Preparation method of low-reflection degradable electromagnetic shielding multilayer composite film

Abstract

The invention relates to a preparation method of a low-reflection degradable electromagnetic shielding multilayer composite membrane, which is characterized in that based on the interaction among nanoparticles, ferroferric oxide magnetic nanoparticles are loaded on the surface of a carbon nanotube, and a magnetoelectric hybrid filler is constructed; meanwhile, degradable polylactic acid is used as a matrix, polycaprolactone is used as a toughening phase, the controllable distribution of the filler is regulated and controlled, and the local effective concentration is increased; further through structural design, asymmetric multilayer electromagnetic shielding composite materials with different impedance matching characteristics are constructed, and an absorption-reflection-reabsorption electromagnetic shielding mechanism is formed by utilizing different electromagnetic wave impedance coefficients of the absorption and reflection layers and the inter-layer impedance mismatching characteristic. By optimizing the filler components of each layer, the processing technology and other methods, the unification of low reflection, high absorption, excellent electromagnetic shielding performance and toughness performance is realized.

Description

Technical Field

[0001] This invention relates to a method for preparing a low-reflection, biodegradable electromagnetic shielding multilayer composite film, belonging to the fields of biodegradable materials and electromagnetic protection technology. Background Technology

[0002] With the rapid development of modern electronic and communication technologies, electromagnetic waves, as the core carrier of information transmission, are playing an increasingly crucial role. Electromagnetic shielding materials, as core protective components in the field of electromagnetic compatibility, are a key means of ensuring the stability of electromagnetic fields within a specific space and guaranteeing the reliable operation of electronic equipment. Currently, mainstream electromagnetic shielding materials generally possess high conductivity, achieving excellent electromagnetic shielding effects. However, they have significant drawbacks: poor impedance matching performance results in over 90% of incident electromagnetic waves being reflected into free space. This "reflection-dominated" shielding mechanism leads to severe secondary electromagnetic pollution and cannot meet the urgent needs of modern electronic equipment, new energy, and medical fields for high-performance electromagnetic shielding materials with "low reflection and high absorption." Therefore, developing new shielding materials has become a pressing technical challenge. The microstructure of a material has a decisive influence on its shielding performance: for example, porous structures can significantly improve absorption loss by constructing multi-interface reflection channels, extending the transmission path of electromagnetic waves within the material; while multilayer structures can further enhance the absorption loss ratio by controlling the spatial distribution of conductive fillers and optimizing the impedance matching characteristics between the material and free space. In summary, achieving the organic integration of different functional layers through innovative structural design, thereby breaking through the performance bottleneck of "low reflection" and "high absorption," is the core direction for developing high-performance electromagnetic shielding materials and solving the problem of secondary electromagnetic pollution. Such materials have broad application prospects in fields such as electronic device integration, new energy system protection, and electromagnetic compatibility of medical equipment.

[0003] Traditional polymer materials, with their advantages of lightweight, easy processing, and controllable cost, are widely used in packaging, building materials, and daily necessities, bringing convenience to life. However, due to their difficulty in natural degradation, the large amounts of waste generated constitute "white pollution," damaging the ecological environment, threatening the survival of animals and plants, and human health, becoming a global environmental problem that urgently needs to be solved. Against this backdrop, developing biodegradable and environmentally friendly bio-based polymer materials to replace traditional materials has become crucial for alleviating "white pollution" and promoting the green and sustainable development of the materials industry, making its accelerated research and development of significant importance. Among them, polylactic acid (PLA), as a typical representative of bio-based polyesters, has significant advantages: its excellent mechanical strength meets the needs of daily and industrial use, its good biocompatibility is suitable for the medical field, and its excellent transparency and barrier properties make it a potential substitute for petroleum-based plastic products. It is considered one of the most promising bio-based materials. Furthermore, PLA-based electromagnetic shielding composite materials inherit its degradable and environmentally friendly characteristics while also possessing electromagnetic shielding functions, aligning with the "dual-carbon" strategy. They can meet the electromagnetic compatibility requirements of electronic devices and avoid waste pollution, making them a research hotspot in the materials field in recent years, attracting attention from both academia and industry.

