Distortion of Interfaces in a Multilayer Polymer Co-extrusion Feedblock

Abstract

Numerical simulations of co-extruded multilayered viscoelastic polymers flowing through a feed block were performed to analyze the effects of polymer rheology and process conditions on the distortion of interfaces between layers. Finite element simulations assuming Phan-Thien Tanner viscoelastic fluids were used to test the effects of increasing the number of layers introduced to the feed block and decreasing wall friction on interface distortion. It was found that increasing the number of layers introduced to the feed block decreased the overall distortion in the layers by reducing the overall magnitude of second normal stress differences and thus decreasing the normal in-plane velocities that cause distortion, which was validated by experiments. Decreasing wall friction was also found to decrease the amount of distortion in layer interfaces by decreasing the strength of these second normal stress differences.