stored in a refrigerator at 4°C for later use.

(4) Preparation of insulating film: Mix basalt nanosheets B containing carbonyl groups on the surface obtained in step (2) with aramid nanofibers in step (3), and the amount of basalt nanosheets B added is equal to the amount of aramid nanofiber solids The content is 10wt%, the mixing method is magnetic stirring, the stirring speed is 1500rpm, and the stirring time is 2h. After the reaction is completed, a film is formed by suction filtration, and after drying, a composite insulating film doped with aramid fiber nanofibers and basalt nanosheets is obtained.

It can be seen from Table 1 that after the above-prepared nanosheets are added to the aramid nanofiber solution to form a film, the film has a breakdown strength of 57.731kV/mm and a stress of 55.61MPa.

Example 5

A preparation method of aramid nanofiber doped basalt nanosheet composite insulating film, comprising the following steps:

(1) Preparation of basalt nanosheets: Weigh a certain amount of basalt flakes and place them in a three-neck flask, add hydrochloric acid solution (HCl) to it, and the dosage ratio of basalt flakes and hydrochloric acid solution (HCl) is 0.4g: 30mL, The concentration of the hydrochloric acid solution was 4moL/L, and mechanically stirred for 24 hours in a water bath at 80°C to carry out the surface etching reaction. After the reaction is finished, filter and wash to neutrality (pH test paper test), and obtain preliminary surface etched basalt scales by vacuum drying, oven drying and freeze drying. Then the basalt scales of preliminary surface etching of a certain quality are weighed and placed in a three-neck flask, and the lithium chloride solution whose concentration is 2mol/L is added to it, the basalt scales of preliminary surface etching and lithium chloride solution The dosage ratio is 1.0g: 200mL. The reaction temperature is 110° C., the stirring rate is 1000 rpm, and the reaction time is 8 h. After the reaction is finished, filter and wash to neutrality (pH test paper test), and obtain cation-exchanged basalt scales by vacuum drying, oven drying and freeze drying. A certain mass of cation-exchanged basalt scales was placed in a plastic beaker, and a certain volume of water was added thereto. The mass ratio of cation-exchanged basalt scales to water was 0.1 g: 50 mL. Transfer the beaker with the sample to the cell pulverizer, place the bottom of the horn of the cell pulverizer at 2/3 of the sample in the beaker, turn on the cell pulverizer, adjust the power to 1000W to start the reaction, and the reaction time is 60min. After completion, the samples were taken out and placed in glass bottles for later use. After standing still for 24 hours, the upper cloudy liquid was taken out, and the basalt nanosheets were obtained by vacuum drying, oven drying and freeze drying.

(2) Surface modification of basalt nanosheets: Weigh basalt nanosheets A prepared in step (1) with a solid content of 0.1 g and place them in a three-necked flask, then add polyvinylpyrrolidone, basalt nanosheets A and polyvinylpyrrolidone The mass ratio of vinylpyrrolidone is 1:20, and the stirring reaction is carried out at room temperature. After the reaction is completed, it is washed with deionized water and ethanol several times and stored for later use.

(3) Preparation of aramid nanofibers: Stir 1.0 g of para-aramid chopped fibers with 1.5 g of potassium hydroxide, 500 mL of dimethyl sulfoxide, and 20 mL of deionized water at room temperature for 12 hours, and then add 1000mL of deionized water was used for protonation reduction, and repeated washing with deionized water and absolute ethanol until no excess dimethyl sulfoxide remained, and aramid nanofibers were obtained, which were stored in a refrigerator at 4°C for later use.

(4) Preparation of insulating film: Mix basalt nanosheets B containing carbonyl groups on the surface obtained in step (2) with aramid nanofibers in step (3), and the amount of basalt nanosheets B added is equal to the amount of aramid nanofiber solids The content is 10wt%, the mixing method is mechanical stirring, the stirring speed is 1000rpm, and the stirring time is 1h. After the reaction is completed, a film is formed by suction filtration, and after drying, a composite insulating film doped with aramid fiber nanofibers and basalt nanosheets is obtained.

