Abstract
The present study focuses on finding a correlation between the positron annihilation parameters in silicone rubber based on Poly dimethyl siloxane (PDMS) composites loaded with different conductive fillers and their swelling and electrical properties. Four types of conductive fillers have been used in this study: carbon black, graphite, copper, and nickel powders. The maximum degree of swelling Q(m) %, the penetration rate, P, as well as the diffusion coefficient, D, decrease with increasing the filler content due to the reduction of the size of free volume, as observed through a decrease of the probability of ortho-positronium (o-Ps) formation I-3 and the o-Ps lifetime tau(3), representing the size of free volume measured by the positron annihilation lifetime technique (PAL). The electrical conductivity ln (sigma) is positively correlated with the probability of free annihilation of positrons at interfaces I-2, thus suggesting an increase in the electron density with the filler content. The activation energy of conduction, E-a, is found to decrease with the increase in the loading of conductive filler and the particle size of the filler. A correlation between the free-volume V-f, and the d.c. electrical conductivity ln (sigma) is found to be in accordance with Miyamoto and Shibayma model of ion conduction.