A metal-based polyvinylidene fluoride / conductive carbon powder / charring polyimide composite material, a preparation method and application thereof

Abstract

The application discloses a metal-based polyvinylidene fluoride / conductive carbon powder / carbonized polyimide composite material and a preparation method and application thereof. The method comprises the following steps: firstly, modifying a metal mesh by using a polyamide acid sol; then, performing thermal imidization and carbonization treatment under an argon atmosphere to obtain a metal mesh loaded with carbonized polyimide; placing the metal mesh loaded with carbonized polyimide in a polyvinylidene fluoride / conductive carbon powder composite sol, and performing ultrasonic treatment and drying to obtain a polyvinylidene fluoride / conductive carbon powder / carbonized polyimide modified metal mesh; and alternately stacking the polyvinylidene fluoride / conductive carbon powder / carbonized polyimide modified metal mesh and a polyvinylidene fluoride / conductive carbon powder composite film, and then performing hot pressing to obtain the metal-based polyvinylidene fluoride / conductive carbon powder / carbonized polyimide composite material. The composite material prepared by the application is mainly absorption, and the secondary pollution caused by reflection is greatly reduced. Meanwhile, the composite material has low preparation cost, good flexibility and potential great application value.

Description

Technical Field

[0001] This invention belongs to the field of electromagnetic shielding composite material development technology, and relates to a metal-based polyvinylidene fluoride / conductive carbon powder / carbonized polyimide composite material, its preparation method and application. Background Technology

[0002] With the widespread use of electronic devices, electromagnetic radiation constantly and adversely affects human health and the environment, making the development of high-performance electromagnetic shielding materials particularly important. Metals and their alloys are traditional electromagnetic shielding materials, widely used in various fields. While they achieve good shielding effects, their high density, poor corrosion resistance, poor processing performance, and the fact that their primary shielding mechanism is reflection, which can cause secondary pollution, limit their application in the electromagnetic shielding material field. Polymer composite electromagnetic shielding materials have become a research hotspot due to their advantages such as lightweight, good chemical stability, ease of processing and molding, and adjustable electromagnetic shielding effectiveness. However, polymers are generally non-conductive, requiring the addition of conductive fillers to impart conductivity. Carbon fillers often possess properties such as high specific surface area, good conductivity, low density, and good chemical stability, and are frequently used to composite with polymers to prepare polymer conductive composite electromagnetic shielding materials. However, polymer conductive composite materials typically require the addition of large amounts of conductive fillers to achieve sufficient shielding effects, which not only increases manufacturing costs but also reduces the mechanical properties of the electromagnetic shielding material. Summary of the Invention

[0003] To address the problems existing in the prior art, this invention provides a metal-based polyvinylidene fluoride / conductive carbon powder / carbonized polyimide composite material, its preparation method, and its application. This solves the technical problems in the prior art where traditional metal and alloy materials, although inexpensive, mainly reflect electromagnetic waves, easily causing secondary pollution, and polymer composite electromagnetic shielding materials have high requirements for conductive fillers, high preparation costs, and can lead to a decline in the mechanical properties of composite materials.

[0004] This invention is achieved through the following technical solution:

[0005] A method for preparing a metal-based polyvinylidene fluoride / conductive carbon powder / carbonized polyimide composite material includes the following steps:

[0006] S1: The metal mesh is placed in polyamic acid sol, ultrasonically treated, and then dried to obtain a metal mesh loaded with polyamic acid;

[0007] S2: The metal mesh loaded with polyamic acid is subjected to thermal imidization and carbonization under an argon atmosphere to obtain a metal mesh loaded with carbonized polyimide.

[0008] S3: The metal mesh loaded with carbonized polyimide is placed in a composite sol of polyvinylidene fluoride / conductive carbon powder, and after ultrasonic treatment and drying, a polyvinylidene fluoride / conductive carbon powder / carbonized polyimide modified metal mesh is obtained.

[0009] S4: The polyvinylidene fluoride / conductive carbon powder / carbonized polyimide modified metal mesh and polyvinylidene fluoride / conductive carbon powder composite film are alternately stacked and then hot-pressed to obtain the metal-based polyvinylidene fluoride / conductive carbon powder / carbonized polyimide composite material.

[0010] Preferably, the metal mesh is pretreated before being ultrasonically treated in polyamic acid sol. The pretreatment process involves polishing the metal mesh, cleaning it with ethanol, and finally immersing it in N,N-dimethylformamide and then drying it.

[0011] Preferably, the metal mesh is at least one of copper mesh and nickel mesh.

[0012] Preferably, the mass concentration of the polyamic acid sol is 15-18 wt%.

[0013] Preferably, in step S1, the ultrasonic treatment lasts for 10 to 15 minutes.

[0014] Preferably, in step S2, the temperature of the thermal imidization treatment is 350℃~450℃, and the temperature of the carbonization treatment is 600~800℃.

[0015] Preferably, in the polyvinylidene fluoride / conductive carbon powder composite sol, the conductive carbon powder is at least one of Ketjen black, graphene, and acetylene black; and the mass concentration of the conductive carbon powder in the polyvinylidene fluoride / conductive carbon powder composite sol is 10-20 wt%.

