STRUCTURAL RELAXATION AROUND THE GLASS-TRANSITION TEMPERATURE IN AMORPHOUS POLYMER BLENDS - TEMPERATURE AND COMPOSITION DEPENDENCE

The thermally stimulated depolarization current technique has been used to study the relaxation behaviour in solvent-cast blends of poly(vinyl chloride) (PVC) and acrylonitrile-butadiene-styrene (ABS). The effects of the forming conditions (field, temperature and time) on depolarization have been investigated. The data on blends with components in various weight ratios indicate that the blends are not compatible enough to show one relaxation peak and the 40-60 PVC/ABS blend shows the greatest depolarization current. The blends show two relaxation processes corresponding respectively to the glass transitions of PVC and ABS. Partial polarization and peak-cleaning techniques have been used to obtain both alpha peaks as a function of blend composition. Curve fitting was carried out and the activation energy E(a) and the pre-exponential factor tau0 were calculated. The data have been used for investigations of relaxations that obey an Arrhenius-like law. Analysis of the data shows that it is possible to study the relaxation behaviour in this system, which was found to be controlled by the free-volume mechanism described by the Williams-Landel-Ferry equation.