Effect of Nanoclay on Positive Temperature Coefficient to Resistivity Characteristics of High Density Polyethylene/Silver-Coated Glass Bead Composites

摘要

Positive temperature coefficient to resistivity characteristics of high density polyethylene (HDPE)/silver (Ag)-coated glass bead (45 wt%) composites, without and with nanoclay, has been investigated with reference to HDPE/carbon black (CB) (10 wt%) composites. Plot of resistivity versus temperature of HDPE/CB (10 wt%) composites showed a sudden rise in resistivity (PTC trip) at≈128°C, close to the melting temperature (T_m) of HDPE. However, for HDPE/Ag coated glass bead (45 wt%) composites, the PTC trip temperature (≈88°C) appeared well below the T_m of HDPE. Addition of 1 phr clay in the composites resulted in an increase in PTC trip temperature of HDPE/Ag-coated glass bead (45 wt%) composites, whereas no significant effect of clay on PTC trip temperature was evident in HDPE/CB/ clay composites. We proposed that the PTC trip temperature in HDPE/Ag-coated glass bead composites was governed by the difference in coefficient of thermal expansion of HDPE and Ag-coated glass beads. The room temperature resistivity and PTC trip temperature of HDPE/Ag-coated glass bead (45 wt%) composites were found to be very stable on thermal cycling. Dynamic mechanical analyzer results showed higher storage modulus of HDPE/Ag-coated glass bead (45 wt%) composites compared with the HDPE/CB (10 wt%) composites. Thermal stability of HDPE/Ag-coated glass bead (45 wt%) composites was also improved compared with that of HDPE/CB (10 wt%) composites.