Editing Polytetrafluoroethylene (section)

== Properties ==
[[File:Blintzes in frying pan.jpg|thumb|right|PTFE is often used to coat [[non-stick pans]] as it is [[hydrophobic]] and possesses fairly high heat resistance.]]

PTFE is a [[thermoplastic]] [[polymer]], which is a white solid at room temperature, with a density of about 2200&nbsp;kg/m<sup>3</sup> and a melting point of {{convert|600|K}}.<ref name=chemours>{{cite web |title=Fluoroplastic Comparison - Typical Properties |url=https://www.chemours.com/Teflon_Industrial/en_US/tech_info/techinfo_compare.html |website=Chemours |archive-url= https://web.archive.org/web/20160203093128/https://www.chemours.com/Teflon_Industrial/en_US/tech_info/techinfo_compare.html |archive-date=3 February 2016 |url-status=dead}}</ref> It maintains high strength, toughness and self-lubrication at low temperatures down to {{convert|5|K|sigfig=4}}, and good flexibility at temperatures above {{convert|194|K|sigfig=4}}.<ref name=ptfe_handbook>[http://www.rjchase.com/ptfe_handbook.pdf Teflon PTFE Properties Handbook]. Retrieved 11 October 2012.</ref> PTFE gains its properties from the aggregate effect of [[carbon-fluorine bond]]s, as do all fluorocarbons. The only chemicals known to affect these carbon-fluorine bonds are highly reactive metals like the [[alkali metal]]s, at higher temperatures such metals as aluminium and magnesium, and fluorinating agents such as [[xenon difluoride]] and [[cobalt(III) fluoride]].<ref>{{cite web|url=https://plastechcoatings.com/chemours-teflon/|title= Chemours Teflon™ Coating Applications |website=plastechcoatings.com}}</ref> At temperatures above {{Convert|650|–|700|C|F|-1}} PTFE undergoes depolymerization.<ref>{{cite journal |author1=R. J. Hunadi |author2=K. Baum |title=Tetrafluoroethylene: A Convenient Laboratory Preparation |journal=Synthesis |year=1982 |volume=39 |issue=6 |page=454 |doi=10.1055/s-1982-29830|s2cid=96276938 }}</ref> However, it begins to decompose at about {{convert|260|C|}} through {{convert|350|C}}, and [[pyrolysis]] occurs at temperatures above {{Convert|400|C|F|abbr=on}}.<ref name=":3" />

{| class="wikitable"
|-
! Property
! Value
|-
| [[Glass transition temperature|Glass temperature]]
| {{Convert|114.85|C|F K}}<ref>{{cite book |last1=Nicholson |first1=John W. |title=The Chemistry of Polymers |date=2012 |publisher=Royal Society of Chemistry |isbn=978-1-84973-391-5 |page=50 |url=https://books.google.com/books?id=5XFsT69cX_YC&pg=PA50 }}</ref>
|-
| [[Thermal expansion]]
| 112–125×10<sup>−6</sup>&nbsp;K<sup>−1</sup><ref>{{cite web |url=http://www.engineershandbook.com/Tables/plasticthermalexp.htm |title=Reference Tables – Thermal Expansion Coefficients – Plastics |work=engineershandbook.com |access-date=2 January 2012 |archive-date=3 January 2012 |archive-url=https://web.archive.org/web/20120103183144/http://engineershandbook.com/Tables/plasticthermalexp.htm |url-status=dead }}</ref>
|-
| [[Thermal diffusivity]]
| 0.124&nbsp;mm{{sup|2}}/s<ref>{{cite journal |author1=Blumm, J. |author2=Lindemann, A. |author3=Meyer, M. |author4=Strasser, C. | title=Characterization of PTFE Using Advanced Thermal Analysis Technique |journal=[[International Journal of Thermophysics]]| volume=40 |issue=3–4 |page=311 | year=2011 |doi= 10.1007/s10765-008-0512-z |bibcode=2010IJT....31.1919B |s2cid=122020437 }}</ref>
|-
| [[Young's modulus]]
| 0.5&nbsp;GPa
|-
| [[Yield strength]]
| 23&nbsp;MPa
|-
| [[Coefficient of friction]]
| 0.05–0.10
|-
| [[Dielectric constant]]
| {{nowrap|ε {{=}} 2.1}}, {{nowrap|[[dissipation factor|tan(δ)]] < 5×10{{sup|−2}}}}
|-
| Dielectric constant (60&nbsp;Hz)
| {{nowrap|ε {{=}} 2.1}}, {{nowrap|[[dissipation factor|tan(δ)]] < 2×10{{sup|−2}}}}
|-
| [[Dielectric strength]] (1&nbsp;MHz)
| 60&nbsp;MV/m
|-
| [[Magnetic susceptibility]] (SI, 22&nbsp;°C)
| −10.28×10<sup>−6</sup><ref>{{cite journal |last1=Wapler |first1=M. C. |last2=Leupold |first2=J. |last3=Dragonu |first3=I. |last4=von Elverfeldt |first4=D. |last5=Zaitsev |first5=M. |last6=Wallrabe |first6=U. |title=Magnetic properties of materials for MR engineering, micro-MR and beyond |journal=JMR |date=2014 |volume=242 |pages=233–242 |doi=10.1016/j.jmr.2014.02.005 |arxiv=1403.4760 |bibcode=2014JMagR.242..233W |pmid=24705364|s2cid=11545416 }}</ref>
|}

