Kinetics of Styrene and Methylmethacrylate Polymerizations in A Starved Feed Reactor

A starved feed reactor (SFR) is one in which rapidly decomposing initiator and rapidly polymerizing monomer are fed slowly into a large volume of solvent, thus producing polymer whose chain length is largely determined by the stoichiometric ratio of monomer to initiator. Such a reactor is useful for the preparation of low molecular weight polymers. A SFR has been used to polymerize styrene (STY) and methylmethacrylate (MMA) with 2,2' azobisisobutyronitrile (AIBN) as initiator over a temperature range of 100 to 130°C. in 2-heptanone. Polymers were produced at a solids fraction ranging from 20 to 60 % and had chain lengths of 20 to 140. The monomer consumption and polymer molecular weight distributions were measured as a function of time. Both a simple, ideal model and a more detailed model for the polymerizations were developed. It was found that the STY polymerizations could be modeled by only including a chain length dependence for the termination rate constant, but the MMA polymerizations required the consideration of both the gel and depropagation effects.