A polyvinylidene fluoride-based insulation composite material, a preparation method and application

Abstract

The application relates to the technical field of high polymer materials, and discloses a polyvinyl fluoride-based insulation composite material, a preparation method and application. The preparation method of the polyvinyl fluoride-based insulation composite material comprises the following steps: preparing a pyrrole-based modifier, and modifying a functionalized carbon nanotube composite material with the pyrrole-based modifier to obtain a surface-modified nanotube composite material; combining amino-nano boron nitride with the surface-modified nanotube composite material to obtain a boron nitride / carbon nanotube composite material; grafting an organic polymer chain on the surface of the boron nitride / carbon nanotube composite material to obtain an organic-inorganic hybrid filler; taking the organic-inorganic hybrid filler and polyvinyl fluoride as raw materials, casting a film, and hot-pressing to obtain a polyvinyl fluoride-based insulation composite material; the polyvinyl fluoride-based insulation composite material has excellent insulation performance, heat conduction performance and mechanical properties, and can be used in electronic and electrical materials.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to a polyvinylidene fluoride insulating composite material, its preparation method, and its application. Background Technology

[0002] Polymer materials are widely used in various fields due to their excellent chemical resistance, electrical insulation properties, light weight, and ease of processing. Polyvinylidene fluoride (PVDF) resin refers to polyvinylidene fluoride (VDF) homopolymer or copolymer of VDF with other small amounts of fluorinated vinyl monomers. It has advantages such as good thermal stability, resistance to degradation, and good insulation properties, and is widely used in insulating materials in the electronics and electrical fields.

[0003] With the rapid development of microelectronics technology, electronic components are becoming increasingly miniaturized, higher frequency, more efficient, and more multifunctional. Difficulty in heat dissipation of electrical components can affect their accuracy and service life. Polyvinylidene fluoride (PVDF) has an intrinsic thermal conductivity of 0.1-0.2 W / (m·K), which limits its application in the electronics and electrical industries. Adding thermally conductive fillers to PVDF is a common method to improve its thermal conductivity. For example, Chinese patent application CN113372669A discloses a PVDF-converted carbon nanotube / graphene thermally conductive composite material and its preparation method. This method uses styrene as a carbon source to grow nitrogen-free carbon nanotubes in situ on graphene, obtaining a converted carbon nanotube / graphene dual thermally conductive filler. This filler is then combined with PVDF via hot pressing to obtain the desired composite material. However, the converted carbon nanotube / graphene dual thermally conductive filler can lead to a decrease in the insulation performance of the PVDF composite material.

[0004] Therefore, preparing a polyvinylidene fluoride composite material that simultaneously possesses excellent insulation and thermal conductivity properties will expand the application range of polyvinylidene fluoride composite materials. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a method for preparing polyvinylidene fluoride insulating composite materials, comprising the following steps: Step 1: Gallic acid reacts with 5-chloropyrrole-2-carboxaldehyde to obtain a pyrrole compound; the pyrrole compound reacts with 3-buten-1-amine to obtain a pyrrole-modifying agent; Step 2: Modify the functionalized carbon nanotube composite material with a pyrrole modifier to obtain a surface-modified nanotube composite material. The functionalized carbon nanotube composite material is obtained by acyl chloride treatment of carbon nanotube composite material, the carbon nanotube composite material is obtained by depositing oxidized nanodiamond on aminated multi-walled carbon nanotube, and the oxidized nanodiamond is obtained by oxidizing nanodiamond with hydrogen peroxide aqueous solution. Step 3: Hexagonal boron nitride, urea, and deionized water are reacted to obtain aminated boron nitride nanoparticles; the aminated boron nitride nanoparticles are then combined with surface-modified nanotube composite materials to obtain boron nitride / carbon nanotube composite materials. Step 4: Graft organic polymer chains onto the surface of the boron nitride / carbon nanotube composite material to obtain an organic-inorganic hybrid filler; Step 5: Using organic-inorganic hybrid filler and polyvinylidene fluoride as raw materials, cast film and hot press to obtain polyvinylidene fluoride insulating composite material.

[0006] Preferably, in step one, the pyrrole modifier is prepared by the following method: Gallic acid and triethylamine were added to N,N-dimethylformamide, and then a 12.95wt% solution of 5-chloropyrrole-2-carboxaldehyde in N,N-dimethylformamide was added at 0-5℃. The mixture was stirred for 20-40 min, and then stirred at 22-28℃ for 12-20 h to purify the product and obtain the pyrrole compound. The mass ratio of gallic acid, triethylamine, N,N-dimethylformamide, and the 12.95wt% solution of 5-chloropyrrole-2-carboxaldehyde in N,N-dimethylformamide was (17.01-20.4):(10.12-12.14):(150-250):(100-120). The specific reaction mechanism is as follows: Pyrrole compound and 3-buten-1-amine were added to N,N-dimethylformamide and reacted under nitrogen atmosphere at 60-70℃ for 6-10 h with stirring. The product was purified to obtain a pyrrole modifier. The mass ratio of the pyrrole compound, 3-buten-1-amine and N,N-dimethylformamide was (115.7-26.3):(6.2-7.8):(140-180). The specific reaction mechanism is as follows: In the above process, gallic acid reacts with 5-chloropyrrole-2-carboxaldehyde in an equimolar ratio, and one phenolic hydroxyl group of gallic acid undergoes a substitution reaction with the chlorine of 5-chloropyrrole-2-carboxaldehyde to obtain a pyrrole compound; next, the pyrrole compound and 3-buten-1-amine are combined through a Schiff base reaction to obtain a pyrrole-based modifier, wherein the pyrrole-based modifier includes a nitrogen-containing pyrrole ring structure, a carboxyl group, a phenolic hydroxyl group, and a carbon-carbon double bond.

[0007] Preferably, in step two, the surface-modified nanotube composite material is prepared by the following method: The functionalized carbon nanotube composite material was added to N,N-dimethylformamide and sonicated. Then triethylamine was added, and the mixture was stirred at 0-5℃ for 20-40 min. Next, a solution of N,N-dimethylformamide with 8.6 wt% pyrrole modifier was added, and the mixture was stirred for 40-60 min. Then, the mixture was stirred at 22-28℃ for 20-30 h, and the product was purified to obtain the surface-modified nanotube composite material. The mass ratio of the functionalized carbon nanotube composite material, N,N-dimethylformamide, triethylamine, and the N,N-dimethylformamide solution with 8.6 wt% pyrrole modifier was (0.5-1.5):(150-200):(0.6-1.2):(20-40). In the above process, the acyl chloride groups on the surface of the functionalized carbon nanotube composite material combine with the phenolic hydroxyl groups in the pyrrole modifier through an esterification reaction, grafting the pyrrole modifier onto the functionalized carbon nanotube composite material. The pyrrole nitrogen and phenolic hydroxyl groups in the pyrrole modifier can form hydrogen bonds with polyvinylidene fluoride, thereby promoting the dispersion of the functionalized carbon nanotube composite material in polyvinylidene fluoride.

