Simultaneous enhancement of electrical conductivity and shape memory behavior of polystyrene/ethylene octene copolymer blend nanocomposites by CNTs through double percolation

Abstract

The purpose of this paper is to investigate the effects of carbon nanotube (CNT) addition on the morphology as well as mechanical and electrical and shape memory properties of immiscible polystyrene/ethylene octene copolymer (PS/EOC) blends prepared by melt compounding. To prepare PS and EOC blends, weight percent of 80/20 and 50/50, different amounts of CNTs were varied between 0.05 and 1.5 phr. An investigation of the morphology of the PS/EOC blends using scanning electron microscopy revealed that when CNTs are added, the morphology of the blends changes from matrix-droplet to co-continuous. Based on the rheological results, blend nanocomposites exhibited solid-like behavior at low frequencies due to the formation of the 3D network of CNTs in mainly the PS phase. According to the electrical conductivity measurement, the electrical percolation thresholds for PS/EOC (80/20) and (50/50) samples were as low as 0.15 and 0.25 phr, respectively. Through the double percolation phenomenon, the electrical conductivity increased by 9 orders of magnitude by adding only 1.5 phr CNTs. Also, the shape fixity and recovery of PS/EOC/CNT (50/50/1.5) nanocomposite reached 100 % mainly contributed to increased interfacial elasticity and CNTs’ 3D network formation. The results showed that this method can be applied to produce materials with desirable electrical conductivity, shape memory, and mechanical properties.