Polystyrene
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|-
! colspan="2" align=center bgcolor="#cccccc" |'''Polystyrene'''
|-
|[[Density]]
|1050 [[kilogram per cubic metre|kg/m³]]
|-
|[[Density]] of [[Polystyrene#Expanded polystyrene|EPS]]
|25-200 [[kilogram per cubic metre|kg/m³]]
|-
|[[Specific Gravity]]
|1.05
|-
|[[Electrical conductivity]] (s)
|10<sup>-16</sup> [[siemens (unit)|S]]/[[metre|m]]
|-
|[[Thermal conductivity]] (k)
|0.08 [[Thermal conductivity|W/(m·K)]]
|-
|[[Young's modulus]] (''E'')
|3000-3600 [[Mega|M]][[Pascal (unit)|Pa]]
|-
|[[Tensile strength]] (''s''<sub>t</sub>)
|46–60 [[Mega|M]][[Pascal (unit)|Pa]]
|-
|Elongation at break
|3–4%
|-
|[[Notch]] test
|2–5 [[kilojoules|kJ]]/[[square metre|m²]]
|-
|[[Glass transition temperature|Glass temperature]]
|95 °[[Degree Celsius|C]]
|-
|[[Melting point]]<ref name="ILO-safety-card">[http://www.ilo.org/public/english/protection/safework/cis/products/icsc/dtasht/_icsc10/icsc1043.htm International Labour Organisation chemical safety card for polystyrene]</ref>
|240 °[[Degree Celsius|C]]
|-
|[[Vicat softening point|Vicat B]]
|90 °[[Degree Celsius|C]]<ref>A.K. van der Vegt & L.E. Govaert, Polymeren, van keten tot kunstof, ISBN 90-407-2388-5</ref>
|-
|[[Heat transfer coefficient]] (''Q'')
|0.17 W/([[metre|m]]<sup>2</sup>[[Kelvin|K]])
|-
|[[Coefficient of thermal expansion|Linear expansion coefficient (a)]]
|8 10<sup>-5</sup> /[[Kelvin|K]]
|-
|[[Specific heat capacity|Specific heat]] (''c'')
|1.3 kJ/(kg·K)
|-
|[[Absorption (chemistry)|Water absorption]] (ASTM)
|0.03–0.1
|-
|[[Decomposition]]
|X years, still decaying
|-
|}
'''Polystyrene''' {{IPAEng|ˌpɒliˈstaɪriːn}} ([[IUPAC]] Polyphenylethene) is an [[Aromaticity|aromatic]] [[polymer]] made from the aromatic [[monomer]] [[styrene]], a liquid [[hydrocarbon]] that is commercially manufactured from [[petroleum]] by the [[chemical industry]]. Polystyrene is a [[thermoplastic]] substance, normally existing in solid state at room temperature, but melting if heated (for [[Molding (process)|molding]] or extrusion), and becoming solid again when cooling off.
Pure solid polystyrene is a colorless, hard plastic with limited flexibility. It can be cast into molds with fine detail. Polystyrene can be [[Transparency (optics)|transparent]] or can be made to take on various colours. It is economical and is used for producing [[plastic model]] assembly kits, license plate frames, plastic cutlery, [[CD and DVD packaging|CD "jewel" cases]], and many other objects where a fairly rigid, economical plastic is desired.
==History==
Polystyrene was discovered in 1839 by [[Eduard Simon]],<ref>[http://inventors.about.com/od/pstartinventions/a/plastics.htm The history of plastics ]</ref> an apothecary in Berlin. From [[storax]], the resin of ''[[Liquidambar|Liquidambar orientalis]]'', he distilled an oily substance, a monomer which he named styrol. Several days later Simon found that the styrol had thickened, presumably from oxidation, into a jelly he dubbed styrol oxide ("Styroloxyd"). By 1845 English chemist [[John Blyth]] and German chemist [[August Wilhelm von Hofmann]] showed that the same transformation of styrol took place in the absence of oxygen. They called their substance metastyrol. Analysis later showed that it was chemically identical to Styroloxyd. In 1866 [[Marcelin Berthelot]] correctly identified the formation of metastyrol from styrol as a polymerization process. About 80 years went by before it was realized that heating of styrol starts a chain reaction which produces [[macromolecule]]s, following the thesis of German organic chemist [[Hermann Staudinger]] (1881–1965). This eventually led to the substance receiving its present name, polystyrene. The [[IG Farben|I. G. Farben]] company began manufacturing polystyrene in [[Ludwigshafen|Ludwigshafen, Germany]], about 1931, hoping it would be a suitable replacement for die cast zinc in many applications. Success was achieved when they developed a reactor vessel that extruded polystyrene through a heated tube and cutter, producing polystyrene in pellet form. Polystyrene is about as strong as unalloyed [[aluminium]], but much more flexible.
