MECHANICAL MIXING IN PIN SCREW EXTRUDERS: EXPERIMENTAL AND NUMERICAL ANALYSIS

摘要

Pin extruders are frequently used in rubber processing. They are designed to exhibit good mixing capabilities and deliver an important mechanical work to facilitate the processing and mixing of elastomers. The design of such single screw extruders (SSE) is based on empirical know-how and trial-and-error. In this study, we compare three extruder configurations: a simple, continuously flighted single screw, a single screw with interrupted flight and finally a pin barrel screw. The calculation of the flow rate vs. pressure drop confirms that the interrupted flight reduces the pumping efficiency and the addition of the pins does not increase this effect any further. Statistical analysis of the trajectories obtained from the transient velocity field allows us to evaluate directly indices linked to the mixing quality. We obtain a good qualitative agreement between the calculated and measured RTD and confirm that there is an increasing mixing capability in the grooved screw and even more so in the pin barrel extruder.