A flexible aramid nanofiber conductive film and its preparation method and application

Abstract

The present invention belongs to the technical field of electromagnetic shielding materials and conductive polymer-based composite materials, and specifically relates to a flexible aramid nanofiber conductive membrane, a preparation method thereof, and an application thereof. First, an aramid nanofiber membrane is prepared by vacuum-assisted filtration, and then immersed in a nickel ion solution for ultrasonic pretreatment and activation treatment with a sodium borohydride solution to obtain a modified aramid nanofiber membrane. Then, under an external magnetic field, the membrane is mixed with a chemical nickel plating solution, dried, and dip-coated with a polydimethylsiloxane encapsulation liquid to obtain a flexible aramid nanofiber membrane. The flexible aramid nanofiber conductive membrane finally obtained has excellent flexibility, heat resistance, and corrosion resistance. The method is easy to operate, economical, and environmentally friendly. The porous layered structure of the formed nanofiber membrane and the nickel coating on the surface give the material excellent electromagnetic shielding performance, which can solve the problem of mutual interference between electronic components.

Description

Technical Field

[0001] The present invention belongs to the technical field of electromagnetic shielding materials and conductive polymer-based composite materials, and particularly relates to a flexible aramid nanofiber conductive film and a preparation method and application thereof. Background Art

[0002] With the widespread adoption of fifth-generation communications (5G), electromagnetic waves, while bringing convenience to human life, also carry significant potential hazards. These hazards not only impact human health but have also become a factor influencing the performance of aircraft, satellites, and many other critical equipment, causing significant distress in people's lives and work. Highly conductive metals have traditionally been chosen as shielding materials, but their rigidity and difficulty in bending have limited their application. Furthermore, while metal materials still hold significant value, many electrochemical metal plating methods often involve complex steps and high energy consumption. Therefore, designing flexible materials with both high electromagnetic shielding performance and low-cost methods is increasingly important, and demand is expected to continue to grow.

[0003] Currently, conductive polymer-based composites can largely address the issue of high material rigidity. They also offer advantages such as low cost, low density, wide applicability, and strong designability. Different polymers can be selected as the matrix material based on actual application requirements, resulting in conductive composite materials with excellent flexibility. Commonly used polymer matrix materials include polyetheretherketone, polyester, polyimide, polyolefin, polylactic acid, epoxy resin, and silicone rubber. Polymer-based flexible conductive films primarily use a flexible polymer as a matrix. Conductive fillers such as metal-based fillers (such as metal particles and metal nanowires), carbon-based fillers, and conductive polymer fillers are coated on the matrix surface or embedded within the matrix to form conductive pathways, thereby achieving controllable conductivity. Preparation methods include blending, electroless plating, surface coating, spraying, electroplating, vapor deposition, sol-gel methods, microporous foaming, and isolation structures. However, some polymer matrices have poor heat resistance, making it difficult to maintain good overall performance at high operating temperatures, making it difficult to meet the application requirements of flexible conductive films. Furthermore, metals like copper and silver are easily oxidized when exposed to the environment, limiting the application of conductive fillers. Patent application number CN202410297420.4 discloses a method for coating carbon nanotubes on the surface of a polyurethane / nonwoven fabric. This method uses a dip coating process, where the polyurethane / nonwoven fabric is immersed in a conductive impregnation solution, physically bonding the conductive layer to the surface. The polyurethane material used in this method has poor heat resistance, typically operating temperatures exceeding 150°C. Furthermore, the dip coating process easily detaches during use, resulting in poor conductivity and electromagnetic shielding performance of the resulting coating. Patent application number CN201610899123.2 discloses a method for copper plating on the surface of polytetrafluoroethylene (PTFE) using a low-temperature plasma treatment. The conductive copper filler used in this method is easily oxidized when exposed to the environment, resulting in poor corrosion resistance, ultimately leading to reduced shielding and conductivity in some corrosive environments. Therefore, a polymer-based flexible conductive film with excellent heat resistance and mechanical properties is urgently needed in this field. Summary of the Invention

[0004] Based on the above problems, the purpose of this application is to overcome the defects of the existing technology and provide a flexible aramid nanofiber conductive film and a preparation method thereof to improve the electromagnetic shielding performance of the material.

