Sandwich structured iPP/CNTs nanocomposite foams with high electromagnetic interference shielding performance

Polymer-based nanocomposite foams with high electrical conductivity are promising alternatives to traditional metal materials in the field of electromagnetic interference (EMI) shielding due to their advanced properties. Herein we prepared nanocomposite foams based on isotactic polypropylene (iPP) and carbon nanotubes (CNTs), using a facile melt blending process combining with an environment friendly physical foaming method. A foamed iPP/CNTs nanocomposites sandwich structure is obtained by utilizing the varied viscoelastic properties of the iPP/CNTs blends with different CNTs contents, under a given foaming temperature schedule. The manufactured sandwich structure possesses a micro-foamed core layer (low CNTs content) and nano-foamed skin layers (high CNTs content), which can provide a synergistic effect on the EMI shielding performance. A total electromagnetic shielding effectiveness of 38.0 dB for the foamed iPP-10CNTs/iPP-3CNTs/iPP-10CNTs was achieved, of which 84.5% was found to be attributed to the absorption mechanism, leading to a superior EMI shielding performance, with respect to either the single layered microcellular foams or their solid counterparts.