SHEET COEXTRUSION OF POLYMER-SOLUTIONS AND MELTS - COMPARISON BETWEENSIMULATION AND EXPERIMENTS

Coextrusion flows of polymer solutions and melts to produce polymeric sheets are studied employing (a) the Lubrication Approximation Theory for a quick determination of interface development and pressure drops for each material; and (b) the Finite Element Method, which uses a u-v -p-T-h formulation for the velocities, pressures, temperatures, and in terface location and solves in the flow domain the full conservation a nd constitutive equations. The determination of the interface is part of the solution process. Simulations have been carried out for several cases of two-layer coextrusion of polymer solutions (Oppanols, i.e., polyisobutylenes) and compared with experimental data available in the literature. A three-layer coextrusion case is also studied with a bar rier ethylene vinyl alcohol and an adhesive layer tying a polystyrene layer, and the results are compared with experimental data. For low fl ow rates, the interface location agrees closely with experiments. For high flow rates, a tendency for encapsulation occurs, which cannot be captured by the present purely viscous two-dimensional simulations. (C ) 1993 John Wiley & Sons, Inc.