Scission-dominated crazing

One of the great successes of the craze growth model is that it predicts a transition from scission-dominated crazing to shear deformation as the strand density of the network is increased. While the shear yield stress is essentially unaffected by dian ... 

Similar behavior has been found for dust-free films of poly(methylmethacrylate) (PMMA) and poly(a-methylstyrene) (PaMS) as shown in Figs. 35b and 35c and we expect similar results for any glassy polymer that deforms predominantly by crazing at low temperatures (i.e., one in which scission-dominated crazing occurs in preference to shear deformation). 

In thin film studies, however, Kramer and co-workers have observed the reverse to be true, that crazing is preferred at higher temperatures, while shear deformation zones are observed at lower tefnperatures. This diametrically opposite behavior may have its origins in the different type of craze fibril formation that may occur in the bulk vs in the thin films. Preliminary observations indicate that chain scission may-dominate in bulk craze fibril formation, leading to weaker crazes at lower temperatures, whereas disentanglement processes may dominate in the thin films, leading to stronger crazes at lower temperatures... 

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