[0005] To this end, the first technical solution of the present application discloses a method for preparing a flexible aramid nanofiber conductive film, comprising the following steps:

[0006] Preparation of modified aramid nanofiber membrane: vacuum-assisted filtration of aramid nanofiber dispersion to obtain flexible aramid nanofiber membrane, followed by ultrasonic treatment in nickel ion-containing solution-1 to obtain pretreated flexible aramid nanofiber membrane, and then immersion in sodium borohydride solution to activate the modified flexible aramid nanofiber membrane;

[0007] Prepare an electroless nickel plating solution: add sodium citrate and sodium hypophosphite to the nickel ion-containing solution-2 and adjust the pH to 10;

[0008] Preparation of flexible aramid nanofiber conductive film: Under an external magnetic field, the modified flexible aramid nanofiber membrane is immersed in a chemical nickel plating solution and then dried, and then dip-coated with a polydimethylsiloxane encapsulation solution and then dried to obtain a flexible aramid nanofiber conductive film.

[0009] Furthermore, the aramid nanofibers are dispersed in the aramid nanofiber dispersion, and the aramid nanofibers are one or more of para-aramid yarn fibers, para-aramid staple fibers, para-aramid fabric fibers, para-aramid fibrils, para-aramid pulp, meta-aramid staple fibers, meta-aramid fibrils, and meta-aramid filaments.

[0010] Furthermore, the vacuum-assisted filtration pressure is 0.4-0.8 MPa.

[0011] Furthermore, the ultrasonic treatment power is 40-240w.

[0012] Furthermore, the mass percentage concentration of the nanofiber membrane is 5wt% to 11wt% of the total mass of the chemical plating solution and the nanofibers;

[0013] Furthermore, the mass percentage concentration of the nanofiber membrane is 5wt% to 11wt% of the total mass of the chemical nickel plating solution and the aramid nanofiber.

[0014] Furthermore, in terms of mass percentage concentration, the nickel ion solution containing Ni 2+ 1wt%-6wt%, nickel ion solution-2 2+ 6wt%-18wt%.

[0015] Furthermore, the strength of the external magnetic field is 100-400 mT.

[0016] And, the flexible aramid nanofiber conductive film prepared according to the above preparation method.

[0017] The second technical solution of the present application discloses the application of the flexible aramid nanofiber conductive film in the preparation of shielding materials; and

[0018] A shielding material comprises the above-mentioned flexible aramid nanofiber conductive film.

[0019] The present invention has the following beneficial effects:

[0020] The present invention first prepares an aramid nanofiber membrane by vacuum-assisted filtration, then immerses it in a nickel ion solution for ultrasonic pretreatment and activation treatment with a sodium borohydride solution to obtain a modified aramid nanofiber membrane, and then mixes it with a chemical nickel plating solution under an external magnetic field, dries it, and dip-coats it with a polydimethylsiloxane encapsulation solution to obtain a flexible aramid nanofiber membrane. In this process, the ultrasonic treatment causes the microjets generated in the ultrasonic bath to form new active points on the surface of the nanofiber membrane, promoting the oxidation of hydroxyl groups on the surface of the fiber membrane to form carboxyl groups. The increase in the number of polar functional groups is beneficial to the wettability of the nanofiber, that is, it helps the carboxyl groups on the surface of the fiber membrane to react with Ni. 2+ Contact; using conductive and magnetic nickel nanoparticles as conductive fillers, an electroless nickel plating solution is prepared. With the help of an external magnetic field, the nickel nanoparticles are oriented and distributed to form an ideal conductive path, thereby making the aramid nanofiber conductive film highly conductive; then, polydimethylsiloxane encapsulation liquid is used for dip coating, which ensures good adhesion between the coating and the substrate, preventing the conductive layer from falling off while maintaining the flexibility of the nanofiber membrane, making it superhydrophobic, and further enhancing the corrosion resistance of the conductive film; ultimately, the resulting flexible aramid nanofiber conductive film has excellent flexibility, heat resistance, and corrosion resistance. This method is easy to operate, economical and environmentally friendly. The porous layered structure of the formed nanofiber membrane and the nickel coating on the surface give the material excellent electromagnetic shielding properties, which can solve the problem of mutual interference between electronic components. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is an SEM image of the aramid nanofiber conductive composite film according to Example 1 of the present invention.

