Crazes suppression mechanism

From the discussion in this section a number of craze suppression mechanisms... 

Thus the combination of pre-orientation to suppress crazing and to reduce the natural draw ratio and rubber block introduction to bias the deformation response toward yielding has converted a brittle polymer to a moderately ductile one. Although the BPFC domain Tg has been reduced by roughly 30 °C, the improved balance of mechanical properties makes this sacrifice worthwhile. 

It is well known that the mechanical behavior of glassy amorphous polymers is strongly influenced by hydrostatic pressure. A pronounced change is that polymers, which fracture in a brittle manner, can be made to yield by the application of hydrostatic pressure Additional experimental evidence for the role of a dilatational stress component in crazing in semicrystalline thermoplastics is obtainai by the tests in which hydrostatic pressure suppresses craze nucleation as a result, above a certain critical hydrostatic pressure the material can be plastically deformed. 

The promotion of energy dissipative processes that delay or entirely suppress fracture processes originating from imperfections in the internal structure or scratches and notches is enhanced by cavitation. In almost all cases, cavitation either makes possible further toughening by activating other mechanisms or itself contributes to the plastic response of the polymer. The most energy dissipative processes, crazing and shear yielding, occur at a reduced stress level. 

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