A study of the time dependence of the post yield behavior of a syndiotactic polypropilene

Cyclic tensile tests at constant displacement rate have been performed on a syndiotactic polypropylene to study the effect of the loading history on its mechanical behavior. A test procedure was, at first, properly set up to take into account the inhomogeneous deformation occurring in the adopted dumb-bell specimen. A dependence of the material behavior on the loading history was observed up to yielding, as expected. No effect of the loading history was, instead, observed, neither in the post-yield behavior nor in the strain recovery during and after unloading.