Mechanistic Complexities of High Temperature Free-Radical Acrylic Solution Terpolymerization

The generalized treatment of addition copolymerization kinetics developed by Arriola and Ray in the 1980s included every complexity imaginable, including depropagation, penultimate effects in copolymerization, chain scission after intra or intermolecular chain transfer to polymer, and branching introduced by chain transfer to polymer, terminal double bond polymerization and/or chain-attack by initiator-derived radicals. One system for which all of these mechanisms are important is the production of acrylic resins used for automotive coatings, synthesized from a mixture of monomers selected from the methacrylate, acrylate and styrene families. The low molecular weight polymers with reactive functionalities are made via high-temperature starved-feed free-radical solution semibatch terpolymerization. In this presentation I review recent advances made in the study of these complex mechanisms and the measurement of the associated rate coefficients. In addition, a full mechanistic terpolymerization model is shown to provide good predictions of monomer conversion and polymer molecular weights of high temperature semibatch free radical terpolymerization over an extended range of operating conditions.