BASIC ASPECTS AND RECENT DEVELOPMENTS IN SUSPENSION POLYMERIZATION

In suspension processes, polymerisation occurs in a monomer‐containing phase which is dispersed in a continuous liquid phase. Controlled agitation and the presence of drop stabilisers are necessary to maintain the suspension. Temperature control is usually better than that observed in corresponding bulk processes. Polymerisation kinetics are often similar to those which apply to bulk systems but high conversions increase the probability of gel effects. Drop sizes can depend on conditions of turbulence, viscosity and interfacial tension. Correlations for maximum drop sizes are discussed. Drop segregation can affect product quality and reactor design is important. Drop sizes can change with time and particle size distributions may become bimodal. Polymeric stabilisers may be present in both the continuous and dispersed phases. If polymer precipitates inside the drops, the stabiliser can influence the particle morphology. The stabilising action of particulate inorganic solids is not well‐understood. In copolymerisation, cross‐linking may occur. Precipitation of copolymer can be promoted by the use of diluents. Stabilisers can have a role in determining porosity of the final particles. Reactivity ratios may appear to differ from those expected in bulk processes when one or more of the comonomers is appreciably soluble in the continuous phase. Relevant literature is reviewed and topics requiring further work are identified. Copyright © 1990 Hüthig & Wepf Verlag