THERMAL-BEHAVIOR OF HYDROSTATICALLY EXTRUDED POLYCARBONATE AND HIGH-IMPACT POLYSTYRENE

Effects of hydrostatic extrusion on the thermal properties of polycarb onate (PC) and of high-impact polystyrene (HIPS) were studied using di fferential scanning calorimeter (DSC) measurements. A glass transition temperature (T-g) and a peak temperature were determined from the DSC curves for both PC and HIPS extrudates. The T-g values of the PC extr udates, with a percentage reduction in area, R, from 40 to 50%, change appreciably from the value for the as-received PC. The results of the hydrostatic extrusion of the PC billets suggest that a two stage defo rmation process of molecular chains may be involved. Shear-banding is observed for HIPS extrudates with R = 30 to 60%; this fact indicates t hat a sub-glass transition (beta-transition) occurs at temperatures be low T-g. It is suggested that the molecular chains of the HIPS extruda te with R = 70% are oriented in the direction of hydrostatic extrusion . The deformation mechanism of molecular chains caused by the hydrosta tic extrusion is discussed.