[0016] Preferably, in step S4, during the hot pressing process, the hot pressing temperature is 180-200℃, the pressure is 15-20 MPa, and the time is 25-35 min.

[0017] A method for preparing a metal-based polyvinylidene fluoride / conductive carbon powder / carbonized polyimide composite material, which is obtained by the above method.

[0018] The above-mentioned method for preparing a metal-based polyvinylidene fluoride / conductive carbon powder / carbonized polyimide composite material is applied in the field of electromagnetic shielding.

[0019] Compared with the prior art, the present invention has the following beneficial technical effects:

[0020] This invention discloses a method for preparing a metal-based polyvinylidene fluoride (PVDF) / conductive toner / carbonized polyimide composite material. The method uses a metal mesh as a substrate. First, carbonized polyimide is loaded onto its surface. This carbonized polyimide has good electromagnetic wave absorption properties. Then, a PVDF / conductive toner composite sol is further loaded onto the metal mesh loaded with carbonized polyimide. This results in good affinity between the substrate and the PVDF / conductive toner composite film during alternating hot-pressing, leading to a tighter bond between the materials. The PVDF / conductive toner / carbonized polyimide modified metal mesh and the PVDF / conductive toner composite film are then alternately stacked, with the PVDF / conductive toner composite film placed as the outermost layer. When electromagnetic waves are incident on the composite material, a portion is reflected off the surface of the PVDF / conductive toner film due to impedance mismatch between the air and the PVDF / conductive toner film on the outer surface of the composite material. Electromagnetic waves incident on the polyvinylidene fluoride / conductive carbon film are partially absorbed by the conductive carbon powder, and then partially absorbed by the carbonized polyimide on the surface of the metal mesh. When the electromagnetic waves reach the surface of the metal mesh, the metal mesh strongly reflects them, and the reflected electromagnetic waves are then absorbed by the upper carbonized polyimide. The electromagnetic waves that pass through the metal mesh are then absorbed by the lower carbonized polyimide. This multi-layered structure, with its multiple reflections and absorptions, as well as the interfacial polarization at different interfaces of the composite material, greatly attenuates the electromagnetic waves. Ultimately, only a very small portion of the electromagnetic waves can pass through the composite material. The composite material prepared by this invention achieves an overall electromagnetic shielding effectiveness of 90dB in the frequency range of 8.2–12.4 GHz, with a maximum of 110dB, capable of shielding more than 99.9999999% of electromagnetic waves. The shielding mechanism is mainly absorption-based, significantly reducing secondary pollution caused by reflection. At the same time, this composite material has low manufacturing cost, good flexibility, and can withstand bending and folding without damage, showing great potential application value.

[0021] Furthermore, before ultrasonic treatment in polyamic acid sol, the metal mesh is pretreated. The pretreatment process involves polishing the metal mesh, cleaning it with ethanol, and finally immersing it in N,N-dimethylformamide and then drying it. This pretreatment process increases the surface roughness of the metal mesh, which is more conducive to the adhesion of the sol to the surface of the metal mesh.

[0022] Furthermore, the metal mesh is at least one of copper mesh and nickel mesh, which can effectively control the material synthesis cost.

[0023] Furthermore, the polyamic acid sol has a mass concentration of 15-18 wt%, which allows the polyamic acid sol to have a moderate viscosity and better adhere to the surface of the metal mesh.

[0024] Furthermore, in step S1, ultrasonic treatment for 10-15 minutes allows the polyamic acid sol to come into close contact with the metal mesh, increasing the adhesion of the polyamic acid.

[0025] Furthermore, in step S2, the temperature of the thermal imidization treatment is 350℃~450℃, which can convert polyamic acid into polyimide.

[0026] Furthermore, in the polyvinylidene fluoride / conductive carbon powder composite sol, the mass concentration of conductive carbon powder is 10-20 wt%, which makes the viscosity of the polyvinylidene fluoride / conductive carbon powder composite sol moderate. If the viscosity of the polyvinylidene fluoride / conductive carbon powder sol is too low, it will be impossible to scrape a film or the thickness of the scraped film will not reach the ideal thickness. If the viscosity of the polyvinylidene fluoride / conductive carbon powder sol is too high, it will be difficult to scrape a uniform film, and it will also increase the preparation cost.

[0027] Furthermore, during the hot pressing process, the hot pressing temperature is 180-200℃, the pressure is 15-20 MPa, and the time is 25-35 minutes, which allows the various parts of the composite material to come into full contact and the components to form a whole, reducing the risk of material detachment. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a schematic flowchart of a method for preparing a metal-based polyvinylidene fluoride / conductive carbon powder / carbonized polyimide composite material according to the present invention.

[0030] Figure 2 This is a photograph of the copper-based polyvinylidene fluoride / Ketjen black / carbonized polyimide composite material prepared in Example 1 of the present invention.

[0031] Figure 3 The graph shows the electromagnetic shielding effectiveness of the copper-based polyvinylidene fluoride / Kejtien black / carbonized polyimide composite material prepared in Example 1 of this invention as a function of frequency.

