A double-network cross-linked self-healing electromagnetic shielding material and its preparation method

Abstract

The present invention discloses a dual-network cross-linked self-healing electromagnetic shielding material and its preparation method. A layered MXene structure is prepared, followed by in-situ polymerization using protonic acid as a dopant to produce a highly conductive MXene / polypyrrole composite. The MXene / polypyrrole composite is then used as a conductive filler, and polyvinyl alcohol is used as a polymer matrix to construct a dual-network cross-linked electromagnetic shielding composite material with excellent self-healing properties, comprised of boric acid and cellulose nanocrystals. The resulting composite material not only exhibits excellent electromagnetic shielding performance in the L- and X-bands but also exhibits excellent self-healing properties. Hydrogen bonds are formed through contact with the bisected surface or by water spraying, allowing the damaged area to self-heal. This composite material has promising application in the field of functional electromagnetic shielding materials.

Description

Technical Field

[0001] The present invention belongs to the technical field of functional electromagnetic shielding materials and relates to a double-network cross-linked self-healing electromagnetic shielding material and a preparation method thereof. Background Art

[0002] Traditional electromagnetic shielding materials are mostly made of metals and their alloys. While these materials offer excellent electromagnetic shielding performance, they also suffer from disadvantages such as heavy weight, corrosion resistance, and poor flexibility. Polymer-based conductive composites, with their numerous advantages including lightweight, excellent mechanical properties, corrosion resistance, chemical stability, tunable properties, and ease of processing and forming, are attracting increasing attention in the electromagnetic shielding material field. However, existing polymer-based electromagnetic shielding composites can significantly degrade in shielding performance when scratched or damaged by external forces, leading to them becoming useless and being discarded, resulting in a waste of resources. Therefore, imparting excellent self-healing properties to polymer-based electromagnetic shielding materials is of great significance.

[0003] Self-healing materials can be categorized as externally and internally repairable based on their self-healing mechanisms. Externally repairable polymers repair damaged areas using liquid substances encapsulated in capsules or containers. However, this approach offers poor repair effectiveness and cannot be repeated. Internally repairable polymers repair damage through interactions between polymer chains, such as hydrogen bonds, hydrophobic interactions, and supramolecular interactions. This self-healing process can repeatedly repair damaged areas of the material, making it an ideal material repair method. Summary of the Invention

[0004] The present invention relates to a dual-network cross-linked self-healing electromagnetic shielding material and its preparation method. First, a polypyrrole / MXene composite material with excellent conductivity is obtained through in-situ polymerization. The polymer-based self-healing electromagnetic shielding material is then prepared. The resulting material not only exhibits excellent electromagnetic shielding performance but also self-heals.

[0005] The present invention is achieved through the following technical solutions.

[0006] The present invention provides a double-network cross-linked self-healing electromagnetic shielding material and a preparation method thereof, comprising the following processes: preparation of MXene / polypyrrole conductive filler, and preparation of a double-cross-linked network hydrogen bond-driven self-healing electromagnetic shielding composite material.

[0007] A double-network cross-linked self-healing electromagnetic shielding material and a preparation method thereof, specifically comprising the following steps:

[0008] (1) Add 10-15 g of LiF to 50 mL of 1 mol / L HCl solution, stir mechanically for 5-15 min, then slowly add the MAX phase, react at 30-40 °C for 24 h, and then centrifuge, wash, and dry to obtain MXene powder;

[0009] (2) 10 mL of pyrrole monomer and 5-10 g of MXene solid powder obtained in step (1) were dispersed in 50-100 mL of ethanol aqueous solution (volume ratio of 1:1) to prepare a MXene solution, and then 10-20 g of ammonium persulfate was added to the mixed solution. After mechanical stirring in an ice bath at 0°C for 12-20 h, the obtained product was filtered, washed, and vacuum-dried at 50-60°C to obtain a polypyrrole / MXene composite;

[0010] (3) dispersing the polypyrrole / MXene composite, cellulose nanocrystals, and polyvinyl alcohol in deionized water, and mixing them at a stirring speed of 200 r / min at 70-90°C until the polyvinyl alcohol is completely dissolved to obtain a mixed solution;

[0011] (4) adding an appropriate amount of boric acid to the mixed solution obtained in step (3) and continuing the reaction for 1 to 2 hours to obtain a double-network cross-linked mixed solution composed of cellulose nanocrystals and boric acid;

[0012] (5) Pour the mixed solution obtained in step (4) into a flat glass mold, and vacuum dry it at 50-60° C. until the water is completely evaporated to obtain a double-network cross-linked self-healing electromagnetic shielding material.

