Distributive mixing in a single-screw extruder - Evaluation in the flow direction

This study investigates distributive mixing in the flow direction for a sin gle-screw extruder. With a custom-designed transparent extruder, an Image A nalysis System, and a newly defined parameter, i.e., distribution index, th e distribution mechanism is thoroughly examined with respect to various pro cessing conditions or screw designs. Experimental results indicate that the longitudinal distribution can be enhanced with an increasing RPM, a longer metering section, or a decreasing diameter of the die. However, a plateau region occurs when an optimum condition exists for the RPM and the length o f the metering section. In addition, an extruder modified with a barrier, p in-elements, or high helix angle performs better in the longitudinal mixing than the conventional one. Our results further demonstrate that leakage fl ow significantly enhances mixing in the flow direction.