ABSTRACT
A single-screw extruder consists of one screw rotatingin a closely fitting barrel; the transport mechanism is based on frictionbetween the polymer and the walls of the channel. In case of intermeshing extruders the flights of one screw stickin the channel of the other screw. The closely intermeshing twin-screw extruders, both counterrotating and corotating, can best be modeled as series of C-shaped chambers. In general, it can be concluded that because of the large shear forces in the channel and the simple application of mixing elements, self-wiping extruders are often used in compounding processes. Single-screw extruders can be used in reactive processes where the viscosity changes remain within acceptable limits, like in some grafting reactions. In counterrotating extruders both drag flow and internal pressure generation favor the calender leak. Since in the calender gap the material is elongated and kneaded, it can be concluded that counterrotating extruders favor a good kneading action.
