A polymer-based multilayer composite film with electromagnetic shielding and heat conduction functions and a preparation method thereof

Abstract

The application relates to the technical field of thin film materials, and discloses a polymer-based multilayer composite film with electromagnetic shielding and heat conduction functions and a preparation method thereof. The preparation method comprises the following steps: S1. dissolving high syndiotactic polyvinyl alcohol in a solvent to obtain a polymer solution; dispersing functional fillers in anhydrous ethanol, adding a polyelectrolyte modifier into the anhydrous ethanol, and obtaining a suspension dispersion; S2. coating the polymer solution on the surface of a substrate and drying to obtain a polymer layer film; S3. coating the suspension dispersion on the surface of the polymer film and drying to obtain a filler layer film; coating the polymer solution on the surface of the filler layer film and drying to obtain a second polymer layer film; and coating the suspension dispersion on the surface of the second polymer layer film and drying to obtain a second filler layer film; and S4. alternately performing steps S2 and S3 to obtain a multilayer composite film with an odd number of layers. The preparation method is simple, the polymer matrix does not need to be modified complicatedly, and the production is easy, low in cost and high in quality.

Description

Technical Field

[0001] This application relates to the field of thin film materials technology, specifically to a polymer-based multilayer composite thin film with electromagnetic shielding and thermal conductivity functions and its preparation method. Background Technology

[0002] With the rapid development of electronic technology, the intelligence and integration of electronic devices have greatly improved. The electromagnetic radiation and heat accumulation generated during operation are becoming increasingly serious, not only interfering with the response of other components but also threatening human health. Currently, maximizing the shielding of electromagnetic interference from electronic products and effectively improving the heat dissipation of components are urgent problems to be solved. Polymers, with their advantages of being lightweight, high-strength, and flexible, are commonly used as matrices for functional composite thin film materials. Compared with traditional metal-based shielding materials, preparing composite thin film materials with excellent electromagnetic shielding and thermal conductivity by combining polymer matrices with functionalized fillers is considered an effective method. However, due to the poor compatibility between traditional conductive and thermally conductive fillers and the polymer matrix, the interfacial forces are weak, resulting in poor electrical and thermal conductivity, ineffective electromagnetic interference shielding, and limited application range. To adapt the polymer matrix to the harsh applications of composite materials, a series of modifications are usually performed to improve interfacial interactions, but the enormous potential of the molecular structure and functional groups in the polymer matrix for expanding the multifunctionality of composite materials is overlooked.

[0003] Recent studies have shown that stereoregularity influences the degree of intramolecular or intermolecular interactions in polymers containing hydrogen bonds. Highly stereoregular polyvinyl alcohol (PVA) exhibits a predominantly isotactic arrangement of hydroxyl groups. This unique hydroxyl structure facilitates intermolecular attraction, enhancing the physical and mechanical properties of the polymer matrix and mitigating the moisture absorption issues of its composites. Therefore, using highly stereoregular PVA holds promise for providing a novel preparation strategy for developing functional composites adapted to complex application environments. Furthermore, by cleverly combining polymers and fillers through structural integration, interfacial anchoring is improved, and the unique structure facilitates the construction of continuous conduction pathways between fillers. This provides excellent conditions for constructing composites with structural stability under complex environments and multiple, highly efficient shielding against electromagnetic interference / heat dissipation.

[0004] Based on this, the development of composite films using high-performance polymer matrices and fillers through sophisticated structural design has a very broad prospect in the field of electronic information. Summary of the Invention

[0005] This application provides a polymer-based multilayer composite film with electromagnetic shielding and thermal conductivity functions and its preparation method, aiming to solve the problem of poor electromagnetic shielding and thermal conductivity of existing polymer-based composite films.

[0006] To achieve the above objectives, the present application adopts the following technical solution.

[0007] A first aspect of this application provides a method for preparing a polymer-based multilayer composite film with electromagnetic shielding and thermal conductivity functions, comprising:

[0008] S1, dissolve hypersyndiotactic polyvinyl alcohol in a solvent to obtain a polymer solution;

[0009] The functional filler was dispersed in anhydrous ethanol to obtain a homogeneous dispersion, and a polyelectrolyte modifier was added to it to obtain a suspension dispersion.

