Metaparamid aramid nanocomposite paper and method of making same

Abstract

The application relates to a meta-aramid nanocomposite paper and a preparation method thereof, the preparation method comprising the following steps: S1, providing meta-aramid paper, meta-aramid stock solution and a dissolving solution, wherein the dissolving solution comprises a chlorinated salt and a first organic solvent; S2, mixing the meta-aramid stock solution with inorganic nanoparticles and a ferroelectric polymer in a second organic solvent to obtain a reinforcing solution; S3, placing the meta-aramid paper in the dissolving solution, carrying out ultrasonic treatment and drying, and coating the reinforcing solution on the surface of the meta-aramid paper after drying; and S4, carrying out annealing polarization treatment on the meta-aramid paper after the reinforcing solution is coated, so as to obtain the meta-aramid nanocomposite paper. According to the preparation method, MAP is used as a base, the chlorinated salt is dissolved in a strong-polarity organic solvent as a dissolving solution, and the meta-aramid stock solution and IN are dissolved in a strong-polarity organic solvent as a reinforcing solution, so that the mechanical durability, insulation reliability and service life of the existing meta-aramid-based insulating paper can be improved.

Description

Technical Field

[0001] The invention relates to meta-aramid nano-composite paper and a preparation method thereof, and belongs to the field of insulating material preparation. Background Art

[0002] Meta-aramid Fiber (MA) has excellent electrical insulation properties and chemical stability. Meta-aramid Paper (MAP) is made of meta-aramid pulp (precipitated fibers) and chopped fibers through wet molding and hot pressing, referring to the preparation process of cellulose-based paper. It is widely used in the insulation structure of electrical equipment such as oil-cooled motors and offshore generators. With the development of new energy vehicle technology, the development and application of 800V high-voltage drive motors have put forward more stringent requirements on the electrical and mechanical properties of insulation materials. The surface roughness and porosity of MAP will affect the insulation strength and even cause partial discharge and lamination breakdown. Improving the mechanical strength and corona resistance of MAP is of great significance to extending the safe service life, improving reliability, and thus ensuring the long-term safe operation of insulation structures and electrical equipment.

[0003] Nano-modification is an effective method for improving the overall performance of polymer materials. In 1994, DuPont (USA) successfully developed Kapton CR and Kapton FCR films, which exhibit excellent corona resistance, by filling a polyimide precursor with nano-alumina particles. This improved the films' corona resistance by more than tenfold. Applying these inorganic nano-hybrid ferroelectric polymer nanocomposites to electrical insulation can effectively enhance the corona resistance of products and equipment.

[0004] However, the current existing preparation method requires a precipitated fiber re-dissolution process, which is cumbersome and the cost of using base paper recycled composite paper is high.

[0005] Therefore, selecting suitable modified materials and improving their interfacial bonding ability with MAP, while obtaining a denser structure to achieve high strength and high insulation, is a current research hotspot. Summary of the Invention

[0006] The object of the present invention is to provide a meta-aramid nanocomposite paper infiltrated with a ferroelectric polymer and a preparation method thereof, so as to improve the mechanical durability, insulation reliability and life of the existing meta-aramid-based insulating paper.

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] In a first aspect, the present application provides a method for preparing meta-aramid nanocomposite paper, comprising the following steps:

[0009] S1. Providing meta-aramid paper, meta-aramid stock solution, and a dissolving solution, wherein the dissolving solution comprises a chloride salt and a first organic solvent;

[0010] S2, mixing the meta-aramid stock solution with inorganic nanoparticles (IN) and a ferroelectric polymer and dissolving the mixture in a second organic solvent to obtain a reinforcement solution;

[0011] S3, placing the meta-aramid paper in the dissolving solution, ultrasonically treating and drying, and coating the reinforcing solution on the surface of the dried meta-aramid paper;

[0012] S4. Performing annealing and polarization treatment on the meta-aramid paper coated with the reinforcing solution to obtain the meta-aramid nanocomposite paper.

[0013] In one or more possible implementations, in step S1, the meta-aramid paper is pretreated:

[0014] The meta-aramid paper is immersed in a sodium dodecylbenzenesulfonate aqueous solution, washed, and then dried.