[0004] Chinese invention patent CN 119241885 A discloses a thermally conductive electromagnetic shielding multilayer composite film, its preparation method, and its application. This film achieves both electromagnetic shielding and thermal conductivity by sequentially stacking an insulating thermally conductive layer of a cellulose membrane containing thermally conductive fillers, a magnetic shielding layer of a cellulose membrane containing magnetic fillers and expanded microspheres, and a conductive shielding layer of a cellulose membrane containing conductive fillers and expanded microspheres. Chinese invention patent CN115103582 A discloses an asymmetric alternating multilayer electromagnetic interference shielding nanocomposite film and its preparation method. This film achieves ultra-high electromagnetic interference shielding performance through alternating layers of absorbing and reflecting nanofilms of different thicknesses. Chinese invention patent CN 119239095 A discloses a method for preparing a multilayer flexible electromagnetic shielding film. This method uses electroless nickel plating and electroless copper plating to obtain nickel-plated PET fiber fabrics and copper-plated PET fiber fabrics, respectively, to prepare a multilayer flexible electromagnetic shielding film with good mechanical properties and excellent thermal stability. While the methods mentioned in the aforementioned patents have achieved some success in improving the electromagnetic shielding performance of composite materials, they inevitably have some shortcomings, such as insufficient electromagnetic absorption performance, complex preparation processes, and insufficient environmental protection properties. Therefore, developing a multilayer electromagnetic shielding material that can both simply and efficiently improve electromagnetic shielding performance, ensure that electromagnetic absorption performance is the primary focus, and also possess green and environmentally friendly properties has extremely important scientific significance and application value. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing a low-reflection, biodegradable electromagnetic shielding multilayer composite film, addressing the shortcomings of existing technologies. The method is characterized by: loading magnetite nanoparticles onto the surface of conductive carbon nanotubes based on surface chemistry to construct a magnetoelectric hybrid filler; using biodegradable polylactic acid and polycaprolactone as the matrix and toughening phase, inducing the filler to be controllably distributed within the polycaprolactone phase, increasing the local effective concentration; and, through multi-level structural design, constructing an asymmetric multilayer electromagnetic shielding composite film with different impedance matching characteristics. Utilizing the differences in electromagnetic wave impedance coefficients between the absorption and reflection layers and the interlayer impedance mismatch characteristics, and by optimizing the filler composition and processing technology of each layer, a biodegradable nanocomposite film with low reflection, high absorption, excellent electromagnetic shielding performance, and high toughness is obtained, which can be used as an electromagnetic protection material.

[0006] The technical solution of this invention is a method for preparing a low-reflection, biodegradable electromagnetic shielding multilayer composite film, specifically implemented according to the following steps: (1) Preparation of magnetoelectric hybrid fillers; (2) Preparation of composite materials consisting of a conductive layer, a transition layer, and a magnetic absorption layer; and (3) Preparation of asymmetric multilayer electromagnetic shielding composite film.

[0007] Further, step (1) includes: based on surface chemical action, firstly, a certain concentration of carbon nanotube aqueous dispersion is prepared and ultrasonically dispersed evenly. At the same time, a mixed aqueous solution of ferric chloride and ferrous chloride tetrahydrate with a certain pH is prepared and mixed with the carbon nanotube aqueous dispersion. After reacting at a certain temperature for a period of time, the mixture is dried to obtain the magnetoelectric hybrid filler.

