Chain disentanglement craze

Aryl-aliphatic copolyamide Bisphenol A polycarbonate Chain disentanglement craze N-Cyclohexyl maleimide unit... 

Under conditions where chain mobility is high enough, typically at high temperature and low strain rate, the loss of entanglement in the active layer at the craze-bulk interface can occur by chain disentanglement, resulting in chain disentanglement craze (CDC). 

For these reasons, PMMA and its maleimide and glutarimide copolymers represent very suitable materials for investigating the effect of the chemical structure and of the solid state molecular motions on the plastic deformation, the occurrence of the various micro-mechanisms of deformation (chain scission crazes, shear deformation zones, chain disentanglement crazes), as well as the fracture behaviour. 

In order to understand fracture behaviour, it is important to analyse the types of deformation micromechanisms undergone under strain chain scission craze (CSC), shear deformation zone (SDZ), chain disentanglement craze (CDC) and the temperature range over which each one occurs. Furthermore, it is worth wondering whether these micromechanisms are related to /i transition motions. 

Characteristic stress associated with chain disentanglement craze Characteristic stress associated with chain scission craze Limit of purely elastic behaviour Plastic flow stress... 

In the case of BPA-PC, the crazes occurring at high temperatures and showing a MW dependence have led the authors [57] to introduce the mechanism of craze formation by chain disentanglement (CDC). 

An increase of the craze stability of tensile-induced crazes with rising M has been noted in various glassy polymers. In a study made on thin PS films by Berger and Kramer the craze extension ratio was determined at various temperatures for polymers of varying M. For measurements made at room temperature, X varied little with molecular weight but, as the temperature was raised, and chain disentanglement processes became more probable, the situation changed. For example, at 50 °C,... 

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