On the Use of a Kolsky Torsion Bar to Study the Transient Large-Strain Response of Polymer Melts at High Shear Rates

Abstract

A Kolsky torsion bar is utilized successfully in a novel rheometric experiment for measuring the transient large-strain response of polymer melts under high shear-rate loading. A molten low-density polyethylene is studied with the new technique. The results show that the high-rate shear response of the material has an instantaneous rate dependence that may not be discernible at low rates and a strain-dependent hardening that saturates at large strains instead of fading. The usefulness of the technique and the significance of the findings are discussed in comparison with a modified rubberlike liquid theory and high-rate capillary measurements for low-density polyethylene melts.