Electromagnetic shielding film and preparation method and application thereof

Abstract

The application provides an electromagnetic shielding film, which adopts a polyvinyl alcohol-water-multi-walled carbon nanotube mixed material as a film base body and adopts liquid metal gallium-indium alloy nanoparticles as functional fillers; the liquid metal gallium-indium alloy nanoparticles are inlaid in a lower part of the film base body to form a functional filler layer in a stack shape. The electromagnetic film sample has excellent electromagnetic shielding performance, and has the advantages of flexibility, plasticity and strong mechanical performance, and can fully adapt to various use environments.

Description

Technical Field

[0001] This invention relates to the field of electromagnetic shielding composite materials technology, and more specifically, to an electromagnetic shielding film, its preparation method, and its application. Background Technology

[0002] In recent years, the rapid development of information technology has driven the continuous upgrading of military communication systems, leading to the increasingly widespread application of electromagnetic shielding materials in the military field. Electromagnetic shielding materials are a technical means of eliminating the adverse effects of electromagnetic waves by cutting off their propagation path. By covering the surfaces of weapons and equipment with electromagnetic shielding materials, electromagnetic waves can be effectively blocked and absorbed, reducing the damage caused by electromagnetic pulses. Furthermore, in command and control modules, which serve as the "brain" and "nerve center" for coordinating joint operations among various ground forces during wartime, the application of electromagnetic shielding materials can achieve signal filtering and isolation, ensuring the survivability of the command and control system. Faced with increasingly complex battlefield environments, electromagnetic shielding materials are required to develop towards lighter weight and greater intelligence. Metals, as traditional electromagnetic shielding materials, possess excellent electrical conductivity. However, due to the high density, fixed performance parameters, and inconvenient processing and manufacturing of metals, their development in the field of intelligent electromagnetic shielding materials is limited.

[0003] CN 118076077A discloses a multifunctional flexible electromagnetic shielding film product and its preparation method. The electromagnetic shielding film structure, from top to bottom, includes a superhydrophobic layer, a transition layer, an absorption layer, and a reflective layer. It is prepared layer by layer using a vacuum filtration method, followed by drying, separation, hot pressing, and finally spraying to prepare the superhydrophobic layer, thus creating the multifunctional flexible electromagnetic shielding film product. The film product uses dopants including fluorinated silica nanoparticles, bacterial cellulose, and carbon nanotubes coated with iron oxide, etc., involving a large number and complexity of materials, and a cumbersome preparation process. The film product has fixed properties and cannot achieve intelligent response of electromagnetic shielding performance. CN118110028A discloses a multi-layered flexible superhydrophobic high-absorption electromagnetic shielding composite film and its preparation method. It uses traditional electrospinning technology to prepare a silver nanowire-polyurethane fiber membrane. This electromagnetic shielding composite film is flexible and lightweight, possessing a multi-layered shielding mechanism of "absorption-reflection-reabsorption," but the preparation process is relatively complex, the highest electromagnetic shielding effectiveness is 54 dB, and it cannot achieve intelligent response of electromagnetic shielding performance. Summary of the Invention

[0004] To overcome the deficiencies of the prior art, the present invention provides an electromagnetic shielding film. The electromagnetic shielding film uses a polyvinyl alcohol-water-multi-walled carbon nanotube hybrid material as the film matrix and liquid gallium indium alloy nanoparticles as the functional filler. The liquid gallium indium alloy nanoparticles are embedded in the lower part of the film matrix and stacked to form a functional filler layer. The liquid gallium indium alloy nanoparticles are added to a polyvinyl alcohol-water-multi-walled carbon nanotube suspension at a mass ratio of (1~5):26 and mixed evenly. Then, the electromagnetic shielding film is obtained by casting, constant temperature and humidity water-locking treatment, and force-controlled induction treatment.

[0005] The electromagnetic shielding film contains 20-25% water by mass percentage; the functional filler layer has a thickness of 1 / 10 to 1 / 3 of the electromagnetic shielding film thickness; and the liquid metal gallium indium alloy nanoparticles have a particle size of 1-5µm.