Figure 1c is the SEM image of the nanosheets in step (1). From Figure 1a, it can be found that the basalt scales have formed a lamellar structure, and its size is found to be about 80nm when enlarged. It can be seen from Table 1 that after the above-prepared nanosheets are added to the aramid nanofiber solution to form a film, the film has a breakdown strength of 64.554kV/mm and a stress of 54.12MPa.

Example 6

A preparation method of aramid nanofiber doped basalt nanosheet composite insulating film, comprising the following steps:

(1) Preparation of basalt nanosheets: Weigh a certain amount of basalt flakes and place them in a three-neck flask, add hydrochloric acid solution (HCl) to it, and the dosage ratio of basalt flakes and hydrochloric acid solution (HCl) is 0.4g: 30mL, The concentration of the hydrochloric acid solution was 4moL/L, and mechanically stirred for 24 hours in a water bath at 80°C to carry out the surface etching reaction. After the reaction is finished, filter and wash to neutrality (pH test paper test), and obtain preliminary surface etched basalt scales by vacuum drying, oven drying and freeze drying. Then the basalt scales of preliminary surface etching of a certain quality are weighed and placed in a three-necked flask, and the lithium chloride solution whose concentration is 3mol/L is added to it, the basalt scales of preliminary surface etching and lithium chloride solution The dosage ratio is 1.0g: 200mL. The reaction temperature is 110° C., the stirring rate is 1000 rpm, and the reaction time is 8 h. After the reaction is finished, filter and wash to neutrality (pH test paper test), and obtain cation-exchanged basalt scales by vacuum drying, oven drying and freeze drying. A certain mass of cation-exchanged basalt scales was placed in a plastic beaker, and a certain volume of water was added thereto. The mass ratio of cation-exchanged basalt scales to water was 0.1 g: 50 mL. Transfer the beaker with the sample to the cell pulverizer, place the bottom of the horn of the cell pulverizer at 2/3 of the sample in the beaker, turn on the cell pulverizer, adjust the power to 1000W to start the reaction, and the reaction time is 60min. After completion, the samples were taken out and placed in glass bottles for later use. After standing still for 24 hours, the upper cloudy liquid was taken out, and the basalt nanosheets were obtained by vacuum drying, oven drying and freeze drying.

(2) Surface modification of basalt nanosheets: Weigh basalt nanosheets A prepared in step (1) with a solid content of 0.1 g and place them in a three-necked flask, then add polyvinylpyrrolidone, basalt nanosheets A and polyvinylpyrrolidone The mass ratio of vinylpyrrolidone is 1:20, and the stirring reaction is carried out at room temperature. After the reaction is completed, it is washed with deionized water and ethanol several times and stored for later use.

(3) Preparation of aramid nanofibers: Stir 1.0 g of para-aramid chopped fibers with 1.5 g of potassium hydroxide, 500 mL of dimethyl sulfoxide, and 20 mL of deionized water at room temperature for 12 hours, and then add 1000mL of deionized water was used for protonation reduction, and repeated washing with deionized water and absolute ethanol until no excess dimethyl sulfoxide remained, and aramid nanofibers were obtained, which were stored in a refrigerator at 4°C for later use.

(4) Preparation of insulating film: Mix basalt nanosheets B containing carbonyl groups on the surface obtained in step (2) with aramid nanofibers in step (3), and the amount of basalt nanosheets B added is equal to the amount of aramid nanofiber solids The content is 10wt%, the mixing method is mechanical stirring, the stirring speed is 1500rpm, and the stirring time is 2h. After the reaction is completed, a film is formed by suction filtration, and after drying, a composite insulating film doped with aramid fiber nanofibers and basalt nanosheets is obtained.