[0008] Preferably, in step two, the method for preparing the functionalized carbon nanotube composite material includes the following steps: Step A1: At 70-80℃, add nanodiamond to a 30wt% hydrogen peroxide aqueous solution with a solid-liquid mass ratio of 1:(300-500), soak for 20-30 hours, and purify to obtain oxidized nanodiamond; Step A2: Add nanodiamond oxide and dimethylaminopyridine to N,N-dimethylformamide, sonicate, then add 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide, stir at 22-28℃ for 40-80 min, then add aminated multi-walled carbon nanotube dispersion, stir and react at 22-28℃ for 10-14 h, purify, and obtain carbon nanotube composite material; wherein, the mass ratio of aminated multi-walled carbon nanotubes, nanodiamond oxide, dimethylaminopyridine, and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide is (1.4-2.4):(0.8-1.2):(0.2-0.4):(0.2-0.4); Step A3: Mix carbon nanotube composite material and sulfoxide at a mass ratio of (0.5-1.5):(250-350), stir and react at 60-70℃ for 20-30h, and then rotary evaporate to obtain functionalized carbon nanotube composite material. In the above process, nanodiamonds are treated with an aqueous hydrogen peroxide solution to form abundant carboxyl groups on their surface. Then, under the action of dimethylaminopyridine and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide, the oxidized nanodiamonds and aminated multi-walled carbon nanotubes are combined through an amidation reaction, depositing the oxidized nanodiamonds onto the aminated multi-walled carbon nanotubes to obtain a carbon nanotube composite material. Further, the carboxyl groups on the surface of the carbon nanotube composite material are converted into acyl chloride groups under the action of sulfoxide, resulting in a functionalized carbon nanotube composite material. Nanodiamonds have excellent thermal conductivity, insulation properties, and low toxicity, but due to their nanoscale effect, they are prone to agglomeration in polymer matrices. Carbon nanotubes possess high thermal conductivity, mechanical properties, and a high aspect ratio, making them more likely to form interconnected thermally conductive networks in polymer matrices. This can significantly improve the thermal conductivity of polymer composites even at low filler ratios. However, because carbon nanotubes also exhibit excellent electrical conductivity, they cannot meet the requirements for insulating materials. Therefore, this invention deposits nanodiamonds onto the surface of carbon nanotubes. The two are bonded through amide bonds, promoting uniform dispersion of nanodiamonds on the carbon nanotubes, reducing interfacial thermal resistance, and forming a new thermally conductive network. More importantly, the deposition of nanodiamonds can disrupt the conductive network between carbon nanotubes, endowing the functionalized carbon nanotube composite with excellent insulation properties.

[0009] Preferably, in step three, the preparation method of the boron nitride / carbon nanotube composite material is as follows: Hexagonal boron nitride, urea and deionized water were mixed in a mass ratio of (2-4):(40-50):(120-150), ultrasonically treated at 22-28℃ for 5-7 hours, filtered and dried to obtain aminated nano boron nitride. Aminated boron nitride nanoparticles were dispersed in N,N-dimethylformamide, sonicated, and then surface-modified nanotube composite material was added. The mixture was stirred at 24-27℃ for 2-3 hours, filtered, and dried to obtain boron nitride / carbon nanotube composite material. The mass ratio of the aminated boron nitride nanoparticles, N,N-dimethylformamide, and surface-modified nanotube composite material was (0.6-1.8):(100-150):(1-2). In the above process, hexagonal boron nitride, also known as "white graphite," not only has good mechanical properties but is also one of the best materials in ceramics in terms of thermal conductivity and high-temperature insulation. However, due to its large specific surface area, high surface energy, and tendency to agglomerate, it is difficult to disperse evenly in polymer matrices. This invention introduces abundant amino groups into the surface of nano-boron nitride through amination treatment, which combine with the carboxyl groups on the surface-modified nanotube composite material through electrostatic and hydrogen bonding. The surface-modified nanotube composite material is inserted between the lamellar structures of the amination nano-boron nitride, avoiding agglomeration. At the same time, the lamellar boron nitride acts as a physical barrier for the surface-modified nanotube composite material, further blocking the conductive network between carbon nanotubes, thereby endowing the boron nitride / carbon nanotube composite material with excellent insulation properties. Therefore, the surface-modified nanotube composite material with a "point-line" structure and the lamellar boron nitride form a three-dimensional "point-line-surface" thermally conductive network structure with excellent thermal conductivity.

[0010] Preferably, in step four, the preparation method of the organic-inorganic hybrid filler is as follows: Boron nitride / carbon nanotube composite material was added to N,N-dimethylformamide, sonicated, and nitrogen gas was introduced for 10-20 min. Then, methyl methacrylate and azobisisobutyronitrile were added. The mixture was heated to 86-94℃ and stirred for 5-7 h in a closed environment. The product was purified to obtain an organic-inorganic hybrid filler. The mass ratio of the boron nitride / carbon nanotube composite material, N,N-dimethylformamide, methyl methacrylate, and azobisisobutyronitrile was (0.8-1.2):(100-150):(5.5-9.1):(0.02-0.04). In the above process, under the initiation of azobisisobutyronitrile (AIBN), the presence of carbon-carbon double bonds on the surface of the boron nitride / carbon nanotube composite material enables it to polymerize with methyl methacrylate monomers. The introduction of polymethyl methacrylate organic polymer chains into the boron nitride / carbon nanotube composite material further improves the interfacial compatibility between the boron nitride / carbon nanotube composite material and polyvinylidene fluoride (PVDF). This is because: on the one hand, hydrogen bonds can be formed between the polymethyl methacrylate chains and PVDF; on the other hand, its long organic chains can form physical entanglements with the PVDF polymer chains, thereby promoting the uniform dispersion of the organic-inorganic hybrid filler in the PVDF matrix.

[0011] Preferably, in step five, the preparation method of the polyvinylidene fluoride insulating composite material is as follows: Organic-inorganic hybrid filler and N,N-dimethylformamide were mixed at a mass ratio of (1-3):(50-80) to obtain an organic-inorganic hybrid filler dispersion; polyvinylidene fluoride and N,N-dimethylformamide were mixed at a mass ratio of (10-15):(50-80) and stirred at 60-70℃ until completely dissolved. Then, the above organic-inorganic hybrid filler dispersion was added, and the temperature was kept constant. Stirring was continued for 4-6 hours to obtain a casting solution. The casting solution was uniformly coated onto a glass plate, dried, and hot-pressed to obtain a polyvinylidene fluoride insulating composite material with a thickness of 15-25µm.

