High-strength electromagnetic shielding nanofiber composite membrane with double network structure and preparation method thereof

Abstract

The application provides a high-strength electromagnetic shielding nanofiber composite film with a double-network structure and a preparation method thereof. A nanofiber suspension is prepared first, then the nanofiber suspension is sequentially mixed with carbon nanotubes and silver-plated nylon to obtain a multi-component mixed suspension, then the multi-component mixed suspension is filtered through a vacuum-assisted filtration method to obtain a nanofiber composite film, and finally the nanofiber composite film is immersed in a crosslinking agent and crosslinked under ultraviolet light to obtain the high-strength electromagnetic shielding nanofiber composite film with the double-network structure. The nanofiber composite film with the double-network structure is prepared by taking nanofibers as a base material, selecting wave-absorbing media with different properties, and cooperating with the vacuum-assisted filtration method. The composite film material overcomes the defects of traditional conductive polymer composite materials that are difficult to have shielding performance and mechanical performance, has excellent electromagnetic shielding performance in a wide frequency band range, has sufficient mechanical performance and good processing performance, and widens the application field of electromagnetic shielding materials.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electromagnetic shielding materials, and particularly relates to a high-strength electromagnetic shielding nanofiber composite film with a double-network structure and a preparation method thereof. BACKGROUND

[0002] With the advent of the Internet era, 5G communication technology and intelligent electronic products are the needs of the new era, but also bring new problems such as electromagnetic radiation pollution. Electromagnetic pollution can pose a serious threat to electronic equipment and human health. For example, the electromagnetic waves generated by televisions / radios, mobile phones exceeding the normal limit will interact with electronic equipment related to nuclear power plants, transformers, aerospace and aircraft systems, and medical equipment, and will also affect human health, causing headaches, cancer, fatigue and other problems.

[0003] Electromagnetic shielding refers to using specific materials or structures as shielding bodies to stop electromagnetic radiation or block the propagation of electromagnetic waves. According to the transmission line theory of electromagnetic shielding mechanism, the attenuation of electromagnetic shielding body to electromagnetic wave is mainly based on the reflection of electromagnetic wave and the absorption of electromagnetic wave. When electromagnetic wave reaches the surface of the shielding body, due to the discontinuity of impedance at the air-metal interface, the reflection of the incident wave occurs, and the energy that is not reflected by the surface enters the shielding body and is attenuated in the body, which is called absorption. The remaining energy that has not been attenuated in the shielding body will be reflected again when it reaches the other surface of the material, and will return to the shielding body. This reflection may occur multiple times at the interface of the two metals.

[0004] Although metal-based materials are widely used in industry due to their excellent electrical conductivity, EMI shielding and thermal management performance, their high density, low flexibility, low mechanical performance and poor chemical corrosion resistance limit their application in many cases. At present, conductive polymer composites (CPCs) composed of a polymer matrix and conductive fillers (such as graphene, multi-walled carbon nanotubes (MWCNTs), metal nanoparticles (NPs), and nanowires (NWs), and their hybrids) are widely studied and applied in light electromagnetic interference shielding and thermal management materials. However, due to the high percolation threshold of CPCs, high filler content and large thickness are usually required to obtain ideal electrical conductivity and EMI shielding performance, but this will lead to a decrease in the flexibility, mechanical properties (especially strength and toughness) and processability of the material, reducing its practicality.

[0005] Therefore, it is necessary to design an improved high-strength electromagnetic shielding nanofiber composite film with a double-network structure and a preparation method thereof to solve the above problems. SUMMARY

[0006] The application aims to provide a high-strength electromagnetic shielding nanofiber composite film with a double-network structure and a preparation method thereof.

