Study on poly (ethylene-co-vinyl acetate), acrylonitrile butadiene copolymer, and their blend reinforced with carbon black using position annihilation lifetime spectroscopy

Abstract

Positron annihilation lifetime spectroscopy (PALS) have been used to investigate the effect of filling each of poly (ethylene-co-vinyl acetate) (EVA), acrylonitrile butadiene rubber (NBR), and their blend (50/50wt-%) with different concentrations of high-abrasion furnace (HAF) (0–60 phr). PALS is characterised by the free-volume parameters (Vh and F %), which is a measure of the size and fraction of free-volume holes in the composites. The results show that the variation in Vh and F % of free-volume holes depends on the chemical structure and the degree of crystallinity of each polymer. The NBR has a smaller size (127.78 Å3) and lower fraction (4.18%) of free-volume holes than the corresponding free-volume holes (177.48 Å3 and 7.03%) in EVA. The size of the free-volume holes increases in EVA with increasing HAF content up to 20 phr in polymer matrix while it decreases in NBR. The fractions (F %) of free-volume holes decrease due to the reduction in positronium formation in polymer and positron trapping at polymer interface. The results also show an inverse correlation between free-volume parameters (Vh and F %) and tensile strength value, and a direct correlation with elongation at break as a function of HAF content in EVA and NBR. The electrical properties are negatively correlated with lifetime of free positron, τ2, and positively with its relative intensity (I2).