Preparation And Electromagnetic Shielding Prope Rties Of Polymer-Based Mxene Copmposites

Electromagnetic radiation pollution will not only seriously interfere with the normal operation of electronic equipment,but also bring a series of harm to human health.Therefore,with the rapid development of electronic information industry,the research of electromagnetic shielding materials is of great significance.MXene is a new kind of two-dimensional nanomaterials,which can be used as an ideal conductive filler because of its excellent electrical conductivity,mechanical properties and multifunctional chemical properties.The intrinsically conductive polymer polypyrrole(PPy),with its advantages of low density,low cost,high manufacturability and environmental friendliness,shows excellent application prospects in energy storage,electrothermal,sensor and photothermal conversion,especially in the field of electromagnetic shielding.In this paper,polymer-based MXene nanocomposites were designed and prepared based on the interlayer structure of MXene nanosheets,and polypyrrole nanoparticles were grown in situ on MXene nanosheets by chemical oxidation polymerization,so as to study the way and mechanism of improving the electromagnetic shielding performance of polypyrrole.MXene/WPU composite film,MXene/PPy/WPU composite film and MXene/PPy/PP nanocomposites were prepared respectively,and their electromagnetic shielding properties were studied.The main research contents are as follows:(1)Ti3C2Tx MXene nanosheets with few layers were successfully prepared by mixing LiFHCl to prepare HF mild etching.Aqueous polyurethane based on polymer(WPU)was introduced,and MXene/WPU composite films with excellent electrical conductivity and electromagnetic shielding properties were prepared by simple blending and vacuum filtration.WPU can enhance the flexibility of MXene/WPU composite film,and can protect the multi-layer conductive network structure of MXene,so as to improve its environmental stability.At 75 wt%MXene,the conductivity increases to 442.1 S/m,and the EMI SE value in the X-band is 46.7 dB.The electrical conductivity test results show that Ti3C2Tx MXene has excellent electrical conductivity and can be used as an ideal conductive filler in subsequent composites.As a polymer substrate,WPU has the advantages of simple process,high efficiency,strong processability and environmental friendliness.(2)The prepared Ti3C2Tx MXene was selected as a conductive filler,and the MXene/PPy composite was prepared by in-situ growth of PPy on MXene nanosheets by chemical oxidation polymerization;MXene/PPy/WPU composite films were prepared by vacuum assisted filtration by adding WPU as polymer substrate.In MXene/PPy composite material,continuous MXene nanosheets and PPy nanoparticles were alternately stacked to construct a continuous and efficient three-dimensional conductive network structure,and the thermal stability of the material was significantly improved.By changing the addition content of MXene,the conductivity of MXene/PPy/WPU composite film prepared by MXene/PPy composite material with MXene content of 20 vol%was increased to 806.5 S/m,and the maximum EMI SE in the X-band was also increased to 38.5 dB.(3)Using polypropylene(PP)nonwoven fabric as the matrix,after treatment,PPy was synthesized and loaded on the matrix by in-situ chemical oxidation polymerization,and then MXene was impregnated and coated to prepare MXene/PPy/PP nanocomposites with good electrical conductivity and EMI shielding properties.The effect of the concentration of different pyrrole monomer solution on the electromagnetic shielding properties of the composite was studied,and the main electromagnetic shielding mechanism was further analyzed.The EMI shielding efficiency increased with the increase of the concentration of pyrrole monomer solution,from 10.1 dB when the concentration of pyrrole monomer was 0.2 mol/L to 25.2 dB when the concentration of pyrrole monomer was 1.0 mol/L,and the corresponding conductivity increased from 6.2 S/m to 20.6 S/m.In this chapter,MXene/PPy/PP nanocomposites were prepared by simple in situ oxidation polymerization and impregnation,which expanded the application of MXene/PPy composites in practice and provided a new design idea and method for preparing polymer-based MXene nanocomposites.