Helical flow of polymer melts in extruders, part 1: Model development

Abstract

AbstractOperating and processing conditions as well as the selection of the screw design in injection molding industry are largely based on trial‐and‐error exercise, which is expensive and time consuming. A better approach is to develop mathematical models to help select the conditions and parameters and predict the process performance. However, most of the models developed and used so far contain unrealistic geometrical and mathematical simplifications. The objective of this work is to develop a steady‐state three‐dimensional mathematical model to describe the flow of an incompressible polymer melt inside a helical geometry, which represents the polymer's true motion in extrusion and injection molding processes. The mathematical model is first developed in a natural cylindrical system. Transformers are then derived to obtain the model in helical coordinates. A novel feature of this work is the consideration of tapered screws, i.e., screws tapered either upward or downward along the direction of the flow. © 2010 Wiley Periodicals, Inc. Adv Polym Techn 29:249–260, 2010; View this article online at wileyonlinelibrary.com. DOI 10.1002/adv.20195