ABSTRACT
CO-RUTATING, intermeshing twin-screw extruders have long proved their worth in a wide variety of compounding tasks. Since the mid-1980s, however, a new approach to twin-screw extrusion has emerged in which the main processing occurs while the thermoplastic material stays below its melting point. The term "extrusion" no longer applies because the product at discharge is in a solid powder form and is no longer "extrudable" into a defined shape. This new process takes place under high-shear stress and leads to solid-particle breakup in a continuous operation. Known as S3P, this process can be applied to numerous polymers as well as to rubber, including vulcanized rubber. This chapter discusses the machine functions of the twin-screw extruder, looking first at its traditional use as a versatile compounding extruder and then at the ways in which these functions can be applied or extended to increase the efficiency of the pulverizer.