[0008] Preferably, in step (1), the carbon nanotubes are one of conductive carbon nanotubes, carboxylated carbon nanotubes, and hydroxylated carbon nanotubes, the concentration of carbon nanotubes is 2~5 mg / mL, the ultrasonic dispersion time is 30~90 min, the ratio of ferric ions to ferrous ions in the mixed aqueous solution of ferric chloride and ferrous chloride tetrahydrate is 1~4:1, the pH is adjusted to 10~13 using sodium hydroxide, the reaction conditions of the mixed solution of ferric chloride and ferrous chloride tetrahydrate with the aqueous dispersion of carbon nanotubes are 65 ℃, and mechanical stirring is performed for 1~2 h, and the post-reaction treatment is to vacuum filter the reaction solution, dry it in an 80 ℃ forced-air oven for 8~10 h, and then grind it into powder to obtain the magnetoelectric hybrid filler.

[0009] Furthermore, in step (2), a certain proportion of conductive filler, antioxidant, polylactic acid and polycaprolactone are dried and then kneaded under certain conditions to obtain a conductive layer composite material. Similarly, a certain proportion of conductive filler, antioxidant, magnetoelectric hybrid filler, polylactic acid and polycaprolactone are dried and then kneaded under certain conditions to obtain a transition layer composite material. A certain proportion of magnetoelectric hybrid filler, antioxidant, polylactic acid and polycaprolactone are dried and then kneaded to obtain a magnetic absorption layer composite material.

[0010] Preferably, in step (2), the conductive filler is one of conductive carbon nanotubes, carboxylated carbon nanotubes, and hydroxylated carbon nanotubes; the antioxidant is one of antioxidant 1010, antioxidant 1076, and antioxidant 245; the drying temperature is 40 ℃, and the drying time is 1~2 h; the ratio of conductive filler, antioxidant, polylactic acid, and polycaprolactone is (1~9):0.1:60:40; the ratio of conductive filler, magnetic filler, antioxidant, polylactic acid, and polycaprolactone is 5:5:0.1:60:40; the ratio of magnetic filler, antioxidant, polylactic acid, and polycaprolactone is (1~9):0.1:60:40; and the mixing temperature is 175 ℃, the mixing speed is 40~60 rpm, and the mixing time is 5~8 min.

[0011] Further, step (3) includes: hot pressing the conductive layer composite material, the transition layer composite material and the magnetic absorption layer composite material under a certain temperature and pressure to obtain a 1mm thick conductive monolayer, intermediate transition monolayer and magnetic absorption monolayer, and then stacking the conductive monolayer, intermediate transition monolayer and magnetic absorption monolayer in sequence, and then composite heating and pressing for a period of time under a certain temperature and pressure to obtain a low-reflection electromagnetic shielding multilayer composite film.

[0012] Preferably, in step (3), the hot pressing temperature is 160~200℃, the hot pressing pressure is 6~15MPa, and the hot pressing time is 5~10 min.

[0013] This invention provides a low-reflection, biodegradable electromagnetic shielding multilayer composite film and its preparation method.

[0014] This invention uses biodegradable polylactic acid and polycaprolactone as the matrix and toughening phase, and carbon nanotubes as the conductive unit. Based on surface chemical interaction, magnetic nanoparticles of iron oxide are loaded on the surface to construct a magnetoelectric bifunctional hybrid filler. It is further melt-blended with the matrix resin to prepare conductive layers, transition layers and magnetic absorption layers with different functions. Subsequently, according to the impedance matching characteristics of different layers, an asymmetric low-reflection biodegradable electromagnetic shielding multilayer composite film is prepared by structural design, fixed-structure processing and hot pressing, which can be used in the field of electromagnetic protection.

[0015] Compared with the prior art, the advantages of the present invention are as follows: 1. Existing technologies mostly use a single conductive or magnetic filler, resulting in a single electromagnetic wave absorption mechanism. This invention loads iron oxide magnetic nanoparticles onto the surface of carbon nanotubes through the interaction between nanoparticles, forming a magnetoelectric hybrid filler. It can simultaneously utilize conductive loss and magnetic loss to synergistically attenuate electromagnetic waves, laying the core foundation for high absorption performance.