[0015] In one or more possible implementations, in step S1, the meta-aramid stock solution is defoamed in a vacuum drying oven.

[0016] In one or more possible embodiments, in the sodium dodecylbenzenesulfonate aqueous solution, the mass percentages of the components are: 28-65% dodecylbenzenesulfonic acid, 6-8% sodium carbonate, and the balance water.

[0017] In one or more possible implementations, in the dissolving solution, the mass fraction of the chloride salt is 25% to 35%.

[0018] In one or more possible embodiments, the chloride salt is selected from any one or more of LiCl2, AlCl3, and CaCl2.

[0019] In one or more possible embodiments, in step S2, the inorganic nanoparticles are selected from any one or more of TiO2, Al2O3, SiO2 or mica.

[0020] In one or more possible embodiments, the ferroelectric polymer is selected from any one or more of PVDF, P(VDF-CTEF) or P(VDF-HFP).

[0021] In one or more possible embodiments, the first organic solvent has strong polarity, and the first organic solvent is selected from any one or more of DMSO, DMF, DMAC, and NMP.

[0022] In one or more possible embodiments, the second organic solvent has strong polarity, and the second organic solvent is selected from any one or more of DMSO, DMF, DMAC, and NMP.

[0023] In one or more possible implementations, in step S3, placing the meta-aramid paper in the dissolving solution, ultrasonically treating and drying the solution comprises:

[0024] placing the meta-aramid paper in the dissolving solution and performing ultrasonic treatment, washing with deionized water until neutral after the ultrasonic treatment, and allowing the paper surface to dry naturally;

[0025] Wherein, during the ultrasonic treatment process, the power is 550-650W, the ultrasonic time is 5-10s, the interval is 5-10s, and the duration is 5-10min; and the static treatment time is 2-3h.

[0026] In one or more possible implementations, in step S3, coating the reinforcing solution on the surface of the dried meta-aramid paper includes:

[0027] Lay the dried meta-aramid paper flat on a coating table, and evenly coat the surface of the meta-aramid paper with the reinforcing solution using a coating machine. Then, soak the meta-aramid paper in deionized water, wash it until it is neutral, and dry it. Then, coat the other side of the meta-aramid paper in the same manner.

[0028] Wherein, during the drying process, the ambient temperature is 90-100° C., and the vacuum drying is performed for 10-20 minutes.

[0029] In one or more possible embodiments, the coating of the meta-aramid composite paper can be controlled in thickness by coating rods of different types, and the preferred coating amount is 5-15 g / m 2 .

[0030] In one or more possible implementations, in step S4, during the annealing process, the annealing temperature is 120-160° C., and the annealing time is 12-20 hours.

[0031] In a second aspect, the present application provides a meta-aramid nano-composite paper prepared by the preparation method of the meta-aramid nano-composite paper according to the first aspect, wherein the meta-aramid nano-composite paper includes a first polymer reinforcement layer, a first polymer cross-linked layer, an aramid paper layer, a second polymer cross-linked layer and a second polymer reinforcement layer arranged in sequence from top to bottom.

[0032] The beneficial effects of the present invention are:

[0033] (1) The preparation method of the present invention is simple and easy to implement, has low requirements for production equipment, and is low in cost. The prepared composite paper, after being modified by a simple coating process, has good mechanical strength and insulation properties, and is of great value in the preparation of insulating materials;

[0034] (2) The present invention uses ultrasonic treatment to assist the polar solvent in the swelling modification of the fiber, thereby increasing the contact area and roughness of the paper surface, which is beneficial to physical adsorption; and the aramid stock solution mixed with IN and ferroelectric polymer is filled into the swollen fiber on the surface of MAP to achieve nano-enhancement of MAP;

[0035] (3) The present invention uses meta-aramid stock solution for filling, which is conducive to forming an interface bond between the reinforcing material and the aramid fiber, reducing interface defects, and at the same time is conducive to further densification of the paper surface and enhancing its mechanical strength;

[0036] (4) The present invention infiltrates ferroelectric polymer nanomaterials into the aramid fiber network to form a quaternary "micro-crosslinked" layer of inorganic nano-organic ferroelectric polymer-aramid-aramid fiber, and then uses annealing and polarization treatment to orient the randomly oriented molecular dipoles along the electric field direction, thereby further improving the dielectric properties of the insulating paper.

