Viscoelastic coextrusion flow modeling by advanced constitutive equations: The influence of the die design on interfacial instabilities

Abstract

Fully viscoelastic FEM together with flow visualization technique are employed to quantify the effect of the die design on the wave type of interfacial instabilities in coextrasion. It has been shown experimentally that the minor channel geometry has a strong impact on the wave type of interfacial instabilities and the results can be correlated through novel criteria called as Total Stress Difference (TSN), which takes in to account the bulk change of the total stress in normal as well as tangential direction with respect to the interface. It has also been shown that specific type of high stress area occurs around the interface at the end of the converging section. This total stress has been found to be non-monotonic and discontinues along the interface and related for the onset of zig-zag type of interfacial instabilities.