Microwave‐Assisted Confining Flame‐Retardant Polypropylene in Carbon Nanotube Conductive Networks for Improved Electromagnetic Interference Shielding and Flame Retardation

Electrical conductive polymer composites (CPCs) with segregated structure can achieve better electrical conductivity with low content of conductive filler. Nevertheless, the undesirable properties of these CPCs, such as ease of burning, high smoke generation, weak interfacial adhesion, and poor mechanical performance, have restricted their practical applications. Herein, a promising microwave‐assisted strategy is developed for the fabrication of a flame‐retardant and electrically conductive polypropylene/ammonium polyphosphate/carbon nanotube (PP/APP/CNT) composite. Highly conductive networks can be set via the microwave‐selective heating, which results in an electromagnetic shielding effectiveness (EMI SE) of 32.1 dB of the composite with 7 wt% content of CNTs. Furthermore, the conductive segregated CNT network also serves as an excellent char‐forming agent to enhance the nonflammability and overcome the melt dripping issue of the pure PP matrix. As a result, the segregated conductive PP composites with 7 wt% CNTs and 15 wt% APP exhibit melt dripping and prompt self‐extinguishment, achieving the V‐0 rating level in the UL‐94 test. In brief, the well‐defined microwave‐assisted process provides a promising approach to fabricate various CPCs with simultaneously improved EMI shielding and flame‐retarding properties.