A method for preparing a nacreous layered montmorillonite-based inorganic insulating film

Abstract

A method for preparing a nacre-layered montmorillonite-based inorganic insulating film includes the following steps: Step 1, preparing the following raw materials: montmorillonite, N-methyl-2-pyrrolidone, polyvinylpyrrolidone, and polyvinylidene fluoride-hexafluoropropylene; Step 2, preparing a two-dimensional nano-montmorillonite dispersion; Step 3, coating with polyvinylidene fluoride-hexafluoropropylene; Step 4, molding the inorganic insulating film; Step 5, drying the inorganic insulating film; and Step 6, thermal coupling treatment of the inorganic insulating film. This material exhibits excellent electrical insulation properties, with a nonlinear coefficient as high as 10.66, a breakdown field strength of up to 224.3 kV / mm, and a corona resistance time of up to 1287.6 min under a high electric field of 80 kV / mm. By adjusting the content of polyvinylidene fluoride-hexafluoropropylene, the conductivity and nonlinear coefficient of the material can be flexibly adjusted to meet diverse application requirements.

Description

Technical Field

[0001] This invention belongs to the technical field of anti-corona insulation materials, and specifically relates to a method for preparing a nacreous montmorillonite-based inorganic insulating film. Background Technology

[0002] With the rapid development of my country's modern power system and deep space exploration, modern electrical equipment is rapidly evolving towards miniaturization and high power. This trend places more stringent requirements on electrical insulation materials, especially in terms of insulation reliability. Although the application and development of traditional materials such as metals, ceramics, mica paper, and polymers in extreme environments have been studied, each has its limitations. While metals and ceramics have excellent mechanical properties and are resistant to extreme environments, metals are limited by their high density, and ceramics are difficult to shape due to their brittleness. On the other hand, although mica paper has excellent electrical insulation, thermal stability, and chemical stability, its poor microscopic uniformity and low stress transfer efficiency between microscopic components result in insufficient mechanical properties and dielectric strength, and its excessive thickness makes it unsuitable for miniaturized high-power electrical equipment. Polymer materials, while uniform, lightweight, thin, and with good ductility, generally suffer from insufficient corona resistance. Materials selected by nature, through continuous optimization during evolution, are often seen as a source of inspiration for high-performance and high-efficiency solutions. It is crucial to develop novel structural materials that possess both superior performance and meet the requirements of sustainable development by conducting in-depth research on the formation mechanisms and self-assembly processes of biomaterials in nature. Summary of the Invention

[0003] To overcome the shortcomings of the prior art, the purpose of this invention is to provide a method for preparing a nacreous layered montmorillonite-based inorganic insulating film. Addressing the deficiencies in the prior art, this invention focuses on controlling the orientation, order, density, and interfacial interactions of two-dimensional nanomaterial structures. Using typical natural two-dimensional layered nanomaterials such as montmorillonite, and employing vacuum-assisted self-assembly and thermo-coupling techniques, an inorganic insulating film with nonlinear conductivity and high anti-corona discharge properties is prepared.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is: a method for preparing a nacreous montmorillonite-based inorganic insulating film, comprising the following steps:

[0005] Step 1, prepare the following raw materials: montmorillonite, N-methyl-2-pyrrolidone, polyvinylpyrrolidone, and polyvinylidene fluoride-hexafluoropropylene;

[0006] Step 2, Preparation of two-dimensional nano-montmorillonite dispersion;

[0007] Step 3, coating of polyvinylidene fluoride-hexafluoropropylene;

[0008] Step 4, forming of inorganic insulating film;

[0009] Step 5, drying of the inorganic insulating film;

[0010] Step 6: Thermal coupling treatment of the inorganic insulating film.

[0011] In step 1, the montmorillonite is unpeeled sodium-based montmorillonite raw material.

