Electrical properties of non-crosslinked polyethylene/syndiotactic polystyrene composites filled with carbon black

Carbon black (CB)-filled high density polyethylene (HDPE)/syndiotactic polystyrene (sPS) composites were prepared by the conventional melt-mixing procedure. The effect of the HDPE/sPS weight ratio, CB content and processing speed on the thermoelectric behavior such as positive temperature coefficient (PTC) and negative temperature coefficient (NTC) was investigated in detail. The non-crosslinked HDPE/sPS composites containing 10-phr CB, a typical PTC behavior was observed when the temperature increased toward the melting point of HDPE. At high processing speed, the composites exhibited high room temperature resistivity and high PTC intensity. In a high sPS content composite, the dispersion of sPS particles are homogeneous and the distance of sPS particles are very close. The CB-coated sPS particles could be formed a continuous conductive network; therefore the PTC effect became weaker and weaker in these systems. The elimination of the NTC effect in CB-filled composites can be achieved by using a very high melting semicrystalline polymer as one of its components.