Manufacturing expandable polystyrene beads
Expanded polystyrene or EPS

The water-suspension polymerization process is employed for the polymerization of EPS. Monomeric styrene (C ₈ H ₈ ) (figure 1 ) is dispersed in fine droplets in water.

Radical polymerization initiators are essentially organic peroxides (benzoyl peroxide) which must be soluble in styrene monomer and insoluble in water. Droplet size can be adjusted by a number of parameters, such as the addition of a protective agent to stabilize the suspension, mixing conditions, reactor shape, and so on. A flame-retardant system may also be incorporated.

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