[0012] Preferably, the drying conditions are: temperature 110-130℃, time 40-80min; the hot pressing conditions are: temperature 175-185℃, pressure 9-11MPa, time 4-6min.

[0013] The polyvinylidene fluoride insulating composite material prepared by the aforementioned method is a polyvinylidene fluoride insulating composite material.

[0014] The polyvinylidene fluoride insulating composite material of the present invention can be used in electronic and electrical materials.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention combines organic-inorganic hybrid fillers with polyvinylidene fluoride (PVDF). The addition of organic-inorganic hybrid fillers endows PVDF insulating composites with excellent insulation, thermal conductivity, and mechanical properties, specifically manifested in: 1. This invention deposits nanodiamonds onto the surface of carbon nanotubes, where they are bonded by amide bonds. This promotes uniform dispersion of the nanodiamonds on the carbon nanotubes, reduces interfacial thermal resistance, and forms a new thermally conductive network. More importantly, the deposition of nanodiamonds blocks the conductive network between carbon nanotubes. Furthermore, the surface-modified nanotube composite material is inserted between the lamellar structures of aminated boron nitride nanotubes, preventing the agglomeration of the aminated boron nitride nanotubes. Simultaneously, the lamellar boron nitride nanotubes act as a physical barrier for the surface-modified nanotube composite material, further blocking the conductive network between carbon nanotubes. This endows the boron nitride / carbon nanotube composite material with excellent insulation properties. Therefore, this invention combines nanodiamonds, multi-walled carbon nanotubes, and nano-boron nitride, not only solving the agglomeration problem of inorganic nanomaterials but also endowing the organic-inorganic hybrid filler with a "point-line-surface" structure of thermally conductive and insulating networks, thereby improving the insulation and thermal conductivity of polyvinylidene fluoride insulating composite materials. 2. The nanodiamond, multi-walled carbon nanotubes, and nano-boron nitride in the organic-inorganic hybrid filler of the present invention serve as inorganic reinforcing fillers, which can improve the mechanical properties of the polymer matrix. Therefore, the organic-inorganic hybrid filler has a positive impact on improving the mechanical properties of polyvinylidene fluoride insulating composite materials. 3. The organic-inorganic hybrid filler of the present invention includes pyrrole nitrogen and phenolic hydroxyl groups introduced by a pyrrole modifier, and polymethyl methacrylate chains formed by polymerization of methyl methacrylate monomers. The pyrrole nitrogen and phenolic hydroxyl groups in the pyrrole modifier can form hydrogen bonds with polyvinylidene fluoride. The polymethyl methacrylate chains can not only form hydrogen bonds with polyvinylidene fluoride, but also form physical entanglements with the polymer chains of polyvinylidene fluoride. The combined effect of the above-mentioned multiple organic structures promotes the uniform dispersion of the organic-inorganic hybrid filler in polyvinylidene fluoride, thereby further improving the comprehensive performance of polyvinylidene fluoride insulating composite materials. Attached Figure Description

[0016] Figure 1 This is a comparison chart of the volume resistivity tests of polyvinylidene fluoride insulating composite materials prepared in Examples 2-4 and Comparative Examples 2-6 of the present invention; Figure 2 This is a comparison chart of the thermal conductivity tests of polyvinylidene fluoride insulating composite materials prepared in Examples 2-4 and Comparative Examples 2-5 of the present invention. Detailed Implementation

[0017] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0018] Example 1 This embodiment discloses a method for preparing a functionalized carbon nanotube composite material, including the following steps: Step A1: Add nanodiamond to a 30wt% hydrogen peroxide aqueous solution at 75℃, with a solid-liquid mass ratio of 1:400, soak for 25h, collect the precipitate by centrifugation, wash with deionized water 4 times, and vacuum dry at 65℃ for 12h to obtain oxidized nanodiamond. Step A2: 1.9g of aminated multi-walled carbon nanotubes were dispersed in 200g of N,N-dimethylformamide and sonicated for 30min to obtain an aminated multi-walled carbon nanotube dispersion. 1g of nanodiamond oxide and 0.3g of dimethylaminopyridine were added to 80g of N,N-dimethylformamide and sonicated for 30min. Then, 0.3g of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide was added and stirred at 25℃ for 60min. The above aminated multi-walled carbon nanotube dispersion was then added and stirred at 25℃ for 12h. After the reaction was completed, the precipitate was collected by centrifugation, washed 9 times with deionized water, and then vacuum dried at 65℃ for 12h to obtain the carbon nanotube composite material. Step A3: Add 1g of carbon nanotube composite material to 300g of thionyl chloride and stir at 605℃ for 5h. After the reaction is complete, remove the solvent and excess thionyl chloride by rotary evaporation to obtain the functionalized carbon nanotube composite material.

