Influence of Molecular Entanglements in Crazing

The effects of molecular entanglements on the rheology of polymers above the glass transition temperature are large and have been recognized for a long One of the most prominent effects is the appearance of a rubbery 

The chain contour length 1 between entanglements is given by le = lo Me/Mo 

A single chain in the entanglement network is shown schematically in Fig. 15. If the chain is extended along its end-to-end vector d, it cannot be extended more than a maximum extension ratio i.e., 

For a network however, the average chain will have equal projections on each of three perpendicular axes. Imagine stretching this network along an arbitrary axis, say X3, by an extension ratio and allowing the network to contract by along 

Much less attention has been given to the effects of entanglements on the mechanical properties of crazes and on the competition between crazing and other. 

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Since then the research activity may even have increased. Central themes were the molecular mechanisms in craze initiation, the influence of molecular weight and presence of entanglements, the nature of plastic instabilities, the role of crazes as precursors to cracks, and last but certainly not least, the formation of crazes in semicrystalline and multiphase polymers. Although considerable progress has been made in the above mentioned fields, some important questions are still open today. 

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