[0010] S2, the polymer solution is coated onto the substrate surface and dried to obtain a polymer layer film;

[0011] S3, the suspension dispersion is coated on the surface of the polymer film and dried to obtain a filler layer film;

[0012] S4, apply the polymer solution to the surface of the filler layer film, dry it to obtain the second polymer layer film; then apply the suspension dispersion to the surface of the second polymer layer film, dry it to obtain the second filler layer film; steps S2 and S3 are performed alternately to obtain a polymer-based multilayer composite film with an odd number of layers.

[0013] In some embodiments, the syndiotactic stereoregularity of the high syndiotactic polyvinyl alcohol is 55-70%, and the degree of alcoholysis is 80-99%.

[0014] In some embodiments, the functional filler is a filler with both electrical and thermal conductivity, including at least one of titanium carbide nanosheets, titanium carbide precipitated powder, carbon black, multi-walled carbon nanotubes, or reduced graphene oxide.

[0015] In some embodiments, the polyelectrolyte modifier includes at least one of polydimethyldiallylammonium chloride, polyethyleneimine, or polyallylamine hydrochloride.

[0016] In some embodiments, the solvent is at least one of water, dimethylformamide, or dimethyl sulfoxide;

[0017] And / or:

[0018] The substrate is any one of iron sheet, glass, aluminum sheet, polystyrene board, acrylic board or polytetrafluoroethylene board.

[0019] In some embodiments, the concentration of the polymer solution is 10.0-50.0 mg / mL.

[0020] In some embodiments, the solid-liquid ratio of the homogeneous dispersion is 1.0-50.0 mg / mL; the mass ratio of the functional filler to the polyelectrolyte modifier is (100-300):1.

[0021] In some embodiments, the drying temperature is 25-80°C.

[0022] In some embodiments, the ratio of the amount of polymer solution used in S2 to the area of ​​the substrate is 0.003125-0.125 mL / cm². 2 ;

[0023] The ratio of the amount of suspension / dispersion used in S3 to the area of ​​the polymer film is 0.003125-0.125 mL / cm². 2 .

[0024] The polymer-based multilayer composite film with electromagnetic shielding and thermal conductivity functions has 3-15 layers.

[0025] A second aspect of this application provides a polymer-based multilayer composite film with electromagnetic shielding and thermal conductivity functions prepared by the above-described preparation method.

[0026] Compared with the prior art, the beneficial effects of this application are as follows:

[0027] The polymer-based multilayer composite film preparation method of this application is simple, requiring no cumbersome modification of the polymer matrix, and is easy to produce at low cost and with high quality. The high-syndiotactic polyvinyl alcohol, with its abundant hydroxyl structure and easily formed intramolecular hydrogen bonds, enhances the internal interaction forces of the polymer matrix, giving it high strength and good water resistance. The polyelectrolyte modifier promotes the bonding between functional fillers, contributing to the formation of a layered structure, further improving the stability of the composite film, and endowing the composite film with excellent electrical and thermal conductivity, giving it excellent electromagnetic shielding and heat dissipation functions.

[0028] This application utilizes a clever structural composite of high-meta-diurnal polyvinyl alcohol and functional fillers. This enhances the interfacial anchoring effect and facilitates the construction of continuous conduction paths between the functional fillers, resulting in a composite film with excellent structural stability in complex environments, multi-layered and highly efficient electromagnetic interference shielding, and good heat dissipation. Furthermore, the electromagnetic interference shielding and heat dissipation characteristics of this functional polymer-based composite film can be controlled through the design of the multilayer structure, demonstrating broad application prospects in the field of electronic information. Attached Figure Description

[0029] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This is a schematic diagram of the structure of the composite film prepared in Example 1;

[0031] Figure 2 The image shows the zeta potential curves of titanium carbide nanosheets (MXene) in Example 1 before and after modification with polyelectrolyte polyethyleneimine (PEI).

