Dynamic percolation phenomenon of poly(methyl methacrylate)/surface fluorinated carbon black composite

The electrical resistivity of polymer filled with conductive filler, such as carbon black (CB) particles, is greatly decreased by incorporating the conductive filler. This is called the percolation phenomenon and the critical CB concentration is called the percolation threshold concentration (Phi*). For CB particle-filled insulating polymer composite at lower than Phi*, the conductive CB network is constructed in the polymer matrix when the composite is maintained at a temperature higher than the glass-transition temperature or the melting temperature of the polymer matrix. This phenomenon is called dynamic percolation and the time to reach the substantial decrease in resistivity is called percolation time (t(p)). To investigate the relationship between the dynamic percolation process and the surface state of CB particles, we used three kinds of carbon black particles such as original carbon black (CB0) and fluorinated carbon black (FCB010 and FCB025)-filled poly(methyl methacrylate) (PMMA). It was observed that the dynamic percolation curves for CBO-filled PMMA and FCB-filled PMMA composites shifted to a shorter percolation time with increases in both the annealing temperature and the filler concentration. However, the dynamic percolation curves of FCB-filled PMMA showed a gradually decreasing trend compared to that of CB0-filled PMMA composites. The activation energy calculated from an Arrhenius plot of the t(p) against the inverse of the annealing temperature was decreased by surface fluorine treatment. (C) 2003 Wiley Periodicals, Inc.