Natural craze extension ratio

For craze growth at temperatures well below the glass transition temperature it is observed experimentally that the natural craze extension ratio X is nearly a constant value characteristic of the particular polymer under investigation It was ob-... 

In the discussion of the shear yielding and crazing behavior of PC (in Sect. 3.2 and 4.1), the existence of characteristic extension ratios has become apparent (1) The extension ratio, 7. , after shear yielding referred to as natural draw ratio, (2) the extension ratio, V, of craze I fibrils and (3) the extension ratio, at craze II initiation. 

As noted, once the material has been drawn into the craze it appears to stabilize, and little, if any, further extension takes place. As with cold drawing, the fibrillar material is seen to take on a natural draw ratio, Xn, the value of which is characteristic of the individual polymer. Kramer (116,141) found that the natural draw ratio correlated well with the maximum theoretical extension expected for an entangled network, Xmax ... 

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