Study on the Microstructure of EPDM/NBR Blend by Positron Annihilation Spectroscopy

Abstract

Positron annihilation lifetime and Doppler broadening of annihilation radiation techniques were employed to investigate the relationship between free-vol ume hole properties and miscibility of ethylene propylene diene monomer (EPDM)/acrylonitrile butadiene rubber (NBR) blends. It has been found that there were positive and negative deviations in free-volume hole size (s3) and concentration (I3) as well as S-parameter from linear rela tionship of initial polymers indicating the immiscibility of the blend. The broadening in free-volume hole distribution by increasing NBR content in EPDM/NBR blend confirm the results obtained by finite term analysis. From the fill ing effect of silica on free-volume properties of EPDM/ NBR (75/25) blend, it has been found that the addition of silica up to 50 phr is the most promising concentration for electrical application. Furthermore, correlations were established between free-volume hole size and fraction com bined with the results of electrical (dielectric constant and dielectric loss) and mechanical (stress at yield and strain at yield) properties.