[0032] Figure 4 The graph shows the electromagnetic shielding efficiency of the nickel-based polyvinylidene fluoride / Kejtien black / carbonized polyimide composite material prepared in Example 6 of this invention as a function of frequency. Detailed Implementation

[0033] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0034] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0035] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0036] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0037] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0038] like Figure 1 As shown, this invention provides a method for preparing a metal-based polyvinylidene fluoride / conductive carbon powder / carbonized polyimide composite material, comprising the following steps:

[0039] S1: After ultrasonic treatment in polyamic acid sol for 10-15 minutes, the metal mesh is dried in a precision high-temperature drying oven for 5-6 hours to obtain a metal mesh loaded with polyamic acid. In this step, the metal mesh is pretreated before ultrasonic treatment in the polyamic acid sol. The pretreatment process involves polishing the metal mesh, cleaning it with ethanol, and finally immersing it in N,N-dimethylformamide and air-drying it to complete the pretreatment process. The metal mesh is at least one of copper mesh and nickel mesh.

[0040] The preparation process of the polyamic acid sol involves dissolving 4,4'-diaminodiphenyl ether in N,N-dimethylformamide, sonicating for 5–10 min to obtain a diamine dispersion, then adding pyromellitic dianhydride in four portions to the diamine dispersion, and stirring under shear force for 2–3 h to obtain the polyamic acid sol. The mass concentration of the polyamic acid sol is 15–18 wt%, i.e., the solid content of the polyamic acid sol is 15–18 wt%.

[0041] S2: The metal mesh loaded with polyamic acid is subjected to thermal imidization and carbonization treatment under an argon atmosphere to obtain a metal mesh loaded with carbonized polyimide; wherein the temperature of thermal imidization treatment is 350℃~450℃, and the temperature of carbonization treatment is 600~800℃.

[0042] S3: The metal mesh loaded with carbonized polyimide is placed in a polyvinylidene fluoride / conductive carbon powder composite sol, ultrasonically treated and dried to obtain a polyvinylidene fluoride / conductive carbon powder / carbonized polyimide modified metal mesh; wherein, the specific preparation process of the polyvinylidene fluoride / conductive carbon powder composite sol is as follows: polyvinylidene fluoride is added to N,N-dimethylformamide, wherein the ratio of polyvinylidene fluoride to N,N-dimethylformamide is 1g:(8-10)mL, magnetically stirred for 12h, then conductive carbon powder is added and magnetically stirred until fully dissolved, and finally emulsification treatment is performed for 5-6h to obtain the polyvinylidene fluoride / conductive carbon powder composite sol. In the polyvinylidene fluoride / conductive carbon powder composite sol, the content of conductive carbon powder is 10-20wt%. The conductive carbon powder can be at least one of Ketjen black, graphene and acetylene black.

[0043] S4: The polyvinylidene fluoride / conductive carbon powder / carbonized polyimide modified metal mesh and polyvinylidene fluoride / conductive carbon powder composite film are alternately stacked and then hot-pressed to obtain a metal-based polyvinylidene fluoride / conductive carbon powder / carbonized polyimide composite material. During the hot-pressing process, the hot-pressing temperature is 180–200℃, the pressure is 15–20 MPa, and the time is 25–35 min. The preparation process of the polyvinylidene fluoride / conductive carbon powder composite film involves coating a polyvinylidene fluoride / conductive carbon powder composite sol onto a clean glass substrate to form a wet film with a thickness of 15±2 μm, and then drying it at 100℃ for 10–12 h to obtain the polyvinylidene fluoride / conductive carbon powder composite film.

[0044] The hot-pressing process utilizes a hot press, specifically involving alternating stacking of three layers of polyvinylidene fluoride / conductive carbon powder / carbonized polyimide modified metal mesh with four layers of polyvinylidene fluoride / conductive carbon powder composite film before hot pressing. During this alternating stacking process, the polyvinylidene fluoride / conductive carbon powder composite film is placed on the outermost layer.

[0045] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0046] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" refers to weight percentage, "parts" refers to parts by weight, and "ratio" refers to weight proportion.

[0047] Example 1

[0048] A method for preparing a copper-based polyvinylidene fluoride / Ketjen black / carbonized polyimide composite material includes the following steps:

[0049] (1) After sanding the copper mesh with sandpaper, clean it with alcohol and then soak it in N,N-dimethylformamide;

[0050] (2) Dissolve 3.0g of 4,4'-diaminodiphenyl ether in 35.6mL of N,N-dimethylformamide and sonicate for 10min to obtain a diamine dispersion. Then add 3.28g of pyromellitic dianhydride to the diamine dispersion in four portions and stir under shear force for 2h to obtain a polyamic acid sol with a solid content of 15wt%.

[0051] (3) While impregnating the copper mesh with polyamic acid sol, ultrasonic treatment was performed for 10 minutes, followed by drying in a precision high-temperature drying oven for 5 hours.

[0052] (4) The copper mesh is transferred to a tube furnace and held at 400°C and 600°C for 1 hour each under an argon atmosphere for thermal imidization and carbonization.

[0053] (5) Dissolve 5g of polyvinylidene fluoride in 50mL of N,N-dimethylformamide and stir magnetically for 12h. Then add 0.56g of Ketjen black powder and stir magnetically until fully dissolved. Finally, perform emulsification treatment for 5h to obtain polyvinylidene fluoride / Ketjen black composite sol, in which Ketjen black accounts for 10wt% of the total solids.

