IUPAC name
Other names
  • 9003-53-6
Abbreviations PS
  • none
ECHA InfoCard 100.105.519
Density 0.96–1.05 g/cm3
Melting point ~ 240 °C (464 °F; 513 K)[1] For Isotactic Polystyrene
Boiling point 430 °C (806 °F; 703 K) and depolymerizes
Solubility Soluble in benzene, carbon disulfide, chlorinated aliphatic hydrocarbons, chloroform, cyclohexanone, dioxane, ethyl acetate, ethylbenzene, MEK, NMP, THF [2]
Thermal conductivity 0.033 W/(m·K) (foam, ρ 0.05 g/cm3)[3]
1.6; dielectric constant 2.6 (1 kHz – 1 GHz)[4]
Related compounds
Related compounds
Styrene (monomer)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references
Expanded polystyrene packaging
A polystyrene yogurt container
Bottom of a vacuum-formed cup; fine details such as the glass and fork food contact materials symbol and the resin identification code symbol are easily molded

Polystyrene (PS) /ˌpɒliˈstrn/ is a synthetic aromatic hydrocarbon polymer made from the monomer known as styrene.[5] Polystyrene can be solid or foamed. General-purpose polystyrene is clear, hard, and brittle. It is an inexpensive resin per unit weight. It is a poor barrier to oxygen and water vapour and has a relatively low melting point.[6] Polystyrene is one of the most widely used plastics, the scale of its production being several million tonnes per year.[7] Polystyrene can be naturally transparent, but can be coloured with colourants. Uses include protective packaging (such as packing peanuts and in the jewel cases used for storage of optical discs such as CDs and occasionally DVDs), containers, lids, bottles, trays, tumblers, disposable cutlery[6], in the making of models, and as an alternative material for phonograph records.[8]

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.

Under ASTM standards, polystyrene is regarded as not biodegradable. It is accumulating as a form of litter in the outside environment, particularly along shores and waterways, especially in its foam form, and in the Pacific Ocean.[9]