Technological solutions to reduce the geometrical defects during the cast film process

Abstract : The polymer cast film process induces some geometrical defects : the width reduction (neck-in defect) and the inhomogeneous decrease of the thickness distribution (edge bead defect). These defects prevent from predicting the film final dimensions and thus from a high industrial productivity. In this paper, a numerical model developed by the authors is used to test and optimize two technological solutions, aimed at reducing the geometrical defects : a localized air cooling on the edges of the film at the die exit and an "encapsulation die" which enables the extrusion of a high melt strength polymer along the outer edge of a core polymer. Numerical results are confronted with experimental investigations