The [[coefficient of friction]] of plastics is usually measured against polished steel.<ref>[http://www.matweb.com/reference/coefficient-of-friction.asp Coefficient of Friction (COF) Testing of Plastics]. MatWeb Material Property Data. Retrieved 1 January 2007.</ref> PTFE's coefficient of friction is 0.05 to 0.10,<ref name=chemours/> which is the third-lowest of any known solid material ([[aluminium magnesium boride]] (BAM) being the lowest, with a coefficient of friction of 0.02; [[diamond-like carbon]] being second-lowest at 0.05).{{cn|date=October 2024}} PTFE's resistance to [[van der Waals force]]s means that it is the only known surface to which a [[gecko]] cannot stick.<ref name="gecko">"[https://web.archive.org/web/20071014063923/http://socrates.berkeley.edu/~peattiea/research_main.html Research into Gecko Adhesion]",{{self-published inline|date=October 2024}} ''[[University of California, Berkeley|Berkeley]]'', 2007-10-14. Retrieved 8 April 2010.</ref> In addition, PTFE can be used to prevent insects from climbing up surfaces painted with the material. For example, PTFE is used to prevent ants from climbing out of [[formicarium|formicaria]]. There are [[Surface treatment of PTFE|surface treatments for PTFE]] that alter the surface to allow adhesion to other materials.

Because of its chemical and thermal properties, PTFE is often used as a gasket material within industries that require resistance to aggressive chemicals such as pharmaceuticals or chemical processing.<ref>{{cite web |url=http://www.gasketresources.com/ptfe-gaskets |title=PTFE Sheet |website=Gasket Resources Inc. |access-date=2017-08-16}}</ref> However, until the 1990s,<ref name="autogenerated655"/> PTFE was not known to crosslink like an [[elastomer]], due to its chemical inertness. Therefore, it has no "memory" and is subject to [[creep (deformation)|creep]]. Because of the propensity to creep, the long-term performance of such seals is worse than for elastomers that exhibit zero, or near-zero, levels of creep. In critical applications, [[Belleville washer]]s are often used to apply continuous force to PTFE gaskets, thereby ensuring a minimal loss of performance over the lifetime of the gasket.<ref>{{cite web |url=https://go.solonmfg.com/l/152611/2016-06-22/mlzyt/152611/15210/Using_Belleville_Springs_to_Maintain_Bolt_Preload.pdf |title=Using Belleville Springs To Maintain Bolt Preload |last=Davet |first=George P. |publisher=Solon Manufacturing Company }}</ref>

PTFE is an [[ultraviolet]] (UV) transparent polymer. However, when exposed to an [[excimer laser]] beam it severely degrades due to heterogeneous [[photothermal effect]].<ref>{{cite journal |last1=Ferry |first1=Laurent |last2=Vigier |first2=Gérard |last3=Bessede |first3=Jean Luc |title=Effect of Ultraviolet Radiation on Polytetrafluoroethylene: Morphology Influence |journal=Polymers for Advanced Technologies |date=May 1996 |volume=7 |issue=5–6 |pages=493–500 |doi=10.1002/(SICI)1099-1581(199605)7:5/6<493::AID-PAT536>3.0.CO;2-D }}</ref>