[0019] Example 2 This embodiment discloses a method for preparing a polyvinylidene fluoride insulating composite material, including the following steps: Step 1: Add 17.01g gallic acid and 10.12g triethylamine to 150g N,N-dimethylformamide. Then, at 0-5℃, add 100g of 12.95wt% N,N-dimethylformamide solution of 5-chloropyrrole-2-carboxaldehyde at a rate of 1mL / min. Stir for 20min, then stir at 22℃ for 20h. After the reaction is complete, precipitate the product with deionized water at 5℃, filter, wash, and dry to obtain the pyrrole compound. 15.7 g of pyrrole compound and 6.2 g of 3-buten-1-amine were added to 140 g of N,N-dimethylformamide and stirred at 60 °C for 10 h under a nitrogen atmosphere. After the reaction was completed, the solvent and excess 3-buten-1-amine were removed by rotary evaporation to obtain the pyrrole modifier. Step 2: Add 0.5g of the functionalized carbon nanotube composite material prepared in Example 1 to 150g of N,N-dimethylformamide, sonicate for 20min, then add 0.6g of triethylamine, stir at 0℃ for 40min, then add 20g of N,N-dimethylformamide solution of 8.6wt% pyrrole modifier at a rate of 1mL / min, stir for 40min, then stir at 22℃ for 30h. After the reaction is completed, centrifuge to collect the precipitate, wash with N,N-dimethylformamide and deionized water, and vacuum dry at 60℃ for 14h to obtain the surface-modified nanotube composite material. Step 3: Mix 2g of hexagonal boron nitride, 40g of urea and 120g of deionized water, sonicate at 22℃ for 5h, filter, and vacuum dry the resulting solid product at 50℃ for 4h to obtain aminated nano boron nitride. 0.6 g of aminated boron nitride nanoparticles were dispersed in 100 g of N,N-dimethylformamide and ultrasonically treated for 1 h. Then, 1 g of surface-modified nanotube composite material was added, stirred at 24 °C for 3 h, filtered, and the resulting solid product was vacuum dried at 50 °C for 4 h to obtain boron nitride / carbon nanotube composite material. Step 4: Add 0.8g of boron nitride / carbon nanotube composite material to 100g of N,N-dimethylformamide, sonicate for 40min, and purge with nitrogen for 10min to remove dissolved oxygen in the reaction system. Then add 5.5g of methyl methacrylate monomer and 0.02g of azobisisobutyronitrile. In a closed environment, heat to 86℃ and stir for 7h. After the reaction is completed, centrifuge to collect the precipitate, wash with N,N-dimethylformamide and deionized water, and vacuum dry at 60℃ for 14h to obtain organic-inorganic hybrid filler. Step 5: Add 1g of organic-inorganic hybrid filler to 50g of N,N-dimethylformamide and sonicate for 30min to obtain an organic-inorganic hybrid filler dispersion; add 10g of polyvinylidene fluoride powder to 50g of N,N-dimethylformamide and stir at 60℃ until completely dissolved, then add the above organic-inorganic hybrid filler dispersion, keep the temperature constant, and continue stirring for 6h to obtain a casting solution; The casting solution was uniformly coated onto a glass plate, dried at 110°C for 80 min to remove DMF, and then hot-pressed at 175°C and 9 MPa for 6 min to obtain a polyvinylidene fluoride insulating composite material with a thickness of 15 µm.

[0020] Example 3 This embodiment discloses a method for preparing a polyvinylidene fluoride insulating composite material, including the following steps: Step 1: Add 20.4 g gallic acid and 12.14 g triethylamine to 250 g N,N-dimethylformamide. Then, at 5 °C, add 120 g of 12.95 wt% N,N-dimethylformamide solution of 5-chloropyrrole-2-carboxaldehyde at a rate of 2 mL / min. Stir for 40 min, then stir at 28 °C for 12 h. After the reaction is complete, precipitate the product with deionized water at 10 °C, filter, wash, and dry to obtain the pyrrole compound. 26.3 g of pyrrole compound and 7.8 g of 3-buten-1-amine were added to 180 g of N,N-dimethylformamide and stirred at 70 °C for 6 h under a nitrogen atmosphere. After the reaction was completed, the solvent and excess 3-buten-1-amine were removed by rotary evaporation to obtain the pyrrole modifier. Step 2: Add 1.5g of the functionalized carbon nanotube composite material prepared in Example 1 to 200g of N,N-dimethylformamide, sonicate for 40min, then add 1.2g of triethylamine, stir at 5℃ for 20min, then add 40g of N,N-dimethylformamide solution of 8.6wt% pyrrole modifier at a rate of 2mL / min, stir for 40-60min, then stir at 28℃ for 20h. After the reaction is complete, centrifuge to collect the precipitate, wash with N,N-dimethylformamide and deionized water, and vacuum dry at 70℃ for 10h to obtain the surface-modified nanotube composite material. Step 3: Mix 4g of hexagonal boron nitride, 50g of urea and 150g of deionized water, sonicate for 7h, filter, and vacuum dry the resulting solid product at 60℃ for 3h to obtain aminated nano boron nitride. 1.8 g of aminated boron nitride nanoparticles were dispersed in 150 g of N,N-dimethylformamide and ultrasonically treated at 28 °C for 2 h. Then, 2 g of surface-modified nanotube composite material was added and stirred at 27 °C for 2 h. The mixture was filtered and the resulting solid product was vacuum dried at 60 °C for 3 h to obtain boron nitride / carbon nanotube composite material. Step 4: Add 1.2g of boron nitride / carbon nanotube composite material to 150g of N,N-dimethylformamide, sonicate for 60min, and purge with nitrogen for 20min to remove dissolved oxygen in the reaction system. Then add 9.1g of methyl methacrylate monomer and 0.04g of azobisisobutyronitrile. In a closed environment, heat to 94℃ and stir for 5h. After the reaction is completed, collect the precipitate by centrifugation, wash with N,N-dimethylformamide and deionized water, and vacuum dry at 70℃ for 10h to obtain organic-inorganic hybrid filler. Step 5: Add 3g of organic-inorganic hybrid filler to 80g of N,N-dimethylformamide and sonicate for 60min to obtain an organic-inorganic hybrid filler dispersion; add 15g of polyvinylidene fluoride powder to 80g of N,N-dimethylformamide and stir at 70℃ until completely dissolved, then add the above organic-inorganic hybrid filler dispersion, keep the temperature constant, and continue stirring for 4h to obtain a casting solution; The casting solution was uniformly coated onto a glass plate, dried at 130°C for 40 min to remove DMF, and then hot-pressed at 185°C and 11 MPa for 4 min to obtain a polyvinylidene fluoride insulating composite material with a thickness of 25 µm.