==Structure==
The chemical makeup of polystyrene is a long chain hydrocarbon with every other carbon connected to a [[Phenyl group]] (the name given to the aromatic ring [[benzene]], when bonded to complex carbon substituents).
<center>[[Image:Polystyrene formation.PNG]]</center>
A 3-D model would show that each of the [[chirality (chemistry)|chiral]] backbone carbons lies at the center of a [[tetrahedron]], with its 4 [[chemical bond|bonds]] pointing toward the vertices. Say the -C-C- bonds are rotated so that the backbone chain lies entirely in the plane of the diagram. From this flat schematic, it is not evident which of the [[phenyl]] (benzene) groups are angled toward us from the plane of the diagram, and which ones are angled away. The [[isomer]] where all of them are on the same side is called ''isotactic'' polystyrene, which is not produced commercially. Ordinary ''atactic'' polystyrene has these large phenyl groups [[randomness|randomly]] distributed on both sides of the chain. This random positioning prevents the chains from ever aligning with sufficient regularity to achieve any [[crystallinity]], so the plastic has no [[melting temperature]], ''T''<sub>m</sub>. But [[metallocene]]-[[catalysis|catalyzed]] [[polymerization]] can produce an ordered ''syndiotactic'' polystyrene with the phenyl groups on alternating sides. This form is highly crystalline with a ''T''<sub>m</sub> of 270 °C.
<span id="Expanded polystyrene">
==Solid foam==
[[Image:Expanded polysterene tray with tomato seedlings.jpg|thumb|250px|Expanded polysterene tray with tomato seedlings]]
[[Image:Styrofoam.jpg|thumb|Expanded polystyrene packaging material]]
Polystyrene's most common use is as expanded polystyrene (EPS). Expanded polystyrene is produced from a mixture of about 90-95% polystyrene and 5-10% gaseous [[blowing agent]], most commonly [[pentane]] or [[carbon dioxide]]<ref>[http://www.bpf.co.uk/bpfindustry/process_plastics_moulding_expanded_polystyrene.cfm process plastics Moulding Expanded Polystyrene<!-- Bot generated title -->]</ref>. The solid plastic is expanded into a foam through the use of heat, usually steam.
Extruded polystyrene (XPS), which is different from expanded polystyrene (EPS), is commonly known by the trade name [[Styrofoam]]. The voids filled with trapped air give it low [[thermal conductivity]]. This makes it ideal as a construction material and it is therefore sometimes used in [[structural insulated panel]] building systems. It is also used as [[Thermal insulation|insulation]] in building structures, as molded packing material for cushioning fragile equipment inside boxes, as [[packing peanuts|packing "peanuts"]], as non-weight-bearing architectural structures (such as [[column|pillars]]), and also in [[craft]]s and [[model (physical)|model]] building, particularly [[Architecture|architectural]] models. Foamed between two sheets of paper, it makes a more-uniform substitute for [[corrugated cardboard]], tradenamed [[Foamcore]]. A more unexpected use for the material is as a lightweight fill for embankments in the civil engineering industry.<ref>[http://www.vencel.co.uk/products/civil/design.htm Expanded polystyrene civil engineering products for roads, bridges and culverts: Vencel Resil<!-- Bot generated title -->]</ref>
Expanded polystyrene used to contain [[Chlorofluorocarbon|CFC]]s, but other, more environmentally-safe blowing agents are now used. Because it is an [[aromatic hydrocarbon]], it burns with an orange-yellow flame, giving off [[soot]], as opposed to non-aromatic hydrocarbon polymers such as [[polyethylene]], which burn with a light yellow flame (often with a blue tinge) and no soot.
Production methods include sheet stamping (PS) and [[injection molding]] (both PS and HIPS).
