Acrylic Acid/Vinyl Acetate Suspension Copolymerizations. 2. Modeling and Experimental Results

Abstract

The present work presents experimental and modeling results for both vinyl acetate (VAc) homopolymerizations and VAc/acrylic acid (AA) copolymerizations performed in suspension. It is shown that the VAc homopolymerization presents a maximum conversion limit that cannot be surpassed with additional feed of an initiator. This maximum conversion limit is believed to be due to viscosity effects that characterize the well-known gel effect. A correlation based on the free-volume theory is then proposed for the gel effect. Because the molecular weight averages obtained for samples of the produced poly(vinyl acetate) are very high, the existence of strong diffusion limitations in the reaction medium is very likely. A mathematical model is developed and shown to describe very well the dynamic conversion and molecular weight profiles obtained experimentally. The model is then extended to describe VAc/AA copolymerizations, considering the AA partition between the organic and aqueous phases, which is a fundamental po...