[0006] Preferably, the mass ratio of polyvinyl alcohol, multi-walled carbon nanotubes and liquid metal gallium indium alloy nanoparticles in the electromagnetic shielding film is 5: (0.05~0.2): (1~5).

[0007] Preferably, the liquid gallium-indium alloy nanoparticles are prepared by dispersing liquid gallium-indium alloy in ethanol and then removing the ethanol by centrifugation; by mass percentage, the liquid gallium-indium alloy contains 75.5% gallium and 24.5% indium.

[0008] Preferably, the multi-walled carbon nanotubes have a diameter of 5–50 nm and a length of 5–20 µm.

[0009] The present invention also provides a method for preparing an electromagnetic shielding film, wherein liquid gallium indium alloy nanoparticles are added to a polyvinyl alcohol-water-multi-walled carbon nanotube suspension at a mass ratio of (1~5):26 and mixed evenly, and then the electromagnetic shielding film is obtained by casting, constant temperature and humidity water-locking treatment, and force-controlled induction treatment.

[0010] The constant temperature and humidity water-locking treatment involves placing the film product obtained by casting in an environment with a temperature of 20~30℃ and a humidity of 60% to dehydrate it to a water content of 20~25%; the force-controlled induction treatment involves uniaxially stretching the film obtained by the constant temperature and humidity water-locking treatment to 120~240% of its original length.

[0011] Preferably, the liquid gallium-indium alloy is prepared by mixing gallium and indium in a mass ratio of 75.5:24.5 and then heating at 60°C for 1 hour.

[0012] Preferably, the polyvinyl alcohol-water-multi-walled carbon nanotube suspension is prepared by adding polyvinyl alcohol to water, mixing it evenly at 90~98°C, and then adding multi-walled carbon nanotubes; the mass ratio of polyvinyl alcohol, water and multi-walled carbon nanotubes is 5:20:(0.05~0.2).

[0013] A further preferred preparation step is as follows:

[0014] Step 1: Add polyvinyl alcohol to water, mix and heat to 95°C and stir evenly, then add multi-walled carbon nanotubes to obtain a polyvinyl alcohol-water-multi-walled carbon nanotube suspension; the mass ratio of polyvinyl alcohol, water and multi-walled carbon nanotubes is 5:20:0.2.

[0015] Step 2: Disperse the liquid gallium-indium alloy in ethanol, centrifuge at 4000 rpm for 20 min, and separate the ethanol to obtain liquid gallium-indium alloy nanoparticles; the gallium-indium alloy is prepared by mixing gallium and indium in a mass ratio of 75.5:24.5 and heating at 60°C for 1 h; the particle size of the liquid gallium-indium alloy nanoparticles is 1~5 µm;

[0016] Step 3: Add the liquid gallium indium alloy nanoparticles obtained in Step 2 to the polyvinyl alcohol-water-multi-walled carbon nanotube suspension obtained in Step 1 at a mass ratio of 5:25.2, mix evenly, and transfer to a film-forming mold for casting.

[0017] Step 4: Place the film obtained in Step 3 in an environment with a constant temperature of 20~30℃ and a constant humidity of 60% to dehydrate it until the water content is 20~25%;

[0018] The method for determining the moisture content is as follows: First, weigh and record the mass of the molding mold (PTFE mold). Then, weigh the total mass of the mold and the film after casting in step 3. The change in mass between the two is the mass of the film at the determined moment. Second, calculate the mass of the film when the moisture content is 20% to 25% based on the total mass of the materials fed in steps 1 to 3 and the mass of water. Finally, place the molding mold and the film together on a weighing instrument to tare and weigh in real time. Then, perform constant temperature and humidity water-locking treatment. When the mass displayed by the weighing instrument is consistent with the mass of the film when the moisture content is 20% to 25%, remove the film to obtain the film treated with constant temperature and humidity water-locking.

[0019] Step 5: uniaxially stretch the film obtained in Step 4 to 230-235% of its original length and / or reduce its thickness to 40-50% of its original thickness to obtain an electromagnetic shielding film.

[0020] The electromagnetic shielding film obtained by the technical solution of this invention is applied to the electromagnetic shielding of electronic devices.

