Coextrusion of LDPEs in the cast film process (zig-zag interfacial instabilities)

Abstract

This work shows results of experiments on a coextrusion cast film line and is focused mainly on studying conditions for the onset of zig-zag interfacial instabilities. The measurements were performed for a wide range of LDPEs polymerized by different polymerization methods. It is shown that for a group the materials prepared by a similar polymerization method there exists a critical shear stress value at the interface that determines the onset of the instability. The values determined for different material groups are different and it seems that there is a correlation between the molecular weight distribution width and the critical shear stress value. The broader is the MWD the lower is the critical shear stress value.