Effect of Screw Stagger on Mixing in a Tangential Counter-Rotating Twin Screw Extruder

Abstract

Abstract The Counter-Rotating, Tangential Twin Screw Extruder (CR TSE) is a polymer processing device which has been in industrial use for dozens of years. Over this period of time, many of the design parameters have been studied for their effect on processing issues that are related to a particular application. Recent studies have shown that the CR TSE is a greater-than-linear mixer and that is due primarily to the flow in the nip region. This study seeks to determine the relationship between mixing rates and percent of screw stagger. Using a flow visualization technique of an acid-dyeeradication, experiments were conducted varying the stagger setting every 10%. In this experiment the total mixing length was used as the measure of mixing. Data was taken at the time of the experiment and the process was videotaped for later review and data evaluation. The technique provides both qualitative and quantitative information. A discussion of the nature of the extruder performance as a function of screw stagger is reported and important design considerations presented.