[0037] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the following is a detailed description of the preferred embodiments of the present invention with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is a flowchart of a method for preparing meta-aramid nanocomposite paper according to an embodiment of the present application;

[0039] Figure 2 Schematic diagram of the preparation method and microscopic interface of the meta-aramid nanocomposite paper according to one embodiment of the present application;

[0040] Figure 3 This is a digital photo of the MAP before and after coating with the enhancement solution shown in an embodiment of the present application;

[0041] Figure 4 This is a scanning electron microscope image of the MAP before and after coating with the enhancement solution shown in an embodiment of the present application. DETAILED DESCRIPTION

[0042] The following describes the embodiments of the present invention through specific examples. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments. The details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the following embodiments and features in the embodiments can be combined with each other unless they conflict.

[0043] It should be noted that the illustrations provided in the following embodiments are merely schematic illustrations of the basic concept of the present invention. Therefore, the illustrations only show components related to the present invention and are not drawn according to the number, shape, and size of components in actual implementation. In actual implementation, the type, quantity, and proportion of each component may be changed arbitrarily, and the component layout may also be more complex.

[0044] While some exemplary embodiments of the present invention have been described for purposes of illustration, it should be understood that the present invention may be implemented in other ways not specifically shown in the drawings.

[0045] Figure 1 The preparation method of the meta-aramid nanocomposite paper shown in an embodiment of the present application is shown. Figure 1 As shown, the preparation method of the meta-aramid nanocomposite paper of this embodiment includes the following steps:

[0046] S1. Providing meta-aramid paper, meta-aramid stock solution, and a dissolving solution, wherein the dissolving solution comprises a chloride salt and a first organic solvent;

[0047] S2, mixing the meta-aramid stock solution with inorganic nanoparticles (IN) and a ferroelectric polymer and dissolving the mixture in a second organic solvent to obtain a reinforcement solution;

[0048] S3, placing the meta-aramid paper in the dissolving solution, ultrasonically treating and drying, and coating the reinforcing solution on the surface of the dried meta-aramid paper;

[0049] S4. Performing annealing and polarization treatment on the meta-aramid paper coated with the reinforcing solution to obtain the meta-aramid nanocomposite paper.

[0050] For details, please combine Figure 2 In step S1, the meta-aramid paper is pretreated:

[0051] The meta-aramid paper is immersed in a sodium dodecylbenzenesulfonate aqueous solution, washed, and then dried.

[0052] The meta-aramid stock solution is defoamed in a vacuum drying oven.

[0053] As an example but not a limitation, in the aqueous solution of sodium dodecylbenzenesulfonate, the mass percentages of the components are: 28-65% dodecylbenzenesulfonic acid, 6-8% sodium carbonate, and the balance water.

[0054] As an example but not a limitation, in the dissolving solution, the mass fraction of the chloride salt is 25% to 35%.

[0055] As an example but not limitation, the chloride salt is selected from any one or more of LiCl2, AlCl3, and CaCl2.

[0056] As an example but not a limitation, in step S2, the inorganic nanoparticles are selected from any one or more of TiO2, Al2O3, SiO2 or mica.

[0057] As an example but not a limitation, the ferroelectric polymer is selected from any one or more of PVDF, P(VDF-CTEF) or P(VDF-HFP).

[0058] As an example but not a limitation, the first organic solvent has strong polarity, and the first organic solvent is selected from any one or more of DMSO, DMF, DMAC, and NMP.

[0059] As an example but not a limitation, the second organic solvent has strong polarity, and the second organic solvent is selected from any one or more of DMSO, DMF, DMAC, and NMP.

[0060] For details, please combine Figure 2 In step S3, the meta-aramid paper is placed in the dissolving solution, ultrasonically treated and dried, comprising:

[0061] placing the meta-aramid paper in the dissolving solution and performing ultrasonic treatment, washing with deionized water until neutral after the ultrasonic treatment, and allowing the paper surface to dry naturally;

[0062] Wherein, during the ultrasonic treatment process, the power is 550-650W, the ultrasonic time is 5-10s, the interval is 5-10s, and the duration is 5-10min; and the static treatment time is 2-3h.