[0022] Figure 2 This is the XRD spectrum of the aramid nanofiber membrane and the flexible conductive nanofiber membrane in Example 1 of the present invention.

[0023] Figure 3 This shows the changes in electrical conductivity and shielding performance of the flexible conductive nanofiber membrane of Example 1 of the present invention when subjected to different magnetic field intensities.

[0024] Figure 4 This is the change in microscopic morphology and sheet resistance of the flexible conductive nanofiber membrane in Example 1 of the present invention under different environments.

[0025] FIG5 is a TGA graph of the aramid nanofiber membrane and the flexible conductive nanofiber membrane according to Example 1 of the present invention. DETAILED DESCRIPTION

[0026] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0027] Unless otherwise specifically stated, the relative arrangement of the parts and steps, numerical expressions and numerical values ​​set forth in these embodiments do not limit the scope of the present application. At the same time, it should be understood that, for ease of description, the sizes of the various parts shown in the drawings are not drawn according to actual proportional relationships. The techniques, methods and equipment known to those of ordinary skill in the relevant art may not be discussed in detail, but where appropriate, the techniques, methods and equipment should be considered as part of the authorization specification. In all examples shown and discussed here, any specific values ​​should be interpreted as being merely exemplary and not as limitations. Therefore, other examples of the exemplary embodiments may have different values. It should be noted that similar numbers and letters represent similar items in the following figures, and therefore, once an item is defined in one figure, it does not need to be further discussed in subsequent figures.

[0028] The first embodiment of the present application discloses a method for preparing a flexible aramid nanofiber conductive film, comprising the following steps:

[0029] Preparation of modified aramid nanofiber membrane: vacuum-assisted filtration of aramid nanofiber dispersion to obtain flexible aramid nanofiber membrane, followed by ultrasonic treatment in nickel ion-containing solution-1 to obtain pretreated flexible aramid nanofiber membrane, and then immersion in sodium borohydride solution to activate the modified flexible aramid nanofiber membrane;

[0030] Prepare an electroless nickel plating solution: add sodium citrate and sodium hypophosphite to the nickel ion-containing solution-2 and adjust the pH to 10;

[0031] Preparation of flexible aramid nanofiber conductive film: Under an external magnetic field, the modified flexible aramid nanofiber membrane is immersed in a chemical nickel plating solution and then dried, and then dip-coated with a polydimethylsiloxane encapsulation solution and then dried to obtain a flexible aramid nanofiber conductive film.

[0032] In this embodiment, the aramid nanofiber dispersion is a mixture containing dispersed aramid fibers. A preferred preparation method is as follows: Substance A and substance B are mixed at a ratio of (0.3-3.0) g:20 mL, where substance A is potassium hydroxide, potassium tert-butoxide, or sodium hydroxide, and substance B is one or more of deionized water, ethanol, and methanol, to obtain solution A; solution A is then mixed with one or more of dimethyl sulfoxide and N,N-dimethylacetamide at a ratio of 20 mL:500 mL to obtain mixture B; aramid fibers are added to mixture B at a ratio of 2 g:520 mL, and the mixture is continuously stirred at 20-80°C to obtain the aramid nanofiber dispersion. The stirring temperature is 20-80°C, the stirring speed is 800-1200 r / min, and the stirring time is 1-7 days.

[0033] In a further embodiment, the aramid fiber in the preparation of the aramid fiber nano-dispersion is fully called poly(p-phenylene terephthalamide), which is a synthetic fiber; the fibers preferably used in this application are any one or more of para-aramid yarn fiber, para-aramid staple fiber, para-aramid fabric fiber, para-aramid precipitated fiber or para-aramid pulp, meta-aramid staple fiber, meta-aramid precipitated fiber, and meta-aramid filament.

[0034] It can be understood that in the vacuum-assisted filtration process, in order to improve the filtration efficiency, the present application preferably adds the aramid fiber nanodispersion into deionized water for filtration, and the filtration pressure is preferably 0.4-0.8 MPa, and the filtered components are further dried at a drying temperature of 40-80°C.

