Physico-chemical properties of low density polyethylene and ethylene vinyl acetate composites cross-linked by ionizing radiation

Conductive polymers consisting of low density polyethylene (LDPE), ethylene vinyl acetate copolymer (EVA) and carbon black (CB) were prepared by melt mixing. LDPE/CB, EVA/CB and LDPE/EVA/CB composites were irradiated by electron beam over the range 50–200 kGy. The effect of CB content, CB type, content of the EVA and irradiation dose on the physico-chemical properties (gel content, volume resistivity, mechanical and thermal properties) was investigated. The gel content increased as a function of both increasing irradiation dose and CB content, and a significant improvement in the mechanical properties (tensile strength and elongation at break) was observed. By increasing the CB content, the volume resistivity dropped by several orders of magnitude. Thermogravimetric analysis parameters including onset temperature (Ti, °C), differential thermogravimetric peak temperature (DTG, °C) and temperatures at 50% and 95% weight losses were investigated. Thermal stability of the conductive composites was enhanced by addition of either CB or EVA and the degree of enhancement was correlated to their contents. The melt flow index decreased with incorporation of CB leading to more viscous matrix.