[0063] The step of coating the reinforcing solution on the surface of the dried meta-aramid paper comprises:

[0064] Lay the dried meta-aramid paper flat on a coating table, and evenly coat the surface of the meta-aramid paper with the reinforcing solution using a coating machine. Then, soak the meta-aramid paper in deionized water, wash it until it is neutral, and dry it. Then, coat the other side of the meta-aramid paper in the same manner.

[0065] Wherein, during the drying process, the ambient temperature is 90-100° C., and the vacuum drying is performed for 10-20 minutes.

[0066] It is understood that the coating thickness of the meta-aramid composite paper can be controlled by different types of coating rods, and the preferred coating amount is 5-15g / m 2 .

[0067] As an example but not a limitation, in step S4, during the annealing process, the annealing temperature is 120-160° C. and the annealing time is 12-20 hours.

[0068] The present application will be further described in detail below with reference to specific embodiments.

[0069] It should be noted that the sources of the main reagents involved in the following examples are shown in Table 1:

[0070] Table 1

[0071]

[0072]

[0073] Example 1

[0074] MAP was soaked and washed in a 60°C aqueous solution of sodium dodecylbenzenesulfonate (30% dodecylbenzenesulfonic acid, 6% sodium carbonate, the balance water) for 30 minutes, then vacuum-dried. Simultaneously, the meta-aramid stock solution was defoamed in a 90°C vacuum drying oven for 1 hour. Subsequently, AlCl₃ was dissolved in DMAc solvent to obtain a dissolving solution. In this example, the mass fraction of AlCl₃ was 25%. The defoamed meta-aramid stock solution, Al₂O₃, and PVDF were then dissolved in DMAc solvent to obtain a reinforcing solution. In this example, the mass ratio of meta-aramid stock solution, Al₂O₃, PVDF, and DMAc solvent was 7:1:1:7.

[0075] The cleaned and dried MAP was immersed in the dissolving solution and ultrasonically treated (power 600W, ultrasonic 5s, interval 5s, duration 5min). After the ultrasonic treatment, it was washed with deionized water until neutral and allowed to stand for 2h. After the paper surface was naturally dried, the enhanced solution was evenly coated on the paper surface with a coating amount of 5g / m 2 The paper was then washed in deionized water until neutral and dried in a vacuum oven at 90°C for 10 minutes. The other side of the paper was coated in the same manner to obtain meta-aramid composite paper.

[0076] Finally, the composite paper was annealed in an oven at 120° C. for 20 h to obtain the meta-aramid nanocomposite paper infiltrated with ferroelectric polymer.

[0077] Figure 2 Schematic diagram of the preparation of meta-aramid composite paper and microscopic interface diagram of this embodiment. Figure 2 As shown, in order to enhance the interfacial bonds and physical adsorption between composite materials, this embodiment uses a DMAc-AlCl3 solution to ultrasonically modify the MAP (a) surface fiber swelling (b), and then coats the aramid stock solution, Al2O3, and PVDF reinforcement solution to obtain the meta-aramid composite paper shown in (c), which includes a first polymer reinforcement layer 1, a first polymer cross-linking layer 2, an aramid paper layer 3, a second polymer cross-linking layer 4, and a second polymer reinforcement layer 5 arranged in sequence from top to bottom.

[0078] Figure 3 These are digital photos of the MAP before and after application of the reinforcing solution in this example. Photo 1 shows the surface before application, and Photo 2 shows the surface after application of the correct solution. It can be seen that after application of the aramid solution, Al2O3, and PVDF reinforcement, the surface of the insulating paper becomes darker and smoother.

[0079] Figure 4 The scanning electron microscope images of MAP before and after coating the enhanced solution in this embodiment are shown in FIG. Figure 4 Before coating with the reinforcing solution, the surface fibers of the MAP (Photo 1) are clearly scattered and uneven, with some contact surfaces incomplete and loose microporous structures between adjacent fiber layers. After coating with the reinforcing solution (Photo 2), the aramid composite paper exhibits an overall smooth, uniform, and dense surface, demonstrating the effectiveness of coating modification in improving the mechanical properties of MAP.