[0013] Preferably, the MAX phase in step (1) is one or more of Ti3AlC2, Ti2AlC or Ti3AlCN, and has a particle size of ≤200 mesh.

[0014] Preferably, in step (3), the ratio of the polypyrrole / MXene composite, cellulose nanocrystals and polyvinyl alcohol is 30-40 parts, 10-20 parts and 40-60 parts, and the solid content of the three in deionized water is 10% to 15%.

[0015] The resulting material has excellent electromagnetic shielding performance, with an average electromagnetic shielding effectiveness of 36dB in the L-band (1-2GHz) and 27dB in the X-band (8-12GHz). Furthermore, the resulting electromagnetic shielding material exhibits excellent self-healing properties at room temperature, with a repair efficiency of up to 88%.

[0016] Beneficial effects of the present invention:

[0017] (1) The polypyrrole / MXene composite was prepared by in-situ polymerization, and a composite material with good dual-band electromagnetic shielding effect was obtained. Compared with metals and metal alloys, polypyrrole and MXene not only have the advantages of light weight and corrosion resistance, but also their electromagnetic wave loss mechanism mainly relies on absorption loss rather than reflection loss, which will not cause secondary pollution of electromagnetic waves. Both MXene and polypyrrole have good electrical conductivity and can effectively promote the dielectric loss of electromagnetic waves; the multilayer structure of MXene is conducive to the multiple reflection loss and absorption of electromagnetic waves within the material; polypyrrole has an electronic conjugated system, which can convert the electrical energy generated by electromagnetic waves into heat energy, and it is easy to control the conductivity and dielectric constant through chemical reactions, which can effectively improve the electromagnetic shielding performance of the material; the difference in conductivity between polypyrrole and MXene forms an interface effect, which is conducive to further absorption and loss of electromagnetic waves.

[0018] (2) The present invention constructs a polyvinyl alcohol-based composite material with a double-network cross-linking structure driven by borate bonds and cellulose nanocrystal hydrogen bonds. The resulting material has excellent self-healing properties, with a repair rate of up to 88% at room temperature. The present invention uses polyvinyl alcohol as a matrix and adopts boric acid and cellulose nanocrystals as cross-linking agents to prepare a self-healing electromagnetic shielding composite material. Boric acid reacts with polyvinyl alcohol to form a borate dynamic reversible bond, which enables polyvinyl alcohol to self-heal; the surface of cellulose nanocrystals has rich active functional groups, which can form strong hydrogen bonds with the hydroxyl groups in the polyvinyl alcohol molecular chain, enabling polyvinyl alcohol to self-heal. The present invention combines dynamic reversible construction with hydrogen bonding to form a double-network, double-dynamic cross-linking self-healing electromagnetic shielding material, achieving an efficient repair effect at room temperature. DETAILED DESCRIPTION

[0019] In order to have a clearer understanding of the technical features of the present invention, the technical solution of the present invention is now described in detail below, but it should not be understood as limiting the scope of implementation of the present invention.

[0020] Example 1

[0021] (1) 10 g of LiF was added to 50 mL of 1 mol / L HCl solution. After mechanical stirring for 10 min, 5 g of Ti3AlC2 was slowly added and reacted at 35 °C for 24 h. MXene powder was then obtained by centrifugation, washing, and drying.

[0022] (2) 10 mL of pyrrole monomer and 5 g of MXene solid powder obtained in step (1) were dispersed in 100 mL of ethanol aqueous solution (volume ratio of 1:1) to prepare a MXene solution, and then 10 g of ammonium persulfate was added to the mixed solution. After mechanical stirring in an ice bath at 0°C for 12 h, the obtained product was filtered, washed, and vacuum-dried at 60°C to obtain a polypyrrole / MXene composite;

[0023] (3) 4 g of polypyrrole / MXene composite, 2 g of cellulose nanocrystals, and 4 g of polyvinyl alcohol were dispersed in 100 mL of deionized water and mixed at 80 °C at a stirring speed of 200 r / min until the polyvinyl alcohol was completely dissolved to obtain a mixed solution;

[0024] (4) adding 2 g of boric acid dropwise to the mixed solution obtained in step (3) and continuing the reaction for 2 h to obtain a double-network cross-linked mixed solution composed of cellulose nanocrystals and boric acid;

[0025] (5) Pour the mixed solution obtained in step (4) into a flat glass mold, and vacuum dry it at 60° C. until the water is completely evaporated to obtain a double-network cross-linked self-healing electromagnetic shielding material.

