Effect of Draw Rate

An increase in the rate of drawing affects stress-strain curves in a manner similar to that of a decrease in temperature. Lazurkin [205] obtained an empirical relationship between yield 

This equation is valid for many polymers. A fit has been determined for polyethylene but not for polypropylene. 

FIGURE 3.32 Tensile strength versus spin-line stress for spun polypropylene fibers. (From Nadella, H.P., Henson, H.M., Spruiell, J.E. White, J.L. J. Appl. Polym. Sci., 1977, 21, 3003. With permission.) 

Nadella et al. [204] studied the drawing of samples H-0042 and 11-1200, which were produced earlier in their spinning studies [79]. The drawing was carried out on an Instron tensile testing machine. One-inch samples were stretched to three different lengths 1 in. beyond the natural draw ratio (disappearance of neck), approximately 1 in. prior to fracture, and between the above two. If necking was not observed, the first stage corresponded to a 

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FIG. 57 Effect of draw rate on the yield stress of polypropylene drawn in air (A) and under water ( ). (From Ref. 32.)... 

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