[0012] Step 2, the two-dimensional nano-montmorillonite dispersion, is prepared by a chemical-mechanical exfoliation method. The specific steps are as follows:

[0013] Dissolve 1.5-2.5g of montmorillonite raw material in 300-500mL of N-methyl-2-pyrrolidone solution and stir magnetically for 10-20min to obtain montmorillonite dispersion. Then slowly add 18-30g of polyvinylpyrrolidone and continue stirring for 12-20h. After standing for 48-72h, take the supernatant to obtain two-dimensional nano-montmorillonite dispersion.

[0014] The montmorillonite raw material is pre-dried in an 80-90℃ forced-air drying oven for 6-8 hours to remove residual moisture.

[0015] The magnetic stirring speed is 3000-3200 rpm.

[0016] The polyvinylpyrrolidone was divided into three equal parts, and each part was added slowly at 5-7 minute intervals.

[0017] Step 3, the coating of polyvinylidene fluoride-hexafluoropropylene, involves adding 1%-5% of polyvinylidene fluoride-hexafluoropropylene by mass of nano-montmorillonite to a two-dimensional nano-montmorillonite dispersion, followed by ultrasonic treatment for 30-40 minutes and continued stirring for 1-2 hours to obtain a two-dimensional nano-montmorillonite dispersion coated with polyvinylidene fluoride-hexafluoropropylene.

[0018] In step 4, the inorganic insulating film is formed by using a vacuum filtration device to filter a two-dimensional nano-montmorillonite dispersion coated with polyvinylidene fluoride-hexafluoropropylene. The directional flow rate of the liquid is used to orient the nanosheets so that they are arranged in parallel on filter paper with an average pore size of 220 μm, thus obtaining a moist inorganic insulating film.

[0019] Step 5, the drying treatment of the inorganic insulating film, involves placing the moistened film in a forced-air drying oven at 80-90℃ and drying it for 6-8 hours.

[0020] Step 6, the thermo-coupling treatment of the inorganic insulating film, involves placing the dried film from step 5 on a hot press and hot-pressing it for 30-50 minutes at a temperature of 180-200℃ and a pressure of 18-20 MPa, ultimately obtaining a montmorillonite inorganic insulating film with a pearl-like structure.

[0021] This invention employs a biomimetic manufacturing strategy, which is expected to gradually replace traditional methods for manufacturing insulating materials. The core of this strategy lies in mimicking the hierarchical structure and interfacial interactions of biological materials in nature to achieve multifunctional artificial materials. By carefully designing the microstructure of the material, its performance can be significantly improved. In this process, utilizing nanomaterials with different functions endows the composite material with more intelligent characteristics. Moreover, this strategy has good universality and can be better applied to two-dimensional nanomaterials. By precisely controlling the arrangement and distribution of two-dimensional nanomaterials, the key properties of the composite material, such as mechanical properties, thermal stability, and electrical conductivity, can be effectively optimized, thereby promoting the development of high-performance composite materials. For example, materials such as graphene with excellent electrical conductivity and montmorillonite nanosheets with flame-retardant properties can be used as reinforcing phases. They not only enhance the mechanical properties of the base material but also provide additional functions, such as electrical conductivity or flame retardancy. The realization of this intelligent functionality relies on the synergistic effect between the nanomaterial and the matrix, as well as interface engineering at the nanoscale. By precisely controlling the dispersion, interfacial compatibility, and interaction forces of the nanocomponents, the overall performance of the composite material can be optimized, enabling it to perform excellently in specific application environments.