[0021] Preferably, the prepared electromagnetic shielding film is applied to electronic devices after undergoing force-controlled stretching treatment. The electromagnetic shielding film obtained by the present invention possesses intelligent response characteristics after film formation, enabling it to flexibly adjust its electromagnetic shielding parameters to adapt to different performance requirements when the application scenario changes. Here, intelligent response refers to the characteristic of further force-controlled stretching treatment of the prepared electromagnetic shielding film according to different performance requirements, thereby altering its electromagnetic shielding parameters.

[0022] Beneficial effects:

[0023] Compared with the prior art, the advantages of the present invention are:

[0024] 1. The preparation process is simple, requires no complicated operations, and the size of the prepared sample is only affected by the sample mold, which can realize the mass production of samples.

[0025] 2. The polyvinyl alcohol matrix does not completely lose water during the film-forming stage. Under the premise of having considerable mechanical strength, the water content of 20%~25% ensures that the film is in a solid-liquid intermediate phase. The intermediate phase can ensure the film formation without restricting the fluidity of the liquid gallium indium alloy, allowing it to deform freely under stretching, connecting multi-walled carbon nanotubes, dynamically adjusting the construction of the conductive network, and realizing intelligent response of electromagnetic shielding performance.

[0026] 3. The thin film sample has excellent electromagnetic shielding performance, while also possessing the advantages of flexibility, plasticity and strong mechanical properties, making it fully adaptable to a variety of usage environments. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the force-controlled induction process of the electromagnetic shielding film prepared in Example 1.

[0028] Figure 2 The image shows the surface morphology of the electromagnetic shielding film prepared in Example 1.

[0029] Figure 3 The image shows the bottom surface morphology of the electromagnetic shielding film prepared in Example 1.

[0030] Figure 4 This is a schematic cross-sectional view of the electromagnetic shielding film prepared in Example 1 before force control induction.

[0031] Figure 5 This is a schematic diagram of the cross-section of the electromagnetic shielding film prepared in Example 1 after force control induction.

[0032] Figure 6 The performance changes of the electromagnetic shielding film prepared in Example 1 before and after force control induction.

[0033] Figures 7-11The electromagnetic shielding performance parameters of the films prepared in Example 1 with lengths of 3cm, 4cm (stretched length of 1cm), 5cm (stretched length of 2cm), 6cm (stretched length of 3cm), and 7cm (stretched length of 4cm) are shown in the following figures. Detailed Implementation

[0034] To explain in detail the technical content, structural features, objectives, and effects of the technical solution, the following description is provided in conjunction with specific embodiments and accompanying drawings.

[0035] Example 1:

[0036] Step 1: Add 5g of polyvinyl alcohol to 20ml of water (20g in mass), mix and heat to 95℃, mechanically stir for 10h to obtain a mixed solution at a stirring speed of 700rpm; then add 0.2g of multi-walled carbon nanotubes to the mixed solution to obtain a polyvinyl alcohol-water-multi-walled carbon nanotube suspension.

[0037] Step 2: Disperse the liquid gallium-indium alloy in anhydrous ethanol and ultrasonically disperse for 20 min to obtain an ethanol solution of liquid gallium-indium alloy nanoparticles; centrifuge the obtained ethanol solution of liquid gallium-indium alloy nanoparticles at 4000 rpm for 20 min, and separate the ethanol to obtain liquid gallium-indium alloy nanoparticles; the liquid gallium-indium alloy is prepared by mixing gallium and indium in a mass ratio of 75.5:24.5 and heating at 60℃ for 1 h;

[0038] Step 3: Take 0.2g of the liquid gallium indium alloy nanoparticles obtained in Step 2 and add them to the polyvinyl alcohol-water-multi-walled carbon nanotube suspension obtained in Step 1. Mix them evenly, degas the solution, and then transfer it to a molding mold (polytetrafluoroethylene mold) for casting. The sample thickness inside the mold is 1.0mm.

