Electromagnetic shielding of ultrathin, lightweight and strong nonwoven composites decorated by a bandage-style interlaced layer electropolymerized with polyaniline

The electromagnetic shielding materials with characteristics of ultrathin, lightweight and high strength are the most advantageous materials in electromagnetic shielding. In this work, novel carbon fiber nonwoven composites with interlayer microstructure were designed and prepared. Due to their special structure, carbon fiber nonwoven composites coated with polyaniline by means of electropolymerization showed excellent electromagnetic shielding (65 dB) and mechanical properties (bending strength of 457 MPa). More intriguing, the absolute SE (Shielding Effectiveness) of the composites can be as high as 3904 dB.cm²/g. In order to explore the elementary mechanisms of electromagnetic loss, the relevant calculation of electromagnetic shielding effectiveness was carried out. The experimental and theoretical results show that the reflection is the dominant shielding performance of the carbon fiber nonwoven composites. However, with the increase of electropolymerization time, the absorption loss was enhanced and the reflection was weakened, which was caused by the conductive polyaniline network structure covered on the nonwoven fiber surface. Based on the comparison between experimental results and theoretical calculation, the effect of multiple reflection loss on the total electromagnetic shielding performance was improved, and the loss mechanism of multiple reflection was analyzed in detail. Moreover, the surface roughness of fiber and the formation of polymerization products by electropolymerization could effectively enhance the interfacial strength between carbon fiber nonwoven and epoxy, which observably increased the bending strength by 83%.