[0016] 2. In traditional materials, fillers are prone to agglomeration or uneven distribution, resulting in unstable shielding performance. This invention uses polylactic acid as the matrix and polycaprolactone as the toughening phase. By regulating the distribution of fillers and increasing the local effective concentration, filler waste is avoided, while local electromagnetic loss capacity is enhanced, thus improving the stability and efficiency of shielding performance.

[0017] 3. Most existing mainstream shielding materials are single-layer structures, which are prone to high reflection due to poor impedance matching. This invention constructs an asymmetric multilayer structure with different impedance matching characteristics through structural innovation. It utilizes the impedance mismatch between layers to form an "absorption-reflection-reabsorption" mechanism, which greatly reduces the electromagnetic wave reflectivity and reduces secondary pollution.

[0018] 4. Existing biodegradable shielding materials often suffer from weak mechanical properties (such as high brittleness) and limited functionality. This invention uses biodegradable polylactic acid as the matrix and introduces polycaprolactone as a toughening phase. While achieving low-reflection and high-absorption shielding performance, it significantly improves the strength and toughness of the material. Moreover, the entire material is biodegradable, which aligns with the "dual carbon" strategy and is suitable for scenarios with high requirements for material performance and environmental protection, such as electronics and medical applications.

[0019] 5. Existing technologies cannot simultaneously achieve synergistic optimization of shielding performance, mechanical performance, and environmental friendliness; this invention optimizes the composition of each layer of filler (such as the ratio of magnetoelectric hybrid filler) and processing technology, and can specifically control the absorption and reflection characteristics, mechanical strength, and degradation performance of the material, so as to achieve synergistic unity of multiple properties and meet the customized needs of different application scenarios. Attached Figure Description

[0020] Figure 1 This is a graph showing the Fe content distribution on the brittle fracture surface of a low-reflection electromagnetic shielding multilayer composite film.

[0021] Figure 2 The figures show the electromagnetic shielding effectiveness test results for Examples 1-3.

[0022] Figure 3 The graphs show the test results of electromagnetic absorption coefficient and reflection coefficient for Examples 1-3. Detailed Implementation

[0023] The following specific embodiments and appendices Figure 1-3The present invention will be further described below. It should be noted that the embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Those skilled in the art can make non-essential improvements and adjustments to the present invention based on the above content. Example

[0024] A method for preparing a low-reflection, biodegradable electromagnetic shielding multilayer composite film, comprising the following steps: (1) Preparation of magnetoelectric hybrid filler: First, prepare a 2 mg / mL carbon nanotube aqueous dispersion and ultrasonically disperse it for 10 min. At the same time, prepare a mixed aqueous solution of ferric chloride and ferrous chloride tetrahydrate, wherein the concentration of ferric chloride is 20 mg / mL and the concentration of ferrous chloride tetrahydrate is 20 mg / mL. Then, adjust the pH to 12 with sodium hydroxide. Then, add the mixed solution of ferric chloride and ferrous chloride tetrahydrate to the carbon nanotube aqueous dispersion for full reaction. The reaction conditions are 65 ℃ and mechanical stirring for 1~2 h. Finally, after vacuum filtration, the solution is dried in an 80 ℃ forced-air oven for 8~10 h and then ground into powder to obtain magnetoelectric hybrid filler.