[0032] Figure 3 The image shows the SEM image of the composite film prepared in Example 2.

[0033] Figure 4 Tensile stress-strain curves of the composite film prepared in Example 3 and the pure sPVA film of the comparative example.

[0034] Figure 5 The graph shows the electromagnetic shielding test results of the composite films prepared in Examples 2-4;

[0035] Figure 6 The graph shows the thermal conductivity test results of the composite films prepared in Examples 2-4. Detailed Implementation

[0036] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0037] In the following description of this embodiment, the terms "including", "comprising", "having", and "containing" are all open-ended terms, meaning that they include but are not limited to.

[0038] In the following description of this embodiment, the term "and / or" is used to describe the association relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, B existing alone, and A and B existing simultaneously. A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0039] In the following description of this embodiment, the term "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0040] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms "a" and "the" as used in the embodiments of this application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0041] Those skilled in the art should understand that, in the following description of the embodiments of this application, the sequence of numbers does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0042] Those skilled in the art will understand that the numerical ranges in the embodiments of this application should be understood as each intermediate value between the upper and lower limits of the specifically disclosed range. Each smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this application. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0043] Unless otherwise stated, the technical / scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. While this application describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this application. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0044] In a first aspect, this application provides a method for preparing a polymer-based multilayer composite film with electromagnetic shielding and thermal conductivity functions, comprising:

[0045] S1, dissolve hypersyndiotactic polyvinyl alcohol in a solvent to obtain a polymer solution;

[0046] The functional filler was dispersed in anhydrous ethanol to obtain a homogeneous dispersion, and a polyelectrolyte modifier was added to it to obtain a suspension dispersion.

[0047] This application uses high-regularity polyvinyl alcohol (PVA) as a matrix, overcoming the shortcomings of commonly used matrices with weak interfacial interactions under complex conditions, and improving the physical and mechanical properties of the film composite material. The high-syndiotactic polyvinyl alcohol selected in this application, with its abundant hydroxyl structure and easily formed intramolecular hydrogen bonds, enhances the internal interaction forces of the polymer matrix, giving it high strength and good water resistance. Preferably, the high-syndiotactic polyvinyl alcohol has a syndiotactic regularity of 55-70% and a degree of alcoholysis of 80-99%; the solvent is at least one of water, dimethylformamide, or dimethyl sulfoxide; the solvent is preferably dimethyl sulfoxide. The high-syndiotactic polyvinyl alcohol is dissolved in the solvent to prepare a polymer solution with a concentration of 10.0-50.0 mg / mL for later use.

[0048] In this application, the functional filler is a filler with both electrical and thermal conductivity, including at least one of titanium carbide nanosheets, titanium carbide powder, carbon black, multi-walled carbon nanotubes, or reduced graphene oxide. The functional filler is dispersed in anhydrous ethanol to prepare a homogeneous dispersion.

[0049] In this application, by adding a polyelectrolyte modifier to a homogeneous dispersion, the potential of the filler is changed, promoting electrostatic interaction between the fillers and facilitating the construction of the filler layer. The polyelectrolyte modifier includes at least one of polydimethyldiallylammonium chloride, polyethyleneimine, or polyallylamine hydrochloride. Preferably, the solid-liquid ratio of the homogeneous dispersion is 1.0-50.0 mg / mL; preferably, the mass ratio of the functional filler to the polyelectrolyte modifier is (100-300):1.

[0050] In this application, the polyelectrolyte modifier promotes the bonding between functional fillers, which helps to form a layered structure, further improves the stability of the composite film, and endows the composite film with excellent electrical and thermal conductivity, giving it excellent electromagnetic shielding and heat dissipation functions.

[0051] S2, the polymer solution is coated onto the substrate surface and dried to obtain a polymer layer film;

[0052] The substrate is any one of iron sheet, glass, aluminum sheet, polystyrene board, acrylic board or polytetrafluoroethylene board.

[0053] The preferred ratio of polymer solution volume to substrate coating area is 0.003125-0.125 mL / cm². 2 In this embodiment, the coating area of ​​the substrate is 16 cm². 2 The amount of polymer solution used is 0.05-2.0 mL.

