John Gilbert (scientist)
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A non-stick surface is engineered to reduce the ability of other materials to stick to it. Non-stick cookware is a common application, where the non-stick coating allows food to brown without sticking to the pan. Non-stick is often used to refer to surfaces coated with polytetrafluoroethylene (PTFE), a well-known brand of which is
Teflon Polytetrafluoroethylene (PTFE) is a synthetic fluoropolymer of tetrafluoroethylene that has numerous applications. It is one of the best-known and widely applied PFAS. The commonly known brand name of PTFE-based composition is Teflon by Chemo ...
. In the twenty-first century, other coatings have been marketed as non-stick, such as
anodized aluminium Anodizing is an electrolytic passivation process used to increase the thickness of the natural oxide layer on the surface of metal parts. The process is called ''anodizing'' because the part to be treated forms the anode electrode of an elect ...
,
silica Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , most commonly found in nature as quartz and in various living organisms. In many parts of the world, silica is the major constituent of sand. Silica is ...
, enameled cast iron, and seasoned cookware.


Types


Seasoning

Cast iron Cast iron is a class of iron– carbon alloys with a carbon content more than 2%. Its usefulness derives from its relatively low melting temperature. The alloy constituents affect its color when fractured: white cast iron has carbide impur ...
, carbon steel, stainless steel and cast aluminium cookware may be seasoned before cooking by applying a fat to the surface and heating it to polymerize it. This produces a dry, hard, smooth,
hydrophobic In chemistry, hydrophobicity is the physical property of a molecule that is seemingly repelled from a mass of water (known as a hydrophobe). In contrast, hydrophiles are attracted to water. Hydrophobic molecules tend to be nonpolar and, t ...
coating, which is non-stick when food is cooked with a small amount of cooking oil or fat.


Fluoropolymer

The modern non-stick pans were made using a coating of
Teflon Polytetrafluoroethylene (PTFE) is a synthetic fluoropolymer of tetrafluoroethylene that has numerous applications. It is one of the best-known and widely applied PFAS. The commonly known brand name of PTFE-based composition is Teflon by Chemo ...
(polytetrafluoroethylene or PTFE). PTFE was invented
serendipitously Serendipity is an unplanned fortunate discovery. Serendipity is a common occurrence throughout the history of product invention and scientific discovery. Etymology The first noted use of "serendipity" was by Horace Walpole on 28 January 1754. I ...
by Roy Plunkett in 1938, while working for a joint venture of the DuPont company. The substance was found to have several unique properties, including very good corrosion-resistance and the lowest coefficient of friction of any substance yet manufactured. PTFE was first used to make seals resistant to the
uranium hexafluoride Uranium hexafluoride (), (sometimes called "hex") is an inorganic compound with the formula UF6. Uranium hexafluoride is a volatile white solid that reacts with water, releasing corrosive hydrofluoric acid. The compound reacts mildly with alumin ...
gas used in development of the atomic bomb during
World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposing ...
, and was regarded as a military secret. Dupont registered the Teflon trademark in 1944 and soon began planning for post-war commercial use of the new product. By 1951 Dupont had developed applications for Teflon in commercial bread and cookie-making; however, the company avoided the market for consumer cookware due to potential problems associated with release of toxic gases if stove-top pans were overheated in inadequately ventilated spaces. While working at DuPont, NYU Tandon School of Engineering alumnus John Gilbert was asked to evaluate a newly developed material called Teflon. His experiments using the fluorinated polymer as a surface coating for pots and pans helped usher in a revolution in non-stick cookware. A few years later, a French engineer had begun coating his fishing gear with Teflon to prevent tangles. His wife Colette suggested using the same method to coat her cooking pans. The idea was successful and a French patent was granted for the process in 1954. The
Tefal Tefal S.A.S. (a portmanteau of TEFlon and ALuminium.) is a French cookware and small appliance manufacturer, owned by Groupe SEB (a global manufacturer of cookware) since 1968 The year was highlighted by protests and other unrests t ...
company was formed in 1956 to manufacture non-stick pans. Not all non-stick pans use Teflon; other non-stick coatings have become available. For example, a mixture of
titanium Titanium is a chemical element with the Symbol (chemistry), symbol Ti and atomic number 22. Found in nature only as an oxide, it can be reduced to produce a lustrous transition metal with a silver color, low density, and high strength, resista ...
and
ceramic A ceramic is any of the various hard, brittle, heat-resistant and corrosion-resistant materials made by shaping and then firing an inorganic, nonmetallic material, such as clay, at a high temperature. Common examples are earthenware, porcelain ...
can be
sandblasted Sandblasting, sometimes known as abrasive blasting, is the operation of forcibly propelling a stream of abrasive material against a surface under high pressure to smooth a rough surface, roughen a smooth surface, shape a surface or remove su ...
onto the pan surface, and then fired at to produce a non-stick ceramic coating.


PTFE (Teflon)

Polytetrafluoroethylene (PTFE) is a synthetic fluoropolymer used in various applications including non-stick coatings. Teflon is a brand of PTFE, often used as a generic term for PTFE. The metallic substrate is roughened by abrasive blasting, then sometimes electric-arc sprayed with stainless steel. The irregular surface promotes adhesion of the PTFE and also resists abrasion of the PTFE. Then one to seven layers of PTFE are sprayed or rolled on, with a larger number of layers and spraying being better. The number and thickness of the layers and quality of the material determine the quality of the non-stick coating. Better-quality coatings are more durable, and less likely to peel and flake, and keep their non-stick properties for longer. Any PTFE-based coating will rapidly lose its non-stick properties if overheated; all manufacturers recommend that temperatures be kept below, typically, . Utensils used with PTFE-coated pans can scratch the coating, if the utensils are harder than the coating; this can be prevented by using non-metallic (usually plastic or wood) cooking tools.


