Integrated double-layer shielding film and preparation and application thereof

Abstract

The invention relates to an integrated double-layer shielding film and preparation and application thereof.The preparation method of the double-layer shielding film comprises the following steps that S1, blocky liquid metal and absolute ethyl alcohol are mixed and subjected to ultrasonication treatment, and small liquid metal particles are obtained; s2, thermoplastic polyurethane is dissolved in an organic solvent, then the small liquid metal particles obtained in the S1 are added, ultrasonic dispersion is conducted, then electrostatic spinning is conducted, and a fiber membrane is obtained; s3, Ecoflex A is taken to be mixed with the small liquid metal particles in the S1, BaTiO3 particles and blocky liquid metal are sequentially added under the stirring condition, then Ecoflex B is added, stirring is conducted, and a colloid mixture solution is formed; and S4, uniformly coating the colloid mixture solution obtained in S3 on the surface of the fiber film obtained in S2, and curing to obtain the integrated double-layer shielding film. Compared with the prior art, the prepared composite double-layer film shows excellent shielding performance, interfaces between the circuit layer and the shielding layer are tightly combined, and the composite double-layer film has good application potential in the field of electromagnetic shielding.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electromagnetic shielding materials, and relates to an integrated double-layer shielding film and preparation and application thereof. BACKGROUND

[0002] With the rapid development of modern science and technology using electromagnetic waves as information carriers, human society is accelerating into the intelligent era of Internet of Everything. Under the dual driving of the fully deployed 5G communication network and the emerging 6G frontier technology, the application frequency band of electromagnetic waves continues to expand, and the transmission power is significantly enhanced. However, this technological progress, while bringing efficient experience, has also caused increasingly serious electromagnetic environmental problems. Under this background, the development of advanced electromagnetic wave shielding materials with excellent performance has become the only way to crack the electromagnetic pollution dilemma and build a safe electromagnetic environment. In the field of electromagnetic wave shielding materials, component regulation and structure design play a crucial role as two core strategies. In view of the difficulty in improving the intrinsic function of composite materials, it is necessary to design materials with complex components to realize multifunctionality, thereby broadening the application field of materials and improving the electromagnetic shielding performance.

[0003] Liquid metal has high electrical conductivity, fluid deformability, and self-repairing ability, providing a solid foundation for flexible electronic technology. When cleverly embedded into a polymer substrate, liquid metal materials can form a stretchable and fatigue-resistant conductive network that still maintains stable access under complex three-dimensional deformation. However, the easy flow property of liquid metal under tensile stress can lead to leakage and migration risks in material design. The inherent high surface tension of liquid metal and limited physical adhesion to most soft substrates exacerbate the problem of interfacial separation in composite multilayer materials, while the mismatch of mechanical properties between different interfaces hinders seamless integration with auxiliary functional layers. In addition, the relatively large density and fluid flow often lead to liquid metal particle deposition or agglomeration, which hinders the liquid metal from exerting its superior thermoelectric performance. Therefore, there is an urgent need to develop an integrated double-layer shielding film preparation technology that is simple and low-cost and suitable for large-scale production, while also requiring multifunctionality to meet the practical application needs in the field of shielding materials. SUMMARY

[0004] The purpose of the present application is to provide an integrated double-layer shielding film and its preparation and application, to obtain a composite double-layer film that exhibits excellent shielding performance and a tightly bonded interface between the circuit layer and the shielding layer.

[0005] The application finds that the synthesis strategy of the composite multilayer material is relatively complex, and the bonding force between the two layers is weak, which leads to the inability to withstand deformation and repeated use in the application process, the difficulty in controlling the shielding performance of the material, and the weak competitiveness in the aspects of environmental friendliness and multi-field application. Based on the above problems, the application designs an integrated double-layer shielding film, and the interface is cleverly connected through a simple electrospinning technology and a one-step casting method, so that a material with excellent shielding performance is obtained.

