The main difference between Styrofoam and Polystyrene is that the Styrofoam is a trademark for expanded polystyrene and Polystyrene is a polymer.
Styrofoam is a trademarked brand of closed-cell extruded polystyrene foam (XPS), commonly called “Blue Board” manufactured as foam continuous building insulation board used in walls, roofs, and foundations as thermal insulation and water barrier. This material is light blue in color and is owned and manufactured by The Dow Chemical Company.In the United States and Canada, the colloquial use of the word styrofoam refers to another material that is usually white in color and made of expanded (not extruded) polystyrene foam (EPS). It is often used in disposable coffee cups and coolers, and as cushioning material in packaging. The trademarked term is used generically although it is a different material from the extruded polystyrene used for Styrofoam insulation.
The Styrofoam brand polystyrene foam, which is used for craft applications, can be identified by its roughness and the “crunch” it makes when cut. Additionally, it is moderately soluble in many organic solvents, cyanoacrylate, and the propellants and solvents of spray paint.
Polystyrene (PS) is a synthetic aromatic hydrocarbon 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 vapour and has a relatively low melting point. Polystyrene is one of the most widely used plastics, the scale of its production being several million tonnes per year. Polystyrene can be naturally transparent, but can be coloured with colourants. Uses include protective packaging (such as packing peanuts and CD and DVD cases), containers (such as “clamshells”), lids, bottles, trays, tumblers, disposable cutlery and in the making of models.
As a thermoplastic polymer, polystyrene is in a solid (glassy) state at room temperature but flows if heated above about 100 °C, its glass transition temperature. It becomes rigid again when cooled. This temperature behaviour is exploited for extrusion (as in Styrofoam) and also for molding and vacuum forming, since it can be cast into molds with fine detail.
Polystyrene is slow to biodegrade and is therefore a focus of controversy among environmentalists. It is increasingly abundant as a form of litter in the outdoor environment, particularly along shores and waterways, especially in its foam form, and also in increasing quantities in the Pacific Ocean.
Expanded polystyrene foam, such as is used in cups and packaging.
A vinylic polymer of styrene, CH2CHphenyl.
An alkane chain of benzene molecules, RCH2CHphenylR.