[0022] The beneficial effects of this invention are:

[0023] Compared with existing technologies, this invention combines vacuum-assisted self-assembly with thermo-coupling to construct a pearl-like layered structure. Simultaneously, polyvinylidene fluoride (PVDF)-hexafluoropropylene (HCF) is added during film formation to increase interlayer interaction of nanosheets, reduce defects, and prepare an anti-corona discharge inorganic insulating film with nonlinear conductivity. Vacuum-assisted self-assembly improves the orientation of nanosheets, maximizing their two-dimensional characteristics. The parallel stacking of two-dimensional nanosheets maximizes the dielectric strength perpendicular to the cleavage planes of the nanosheets. Thermo-coupling technology further increases the density between layers, improving the material's insulation properties. Through the above treatments, the inorganic insulating film with a pearl-like layered structure obtained by this invention achieves a nonlinear coefficient of 10.66, a maximum breakdown field strength of 224.3 kV / mm, and a corona resistance time of 1287.6 min at an 80 kV / mm field strength. By adjusting the PVDF-HCF content, the conductivity and nonlinear coefficient of the film can be changed, thus allowing for applications in various practical situations. Attached Figure Description

[0024] Figure 1This is a flowchart illustrating the preparation process of the nacreous layered montmorillonite-based inorganic insulating film of the present invention.

[0025] Figure 2 This is a physical image of the pearl-layered montmorillonite-based inorganic insulating film obtained in Example 1 of the present invention.

[0026] Figure 3 This is a cross-sectional scanning electron microscope image of the nacreous layered montmorillonite-based inorganic insulating film obtained in Example 1 of the present invention.

[0027] Figure 4 This is a graph showing the nonlinear conductivity characteristics of the nacreous montmorillonite-based inorganic insulating films obtained in Embodiments 1, 2, 3 and Comparative Example 1 of this invention.

[0028] Figure 5 This is a breakdown characteristic diagram of the nacreous layered montmorillonite-based inorganic insulating film obtained in Embodiments 1, 2, 3 and Comparative Example 1 of the present invention.

[0029] Figure 6 This is a bar chart showing the corona resistance of the nacreous montmorillonite-based inorganic insulating film obtained in Embodiment 2 and Comparative Example 1 of the present invention. Detailed Implementation

[0030] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0031] A method for preparing a nacreous montmorillonite-based inorganic insulating film involves first dissolving montmorillonite raw material in N-methyl-2-pyrrolidone and stirring until homogeneous; then adding polyvinylpyrrolidone and continuing stirring, followed by standing to obtain a two-dimensional nano-montmorillonite dispersion; subsequently adding a small amount of polyvinylidene fluoride-hexafluoropropylene and ultrasonically stirring to form a novel dispersion; preparing a moist inorganic insulating film using vacuum-assisted self-assembly technology; drying the film and then hot-pressing it to finally obtain a montmorillonite-based inorganic insulating film with a nacreous layered structure. Example

[0032] A method for preparing a nacreous layered montmorillonite-based inorganic insulating film, which is prepared by combining vacuum-assisted self-assembly and thermo-coupling technology, includes the following steps:

[0033] Step 1, prepare the following raw materials: including unpeeled sodium montmorillonite, N-methyl-2-pyrrolidone, polyvinylpyrrolidone, and polyvinylidene fluoride-hexafluoropropylene;

[0034] Step 2: Two-dimensional nano-montmorillonite is prepared by chemical-mechanical exfoliation. The montmorillonite raw material is dried in an 80℃ forced-air drying oven for 6 hours in advance to remove residual moisture.

[0035] 1.5g of montmorillonite raw material was dissolved in 300mL of N-methyl-2-pyrrolidone solution and magnetically stirred for 10min at 3000rpm to obtain montmorillonite dispersion.

[0036] 18% polyvinylpyrrolidone was divided into three equal parts, and each part was slowly added to the montmorillonite dispersion at 5-minute intervals. The mixture was stirred for 12 hours and then allowed to stand for 48 hours. The supernatant was then collected to obtain a two-dimensional nano-montmorillonite dispersion.

[0037] Step 3: Add 1% (by weight of nano-montmorillonite) of polyvinylidene fluoride-hexafluoropropylene to the nano-montmorillonite dispersion, then sonicate for 30 min and continue stirring for 1 h to obtain a two-dimensional nano-montmorillonite dispersion coated with polyvinylidene fluoride-hexafluoropropylene.