[0054] (6) Coating a copper mesh with polyvinylidene fluoride / Ketjenblack composite sol and simultaneously coating it on a clean glass substrate to form a 15μm wet film, and then drying it at 100℃ for 10h to obtain a polyvinylidene fluoride / Ketjenblack composite film.

[0055] (7) The three layers of copper mesh treated above and the four layers of polyvinylidene fluoride / Ketjen black composite film are stacked alternately and then hot-pressed. The hot-pressing temperature is 180℃, the pressure is 15Mpa, and the time is 30min to obtain copper-based polyvinylidene fluoride / Ketjen black / carbonized polyimide composite material.

[0056] Figure 2 The image shows a physical picture of the copper-based polyvinylidene fluoride / Kejtien black / carbonized polyimide composite material prepared according to the present invention. As can be seen from the figure, the composite material prepared by the present invention has excellent mechanical properties, good toughness, and can be folded into complex shapes without damage.

[0057] Figure 3 The graph shows the electromagnetic shielding effectiveness (ESI) of the copper-based polyvinylidene fluoride / Kejtien black / carbonized polyimide composite material prepared in Example 1 as a function of frequency. The graph shows that within the frequency range of 8.2-12.4 GHz, the total electromagnetic shielding effectiveness (SE) of the composite material is... T Overall, the shielding efficiency is around 90dB, with a maximum of 110dB. It can shield 99.9999999% of electromagnetic waves in the 8.2-12.4GHz band, demonstrating excellent shielding performance. Furthermore, absorption contributes far more to the shielding effectiveness than reflection, significantly reducing secondary electromagnetic pollution.

[0058] Example 2

[0059] A method for preparing a copper-based polyvinylidene fluoride / Ketjen black / carbonized polyimide composite material includes the following steps:

[0060] (1) After sanding the copper mesh with sandpaper, clean it with alcohol and then soak it in N,N-dimethylformamide;

[0061] (2) Dissolve 3.0g of 4,4'-diaminodiphenyl ether in 35.6mL of N,N-dimethylformamide and sonicate for 10min to obtain a diamine dispersion. Then add 3.28g of pyromellitic dianhydride to the diamine dispersion in four portions and stir under shear force for 2h to obtain a polyamic acid sol with a solid content of 15wt%.

[0062] (3) While impregnating the copper mesh with polyamic acid sol, ultrasonic treatment was performed for 12 minutes, followed by drying in a precision high-temperature drying oven for 5.5 hours.

[0063] (4) The copper mesh is transferred to a tube furnace and held at 350°C and 600°C for 1 hour each under an argon atmosphere for thermal imidization and carbonization.

[0064] (5) Dissolve 5g of polyvinylidene fluoride in 50mL of N,N-dimethylformamide and stir magnetically for 12h. Then add 1.25g of Ketjen black powder and stir magnetically until fully dissolved. Finally, perform emulsification treatment for 5h to obtain polyvinylidene fluoride / Ketjen black composite sol, in which Ketjen black accounts for 20wt% of the total solids.

[0065] (6) Coating a copper mesh with polyvinylidene fluoride / Ketjenblack composite sol and simultaneously coating it on a clean glass substrate to form a 15μm wet film, and then drying it at 100℃ for 12h to obtain a polyvinylidene fluoride / Ketjenblack composite film.

[0066] (7) The three layers of copper mesh treated above and the four layers of polyvinylidene fluoride / Ketjen black composite film are stacked alternately and then hot-pressed. The hot-pressing temperature is 180℃, the pressure is 20Mpa, and the time is 35min to obtain copper-based polyvinylidene fluoride / Ketjen black / carbonized polyimide composite material.

[0067] Example 3

[0068] A method for preparing a copper-based polyvinylidene fluoride / graphene / carbonized polyimide composite material includes the following steps:

[0069] S1: 4,4'-Diaminodiphenyl ether was dissolved in N,N-dimethylformamide and sonicated for 5 min to obtain a diamine dispersion. Pyromellitic dianhydride was then added to the diamine dispersion in four portions, and the mixture was stirred under shear force for 2.5 h to obtain the polyamic acid sol. The mass concentration of the polyamic acid sol was 17 wt%.

[0070] S2: The copper mesh is polished, then cleaned with ethanol, and finally soaked in N,N-dimethylformamide and air-dried to complete the pretreatment. The pretreated copper mesh is placed in polyamic acid sol and ultrasonically treated for 10 minutes, and then dried in a precision high-temperature drying oven for 5 hours to obtain a copper mesh loaded with polyamic acid.

[0071] S3: The copper mesh loaded with polyamic acid is subjected to thermal imidization and carbonization treatment under an argon atmosphere to obtain a copper mesh loaded with carbonized polyimide; wherein the thermal imidization treatment temperature is 350℃ and the carbonization treatment temperature is 600℃. Polyvinylidene fluoride is dissolved in N,N-dimethylformamide at a ratio of 1g:8mL and magnetically stirred for 12h. Then, graphene powder is added and magnetically stirred until fully dissolved. Finally, emulsification treatment is performed for 5h to obtain a polyvinylidene fluoride / graphene composite sol. The graphene content in the polyvinylidene fluoride / graphene composite sol is 10wt%.

