Continuous Processing of Polymerizing Fluids IV: Continuous Mechanism in a Channel of a Screw-Extruder

Abstract

Reactive extrusion of polymers (REX) is an integrated engineering operation that may combine, completely or partially, the traditionally separated steps of the polymer macromolecule formation, compounding, mixing, devolatilization, shaping and the product structuring into a single engineering operation carried out in a screw extruder as developed over the years for conventional polymer processing. The advantages associated with REX are in substantial reduction of the manufacturing time, energy savings as typically the remelting and often the solvent recovery steps are eliminated, in lower capital investment and in the potential direct feed-back between the polymer mechanical properties and the process conditions.

The present theoretical simulations have suggested that significant interactions exist between the extruder conveying mechanism and polymerization reaction in REX. Our results further suggest that careful temperature control may be required for a successful REX operation involving possibly screw cooling. An analysis of the present type is capable of determining an optimum strategy to maintain a reasonably uniform distribution of the average molecular weight across the channel to ensure both efficient transport and a uniform product. From the extrusion technology standpoint, there is an additional, very important benefit: if the proper temperature control is maintained, the uniformity in radial distribution of molecular weights causes REX to become similiar to conventional melt extrusion in terms of its conveying mechanism.