STATIC AND DYNAMIC ELECTRICAL BREAKDOWN IN CONDUCTING FILLED-POLYMERS

The electrical resistance of a percolating medium- made of A polymer f illed with conductive particles may undergo a steep increase over a na rrow temperature range above room temperature. A likely mechanism for the effect is the loss of interparticle contact inducing a weakening o f the connectivity of the medium as temperature is increased. When Jou le heating is used, the sample behavior depends strongly on whether a tension or current source is used. We show that in the first case, at any value of the voltage drop across the sample, a stable state is rea ched; on the contrary when a convenient exciting current is used, the sample resistance may diverge spontaneously with time. We demonstrate that most of these behaviors are compatible with the predictions of a random thermal fuse model.