ABSTRACT
Free-radical polymerization is a widely utilized technology to prepare synthetic polymers in aqueous colloidal dispersion form. It is by far the most commonly used process in industry; manufacturers find that it has a large number of technical advantages (conventional reaction vessels, easy-to-run operations, high molar mass polymers, and wide variety of potential products) and economic advantages (good productivity, inexpensive reagents, relatively low investments). The “synthetic latexes,” which are obtained from polymerization reaction vessels (Fig. 1), can be processed on the production site to separate the polymer, dry it, and then market it in various dry forms (powders, granules, chips, etc.). Large quantities of inexpensive commodity polymers are manufactured in this way: they may be thermoplastics, such as certain polyvinyl chloride (PVC) grades, or elastomers, such as styrene-butadiene rubbers (SBRs) or polychloroprene rubbers. Other products, more complex in terms of molecular structure, are also produced via free-radical emulsion polymerization and offered on specialty markets in dry powder or granule form. Graft copolymers, such as Acrylo-nitrile Butadiene Styrene (ABS) or Methyl Methacrylate Butadiene Styrene resins (MBS), used in the composition of high mechanical performance polymeric materials, intended for the automobile or packaging industries, are illustrative examples of this product class.
