Abstract
Thermal expansion behavior defined as the percentage of dimensional change upon heating for the blend systems of polystyrene/polyethyleneterephthalate has been investigated in this study. General purpose polystyrene (PS) and high impact polystyrene (HIPS) were blended with polyethyleneterephthalate (PET) at a weight ratio of (15/85). The dimensional change of the neat and blended polymers versus temperature is measured by a thermomechanical analyzer using an expansion probe. The study investigates thermal expansion behavior of the PS/PET and HIPS/ PET blend systems under various conditions of heating rate, load, and heating regime. Higher thermal expansion values for the neat polymers and the blends were observed at lower heating rate, i.e., 5°C/min, while increasing load did not seem to affect thermal expansion behavior of the materials except for neat PET and HIPS/ PET blend system at higher temperature range, i.e., beyond Tg of PET and near softening temp of HIPS, where thermal expansion values decreased as load increased. Neat polystyrenes exhibited noticeable thermal expansion and contraction behavior when tested isothermally. The blend systems formulated and tested in this study, which consisted 15/85 wt% of both PS/PET and HIPS/PET, have proven to be more thermally stable and have better thermal expansion behaviors in both heating regimes used, i.e., nonisothermal and isothermal, than those behaviors observed for the neat polymers especially the minor phase, i.e., the polystyrenes.