[0038] Step 4: The polyvinylidene fluoride-hexafluoropropylene coated nano-montmorillonite dispersion is filtered using a vacuum filtration device. The directional flow rate of the liquid is used to orient the nanosheets so that they are arranged in parallel on filter paper with an average pore size of 220 μm, resulting in a moist inorganic insulating film.

[0039] Step 5: Place the moistened film in a forced-air drying oven at 80°C and dry for 6 hours.

[0040] Step 6: Place the dried film on a hot press and hot press for 30 minutes at a temperature of 180℃ and a pressure of 18 MPa to finally obtain a montmorillonite inorganic insulating film with a layered structure.

[0041] Figure 2 This is a photograph of the nacreous montmorillonite-based inorganic insulating film obtained in Example 1 of this invention. As can be seen from the figure, the inorganic film has a smooth surface and a certain degree of flexibility.

[0042] Figure 3 This is a cross-sectional scanning electron microscope (SEM) image of the nacreous montmorillonite-based inorganic insulating film obtained in Example 1 of this invention. The microscopic morphology of the cross-section shows that the inorganic insulating film consists of numerous tightly arranged montmorillonite nanosheets forming a parallel, stacked layered structure, similar to the structure of nacre. This structure not only exhibits a high degree of order, but the tight stacking also endows the material with excellent insulating properties. Example

[0043] A method for preparing a nacreous montmorillonite-based inorganic insulating film includes the following steps:

[0044] Step 1, prepare the following raw materials: including unpeeled sodium montmorillonite, N-methyl-2-pyrrolidone, polyvinylpyrrolidone, and polyvinylidene fluoride-hexafluoropropylene;

[0045] Step 2: Two-dimensional nano-montmorillonite is prepared by chemical-mechanical exfoliation. The montmorillonite raw material is dried in an 85℃ forced-air drying oven for 7 hours in advance to remove residual moisture.

[0046] Dissolve 2g of montmorillonite raw material in 400mL of N-methyl-2-pyrrolidone solution and stir magnetically for 15min at 3100rpm to obtain montmorillonite dispersion;

[0047] 24g of polyvinylpyrrolidone was divided into three equal parts, and each part was slowly added to the montmorillonite dispersion at 6min intervals. The mixture was stirred for 16h and then allowed to stand for 60h. The supernatant was then collected to obtain a two-dimensional nano-montmorillonite dispersion.

[0048] Step 3: Add 3% by weight of polyvinylidene fluoride-hexafluoropropylene to the nano-montmorillonite dispersion, then sonicate for 35 min and continue stirring for 1.5 h to obtain a two-dimensional nano-montmorillonite dispersion coated with polyvinylidene fluoride-hexafluoropropylene.

[0049] Step 4: The polyvinylidene fluoride-hexafluoropropylene coated nano-montmorillonite dispersion is filtered using a vacuum filtration device. The directional flow rate of the liquid is used to orient the nanosheets so that they are arranged in parallel on filter paper with an average pore size of 220 μm, resulting in a moist inorganic insulating film.

[0050] Step 5: Place the moistened film in a forced-air drying oven at 85°C and dry for 7 hours.

[0051] Step 6: Place the dried film on a hot press and hot press for 40 minutes at a temperature of 190℃ and a pressure of 19 MPa to finally obtain a montmorillonite inorganic insulating film with a layered structure. Example

[0052] A method for preparing a nacreous montmorillonite-based inorganic insulating film includes the following steps:

[0053] Step 1, prepare the following raw materials: including unpeeled sodium montmorillonite, N-methyl-2-pyrrolidone, polyvinylpyrrolidone, and polyvinylidene fluoride-hexafluoropropylene;

[0054] Step 2: Two-dimensional nano-montmorillonite is prepared by chemical-mechanical exfoliation. The montmorillonite raw material is dried in a 90℃ forced-air drying oven for 8 hours in advance to remove residual moisture.

