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Suspension polymerization is a free-radical polymerization technique where the reaction takes place in droplets of a monomer dispersed in a continuous phase, typically water. The monomer, which is insoluble in the continuous phase, is stabilized by suspending agents such as polyvinyl alcohol or cellulose derivatives. These agents prevent the monomer droplets from coalescing during the polymerization process. The polymerization is initiated by a soluble initiator, which is either dissolved in the monomer or in the continuous phase, depending on its solubility.

The process involves vigorously stirring the monomer and initiator in the continuous phase. This creates small, uniformly sized monomer droplets, which act as individual reaction vessels. Heat generated by the exothermic polymerization reaction is efficiently dissipated by the continuous phase, allowing for good temperature control and preventing runaway reactions. The resulting polymer is obtained as discrete beads or pearls, which can be easily separated from the continuous phase by filtration or centrifugation.

Suspension polymerization is widely used for the production of various polymers, including polyvinyl chloride (PVC), polystyrene (PS), and polymethyl methacrylate (PMMA). The polymer beads produced by this method often have good flowability and are suitable for applications such as extrusion, injection molding, and the production of ion-exchange resins. The particle size and distribution of the polymer beads can be controlled by factors such as the stirring speed, the type and concentration of suspending agents, and the viscosity of the monomer.