[0021] Example 4 This embodiment discloses a method for preparing a polyvinylidene fluoride insulating composite material, including the following steps: Step 1: Add 18.1g gallic acid and 11.13g triethylamine to 200g N,N-dimethylformamide. Then, at 3℃, add 110g of a 12.95wt% N,N-dimethylformamide solution of 5-chloropyrrole-2-carboxaldehyde at a rate of 1.5mL / min. Stir for 30min, then stir at 25℃ for 16h. After the reaction is complete, precipitate the product with deionized water at 8℃, filter, wash, and dry to obtain the pyrrole compound. 21g of pyrrole compound and 7g of 3-buten-1-amine were added to 160g of N,N-dimethylformamide and stirred at 65°C for 8h under a nitrogen atmosphere. After the reaction was completed, the solvent and excess 3-buten-1-amine were removed by rotary evaporation to obtain the pyrrole modifier. Step 2: Add 1g of the functionalized carbon nanotube composite material prepared in Example 1 to 175g of N,N-dimethylformamide, sonicate for 30min, then add 0.9g of triethylamine, stir at 3℃ for 30min, then add 30g of N,N-dimethylformamide solution of 8.6wt% pyrrole modifier at a rate of 1.5mL / min, stir for 50min, then stir at 25℃ for 25h. After the reaction is complete, centrifuge to collect the precipitate, wash with N,N-dimethylformamide and deionized water, and vacuum dry at 65℃ for 12h to obtain the surface-modified nanotube composite material. Step 3: Mix 3g of hexagonal boron nitride, 45g of urea and 135g of deionized water, sonicate at 25°C for 6h, filter, and vacuum dry the resulting solid product at 55°C for 3.5h to obtain aminated nano boron nitride. 1.2g of aminated boron nitride nanoparticles were dispersed in 125g of N,N-dimethylformamide and sonicated for 1.5h. Then, 1.5g of surface-modified nanotube composite material was added, stirred at 25℃ for 2.5h, filtered, and the resulting solid product was vacuum dried at 55℃ for 3.5h to obtain boron nitride / carbon nanotube composite material. Step 4: Add 1g of boron nitride / carbon nanotube composite material to 125g of N,N-dimethylformamide, sonicate for 50min, and purge with nitrogen for 15min to remove dissolved oxygen in the reaction system. Then add 7.3g of methyl methacrylate monomer and 0.03g of azobisisobutyronitrile. In a closed environment, heat to 90℃ and stir for 6h. After the reaction is completed, collect the precipitate by centrifugation, wash with N,N-dimethylformamide and deionized water, and vacuum dry at 65℃ for 12h to obtain organic-inorganic hybrid filler. Step 5: Add 2g of organic-inorganic hybrid filler to 65g of N,N-dimethylformamide and sonicate for 45min to obtain an organic-inorganic hybrid filler dispersion; add 12.5g of polyvinylidene fluoride powder to 65g of N,N-dimethylformamide and stir at 65℃ until completely dissolved, then add the above organic-inorganic hybrid filler dispersion, keep the temperature constant, and continue stirring for 5h to obtain a casting solution; The casting solution was uniformly coated onto a glass plate, dried at 120°C for 60 min to remove DMF, and then hot-pressed at 180°C and 10 MPa for 5 min to obtain a polyvinylidene fluoride insulating composite material with a thickness of 20 µm.

[0022] Comparative Example 1 This comparative example discloses a method for preparing functionalized nanodiamonds, comprising the following steps: Step A1: Add nanodiamond to a 30wt% hydrogen peroxide aqueous solution at 75℃, with a solid-liquid mass ratio of 1:400, soak for 25h, collect the precipitate by centrifugation, wash with deionized water 4 times, and vacuum dry at 65℃ for 12h to obtain oxidized nanodiamond. Step A2: Add 1g of carbon nanotube composite material to 300g of thionyl chloride and stir at 605℃ for 5h. After the reaction is complete, remove the solvent and excess thionyl chloride by rotary evaporation to obtain functionalized nanodiamond.

[0023] Comparative Example 2 This comparative example discloses a method for preparing a polyvinylidene fluoride insulating composite material, comprising the following steps: Step 1: Add 17.01g gallic acid and 10.12g triethylamine to 150g N,N-dimethylformamide. Then, at 0-5℃, add 100g of 12.95wt% N,N-dimethylformamide solution of 5-chloropyrrole-2-carboxaldehyde at a rate of 1mL / min. Stir for 20min, then stir at 22℃ for 20h. After the reaction is complete, precipitate the product with deionized water at 5℃, filter, wash, and dry to obtain the pyrrole compound. 15.7 g of pyrrole compound and 6.2 g of 3-buten-1-amine were added to 140 g of N,N-dimethylformamide and stirred at 60 °C for 10 h under a nitrogen atmosphere. After the reaction was completed, the solvent and excess 3-buten-1-amine were removed by rotary evaporation to obtain the pyrrole modifier. Step 2: Add 0.5g of the functionalized nanodiamond prepared in Comparative Example 1 to 150g of N,N-dimethylformamide, sonicate for 20min, then add 0.6g of triethylamine, stir at 0℃ for 40min, then add 20g of N,N-dimethylformamide solution of 8.6wt% pyrrole modifier at a rate of 1mL / min, stir for 40min, then stir at 22℃ for 30h. After the reaction is complete, centrifuge to collect the precipitate, wash with N,N-dimethylformamide and deionized water, and vacuum dry at 60℃ for 14h to obtain surface-modified nanodiamond. Step 3: Mix 2g of hexagonal boron nitride, 40g of urea and 120g of deionized water, sonicate at 22℃ for 5h, filter, and vacuum dry the resulting solid product at 50℃ for 4h to obtain aminated nano boron nitride. 0.6g of aminated boron nitride nanoparticles were dispersed in 100g of N,N-dimethylformamide and ultrasonically treated for 1h. Then, 1g of surface-modified nanodiamond was added, and the mixture was stirred at 24℃ for 3h. After filtration, the resulting solid product was vacuum dried at 50℃ for 4h to obtain a boron nitride / diamond composite material. Step 4: Add 0.8g of boron nitride / diamond composite material to 100g of N,N-dimethylformamide, sonicate for 40min, and purge with nitrogen for 10min to remove dissolved oxygen in the reaction system. Then add 5.5g of methyl methacrylate monomer and 0.02g of azobisisobutyronitrile. In a closed environment, heat to 86℃ and stir for 7h. After the reaction is complete, centrifuge to collect the precipitate, wash with N,N-dimethylformamide and deionized water, and vacuum dry at 60℃ for 14h to obtain organic-inorganic hybrid filler. Step 5: Add 1g of organic-inorganic hybrid filler to 50g of N,N-dimethylformamide and sonicate for 30min to obtain an organic-inorganic hybrid filler dispersion; add 10g of polyvinylidene fluoride powder to 50g of N,N-dimethylformamide and stir at 60℃ until completely dissolved, then add the above organic-inorganic hybrid filler dispersion, keep the temperature constant, and continue stirring for 6h to obtain a casting solution; The casting solution was uniformly coated onto a glass plate, dried at 110°C for 80 min to remove DMF, and then hot-pressed at 175°C and 9 MPa for 6 min to obtain a polyvinylidene fluoride insulating composite material with a thickness of 20 µm.

