Abstract: In the feeding sleeve several helical grooves were opened up. Regarding the materials between groove and channel as a solid-plug, the barrel and screw could be considered as an indivisible system to cooperatively push forward the materials in solid conveying zone. A mathematical model was formulated to consider the influences of the compressibility and the acceleration of the materials, the pressure and the velocity of the solid-plug in the down-channel were calculated. Finally, it is found that when the solid-plug was being carried by way of positive conveying, the peak pressure at the end of solid conveying zone was strikingly promoted and the materials could be stably extruded.

Key words: single-screw extruder, helical groove, double flight driving, solid conveying, pressure distribution