[0055] 2.5g of montmorillonite raw material was dissolved in 500mL of N-methyl-2-pyrrolidone solution and magnetically stirred for 20min at 3200rpm to obtain montmorillonite dispersion.

[0056] 30g of polyvinylpyrrolidone was divided into three equal parts, and each part was slowly added to the montmorillonite dispersion at 7min intervals. The mixture was stirred for 20h and then allowed to stand for 72h. The supernatant was then collected to obtain the two-dimensional nano-montmorillonite dispersion.

[0057] Step 3: Add 5% by weight of polyvinylidene fluoride-hexafluoropropylene to the nano-montmorillonite dispersion, then sonicate for 40 min, and continue stirring for 2 h to obtain a two-dimensional nano-montmorillonite dispersion coated with polyvinylidene fluoride-hexafluoropropylene.

[0058] Step 4: The polyvinylidene fluoride-hexafluoropropylene coated nano-montmorillonite dispersion is filtered using a vacuum filtration device. The directional flow rate of the liquid is used to orient the nanosheets so that they are arranged in parallel on filter paper with an average pore size of 220 μm, resulting in a moist inorganic insulating film.

[0059] Step 5: Place the moistened film in a 90°C forced-air drying oven and dry for 8 hours.

[0060] Step 6: Place the dried film on a hot press and hot press for 50 minutes at a temperature of 200℃ and a pressure of 20 MPa to finally obtain a montmorillonite inorganic insulating film with a layered structure.

[0061] Comparative Example 1

[0062] In the preparation of montmorillonite-based inorganic insulating films, pure montmorillonite inorganic film comparative samples were prepared without the addition of polyvinylidene fluoride-hexafluoropropylene. The specific steps are as follows:

[0063] Step 1, prepare the following raw materials: including unpeeled sodium montmorillonite and N-methyl-2-pyrrolidone;

[0064] Step 2, preparation of two-dimensional nano-montmorillonite dispersion. Two-dimensional nano-montmorillonite is prepared by chemical-mechanical exfoliation. The montmorillonite raw material is dried in an 80℃ forced-air drying oven for 6 hours in advance to remove residual moisture.

[0065] 1.5g of montmorillonite raw material was dissolved in 300mL of N-methyl-2-pyrrolidone solution and magnetically stirred for 10min at 3000rpm to obtain montmorillonite dispersion.

[0066] 18g of polyvinylpyrrolidone was divided into three equal parts, and each part was slowly added to the montmorillonite dispersion at 5min intervals. The mixture was stirred for 12h and then allowed to stand for 48h. The supernatant was then collected to obtain the two-dimensional nano-montmorillonite dispersion.

[0067] Step 3: The nano-montmorillonite dispersion is filtered using a vacuum filtration device. The directional flow rate of the liquid is used to orient the nanosheets so that they are arranged in parallel on filter paper with an average pore size of 220 μm, resulting in a moist inorganic insulating film.

[0068] Step 4: Place the moistened film in a forced-air drying oven at 80°C and dry for 6 hours.

[0069] Step 5: Place the dried film on a hot press and hot press for 30 minutes at a temperature of 180℃ and a pressure of 18 MPa to finally obtain a montmorillonite inorganic insulating film with a layered structure.

[0070] Figure 4 These are nonlinear characteristic curves of the nacreous montmorillonite-based inorganic insulating films obtained in Examples 1, 2, 3, and Comparative Example 1 of this invention. As can be seen from the figures, the inorganic films exhibit significant nonlinear conductivity characteristics. The conductivity and nonlinear coefficient increase after the addition of polyvinylidene fluoride-hexafluoropropylene. β With further increases, the nonlinear coefficient reaches a maximum of 10.66.

[0071] Figure 5 This is a breakdown characteristic curve of the nacreous montmorillonite-based inorganic insulating film obtained in Examples 1, 2, 3, and Comparative Example 1 of this invention. As can be seen from the figure, the inorganic film, after the addition of polyvinylidene fluoride-hexafluoropropylene, achieved a maximum breakdown field strength of 224.3 kV / mm, exhibiting excellent insulation properties.

