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

The thermally stimulated depolarization current technique has been use d to study the relaxation behaviour in solvent-cast blends of poly(vin yl chloride) (PVC) and acrylonitrile-butadiene-styrene (ABS). The effe cts of the forming conditions (field, temperature and time) on depolar ization have been investigated. The data on blends with components in various weight ratios indicate that the blends are not compatible enou gh to show one relaxation peak and the 40-60 PVC/ABS blend shows the g reatest depolarization current. The blends show two relaxation process es corresponding respectively to the glass transitions of PVC and ABS. Partial polarization and peak-cleaning techniques have been used to o btain both alpha peaks as a function of blend composition. Curve fitti ng was carried out and the activation energy E(a) and the pre-exponent ial factor tau0 were calculated. The data have been used for investiga tions of relaxations that obey an Arrhenius-like law. Analysis of the data shows that it is possible to study the relaxation behaviour in th is system, which was found to be controlled by the free-volume mechani sm described by the Williams-Landel-Ferry equation.