Study on Effect of Carbon Black on Behavior of Conductive Polymer Composites with Positive Temperature Coefficient
Abstract
Conductive polymer composites showing large positive
temperature coefficient (PTC) are made of semi-crystalline
polymer as an insulator and a conducting filler, whose concentration
is close to the critical volume fraction. In this study, the resistivity
and PTC behavior of high density polyethylene (HDPE)
filled with different carbon blacks were studied. Among those composites,
N660 carbon black filled PE showed the greatest PTC behavior.
Carbon black with large particle size, small surface area
and small amount of aggregated structure leads to large amplitude
of PTC transition (defined as the ratio of maximum resistivity to
the resistivity at 25 ℃). The great PTC behavior is due to some microscopic
mechanism under the macroscopic thermal expansion of
polymer matrix during melting of polymer crystal.