MECHANISTIC AND CONTINUUM ASPECTS OF TOUGHNESS IN HETEROGENEOUS POLYMERS

ABSTRACT Brittle glassy polymers can be very effectively toughened by the incorporation of compliant particles which can be made to act as potent sites of craze initiation. These crazes, as dilatational transformations, can result in very substantial plastic strains. The potency of the particles depends strongly on their morphology, which can be modified effectively by blending block copolymers with low molecular weight rubber. To be effective, the particles must have a stress-induced displacement misfit greater than the thickness of a mature craze. Terminal craze fracture is most often due to separation of entrapped inorganic impurity particles that get incorporated into thickening crazes.