[0025] (2) Preparation of conductive layer, transition layer and magnetic absorption layer composite material: Conductive carbon nanotubes, antioxidant 245, polylactic acid and polycaprolactone were dried in a ratio of 1:0.1:60:40 and then kneaded to obtain conductive shielding composite material. Similarly, conductive carbon nanotubes, magnetoelectric filler, antioxidant 245, polylactic acid and polycaprolactone were dried in a ratio of 5:5:0.1:60:40 and then kneaded to obtain intermediate transition composite material. Magnetoelectric filler, antioxidant 245, polylactic acid and polycaprolactone were dried in a ratio of 9:0.1:60:40 and then kneaded to obtain magnetic shielding composite material. The drying temperature was 40 ℃ for 2 h, the kneading temperature was 175 ℃, the kneading speed was 60 rpm and the kneading time was 5 min. (3) Preparation of asymmetric multilayer electromagnetic shielding composite film: Conductive layer composite material, intermediate transition composite material and magnetic absorption layer composite material were hot-pressed to obtain conductive shielding single layer, intermediate transition single layer and magnetic absorption single layer respectively. The above three layers were then stacked sequentially and hot-pressed at 180 ℃ for 5 min to obtain asymmetric electromagnetic shielding multilayer composite film. The electromagnetic shielding efficiency of the asymmetric multilayer electromagnetic shielding composite film is 39.2 dB, the absorption coefficient is 0.76 and the tensile strength reaches 38.2 MPa. Example

[0026] A method for preparing a low-reflection, biodegradable electromagnetic shielding multilayer composite film, comprising the following steps: (1) Preparation of magnetoelectric hybrid filler: First, prepare a 2 mg / mL carbon nanotube aqueous dispersion and ultrasonically disperse it for 10 min. At the same time, prepare a mixed aqueous solution of ferric chloride and ferrous chloride tetrahydrate, wherein the concentration of ferric chloride is 20 mg / mL and the concentration of ferrous chloride tetrahydrate is 20 mg / mL. Then, adjust the pH to 12 with sodium hydroxide. Then, add the mixed solution of ferric chloride and ferrous chloride tetrahydrate to the carbon nanotube aqueous dispersion for full reaction. The reaction conditions are 65 ℃ and mechanical stirring for 1~2 h. Finally, after vacuum filtration, the solution is dried in an 80 ℃ forced-air oven for 8~10 h and then ground into powder to obtain magnetoelectric hybrid filler.

[0027] (2) Preparation of conductive layer, transition layer and magnetic absorption layer composite material: Conductive carbon nanotubes, antioxidant 245, polylactic acid and polycaprolactone were dried in a ratio of 5:0.1:60:40 and then kneaded to obtain conductive shielding composite material. Similarly, conductive carbon nanotubes, magnetoelectric filler, antioxidant 245, polylactic acid and polycaprolactone were dried in a ratio of 5:5:0.1:60:40 and then kneaded to obtain intermediate transition composite material. Magnetic filler, antioxidant 245, polylactic acid and polycaprolactone were kneaded in a ratio of 5:0.1:60:40 to obtain magnetic absorption composite material. The drying temperature was 40 ℃ for 2 h, the kneading temperature was 175 ℃, the kneading speed was 60 rpm, and the kneading time was 5 min. (3) Preparation of asymmetric multilayer electromagnetic shielding composite film: Conductive composite material, intermediate transition composite material and magnetic absorption composite material were hot-pressed to obtain conductive shielding monolayer, intermediate transition monolayer and magnetic absorption monolayer respectively. The above three layers were then stacked sequentially and hot-pressed at 180 ℃ for 5 min to obtain asymmetric multilayer electromagnetic shielding composite material. The electromagnetic shielding efficiency of the asymmetric multilayer electromagnetic shielding composite film was 41.6 dB, the absorption coefficient was 0.68 and the tensile strength reached 37.3 MPa. Example

[0028] A method for preparing a low-reflection, biodegradable electromagnetic shielding multilayer composite film, comprising the following steps: (1) Preparation of magnetoelectric hybrid filler: First, prepare a 2 mg / mL carbon nanotube aqueous dispersion and ultrasonically disperse it for 10 min. At the same time, prepare a mixed aqueous solution of ferric chloride and ferrous chloride tetrahydrate, wherein the concentration of ferric chloride is 20 mg / mL and the concentration of ferrous chloride tetrahydrate is 20 mg / mL. Then, adjust the pH to 12 with sodium hydroxide. Then, add the mixed solution of ferric chloride and ferrous chloride tetrahydrate to the carbon nanotube aqueous dispersion for full reaction. The reaction conditions are 65 ℃ and mechanical stirring for 1~2 h. Finally, after vacuum filtration, the solution is dried in an 80 ℃ forced-air oven for 8~10 h and then ground into powder to obtain magnetoelectric hybrid filler.