[0026] Example 2

[0027] (1) 10 g of LiF was added to 50 mL of 1 mol / L HCl solution. After mechanical stirring for 10 min, 5 g of Ti3AlC2 was slowly added and reacted at 35 °C for 24 h. MXene powder was then obtained by centrifugation, washing, and drying.

[0028] (2) 10 mL of pyrrole monomer and 5 g of MXene solid powder obtained in step (1) were dispersed in 100 mL of ethanol aqueous solution (volume ratio of 1:1) to prepare a MXene solution, and then 10 g of ammonium persulfate was added to the mixed solution. After mechanical stirring in an ice bath at 0°C for 12 h, the obtained product was filtered, washed, and vacuum-dried at 60°C to obtain a polypyrrole / MXene composite;

[0029] (3) 3 g of polypyrrole / MXene composite, 2 g of cellulose nanocrystals, and 5 g of polyvinyl alcohol were dispersed in 100 mL of deionized water and mixed at 80 °C at a stirring speed of 200 r / min until the polyvinyl alcohol was completely dissolved to obtain a mixed solution;

[0030] (4) adding 3 g of boric acid dropwise to the mixed solution obtained in step (3) and continuing the reaction for 2 h to obtain a double-network cross-linked mixed solution composed of cellulose nanocrystals and boric acid;

[0031] (5) Pour the mixed solution obtained in step (4) into a flat glass mold, and vacuum dry it at 60° C. until the water is completely evaporated to obtain a double-network cross-linked self-healing electromagnetic shielding material.

[0032] Example 3

[0033] (1) 10 g of LiF was added to 50 mL of 1 mol / L HCl solution. After mechanical stirring for 10 min, 5 g of Ti3AlC2 was slowly added and reacted at 35 °C for 24 h. MXene powder was then obtained by centrifugation, washing, and drying.

[0034] (2) 10 mL of pyrrole monomer and 5 g of MXene solid powder obtained in step (1) were dispersed in 100 mL of ethanol aqueous solution (volume ratio of 1:1) to prepare a MXene solution, and then 10 g of ammonium persulfate was added to the mixed solution. After mechanical stirring in an ice bath at 0°C for 12 h, the obtained product was filtered, washed, and vacuum-dried at 60°C to obtain a polypyrrole / MXene composite;

[0035] (3) 4 g of polypyrrole / MXene composite, 3 g of cellulose nanocrystals, and 3 g of polyvinyl alcohol were dispersed in 100 mL of deionized water and mixed at 80 °C at a stirring speed of 200 r / min until the polyvinyl alcohol was completely dissolved to obtain a mixed solution;

[0036] (4) adding 3 g of boric acid dropwise to the mixed solution obtained in step (3) and continuing the reaction for 2 h to obtain a double-network cross-linked mixed solution composed of cellulose nanocrystals and boric acid;

[0037] (5) Pour the mixed solution obtained in step (4) into a flat glass mold, and vacuum dry it at 60° C. until the water is completely evaporated to obtain a double-network cross-linked self-healing electromagnetic shielding material.

[0038] Example 4

[0039] (1) 10 g of LiF was added to 50 mL of 1 mol / L HCl solution. After mechanical stirring for 10 min, 3 g of Ti3AlC2 and 2 g of Ti2AlC were slowly added. The mixture was reacted at 35 °C for 24 h. MXene powder was then obtained by centrifugation, washing, and drying.

[0040] (2) 10 mL of pyrrole monomer and 5 g of MXene solid powder obtained in step (1) were dispersed in 100 mL of ethanol aqueous solution (volume ratio of 1:1) to prepare a MXene solution, and then 10 g of ammonium persulfate was added to the mixed solution. After mechanical stirring in an ice bath at 0°C for 12 h, the obtained product was filtered, washed, and vacuum-dried at 60°C to obtain a polypyrrole / MXene composite;

[0041] (3) 4 g of polypyrrole / MXene composite, 2 g of cellulose nanocrystals, and 4 g of polyvinyl alcohol were dispersed in 100 mL of deionized water and mixed at 80 °C at a stirring speed of 200 r / min until the polyvinyl alcohol was completely dissolved to obtain a mixed solution;

[0042] (4) adding 2 g of boric acid dropwise to the mixed solution obtained in step (3) and continuing the reaction for 2 h to obtain a double-network cross-linked mixed solution composed of cellulose nanocrystals and boric acid;

[0043] (5) Pour the mixed solution obtained in step (4) into a flat glass mold, and vacuum dry it at 60° C. until the water is completely evaporated to obtain a double-network cross-linked self-healing electromagnetic shielding material.