[0054] The substrate coated with the polymer solution is dried to form a polymer film, preferably at a drying temperature of 25-80°C.

[0055] S3, the suspension dispersion is coated on the surface of the polymer film and dried to obtain a filler layer film;

[0056] The preferred ratio of the amount of suspension dispersion to the coating area of ​​the polymer film is 0.003125-0.125 mL / cm². 2 In this embodiment, the coating area of ​​the polymer film is 16 cm². 2 The amount of suspension / dispersion used is 0.05-2.0 mL.

[0057] The polymer film coated with the suspension dispersion is dried to form a filler layer film, preferably at a drying temperature of 25-80℃.

[0058] S4, Steps S2 and S3 are performed alternately on the surface of the filler layer film to obtain a polymer-based multilayer composite film with an odd number of layers.

[0059] In this application, the polymer-based multilayer composite film has an odd number of layers, with its upper and lower surface layers being highly syndiotactic polyvinyl alcohol layers, and a conductive and thermally conductive filler layer located between the upper and lower surface layers. Preferably, the polymer-based multilayer composite film has 3-15 layers, such as 3, 5, 7, 9, 11, 13, or 15 layers.

[0060] The polymer-based multilayer composite film preparation method of this application is simple, requiring no cumbersome modification of the polymer matrix, and is easy to mass-produce at low cost. Through the ingenious structural composite of highly syndiotactic polyvinyl alcohol and functional fillers, the interfacial anchoring effect is improved, and the unique structure facilitates the construction of continuous conduction paths between the functional fillers, thereby constructing a composite film with good structural stability in complex environments and multiple, highly efficient electromagnetic interference shielding and heat dissipation. Furthermore, the electromagnetic interference shielding and heat dissipation characteristics of the functional polymer-based composite film can be controlled by designing the multilayer structure.

[0061] Secondly, this application discloses a polymer-based multilayer composite film with electromagnetic shielding and thermal conductivity functions. Its structure consists of alternating layers of highly syndiotactic polyvinyl alcohol (PVA) and conductive and thermally conductive fillers, with an odd number of layers. Both the upper and lower surfaces are composed of highly syndiotactic PVA layers. This polymer-based multilayer composite film exhibits good structural stability under complex environments, effectively shields electromagnetic interference, and provides excellent heat dissipation. By adjusting the number of layers in the multilayer structure, its electromagnetic interference shielding and heat dissipation characteristics can be controlled, making it a promising candidate for applications in the field of electronic information.

[0062] The present application will be further illustrated by the following examples.

[0063] In the embodiments of this application, the selected high syndiotactic polyvinyl alcohol (sPVA) has a syndiotactic regularity of 65-70% and a degree of alcoholysis of 90-99%.

[0064] Example 1

[0065] This embodiment provides a method for preparing a polymer-based multilayer composite film with electromagnetic shielding and thermal conductivity functions, including the following steps:

[0066] S1, Weigh 4.8g of high syndiotactic polyvinyl alcohol (sPVA) and dissolve it in 90mL of N,N-dimethylformamide (DMF) at 80℃. After it is completely dissolved, an sPVA solution is obtained.

[0067] Weigh 0.045 g of titanium carbide nanosheets (MXene) and place them in 4.50 mL of anhydrous ethanol for ultrasonic dispersion to obtain a homogeneous dispersion; add 0.015 mL of polyethyleneimine to the homogeneous dispersion and dissolve it by ultrasonication to obtain a suspension dispersion.

[0068] S2, 2.00 mL of sPVA solution was coated onto a flat glass slide using a casting method, and dried at 50 °C to obtain an sPVA film; the area of ​​the glass slide was 16 cm². 2 .

[0069] S3, take 1.50 mL of suspension dispersion and coat it on the surface of sPVA layer film, and dry it at 50℃ to obtain titanium carbide nanosheet film;

[0070] S4. Steps S2 and S3 are performed alternately on the surface of the titanium carbide nanosheet film to prepare a composite film with 7 layers.

