Suspension Polymerization Processes

Industrial suspension polymerization usually proceeds by a free-radical mechanism to produce polymer beads. The size distribution of the polymer beads is often similar to that of the polymerizing drops in the reactor. That distribution is determined by the operating mechanisms of drop breakage and drop coalescence. Consequently, the value of the Reynolds number is significant and a potential change in flow regime must be considered in reactor scale-up. The choice of suspending agent, which can be a water-miscible polymer or a finely divided particulate solid, can affect both the drop size and the properties of the final product. High monomer conversions are attainable but reaction kinetics can be affected by increases in drop viscosity during the polymerization. Drop mixing, which sometimes takes place, can be slow, so that non-uniformity occurs in the final product. With copolymerization, complications can arise if the initiator, or one of the monomers, is partially soluble in the continuous phase. Adverse environmental impact of suspension polymerization can be avoided by cleaning and/or recycling the continuous phase when it leaves the reactor.