It can be seen from Table 1 that after the above-prepared nanosheets are added to the aramid nanofiber solution to form a film, the film has a breakdown strength of 73.296kV/mm and a stress of 53.64MPa. From Figure 2(a), it can be found that after the pure aramid nanocellulose membrane undergoes electrical breakdown, an eversion structure is formed around the electrical breakdown hole, and when it is enlarged, it can be found that the edge of the electrical breakdown hole is relatively smooth; while Figure 2(b) is the above-mentioned The electrical breakdown hole morphology of the aramid nanofiber-doped basalt nanosheet composite insulating film prepared by the method shows that the cavity is small and the edges are relatively flat. After zooming in, more rough structures can be found, indicating that its withstand voltage capacity is relatively high. good.

Example 7

1. A method for preparing aramid nanofiber doped basalt nanosheet composite insulating film, comprising the following steps:

(1) Preparation of basalt nanosheets: Weigh a certain amount of basalt flakes and place them in a three-neck flask, add hydrochloric acid solution (HCl) to it, and the dosage ratio of basalt flakes and hydrochloric acid solution (HCl) is 0.4g: 30mL, The concentration of the hydrochloric acid solution was 4moL/L, and mechanically stirred for 24 hours in a water bath at 80°C to carry out the surface etching reaction. After the reaction is finished, filter and wash to neutrality (pH test paper test), and obtain preliminary surface etched basalt scales by vacuum drying, oven drying and freeze drying. Then the basalt scales of preliminary surface etching of a certain quality are weighed and placed in a three-necked flask, and the lithium chloride solution whose concentration is 3mol/L is added to it, the basalt scales of preliminary surface etching and lithium chloride solution The dosage ratio is 1.0g: 200mL. The reaction temperature is 110° C., the stirring rate is 1000 rpm, and the reaction time is 8 h. After the reaction is finished, filter and wash to neutrality (pH test paper test), and obtain cation-exchanged basalt scales by vacuum drying, oven drying and freeze drying. Take a certain mass of cation-exchanged basalt scales and put them in a plastic beaker, add a certain volume of water to it, the mass ratio of cation-exchanged basalt scales to water is 0.1g:200mL. Transfer the beaker with the sample to the cell pulverizer, place the bottom of the horn of the cell pulverizer at 2/3 of the sample in the beaker, turn on the cell pulverizer, adjust the power to 1000W to start the reaction, and the reaction time is 60min. After completion, the samples were taken out and placed in glass bottles for later use. After standing still for 24 hours, the upper cloudy liquid was taken out, and the basalt nanosheets were obtained by vacuum drying, oven drying and freeze drying.

(2) Surface modification of basalt nanosheets: Weigh basalt nanosheets A prepared in step (1) with a solid content of 0.1 g and place them in a three-necked flask, then add polyvinylpyrrolidone, basalt nanosheets A and polyvinylpyrrolidone The mass ratio of vinylpyrrolidone is 1:20, and the stirring reaction is carried out at room temperature. After the reaction is completed, it is washed with deionized water and ethanol several times and stored for later use.

(3) Preparation of aramid nanofibers: Stir 1.0 g of para-aramid chopped fibers with 1.5 g of potassium hydroxide, 500 mL of dimethyl sulfoxide, and 20 mL of deionized water at room temperature for 12 hours, and then add 1000mL of deionized water was used for protonation reduction, and repeated washing with deionized water and absolute ethanol until no excess dimethyl sulfoxide remained, and aramid nanofibers were obtained, which were stored in a refrigerator at 4°C for later use.

(4) Preparation of insulating film: Mix basalt nanosheets B containing carbonyl groups on the surface obtained in step (2) with aramid nanofibers in step (3), and the amount of basalt nanosheets B added is equal to the amount of aramid nanofiber solids content of 10wt%, the mixing method is ball milling, and the ball milling time is 10min. After the reaction is completed, a film is formed by suction filtration, and after drying, a composite insulating film doped with aramid fiber nanofibers and basalt nanosheets is obtained.

