Interfacial flow instability in multilayer coextrusion

Abstract

Abstract In coextrusion of multilayer film and sheet, one type of flow instability which can occur is a wavelike distortion of the interface under certain coextrusion conditions. Severe instability can cause intermixing of the layers, particularly in thin skin coextrusion. Observations have shown that the onset of instability is associated with a “critical interfacial shear stress”. This paper describes a mathematical model of non‐Newtonian multilayer flow which was used to correlate experimental observations.