Rheological and electrical percolation thresholds of carbon nanotube/polymer nanocomposites

Abstract

Abstract Percolation thresholds of multiwalled carbon nanotube/polystyrene (MWCNT/PS) nanocomposites (NC) were determined by rheology and electrical conductivity. The percolation threshold found by electrical conductivity was 0.5% carbon nanotubes (CNT) and that by mechanical spectroscopy and relaxation measurements was 0.9% CNT. These results together with those reported in the literature show several types of percolation thresholds, depending on the average filler–filler (CNT and/or aggregates) distance in a polymer matrix. A distance close to polymer gyration radius corresponds to a “soft” rheological threshold ( P C rheo soft ). Close contacts between fillers giving rise to a conductive path corresponds to an electrical threshold ( P C elec ). At high filler concentration, fillers form a network, corresponding to a “rigid” rheological threshold ( P C rheo rigid ). These thresholds depend on the filler content and follow the order: P C elec soft < P C elec < P C rheo rigid . POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers