Effect of interphase interactions on the dielectric behaviour of polycarbonate/poly (styrene-co-acrylonitrile) blends

Frequency and temperature dependences of the complex permittivity epsilon* (= epsilon' - i epsilon ", epsilon' is the real and epsilon " imaginary com ponent, respectively) were investigated for blends of polycarbonate/poly(st yrene-co-acrylonitrile) (PC/SAN). In the blends, two alpha-processes corres ponding to the main transitions of PC and SAN were found; for SAN at concen trations c(SAN) greater than or equal to 20 wt% and for PC for c(PC) greate r than or equal to 40 wt%. The Havriliak-Negami shape parameters describing the frequency dependence of epsilon' and epsilon " are virtually independe nt of temperature and composition. Slight shift of temperature or frequency positions of alpha-processes found for blends from those found for neat po lymers with composition of blends indicated partial miscibility of componen ts. The concentration dependences of epsilon and epsilon " at low frequenci es and high temperatures could be described with the Bottcher equation from which it followed that percolation threshold takes place for SAN inclusion s at c(SAN) = 30 Wt%. Both the reduced dielectric strength Delta epsilon T and the reduced Onsager term O-t/c(SAN): (or O-t/c(PC)) in dependence on th e blend composition could be qualitatively described by the Bottcher equati on as well.