The study of stress-yielding of aged atactic polystyrene (a-PS) by differential scanning calorimetry

Full Paper: The stress-yielding mechanism of-aged atactic polystyrene (a-PS ) was studied by differential scanning calorimetry (DSC) and solvent-swelli ng measurements and the viewpoint of cohesional entanglement (CE) was appli ed to interpret the observations. The results indicated that the yielding, as well as the solvent- swelling of aged a-PS were in essence the processes to break the CE points, generated by the aging at temperatures below a-PS' s Tg. In these cases, the break up of CE was manifested by the decrease of disappearance of the stress-induced yielding peak in the stress-strain curv e (sigma-epsilon curve) and that of the endothermic peak near the Tg temper ature range of DSC scanning. sigma-epsilon curves of quenched a-PS aged at 85 degreesC for different per iods of time. a) 0 h; b): 5 h; c) 20 h; d) 50 h; e): 100 h and f) 300 h. [GRAPHICS]