It can be seen from Table 1 that after the above-prepared nanosheets are added to the aramid nanofiber solution to form a film, the film has a breakdown strength of 82.214kV/mm and a stress of 52.19MPa. Figure 2(c) is the topography of the electrical breakdown hole of the doped basalt nanosheet insulating film prepared by the above method. The edge is relatively smooth. After zooming in, more rough structures can be found, and there is no dendritic breakdown, indicating its withstand voltage. Ability is better.

Example 8

A preparation method of aramid nanofiber doped basalt nanosheet composite insulating film, comprising the following steps:

(1) Preparation of basalt nanosheets: Weigh a certain amount of basalt flakes and place them in a three-neck flask, add hydrochloric acid solution (HCl) to it, and the dosage ratio of basalt flakes and hydrochloric acid solution (HCl) is 0.4g: 30mL, The concentration of the hydrochloric acid solution was 4moL/L, and mechanically stirred for 24 hours in a water bath at 80°C to carry out the surface etching reaction. After the reaction is finished, filter and wash to neutrality (pH test paper test), and obtain preliminary surface etched basalt scales by vacuum drying, oven drying and freeze drying. Then the basalt scales of preliminary surface etching of a certain quality are weighed and placed in a three-necked flask, and the lithium chloride solution whose concentration is 3mol/L is added to it, the basalt scales of preliminary surface etching and lithium chloride solution The dosage ratio is 1.0g:100mL. The reaction temperature is 110° C., the stirring rate is 1000 rpm, and the reaction time is 8 h. After the reaction is finished, filter and wash to neutrality (pH test paper test), and obtain cation-exchanged basalt scales by vacuum drying, oven drying and freeze drying. A certain mass of cation-exchanged basalt scales was placed in a plastic beaker, and a certain volume of water was added thereto. The mass ratio of cation-exchanged basalt scales to water was 0.1 g: 100 mL. Transfer the beaker with the sample to the cell pulverizer, place the bottom of the horn of the cell pulverizer at 2/3 of the sample in the beaker, turn on the cell pulverizer, adjust the power to 1000W to start the reaction, and the reaction time is 60min. After completion, the samples were taken out and placed in glass bottles for later use. After standing still for 24 hours, the upper cloudy liquid was taken out, and the basalt nanosheets were obtained by vacuum drying, oven drying and freeze drying.

(2) Surface modification of basalt nanosheets: Weigh basalt nanosheets A prepared in step (1) with a solid content of 0.1 g and place them in a three-necked flask, then add polyvinylpyrrolidone, basalt nanosheets A and polyvinylpyrrolidone The mass ratio of vinylpyrrolidone is 1:20, and the stirring reaction is carried out at room temperature. After the reaction is completed, it is washed with deionized water and ethanol several times and stored for later use.

(3) Preparation of aramid nanofibers: Stir 1.0 g of para-aramid chopped fibers with 1.5 g of potassium hydroxide, 500 mL of dimethyl sulfoxide, and 20 mL of deionized water at room temperature for 12 hours, and then add 1000mL of deionized water was used for protonation reduction, and repeated washing with deionized water and absolute ethanol until no excess dimethyl sulfoxide remained, and aramid nanofibers were obtained, which were stored in a refrigerator at 4°C for later use.

(4) Preparation of insulating film: Mix basalt nanosheets B containing carbonyl groups on the surface obtained in step (2) with aramid nanofibers in step (3), and the amount of basalt nanosheets B added is equal to the amount of aramid nanofiber solids content of 10wt%, the mixing method is ball milling, and the ball milling time is 20min. After the reaction is completed, a film is formed by suction filtration, and after drying, a composite insulating film doped with aramid fiber nanofibers and basalt nanosheets is obtained.

It can be seen from Table 1 that after the above-prepared nanosheets are added to the aramid nanofiber solution to form a film, the film has a breakdown strength of 85.668kV/mm and a stress of 52.03MPa.

