Positive Temperature Coefficient Behavior of HDPE/EVA Blends Filled with Carbon Black
The electrical resistivity and positive temperature coefficient (PTC) behavior of carbon black (CB)-filled high density polyethylene (HDPE) /ethylene-vinyl acetate copolymer (EVA) composites were investigated. At any particular CB content, the composite with the HDPE/EVA weight ratio 9/1 showed the lowest resistivity compared to other composites under investigation. The resistivity was decreased after the addition of small amount of EVA in HDPE with a particular CB loading. This is due to the improvement in dispersion of CB in HDPE in presence of small amount of EVA. However, the resistivity was again increased after the addition of higher amount of EVA due to the formation of an insulation polymer shield by EVA around CB particles. The nature and intensity of PTC was dependent on the HDPE/EVA ratio. With the increase in EVA content, PTC was shifted at a lower temperature. The highest PTC intensity was observed for the composite with HDPE/EVA ratio 8/2.
Yansheng Yin and Xin Wang
Q. Li et al., "Positive Temperature Coefficient Behavior of HDPE/EVA Blends Filled with Carbon Black", Advanced Materials Research, Vols. 79-82, pp. 2267-2270, 2009