The density of expanded polystyrene varies greatly from around 25 kg/m³ to 200 kg/m³ depending on how much gas was admixed to create the foam. A density of 200 kg/m³ is typical for the expanded polystyrene used in [[surfboard]]s.<ref name="aw">{{cite web | author=Jed Norton | title=Blue Foam, Pink Foam and Foam Board | publisher=Antenociti's Workshop | url=http://www.barrule.com/workshop/images/info/foams/index.htm | accessdate=2008-01-29}}</ref>
==Standard markings==
The [[resin identification code]] symbol for polystyrene, developed by the [[Society of the Plastics Industry]] so that items can be labeled for easy recycling, is [[Image:Resin-identification-code-6-PS.svg|20px]] <!--The [[Unicode]] character is U+2678, which will appear here if you have a suitable font installed: <font size="6">♸</font>.-->. However, the majority of polystyrene products are currently not recycled because of a lack of suitable recycling facilities. Furthermore, when it is "recycled," it is not a closed loop — polystyrene cups and other packaging materials are usually recycled into fillers in other plastics, or other items that cannot themselves be recycled and are thrown away.
==Copolymers==
[[Image:Styropor in Mikroskop mit Polfilter.jpg|thumb|Structure of expanded polystyrene (microscope)]]
Pure polystyrene is [[toughness|brittle]], but [[hardness|hard]] enough that a fairly high-performance product can be made by giving it some of the properties of a stretchier material, such as [[polybutadiene]] rubber. The two such materials can never normally be mixed because of the amplified effect of [[Polymers#Intermolecular forces|intermolecular forces]] on polymer [[insolubility]] (see [[plastic recycling]]), but if polybutadiene is added during polymerization it can become chemically bonded to the polystyrene, forming a [[graft copolymer]] which helps to incorporate normal polybutadiene into the final mix, resulting in '''high-impact polystyrene''' or '''HIPS''', often called "high-impact plastic" in advertisements. One commercial name for HIPS is Bextrene. Common applications include use in toys and product casings. HIPS is usually [[Injection moulding|injection molded]] in production. Autoclaving polystyrene can compress and harden the material.
[[Acrylonitrile butadiene styrene]] or ABS plastic is similar to HIPS: a copolymer of '''a'''crylonitrile and '''s'''tyrene, toughened with poly'''b'''utadiene. Most electronics cases are made of this form of polystyrene, as are many sewer pipes. ABS pipes may become brittle over time. [[Styrene-acrylonitrile resin|SAN]] is a copolymer of styrene with [[acrylonitrile]] and [[styrene maleic anhydride|SMA]] one with [[maleic anhydride]].
Styrene can be copolymerized with other monomers; for example, [[divinylbenzene]] for cross-linking the polystyrene chains.
==Cutting and shaping==
[[Image:Polistirolo faccia.jpg|thumb|right|180px|Expanded polystyrene]]
Expanded polystyrene is very easily cut with a [[hot-wire foam cutter]], which is easily made by a heated taut length of wire, usually [[nichrome]] because of nichrome's resistance to oxidation at high temperatures and its suitable [[electrical conductivity]]. The hot wire foam cutter works by heating the wire to the point where it can vaporize foam immediately adjacent to it. The foam gets vaporized before actually touching the heated wire, which yields exceptionally smooth cuts.
Polystyrene, shaped and cut with hot wire foam cutters, is used in architecture models, [[actual signage]], amusement parks, movie sets, airplane construction, and much more. Such cutters may cost just a few dollars (for a completely manual cutter) to tens of thousands of dollars for large [[CNC]] machines that can be used in high-volume industrial production.
Polystyrene can also be cut with a traditional cutter. In order to do this without ruining the sides of the blade one must first dip the blade in water and cut with the blade at an angle of about 30º. The procedure has to be repeated multiple times for best results.
Polystyrene can also be cut on 3 and 5-axis routers, enabling large-scale prototyping and model-making. Special polystyrene cutters are available that look more like large cylindrical rasps.
==Use in biology==
Petri dishes and other containers such as test tubes, made of polystyrene, play an important role in biomedical research and science. For these uses, articles are almost always made by [[injection molding]], and often sterilized post molding, either by irradiation or treatment with [[ethylene oxide]]. Post mold surface modification, usually with oxygen rich plasmas, is often done to introduce polar groups. Much of modern biomedical research relies on the use of such products; they therefore play a critical role in pharmaceutical research.
==Finishing==
In the United States, environmental protection regulations prohibit the use of solvents on polystyrene (which would dissolve the polystyrene and de-foam most of foams anyway).
Some acceptable finishing materials are
* Water-based [[paint]] ([[artist]]s have created [[painting]]s on polystyrene with [[gouache]])
* [[Mortar (masonry)|Mortar]] or acrylic/cement render, often used in the building industry as a weather-hard overcoat that hides the foam completely after finishing the objects.
* Cotton wool or other fabrics used in conjunction with a stapling implement.
