Editing Polystyrene (section)

{{short description|Polymer resin widely used in packaging}}
{{Other uses}}
{{Use dmy dates|date=October 2021}}
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| ImageFile = Polystyrene.svg
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| ImageName = Repeating unit of PS polymer chain
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| ImageFile1 = Polystyrene-chain-from-xtal-3D-bs-17.png
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| ImageFile2 = Polystyrene-chain-from-xtal-3D-sf.png
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| IUPACName = Poly(1-phenylethylene) 
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| OtherNames = Thermocol
|Section1={{Chembox Identifiers
| Abbreviations = PS
| CASNo = 9003-53-6
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|Section2={{Chembox Properties
| Formula = (C<sub>8</sub>H<sub>8</sub>)<sub>n</sub>
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| Density = 0.96–1.05&nbsp;g/cm<sup>3</sup>
| MeltingPt= ~
| MeltingPtC = 240
| MeltingPt_ref = <ref name="Wunsch2000">{{cite book|author=Wunsch, J.R. |title=Polystyrene – Synthesis, Production and Applications|url=https://books.google.com/books?id=9Oal8DG_7GAC&pg=PA15|access-date=25 July 2012|year=2000|publisher=iSmithers Rapra Publishing|isbn=978-1-85957-191-0|page=15}}</ref>
| MeltingPt_notes = for isotactic polystyrene
| ThermalConductivity = 0.033 W/(m·K) (foam, ρ 0.05 g/cm<sup>3</sup>){{sfn|Haynes|2011|p={{page needed|date=November 2017}}}}
| BoilingPtC = 430
| BoilingPt_notes = and depolymerizes
| Solubility = Insoluble
| SolubleOther = Soluble in benzene, carbon disulfide, chlorinated aliphatic hydrocarbons, chloroform, cyclohexanone, dioxane, ethyl acetate, ethylbenzene, MEK, NMP, THF<ref>{{cite book |doi=10.1016/B978-1-895198-47-8.50162-4 |chapter=PS polystyrene |title=Handbook of Polymers |pages=541–7 |year=2012 |last1=Wypych |first1=George |isbn=978-1-895198-47-8 }}</ref>
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| RefractIndex = 1.6; [[dielectric constant]] 2.6 (1 kHz – 1 GHz){{sfn|Haynes|2011|pp=13–17}}
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|Section4={{Chembox Thermochemistry
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|Section8={{Chembox Related
| OtherCompounds = [[Styrene]] (monomer)
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[[File:Expanded polystyrene foam dunnage.jpg|thumb|Expanded polystyrene packaging]]
[[File:Envase de yogur.jpg|thumb|A polystyrene yogurt container]]
[[File:Ps6cup.jpg|thumb|Bottom of a [[vacuum forming|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''') {{IPAc-en|ˌ|p|ɒ|l|i|ˈ|s|t|aɪ|r|iː|n}} is a synthetic [[polymer]] made from monomers of the [[Aromatic hydrocarbon|aromatic]] hydrocarbon [[styrene]].<ref>{{cite book|author1=John Scheirs|author2=Duane Priddy|title=Modern Styrenic Polymers: Polystyrenes and Styrenic Copolymers|url=https://books.google.com/books?id=FRGoFxKels4C&pg=PA3|date=28 March 2003|publisher=John Wiley & Sons|isbn=978-0-471-49752-3|page=3}}</ref> Polystyrene can be solid or [[foam]]ed. General-purpose polystyrene is clear, hard, and brittle. It is an inexpensive resin per unit weight. It is a poor barrier to air and water vapor and has a relatively low melting point.<ref name="acc">{{cite web|title=Common Plastic Resins Used in Packaging|url=http://plastics.americanchemistry.com/Education-Resources/Hands-on-Plastics/Introduction-to-Plastics-Science-Teaching-Resources/History-of-Polymers-Plastics-for-Teachers.html|website=Introduction to Plastics Science Teaching Resources|publisher=American Chemistry Council, Inc.|access-date=24 December 2012}}</ref> Polystyrene is one of the most widely used [[plastic]]s, with the scale of its production being several million tonnes per year.<ref name=Ullmann/> Polystyrene is naturally [[Transparency (optics)|transparent]], but can be colored with colorants. Uses include protective packaging (such as [[Foam peanut|packing peanuts]] and [[optical disc]] [[Optical disc packaging#Jewel case|jewel cases]]), containers, lids, bottles, trays, tumblers, [[disposable]] [[cutlery]],<ref name="acc"/> in the making of models, and as an alternative material for [[phonograph record]]s.<ref>{{cite web |title=Polystyrene phonograph record and process of manufacture |url=https://patents.google.com/patent/US2681323A/en |access-date=22 September 2021 |language=en |date=22 March 1949}}</ref>

As a [[thermoplastic]] polymer, polystyrene is in a solid (glassy) state at room temperature but flows if heated above about 100&nbsp;°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 (process)|molding]] and [[vacuum forming]], since it can be cast into molds with fine detail.  The temperatures behavior can be controlled by photocrosslinking.<ref>{{Cite journal |last1=Carroll |first1=Gregory T. |last2=Sojka |first2=Melissa E. |last3=Lei |first3=Xuegong |last4=Turro |first4=Nicholas J. |last5=Koberstein |first5=Jeffrey T. |date=2006-08-01 |title=Photoactive Additives for Cross-Linking Polymer Films: Inhibition of Dewetting in Thin Polymer Films |url=https://pubs.acs.org/doi/10.1021/la0611099 |journal=Langmuir |language=en |volume=22 |issue=18 |pages=7748–7754 |doi=10.1021/la0611099 |pmid=16922559 |issn=0743-7463|url-access=subscription }}</ref>

Under [[ASTM]] standards, polystyrene is regarded as not [[biodegradable]]. It is accumulating as a form of [[litter]] in the outside [[environment (biophysical)|environment]], particularly along shores and waterways, especially in its foam form, and in the Pacific Ocean.<ref>{{cite journal | vauthors = Kwon BG, Saido K, Koizumi K, Sato H, Ogawa N, Chung SY, Kusui T, Kodera Y, Kogure K | title = Regional distribution of styrene analogues generated from polystyrene degradation along the coastlines of the North-East Pacific Ocean and Hawaii | journal = Environmental Pollution | volume = 188 | pages = 45–9 | date = May 2014 | pmid = 24553245 | doi = 10.1016/j.envpol.2014.01.019 | bibcode = 2014EPoll.188...45K | display-authors = etal }}</ref>