Polymer Flow Instability: A Review and Analysis

Abstract

In the flow of polymeric materials through small orifices, it was recognized early that if flow parameters such as shear stress or shear rate exceeded certain critical values, the extrudate emerging from the die would exhibit surface defects or irregularities in cross-section. Since the extrusion of molten plastics, elastomers, and fibers is such an important industrial operation and the production of extruded products is limited to rates below those which produce extrudate distortion, the study of this phenomenon became important. In the last 30 years many descriptions and experiments of the onset of extrudate distortion and its accompanying flow behavior have appeared in the literature. This literature has attained such proportion that it has been subject to several reviews in recent years [1-6].