[0035] In a further embodiment, the flexible aramid nanofiber membrane obtained by vacuum assisted filtration drying is immersed in a nickel ion solution for ultrasonic treatment. The ultrasonic treatment causes the microjets generated in the ultrasonic bath to form new active points on the surface of the nanofiber flexible film, promoting the oxidation of hydroxyl groups on the surface of the fiber membrane to form carboxyl groups, thereby increasing the oxygen-containing polar functional groups on the surface of the fiber membrane, which helps to improve the wettability of the fiber membrane surface, improve the surface activity of the fiber membrane, and help the carboxyl groups on the surface of the fiber membrane to react with Ni. 2+ Contact, so that it undergoes a coordination reaction to form a coordination bond -COO-Ni, thereby modifying and modifying the metal ions, stabilizing the metal ions on the ligand molecules, and improving the binding force between the fiber membrane and the metal ions. In order to achieve the above purpose, the ultrasonic treatment power is 40-240w.

[0036] In this embodiment, the nickel ion solution-1 is obtained by dissolving a nickel salt. The preferred nickel salt in this application is nickel chloride hexahydrate, specifically, nickel chloride hexahydrate is added to deionized water and mixed until completely dissolved. When nickel chloride hexahydrate is used as the nickel salt, the applicant has determined through gradient experiments that the concentration of the nickel chloride solution is 2-10 g / L, preferably 7 g / L. At this time, in terms of mass percentage concentration, Ni 2+ Concentration is 1wt%-6wt%

[0037] In a further embodiment, the pre-treated flexible aramid nanofiber membrane, after ultrasonic treatment, is immersed in a sodium borohydride solution for activation. This is intended to better reduce the metallic nickel ions on the membrane surface during the subsequent electroless nickel plating process. Compared to the palladium activation process commonly used in the prior art, the use of sodium borohydride for membrane activation in this application can significantly save and reduce costs.

[0038] In this embodiment, the chemical nickel plating solution is prepared by adding sodium citrate and sodium hypophosphite to the nickel ion-containing solution-2 and then adjusting the pH to alkaline.

[0039] The preparation method of the nickel ion solution-2 is the same as that of the nickel ion solution-1, wherein, in terms of mass percentage concentration, Ni 2+ The content is preferably 6wt%-18wt% of the nickel ion solution-2.

[0040] In a further embodiment, the purpose of adding sodium citrate and sodium hypophosphite is to improve the quality of the coating and ensure the stability of the electroplating process. Sodium citrate can form a stable complex with nickel ions, which can prevent nickel ions from precipitating or being reduced in the electrolyte, thereby helping nickel ions to stably exist in the electrolyte. At the same time, sodium citrate can promote the formation of sediments and enhance the adhesion between the sediments and the substrate. In addition, the chemical plating system containing sodium hypophosphite is environmentally friendly. In order to ensure the high conductivity of the obtained coating, a coating with a lower phosphorus content is formed, so chemical nickel plating is selected in an alkaline environment. Therefore, the pH range can be 8 to 14. The present application is preferably pH=10, and for this reason, the addition ratio of nickel ion solution to sodium citrate and sodium hypophosphite is preferably 1.9:1:1.7.

[0041] In this embodiment, the external magnetic field strength for preparing the flexible aramid nanofiber conductive film is 100-400mT; under this external magnetic field, the nickel nanoparticles in the nickel ion-containing solution can be oriented and distributed to form an ideal conductive path, thereby making the aramid nanofiber conductive film have efficient conductivity.

[0042] It should be noted that in the prior art, when selecting nickel as a conductive filler, metallic nickel is generally directly blended with the matrix material. However, this composite method will lead to uneven dispersion of nickel nanoparticles, and the nickel nanoparticles and the matrix material are only physically bound together, which can also cause problems with shielding performance and stability. Alternatively, the traditional palladium activation process is used to chemically deposit nickel, which is costly and causes environmental pollution. However, the present application uses an external magnetic field to induce nickel ions to form an oriented conductive path, which not only makes the nickel nanoparticles evenly dispersed, but also reduces costs.

[0043] It can be understood that after the modified flexible nanofiber membrane is immersed in a chemical nickel plating solution and treated with an external magnetic field, the surface is a wet fiber membrane; therefore, in a further embodiment, it is necessary to place the wet modified aramid nanofiber membrane wrapped by nickel nano ions on a carrier for drying, and the carrier is preferably any one of a polytetrafluoroethylene plate, a glass substrate, a stainless steel plate or a cellulose acetate film, and the drying temperature is 40-80°C.