[0007] To achieve the above-mentioned application purposes, the application provides a preparation method of a high-strength electromagnetic shielding nanofiber composite film with a double-network structure, which comprises the following steps:

[0008] S1, preparing a nanofiber suspension with a nanofiber content of 0.5wt%-1.5wt%;

[0009] S2, mixing the nanofiber suspension of step S1 with carbon nanotubes and silver-plated nylon to obtain a multi-component mixed suspension;

[0010] S3, placing the multi-component mixed suspension obtained in step S2 in a vacuum-assisted filtration device to obtain a nanofiber composite film through vacuum-assisted filtration;

[0011] S4, immersing the nanofiber composite film obtained in step S3 in a crosslinking agent, crosslinking under ultraviolet light, and naturally air-drying to obtain a high-strength electromagnetic shielding nanofiber composite film with a double-network structure.

[0012] As a further improvement of the application, in the multi-component mixed suspension of step S2, the mass percentage content of the carbon nanotubes is 2wt%-4wt%, and the mass percentage content of the silver-plated nylon is 4wt%-6wt%.

[0013] As a further improvement of the application, in step S2, the silver-plated nylon is silver-plated nylon fiber with a length of 50-150μm and a fiber diameter of 20-80μm.

[0014] As a further improvement of the application, in step S4, the mass percentage concentration of the crosslinking agent is 3%-5%, the crosslinking time under ultraviolet light is 20-40min, and the ultraviolet light intensity is 50μW / cm 2 .

[0015] As a further improvement of the application, in step S1, the types of nanofibers in the nanofiber suspension include one or more of PVA-co-PE nanofiber, aramid fiber, cellulose nanofiber and carbon nanofiber.

[0016] As a further improvement of the application, in step S1, the nanofiber suspension is prepared by dispersing isopropyl alcohol, deionized water and nanofibers in a certain proportion under a high-speed shearing machine at a volume ratio of 1:1.

[0017] As a further improvement of the present application, the cross-linking agent is prepared by diluting trimethylolpropane trimethacrylate with ethanol to a certain concentration.

[0018] As a further improvement of the present application, in step S2, the multi-component mixed suspension further contains glutaraldehyde cross-linking agent, the mass ratio of the glutaraldehyde cross-linking agent in the multi-component mixed suspension is 0.5wt%-1.5wt%; the glutaraldehyde cross-linking agent is prepared by glutaraldehyde and hydrochloric acid with a volume ratio of 1:(0.08-0.12).

[0019] The application also provides a high-strength electromagnetic shielding nanofiber composite film with a double-network structure, which is prepared by the preparation method of the high-strength electromagnetic shielding nanofiber composite film with a double-network structure according to any one of the above.

[0020] As a further improvement of the present application, the nanofiber composite film has a double-network structure of a large network wrapping a small network, and the electromagnetic shielding performance in the X wave band is 40-45 dB.

[0021] The application has the following beneficial effects:

[0022] 1. The preparation method of the high-strength electromagnetic shielding nanofiber composite film with a double-network structure, which mixes nanofiber suspension, carbon nanotubes and silver-plated nylon as raw materials to form a multi-component mixed suspension, then obtains a nanofiber composite film through vacuum-assisted filtration, finally immerses the nanofiber composite film in a cross-linking agent, places it under ultraviolet light for cross-linking, and then naturally air-dries to obtain a high-strength electromagnetic shielding nanofiber composite film with a double-network structure. The application selects nanofiber as a base material, selects wave-absorbing media with different properties, and uses a vacuum-assisted filtration method to obtain a nanofiber composite film with a double-network structure. The composite film material has excellent electromagnetic shielding performance in a wide frequency band range, has high electromagnetic shielding performance and strong mechanical properties, and overcomes the problems of high permeability domain value, low conductivity and EMI shielding performance of traditional conductive polymer composite materials.

