Colloidal stability of high-solids polystyrene and polyvinyl acetate latices

Commercial emulsion polymerization processes are often done with high-solid s recipes (e.g., about 50 wt % monomer), resulting in relatively viscous, p seudoplastic reaction mixtures. The change in rheological behavior during h igh-solids emulsion polymerization complicates the operation in terms of im perfect mixing, increasing heat transfer resistance and reactor fouling. In this article, we report the influence of solids content on the colloidal s tability of polystyrene (PS) and polyvinyl acetate (PVAc) latex systems. Fo r the systems investigated, solids content up to 50 wt % had no influence o n the colloidal stability of the latex. The influence of recipe on colloida l stability is more pronounced than the influence of operating conditions. Brownian coagulation dominates over shear coagulation for both low- and hig h-solids systems, although in some cases the operating conditions appear to have some effect on the course and outcome of high-solids emulsion polymer ization. (C) 1999 John Wiley & Sons, Inc.