[0080] Example 2

[0081] MAP was soaked and washed in a 70°C aqueous solution of sodium dodecylbenzenesulfonate (40% sodium carbonate, 7% water), then vacuum-dried for 35 minutes. The meta-aramid stock solution was then defoamed in a 95°C vacuum drying oven for 1.5 hours. LiCl₂ was then dissolved in DMSO to obtain a solution. In this example, the LiCl₂ mass fraction was 30%. The defoamed meta-aramid stock solution, SiO₂, and P(VDF-HFP) were then dissolved in DMSO to obtain a reinforcement solution. In this example, the mass ratio of meta-aramid stock solution, SiO₂, P(VDF-HFP), and DMSO was 8:1:1.5:8.

[0082] The cleaned and dried MAP was then immersed in the dissolving solution and subjected to ultrasonic treatment (power 600W, ultrasonic 6s, interval 6s, duration 6min). After the ultrasonic treatment, it was washed with deionized water until neutral and allowed to stand for 2.5h. After the paper surface was naturally dried, the enhanced solution was evenly coated on the paper surface with a coating amount of 10g / m 2The paper was then washed in deionized water until neutral and dried in a vacuum oven at 95°C for 15 minutes. The other side of the paper was coated in the same manner to obtain meta-aramid composite paper.

[0083] Finally, the composite paper was annealed in an oven at 140°C for 16 hours to obtain the meta-aramid nanocomposite paper infiltrated with ferroelectric polymer.

[0084] Example 3

[0085] MAP was soaked and washed in an 80°C aqueous solution of sodium dodecylbenzenesulfonate (50% dodecylbenzenesulfonic acid, 8% sodium carbonate, the balance water) for 40 minutes, then vacuum-dried. The meta-aramid stock solution was defoamed in a 100°C vacuum drying oven for 2 hours. CaCl₂ was then dissolved in DMF to obtain a solution. In this example, the CaCl₂ mass fraction was 35%. The defoamed meta-aramid stock solution, TiO₂, and P(VDF-CTEF) were then dissolved in DMF to obtain a reinforcement solution. In this example, the mass ratio of the meta-aramid stock solution, TiO₂, P(VDF-CTEF), and DMF was 9:1:2:9.

[0086] The cleaned and dried MAP was immersed in the dissolving solution and ultrasonically treated (power 600W, ultrasonic 6s, interval 6s, duration 6min). After the ultrasonic treatment, it was washed with deionized water until neutrality and allowed to stand for 3h. After the paper surface was naturally dried, the enhanced solution was evenly coated on the paper surface with a coating amount of 15g / m 2 The paper was then washed in deionized water until neutral and dried in a vacuum oven at 100°C for 20 minutes. The other side of the paper was coated in the same manner to obtain meta-aramid composite paper.

[0087] Finally, the composite paper was annealed in an oven at 160° C. for 12 h to obtain the meta-aramid nanocomposite paper infiltrated with ferroelectric polymer.

[0088] Comparative Example 1

[0089] MAP was soaked and washed in a 75°C aqueous solution of sodium dodecylbenzenesulfonate (60% sodium carbonate, 8% water) for 35 minutes, then vacuum-dried. The meta-aramid stock solution was defoamed in a 90°C vacuum drying oven for 1.5 hours. CaCl₂ was dissolved in NMP to obtain a solution containing 30% CaCl₂. The defoamed meta-aramid stock solution was dissolved in NMP to obtain a reinforcement solution, with a mass ratio of 1:1 between the meta-aramid stock solution and the NMP.

[0090] The cleaned and dried MAP was immersed in the dissolving solution and ultrasonically treated (power 600W, ultrasonic 10s, interval 10s, duration 10min). After the ultrasonic treatment, it was washed with deionized water until neutral and allowed to stand for 2.5h. After the paper surface was naturally dried, the enhanced solution was evenly coated on the paper surface with a coating amount of 10g / m 2 The paper was then washed in deionized water until neutral and dried in a vacuum oven at 90°C for 20 minutes. The other side of the paper was coated in the same manner to obtain meta-aramid composite paper.

