What is Polystyrene?

Polystyrene is a type of polymer with thermoplastic properties produced from the petroleum-derived monomer, styrene. In solid form, it is a colorless and rigid plastic, but it may also be returned to a liquid state by heating, and used again for molding or extrusion. It is used to produce many products for industrial and consumer use. In fact, its presence as a plastic in everyday life is second only to polyethylene.

The chemical structure of this material allows it to be classified as a liquid hydrocarbon, meaning that it is composed exclusively of hydrogen and carbon. Like its precursor, it's an aromatic hydrocarbon that participates in covalent bonding with every other carbon atom being attached to a phenol group. It is produced via free radical polymerization, which means that the reaction involves breaking the bonds between electrons and leaving them “free” to form new bonds. When burned, this material yields black carbon particles, or soot. When completely oxidized, only carbon dioxide and water vapor remain.

There are several different types that are produced. Extruded polystyrene is considered to have as much tensile strength as unalloyed aluminum, but it is lighter and more elastic. This is the material used to make a variety of molded products, ranging from plastic tableware to CD cases and model cars. It is also used to produce medical and pharmaceutical supplies.

Extruded polystyrene foam, commonly known as Styrofoam™, is a type of insulation with versatile applications, such as the manufacture of surfboards. In fact, its buoyancy prompted the U.S. Coast Guard to adopt its use in life rafts. This type may also be used in building materials or in roadway construction. For example, it may serve as a layer of insulation under pavement to prevent freezing and thawing of the soil below from cracking the surface.

This strong but lightweight material is also used for crafts, and it is usually sold in sheets. It is typically made up of three layers, with polystyrene at the core sandwiched by paper on either side. The sheets are frequently used as backing to mount artwork or photography, or to construct architectural models. This foam is also familiar to those who work with floral crafts. In fact, the characteristic “crunch” sound made when it's cut is well-known to florists.

Expanded polystyrene foam is actually made of beads of the material. It is used to make “peanuts” for packaging, disposable coffee cups, and foam picnic coolers. Unlike extruded foam, which is blue in color, expanded foam is typically white.