DIELECTRIC-PROPERTIES OF BLENDS OF POLYCARBONATE AND ACRYLONITRILE-BUTADIENE-STYRENE COPOLYMER

The low frequency dielectric properties of polymeric blends of polycarbonate (PC) and acrylonitrile-butadiene-styrene (ABS) were studied in the temperature interval of 100 to 170-degrees-C. Attention was focused on a 60/40 (m/m) PC/ABS blend. The results were compared with dynamic mechanical measurements in torsion and with the results of a morphological investigation using scanning electron microscopy (SEM). Besides the relaxations at the glass transition temperatures of the components an additional strong low frequency dielectric dispersion was observed, which was not found in mechanical measurements. This low frequency polarization process is due to interfacial polarization at the boundaries between conductive ABS and non-conductive or slightly-conductive PC. It is shown how this process can be described by the dielectric models for two-phase heterogeneous materials. The Looyenga model offers the best description of the detected effects, while the Hanai model is less suitable. The shape factor of the ABS phase as used for modeling the dielectric properties agrees well with the observed morphology using SEM. It is shown for the dielectric measurements on the 75/25, 60/40, and 45/55 (m/m) PC/ABS blends how the connectivity of the ABS phase can be sensitively derived from the electrical conductivity of the blend. whereas mechanical measurements are highly sensitive to the connectivity of the PC phase.