Evaluation of Temperature-strain rate Dependent Uniaxial and Planar Elongational Viscosities for Branched LDPE Polymer Melt

In this work, novel rectangle and circular orifice dies have been utilized for temperature-strain rate dependent planar and uniaxial elongational viscosity measurements for the LDPE polymer melt by using standard twin bore capillary rheometer and Cogswell model and the capability of three different constitutive equations (novel generalized Newtonian model, modified White-Metzner model, modified Leonov model) to describe the measured experimental data has been tested. It has been shown that chain branching causes the strain hardening occurrence in both, unixial and planar elongational viscosities and its maximum is shifted to the higher strain rates if the temperature is increased. The level of uniaxial elongational strain hardening for the branched LDPE sample has been found to be higher in comparison with the planar elongational viscosity within wide range of temperatures.