[0023] 2、The application selects nanofiber, carbon nanotube and silver-plated nylon fiber as raw materials, and constructs nanofiber composite film with a new structure by using a vacuum-assisted filtration method, wherein the nanofiber is crosslinked to form a large network structure, the carbon nanotube is crosslinked to form a small network structure in the large network structure of the nanofiber, and the silver-plated nylon fiber penetrates through the whole composite film structure and plays a role of bridge and support. The double-network structure of the large network wrapping the small network improves the heterogeneous contact between media and media, enhances the multi-layer reflection mechanism of the nanofiber composite film to electromagnetic waves, improves the impedance matching and interface polarization, enhances the loss of electromagnetic waves, and thus the electromagnetic shielding performance is obviously improved. In addition, the addition of the carbon nanotube not only increases the electromagnetic shielding performance, but also makes the nanofiber film have good flexibility; the introduction of the silver-plated nylon not only makes the nanofiber film have good toughness, but also improves the conductivity of the composite film material, and the network structure formed by the two synergistically enhances the mechanical properties of the composite film.

[0024] 3、The vacuum-assisted filtration method of the application plays a key role in forming the double-network structure nanofiber composite film, effectively removes air, moisture and other interference factors affecting uniform film formation, ensures the stability of the uniformly dispersed suspension, avoids the clustering or aggregation of nanofiber during the preparation of the composite film, and successfully prepares the multi-network and uniformly structured nanofiber composite film. In addition, by adding a crosslinking agent, the nanofiber and the carbon nanotube are connected to each other to form a double-network structure, which further enhances the excellent mechanical properties of the nanofiber composite film. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 It is a flowchart of the preparation method of the double-network structure high-strength electromagnetic shielding nanofiber composite film of Example 1.

[0026] Figure 2 It is a microelectronic microscope graph of a certain area of the double-network structure high-strength electromagnetic shielding nanofiber composite film of Example 1.

[0027] Figure 3 It is a microelectronic microscope graph of another area of the double-network structure high-strength electromagnetic shielding nanofiber composite film of Example 1.

[0028] Figure 4 It is a graph of electromagnetic shielding performance test results of the fiber film of Example 1 and Comparative Examples 1-2.

[0029] Figure 5 It is a graph of mechanical property test results of the fiber film of Example 1 and Comparative Examples 1-2. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical scheme and advantages of the application clearer, the application will be described in detail below with reference to the drawings and specific examples.

[0031] It should be noted that, in order to avoid obscuring the present application with unnecessary details, only the structures and / or processing steps closely related to the solution of the present application are shown in the drawings, while other details not closely related to the present application are omitted.

[0032] It should be further noted that the terms "comprising", "containing" or any other variant thereof are intended to cover a non-exclusive inclusion, such that a process, method, article or apparatus that comprises a list of elements is not necessarily limited to those elements, but can include other elements not expressly listed or inherent to such process, method, article or apparatus.

[0033] A preparation method of a high-strength electromagnetic shielding nanofiber composite film with a double-network structure, comprising the following steps:

[0034] S1, preparing a nanofiber suspension with a nanofiber content of 0.5wt%-1.5wt%;

[0035] S2, mixing the nanofiber suspension of step S1 with carbon nanotubes and silver-plated nylon to obtain a multi-component mixed suspension; in the multi-component mixed suspension, the mass percentage content of carbon nanotubes is 2wt%-4wt%, and the mass percentage content of silver-plated nylon is 4wt%-6wt%; in order to be suitable for vacuum-assisted filtration method and form a nanofiber composite film with a double-network structure, the contents of each raw material need to be strictly controlled;

[0036] S3, placing the multi-component mixed suspension obtained in step S2 in a vacuum-assisted filtration device to obtain a nanofiber composite film by vacuum-assisted filtration;

[0037] S4, immersing the nanofiber composite film obtained in step S3 in a crosslinking agent, and then crosslinking under ultraviolet light, and then naturally air-drying to obtain a high-strength electromagnetic shielding nanofiber composite film with a double-network structure.

[0038] Particularly, the preparation method uses nanofibers as a base material, selects different wave-absorbing media, and uses a vacuum-assisted filtration method to obtain a nanofiber composite film with a double-network structure. The composite film material has excellent electromagnetic shielding performance in a wide frequency band range, has high electromagnetic shielding performance and strong mechanical performance, and overcomes the problems of traditional conductive polymer composite materials, such as high permeability, low conductivity, and EMI shielding performance. The vacuum-assisted filtration method plays a key role in forming the double-network structure nanofiber composite film. It effectively removes air, moisture, and other interference factors that affect uniform film formation, ensures the stability of the uniformly dispersed suspension, and keeps the suspension in a uniformly dispersed state during the preparation of the film. This avoids the clustering or aggregation of nanofibers during the preparation of the composite film, and successfully obtains a multi-network and uniformly structured nanofiber composite film.