[0039] Step 4: After the sample obtained in Step 3 has cooled to room temperature, it is subjected to constant temperature and humidity water-locking treatment. The constant temperature and humidity water-locking treatment is to place it in an environment with a constant temperature of 20~30℃ and a constant humidity of 60% to dehydrate it to a water content of 20~25%; the resulting film has a thickness of 1.0 mm, a length of 3.0 cm, and a width of 2.0 cm.

[0040] The method for determining the moisture content is as follows: First, weigh and record the mass of the molding mold (PTFE mold). Then, weigh the total mass of the mold and the film after casting in step 3. The change in mass between the two is the mass of the film at the determined moment. Second, calculate the mass of the film when the moisture content is 20% to 25% based on the total mass of the materials fed in steps 1 to 3 and the mass of water. Finally, place the molding mold and the film together on a weighing instrument to tare and weigh in real time. Then, perform constant temperature and humidity water-locking treatment. When the mass displayed by the weighing instrument is consistent with the mass of the film when the moisture content is 20% to 25%, remove the film to obtain the film treated with constant temperature and humidity water-locking.

[0041] Step 5: The film obtained in Step 4 is subjected to force-controlled induction treatment. This treatment involves using a force-controlled induction film stretching platform to uniaxially stretch the film obtained in Step 4 to 120-240% of its original length. At this point, the thickness is reduced to 40-50% of the original thickness, resulting in an electromagnetic shielding film. The stretching platform has length markings at the bottom to observe the film's stretching process. The initial length of the electromagnetic shielding film is 3.0 mm. The single stretching length is set to 1.0 cm until it reaches 7.0 cm, reaching the film's limit (after multiple tests, it was found that further stretching would cause the film to break easily). Electromagnetic shielding films with lengths of 3 cm, 4 cm (stretched length 1 cm), 5 cm (stretched length 2 cm), 6 cm (stretched length 3 cm), and 7 cm (stretched length 4 cm, at which point the film thickness is measured to be 0.5 mm) are obtained.

[0042] Figure 1 The process of uniaxial force-controlled induced stretching of the prepared electromagnetic shielding film was demonstrated. After multiple experiments, the film obtained the best electromagnetic shielding performance when it was stretched to 200%~240% of its initial length. If it was stretched further, the film would be in a state of easy breakage and would not have the function of electromagnetic shielding.

[0043] Figure 2 , 3 The images shown are the surface morphology and bottom morphology of the electromagnetic shielding film prepared in this embodiment.

[0044] Figure 4 This is a cross-sectional schematic diagram of the electromagnetic shielding film obtained in the initial state of this embodiment. At this time, the thickness of the functional filler layer is 1 / 10 to 1 / 8 of the thickness of the electromagnetic shielding film. Figure 5 This is a cross-sectional view of the electromagnetic shielding film prepared in this embodiment when it is force-controlled stretched to 240% of its initial length. At this point, the thickness of the functional filler layer is 1 / 4 to 1 / 3 of the thickness of the electromagnetic shielding film. Electromagnetic shielding performance tests were performed on the electromagnetic shielding film before and after force-controlled stretching, and the test results are as follows: Figure 6 As shown, the electromagnetic shielding performance increased from 7~8dB to 45~48dB.

[0045] Measuring electromagnetic shielding performance

[0046] The electromagnetic shielding performance of the films in step 6 with lengths of 3cm, 4cm (stretch length of 1cm), 5cm (stretch length of 2cm), 6cm (stretch length of 3cm), and 7cm (stretch length of 4cm) was measured. The electromagnetic shielding parameters obtained by the test were 7.55 dB, 15.21 dB, 24.01 dB, 33.96 dB, and 46.11 dB, respectively.

[0047] Using electromagnetic shielding films with lengths of 3cm, 4cm (stretched length of 1cm), 5cm (stretched length of 2cm), 6cm (stretched length of 3cm), and 7cm (stretched length of 4cm, with a film thickness of 0.5mm) prepared in Example 1 as the measurement objects, the process of electromagnetic shielding performance testing and the process of obtaining electromagnetic shielding performance parameters (corresponding to 7.55 dB, 15.21dB, 24.01dB, 33.96 dB, and 46.11 dB respectively) are illustrated.

