The effect of electric field, annealing temperature and filler loading on the percolation threshold of polystyrene containing carbon nanotubes and graphene nanosheets

The electrical resistance of polystyrene sheets containing carbon nanotubes (CNTs) and graphene nanosheets (GNSs) was examined as a function of electric field intensity and annealing temperature. The time needed for the percolation threshold to be reached, decreases with increasing field intensity, annealing temperature and filler loading. However, conductive networks were always formed more easily in GNS composites than did CNT composites. The activation energies for conductive network formation were about 80 and 100 kJ/mol for GNS and CNT, respectively. Structural observations show that the conductive particles could overcome the polymer barrier films and construct a multitude of conducting pathways under the influence of the electric field. A model is proposed to account for the distribution of the different nanofillers in the polymer matrix before and after application of the electric field. The results indicate that the geometry of the nanoparticles greatly affects the ease of formation of conductive networks in polystyrene. (C) 2011 Elsevier Ltd. All rights reserved.