[0006] The object of the application can be achieved by the following technical solutions: In a first aspect, the application provides a preparation method of an integrated double-layer shielding film, comprising the following steps: S1, mixing a block-shaped liquid metal with anhydrous ethanol, and performing ultrasonic crushing treatment to obtain liquid metal small particles with a size of 2-3 microns; S2, dissolving thermoplastic polyurethane in an organic solvent, then adding the liquid metal small particles obtained in S1 and performing ultrasonic dispersion, and then performing electrospinning on the obtained suspension to obtain a fiber film; S3, mixing Ecoflex A with the liquid metal small particles in S1, then adding BaTiO3 particles and block-shaped liquid metal under stirring, and then adding Ecoflex B and stirring to form a colloidal mixture solution; S4, uniformly coating the colloidal mixture solution of S3 on the surface of the fiber film obtained in S2, and solidifying to obtain an integrated double-layer shielding film.

[0007] Further, in S1, the block-shaped liquid metal is an EGaIn eutectic alloy.

[0008] Further, in S1, the ultrasonic crushing treatment process is: under an ice water bath, treating for 10-30 min at 80% rated power, and the equipment rated power is 600 W.

[0009] Further, in S2, the mass ratio of thermoplastic polyurethane, liquid metal small particles and organic solvent is 9 g: (0.8-4.0) g: 20 g, and the organic solvent is hexafluoroisopropanol (HFIP).

[0010] Further, in S2, the process parameters of electrospinning are: the sample flow rate is 0.8-1.2 mL / h, the receiver rotation speed is 100-120 rpm, the distance between the nozzle and the receiver is 8-12 cm, and the applied voltage is 14.0-16.0 kV.

[0011] Further, in S3, the mass ratio of Ecoflex A, liquid metal small particles, BaTiO3 particles, bulk liquid metal, Ecoflex B is (0.8~1.2):(1.8~2.2):(0.12~0.18):(4.5~5.5):(0.8~1.2).

[0012] Further, in S4, the coating amount of the colloidal mixture solution is (0.5~1.5) mL per 1 cm 2 The surface area of the fiber film.

[0013] Further, in S4, the curing temperature is 50~70℃, preferably 60℃, and the curing time is 4~6h, preferably 5h.

[0014] In the second aspect, the application provides an integrated double-layer shielding film prepared by the preparation method of the first aspect.

[0015] In the third aspect, the application provides an application of the integrated double-layer shielding film in the field of electromagnetic shielding.

[0016] Compared with the prior art, the application has the following advantages: (1) The material provided by the application is applied in the field of electromagnetic shielding, and the minimum reflection loss reaches-58.1 dB at 8~12 GHz.

[0017] (2) The preparation method provided by the application has a simple synthesis route and low cost, and the obtained product can be recycled and used, so that large-scale production and application in multiple fields can be realized.

[0018] (3) The liquid metal spherical particles in the fiber can be arranged in a direction, and the distribution density of the particles can be controlled, so that the shielding efficiency is improved. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 The scanning electron microscope images of the morphologies of various samples; Figure 2 The stress-strain curve graphs of the fiber films with different distribution densities of liquid metal particles; Figure 3 The electromagnetic shielding performance curve graphs of the samples; Figure 4 The thermal conductivity performance graphs of different samples. DETAILED DESCRIPTION

[0020] The application will be described in detail below with reference to the drawings and specific embodiments. The embodiments are implemented on the premise of the technical solution of the application, and detailed implementation methods and specific operation processes are given, but the protection scope of the application is not limited to the following embodiments.

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description herein is for describing particular embodiments only and is not intended to be limiting of the application.

[0022] The alternative ranges of the terms "and / or", "or / and", "and / or" used herein include any one of two or more associated listed items, and also include any and all combinations of the associated listed items, including any two associated listed items, any more associated listed items, or a combination of all associated listed items. It should be noted that when at least three items are connected by a conjunction of at least two selected from "and / or", "or / and", "and / or", it should be understood that in this application, the technical solution undoubtedly includes the technical solution connected by "logical and", and also undoubtedly includes the technical solution connected by "logical or".

[0023] In this application, the technical features described in an open form include both the closed technical solution consisting of listed features and the open technical solution containing the listed features.

[0024] In this application, when referring to a numerical interval, unless otherwise specified, the numerical interval is considered to be continuous and includes the minimum value and the maximum value of the range, as well as every value between the minimum value and the maximum value. Further, when the range refers to an integer, every integer between the minimum value and the maximum value of the range is included. In addition, when multiple ranges are provided to describe a feature or a characteristic, the ranges can be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all sub-ranges encompassed therein.