[0044] In this embodiment, the membrane obtained after drying is dipped in polydimethylsiloxane encapsulation liquid and then dried to obtain a flexible aramid nanofiber conductive membrane.

[0045] The use of a polydimethylsiloxane encapsulating liquid for dip coating can ensure good adhesion between the coating and the substrate, preventing the conductive layer from falling off while maintaining the flexibility of the nanofiber membrane, making it superhydrophobic and further enhancing the corrosion resistance of the conductive membrane. The polydimethylsiloxane encapsulating liquid is prepared by mixing a polydimethylsiloxane base liquid with a solvent in a ratio of 1:1 to 1:10. The solvent is one or more of xylene, n-hexane, and n-decane.

[0046] The resulting flexible aramid nanofiber conductive membrane exhibits excellent flexibility, heat resistance, and corrosion resistance. The method is also easy to operate, economical, and environmentally friendly. The porous layered structure of the resulting nanofiber membrane and the nickel coating on its surface provide the material with excellent electromagnetic shielding properties, addressing the problem of mutual interference between electronic components.

[0047] The technical effects of the present invention will be more clearly described below with reference to the accompanying drawings and specific embodiments.

[0048] Example 1 Preparation of flexible aramid nanofiber conductive film

[0049] S1. Preparation of aramid nanofiber dispersion: Potassium tert-butoxide and methanol were mixed to obtain solution A for later use. Para-aramid fabric fibers, solution A, and dimethyl sulfoxide were then mixed in a ratio of 2 g: 20 mL: 500 mL. After stirring at 900 rpm at 70°C for 1 day, deionized water was added to obtain a deep red aramid nanofiber dispersion with a concentration of 1.2 mg / mL.

[0050] S2. Preparation of a modified flexible aramid nanofiber membrane: adding an aramid nanofiber dispersion to deionized water; vacuum-assisted filtration of the prepared nanofiber dispersion using a sand core funnel and a 0.45 μm microporous filter membrane at a vacuum degree of 0.6 MPa; drying at 80°C to obtain a flexible aramid nanofiber membrane. Preferably, 5 wt% is used as the mass percentage concentration of the nanofiber membrane: 5.6 g of the obtained flexible aramid nanofiber membrane is immersed in a 7 g / L nickel chloride solution for ultrasonic treatment, washed with deionized water, and dried at 80°C to obtain a pretreated flexible aramid nanofiber membrane; the pretreated flexible aramid nanofiber membrane is immersed in a sodium borohydride solution for activation, washed, and dried to obtain a modified flexible aramid nanofiber membrane for use.

[0051] S3. Preparation of flexible aramid nanofiber conductive membrane: Weigh 2g nickel chloride and add 100mL deionized water to mix until completely dissolved, then add 2g sodium citrate and sodium hypophosphite in sequence to form a Ni-containing conductive membrane. 2+ A green, transparent solution was prepared. The pH of the mixed solution was then adjusted to 10.0 using a 20wt% sodium hydroxide solution. A 120mT external magnetic field was then introduced, and the modified flexible aramid nanofiber membrane was placed in an electroless nickel plating solution. The wet nickel nanoparticle-coated aramid nanofiber membrane was placed on a polytetrafluoroethylene plate to dry. Finally, the prepared polydimethylsiloxane solution was dip-coated onto the plate and dried at 80°C to yield a flexible aramid nanofiber conductive membrane.

[0052] In addition, referring to the preparation method of Example 1, the applied electric field intensity of step S3 was changed to 214 mT and 340 mT to obtain flexible aramid nanofiber conductive films, which were respectively recorded as Example 2 (214 mT) and Example 3 (340 mT).

[0053] Comparative Example 1 Preparation of flexible aramid nanofiber membrane

[0054] The preparation method is the same as S1-S2 in Example 1: the aramid nanofiber dispersion is subjected to vacuum-assisted filtration and then dried to obtain the obtained product.

[0055] Comparative Example 2 Preparation of flexible aramid nanofiber conductive film

[0056] The preparation method is the same as that of Example 1, except that, in Comparative Example 2, no external magnetic field treatment is performed in step S3.