[0091] Comparative Example 2

[0092] MAP was immersed and washed in an aqueous solution of sodium dodecylbenzenesulfonate (dodecylbenzenesulfonic acid: 30%, sodium carbonate: 6%, and the balance water) at 70° C. for 30 minutes, and then vacuum dried.

[0093] Test results

[0094] The present application tests the relevant mechanical and electrical properties of the meta-aramid papers of Examples 1-3 and Comparative Examples 1 and 2.

[0095] (1) Mechanical properties

[0096] The mechanical properties of the meta-aramid paper of each embodiment and comparative example are shown in Table 2 below:

[0097] Table 2

[0098]

[0099] According to the data in Table 2, the mechanical properties of the meta-aramid composite paper obtained in the embodiment of the present invention are greatly improved compared with the base paper. It is expected that the composite of nanoparticles and organic ferroelectric polymers can improve the insulation properties while still maintaining good mechanical strength.

[0100] Therefore, the mechanical properties of the high-strength corona-resistant meta-aramid composite paper of the present invention are better than those of Comparative Example 2, that is, better than conventional meta-aramid paper.

[0101] (2) Electrical performance

[0102] The mechanical properties of the meta-aramid paper of each embodiment and comparative example are shown in Table 3 below:

[0103] Table 3

[0104]

[0105]

[0106] The data in Table 3 indicate that the electrical properties of the meta-aramid composite paper obtained in the embodiments of the present invention are significantly improved compared to the base paper. It is expected that the final annealing treatment can polarize the composite paper, aligning the ferroelectric polymer molecular dipoles along the electric field direction, further improving the dielectric properties and corona resistance.

[0107] Therefore, the electrical properties of the meta-aramid composite paper obtained in the embodiment of the present invention are significantly better than those in comparative examples 1 and 2.

[0108] The meta-aramid nanocomposite paper prepared according to Examples 1-3 includes a first polymer reinforcement layer, a first polymer cross-linking layer, an aramid paper layer, a second polymer cross-linking layer, and a second polymer reinforcement layer, which are sequentially arranged from top to bottom.

[0109] In the above embodiment, the first polymer reinforcement layer and the second polymer reinforcement layer are identical, and the first polymer cross-linked layer and the second polymer cross-linked layer are identical. Of course, in other embodiments not shown, different first polymer reinforcement layers and second polymer reinforcement layers, as well as different first polymer cross-linked layers and second polymer cross-linked layers, can be provided as needed. Specifically, different reinforcement solutions can be applied to different surfaces of the aramid paper.

[0110] In the above embodiments, the first organic solvent is used to prepare the dissolving solution, and the second organic solvent is used to prepare the enhancing solution. Of course, in other embodiments not shown, the first and second organic solvents can be selected from one or more of DMSO, DMF, DMAC, and NMP, depending on actual needs. It is understood that other highly polar solvents not shown can also be selected.

[0111] This application uses MAP as a substrate, dissolving chloride salt in a highly polar organic solvent as a dissolving solution, and dissolving meta-aramid stock solution and IN in a highly polar organic solvent as a reinforcing solution. First, the fibers on the surface of the MAP are swollen and modified by ultrasound-assisted polar solvents, and then the reinforcing solution is applied to fully infiltrate and fill the pores of the MAP, forming a quaternary "micro-crosslinked" layer of inorganic nano-ferroelectric polymer-aramid-aramid fiber on the surface of the MAP layer. Subsequently, after washing and drying, a dense inorganic nano-ferroelectric polymer-aramid layer is formed on the outermost layer of the MAP, further improving the mechanical strength. Finally, the composite paper is polarized by annealing treatment, so that the ferroelectric polymer molecular dipoles are aligned along the direction of the electric field, further improving the dielectric properties and corona resistance.

[0112] The meta-aramid composite paper prepared in this application exhibits high mechanical strength and corona resistance. This is achieved by nano-reinforcement of the MAP surface layer using an aramid stock solution containing a mixture of IN and an organic ferroelectric polymer, filling the swollen fibers with an aramid solution. Ultrasonic-assisted swelling of the fibers with a polar solvent increases the contact area and roughness of the paper surface, facilitating physical adsorption. The polarization modification during annealing aligns the randomly oriented molecular dipoles along the electric field, thereby enhancing dielectric properties.

