ABSTRACT
W. A. Mack and R. Herter proposed twin-screw technology for reactive extrusion because of difficulties in scaling up single screw extruders that could be avoided in twinscrew extruders. Residence times of half an hour were possible in self-wiping twin-screw extruders. Mack and Herter also concluded that a combination of a stirred-tank reactor, a single-screw extruder, and a twin-screw extruder was most suitable for the production of polyesters. Reactive extrusion gives the opportunity to polymerize under constant high shear. This opens possibilities for new processes in the field of reactive mixing and blending. The mixing can be adjusted to the requirements for optimal reaction conditions by a judicious screw design. Bulk polymerizations are traditionally subdivided into addition reactions and condensation reactions. During addition reactions a polymer chain is formed in a very short time, until it terminates and stops growing. Polymerization reactions exist of which the reaction kinetics shows aspects of both addition and condensation reactions.
