The elastomer particle cavitation in the deformation mechanism of high impact polystyrene (HIPS)

The role of rubber particles in the deformation of toughened polystyrene was investigated by studying the mechanical behaviour of HIPS submitted to γ-irradiation up to 80 Mrad. This induced cross-linking of the rubber as verified by dynamic mechanical thermal analysis and swelling index determinations. The irradiated HIPS showed increased yield strain and lower strain at break while impact strength decreased. The influence of irradiated PS in this behaviour was shown to be negligible. The main effect was to increase shear modulus G of elastomer thereby making it more resistant t cavitation and fibrillation. In fact, TEM micrographs of tensile tested and highly irradiated specimens did not show matrix crazing and rubber particle cavitation. As G increased, volume strain at which cavitation occurred must have increased, in agreement with Lazzeri and Bucknall's cavitation model but, also, the strain hardening effect of fibrillated rubber must have been enhanced. (author). 10 refs., 3 figs