Polystyrene

For other uses, see Polystyrene (disambiguation).

"♸" redirects here; not to be confused with Recycling symbol. For the symbol to identify the type of plastic, see Resin identification code.

Polystyrene

Repeating unit of PS polymer chain
Names
IUPAC name Poly(1-phenylethylene)
Other names Thermocol
Identifiers
CAS Number	9003-53-6
Abbreviations	PS
ChemSpider	none
ECHA InfoCard	100.105.519
CompTox Dashboard (EPA)	DTXSID5031925
Properties
Chemical formula	(C8H8)n
Density	0.96–1.05 g/cm3
Melting point	~ 240 °C (464 °F; 513 K) for isotactic polystyrene
Solubility in water	Insoluble
Solubility	Soluble in benzene, carbon disulfide, chlorinated aliphatic hydrocarbons, chloroform, cyclohexanone, dioxane, ethyl acetate, ethylbenzene, MEK, NMP, THF
Thermal conductivity	0.033 W/(m·K) (foam, ρ 0.05 g/cm3)
Refractive index (nD)	1.6; dielectric constant 2.6 (1 kHz – 1 GHz)
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) /ˌpɒliˈstaɪriːn/ is a synthetic polymer made from monomers of the aromatic hydrocarbon styrene. Polystyrene can be solid or foamed. General-purpose polystyrene is clear, hard, and brittle. By weight, it is considered a relatively cheap resin and a fairly poor barrier to oxygen and water vapor, with a relatively low melting point. Polystyrene is one of the most widely used plastics, with the scale of its production being several million tonnes per year. Polystyrene is naturally transparent to visible light, but can be colored with colorants. Uses include protective packaging (such as packing peanuts and optical disc jewel cases), containers, lids, bottles, trays, tumblers, disposable cutlery, models, and (as an alternative material to vinyl) phonograph records.

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, which can be controlled by photocrosslinking, is exploited for extrusion (as in Styrofoam) and also for molding and vacuum forming, since the material can cast in 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 oceans.