ABSTRACT
Screw-type mixers, or extruders, of which there are numerous design configurations, are widely employed for the extrusion of molten or plasticized polymers to semi-final- and final-product forms. In single-screw machines, mixing quality is established by the total shear of deformation for a given material volume. Twin-screw mixers are more effective because they process material by the action of intermeshing screws. The efficiency of a screw mixer varies with the volume of the pitch in the helical channel of the screw. The energy transmitted to the screw is spent for overcoming the following resistances: extrusion forces; friction forces of material against the screw; friction forces of material against the machine case, and friction forces in the bearings of the drive. Universal screw mixers are used for processing a variety of polymer materials. These machines are characterized by a reciprocal motion of screws in the axial direction with simultaneous rotation.