[0024] Comparative Example 3 This comparative example discloses a method for preparing a polyvinylidene fluoride insulating composite material, comprising the following steps: Step 1: Add 18.1g gallic acid and 11.13g triethylamine to 200g N,N-dimethylformamide. Then, at 3℃, add 110g of a 12.95wt% N,N-dimethylformamide solution of 5-chloropyrrole-2-carboxaldehyde at a rate of 1.5mL / min. Stir for 30min, then stir at 25℃ for 16h. After the reaction is complete, precipitate the product with deionized water at 8℃, filter, wash, and dry to obtain the pyrrole compound. 21g of pyrrole compound and 7g of 3-buten-1-amine were added to 160g of N,N-dimethylformamide and stirred at 65°C for 8h under a nitrogen atmosphere. After the reaction was completed, the solvent and excess 3-buten-1-amine were removed by rotary evaporation to obtain the pyrrole modifier. Step 2: Mix 3g of hexagonal boron nitride, 45g of urea and 135g of deionized water, sonicate at 25°C for 6h, filter, and vacuum dry the resulting solid product at 55°C for 3.5h to obtain aminated nano boron nitride. 1.2g of aminated boron nitride nanoparticles were dispersed in 125g of N,N-dimethylformamide and sonicated for 1.5h. Then, 1.5g of pyrrole modifier was added and stirred at 25℃ for 2.5h. The mixture was filtered, and the resulting solid product was washed and vacuum dried at 55℃ for 3.5h to obtain modified boron nitride. Step 3: Add 1g of modified boron nitride to 125g of N,N-dimethylformamide, sonicate for 50min, and purge with nitrogen for 15min to remove dissolved oxygen in the reaction system. Then add 7.3g of methyl methacrylate monomer and 0.03g of azobisisobutyronitrile. In a closed environment, heat to 90℃ and stir for 6h. After the reaction is complete, centrifuge to collect the precipitate, wash with N,N-dimethylformamide and deionized water, and vacuum dry at 65℃ for 12h to obtain organic-inorganic hybrid filler. Step 4: Add 2g of organic-inorganic hybrid filler to 65g of N,N-dimethylformamide and sonicate for 45min to obtain an organic-inorganic hybrid filler dispersion; add 12.5g of polyvinylidene fluoride powder to 65g of N,N-dimethylformamide and stir at 65℃ until completely dissolved, then add the above organic-inorganic hybrid filler dispersion, keep the temperature constant, and continue stirring for 5h to obtain a casting solution; The casting solution was uniformly coated onto a glass plate, dried at 120°C for 60 min to remove DMF, and then hot-pressed at 180°C and 10 MPa for 5 min to obtain a polyvinylidene fluoride insulating composite material with a thickness of 20 µm.

[0025] Comparative Example 4 This comparative example discloses a method for preparing a polyvinylidene fluoride insulating composite material, comprising the following steps: Step 1: Add 18.1g gallic acid and 11.13g triethylamine to 200g N,N-dimethylformamide. Then, at 3℃, add 110g of a 12.95wt% N,N-dimethylformamide solution of 5-chloropyrrole-2-carboxaldehyde at a rate of 1.5mL / min. Stir for 30min, then stir at 25℃ for 16h. After the reaction is complete, precipitate the product with deionized water at 8℃, filter, wash, and dry to obtain the pyrrole compound. 21g of pyrrole compound and 7g of 3-buten-1-amine were added to 160g of N,N-dimethylformamide and stirred at 65°C for 8h under a nitrogen atmosphere. After the reaction was completed, the solvent and excess 3-buten-1-amine were removed by rotary evaporation to obtain the pyrrole modifier. Step 2: Add 1g of the functionalized carbon nanotube composite material prepared in Example 1 to 175g of N,N-dimethylformamide, sonicate for 30min, then add 0.9g of triethylamine, stir at 3℃ for 30min, then add 30g of N,N-dimethylformamide solution of 8.6wt% pyrrole modifier at a rate of 1.5mL / min, stir for 50min, then stir at 25℃ for 25h. After the reaction is complete, centrifuge to collect the precipitate, wash with N,N-dimethylformamide and deionized water, and vacuum dry at 65℃ for 12h to obtain the surface-modified nanotube composite material. Step 3: Add 1g of surface-modified nanotube composite material to 125g of N,N-dimethylformamide, sonicate for 50min, and purge with nitrogen for 15min to remove dissolved oxygen in the reaction system. Then add 7.3g of methyl methacrylate monomer and 0.03g of azobisisobutyronitrile. In a closed environment, heat to 90℃ and stir for 6h. After the reaction is completed, collect the precipitate by centrifugation, wash with N,N-dimethylformamide and deionized water, and vacuum dry at 65℃ for 12h to obtain organic-inorganic hybrid filler. Step 4: Add 2g of organic-inorganic hybrid filler to 65g of N,N-dimethylformamide and sonicate for 45min to obtain an organic-inorganic hybrid filler dispersion; add 12.5g of polyvinylidene fluoride powder to 65g of N,N-dimethylformamide and stir at 65℃ until completely dissolved, then add the above organic-inorganic hybrid filler dispersion, keep the temperature constant, and continue stirring for 5h to obtain a casting solution; The casting solution was uniformly coated onto a glass plate, dried at 120°C for 60 min to remove DMF, and then hot-pressed at 180°C and 10 MPa for 5 min to obtain a polyvinylidene fluoride insulating composite material with a thickness of 20 µm.

[0026] Comparative Example 5 This comparative example discloses a method for preparing a polyvinylidene fluoride insulating composite material, comprising the following steps: Step 1: Mix 3g of hexagonal boron nitride, 45g of urea and 135g of deionized water, sonicate at 25°C for 6h, filter, and vacuum dry the resulting solid product at 55°C for 3.5h to obtain aminated nano boron nitride. 1.2g of aminated boron nitride nanoparticles were dispersed in 125g of N,N-dimethylformamide and sonicated for 1.5h. Then, 1.5g of the carbon nanotube composite material prepared in Example 1 was added, and the mixture was stirred at 25°C for 2.5h. After filtration, the resulting solid product was vacuum dried at 55°C for 3.5h to obtain the boron nitride / carbon nanotube composite material. Step 2: Add 2g of boron nitride / carbon nanotube composite material to 65g of N,N-dimethylformamide and sonicate for 45min to obtain a boron nitride / carbon nanotube composite material dispersion; add 12.5g of polyvinylidene fluoride powder to 65g of N,N-dimethylformamide and stir at 65℃ until completely dissolved, then add the above organic-inorganic hybrid filler dispersion, keep the temperature constant, and continue stirring for 5h to obtain a casting solution; The casting solution was uniformly coated onto a glass plate, dried at 120°C for 60 min to remove DMF, and then hot-pressed at 180°C and 10 MPa for 5 min to obtain a polyvinylidene fluoride insulating composite material with a thickness of 20 µm.