==Dangers and fire hazard==
[[Benzene]], a material used in the production of polystyrene, is a known human carcinogen. Moreover, butadiene and styrene (in ABS), when combined, become benzene-like in both form and function.{{Fact|date=February 2007}}<!-- commented out due to lack of cite: For this reason polystyrene is suspected to be carcinogenic in the same manner as benzene, although there is a lack of controlled studies to confirm this. -->
The [[United States Environmental Protection Agency|EPA]] claims <blockquote>
"Styrene is primarily used in the production of polystyrene plastics and resins. Acute (short-term) exposure to styrene in humans results in mucous membrane and eye irritation, and gastrointestinal effects. Chronic (long-term) exposure to styrene in humans results in effects on the central nervous system (CNS), such as headache, fatigue, weakness, and depression, CSN dysfunction, hearing loss, and peripheral neuropathy. Human studies are inconclusive on the reproductive and developmental effects of styrene; several studies did not report an increase in developmental effects in women who worked in the plastics industry, while an increased frequency of spontaneous abortions and decreased frequency of births were reported in another study. Several epidemiologic studies suggest there may be an association between styrene exposure and an increased risk of leukemia and lymphoma. However, the evidence is inconclusive due to confounding factors. EPA has not given a formal carcinogen classification to styrene."</blockquote><ref>[http://www.epa.gov/ttn/atw/hlthef/styrene.html Styrene | Technology Transfer Network Air Toxics Web site | US EPA<!-- Bot generated title -->]</ref>
Polystyrene is classified according to DIN4102 as a "B3" product, meaning highly flammable or "easily ignited". Consequently, though it is an efficient insulator at low temperatures, it is prohibited from being used in any exposed installations in [[building construction]] as long the material is not [[Flame retardant|flame retarded]] e.g. with [[hexabromocyclododecane]]. It must be concealed behind [[drywall]], sheet metal or [[concrete]]. Foamed plastic materials have been accidentally ignited and caused huge fires and losses. Examples include the [[Düsseldorf International Airport]], the [[Channel tunnel]], where it was inside a railcar and caught on fire, and the [[Browns Ferry Nuclear Power Plant]], where fire reached through a fire retardant, reached the foamed plastic underneath, inside a [[firestop]] that had not been tested and certified in accordance with the final installation.
In addition to fire hazard, substances that contain [[acetone]] (such as most [[Aerosol spray|aerosol paint spray]]s), and [[cyanoacrylate]] glues can dissolve polystyrene.
==Environmental concerns and bans==
Expanded polystyrene is not easily [[recyclable]] because of its light weight and low scrap value. It is generally not accepted in [[Kerbside collection|curbside]] programs. Expanded polystyrene foam takes 900 years to decompose in the environment {{Fact|date=May 2008}} and has been documented to cause starvation in birds and other marine wildlife.{{Fact|date=April 2008}} According to the [[California Coastal Commission]], it is a principal component of [[marine debris]]. Restricting the use of foamed polystyrene takeout food packaging is a priority of many solid waste environmentalist organizations, like [[Californians Against Waste]].<ref>{{cite news| url=http://www.recordnet.com/apps/pbcs.dll/article?AID=/20070921/A_NEWS/709210329| accessdate=2007-10-09|publisher=Stockton Record|date=21 September 2007| title= Business Gives Styrofoam a Rare Redemption.}}</ref>
The city of [[Berkeley, California]] was one of the first cities in the world to ban polystyrene food packaging (called Styrofoam in the media announcements).<ref>[http://www.berkeleydaily.org/text/article.cfm?archiveDate=12-06-01&storyID=8729 The Berkeley Daily Planet]</ref><ref>[http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2006/06/28/MNG65JLQJ411.DTL Styrofoam food packaging banned in Oakland]</ref> It was also banned in [[Portland, OR]], and [[Suffolk County, NY]] in 1990.<ref>[http://www.cawrecycles.org/issues/polystyrene_ordinances_list Californians Against Waste website]</ref> Now, over 20 US cities have banned polystyrene food packaging, including [[Oakland, CA]] on Jan 1st 2007.<ref>[http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2006/06/28/MNG65JLQJ411.DTL San Francisco Chronical article, June 28, 2006]</ref> [[San Francisco]] introduced a ban on the packaging on [[June 1]] 2007:<ref> [http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2006/11/07/BAGALM65AQ1.DTL&hw=styrofoam+ban&sn=003&sc=804 San Francisco Chronical article, November 7, 2006]</ref> <blockquote>"This is a long time coming. Polystyrene foam products rely on nonrenewable sources for production, are nearly indestructible and leave a legacy of pollution on our urban and natural environments. If [[McDonald's]] could see the light and phase out polystyrene foam more than a decade ago, it's about time San Francisco got with the program." Board of Supervisors President, Aaron Peskin<ref>[http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2006/06/27/BAG5VJKTS91.DTL&hw=styrofoam&sn=004&sc=367 San Francisco Chronical Article, June 27, 2006]</ref></blockquote>
The overall benefits of the ban in [[Portland, Oregon|Portland]] have been questioned,<ref>{{cite web |url=http://www.polystyrene.org/environment/Cascade1998_Portland.pdf |title=Paper Waste: Why Portland's Ban on Polystyrene Foam Products Has Been a Costly Failure |accessdate=2007-10-23 |last= Eckhardt|first=Angela |coauthors= |date=November, 1998 |work= |publisher=Cascade Policy Institute}}</ref> as have the general environmental concepts of the use of [[paper]] versus polystyrene.<ref>{{cite web
|url=http://www.loyno.edu/lucec/essays/heroes.html
|title=Where Might We Look for Environmental Heroes?
