Expanded polystyrene

Polystyrene

Names
IUPAC name Poly(1-phenylethene)
Other names Thermocol
Identifiers
CAS Number	9003-53-6
Abbreviations	PS
ChemSpider	none
ECHA InfoCard	100.105.519
Properties
Chemical formula	(C8H8)n
Density	0.96–1.04 g/cm3
Melting point	~ 240 °C (464 °F; 513 K) (decomposes at lower temperature)
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

Polystyrene (PS) /ˌpɒliˈstaɪriːn/ 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 million tonnes 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.

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 behavior 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 very 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.