[0072] S4: The copper mesh loaded with carbonized polyimide is placed in the polyvinylidene fluoride / graphene composite sol, and after ultrasonic treatment and drying, a polyvinylidene fluoride / graphene / carbonized polyimide modified copper mesh is obtained.

[0073] S5: A polyvinylidene fluoride (PVDF) / graphene composite sol is coated onto a clean glass substrate to form a wet film with a thickness of 13 μm. After drying at 100°C for 10 h, a PVDF / graphene composite film is obtained. The PVDF / graphene / carbonized polyimide modified copper mesh and the PVDF / graphene composite film are alternately stacked and then hot-pressed to obtain a copper-based PVDF / graphene / carbonized polyimide composite material. During the hot-pressing process, the temperature is 190°C, the pressure is 16 MPa, and the time is 25 min.

[0074] Example 4

[0075] A method for preparing a copper-based polyvinylidene fluoride / graphene / carbonized polyimide composite material includes the following steps:

[0076] S1: 4,4'-Diaminodiphenyl ether was dissolved in N,N-dimethylformamide and sonicated for 10 min to obtain a diamine dispersion. Pyromellitic dianhydride was then added to the diamine dispersion in four portions, and the mixture was stirred under shear force for 3 h to obtain the polyamic acid sol. The mass concentration of the polyamic acid sol was 18 wt%.

[0077] S2: The copper mesh is polished, then cleaned with ethanol, and finally soaked in N,N-dimethylformamide and air-dried to complete the pretreatment. The pretreated copper mesh is placed in polyamic acid sol and ultrasonically treated for 15 minutes, and then dried in a precision high-temperature drying oven for 6 hours to obtain a copper mesh loaded with polyamic acid.

[0078] S3: The copper mesh loaded with polyamic acid is subjected to thermal imidization and carbonization treatment under an argon atmosphere to obtain a copper mesh loaded with carbonized polyimide; wherein the thermal imidization treatment temperature is 450℃ and the carbonization treatment temperature is 800℃. Polyvinylidene fluoride is dissolved in N,N-dimethylformamide at a ratio of 1g:10mL, and magnetically stirred for 12h. Then, graphene powder is added and magnetically stirred until fully dissolved. Finally, emulsification treatment is performed for 6h to obtain a polyvinylidene fluoride / graphene composite sol. The graphene content in the polyvinylidene fluoride / graphene composite sol is 20wt%.

[0079] S4: The copper mesh loaded with carbonized polyimide is placed in the polyvinylidene fluoride / graphene composite sol, and after ultrasonic treatment and drying, a polyvinylidene fluoride / graphene / carbonized polyimide modified copper mesh is obtained.

[0080] S5: A polyvinylidene fluoride (PVDF) / graphene composite sol is coated onto a clean glass substrate to form a wet film with a thickness of 17 μm. After drying at 100°C for 11 hours, a PVDF / graphene composite film is obtained. The PVDF / graphene / carbonized polyimide modified copper mesh and the PVDF / graphene composite film are alternately stacked and then hot-pressed to obtain a copper-based PVDF / graphene / carbonized polyimide composite material. During the hot-pressing process, the temperature is 200°C, the pressure is 18 MPa, and the time is 30 minutes.

[0081] Example 5

[0082] A method for preparing a copper-based polyvinylidene fluoride / acetylene black / carbonized polyimide composite material includes the following steps:

[0083] S1: 4,4'-Diaminodiphenyl ether was dissolved in N,N-dimethylformamide and sonicated for 7 min to obtain a diamine dispersion. Pyromellitic dianhydride was then added to the diamine dispersion in four portions, and the mixture was stirred under shear force for 2 h to obtain the polyamic acid sol. The mass concentration of the polyamic acid sol was 16 wt%.

[0084] S2: The copper mesh is polished, then cleaned with ethanol, and finally soaked in N,N-dimethylformamide and air-dried to complete the pretreatment. The pretreated copper mesh is placed in polyamic acid sol and ultrasonically treated for 12 minutes, and then dried in a precision high-temperature drying oven for 6 hours to obtain a copper mesh loaded with polyamic acid.

[0085] S3: The copper mesh loaded with polyamic acid is subjected to thermal imidization and carbonization treatment under an argon atmosphere to obtain a copper mesh loaded with carbonized polyimide; wherein the thermal imidization treatment temperature is 350℃ and the carbonization treatment temperature is 700℃. Polyvinylidene fluoride is dissolved in N,N-dimethylformamide at a ratio of 1g:9mL, and magnetically stirred for 12h. Then, acetylene black powder is added and magnetically stirred until fully dissolved. Finally, emulsification treatment is carried out for 6h to obtain a polyvinylidene fluoride / acetylene black composite sol. The acetylene black content in the polyvinylidene fluoride / acetylene black composite sol is 15wt%.

[0086] S4: The copper mesh loaded with carbonized polyimide is placed in the polyvinylidene fluoride / acetylene black composite sol, and after ultrasonic treatment and drying, a polyvinylidene fluoride / acetylene black / carbonized polyimide modified copper mesh is obtained.