[0057] Experimental Example 1 Characterization of the structure of flexible aramid nanofiber conductive film

[0058] The flexible aramid nanofiber conductive films prepared in Example 1 (Ni@NAF) and Comparative Example 1 (NAF) were characterized. Figure 1 This is an SEM image of the flexible aramid nanofiber conductive membrane of Example 1. It can be seen that nickel nanoparticles are formed on the surface of the nanofiber membrane, and a continuous nickel coating is formed, filling the pore structure of the original nanofiber membrane. Figure 2 The XRD spectra of the flexible aramid nanofiber membrane of comparative example 1 and the flexible aramid nanofiber conductive membrane of embodiment 1 are compared with those of comparative example 1. The peaks at 44.8°, 51.3° and 77.2° of the XRD spectrum of the conductive nanofiber membrane of embodiment 1 belong to the characteristic peaks of metallic nickel, which confirms that Ni 2+ The successful reduction of aramid nanofibers indicates that the flexible aramid nanofiber conductive film has been successfully prepared.

[0059] Test Example 2 Electromagnetic Shielding Test

[0060] The flexible aramid nanofiber conductive film prepared in Example 1 was used as an electromagnetic shielding material to test its conductivity and shielding performance under different magnetic field intensities. The specific steps are as follows:

[0061] The flexible aramid nanofiber conductive film is cut into discs with a diameter of 12 mm. The conductivity of the conductive performance is tested using a four-probe tester, and the shielding performance is tested using a vector network analyzer with a measurement frequency range of 8.2-12.4 GHz. When the flexible aramid nanofiber conductive film is used as a shielding material, its shielding mechanism is that the electromagnetic waves are first reflected and attenuated on the surface of the material; secondly, the electromagnetic waves that penetrate the surface are absorbed inside the material and further attenuated; finally, multiple reflections inside the material also cause electromagnetic waves to attenuate. The electromagnetic shielding effectiveness (EMI SE) is calculated using the following formula: SE T =SE A +SE R+ SE M , among which, SE T is the total electromagnetic shielding efficiency, SE A is the efficiency of electromagnetic wave absorption loss, SE R Indicates the efficiency of electromagnetic wave reflection loss, SE M It is the efficiency of multiple reflection loss of electromagnetic waves. Figure 33 is a graph showing the changes in conductivity and shielding performance under different magnetic field intensities, wherein N-7 represents a nickel chloride concentration of 7 g / L in an electroless nickel plating solution calculated as nickel chloride, and no external magnetic field treatment is performed (Comparative Example 2), and NM7-1, NM7-2, and NM7-3 represent a nickel chloride concentration of 7 g / L in an electroless nickel plating solution calculated as nickel chloride, and an external magnetic field of 120 mT (Example 1), 214 mT (Example 2), and 340 mT (Example 3), respectively. Figure 3 (a) The results show that N7 has relatively low electrical conductivity. At the same concentration, the flexible aramid nanofiber conductive membrane prepared in the presence of a magnetic field exhibits higher conductivity than the conductive fiber membrane prepared without magnetic field induction. For example, the conductivity of NM7-M3 is seven times that of N7. Figure (b) shows that the trend of EMI SE is consistent with the conductivity, and the EMI SE of the conductive nanofiber membrane is significantly improved after magnetic field induction. For example, the EMI SE of NM7-M3 is 36 dB higher than that of N7. This demonstrates that the conductive nanofiber membrane has excellent electrical conductivity and shielding properties, and that the magnetic field forces promote the alignment of nickel nanoparticles, thereby promoting the formation of an ordered conductive network.

