Suspension polymerization expandable polystyrene

The reaction engineering aspects of these polymerizations are similar. Good heat transfer to a comparatively inviscid phase makes them suitable for vinyl addition polymerizations. Free-radical catalysis is mostly used, but cationic catalysis is used for nonaqueous dispersion polymerization (e.g., of isobutene). High conversions are generally possible, and the resulting polymer, either as a latex or as beads is directly suitable for some applications (e.g., paints, gel permeation chromatography beads, expanded polystyrene). Suspension polymerizations are run in the batch model. Continuous emulsion polymerization is common. 

Suspension Polymerization. Water is the suspending phase. Inorganic salts and vigorous agitation prevent coalescence and agglomeration. The reaction mode is batch. The largest use of suspension polymerization is for the manufacture of expandable polystyrene beads. 

Water or other nonsolvent Polymer or polymer in solution Suspension, dispersion, or emulsion polymerization Emulsion polymerization of a rubber latex. Suspension polymerization of expandable polystyrene... 

Most expandable polystyrene processes involve aqueous suspension systems in which pentane fractions of petroleum are introduced before, during, or after polymerization of styrene. Water-free systems may also be used. Particle size is controlled by suspension polymerization or by chopping fine filaments. The quenched pellet process for expandable polystyrene can consume off-size particles and is a convenient way to add colorants and cell-nucleating additives. 

The expandable polystyrene particles, based on suspension polymerization, are converted into foam in three steps pre-foaming, temporary storage and final... 

Other major products of suspension processes include expandable polystyrene, where a volatile hydrocarbon is diffused into the polymer beads, and spherical divinylbenzene-based beads for chromatographie and ion-exchange applications. PVC is different from most other suspension proeess polymers in that it is produced by precipitation polymerization, as described earlier. 

Suspension polymerization (60-63) is of special meaning for the production of technically important polymers, as for instance, expanded polystyrene and poly(vinyl chloride). Suspension polymerization refers to the carrying out of a polymerization in micron-sized droplets with oil-soluble initiators. Emulsification and polymerization take place in the same vessel and at the same time. A polymeric stabilizer or protective colloid is... 

Polystyrene is made by bulk or suspension polymerization of styrene. It is commonly available in crystal, high impact, and expandable grades. Its major characteristics include transparency, ease of coloring and processing, and low cost. Styrene monomer is produced from benzene and ethylene. 

Free-radical suspension polymerization, originally developed by Hoffman and Delbruch in 1909 [1] is commonly employed for producing a wide variety of commercially important polymers such as poly(vinyl chloride) (PVC), polystyrene (PS), expandable polystyrene (EPS), high-impact polystyrene (HIPS) and various styrene copolymers with acrylonitrile (SAN) and acrylonitrile-polybutadiene (ABS), poly(methyl methacrylate) (PMMA), poly(vinyl acetate) (PVAc), etc. [2],... 

Many important polymers are made commerdally via suspension polymerization of vinyl monomers. These include poly(vinyl chloride), poly(methyl methacrylate), expandable polystyrene, styrene-acrylonitrile copolymers and a variety of ion-exchange resins and specialist materials. The annual polymer production from suspension processes is very high. 

If a polymer product is required in particulate form, then suspension polymerization is especially suitable. The energy required to disperse monomer drops is lower than that required to break up the finished polymer. Also, drop size control before polymerization is easier to achieve than particle size manipulation of granulated polymer. Suspension polymerization provides a good route to functionalized particles such as those used in ion-exchange resins. Expandable polystyrene beads are also made by suspension polymerization. When a product is to be used in bead form , initial drop diameters can be as large as 1-2 mm [1]. 

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