Cold-drawing network draw ratio

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 ... 

It is, of course, possible that the natural draw ratio is determined directly by the strainhardening requirements. This does not invalidate the hypothesis that cold-drawing involves the extension of a molecular network, but suggests that strain hardening increases very rapidly as the network reaches its limiting extensibility. 

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