[0025] Only some numerical ranges are specifically disclosed herein. However, any lower limit can be combined with any upper limit to form a range not explicitly recited; and any lower limit can be combined with other lower limits to form a range not explicitly recited, and likewise any upper limit can be combined with any other upper limit to form a range not explicitly recited. In addition, each individual disclosed point or single numerical value can itself be combined as a lower limit or an upper limit with any other point or single numerical value or with other lower limits or upper limits to form a range not explicitly recited.

[0026] In this application, the temperature parameters, unless otherwise specified, allow for constant temperature processing, and also allow for processing within a certain temperature interval. The constant temperature processing allows for fluctuations within the accuracy range controlled by the instrument. Fluctuations within a range such as ±5°C, ±4°C, ±3°C, ±2°C, ±1°C are allowed.

[0027] In the present application, "suitable", "suitable", "any suitable manner" and the like are described in the "suitable" manner, which can implement the technical solutions of the present application, solve the technical problems of the present application, and achieve the intended technical effects of the present application.

[0028] In the present application, "further", "more further", "particularly" and the like are used to describe the purpose, which means the difference in content, but should not be understood as a limitation on the protection scope of the present application.

[0029] In the present application, "optionally", "optional" and "optional" mean optional, that is, selected from any one of the two parallel schemes of "have" or "have". If there are multiple "optional" in a technical solution, unless otherwise specified, and there is no contradictory relationship or mutual restriction, each "optional" is independent.

[0030] In the description of the application, "multiple" means at least two, for example, two, three, etc., unless otherwise specifically limited.

[0031] Unless otherwise specified, all formulations and tests in the present application occur in an environment of 25°C.

[0032] In the present application, "include", "contain", "contain", "contain", "have" or other variants are intended to cover non-closed inclusion, and there is no distinction between these terms. The term "contains" means that other steps and ingredients can be added without affecting the final result. The composition and method / process of the present application comprises, consists of and consists essentially of the essential elements and limitations described herein and any additional or optional ingredients, components, steps or limitations described herein. There is no distinction between the terms "efficiency", "performance", "effect", "efficacy" in the present application.

[0033] If not specified, all embodiments and optional embodiments of the present application can be combined to form new technical solutions. If not specified, all technical features and optional technical features of the present application can be combined to form new technical solutions.

[0034] If not specified, all steps of the present application can be performed in sequence or randomly, preferably in sequence.

[0035] In the following examples, hexafluoroisopropanol (HFIP), barium titanate (BaTiO3) and ethanol were purchased from Shanghai Reagent Co., Ltd. Thermoplastic polyurethane (TPU, model 1175A) was purchased from Hefei Yuanli Instrument Technology Co., Ltd., and Ecoflex silicone was purchased from Smooth-On company.

[0036] Example 1: Preparation of 3-LM@TPU-LM@Ecoflex electromagnetic shielding film with double-layer structure: First, 1 g of bulk liquid metal (EGaIn eutectic alloy, specification: Ga 75.5%, In 24.5%, purchased from Aladdin) was dispersed in 20 mL of ethanol and ultrasonically treated at 80% power (i.e. 480 W) with a device rated power of 600 W. During the process, the beaker was placed in an ice water bath to keep it cool. The obtained particles were sieved by centrifugal treatment for 10 min, and the precipitate was dried for 12 h to obtain the desired liquid metal particles (size 2-3 microns); Secondly, 9 g of TPU was dissolved in 20 g of HFIP solvent, and magnetic stirring was carried out in a 60°C oil bath for 2 h, and stirring was continued at room temperature for 5 h, and then 1 g of liquid metal particles was added and stirred to form a uniform viscous solution; Then, the obtained viscous solution was introduced into the electrospinning machine, the sample flow rate of the electrospinning machine was 1.0 mL / h, the receiver rotation speed was 110 rpm, the distance between the nozzle and the receiver was 10 cm, and the applied voltage was 16.0 kV, and the LM@TPU fiber film with a filling ratio of 10% (i.e. the mass fraction content of liquid metal was 10%) was prepared; Subsequently, the previously prepared fiber film was laid flat in a PTFE mold, and the colloidal mixture was uniformly coated on its surface, and the colloidal coating amount was 1 mL per 1 cm 2 The surface area of the fiber film. Then the mold was placed in a 60°C oven for curing and kept for 5 h to obtain the target integrated 1-LM@TPU-LM@Ecoflex double-layer film.