[0048] (1) Introduction and explanation of electromagnetic shielding performance characterization parameters:

[0049] Electromagnetic shielding materials typically achieve their shielding effect against electromagnetic waves through three shielding mechanisms. The reflection loss (SE) that is carried away by the material surface is the reflection loss. R The absorption loss SE is what is attenuated within the material. A However, multiple reflection losses are often negligible. The electromagnetic shielding performance of a material is evaluated using electromagnetic shielding effectiveness, measured in decibels (dB). Therefore, shielding effectiveness is equal to SE. R +SE A ;

[0050]

[0051] (2) Introduction and explanation of the electromagnetic shielding test process:

[0052] The electromagnetic shielding performance of the material was tested using a vector network analyzer. For thin-film materials, the waveguide method was used. The electromagnetic shielding effectiveness of the material was obtained by calculating the S-parameters of the material in different wavebands.

[0053] The waveguide method is typically used to test the S-parameters of materials, yielding four sets of data: S11, S21, S22, and S12. The first subscript indicates the receiving port, and the second subscript indicates the transmitting port. For example, S21 means port 1 transmits the signal, and port 2 receives the signal. Therefore, when calculating the electromagnetic shielding effectiveness of a material, S11 and S21 are usually calculated together, and S22 and S12 are calculated together.

[0054]

[0055]

[0056] The electromagnetic shielding film prepared in Example 1 was subjected to force-controlled stretching treatment to obtain electromagnetic shielding films with lengths of 3cm, 4cm (stretch length of 1cm), 5cm (stretch length of 2cm), 6cm (stretch length of 3cm), and 7cm (stretch length of 4cm, at which time the thickness of the film was measured to be 0.5mm).

[0057] Then, electromagnetic shielding tests were performed separately, and the S values ​​were measured based on vector network analysis. 11 S 21 Then, the computer calculates the result by simultaneously solving formulas 1 and 2. Figures 7-11 The SE and P parameters shown are used to calculate the SE data. Figure 7 P R P T P A Parameters and SE A SE R The parameters correspond to the electromagnetic shielding film with a length of 3cm obtained in Example 1, and the calculated SE is 7.55dB; Figure 8 P R P T P A Parameters and SE A SE R The parameters correspond to the electromagnetic shielding film with a length of 4 cm obtained in Example 1, and the calculated SE is 15.21 dB; Figure 9 P R P T P A Parameters and SE A SE R The parameters correspond to the 5cm long electromagnetic shielding film obtained in Example 1, and the calculated SE is 24.01 dB. Figure 10 P R P T P A Parameters and SE A SE RThe parameters correspond to the electromagnetic shielding film with a length of 6 cm obtained in Example 1, and the calculated SE is 33.96 dB; Figure 11 The PR, PT, PA parameters, and SEA, SER parameters correspond to the electromagnetic shielding film with a length of 7 cm obtained in Example 1, and the calculated SE is 46.11 dB. The data shows that the electromagnetic shielding film prepared by this invention has good intelligent response characteristics, and can flexibly adjust its electromagnetic shielding parameters to adapt to different performance requirements when the application scenario changes. Here, intelligent response refers to subjecting the prepared electromagnetic shielding film to force-controlled stretching treatment according to different performance requirements to obtain gradient electromagnetic shielding parameters (7.55 dB, 15.21 dB, 24.01 dB, 33.96 dB, and 46.11 dB respectively) to adapt to different scenario requirements.

[0058] Example 2:

[0059] The other processes are the same as in Example 1, except that in step 2, 3 g of liquid gallium-indium alloy is added. The electromagnetic shielding performance before and after force-controlled stretching is recorded as 5.18 dB and 35.19 dB, respectively. Here, "before force-controlled stretching" refers to the electromagnetic shielding film at its initial length, and "after force-controlled stretching" refers to stretching to 7.0 cm. Examples 3-8 are described later; Comparative Examples 2-3 are understood in the same way.

[0060] Example 3:

[0061] The other processes are the same as in Example 1, except that in step 2, 3 g of liquid gallium-indium alloy is added. The electromagnetic shielding performance before and after force-controlled stretching is recorded as 5.18 dB and 35.19 dB, respectively.

