Measurement of interfacial instabilities during coextrusion of LDPE's in flat dies

Abstract

Coextrusion of low density polyethylenes (LDPE) in flat dies was analyzed. The zig-zag instabilities that are related to the shear stress at the interface and the wave instabilities related to the merge point of coextruded material was distinguished. It was shown that the wave instabilities were brighter in the material samples than the zig-zag instabilities. It was stated that the wave instabilities may also depend on the overall stresses generated in the system and not only on the amount of the stretching.