[0087] S5: A polyvinylidene fluoride (PVDF) / acetylene black composite sol is coated onto a clean glass substrate to form a wet film with a thickness of 15 μm. After drying at 100°C for 11 hours, a PVDF / acetylene black composite film is obtained. The PVDF / acetylene black / carbonized polyimide modified copper mesh and the PVDF / acetylene black composite film are alternately stacked and then hot-pressed to obtain a copper-based PVDF / acetylene black / carbonized polyimide composite material. During the hot-pressing process, the hot-pressing temperature is 190°C, the pressure is 17 MPa, and the time is 30 minutes.

[0088] Example 6

[0089] A nickel-based polyvinylidene fluoride / Ketjen black / carbonized polyimide composite material and its preparation method, comprising the following steps:

[0090] (1) After gently polishing the nickel mesh, clean it with alcohol and then soak it in N,N-dimethylformamide;

[0091] (2) Dissolve 3.0g of 4,4'-diaminodiphenyl ether in 35.6mL of N,N-dimethylformamide and sonicate for 10min to obtain a diamine dispersion. Then add 3.28g of pyromellitic dianhydride to the diamine dispersion in four portions and stir under shear force for 2h to obtain a polyamic acid sol with a solid content of 15wt%.

[0092] (3) While impregnating the nickel mesh with polyamic acid sol, ultrasonic treatment was performed for 10 minutes, followed by drying in a precision high-temperature drying oven for 5 hours.

[0093] (4) The nickel mesh was transferred to a tube furnace and held at 350°C and 600°C for 1 hour each under an argon atmosphere for thermal imidization and carbonization.

[0094] (5) Dissolve 5g of polyvinylidene fluoride in 50mL of N,N-dimethylformamide and stir magnetically for 12h. Then add 1.25g of Ketjen black powder and stir magnetically until fully dissolved. Finally, perform emulsification treatment for 5h to obtain polyvinylidene fluoride / Ketjen black composite sol, in which Ketjen black accounts for 20wt% of the total solids.

[0095] (6) Coating a nickel mesh with polyvinylidene fluoride / Ketjenblack composite sol and simultaneously coating it onto a clean glass substrate to form a 15μm wet film, and then drying it at 100℃ for 12h to obtain a polyvinylidene fluoride / Ketjenblack composite film.

[0096] (7) The three layers of nickel mesh treated above and the four layers of polyvinylidene fluoride / Ketjen black composite film are stacked alternately and then hot-pressed. The hot-pressing temperature is 180℃, the pressure is 20Mpa, and the time is 35min to obtain nickel-based polyvinylidene fluoride / Ketjen black / carbonized polyimide composite material.

[0097] Figure 4 The graph shows the electromagnetic shielding effectiveness of the nickel-based polyvinylidene fluoride / Kejon's black / carbonized polyimide composite material prepared in Example 6 as a function of frequency. As can be seen from the graph, in the frequency range of 8.2-12.4 GHz, the total electromagnetic shielding effectiveness (SET) of the composite material is around 90 dB, while the shielding effectiveness (SEA) generated by absorption is above 60 dB, contributing more than 2 / 3 to the total electromagnetic shielding effectiveness. It can be seen that absorption plays a dominant role in the shielding mechanism.

[0098] Example 7

[0099] A method for preparing a nickel-based polyvinylidene fluoride / Ketjen black / carbonized polyimide composite material includes the following steps:

[0100] (1) After sanding the nickel mesh with sandpaper, clean it with alcohol and then soak it in N,N-dimethylformamide;

[0101] (2) Dissolve 3.0g of 4,4'-diaminodiphenyl ether in 35.6mL of N,N-dimethylformamide and sonicate for 10min to obtain a diamine dispersion. Then add 3.28g of pyromellitic dianhydride to the diamine dispersion in four portions and stir under shear force for 2h to obtain a polyamic acid sol with a solid content of 15wt%.

[0102] (3) While impregnating the nickel mesh with polyamic acid sol, ultrasonic treatment was performed for 12 minutes, followed by drying in a precision high-temperature drying oven for 5.5 hours.

[0103] (4) The nickel mesh was transferred to a tube furnace and held at 350°C and 600°C for 1 hour each under an argon atmosphere for thermal imidization and carbonization.

[0104] (5) Dissolve 5g of polyvinylidene fluoride in 50mL of N,N-dimethylformamide and stir magnetically for 12h. Then add 1.25g of Ketjen black powder and stir magnetically until fully dissolved. Finally, perform emulsification treatment for 5h to obtain polyvinylidene fluoride / Ketjen black composite sol, in which Ketjen black accounts for 20wt% of the total solids.

[0105] (6) Coating a nickel mesh with polyvinylidene fluoride / Ketjenblack composite sol and simultaneously coating it onto a clean glass substrate to form a 15μm wet film, and then drying it at 100℃ for 12h to obtain a polyvinylidene fluoride / Ketjenblack composite film.

