Onset of Electrical Percolation in Onion-Like Carbon/Poly(methyl methacrylate) Composites

The results of broadband dielectric spectroscopy of onion-like carbon (OLC) based Poly(methyl methacrylate) (PMMA) composites are reported in wide temperature range 300-450 K. The dielectric properties of OLC/PMMA composites are chiefly dependent on the preparation technique, in particular annealing above the glass transition temperature of composite with 20 wt.% of OLC inclusions causes the vanishing of β relaxation, electrical conductivity appearance and onset of percolation. The percolation threshold in OLC/PMMA composites is found to be close to 20 wt.%. Below the percolation threshold the dielectric properties of composites in temperature range 300-420 K are determined mainly by β relaxation. The activation energy of such a relaxation is weakly dependent on OLC concentration.