[0037] Here, the colloidal mixture used was prepared by the following method: 1.0 g of Ecoflex A and 2.0 g of LM nanoparticles (i.e. liquid metal particles) were mixed and mechanically stirred for 90 minutes to make them uniformly distributed. Subsequently, 0.15 g of BaTiO3 particles was added and stirring was continued for 20 minutes. Then, 5.0 g of bulk liquid metal was added and mechanically stirred for 5 minutes. Finally, an equal amount of 1.0 g of Ecoflex B was added and stirred for 3 minutes to form a well-dispersed colloidal mixture solution.

[0038] Example 2: Preparation of 2-LM@TPU-LM@Ecoflex electromagnetic shielding film with double-layer structure: Compared with Example 1, most of them are the same, except that the content of liquid metal particles added in the solution of the spinning precursor is adjusted to 2.3 g, corresponding to a 20% filling ratio of LM@TPU fiber film.

[0039] Example 3: Preparation of 3-LM@TPU-LM@Ecoflex electromagnetic shielding film with double-layer structure: Most of them are the same as in Example 1, except that the content of liquid metal particles added in the solution of the spinning precursor is changed to 3.9 g, corresponding to a 30% filling ratio of LM@TPU fiber film.

[0040] Characterization and performance test experiments The one-dimensional beaded LM@TPU fiber micro-morphology in the above examples is characterized by scanning electron microscopy (SEM, Hitachi SEM S-8600), and the sample preparation method is as follows: a small amount of fiber sample is placed on the conductive glue and the morphology is observed.

[0041] Figure 1 The scanning electron microscope images of the prepared LM@TPU fibers with different distribution densities are shown in Figure 1. Figure 1(a) shows that 10% of the liquid metal is confined in the fiber (i.e., 10% filling ratio of LM@TPU fiber film), and the particles in the fiber exhibit obvious protruding structures. Figure 1(b) shows that the proportion of protruding structures increases when the liquid metal content is 20% (i.e., 20% filling ratio of LM@TPU fiber film). Figure 1(c) shows a large number of protruding structures when the liquid metal content is 30% (i.e., 30% filling ratio of LM@TPU fiber film). The consistent morphology of the three fibers indicates that the controllable adjustment of the distribution density is successfully achieved, and the beaded LM@TPU fiber is successfully synthesized.

[0042] Figure 2 The stress-strain test curve of the sample prepared in Example 1 above is shown in Figure 2. It can be seen that the tensile resistance of the sample gradually increases as the proportion of introduced liquid metal spherical particles increases, and the strain increases from 234% to 507%. The introduction of protruding structures increases the toughness of the fiber.

[0043] Figure 3 The reflection loss value of the double-layer LM@TPU-LM@Ecoflex film prepared in the above example at a frequency of 8.0-12.0 GHz. The specific test method is as follows: a rectangular film with a size of 22 mm x 11 mm x 3 mm is fixed in the sample clamp. The S parameters and electromagnetic parameters of the LM@TPU-LM@Ecoflex double-layer film are tested on a vector network analyzer (N5230C, Keysight) by waveguide method. As can be seen from the figure: the 3-LM@TPU-LM@Ecoflex film with a large number of protruding structures has excellent electromagnetic shielding performance, and the minimum reflection loss reaches -58.1 dB.

[0044] Comparative Example 1: Compared to Example 1, except that the addition of BaTiO3 particles was omitted during the preparation of the colloidal mixture solution, the thermal conductivity of the sample was tested. The comparison showed that the thermal conductivity of the sample without BaTiO3 decreased from 5.56 W / m². -1 K -1 Reduced to 4.95 W m -1 K -1 .

