Numerical simulation of multi-layer flow for polymer melts - A study of the effect of viscoelasticity on interface shape of polymers within dies

A two-dimensional simulation was developed for multi-layer confluent viscoelastic flow in dies, using a finite element method. The simulated interface shape was compared with the experimental results of previous researchers, and the simulated results were confirmed. Two-layer and three-layer flows of two or three kinds of viscoelastic fluids were simulated. Fluids with different non-Newtonian viscosities and the first normal stress differences were used. The layer thicknesses in dies are mainly determined by the shear viscosity and less by the elasticity of the fluid. The normal stress difference between the fluids forming an interface may be related to interfacial instability, and normal stresses near the interface were examined. The normal stress difference between both fluids was affected by the first normal stress difference and elongational viscosity.