The resistivity and volume expansion of carbon black (CB)/high-density poly
ethylene (HDPE) composite with different CB volume fractions at different t
emperatures were measured simultaneously. A model based on Meyer's theory i
s proposed to explain the positive temperature coefficient resistance (PTCR
) effect. The relationship between resistivity and volume expansion was det
ermined. It was found that the phase change is the main cause of the PTC ef
fect in the crystalline polymer PTC materials. (C) 2000 John Wiley & Sons,
Inc.