PRESSURE GENERATION AND SCREW DESIGN IN COROTATING TWIN-SCREW EXTRUDERS

In order to properly design the screws and to locate feed and devolati lization ports, it is necessary to determine the extent of filled zone s and to evaluate the pumping and mixing efficiency of different knead ing sections. This paper presents an experimental study of the pumping efficiency of forward and backward pumping screws and kneading sectio ns. Results indicate that the pumping efficiency is generally greater than that predicted by 2D inelastic models and that left-handed elemen ts do not necessarily fill entirely, especially at their downstream en d where backward pumping and forward pumping flights meet.