Non-isothermal Simulation of an Annular Extrudate Swell

Abstract

The flow phenomena of polymer melts that are important in polymer processing depend on properties such as viscosity, relaxation time and temperature distribution. In this study, we focused on the annular extrudate swell problem that can be seen in pipe molding and hollow fiber spinning. The effects of gap width and wall temperature of an annular die on the swelling ratios of annular extrudates have been investigated by a non-isothermal viscoelastic flow simulation using a streamline-upwinding finite element method. The non-isothermal Phan-Thien Tanner model proposed by Sugeng and Phan-Thien (J. Rheol., 31, 37 (1987)) was employed as a constitutive equation.The calculated results for the outer free surface are in agreement with experimental data near the die outlet in the low shear rate region. As the mean velocity in the die increases, both the outer diameter swelling ratio χfo and the thickness swelling ratio χT increase. In the case of a constant outer diameter, χfo and χT increase with an increase of the diameter ratio κ, which is the inner die diameter divided by the outer die diameter. As the inner die wall temperature rises, higher χfo and lower χT are observed.