Electrical properties and thermal oxidative aging stability on the Eva/Silica nano composites using EVAgMA compabilizer

Abstract

The ternary nanocomposites based on ethylene-vinyl acetate copolymer (EVA, 18 % vinyl-acetate group) without and with lwt.% of EVAgMA (EVA - grafted - maleic anhydride) and 2-5 wt.% of nanosilica were prepared by melt mixing in a Haake intermixer at 160 °c, roto speed of 50 rpm for 5 minutes. The volume resistivity, dielectric breakdown and dielectric loss of the nanocomposites were measured in according to ASTM D257, D149 and D150, respectively. The nanocomposites were tested in a hot air circulating oven at 70°c for 168 hours to investigate thermal oxidation aging stability. The obtained results showed that nanosilica decreased volume resistivity and dielectric loss of the nanocomposites but it increased dielectric breakdown of EVA. The dielectric constant of the EVA/EVAgMA/silica nanocomposites is lower than that of the EVA/silica nanocomposites. The EVA/silica nanocomposites without and with EVAgMA are good electrical insulation materials (volume resistivity in the range of 1013 - 1014 Q.cm, dielectric loss of about 10-3 and dielecftic breakdown in the range of 22.1 - 26.7 kv/nun). The percentage of retention in mechanical properties of the EVA/EVAgMA/silica nanocomposites is higher than that of EVA. FTIR analyses of the nanocomposites before and after thermal oxidation aging indicated that nanosilica and EVAgMA limited to degradate EVA macromolecules.