[0113] Furthermore, the use of aramid stock solution for filling facilitates interfacial bonding between IN and aramid fibers, reducing interfacial defects and further densifying the paper surface, enhancing its mechanical strength. The combination of IN and an organic ferroelectric polymer improves corona resistance while further homogenizing the electric field on the composite paper's surface, resulting in excellent mechanical and corona resistance properties.

[0114] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0115] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A method for preparing meta-aramid nanocomposite paper, characterized in that: The following steps are involved: S1. Providing meta-aramid paper, a meta-aramid stock solution, and a dissolving solution, wherein the meta-aramid paper has been pretreated by immersing in an aqueous solution of sodium dodecylbenzenesulfonate, washing, and then drying; the meta-aramid stock solution has been defoamed in a vacuum drying oven; the dissolving solution comprises a chloride salt and a first organic solvent, wherein the chloride salt is selected from any one or more of LiCl2, AlCl3, and CaCl2, and the first organic solvent has a strong polarity; S2, mixing the meta-aramid stock solution with inorganic nanoparticles and ferroelectric polymers and dissolving them in a second organic solvent to obtain an enhanced solution; the inorganic nanoparticles are selected from any one or more of TiO2, Al2O3, SiO2 or mica; the ferroelectric polymer is selected from any one or more of polyvinylidene fluoride, polyvinylidene fluoride-trifluoroethylene copolymer or vinylidene fluoride-hexafluoropropylene copolymer; the second organic solvent has a strong polarity; S3, placing the meta-aramid paper in the dissolving solution, performing ultrasonic treatment, washing with deionized water until neutral after the ultrasonic treatment, standing the paper until the surface is naturally dry, and coating the reinforcing solution on the surface of the dried meta-aramid paper; S4. Performing annealing and polarization treatment on the meta-aramid paper coated with the reinforcing solution to obtain the meta-aramid nanocomposite paper.

2. The method for preparing meta-aramid nanocomposite paper according to claim 1, wherein: In the sodium dodecylbenzenesulfonate aqueous solution, the mass percentages of the components are: 28-65% dodecylbenzenesulfonic acid, 6-8% sodium carbonate, and the balance water; and / or, In the dissolving solution, the mass fraction of the chloride salt is 25% to 35%.

3. The method for preparing meta-aramid nanocomposite paper according to claim 1, wherein: The first organic solvent is selected from any one or more of dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone; and / or, The second organic solvent is selected from any one or more of dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone.

4. The method for preparing meta-aramid nanocomposite paper according to claim 1, wherein: In step S3, during the ultrasonic treatment, the power is 550-650 W, the ultrasonic time is 5-10 s, the interval is 5-10 s, and the duration is 5-10 min; and the static treatment time is 2-3 h.

5. The method for preparing meta-aramid nanocomposite paper according to claim 1 or 4, wherein: In step S3, coating the reinforcing solution on the surface of the dried meta-aramid paper comprises: Lay the dried meta-aramid paper flat on a coating table, and evenly coat the surface of the meta-aramid paper with the reinforcing solution using a coating machine. Then, soak the meta-aramid paper in deionized water, wash it until it is neutral, and dry it. Then, coat the other side of the meta-aramid paper in the same manner. Wherein, during the drying process, the ambient temperature is 90-100° C., and the vacuum drying is performed for 10-20 minutes.

6. The method for preparing meta-aramid nanocomposite paper according to claim 1, wherein: Step S4: During the annealing process, the annealing temperature is 120-160° C. and the annealing time is 12-20 h.

7. The meta-aramid nanocomposite paper prepared by the method for preparing meta-aramid nanocomposite paper according to any one of claims 1 to 6, characterized in that: The meta-aramid nanocomposite paper comprises a first polymer reinforcement layer, a first polymer cross-linking layer, an aramid paper layer, a second polymer cross-linking layer and a second polymer reinforcement layer which are sequentially arranged from top to bottom.

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