Engineered polyamide 66-based composites towards superior electrical conductivity and enhanced toughness

Polyamide 66 (PA66)-based composites with ultra-high conductivity and low percolation threshold as well as enhanced toughness were fabricated via facile melt blending and supercritical CO₂ foaming. The tensile tests confirmed the optimal polypropylene (PP) content of 20 wt% in “sea-island” structured PA66/PP blends to guarantee the structural integrity of the PA66 phase. The conductivity measurements manifested that adding PP lowered the percolation threshold of the composites to 4.1 vol% and simultaneously increased the maximum conductivity to 62.1 S/cm, demonstrating superior conductivity performance related to most previously reported PA-based CPCs. The significant enhancement in conductivity could be mainly ascribed to the selective location of CNT in the composites and the changes in crystallization behavior induced by PP introduction. Additionally, PP incorporation improved the tensile toughness of the PA66/PP/CNT due to the interfacial compatibility of maleic anhydride-grafted PP. Thereafter, the microcellular architecture was successfully integrated into PA66/PP/CNT composites through supercritical CO₂–assisted foaming technique, enabling simultaneous attainment of weight reduction and toughness enhancement as well as remarkably reduced percolation threshold and elevated the conductivity of the composites at low CNT loading. This work offers an in-depth insight into the architectural design for high-performance CPCs with light weight, high conductivity and good toughness.