Positive temperature coefficient characteristic and structure of graphite nanofibers reinforced high density polyethylene/carbon black nanocomposites

Graphite nanofibers (GNF) and carbon black (CB) filled high density polyethylene (HDPE) hybrid composites were fabricated using a melt mixing method. The effects of the CB and GNF content on the room temperature resistivity and positive temperature coefficient (PTC) behavior of the nanocomposites were examined. The room temperature resistivity of the composites decreased significantly with increasing GNF content, but this was not always the case with the PTC intensity. The incorporation of a small amount of GNF into the HDPE/CB composites significantly improved the PTC intensity and reproducibility of the hybrid nanocomposites. The maximum PTC effect, whose log intensity was approximately 7.2, was observed in the HDPE/CB/GNF (80/20/0.25 wt%) nanocomposite with relatively low room temperature resistivity. The mechanism for the effects of GNF in HDPE/CB/GNF hybrid composites were examined using differential scanning calorimetry, transmission scanning electron microscopy and X-ray diffraction.