[0072] Figure 6 This is a bar chart showing the corona resistance time of the nacreous montmorillonite-based inorganic insulating films obtained in Example 2 and Comparative Example 1 of this invention. As can be seen from the figure, the corona resistance time of the inorganic film increased by 58.8% after the addition of polyvinylidene fluoride-hexafluoropropylene, demonstrating excellent anti-corona properties.

Claims

1. A method for preparing a nacreous montmorillonite-based inorganic insulating film, characterized in that, Includes the following steps: Step 1, prepare the following raw materials: montmorillonite, N-methyl-2-pyrrolidone, polyvinylpyrrolidone, and polyvinylidene fluoride-hexafluoropropylene; In step 1, the montmorillonite is unpeeled sodium-based montmorillonite raw material; Step 2, Preparation of two-dimensional nano-montmorillonite dispersion; Step 2, the two-dimensional nano-montmorillonite dispersion, is prepared by a chemical-mechanical exfoliation method. The specific steps are as follows: Dissolve 1.5-2.5g of montmorillonite raw material in 300-500mL of N-methyl-2-pyrrolidone solution and stir magnetically for 10-20min to obtain montmorillonite dispersion. Then slowly add 18-30g of polyvinylpyrrolidone and continue stirring for 12-20h. Let stand for 48-72h and take the supernatant to obtain two-dimensional nano-montmorillonite dispersion. Step 3, coating of polyvinylidene fluoride-hexafluoropropylene; Step 3, coating of polyvinylidene fluoride-hexafluoropropylene, involves adding 1%-5% of polyvinylidene fluoride-hexafluoropropylene by mass of nano-montmorillonite to a two-dimensional nano-montmorillonite dispersion, followed by ultrasonic treatment for 30-40 minutes and continued stirring for 1-2 hours to obtain a two-dimensional nano-montmorillonite dispersion coated with polyvinylidene fluoride-hexafluoropropylene. Step 4, forming of inorganic insulating film; In step 4, the inorganic insulating film is formed by using a vacuum filtration device to filter the two-dimensional nano-montmorillonite dispersion coated with polyvinylidene fluoride-hexafluoropropylene. The directional flow rate of the liquid is used to orient the nanosheets so that they are arranged in parallel on the filter paper with an average pore size of 220 μm, thus obtaining a moist inorganic insulating film. Step 5, drying of the inorganic insulating film; Step 6: Thermal coupling treatment of the inorganic insulating film; The inorganic insulating film has a nonlinear coefficient of 10.66, a maximum breakdown field strength of 224.3 kV / mm, and a corona withstand time of 1287.6 min at a field strength of 80 kV / mm. Step 6, the thermo-coupling treatment of the inorganic insulating film, involves placing the dried film from step 5 on a hot press and hot-pressing it for 30-50 minutes at a temperature of 180-200℃ and a pressure of 18-20 MPa, ultimately obtaining a montmorillonite inorganic insulating film with a pearl-like structure.

2. The method for preparing a nacreous layered montmorillonite-based inorganic insulating film according to claim 1, characterized in that, The montmorillonite raw material is pre-dried in an 80-90℃ forced-air drying oven for 6-8 hours to remove residual moisture.

3. The method for preparing a nacreous layered montmorillonite-based inorganic insulating film according to claim 1, characterized in that, The magnetic stirring speed is 3000-3200 rpm.

4. The method for preparing a nacreous layered montmorillonite-based inorganic insulating film according to claim 1, characterized in that, The polyvinylpyrrolidone was divided into three equal parts, and each part was added slowly at 5-minute intervals.

5. The method for preparing a nacreous layered montmorillonite-based inorganic insulating film according to claim 1, characterized in that, Step 5, the drying treatment of the inorganic insulating film, involves placing the moistened film in a forced-air drying oven at 80-90℃ and drying it for 6-8 hours.

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