[0029] (2) Preparation of conductive layer, transition layer and magnetic absorption layer composite materials: Conductive carbon nanotubes, antioxidant 245, polylactic acid and polycaprolactone were dried in a ratio of 9:0.1:60:40 and then kneaded to obtain conductive layer composite material. Similarly, conductive carbon nanotubes, magnetic filler, antioxidant 245, polylactic acid and polycaprolactone were dried in a ratio of 5:5:0.1:60:40 and then kneaded to obtain intermediate transition composite material. Magnetic filler, antioxidant 245, polylactic acid and polycaprolactone were kneaded in a ratio of 1:0.1:60:40 to obtain magnetic shielding composite material. The drying temperature was 40 ℃ for 2 h, the kneading temperature was 175 ℃, the kneading speed was 60 rpm, and the kneading time was 5 min. (3) Preparation of asymmetric multilayer electromagnetic shielding composite film: Conductive composite material, intermediate transition composite material and magnetic absorption composite material were hot-pressed to obtain conductive monolayer, intermediate transition monolayer and magnetic absorption monolayer respectively. The above three layers were then stacked sequentially and hot-pressed at 180 ℃ for 5 min to obtain asymmetric multilayer electromagnetic shielding composite material. The electromagnetic shielding efficiency of the asymmetric multilayer electromagnetic shielding composite film is 46.8 dB, the absorption coefficient is 0.62 and the tensile strength reaches 35.8 MPa.

[0030] This invention discloses a method for preparing a low-reflection, biodegradable electromagnetic shielding multilayer composite film. Based on surface chemical interactions, a magnetoelectric hybrid filler of iron(III) oxide@carbon nanotubes (Fe3O4@CNTs) is constructed. Biodegradable polylactic acid (PLA) and polycaprolactone (PVC) are used as the matrix and toughening phase, respectively. The filler is induced to be controllably distributed within the PVC phase, increasing the local effective concentration. Simultaneously, through multi-level structural design, an asymmetric multilayer electromagnetic shielding composite film with different impedance matching characteristics is constructed. Utilizing the differences in electromagnetic wave impedance coefficients between the absorbing and conductive layers and the interlayer impedance mismatch characteristics, and by optimizing the filler composition and processing technology of each layer, a biodegradable nanocomposite film with low reflection, high absorption, excellent electromagnetic shielding performance, and strong toughness is obtained, which can be used in the field of electromagnetic protection. The preparation process of this nanocomposite film is simple and feasible, and has broad practicality and promotional value.

Claims

1. A method for preparing a low-reflection, biodegradable electromagnetic shielding multilayer composite film, characterized in that, The preparation of this composite film mainly includes the following steps: (1) Preparation of magnetoelectric hybrid fillers; (2) Preparation of composite materials consisting of a conductive layer, a transition layer, and a magnetic absorption layer; and (3) Preparation of asymmetric multilayer electromagnetic shielding composite film.

2. The method for preparing a low-reflection, biodegradable electromagnetic shielding multilayer composite film according to claim 1, characterized in that, Step (1) The preparation method of the magnetoelectric hybrid filler includes: based on surface chemical action, firstly, a certain concentration of carbon nanotube aqueous dispersion is prepared and ultrasonically dispersed evenly. At the same time, a mixed aqueous solution of ferric chloride and ferrous chloride tetrahydrate with a certain pH is prepared and mixed with the carbon nanotube aqueous dispersion. After reacting at a certain temperature for a period of time, the mixture is dried to obtain the magnetoelectric hybrid filler.