[0027] Comparative Example 6 This comparative example discloses a method for preparing a polyvinylidene fluoride insulating composite material, comprising the following steps: Step 1: Add 18.1g gallic acid and 11.13g triethylamine to 200g N,N-dimethylformamide. Then, at 3℃, add 110g of a 12.95wt% N,N-dimethylformamide solution of 5-chloropyrrole-2-carboxaldehyde at a rate of 1.5mL / min. Stir for 30min, then stir at 25℃ for 16h. After the reaction is complete, precipitate the product with deionized water at 8℃, filter, wash, and dry to obtain the pyrrole compound. 21g of pyrrole compound and 7g of 3-buten-1-amine were added to 160g of N,N-dimethylformamide and stirred at 65°C for 8h under a nitrogen atmosphere. After the reaction was completed, the solvent and excess 3-buten-1-amine were removed by rotary evaporation to obtain the pyrrole modifier. Step 2: Add 1g of the functionalized carbon nanotube composite material prepared in Example 1 to 175g of N,N-dimethylformamide, sonicate for 30min, then add 0.9g of triethylamine, stir at 3℃ for 30min, then add 30g of N,N-dimethylformamide solution of 8.6wt% pyrrole modifier at a rate of 1.5mL / min, stir for 50min, then stir at 25℃ for 25h. After the reaction is complete, centrifuge to collect the precipitate, wash with N,N-dimethylformamide and deionized water, and vacuum dry at 65℃ for 12h to obtain the surface-modified nanotube composite material. Step 3: Mix 3g of hexagonal boron nitride, 45g of urea and 135g of deionized water, sonicate at 25°C for 6h, filter, and vacuum dry the resulting solid product at 55°C for 3.5h to obtain aminated nano boron nitride. 1.2g of aminated boron nitride nanoparticles were dispersed in 125g of N,N-dimethylformamide and sonicated for 1.5h. Then, 1.5g of surface-modified nanotube composite material was added, stirred at 25℃ for 2.5h, filtered, and the resulting solid product was vacuum dried at 55℃ for 3.5h to obtain boron nitride / carbon nanotube composite material. Step 4: Add 2g of boron nitride / carbon nanotube composite material to 65g of N,N-dimethylformamide and sonicate for 45min to obtain a boron nitride / carbon nanotube composite material dispersion; add 12.5g of polyvinylidene fluoride powder to 65g of N,N-dimethylformamide and stir at 65℃ until completely dissolved, then add the above organic-inorganic hybrid filler dispersion, keep the temperature constant, and continue stirring for 5h to obtain a casting solution; The casting solution was uniformly coated onto a glass plate, dried at 120°C for 60 min to remove DMF, and then hot-pressed at 180°C and 10 MPa for 5 min to obtain a polyvinylidene fluoride insulating composite material with a thickness of 20 µm.

[0028] In the above examples and comparative examples, the aminated multi-walled carbon nanotubes had a diameter of 5-15 nm, a length of 10-50 μm, and a purity greater than 95%, and were purchased from Chengdu Jiacai Technology Co., Ltd.; the nanodiamonds (ND, purity ≥97%) had a particle size range of 5-10 nm and were purchased from Nanjing Xianfeng Nanomaterials Technology Co., Ltd.; the hexagonal boron nitride had an average thickness of 50 nm and was purchased from Beijing Deco Island Gold Technology Co., Ltd.; and the polyvinylidene fluoride powder, grade HR460, was purchased from Dongguan Hechuang Plastics Co., Ltd.

[0029] Experimental Example The performance of the polyvinylidene fluoride insulating composite materials prepared in Examples 2-4 and Comparative Examples 2-6 was tested: I. Mechanical property testing: Referring to GB / T 1040.1-2006, a small universal testing machine was used to test the mechanical tensile properties. The samples were prepared into 50mm×10mm rectangular strips and stretched at a constant tensile speed of 1mm / min. Each sample was tested 3 times and the average value was taken. II. Thermal conductivity test: The thermal conductivity of the samples was measured using a thermal conductivity meter. The instrument uses transient hot wire technology. Each sample was tested repeatedly 5 times and the average value was taken. III. Insulation performance test: Each group of samples was prepared into 5×10mm pieces, and the resistivity was tested at room temperature using a physical performance tester.

[0030] The test results are shown in Table 1: Table 1 As can be seen from the test results in Table 1, the polyvinylidene fluoride insulating composite materials prepared in Examples 2-4 of this invention simultaneously exhibit excellent insulation performance, thermal conductivity, and mechanical properties. As can be seen from the comparison between Comparative Examples 2-4 and Example 4, the present invention combines nanodiamond, multi-walled carbon nanotubes, and nano-boron nitride to give the organic-inorganic hybrid filler a thermally conductive network and an insulating network with a "point-line-surface" structure, thereby improving the insulation and thermal conductivity of the polyvinylidene fluoride insulating composite material. However, compared with Example 4, Comparative Example 2 has a higher volume resistivity. This is because multi-walled carbon nanotubes themselves have good conductivity but poor electrical insulation effect. Nanodiamond and boron nitride are needed to block the electrical conductivity so that the composite material can maintain excellent insulation performance. Furthermore, the nanodiamond, multi-walled carbon nanotubes, and nano-boron nitride in the organic-inorganic hybrid filler act as inorganic reinforcing fillers, improving the mechanical properties of the polyvinylidene fluoride insulating composite material. As can be seen from the comparison between Comparative Examples 5-6 and Example 4, the organic-inorganic hybrid filler of the present invention includes pyrrole nitrogen and phenolic hydroxyl groups introduced by the pyrrole modifier, as well as polymethyl methacrylate chains formed by the polymerization of methyl methacrylate monomers. The pyrrole nitrogen and phenolic hydroxyl groups in the pyrrole modifier can form hydrogen bonds with polyvinylidene fluoride. The polymethyl methacrylate chains can not only form hydrogen bonds with polyvinylidene fluoride, but also form physical entanglements with the polymer chains of polyvinylidene fluoride. The combined effect of the above-mentioned multiple organic structures promotes the uniform dispersion of the organic-inorganic hybrid filler in polyvinylidene fluoride, thereby further improving the comprehensive performance of polyvinylidene fluoride insulating composite materials.

[0031] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a polyvinylidene fluoride insulating composite material, characterized in that, Includes the following steps: Step 1: Gallic acid reacts with 5-chloropyrrole-2-carboxaldehyde to obtain a pyrrole compound; the pyrrole compound reacts with 3-buten-1-amine to obtain a pyrrole-modifying agent; Step 2: Modify the functionalized carbon nanotube composite material with a pyrrole modifier to obtain a surface-modified nanotube composite material. The functionalized carbon nanotube composite material is obtained by acyl chloride treatment of carbon nanotube composite material, the carbon nanotube composite material is obtained by depositing oxidized nanodiamond on aminated multi-walled carbon nanotube, and the oxidized nanodiamond is obtained by oxidizing nanodiamond with hydrogen peroxide aqueous solution. Step 3: Hexagonal boron nitride, urea, and deionized water are reacted to obtain aminated boron nitride nanoparticles; the aminated boron nitride nanoparticles are then combined with surface-modified nanotube composite materials to obtain boron nitride / carbon nanotube composite materials. Step 4: Graft organic polymer chains onto the surface of the boron nitride / carbon nanotube composite material to obtain an organic-inorganic hybrid filler; Step 5: Using organic-inorganic hybrid filler and polyvinylidene fluoride as raw materials, cast film and hot press to obtain polyvinylidene fluoride insulating composite material.

