Stress and strain oscillations in syndiotactic polypropylene and in poly(ethyleneterephthalate)

Stress oscillations were produced and analyzed in partly-crystalline syndio tactic polypropylene (sPP) and in poly(ethyleneterephthalate) (PET) in cold drawing experiments. Strain oscillations, which always occur in connection with stress oscillations, were also investigated. The experiments were per formed varying the parameters temperature, sample geometry and drawing velo city. This article gives first results of our investigations, which show di screpancies to the existing theories. (C) 1999 John Wiley & Sons, Inc.