Example 9

1. An aramid fiber nanofiber doped basalt nanosheet composite insulating film, comprising the following steps:

(1) Preparation of basalt nanosheets: Weigh a certain amount of basalt flakes and place them in a three-neck flask, add hydrochloric acid solution (HCl) to it, and the dosage ratio of basalt flakes and hydrochloric acid solution (HCl) is 0.4g: 30mL, The concentration of the hydrochloric acid solution was 4moL/L, and mechanically stirred for 24 hours in a water bath at 80°C to carry out the surface etching reaction. After the reaction is finished, filter and wash to neutrality (pH test paper test), and obtain preliminary surface etched basalt scales by vacuum drying, oven drying and freeze drying. Then the basalt scales of preliminary surface etching of a certain quality are weighed and placed in a three-necked flask, and the lithium chloride solution whose concentration is 3mol/L is added to it, the basalt scales of preliminary surface etching and lithium chloride solution The dosage ratio is 1.0g: 200mL. The reaction temperature is 110° C., the stirring rate is 1000 rpm, and the reaction time is 8 h. After the reaction is finished, filter and wash to neutrality (pH test paper test), and obtain cation-exchanged basalt scales by vacuum drying, oven drying and freeze drying. A certain mass of cation-exchanged basalt scales was placed in a plastic beaker, and a certain volume of water was added thereto. The mass ratio of cation-exchanged basalt scales to water was 0.1 g: 50 mL. Transfer the beaker with the sample to the cell pulverizer, place the bottom of the horn of the cell pulverizer at 2/3 of the sample in the beaker, turn on the cell pulverizer, adjust the power to 1000W to start the reaction, and the reaction time is 60min. After completion, the samples were taken out and placed in glass bottles for later use. After standing still for 24 hours, the upper cloudy liquid was taken out, and the basalt nanosheets were obtained by vacuum drying, oven drying and freeze drying.

(2) Surface modification of basalt nanosheets: Weigh basalt nanosheets A prepared in step (1) with a solid content of 0.1 g and place them in a three-necked flask, then add polyvinylpyrrolidone, basalt nanosheets A and polyvinylpyrrolidone The mass ratio of vinylpyrrolidone is 1:20, and the stirring reaction is carried out at room temperature. After the reaction is completed, it is washed with deionized water and ethanol several times and stored for later use.

(3) Preparation of aramid nanofibers: Stir 1.0 g of para-aramid chopped fibers with 1.5 g of potassium hydroxide, 500 mL of dimethyl sulfoxide, and 20 mL of deionized water at room temperature for 12 hours, and then add 1000mL of deionized water was used for protonation reduction, and repeated washing with deionized water and absolute ethanol until no excess dimethyl sulfoxide remained, and aramid nanofibers were obtained, which were stored in a refrigerator at 4°C for later use.

(4) Preparation of insulating film: Mix basalt nanosheets B containing carbonyl groups on the surface obtained in step (2) with aramid nanofibers in step (3), and the amount of basalt nanosheets B added is equal to the amount of aramid nanofiber solids content of 10wt%, the mixing method is ball milling, and the ball milling time is 30min. After the reaction is completed, a film is formed by suction filtration, and after drying, a composite insulating film doped with aramid fiber nanofibers and basalt nanosheets is obtained.

Figure 1d is the SEM image of the nanosheets in step (1). From Figure 1a, it can be found that the basalt scales have formed many sheets, and the size of the scales is about 50-80nm when enlarged. It can be seen from Table 1 that after the above-prepared nanosheets are added to the aramid nanofiber solution to form a film, the film has a breakdown strength of 87.954kV/mm and a stress of 50.69MPa.

Table 1 is the breakdown strength and stress table of the aramid nanofiber doped basalt nanosheet composite insulating film prepared in Examples 1-9;

Because basalt nanosheets have many physical properties of basalt scales, such as stable high and low temperature resistance, and have a large specific surface area and less surface impurities. The most important thing is that basalt nanosheets have a nanostructure, and when added to aramid nanofibers, they can also be stacked with resin to form a dense layered structure, making aramid nanofibers. In addition, basalt nanosheets have excellent strength, wear resistance, and acid and alkali resistance, which makes the insulating film have great prospects.