[0062] Example 4:

[0063] The other processes are the same as in Example 1, except that in step 2, 2 g of liquid gallium-indium alloy is added. The electromagnetic shielding performance before and after force-controlled stretching is recorded as 4.99 dB and 22.96 dB, respectively.

[0064] Example 5:

[0065] The other processes are the same as in Example 1, except that in step 2, 1 g of liquid gallium-indium alloy is added. The electromagnetic shielding performance before and after force-controlled stretching is recorded as 5.05 dB and 16.57 dB, respectively.

[0066] Example 6:

[0067] The other processes are the same as in Example 1, except that in step 1, 0.15 g of multi-walled carbon nanotubes were added. The electromagnetic shielding performance before and after force-controlled stretching was recorded as 6.41 dB and 32.67 dB, respectively.

[0068] Example 7:

[0069] The other processes are the same as in Example 1, except that in step 1, 0.10 g of multi-walled carbon nanotubes were added. The electromagnetic shielding performance before and after force-controlled stretching was recorded as 6.39 dB and 30.54 dB, respectively.

[0070] Example 8:

[0071] The other processes were the same as in Example 1, except that 0.05 g of multi-walled carbon nanotubes were added in step 1. The electromagnetic shielding performance before and after force-controlled stretching was recorded as 6.49 dB and 28.72 dB, respectively.

[0072] Comparative Example 1:

[0073] Other processes are as described in Example 1. To determine the internal phase relationship of the electromagnetic shielding film, the changes in film performance under different water contents were compared. In step 5, the sample was placed in a constant temperature and humidity chamber for 24 hours to complete the preparation. At this time, the water content of the sample was 50%, but if the water content was too high, film formation would be impossible.

[0074] Comparative Example 2:

[0075] Other processes are the same as in Example 1, except that in step 5, the sample is placed in a constant temperature and humidity chamber for 96 hours to complete the preparation. At this time, the water content of the sample is 0%, and the electromagnetic shielding performance of the film before and after force-controlled stretching is 6.89 dB and 7.01 dB, respectively, which is basically unchanged.

[0076] Comparative Example 3:

[0077] The other processes are the same as in Example 1, except that the polyvinyl alcohol matrix in step 1 is replaced with PDMS (polydimethylsiloxane) material. Specifically, 25 g of PDMS is weighed, and then 2.5 g of ligand is added to obtain a mixed solution. In step 4, after degassing the solution, it is poured into a horizontally placed polytetrafluoroethylene mold. The sample thickness in the mold is 1.0 mm. After heating in an oven at 60°C for 1 h, an electromagnetic shielding film is prepared. The electromagnetic shielding performance of the film before and after force-controlled stretching is 7.15 dB and 7.09 dB, respectively, showing essentially no change.

[0078] It should be noted that although the above embodiments have been described herein, this does not limit the scope of patent protection for this invention. Therefore, any changes and modifications made to the embodiments described herein based on the innovative concept of this invention, or equivalent structural or procedural transformations made using the description and drawings of this invention, directly or indirectly applying the above technical solutions to other related technical fields, are all included within the scope of patent protection for this invention.

Claims

1. An electromagnetic shielding film, characterized in that, the electromagnetic shielding film adopts polyvinyl alcohol-water-multi-walled carbon nanotube mixed material as a film matrix, and adopts liquid metal gallium-indium alloy particles as functional fillers; the liquid metal gallium-indium alloy particles are inlaid in the lower part of the film matrix to form a functional filler layer in a stacked shape; the liquid metal gallium-indium alloy particles are added to the polyvinyl alcohol-water-multi-walled carbon nanotube suspension in a mass ratio of (1-5): 26, and then mixed uniformly, and then the electromagnetic shielding film is prepared through casting, constant temperature and humidity water locking treatment, and force control induction treatment; the water content in the electromagnetic shielding film is 20-25% by mass fraction; the thickness of the functional filler layer is 1 / 10-1 / 3 of the thickness of the electromagnetic shielding film; and the particle size of the liquid metal gallium-indium alloy particles is 1-5 µm.