[0062] Test Example 3 Stability and Corrosion Resistance Test

[0063] The flexible aramid nanofiber conductive membranes of Example 1 (Ni@NAF) and Comparative Example 1 (NAF) were immersed in 10 wt% HCl, 10 wt% NaOH, and 5 wt% NaCl solutions for 48 hours for corrosion resistance tests to evaluate the corrosion resistance of the nickel coating. Figure 4 : It is a graph showing the change of micromorphology and sheet resistance after the corrosion resistance test of Example 1, wherein a1 and a2 are micromorphologies after treatment with 10 wt% HCl (a1-10 μm, a2-4 μm), b1 and b2 are micromorphologies after treatment with 10 wt% NaOH (b1-10 μm, b2-4 μm), c1 and c2 are micromorphologies after treatment with 5 wt% NaCl (c1-10 μm, c2-4 μm), and d is a graph showing the change of sheet resistance (wherein, d-① is the change of the sheet resistance of the untreated flexible aramid nanofiber conductive film, d-② is the change of the sheet resistance of the untreated flexible aramid nanofiber conductive film, d-③ is the change of the sheet resistance of the untreated flexible aramid nanofiber conductive film, d-④ is the change of the sheet resistance of the untreated flexible aramid nanofiber conductive film, d-① is the change of the sheet resistance of the untreated flexible aramid nanofiber conductive film, d-② is the change of the sheet resistance of the untreated flexible aramid nanofiber conductive film, d-③ is the change of the sheet resistance of the untreated flexible aramid nanofiber conductive film, d-④ is the change of the sheet resistance of the untreated flexible aramid nanofiber conductive film, d- NaCl treatment); it can be observed that in an acidic environment, the nickel coating suffers a certain degree of corrosion, forming a "worm-like" structure, and the sheet resistance increases significantly (Figure d-②). However, in alkaline (Figure d-③) and saline (Figure d-④) environments, the overall morphology and sheet resistance are largely unaffected. This indicates that the prepared conductive nanofiber membrane is relatively weak in acidic environments, but exhibits good stability in alkaline and saline environments. Figure 5The TGA curves for the flexible aramid nanofiber membrane from Comparative Example 1 and the flexible aramid nanofiber conductive membrane from Example 1 show that the decomposition temperatures of both the flexible aramid nanofiber membrane and the flexible nanofiber conductive membrane are above 500°C, demonstrating the good thermal stability of the flexible conductive nanofiber membrane. After electroless nickel plating, both the initial and complete decomposition temperatures of the membranes were increased.

[0064] The above embodiments are only used to illustrate the technical solutions of the present invention, but the scope of protection of the present invention is not limited thereto. The embodiments of the present invention and the features in the embodiments can be arbitrarily combined with each other without conflict. Any person skilled in the art can easily think of changes or replacements within the technical scope disclosed by the present invention, which should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A method for preparing a flexible aramid nanofiber conductive film, characterized in that: The steps include: Preparation of modified aramid nanofiber membrane: vacuum-assisted filtration of aramid nanofiber dispersion to obtain flexible aramid nanofiber membrane, followed by ultrasonic treatment in nickel ion-containing solution-1 to obtain pretreated flexible aramid nanofiber membrane, and then immersion in sodium borohydride solution to activate the modified flexible aramid nanofiber membrane; Preparation of chemical nickel plating solution: adding sodium citrate and sodium hypophosphite to nickel ion-containing solution-2 and adjusting the pH to alkaline; Preparation of a flexible aramid nanofiber conductive film: Under an external magnetic field, the modified flexible aramid nanofiber membrane is impregnated with a chemical nickel plating solution and then dried, and then dip-coated with a polydimethylsiloxane encapsulation solution and then dried to obtain a flexible aramid nanofiber conductive film; Among them, in terms of mass percentage concentration, the nickel ion solution containing Ni-1 2+ 1wt%-6wt%, nickel ion solution-2 2+ 6wt%-18wt%.

2. The preparation method according to claim 1, characterized in that The aramid nanofibers are dispersed in the aramid nanofiber dispersion, wherein the aramid nanofibers are one or more of para-aramid yarn fibers, para-aramid short fibers, para-aramid fabric fibers, para-aramid fibrils, para-aramid pulp, meta-aramid short fibers, meta-aramid fibrils, and meta-aramid filaments.

3. The preparation method according to claim 1, characterized in that The vacuum-assisted filtration pressure is 0.4-0.8 MPa.

4. The preparation method according to claim 1, characterized in that The ultrasonic treatment power is 40-240w.

5. The preparation method according to claim 1, characterized in that: The mass percentage concentration of the nanofiber membrane is 5wt% to 11wt% of the total mass of the chemical nickel plating solution and the aramid nanofiber.

6. The preparation method according to claim 1, characterized in that: In the preparation of the chemical nickel plating solution, the addition ratio of nickel ion solution, sodium citrate and sodium hypophosphite is: 1.9:1:1.7。 7. The preparation method according to claim 1, characterized in that: The strength of the external magnetic field is 100-400 mT.

8. A flexible aramid nanofiber conductive film prepared according to the preparation method according to any one of claims 1 to 7.

9. Use of the flexible aramid nanofiber conductive film according to claim 8 in the preparation of shielding materials.

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