[0039] Specifically, in step S2, the silver-plated nylon is silver-plated nylon fiber with a length of 50-150 μm and a fiber diameter of 20-80 μm, and the carbon nanotube is a multi-walled carbon nanotube. By limiting the length and diameter of the silver-plated nylon fiber, it can penetrate the entire composite film, better playing the role of a bridge and a support. In step S1, the types of nanofibers in the nanofiber suspension include one or more of PVA-co-PE (polyvinyl alcohol-ethylene copolymer) nanofiber, aramid fiber, cellulose nanofiber, and carbon nanofiber; preferably PVA-co-PE nanofiber, which contains multiple polar groups, has hydrophilicity and strong interaction with other polar molecules, and is beneficial to the compounding of nanofibers and carbon nanotubes.

[0040] The present application selects nanofibers, carbon nanotubes, and silver-plated nylon fibers as raw materials, and uses a vacuum-assisted filtration method to construct a nanofiber composite film with a new structure. The nanofibers form a large network structure, the carbon nanotubes form a small network structure in the large network structure of the nanofibers, and the silver-plated nylon fibers penetrate the entire composite film structure, acting as a bridge and a support. The double-network structure of the large network wrapping the small network improves the heterogeneous contact between the media and the media, enhances the multi-layer reflection mechanism of the nanofiber composite film to electromagnetic waves, improves the impedance matching and interface polarization, and enhances the loss of electromagnetic waves, thereby significantly improving the electromagnetic shielding performance. In addition, the addition of carbon nanotubes not only increases the electromagnetic shielding performance, but also makes the nanofiber film have good flexibility. The introduction of silver-plated nylon not only makes the nanofiber film have good toughness, but also improves the conductivity of the composite film material. The network structure formed by the two synergistically enhances the mechanical performance of the composite film.

[0041] More specifically, in step S1, the nanofiber suspension is prepared by dispersing isopropyl alcohol, deionized water, and nanofibers in a certain proportion in a high-speed shearing machine at a volume ratio of 1:1.

[0042] In step S4, the mass percentage concentration of the crosslinking agent is 3% to 5%, the time for crosslinking under ultraviolet light is 20 to 40 min, and the ultraviolet light intensity is 50 μW / cm 2 The crosslinking agent is prepared by diluting trimethylolpropane trimethacrylate (TMPTMA) with ethanol to a certain concentration. By adding the crosslinking agent, the nanofibers and carbon nanotubes are connected to each other to form a double network structure, and several media are firmly "bonded" together, further enhancing the excellent mechanical properties of the nanofiber composite film.

[0043] In step S2, the multi-component mixed suspension also contains glutaraldehyde crosslinking agent, and the mass percentage of the glutaraldehyde crosslinking agent in the multi-component mixed suspension is 0.5wt% to 1.5wt%; the glutaraldehyde crosslinking agent is prepared by glutaraldehyde and hydrochloric acid in a volume ratio of 1:(0.08 to 0.12). The addition of the glutaraldehyde crosslinking agent further improves the crosslinking and bonding strength between the nanofibers, carbon nanotubes and silver-plated nylon fibers.

[0044] A double network structure high-strength electromagnetic shielding nanofiber composite film is prepared by the preparation method of the double network structure high-strength electromagnetic shielding nanofiber composite film. The nanofiber composite film has a double network structure of a large network wrapping a small network, an electromagnetic shielding performance of 40 to 45 dB in the X band, a strain of more than 15 Mpa, and good mechanical properties.

