Polystyrene (
PS) is a synthetic
aromatic polymer made from the
monomer styrene. Polystyrene can be solid or foamed. General-purpose polystyrene is clear, hard, and rather brittle. It is an inexpensive resin per unit weight. It is a rather poor barrier to oxygen and water vapor and has a relatively low melting point. Polystyrene is one of the most widely used
plastics, the scale of its production being several billion kilograms per year. Polystyrene can be naturally
transparent, but can be colored with colorants. Uses include protective packaging (such as packing peanuts and CD and
DVD cases), containers (such as "clamshells"), lids, bottles, trays, tumblers, and disposable
cutlery.
