Ductile/fragile temperature

All these factors indicate that there is no strict correlation between the fragile-ductile transition temperature and Tg. Beyond Td and Tg, polymers are prone to a pure ductile fracture, which means fiiat they undergo an irreversible plastic deformation before breaking. 

Since a polymer at its gel point is in a critical state (4-9), it commonly is called a critical gel (10) to distinguish it from the various materials that are commonly called gel. It is interesting to explore the properties of the critical gel and use these as reference for describing the properties in the vicinity of the gel point. The critical gel affords imiversal rheological properties that are intermediate between liquid and solid, including the temperature shift factors that are also in between (11). It combines extreme ductility and fragility when subjected to large strain. Its... 

Robertson tests have determined the strength and temperature for the translation of fragile failure to ductile failure [11]. 

Fig. 26.4 Temperature and CN (z) dependence of the Au-Au bond maximum strain show the order of melting at a curved surface of a nanowire and infers the breaking mode of a nanowire at different temperature ranges. At higher T, core bond breaks first because of with ductile manner because of the lower extensibility at lower T, skin bond break first with fragile manner because of the shorter skin bond (reprinted with permission from [103])...

The precise temperature (F ) at which this fragile-ductile transition occurs depends on factors such as... 

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