[0045] Embodiment 1

[0046] Please refer to Figure 1 The embodiment provides a preparation method of a double network structure high-strength electromagnetic shielding nanofiber composite film, which comprises the following steps:

[0047] S1, isopropanol, deionized water (volume ratio 1:1) and PVA-co-PE nanofiber are dispersed and mixed in a high-speed shearing machine at a certain proportion to prepare a PVA-co-PE nanofiber suspension with a fiber content of 1wt%;

[0048] S2, the PVA-co-PE nanofiber suspension of step S1 is mixed with carbon nanotubes and silver-plated nylon fibers (average length 100 μm, average fiber diameter 20 μm) in turn, and a multi-component mixed suspension is obtained after ultrasonic stirring; in the multi-component mixed suspension, the mass percentage of the carbon nanotubes is 3wt%, and the mass percentage of the silver-plated nylon is 5wt%;

[0049] S3, the multi-component mixed suspension obtained in step S2 is placed in a vacuum-assisted filtration device, the vacuum degree is-0.1 MPa, and a nanofiber composite film is obtained by vacuum-assisted filtration.

[0050] S4. Immerse the nanofiber composite membrane obtained in step S3 in a TMPTMA crosslinking agent (mass percentage concentration is 5%), and then place it under ultraviolet light for crosslinking. The ultraviolet intensity is 50 μW / cm 2 , time is 30min, and after natural air drying, a high-strength electromagnetic shielding nanofiber composite membrane with a double network structure (PVA-co-PE / CNTs / Ag@nylon) is obtained.

[0051] See also Figures 2-3 The figure below shows a microscopic electron microscope image of the high-strength electromagnetic shielding nanofiber composite membrane with a dual-network structure prepared in Example 1. As can be seen from the figure, the composite membrane of this example has a multi-network structure, in which silver-plated nylon fibers serve as bridges and supports throughout the composite membrane, and PVA-co-PE nanofibers and carbon nanotubes are cross-linked to form a large network encapsulating a smaller network. This structure enhances the nanofiber composite membrane's multi-layer reflection mechanism for electromagnetic waves, improves impedance matching and interfacial polarization, and enhances electromagnetic wave loss, significantly improving electromagnetic shielding performance and enhancing the material's mechanical properties.

[0052] Comparative Example 1

[0053] Comparative Example 1 provides a method for preparing a nanofiber membrane. Compared with Example 1, the difference is that only the PVA-co-PE nanofiber suspension in step S1 is used to obtain a nanofiber composite membrane (PVA-co-PE) by vacuum-assisted filtration.

[0054] Comparative Example 2 provides a method for preparing an electromagnetic shielding nanofiber composite membrane. Compared with Example 1, the difference is that no silver-plated nylon fiber is added to the multi-component mixed suspension in step S2 to obtain a PVA-co-PE / CNTs fiber membrane. The rest is roughly the same as Example 1 and will not be repeated here.

[0055] See also Figures 4-5 The graph shows the electromagnetic shielding performance and mechanical performance test results of the fiber membranes of Example 1 and Comparative Examples 1-2. Figure 4 It can be seen that the nanofiber composite membrane (PVA-co-PE / MW-CNTs / Ag@nylon) prepared in Example 1 has significantly improved electromagnetic shielding performance in the X-band compared to the nanofiber composite membrane (PVA-co-PE / MW-CNTs) without silver-coated nylon. The EMI SET in the X-band is increased from 23dB to 42dB, which is nearly 2 times higher than before. Figure 5 It can be seen that the strain of the nanofiber composite membrane prepared in Example 1 is increased from 10 MPa to 15 MPa, which is increased by nearly 1.5 times, and the stress thereof is increased by nearly 40%, showing good mechanical properties.

[0056] Example 2

[0057] The present example provides a preparation method of a high-strength electromagnetic shielding nanofiber composite film with a double-network structure. Compared with Example 1, the difference lies in that the multi-component mixed suspension in step S2 also contains 0.5wt% glutaraldehyde crosslinking agent, which is composed of glutaraldehyde and hydrochloric acid in a volume ratio of 1:0.1, and the rest is basically the same as Example 1, which will not be repeated here.

