Residence Time Distribution in Twin-Screw Extruder Measured by Non-destructive Ultrasonic Device

摘要

In this study, we performed RTD measurement at the die exit of co-rotating twin screw extruder using a non-destructive ultrasonic device. The ultrasonic device was composed of a steel buffer rod and 10 MHz longitudinal piezoelectric ultrasonic transducer. Steel buffer rod is a safety implement for the protection transducer against hot operating temperature. This inline method is based on the ultrasonic response of a filled polymer, where the solid particles act as a tracer. To determine RTD, calcium carbonate (CaCO_3) was used as a tracer. The RTD measurements involved the use of ultrasonic tracer and the measurement of the variation of ultrasonic signal strength with time caused by the tracer concentration change. The ultrasonic tracer, pellet types of compounded CaCO_3 in polymer were used in this study. The effects of CaCO_3 concentration on RTD and flow patterns were studied in the extrusion of a thermoplastic resin. Experiments on the residence functions of different screw speed, feeding rate and screw configurations were also carried out.