Suspension polymerization is a heterogeneous radical polymerization process that uses mechanical agitation to mix a monomer or mixture of monomers in a liquid phase, such as water, while the monomers polymerize, forming spheres of the polymer.
This process is used in the production of many commercial resins, including polyvinyl chloride (PVC), a widely used plastic, styrene resins including polystyrene, expanded polystyrene, and high-impact polystyrene, as well as poly(styrene-acrylonitrile) and poly(methyl methacrylate). This method is used for the production of polystyrene, polyvinyl chloride, polyvinyl acetate, etc.
In general, a suspension polymerization system consists of a dispersing medium, monomer(s), stabilizing agents, and a monomer soluble initiator. Water1 is almost in all cases the continuous phase. For the monomer to be dispersed in the water, it has to be fairly insoluble. If the monomer is not sufficient insoluble, prepolymers or partially polymerized monomers (oligomers) can be used that are either insoluble or have a much lower solubility in the water than the monomers. This will also increase the particle size.
Advantages of Suspension Polymerization
Suspension polymerization has several advantages over other polymerization techniques; since water is usually the continuous phase, it acts as a very effective heat-transfer medium which is very economical and more environmentally friendly than the solvents employed in solution polymerization. Furthermore, temperature and viscosity control is fairly easy. Compared to emulsion polymerization, purification and processing of the polymer are much easier since very little catalyst is used and the final product is a 100% solid resin.
- Ready to control of the heat of polymerization.
- Suspension of the polymer may be directly usable.
- It is only applicable for the water-insoluble monomer.
- Continuous agitation required.
- Contamination by the stabilizer.