[0045] Comparative Example 2: Compared to Example 1, except that Ecoflex A and Ecoflex B were replaced with an equal total mass of the commonly used curing component, pure PDMS colloid, during the preparation of the colloidal mixture solution. After testing, it was found that replacing the colloid did not achieve the convenience of curing at room temperature, and poor adhesion easily occurred between the two layers. Therefore, choosing Ecoflex as the curing component ensures better interfacial bonding between the substances.

[0046] in addition, Figure 4 The thermoelectric properties of the bilayer structure films prepared in Examples 1 to 3, the single-layer liquid metal fiber film (i.e., the LM@TPU fiber film in Example 1), and the pure Ecoflex colloidal film (i.e., the single-layer film obtained by curing a colloidal mixture without the LM@TPU fiber film compared to Example 1) are shown.

[0047] As can be seen from the above, the bilayer LM@TPU-LM@Ecoflex film formed by this invention has the following advantages: the protrusion structure formed in the fibers reshapes the internal distribution of the spherical conductive particles, resulting in a customizable conductive path for the flowable liquid metal within the film. This design breaks away from the traditional rigid circuit design, providing a new structural paradigm for flexible multifunctional electronic materials; furthermore, the unique bilayer film introduces an effective interfacial bonding strategy, enhancing the electromagnetic shielding performance of the material. In summary, the prepared sample not only achieves lightweight and recyclability but also possesses excellent electromagnetic shielding performance, showing particularly promising application prospects in 5G communications.

[0048] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A method for preparing an integrated double-layer shielding film, characterized in that, Includes the following steps: S1. Mix the bulk liquid metal with anhydrous ethanol and then ultrasonically break it up to obtain liquid metal particles with a size of 2-3 micrometers. S2. Dissolve thermoplastic polyurethane in an organic solvent, then add the liquid metal particles obtained in S1, disperse by ultrasonication, and then electrospin the resulting suspension to obtain a fiber membrane. S3. Take Ecoflex A and mix it with the liquid metal particles in S1. Then, under stirring conditions, add BaTiO3 particles and block liquid metal in sequence, followed by Ecoflex B and stirring to form a colloidal mixture solution. S4. The colloidal mixture solution of S3 is uniformly coated on the surface of the fiber membrane obtained in S2 and cured to obtain an integrated double-layer shielding film.

2. The method for preparing an integrated double-layer shielding film according to claim 1, characterized in that, In S1, the bulk liquid metal is an EGaIn eutectic alloy.

3. The method for preparing an integrated double-layer shielding film according to claim 1, characterized in that, In S1, the ultrasonic fragmentation process is as follows: under an ice-water bath, the ultrasonic equipment is processed at 80% of its rated power for 10-30 minutes, and the rated power of the ultrasonic equipment used is 600W.

4. The method for preparing an integrated double-layer shielding film according to claim 1, characterized in that, In S2, the mass ratio of thermoplastic polyurethane, liquid metal particles and organic solvent is 9:(0.8~4.0):20, and the organic solvent is hexafluoroisopropanol.

5. The method for preparing an integrated double-layer shielding film according to claim 1, characterized in that, In S2, the process parameters for Jingsi spinning are: feed flow rate of 0.8~1.2 mL / h, receiver rotation speed of 100~120 rpm, distance between nozzle and receiver of 8~12 cm, and applied voltage of 14.0~16.0 kV.

6. The method for preparing an integrated double-layer shielding film according to claim 1, characterized in that, In S3, the mass ratio of Ecoflex A, liquid metal particles, BaTiO3 particles, bulk liquid metal, and Ecoflex B is (0.8~1.2):(1.8~2.2):(0.12~0.18):(4.5~5.5):(0.8~1.2).

7. The method for preparing an integrated double-layer shielding film according to claim 1, characterized in that, In S4, the coating amount of the colloidal mixture solution is (0.5~1.5) mL / cm². 2 Surface area of ​​fiber membrane.

8. The method for preparing an integrated double-layer shielding film according to claim 1, characterized in that, In S4, the curing temperature is 50~70℃.

9. An integrated double-layer shielding film, characterized in that, It is prepared by the preparation method described in any one of claims 1-8.

10. The application of the integrated double-layer shielding film as described in claim 9 in the field of electromagnetic shielding.

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