A Detailed Lumped Model for Vinyl Acetate Emulsion Polymerization

Abstract

Abstract A mathematical model was developed to simulate emulsion polymerization of vinyl acetate monomer in isothermal, batch and semi-batch reactors. The recipe components included monomer (vinyl acetate), initiator (potassium persulfate), surfactant (sodium dodecyl sulfate) and water as the dispersion medium. The two important phenomena, particle nucleation and particle growth, were modeled in adequate detail. The mechanistic details included: particle formation via micellar nucleation; coupling of the radical concentration in the aqueous phase and the particle phase; determination of the average number of radicals inside the particles by radical entry into, exit from, and termination, inside the particle, assuming pseudo bulk kinetics and partitioning of the monomer among droplets, aqueous phase and particles governed by thermodynamic considerations. The model for the batch reactor was validated against the data taken from literature. This model for the batch reactor was extended to simulate a semi-batch reactor. The semi-batch reactor was considered to operate in two modes: unseeded and seeded. In the unseeded mode, the monomer was fed to the reactor which contained initiator, surfactant and water initially. In the seeded mode, the monomer was fed to the reactor which along with initiator, surfactant and water also contained pre-formed polymer particles (seed particles). Keywords: computer simulation; emulsion polymerization; particle nucleation; polymerization kinetics; vinyl acetate