2. The electromagnetic shielding film according to claim 1, characterized in that, the feeding mass ratio of polyvinyl alcohol, multi-walled carbon nanotubes and liquid metal gallium-indium alloy particles in the electromagnetic shielding film is 5:(0.05-0.2):(1-5).

3. The electromagnetic shielding film according to claim 1, characterized in that, the liquid metal gallium-indium alloy particles are prepared by dispersing liquid metal gallium-indium alloy into ethanol, and then removing ethanol by centrifugation; the liquid metal gallium-indium alloy contains 75.5% of metal gallium and 24.5% of metal indium by mass fraction; and the diameter of the multi-walled carbon nanotubes is 5-50 nm, and the length is 5-20 µm.

4. The electromagnetic shielding film according to claim 1, characterized in that, the constant temperature and humidity water locking treatment is to place the film product obtained by casting in an environment with a temperature of 20-30 ℃ and a humidity of 60% to dehydrate to a water content of 20-25%; and the force control induction treatment is to uniaxially stretch the film obtained by the constant temperature and humidity water locking treatment to 120-240% of the original length.

5. A preparation method of the electromagnetic shielding film according to any one of claims 1-4, characterized in that, the liquid metal gallium-indium alloy particles are added to the polyvinyl alcohol-water-multi-walled carbon nanotube suspension in a mass ratio of (1-5): 26, and then mixed uniformly, and then the electromagnetic shielding film is prepared through casting, constant temperature and humidity water locking treatment, and force control induction treatment; the constant temperature and humidity water locking treatment is to place the film product obtained by casting in an environment with a temperature of 20-30 ℃ and a humidity of 60% to dehydrate to a water content of 20-25%; and the force control induction treatment is to uniaxially stretch the film obtained by the constant temperature and humidity water locking treatment to 120-240% of the original length.

6. The preparation method according to claim 5, characterized in that, the liquid metal gallium-indium alloy is prepared by mixing metal gallium and metal indium in a mass ratio of 75.5:24.5, and then heating at 60 ℃ for 1 h.

7. The preparation method according to claim 5, characterized in that, The polyvinyl alcohol-water-multi-walled carbon nanotube suspension is prepared by adding polyvinyl alcohol into water, mixing uniformly at 90-98 ℃, and then adding multi-walled carbon nanotubes; the mass ratio of polyvinyl alcohol, water, and multi-walled carbon nanotubes is 5:20:(0.05-0.2).

8. The preparation method of claim 5, wherein, The preparation step is: Step 1: polyvinyl alcohol is added into water, mixed, heated to 95 ℃, mixed uniformly, and then multi-walled carbon nanotubes are added to obtain a polyvinyl alcohol-water-multi-walled carbon nanotube suspension; the mass ratio of polyvinyl alcohol, water, and multi-walled carbon nanotubes is 5:20:0.2; Step 2: liquid metal gallium-indium alloy is dispersed into ethanol, centrifuged at 4000 rpm for 20 min, and after separation of ethanol, liquid metal gallium-indium alloy particles are obtained; the metal gallium-indium alloy is prepared by mixing metal gallium and metal indium according to a mass ratio of 75.5:24.5, and then heating at 60 ℃ for 1 h; Step 3: the liquid metal gallium-indium alloy particles prepared in step 2 are added to the polyvinyl alcohol-water-multi-walled carbon nanotube suspension prepared in step 1 according to a mass ratio of 1:26, mixed uniformly, and transferred to a film forming mold for casting; Step 4: the film obtained by casting in step 3 is dehydrated to a water content of 20-25% in an environment with a constant temperature of 20-30 ℃ and a constant humidity of 60%; Step 5: the film obtained in step 4 is uniaxially stretched to 230-235% of the original length, and / or the thickness is reduced to 40-50% of the original thickness, to obtain an electromagnetic shielding film.

9. Use of the electromagnetic shielding film according to any one of claims 1-4 or prepared by the preparation method of any one of claims 5-8, wherein the electromagnetic shielding film is used for electromagnetic shielding of electronic devices. ​

Images