Electrical Conductivity and Rheological Behavior of Multiphase Polymer Composites Containing Conducting Carbon Black

Multiphase polymer composites of carbon black (CB), polypropylene (PP) and low density polyethylene (LDPE) were prepared by melt-mixing method to reduce the amount of CB in the conductive composites. SEM images showed that CB preferably located in LDPE phase and formed electrically conductive path. The measurement of conductive properties showed that the ternary materials possessed lower percolation than binary composites of CB/PP or CB/LDPE, the former was similar to 6 wt% and the latter was 9-10 wt%. Positive temperature coefficient (PTC) effects of the binary and ternary composites were investigated, indicating that the latter exhibited a relatively high PTC intensity. A rheological percolation estimated by a power law function is 2.66 wt% of CB loading, suggesting an onset of solid-like behavior at low frequencies. This difference between the electrical and rheological percolation thresholds may be understood in terms of the smaller CB-CB distance required for electrical conductivity as compared with that required to impede polymer mobility. POLYM. ENG. SCI., 48:2090-2097, 2008. (C) 2008 Society of Plastics Engineers