It can be known from common technical knowledge that the present invention can be realized through other embodiments without departing from its spirit or essential features. Accordingly, the above-disclosed embodiments are, in all respects, illustrative and not exclusive. All changes within the scope of the present invention or within the scope equivalent to the present invention are embraced by the present invention.

Claims (6)

1. The preparation method of the aramid nanofiber-doped basalt nanosheet composite insulating film is characterized by comprising the following steps of:

(1) Preparation of basalt nanosheets: placing basalt flakes in hydrochloric acid solution, stirring at a set temperature to perform surface etching reaction, and performing suction filtration and washing to neutrality after the reaction is finished to obtain basalt flakes with primary surface etching; placing the basalt flakes subjected to the preliminary surface etching into a lithium chloride solution, performing cation exchange reaction at a set temperature, and performing suction filtration washing after the reaction is finished to obtain the basalt flakes subjected to cation exchange; preparing the cation-exchanged basalt flakes into mixed suspension, then carrying out ultrasonic crushing treatment, standing, taking out turbid liquid on the upper layer, and drying to obtain basalt nanosheets A;

(2) Surface modification of basalt nanosheets: stirring the basalt nanosheet A and polyvinylpyrrolidone solution for reaction, and modifying the surface of the basalt nanosheet A to obtain basalt nanosheet B with carbonyl groups on the surface;

(3) Preparation of an insulating film: mixing the basalt nano sheet B with the surface containing carbonyl and the aramid nano fiber solution, performing suction filtration to form a film, and drying to obtain the aramid nano fiber doped basalt nano sheet composite insulating film;

The dosage ratio of basalt flake to hydrochloric acid solution in the step (1) is 0.4g:30mL, hydrochloric acid concentration of 4moL/L, surface etching reaction temperature of 80 ℃ and surface etching reaction time of 24h;

the concentration of the lithium chloride solution in the step (1) is 0.5 mol/L-3 mol/L, and the dosage ratio of the basalt flakes subjected to preliminary surface etching to the lithium chloride solution is 1.0g: 50-200 mL; the cation exchange reaction temperature is 110 ℃, and the cation exchange reaction time is 8 hours;

the mass ratio of basalt nanosheets A to polyvinylpyrrolidone in the step (2) is 1: 5-1: 20, a step of;

the adding amount of the basalt nanosheets B in the step (3) is 1.0-10 wt% of the solid content of the aramid nanofibers.

2. The preparation method of the aramid nanofiber basalt nanosheet composite insulating film according to claim 1, wherein the specific preparation process of the aramid nanofiber is as follows:

stirring para-aramid chopped fiber, potassium hydroxide, dimethyl sulfoxide and deionized water at room temperature for reaction, adding deionized water for deprotonation reduction reaction after the reaction is completed, and repeatedly washing to obtain the aramid nanofiber.

3. The preparation method of the aramid nanofiber-doped basalt nanosheet composite insulating film according to claim 2, wherein the dosage ratio of the para-aramid chopped fiber to the potassium hydroxide to the dimethyl sulfoxide is 1g:1.5g:500mL; the deionized water dosage in the deprotonation reduction reaction is 200mL.

4. The method for preparing the basalt nano-sheet composite insulating film doped with aramid nano-fibers according to claim 1, wherein the mass ratio of the cation exchanged basalt flakes to water in the mixed suspension in the step (1) is 0.1g:50 mL-200 mL.

5. An aramid nanofiber-doped basalt nanosheet composite insulating film, characterized by being prepared based on the preparation method as claimed in any one of claims 1-4.

6. The aramid nanofiber-doped basalt nanosheet composite insulating film disclosed by claim 5 is characterized in that the electric breakdown strength of the aramid nanofiber-doped basalt nanosheet composite insulating film is 73.296 kV/mm-87.954 kV/mm.