[0106] (7) The three layers of nickel mesh treated above and the four layers of polyvinylidene fluoride / Ketjen black composite film are stacked alternately and then hot-pressed. The hot-pressing temperature is 180℃, the pressure is 20Mpa, and the time is 35min to obtain nickel-based polyvinylidene fluoride / Ketjen black / carbonized polyimide composite material.

[0107] Example 8

[0108] A method for preparing a nickel-based polyvinylidene fluoride / graphene / carbonized polyimide composite material includes the following steps:

[0109] S1: 4,4'-Diaminodiphenyl ether was dissolved in N,N-dimethylformamide and sonicated for 5 min to obtain a diamine dispersion. Pyromellitic dianhydride was then added to the diamine dispersion in four portions, and the mixture was stirred under shear force for 2 h to obtain the polyamic acid sol. The mass concentration of the polyamic acid sol was 18 wt%. The nickel mesh was polished, then cleaned with ethanol, and finally immersed in N,N-dimethylformamide and dried to complete the pretreatment of the nickel mesh. The pretreated nickel mesh was placed in the polyamic acid sol, sonicated for 10 min, and then dried in a precision high-temperature drying oven for 5 h to obtain a nickel mesh loaded with polyamic acid.

[0110] S2: The nickel mesh loaded with polyamic acid is subjected to thermal imidization and carbonization treatment under an argon atmosphere to obtain a nickel mesh loaded with carbonized polyimide; wherein the temperature of thermal imidization treatment is 300℃ and the temperature of carbonization treatment is 600℃.

[0111] S3: Polyvinylidene fluoride (PVDF) was dissolved in N,N-dimethylformamide at a ratio of 1g:8mL and magnetically stirred for 12 hours. Then, graphene was added and magnetically stirred until fully dissolved. Finally, emulsification was performed for 5 hours to obtain a PVDF / graphene composite sol with a graphene content of 10wt%. The nickel mesh loaded with carbonized polyimide was placed in the PVDF / graphene composite sol, ultrasonically treated, and dried to obtain a PVDF / graphene / carbonized polyimide modified nickel mesh.

[0112] S4: A polyvinylidene fluoride (PVDF) / graphene composite sol is coated onto a clean glass substrate to form a wet film with a thickness of 15±2 μm. After drying at 100°C for 10 h, a PVDF / graphene composite film is obtained. The PVDF / graphene / carbonized polyimide modified nickel mesh and the PVDF / graphene composite film are alternately stacked and then hot-pressed to obtain a nickel-based PVDF / graphene / carbonized polyimide composite material. During the hot-pressing process, the temperature is 180°C, the pressure is 16 MPa, and the time is 25 min.

[0113] Example 9

[0114] A method for preparing a nickel-based polyvinylidene fluoride / acetylene black / carbonized polyimide composite material includes the following steps:

[0115] S1: 4,4'-Diaminodiphenyl ether was dissolved in N,N-dimethylformamide and sonicated for 10 min to obtain a diamine dispersion. Pyromellitic dianhydride was then added to the diamine dispersion in four portions, and the mixture was stirred under shear force for 3 h to obtain the polyamic acid sol. The mass concentration of the polyamic acid sol was 15 wt%. The nickel mesh was polished, then cleaned with ethanol, and finally immersed in N,N-dimethylformamide and dried to complete the pretreatment of the aluminum mesh. The pretreated nickel mesh was placed in the polyamic acid sol, sonicated for 15 min, and then dried in a precision high-temperature drying oven for 6 h to obtain a nickel mesh loaded with polyamic acid.

[0116] S2: The nickel mesh loaded with polyamic acid is subjected to thermal imidization and carbonization treatment under an argon atmosphere to obtain a nickel mesh loaded with carbonized polyimide; wherein the temperature of thermal imidization treatment is 400℃ and the temperature of carbonization treatment is 800℃.

[0117] S3: Polyvinylidene fluoride (PVDF) was dissolved in N,N-dimethylformamide at a ratio of 1g:10mL and magnetically stirred for 12 hours. Acetylene black was then added and magnetically stirred until fully dissolved. Finally, an emulsification treatment was performed for 6 hours to obtain a PVDF / acetylene black composite sol with an acetylene black content of 20wt%. The nickel mesh loaded with carbonized polyimide was placed in the PVDF / acetylene black composite sol, ultrasonically treated, and dried to obtain a PVDF / acetylene black / carbonized polyimide modified nickel mesh.

[0118] S4: A polyvinylidene fluoride (PVDF) / acetylene black composite sol is coated onto a clean glass substrate to form a wet film with a thickness of 15±2 μm. After drying at 100°C for 12 hours, a PVDF / acetylene black composite film is obtained. The PVDF / acetylene black / carbonized polyimide modified nickel mesh is alternately stacked with the PVDF / acetylene black composite film and then hot-pressed to obtain a nickel-based PVDF / acetylene black / carbonized polyimide composite material. During the hot-pressing process, the temperature is 200°C, the pressure is 18 MPa, and the time is 30 minutes.

