Optical and electrical characterization of gamma irradiated low density polyethylene/paraffin wax blend

Abstract

Blends of LDPE/wax in ratios of 100/0, 98/2, 96/4, 94/6, 92/8, 90/10 and 85/15 (w/w) were prepared by melt-mixing method at the temperature of 150 °C. It was found that increasing the wax content more than 15% leads to phase separation. Optical and electrical properties of pure LDPE, pure paraffin wax and LDPE/paraffin wax blends were studied before and after gamma irradiation. The optical band gap (Egopt) and Urbacht energy (Eu) in the LDPE/paraffin wax blends were determined. The results show a decrease in Egopt and increase in Eu by increasing paraffin wax ratio. The transition energy for electrons is an allowed indirect. The electrical properties including dielectric constant (ε'), dielectric loss (εʺ) and the ac conductivity (σac) in the frequency range (50 KHz–1 MHz) at room temperature were investigated. ε′, εʺ and σac increase with increasing paraffin wax ratio. ε′ and εʺ values are higher at low frequencies, while at high frequencies the trend is reversed. Influence of gamma radiation on the optical and electrical properties for the pure samples and LDPE/paraffin wax blends has been evaluated at different gamma irradiation doses (25 kGy, 50 kGy and 75 kGy). It was found that Egopt decreases, while Eu increases with increasing irradiation dose. Also, we report an increase in ε′, εʺ and σac with increasing irradiation dose. The results of the optical and electrical characteristics indicate a relation between the amorphous nature of the samples and electrical conductivity.