Deformation and toughening mechanism for high impact polystyrene (HIPS) by pressure-induced-flow processing

In this paper, firstly, we systematically explain the deformation mechanism of the high impact polystyrene (HIPS) via pressure-induced-flow (PIF) processing. As indicated by TEM, AFM and SAXS, we find that a single salami domain is intensively deformed into a disk-like shape, and rubber-disk domains form parallel and oriented structure. In addition, chains in the interphase are oriented and become stiffer as suggested by FTIR and DMA. Such structural variation gives rise to the improvement in both strength and toughness. Impact and tensile strength for high impact polystyrene (HIPS) with parallel and oriented structure increase by 100% and 30% respectively. Moreover, we studied the toughening mechanism. The post-impact fracture surface transits from normal smooth fish scale like morphology to aligned grooves with high roughness, as demonstrated by SEM. The craze of impact fracture surface of HIPS samples after PIF processing is characterized by TEM. Finally, a model for the confinement of crazing is proposed.