Shear induced crystallization of high-density polyethylene

Abstract

Relaxation behavior and shear-induced isothermal crystallization of two commercial high-density polyethylenes (HDPE) were investigated by using a rotational rheometer with cone-plate configuration. The excessive free energy was estimated by the measured shear stress and the first normal stress difference, based on a model proposed by Marrucci, in which the molecular orientation brought about by shearing was responsible for the increase of free energy. The results show that a small change of free energy can significantly increase the crystallization rate, thus the induction time of crystallization decreases rapidly as the shear rate increases. The excessive free energy and the induction time of isothermal crystallization can be correlated by an exponential function.

Keywords

high-density polyethylene / isothermal crystallization / shearing / relaxation behavior