Influence of postdrawing temperature on mechanical properties of melt-spun isotactic polypropylene

Mech. properties of melt-spun and postdrawn isotactic polypropylene (iPP) are studied to examine the dependence on the temp. in the postdrawing stage. In accordance with the literature, the Young's modulus is uniquely detd. by the applied draw ratio. However, we found that the overall mech. behavior strongly depends on the applied postdrawing temp. For a fixed draw ratio, a significant drop in yield stress can be obsd. with decreasing drawing temp. At a certain drawing temp., this drop leads to a transition from brittle to ductile failure behavior. From this study it can be concluded that a proper choice of drawing conditions offers control on several mech. properties (e.g., stiffness, strength) at the same tim