[0071] The composite film prepared in Example 1 has the following structural schematic diagram. Figure 1 As shown.

[0072] Example 2

[0073] This embodiment provides a method for preparing a polymer-based multilayer composite film with electromagnetic shielding and thermal conductivity functions, including the following steps:

[0074] S1, Weigh 2.5g of high syndiotactic polyvinyl alcohol (sPVA) and dissolve it in 100mL of N,N-dimethylformamide (DMF) at 90℃. After it is completely dissolved, an sPVA solution is obtained.

[0075] Weigh 0.1 g of titanium carbide powder and place it in 5.00 mL of anhydrous ethanol and disperse it by ultrasonication to obtain a homogeneous dispersion; add 0.01 mL of polydimethyldiallyl ammonium chloride to the homogeneous dispersion and dissolve it by ultrasonication to obtain a suspension dispersion.

[0076] S2, 1.50 mL of sPVA solution was coated onto a flat aluminum sheet surface using a casting method, and dried at 60°C to obtain an sPVA film; the area of ​​the aluminum sheet was 16 cm². 2 .

[0077] S3, take 1.00 mL of suspension dispersion and coat it on the surface of the sPVA layer film, and dry it at 60℃ to obtain a titanium carbide powder layer film;

[0078] S4, Steps S2 and S3 are performed alternately on the surface of the titanium carbide powder film to prepare a composite film with 9 layers.

[0079] Example 3

[0080] This embodiment provides a method for preparing a polymer-based multilayer composite film with electromagnetic shielding and thermal conductivity functions, including the following steps:

[0081] S1, Weigh 2.0g of high syndiotactic polyvinyl alcohol (sPVA) and dissolve it in 75mL of N,N-dimethylformamide (DMF) at 25℃. After it is completely dissolved, an sPVA solution is obtained.

[0082] Weigh 0.35g of carbon black and place it in 14.00mL of anhydrous ethanol and disperse it by ultrasonication to obtain a homogeneous dispersion; add 0.02mL of polydimethyldiallyl ammonium chloride to the homogeneous dispersion and dissolve it by ultrasonication to obtain a suspension dispersion.

[0083] S2, 0.75 mL of sPVA solution was coated onto a flat polytetrafluoroethylene (PTFE) sheet surface using a casting method, and dried at 80 °C to obtain an sPVA film; wherein the area of ​​the PTFE sheet was 16 cm². 2 .

[0084] S3, take 2.00 mL of suspension dispersion and coat it on the surface of sPVA film, then dry it at 50 °C to obtain carbon black film;

[0085] S4, Steps S2 and S3 are performed alternately on the surface of the carbon black film to prepare a composite film with 15 layers.

[0086] Example 4

[0087] This embodiment provides a method for preparing a polymer-based multilayer composite film with electromagnetic shielding and thermal conductivity functions, including the following steps:

[0088] S1, Weigh 3.2g of high syndiotactic polyvinyl alcohol (sPVA) and dissolve it in 80mL of water at 60℃. After it is completely dissolved, an sPVA solution is obtained.

[0089] Weigh 0.24 g of reduced graphene oxide and disperse it in 15.00 mL of anhydrous ethanol by ultrasonication to obtain a homogeneous dispersion; add 0.02 mL of polyallylamine hydrochloride to the homogeneous dispersion and dissolve it by ultrasonication to obtain a suspension dispersion.

[0090] S2, 1.00 mL of sPVA solution was coated onto a flat polystyrene board surface using a casting method, and dried at 60°C to obtain an sPVA film; the area of ​​the polystyrene board was 16 cm². 2 .

[0091] S3, 1.20 mL of suspension dispersion was coated onto the surface of the sPVA layer film and dried at 50 °C to obtain a reduced graphene oxide layer film;

[0092] S4. Steps S2 and S3 are performed alternately on the surface of the reduced graphene oxide film to prepare a composite film with 9 layers.