[0044] Example 5

[0045] (1) 10 g of LiF was added to 50 mL of 1 mol / L HCl solution. After mechanical stirring for 10 min, 3 g of Ti3AlC2 and 2 g of Ti3AlCN were slowly added. The mixture was reacted at 35 °C for 24 h. MXene powder was then obtained by centrifugation, washing, and drying.

[0046] (2) 10 mL of pyrrole monomer and 5 g of MXene solid powder obtained in step (1) were dispersed in 100 mL of ethanol aqueous solution (volume ratio of 1:1) to prepare a MXene solution, and then 10 g of ammonium persulfate was added to the mixed solution. After mechanical stirring in an ice bath at 0°C for 12 h, the obtained product was filtered, washed, and vacuum-dried at 60°C to obtain a polypyrrole / MXene composite;

[0047] (3) 4 g of polypyrrole / MXene composite, 2 g of cellulose nanocrystals, and 4 g of polyvinyl alcohol were dispersed in 100 mL of deionized water and mixed at 80 °C at a stirring speed of 200 r / min until the polyvinyl alcohol was completely dissolved to obtain a mixed solution;

[0048] (4) adding 2 g of boric acid dropwise to the mixed solution obtained in step (3) and continuing the reaction for 2 h to obtain a double-network cross-linked mixed solution composed of cellulose nanocrystals and boric acid;

[0049] (5) Pour the mixed solution obtained in step (4) into a flat glass mold, and vacuum dry it at 60° C. until the water is completely evaporated to obtain a double-network cross-linked self-healing electromagnetic shielding material.

[0050] As shown in Table 1, the shielding effectiveness and self-healing performance parameters of the double-network cross-linked self-healing electromagnetic shielding materials prepared based on Examples 1 to 5 are shown. The average shielding effectiveness (EMI L ) is between 34dB and 36dB, and the average shielding effectiveness (EMI) in the X-band X ) is between 24dB and 27dB, demonstrating good electromagnetic shielding performance. The resulting shielding material has a repair efficiency (μ) of up to 88% at room temperature, demonstrating excellent self-healing properties.

[0051] Table 1. Electromagnetic shielding and self-healing performance parameters of the composite materials obtained in the examples

[0052] Group Example 1 Example 2 Example 3 Example 4 Example 5 <![CDATA[EMI L (dB)]]> 35 34 36 35 35 <![CDATA[EMI X (GHz)]]> 25 24 26 27 26 μ(%) 85％ 88％ 86％ 87％ 86％

Claims

1. A method for preparing a double-network cross-linked self-healing electromagnetic shielding material, characterized in that: The steps include: (1) Add 10-15 g of LiF to 50 mL of 1 mol / L HCl solution, stir mechanically for 5-15 min, then slowly add the MAX phase, react at 30-40 °C for 24 h, and then centrifuge, wash, and dry to obtain MXene powder; (2) Dispersing 10 mL of pyrrole monomer and 5 to 10 g of the MXene solid powder obtained in step (1) in 50 to 100 mL of ethanol aqueous solution at a volume ratio of 1:1 to prepare a MXene solution, and then adding 10 to 20 g of ammonium persulfate to the mixed solution. After mechanical stirring in an ice bath at 0°C for 12 to 20 hours, the obtained product is filtered, washed, and vacuum-dried at 50 to 60°C to obtain a polypyrrole / MXene composite; (3) dispersing the polypyrrole / MXene composite, cellulose nanocrystals, and polyvinyl alcohol in deionized water, and mixing them at a stirring speed of 200 r / min at 70-90°C until the polyvinyl alcohol is completely dissolved to obtain a mixed solution; (4) adding an appropriate amount of boric acid to the mixed solution obtained in step (3) and continuing the reaction for 1 to 2 hours to obtain a double-network cross-linked mixed solution composed of cellulose nanocrystals and boric acid; (5) Pour the mixed solution obtained in step (4) into a flat glass mold, and vacuum dry it at 50-60° C. until the water is completely evaporated to obtain a double-network cross-linked self-healing electromagnetic shielding material.

2. The method for preparing a double-network cross-linked self-healing electromagnetic shielding material according to claim 1, characterized in that: The MAX phase in step (1) is one or more of Ti3AlC2, Ti2AlC or Ti3AlCN, and has a particle size of ≤200 mesh.

3. The method for preparing a double-network cross-linked self-healing electromagnetic shielding material according to claim 1, characterized in that: In step (3), the ratio of the polypyrrole / MXene composite, cellulose nanocrystals and polyvinyl alcohol is 30-40 parts, 10-20 parts and 40-60 parts, and the solid content of the three in deionized water is 10% to 15%.