[0058] Comparative Example 3

[0059] Comparative Example 3 provides a preparation method of an electromagnetic shielding nanofiber composite film. Compared with Example 1, the difference lies in that no carbon nanotubes are added to the multi-component mixed suspension in step S2, obtaining a PVA-co-PE / Ag@nylon fiber film, and the rest is basically the same as Example 1, which will not be repeated here.

[0060] Comparative Example 4

[0061] Comparative Example 4 provides a preparation method of an electromagnetic shielding nanofiber composite film. Compared with Example 1, the difference lies in that reduced graphene oxide is used instead of carbon nanotubes in the multi-component mixed suspension in step S2, obtaining a PVA-co-PE / Ag@nylon fiber film, and the rest is basically the same as Example 1, which will not be repeated here.

[0062] Comparative Example 5

[0063] Comparative Example 5 provides a preparation method of an electromagnetic shielding nanofiber composite film. Compared with Example 1, the difference lies in that step S4 is not performed, and the rest is basically the same as Example 1, which will not be repeated here.

[0064] Comparative Example 6

[0065] Comparative Example 6 provides a preparation method of an electromagnetic shielding nanofiber composite film. Compared with Example 1, the difference lies in that a centrifugal spin coating method is used to prepare the nanofiber composite film in step S3, and the rest is basically the same as Example 1, which will not be repeated here.

[0066] Comparative Example 7

[0067] Comparative Example 7 provides a preparation method of an electromagnetic shielding nanofiber composite film. Compared with Example 1, the difference lies in that step S1 is not performed, and the multi-component mixed suspension in step S2 does not contain PVA-co-PE nanofiber, and the rest is basically the same as Example 1, which will not be repeated here.

[0068] The nanofiber composite film prepared in Example 2 and Comparative Examples 3-7 was detected for electromagnetic shielding performance and mechanical performance, and the results are shown in the following table.

[0069] Table 1 Performance detection results of nanofiber composite film of Example 2 and Comparative Examples 3-7

[0070]

[0071]

[0072] As shown in Table 1, in Example 2, the crosslinking agent is added in excess, and the mechanical performance is improved, and the electromagnetic shielding performance changes little. In Comparative Example 3, no carbon nanotubes are added, and the composite film lacks a dielectric loss medium, resulting in a decrease in electromagnetic shielding performance, and the composite film cannot be constructed to have a double network structure, and the mechanical performance is lower than that of the example. In Comparative Example 4, reduced graphene oxide is used instead of carbon nanotubes, and the effect on electromagnetic shielding and mechanical performance is not good, because the sheet structure of graphene cannot form a double network structure with nanofibers as carbon nanotubes do, and the degree of reflection of electromagnetic waves and the degree of binding between materials are reduced. In Comparative Example 5, no crosslinking agent is added for crosslinking, resulting in weak mechanical performance, and no crosslinking agent is added, resulting in that a large number of hydrogen bonds are not formed between the nanofiber and carbon nanotube networks, reducing the heterogeneous contact between the media and the media, thereby reducing the reflection of electromagnetic waves, resulting in a decrease in the electromagnetic shielding capacity of the composite film. In Comparative Example 6, the composite film is prepared by centrifugal spin coating, and the mechanical performance of the film is not good due to insufficient viscosity of the nanofibers, and the nanofiber composite film prepared by centrifugal spin coating has poor film forming effect and uneven medium distribution due to insufficient viscosity of the nanofiber suspension, resulting in a decrease in electromagnetic shielding capacity. In Comparative Example 7, the composite film does not contain nanofibers, and the composite film has no fiber substrate support, resulting in poor mechanical performance, and the composite film cannot form a double network structure with carbon nanotubes, resulting in a decrease in the number of electromagnetic wave reflections, and a significant decrease in electromagnetic shielding performance.