[0119] Example 10

[0120] A method for preparing a nickel-based polyvinylidene fluoride / acetylene black / carbonized polyimide composite material includes the following steps:

[0121] S1: 4,4'-Diaminodiphenyl ether was dissolved in N,N-dimethylformamide and sonicated for 8 min to obtain a diamine dispersion. Pyromellitic dianhydride was then added to the diamine dispersion in four portions, and the mixture was stirred under shear force for 3 h to obtain the polyamic acid sol. The mass concentration of the polyamic acid sol was 16 wt%. The nickel mesh was polished, then cleaned with ethanol, and finally immersed in N,N-dimethylformamide and dried to complete the pretreatment of the nickel mesh. The pretreated nickel mesh was placed in the polyamic acid sol, sonicated for 13 min, and then dried in a precision high-temperature drying oven for 6 h to obtain a nickel mesh loaded with polyamic acid.

[0122] S2: The nickel mesh loaded with polyamic acid is subjected to thermal imidization and carbonization treatment under an argon atmosphere to obtain a nickel mesh loaded with carbonized polyimide; wherein, the temperature of thermal imidization treatment is 350°C and the temperature of carbonization treatment is 700°C.

[0123] S3: Polyvinylidene fluoride (PVDF) was dissolved in N,N-dimethylformamide at a ratio of 1g:10mL and magnetically stirred for 12 hours. Acetylene black was then added and magnetically stirred until fully dissolved. Finally, emulsification was performed for 5–6 hours to obtain a PVDF / acetylene black composite sol with an acetylene black content of 15wt%. The nickel mesh loaded with carbonized polyimide was placed in the PVDF / acetylene black composite sol, ultrasonically treated, and dried to obtain a PVDF / acetylene black / carbonized polyimide modified nickel mesh.

[0124] S4: A polyvinylidene fluoride (PVDF) / acetylene black composite sol is coated onto a clean glass substrate to form a wet film with a thickness of 15±2 μm. After drying at 100°C for 10 h, a PVDF / acetylene black composite film is obtained. The PVDF / acetylene black / carbonized polyimide modified nickel mesh is alternately stacked with the PVDF / acetylene black composite film and then hot-pressed to obtain a nickel-based PVDF / acetylene black / carbonized polyimide composite material. During the hot-pressing process, the hot-pressing temperature is 190°C, the pressure is 16 MPa, and the time is 28 min.

[0125] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

[0126] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a metal-based polyvinylidene fluoride / conductive carbon powder / carbonized polyimide composite material, characterized in that, Includes the following steps: S1: The metal mesh is placed in polyamic acid sol, ultrasonically treated, and then dried to obtain a metal mesh loaded with polyamic acid; S2: The metal mesh loaded with polyamic acid is subjected to thermal imidization and carbonization under an argon atmosphere to obtain a metal mesh loaded with carbonized polyimide. S3: The metal mesh loaded with carbonized polyimide is placed in a composite sol of polyvinylidene fluoride / conductive carbon powder, and after ultrasonic treatment and drying, a polyvinylidene fluoride / conductive carbon powder / carbonized polyimide modified metal mesh is obtained. S4: The polyvinylidene fluoride / conductive carbon powder / carbonized polyimide modified metal mesh and polyvinylidene fluoride / conductive carbon powder composite film are alternately stacked and then hot-pressed to obtain the metal-based polyvinylidene fluoride / conductive carbon powder / carbonized polyimide composite material. Before ultrasonic treatment in polyamic acid sol, the metal mesh is pretreated. The pretreatment process involves polishing the metal mesh, cleaning it with ethanol, and finally immersing it in N,N-dimethylformamide and then drying it. In step S2, the temperature for thermal imidization is 350℃~450℃, and the temperature for carbonization is 600~800℃.

2. The method for preparing a metal-based polyvinylidene fluoride / conductive carbon powder / carbonized polyimide composite material according to claim 1, characterized in that, The metal mesh is at least one of copper mesh and nickel mesh.

3. The method for preparing a metal-based polyvinylidene fluoride / conductive carbon powder / carbonized polyimide composite material according to claim 1, characterized in that, The mass concentration of the polyamic acid sol is 15~18 wt%.

4. The method for preparing a metal-based polyvinylidene fluoride / conductive carbon powder / carbonized polyimide composite material according to claim 1, characterized in that, In step S1, ultrasonic treatment is performed for 10-15 minutes.

5. The method for preparing a metal-based polyvinylidene fluoride / conductive carbon powder / carbonized polyimide composite material according to claim 1, characterized in that, In the composite sol of polyvinylidene fluoride / conductive carbon powder, the conductive carbon powder is at least one of Ketjen black, graphene, and acetylene black; in the composite sol of polyvinylidene fluoride / conductive carbon powder, the mass concentration of the conductive carbon powder is 10~20 wt%.

6. The method for preparing a metal-based polyvinylidene fluoride / conductive carbon powder / carbonized polyimide composite material according to claim 1, characterized in that, In step S4, during the hot pressing process, the hot pressing temperature is 180~200℃, the pressure is 15~20Mpa, and the time is 25~35 min.

7. A metal-based polyvinylidene fluoride / conductive carbon powder / carbonized polyimide composite material, characterized in that, It is prepared by the method described in any one of claims 1 to 6.

8. The application of the metal-based polyvinylidene fluoride / conductive carbon powder / carbonized polyimide composite material as described in claim 7 in the field of electromagnetic shielding.

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