Designing Extrusion Dies for Thermoplastics

Abstract

An extrusion die must be able to produce, at the highest possible flow rate, a specific cross-section of an homogeneous melt that, after cooling, is well within the dimensional tolerances defined. The correct design of such a tool will have to consider the relevant physical and rheological phenomena that take place during the flow of the polymer melt through the die and upon stretching and cooling. This paper presents a possible strategy for die design that considers the most important physical and rheological phenomena in volved in the process without too complex or time consuming computation tech niques. Since an appropriate die design requires extensive data on the polymer properties, useful procedures for characterizing the rheological behaviour of polymer melts are also discussed.