|last= Thomas|first=Robert A.
|publisher=Center for Environmental Communications, Loyola University, New Orleans
|date=[[March 8]] [[2005]]
|accessdate=2007-10-23
}}</ref>
A campaign to achieve the first ban of polystyrene foam from the food & beverage industry in Canada has been launched in [[Toronto]] as of January 2007, by local non-profit organization [[NaturoPack]].<ref>[http://naturopack.org/getittogogreenmain.html Naturopack Campaign Page]</ref>
The California and New York legislatures are currently considering bills which would effectively ban expanded polystyrene in all takeout food packaging state-wide.<ref>[http://www.cawrecycles.org/issues/current_legislation/ab904_07 AB 904]</ref>
==Explosives==
Polystyrene is used in some [[polymer-bonded explosive]]s:
<table class=wikitable>
<caption>Some Polystyrene PBX Examples</caption>
<tr><th>Name</th><th>Explosive Ingredients</th><th>Binder Ingredients</th><th>Usage</th></tr>
<tr><td>PBX-9205</td><td>[[RDX]] 92%</td><td>Polystyrene 6%; DOP 2%</td><td> </td></tr>
<tr><td>PBX-9007</td><td>[[RDX]] 90%</td><td>Polystyrene 9.1%; DOP 0.5%; resin 0.4%</td><td> </td></tr>
</table>
It is also a component of [[Napalm]] and a component of most designs of [[Teller-Ulam design|hydrogen bombs]].
==Cleaning==
Polystyrene can be [[Dishwasher|dishwashed]] at 70 °C without [[deformation]] since it has a [[glass transition temperature]] of 95 °C
==See also==
*[[Structural insulated panel]]
*[[ThermaSAVE]]
*[[Greatpac Sdn. Bhd.]]
== References==
{{reflist}}
==External links==
{{commons|Polystyrene|Polystyrene}}
*[http://www.pslc.ws/mactest/styrene.htm Polystyrene] - The University of Southern Mississippi
*[http://www.plasticsindustry.org/outreach/recycling/2124.htm SPI resin identification code] - Society of the Plastics Industry
*[http://www.dow.com/styrofoam/ Styrofoam] - the Dow trademarked name "Styrofoam"
*[http://www.sciam.com/article.cfm?chanID=sa003&articleID=0007B0AE-88AF-13FF-88AF83414B7F0000 Bacteria Turns Styrofoam into Biodegradable Plastic] - Scientific American, February 27, 2006
*[http://www.polystyrene.org Polystyrene.org] - Plastics foodservice packaging group
*[http://www.verdant.net/nofoam.htm Arguments against polystyrene] - verdant.net
*[http://www.cctplastics.com/polystyrene.html Polystyrene Data Sheet]
*[http://www.polystyrene.org/polystyrene_facts/facts.html Polystyrene (packaging) facts]
*[http://www.adm.uwaterloo.ca/infowast/watgreen/projects/library/f03biodegradeablesatstjeromes.pdf Biodegradable Alternatives for Styrofoam and Plastics - A Study at St. Jerome’s]
{{HealthIssuesOfPlastics}}
{{Plastics}}
[[Category:Plastics]]
[[Category:Packaging materials]]
[[Category:Household chemicals]]
[[Category:Insulators]]
[[Category:Organic polymers]]
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[[Category:Thermoplastics]]
[[Category:Recyclable materials]]
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