Effect of filler treatment on temperature dependence of resistivity of carbon-black-filled polymer blends

Polyblends prove to be able to provide more possibilities for tailoring conductive polymer composites in comparison with individual polymer systems. Accordingly, ethylene–vinyl acetate—low-density polyethylene (EVA–LDPE) filled with carbon black (CB) was prepared in this study as a candidate for positive temperature coefficient (PTC) material. In consideration of the fact that CB distribution plays the leading role in controlling a composite's conduction behavior, chemical treatment of CB was applied to reveal its influence on percolation and the PTC effect. It was found that titanate coupling agent treatment facilitated sufficient distribution of CB in LDPE phase, leading to lower resistivity and a squarer PTC curve. Composites filled with nitric-acid-treated CB exhibited specific temperature dependence of resistivity as a result of the heterogeneous dispersion of CB at the interface of EVA–LDPE, which might provide the materials with a new function. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 489–494, 1999