2. The method for preparing the polyvinylidene fluoride insulating composite material according to claim 1, characterized in that, In step one, the pyrrole modifier is prepared by the following method: Gallic acid and triethylamine were added to N,N-dimethylformamide, and then a 12.95wt% solution of 5-chloropyrrole-2-carboxaldehyde in N,N-dimethylformamide was added at 0-5℃. The mixture was stirred for 20-40 min, and then stirred at 22-28℃ for 12-20 h to purify the product and obtain the pyrrole compound. The mass ratio of gallic acid, triethylamine, N,N-dimethylformamide, and the 12.95wt% solution of 5-chloropyrrole-2-carboxaldehyde in N,N-dimethylformamide was (17.01-20.4):(10.12-12.14):(150-250):(100-120). Pyrrole compound and 3-buten-1-amine were added to N,N-dimethylformamide and stirred at 60-70°C for 6-10 h under a nitrogen atmosphere. The product was purified to obtain a pyrrole modifier. The mass ratio of the pyrrole compound, 3-buten-1-amine and N,N-dimethylformamide was (115.7-26.3):(6.2-7.8):(140-180).

3. The method for preparing the polyvinylidene fluoride insulating composite material according to claim 1, characterized in that, In step two, the surface-modified nanotube composite material is prepared by the following method: The functionalized carbon nanotube composite material was added to N,N-dimethylformamide and sonicated. Then triethylamine was added, and the mixture was stirred at 0-5℃ for 20-40 min. Next, a solution of N,N-dimethylformamide with 8.6 wt% pyrrole modifier was added, and the mixture was stirred for 40-60 min. Then, the mixture was stirred at 22-28℃ for 20-30 h, and the product was purified to obtain the surface-modified nanotube composite material. The mass ratio of the functionalized carbon nanotube composite material, N,N-dimethylformamide, triethylamine, and the N,N-dimethylformamide solution with 8.6 wt% pyrrole modifier was (0.5-1.5):(150-200):(0.6-1.2):(20-40).

4. The method for preparing the polyvinylidene fluoride insulating composite material according to claim 1, characterized in that, In step two, the preparation method of the functionalized carbon nanotube composite material includes the following steps: Step A1: At 70-80℃, add nanodiamond to a 30wt% hydrogen peroxide aqueous solution with a solid-liquid mass ratio of 1:(300-500), soak for 20-30 hours, and purify to obtain oxidized nanodiamond; Step A2: Add nanodiamond oxide and dimethylaminopyridine to N,N-dimethylformamide, sonicate, then add 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide, stir at 22-28℃ for 40-80 min, then add aminated multi-walled carbon nanotube dispersion, stir and react at 22-28℃ for 10-14 h, purify, and obtain carbon nanotube composite material; wherein, the mass ratio of aminated multi-walled carbon nanotubes, nanodiamond oxide, dimethylaminopyridine, and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide is (1.4-2.4):(0.8-1.2):(0.2-0.4):(0.2-0.4); Step A3: Mix carbon nanotube composite material and thionyl chloride at a mass ratio of (0.5-1.5):(250-350), stir and react at 60-70℃ for 20-30h, and then rotary evaporate to obtain functionalized carbon nanotube composite material.

5. The method for preparing the polyvinylidene fluoride insulating composite material according to claim 1, characterized in that, In step three, the preparation method of the boron nitride / carbon nanotube composite material is as follows: Hexagonal boron nitride, urea and deionized water were mixed in a mass ratio of (2-4):(40-50):(120-150), ultrasonically treated at 22-28℃ for 5-7 hours, filtered and dried to obtain aminated nano boron nitride. Aminated boron nitride nanoparticles were dispersed in N,N-dimethylformamide, sonicated, and then surface-modified nanotube composite material was added. The mixture was stirred at 24-27℃ for 2-3 hours, filtered, and dried to obtain boron nitride / carbon nanotube composite material. The mass ratio of the aminated boron nitride nanoparticles, N,N-dimethylformamide, and surface-modified nanotube composite material was (0.6-1.8):(100-150):(1-2).

6. The method for preparing the polyvinylidene fluoride insulating composite material according to claim 1, characterized in that, In step four, the preparation method of the organic-inorganic hybrid filler is as follows: Boron nitride / carbon nanotube composite material was added to N,N-dimethylformamide, sonicated, and nitrogen gas was introduced for 10-20 min. Then methyl methacrylate and azobisisobutyronitrile were added. The mixture was heated to 86-94℃ and stirred for 5-7 h in a closed environment. The product was purified to obtain an organic-inorganic hybrid filler. The mass ratio of the boron nitride / carbon nanotube composite material, N,N-dimethylformamide, methyl methacrylate, and azobisisobutyronitrile was (0.8-1.2):(100-150):(5.5-9.1):(0.02-0.04).

7. The method for preparing the polyvinylidene fluoride insulating composite material according to claim 1, characterized in that, In step five, the preparation method of the polyvinylidene fluoride insulating composite material is as follows: Organic-inorganic hybrid filler and N,N-dimethylformamide were mixed at a mass ratio of (1-3):(50-80) to obtain an organic-inorganic hybrid filler dispersion; polyvinylidene fluoride and N,N-dimethylformamide were mixed at a mass ratio of (10-15):(50-80) and stirred at 60-70℃ until completely dissolved. Then, the above organic-inorganic hybrid filler dispersion was added, and the temperature was kept constant. Stirring was continued for 4-6 hours to obtain a casting solution. The casting solution was uniformly coated onto a glass plate, dried, and hot-pressed to obtain a polyvinylidene fluoride insulating composite material with a thickness of 15-25µm.

8. The method for preparing the polyvinylidene fluoride insulating composite material according to claim 7, characterized in that, The drying conditions are: temperature 110-130℃, time 40-80min; the hot pressing conditions are: temperature 175-185℃, pressure 9-11MPa, time 4-6min.

9. A polyvinylidene fluoride insulating composite material prepared by the method for preparing polyvinylidene fluoride insulating composite material as described in any one of claims 1-8.

10. The application of the polyvinylidene fluoride insulating composite material according to claim 9 in electronic and electrical materials.

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