[0093] Example 5

[0094] This embodiment provides a method for preparing a polymer-based multilayer composite film with electromagnetic shielding and thermal conductivity functions, including the following steps:

[0095] S1, Weigh 3.6g of high syndiotactic polyvinyl alcohol (sPVA) and dissolve it in 80mL of N,N-dimethylformamide (DMF) at 50℃. After it is completely dissolved, an sPVA solution is obtained.

[0096] Weigh 0.60 g of multi-walled carbon nanotubes and disperse them in 20.00 mL of anhydrous ethanol by ultrasonication to obtain a homogeneous dispersion; add 0.04 mL of polyethyleneimine to the homogeneous dispersion and dissolve it by ultrasonication to obtain a suspension dispersion.

[0097] S2, 1.20 mL of sPVA solution was coated onto a flat polytetrafluoroethylene (PTFE) sheet surface using a casting method, and dried at 70 °C to obtain an sPVA film; wherein the area of ​​the PTFE sheet was 16 cm². 2 .

[0098] S3, take 1.50 mL of suspension dispersion and coat it on the surface of sPVA layer film, and dry it at 50℃ to obtain multi-walled carbon nanotube layer film;

[0099] S4. Steps S2 and S3 are performed alternately on the surface of the multi-walled carbon nanotube thin film to prepare a composite film with 5 layers.

[0100] Comparative Example

[0101] Pure sPVA film without filler layer.

[0102] Zeta potential tests were performed on the titanium carbide nanosheets (MXene) from Example 1 before and after modification with the polyelectrolyte polyethyleneimine (PEI). The results are as follows: Figure 2 As shown.

[0103] from Figure 2 It is known that the positive ions (H+) present on PEI neutralize the negative charges on the surface of titanium carbide nanosheets (MXene), causing the Zeta potential of the modified titanium carbide nanosheets (mMXene) to shift towards a positive potential. The polyelectrolyte PEI can not only insert into the interlayer gaps of MXene particles under the influence of molecular chain motion, thus functionalizing their surface and inducing the formation of dense thin layers of mMXene particles, but also provide conditions for assembling layered composite films under electrostatic interactions.

[0104] The composite film prepared in Example 2, using high-syndiotactic polyvinyl alcohol (sPVA) as the polymer matrix and MXene sediment modified with polyelectrolyte polydiallyl ammonium chloride (PDDA) as the filler, was subjected to SEM testing. The results are as follows: Figure 3 As shown. From Figure 3 It can be seen that the composite film prepared in Example 2 exhibits a clear, continuous, alternating layer-by-layer structure of sPVA layer and MXene sediment layer.

[0105] The composite film prepared in Example 3 using hypersyndiotactic polyvinyl alcohol (sPVA) as the polymer matrix and polydimethyldiallyl ammonium chloride (PDDA) modified carbon black as the filler was compared with the pure sPVA film in the comparative example for mechanical property testing. Their tensile stress-strain curves are shown in the figure below. Figure 4 As shown. From Figure 4 It can be seen that the composite film prepared in Example 3 has significantly improved physical and mechanical properties compared with the pure sPVA film in the comparative example. This is mainly because the selected sPVA polymer has a regular spatial arrangement structure, which is conducive to promoting intramolecular interactions. At the same time, the modified carbon black filler helps to entangle the sPVA and PDDA molecular chains more tightly under hydrogen bonding and electrostatic interaction, thus forming a strong and stable structure.

[0106] The composite films prepared in Examples 2-4 were subjected to electromagnetic shielding and thermal conductivity tests to characterize their electromagnetic shielding and thermal conductivity performance.

[0107] The electromagnetic shielding test covered an electromagnetic wave frequency range of 8.2–12.4 GHz, and the test results are as follows: Figure 5 As shown.

[0108] Depend on Figure 5It can be seen that the composite films prepared in Examples 2-4 all have electromagnetic shielding effects. Among them, the multilayer composite film prepared in Example 5, using high syndiotactic polyvinyl alcohol (sPVA) as the polymer matrix and polyethyleneimine (PEI) modified multi-walled carbon nanotubes as fillers, exhibits high EMI SE in the entire X-band, reaching a maximum of 15.8 dB. In contrast, the multilayer composite film prepared in Example 3, using high syndiotactic polyvinyl alcohol (sPVA) as the polymer matrix and polydimethyldiallylammonium chloride modified carbon black as fillers, also exhibits high EMI SE in the entire X-band, reaching a maximum of 14.2 dB. This demonstrates that the multilayer structure and excellent conductive layer endow the multilayer film with multiple reflections and absorption of electromagnetic waves, achieving a good anti-interference effect.