3. The method for preparing a low-reflection, biodegradable electromagnetic shielding multilayer composite film according to claim 2, characterized in that, In step (1), the preparation method of the magnetoelectric hybrid filler is as follows: the carbon nanotube is one of conductive carbon nanotube, carboxylated carbon nanotube, and hydroxylated carbon nanotube; the concentration of carbon nanotube is 2-5 mg / mL; the ultrasonic dispersion time is 30-90 min; the ratio of ferric ions to ferrous ions in the mixed aqueous solution of ferric chloride and ferrous chloride tetrahydrate is 1-4:1; the pH is adjusted to 10-13 using sodium hydroxide; the reaction conditions of the mixed solution of ferric chloride and ferrous chloride tetrahydrate with the aqueous dispersion of carbon nanotube are 65 ℃, with mechanical stirring for 1-2 h; the post-reaction treatment is to vacuum filter the reaction solution, dry it in an 80 ℃ forced-air oven for 8-10 h, and then grind it into powder to obtain the magnetoelectric hybrid filler.

4. The method for preparing a low-reflection, biodegradable electromagnetic shielding multilayer composite film according to claim 1, characterized in that, The preparation method of the conductive layer, transition layer and magnetic absorption layer in step (2) is as follows: a certain proportion of conductive filler, antioxidant, polylactic acid and polycaprolactone are dried and then mixed under certain conditions to obtain the conductive layer composite material. Similarly, a certain proportion of conductive filler, antioxidant, magnetoelectric hybrid filler, polylactic acid and polycaprolactone are dried and then mixed under certain conditions to obtain the transition layer composite material. A certain proportion of magnetoelectric hybrid filler, antioxidant, polylactic acid and polycaprolactone are dried and then mixed to obtain the magnetic absorption layer composite material.

5. The method for preparing a low-reflection, biodegradable electromagnetic shielding multilayer composite film according to claim 4, characterized in that, The preparation method of the conductive layer, transition layer and magnetic absorption layer in step (2) is as follows: the conductive filler is one of conductive carbon nanotubes, carboxylated carbon nanotubes and hydroxylated carbon nanotubes; the antioxidant is one of antioxidant 1010, antioxidant 1076 and antioxidant 245; the drying temperature is 40 ℃ and the time is 1~2 h; the ratio of conductive filler, antioxidant, polylactic acid and polycaprolactone is 1~9:0.1:60:40; the ratio of conductive filler, magnetic filler, antioxidant, polylactic acid and polycaprolactone is 5:5:0.1:60:40; the ratio of magnetic filler, antioxidant, polylactic acid and polycaprolactone is 1~9: The ratio is 0.1:60:40, the mixing temperature is 175 ℃, the rotation speed is 40~60 rpm, and the time is 5~8 min.

6. The method for preparing a low-reflection, biodegradable electromagnetic shielding multilayer composite film according to claim 1, characterized in that, The preparation method of the asymmetric multilayer electromagnetic shielding composite film in step (3) involves hot-pressing the conductive layer composite material, the transition layer composite material, and the magnetic absorption layer composite material under certain temperature and pressure to obtain a 1mm thick conductive monolayer, intermediate transition monolayer, and magnetic absorption monolayer. Then, the conductive monolayer, intermediate transition monolayer, and magnetic absorption monolayer are stacked sequentially and composite-heat-pressed for a period of time under certain temperature and pressure to obtain a low-reflection electromagnetic shielding multilayer composite film.

7. The method for preparing a low-reflection, biodegradable electromagnetic shielding multilayer composite film according to claim 6, characterized in that, Step (3) Preparation of asymmetric multilayer electromagnetic shielding composite film, wherein the hot pressing temperature is 160~200℃, the hot pressing pressure is 6~15MPa, and the hot pressing time is 5~10 min.

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