Fabrication of PVC-based composite films with controlled electrical conductivity via delayed phase separation-induced directional distribution of CNT for effective electromagnetic interference shielding

Abstract

Traditional polymer/carbon nanotubes (CNT) composite films, prepared by non-solvent-induced phase separation (NIPS), exhibit low electrical conductivity and poor electromagnetic interference (EMI) shielding effectiveness (SE) due to the random dispersion of CNT within the polymer matrix. In this work, conductive porous polyvinyl chloride (PVC)/CNT composite films were successfully prepared using the NIPS process. The film formation rate was reduced by increasing the concentration of PVC, the concentrations of N,N-Dimethylacetamide (DMAc) in the coagulation bath, and the CNT content, resulting in a oriented distribution of CNT on the film surface and pore walls. The electrical conductivity and EMI SE performance of the composite films were enhanced with increasing CNT content, exhibiting optimal values at proper PVC concentration in the casting solution and DMAc concentration in the coagulation bath. Meanwhile, the effects of casting film thickness, structure, and casting process on EMI SE performance were also investigated. The results demonstrate that EMI SE performance improved by increasing casting film thickness and achieving a multilayer structure through a 1-layer/2-sided casting process. Finally, a PVC/5 wt% CNT composite film prepared by repeating the 1-layer/2-sided casting process three times had an optimal EMI SE value of 32.3 dB. This work provides guidance for the rational design of high-performance polymer-based composite film EMI shielding materials and has great potential in practical applications.