Chapter 12 - Polymer Reaction Engineering

Abstract

This chapter focuses on suspension polymerizations in the light of polymer reaction engineering. Engineering of polymerization reactions requires a detailed knowledge of the phenomena that take place in the polymer reactor. This entails a model of the polymerization kinetics and the heat and mass transfer features of the particular polymerization and process. Polymerization reactions are usually complex and a certain degree of mathematical sophistication is required for effective modeling. There are some fundamental differences in the engineering of step-growth and chain-growth polymerizations because of basic distinctions in the mechanisms of these reactions. A propagation reaction in a kinetic chain sequence must be fast or the series of monomer additions will not be long enough to produce high-molecular-weight polymers before the intervention of termination or transfer reactions. This is not generally true for step-growth polymerizations where only an addition reaction is involved and the growth of macromolecules can occur in a series of starts and stops. The major commercial examples of chain-growth polymerizations involve reactions across C=C double bonds to produce polymers with all-carbon backbones. Chain-growth polymerizations that are carried out in the absence of diluents are characterized by high viscosity and poor heat transfer. High-molecular-weight polymer coexists with low-molecular-weight species and monomer, and molecular weight does not increase with conversion. Polymerization reactions can be further classified into batch and continuous processes.