[0109] The test results of thermal conductivity are as follows Figure 6 As shown. From Figure 6 It can be seen that the composite films prepared in Examples 2-4 all have high thermal conductivity. Among them, the multilayer composite film prepared in Example 5, using high syndiotactic polyvinyl alcohol (sPVA) as polymer matrix and polyethyleneimine (PEI) modified multi-walled carbon nanotubes as filler, has an in-plane thermal conductivity of 3.31 W / mK, demonstrating efficient heat dissipation capability.

[0110] Although this application has been described in detail in this specification with general descriptions and specific embodiments, some modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, such modifications or improvements made without departing from the spirit of this application are all within the scope of protection claimed in this application.

Claims

1. A method for preparing a polymer-based multilayer composite film with electromagnetic shielding and thermal conductivity functions, characterized in that, include: S1, dissolve hypersyndiotactic polyvinyl alcohol in a solvent to obtain a polymer solution; The functional filler was dispersed in anhydrous ethanol to obtain a homogeneous dispersion, and a polyelectrolyte modifier was added to it to obtain a suspension dispersion. The functional filler is a filler with both electrical and thermal conductivity properties, including at least one of titanium carbide nanosheets, titanium carbide precipitated powder, carbon black, multi-walled carbon nanotubes, or reduced graphene oxide. The syndiotactic stereoregularity of the high syndiotactic polyvinyl alcohol is 55-70%, and the degree of alcoholysis is 80-99%. S2, the polymer solution is coated onto the substrate surface and dried to obtain a polymer layer film; S3, the suspension dispersion is coated on the surface of the polymer layer film and dried to obtain the filler layer film; S4, apply the polymer solution to the surface of the filler layer film, and dry it to obtain the second polymer layer film; A suspension dispersion is then coated onto the surface of the second polymer layer film and dried to obtain the second filler layer film; steps S2 and S3 are performed alternately to obtain a polymer-based multilayer composite film with an odd number of layers.

2. The method for preparing polymer-based multilayer composite films according to claim 1, characterized in that, The polyelectrolyte modifier includes at least one of polydimethyldiallylammonium chloride, polyethyleneimine, or polyallylamine hydrochloride.

3. The method for preparing polymer-based multilayer composite films according to claim 1, characterized in that, The solvent is at least one of water, dimethylformamide, or dimethyl sulfoxide; And / or: The substrate is any one of iron sheet, glass, aluminum sheet, polystyrene board, acrylic board or polytetrafluoroethylene board.

4. The method for preparing polymer-based multilayer composite films according to claim 1, characterized in that, The concentration of the polymer solution is 10.0-50.0 mg / mL.

5. The method for preparing a polymer-based multilayer composite film according to claim 1, characterized in that, The solid-liquid ratio of the homogeneous dispersion is 1.0-50.0 mg / mL; the mass ratio of the functional filler to the polyelectrolyte modifier is (100-300):

1.

6. The method for preparing a polymer-based multilayer composite film according to claim 1, characterized in that, The drying temperature is 25-80℃.

7. The method for preparing a polymer-based multilayer composite film according to claim 1, characterized in that, The ratio of the amount of polymer solution used in S2 to the area of ​​the substrate is 0.003125-0.125 mL / cm². 2 ; The ratio of the amount of suspension / dispersion used in S3 to the area of ​​the polymer film is 0.003125-0.125 mL / cm². 2 ; The polymer-based multilayer composite film with electromagnetic shielding and thermal conductivity functions has an odd number of layers, ranging from 5 to 15.

8. A polymer-based multilayer composite film with electromagnetic shielding and thermal conductivity prepared by the preparation method according to any one of claims 1-7.

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