[0073] In summary, the present application provides a double network structure high-strength electromagnetic shielding nanofiber composite film and a preparation method thereof. A multi-component mixed suspension is formed by mixing a nanofiber suspension, carbon nanotubes and silver-plated nylon as raw materials, and then a nanofiber composite film is obtained by vacuum-assisted filtration. Finally, the nanofiber composite film is immersed in a crosslinking agent and crosslinked under ultraviolet light, and then naturally air-dried to obtain a double network structure high-strength electromagnetic shielding nanofiber composite film. The present application uses nanofibers as substrate raw materials, selects wave-absorbing media with different properties, and uses a vacuum-assisted filtration method to obtain a nanofiber composite film with a double network structure. The composite film material has excellent electromagnetic shielding performance in a wide frequency band range, and has high electromagnetic shielding performance and strong mechanical performance, overcoming the problems of high permeability domain value, low electrical conductivity and EMI shielding performance of traditional conductive polymer composite materials.

[0074] The above examples are only used to illustrate the technical solutions of the present application but not to limit the present application. Although the present application is described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or equivalently replaced, without departing from the spirit and scope of the present application.

Claims

1. A method for preparing a high-strength electromagnetic shielding nanofiber composite film of a dual-network structure, characterized by, The method comprises the following steps: S1, preparing a nanofiber suspension with a nanofiber content of 0.5 wt%-1.5 wt%; S2, mixing the nanofiber suspension of step S1 with carbon nanotubes and silver-plated nylon to obtain a multi-component mixed suspension; In the multi-component mixed suspension, the mass percentage of the carbon nanotubes is 2 wt%-4 wt%, and the mass percentage of the silver-plated nylon is 4 wt%-6 wt%; the silver-plated nylon is silver-plated nylon fiber with a length of 50-150 μm and a fiber diameter of 20-80 μm; S3, placing the multi-component mixed suspension obtained in step S2 in a vacuum-assisted filtration device to obtain a nanofiber composite membrane by vacuum-assisted filtration; S4, immersing the nanofiber composite membrane obtained in step S3 in a crosslinking agent, and then crosslinking under ultraviolet light to obtain a high-strength electromagnetic shielding nanofiber composite membrane with a double-network structure after natural air drying; the crosslinking agent is prepared by diluting trimethylolpropane trimethacrylate with ethanol to a certain concentration.

2. The method of claim 1, wherein the method is characterized by: In step S4, the mass percentage concentration of the crosslinking agent is 3% to 5%, the time for crosslinking under ultraviolet light is 20 to 40 min, and the ultraviolet light intensity is 50 μW / cm 2 .

3. The method of claim 1, wherein the method is characterized by: In step S1, the types of nanofibers in the nanofiber suspension include one or more of PVA-co-PE nanofibers, aramid fibers, cellulose nanofibers, and carbon nanofibers.

4. The method for preparing a high-strength electromagnetic shielding nanofiber composite membrane with a double network structure according to claim 1, characterized in that: In step S1, the nanofiber suspension is prepared by dispersing the nanofibers in isopropyl alcohol, deionized water, and a certain proportion of nanofibers in a high-speed shearing machine at a volume ratio of 1:

1.

5. The method for preparing a high-strength electromagnetic shielding nanofiber composite membrane with a double network structure according to claim 1, characterized in that: In step S2, the multi-component mixed suspension further contains glutaraldehyde crosslinking agent, and the mass percentage of the glutaraldehyde crosslinking agent in the multi-component mixed suspension is 0.5 wt%-1.5 wt%; the glutaraldehyde crosslinking agent is prepared by mixing glutaraldehyde and hydrochloric acid at a volume ratio of 1:(0.08-0.12).

6. A high-strength electromagnetic shielding nanofiber composite film of a dual-network structure, characterized by, The high-strength electromagnetic shielding nanofiber composite membrane with a double-network structure is prepared by the method of any one of claims 1-5.

7. The dual-network structured high-strength electromagnetic interference shielding nanofibrous composite film according to claim 6, wherein The nanofiber composite membrane has a double-network structure with a large network wrapping a small network, and an electromagnetic shielding performance of 40-45 dB in the X band.

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