Transient simulation of coextrusion flows in coat-hanger dies

A 2-D transient finite element model of two-layer coextrusion has been developed with a generalized non-Newtonian constitutive equation to study the problem of interfacial instability. Experiments were done with LDPE 132I^TM (Dow Chemical Co.) in a coat-hanger die using two extruders, under well controlled temperature and flow conditions, where stable and unstable interface profiles were observed. Cross-sections of the frozen heel were taken and compared to transient simulations by quantitatively examining the position of the interface between the two layers.