Die design optimization for extrusion and multilayer co-extrusion processes to attain layer stability and uniformity

Multilayer materials offer benefits in terms of new materials for packaging, barrier and other applications. The ability to maintain layer stability and uniformity as the polymers flow into different die designs is important in co-extrusion. This work investigates the effect of die design---including manifold design and use of a secondary manifold region---in fabricating multilayer films.;Three dimensional mono layer simulations were carried out for polypropylene material to evaluate different die designs. Multilayer simulations were carried out for horizontal and vertical layering systems using polypropylene and PMMA as flow materials to test the die designs for layer stability and uniformity using Polyflow Software.;Mono-layer and multilayer simulations showed better results for elongated tear drop shaped manifold as compared to a tear drop shaped manifold with respect to shear stresses. Results for horizontal layering showed that a secondary manifold region could prove beneficial for horizontal layering as it reduced the overall stresses in the die. For vertical layering, a larger manifold backwall angle gave rise to a much gradual flow making the flow pattern more streamlined. Results for vertical layering showed that a secondary manifold led to sideway movement of layers making the layer flow unstable.