Effect of coefficient of thermal expansion on positive temperature coefficient of resistivity behavior of HDPE-Cu composites

摘要

Positive temperature coefficient of resistivity (PTCR) characteristics of (high density polyethylene) HDPE-Cu composites has been investigated with reference to the conventional HDPE-CB (carbon black) composites. Plot of resistivity against temperature of HDPE-CB composites showed a sudden rise in resistivity (PTC trip) at 127°C, close to the melting temperature of HDPE. However, the PTC trip temperature (98°C) for HDPE-Cu composites was appeared well below the melting temperature of HDPE. Addition of 1 phr nanoclay in the composites resulted in an increase in PTC trip temperature of HDPE-Cu composites, whereas no significant effect of nanoclay on PTC trip temperature was evident in case of HDPE-CB-clay composites. We proposed that the PTC trip temperature in HDPE-Cu composites was governed by the difference in coefficient of thermal expansion (CTE) of HDPE and Cu. The room temperature resistivity and PTC trip temperature of HDPE-Cu composites were very much stable upon thermal cycling. DMA results showed higher storage modulus of HDPE-Cu composites than the HDPE-CB composites. Thermal stability of HDPE-Cu composites was also improved compared to that of HDPE-CB composites.