Fracture behaviour of high impact polystyrene Influence of particle morphology

The mechanical behaviour of high impact polystyrene has been examined with special attention to the influence of particle size and morphology. Video extensometry was used to follow the volume strain kinetics during tensile drawing and also to make direct observations of crack initiation in compact tension experiments at moderate rates. Materials incorporating composite particles with either small capsule (0.3 µm) or large salami (>1 µm) structures have been considered, as well as blends combining both morphologies. In the particular case of blends, a marked synergistic behaviour was achieved under impact conditions. Plasticity and fracture results, as well as morphological observations, suggest that the ability of the salami particles to stabilise the crazes initiated by the small capsules plays a key role, even at small volume fractions of salami particles.