Health concerns

When pans are overheated beyond approximately 350 °C (660 °F) the PTFE coating begins to dissociate, releasing hydrofluoric acid and a variety of
organofluorine Organofluorine chemistry describes the chemistry of the organofluorines, organic compounds that contain the carbon–fluorine bond. Organofluorine compounds find diverse applications ranging from oil and water repellents to pharmaceuticals, ref ...
compounds which can cause polymer fume fever in humans and can be lethal to birds. Concerns have been raised over the possible negative effects of using PTFE-coated cooking pans. Processing of PTFE in the past used to include
PFOA Perfluorooctanoic acid (PFOA; conjugate base perfluorooctanoate; also known colloquially as C8, for its 8 carbon chain structure) is a perfluorinated carboxylic acid produced and used worldwide as an industrial surfactant in chemical processes a ...
as an emulsifier; however, PFOA is a
persistent organic pollutant Persistent organic pollutants (POPs), sometimes known as "forever chemicals", are organic compounds that are resistant to environmental degradation through chemical, biological, and photolytic processes. They are toxic chemicals that adversel ...
and poses both environmental and health concerns, and is now being phased out of use in PTFE processing. PFOA is now replaced by the
GenX The General Electric GEnx ("General Electric Next-generation") is an advanced dual rotor, axial flow, high-bypass turbofan jet engine in production by GE Aviation for the Boeing 787 and 747-8. The GEnx is intended to succeed the CF6 in GE's pro ...
product manufactured by the DuPont spin-off Chemours, which seems to pose similar health issues as the now banned PFOA.


Culinary uses and limitations

With other types of pans, some
oil An oil is any nonpolar chemical substance that is composed primarily of hydrocarbons and is hydrophobic (does not mix with water) & lipophilic (mixes with other oils). Oils are usually flammable and surface active. Most oils are unsaturated ...
or fat is required to prevent hot food from sticking to the pan's surface. Food does not have the same tendency to stick to a non-stick surface; pans can be used with less, or no oil, and are easier to clean as residues do not stick to the surface. According to writer Tony Polombo, pans that are not non-stick are better for producing pan gravy, because the
fond In the culinary arts, fond is a contraction of ''fonds de cuisine'' which is loosely described as "the foundation and working capital of the kitchen". It refers to a flavorful liquid that is used as foundation (''fondation'' in French, hence the ...
(the caramelized drippings that stick to the pan when meat is cooked) sticks to them, and can be turned into pan gravy by deglazing them—dissolving them in liquid.


Ceramic

Ceramic nonstick pans use a finish of silica (silicon dioxide) to prevent sticking. It is applied using a sol-gel process without the use of
PFAS Per- and polyfluoroalkyl substances (PFASs) are synthetic organofluorine chemical compounds that have multiple fluorine atoms attached to an alkyl chain. An early definition, from 2011, required that they contain at least one perfluoroalkyl mo ...
. GreenPan was the first company to create ceramic nonstick cookware. The coating layer starts to break down when heated to 426°C (800°F). With the EPA imposing stricter limits on the use of PFAS, some companies like OXO are voluntarily replacing their PTFE cookware with ceramic options.


Superhydrophobic

A superhydrophobic coating is a thin surface layer that repels water. It is made from superhydrophobic ( ultrahydrophobicity) materials. Droplets hitting this kind of coating can fully rebound.Richard, Denis, Christophe Clanet, and David Quéré. "Surface phenomena: Contact time of a bouncing drop." Nature 417.6891 (2002): 811-811Yahua Liu, Lisa Moevius, Xinpeng Xu,Tiezheng Qian, Julia M Yeomans, Zuankai Wang. "Pancake bouncing on superhydrophobic surfaces." Nature Physics, 10, 515-519 (2014) Generally speaking, superhydrophobic coatings are made from composite materials where one component provides the roughness and the other provides low surface energy.


Liquid-impregnated surface

A liquid-impregnated surface consists of two distinct layers. The first is a highly textured or porous substrate with features spaced sufficiently close to stably contain the second layer which is an impregnating liquid that fills in the spaces between the features. The liquid must have a surface energy well-matched to the substrate in order to form a stable film. These surfaces bioimitate the carnivorous Venezuelan pitcher plant, which uses microscale hairs to create a water slide that causes ants to slip to their death. Slippery surfaces are finding applications in commercial products, anti-fouling surfaces, anti-icing and biofilm-resistant medical devices.


See also

* Cooking spray *
Aluminium magnesium boride Aluminum magnesium boride or Al3Mg3B56 colliqually known as BAM is a chemical compound of aluminium, magnesium and boron. Whereas its nominal formula is AlMgB14, the chemical composition is closer to Al0.75Mg0.75B14. It is a ceramic alloy that is h ...
*
Forever chemicals Per- and polyfluoroalkyl substances (PFASs) are synthetic Organofluorine chemistry, organofluorine chemical compounds that have multiple fluorine atoms attached to an alkyl chain. An early definition, from 2011, required that they contain at l ...


References


External links


How non-stick pan works"Science plans 'non-stick' submarine", ''bbc.co.uk'', 10 October, 2003
*{{cite web , url=http://news.bbc.co.uk/2/hi/science/nature/6993719.stm , title='Virtually non-stick' gum created , author=Rebecca Morelle , author-link=Rebecca Morelle , author2=Liz Seward , author2-link=Liz Seward, website=BBC News , date=13 September 2007

from
How Stuff Works HowStuffWorks is an American commercial infotainment website founded by professor and author Marshall Brain, to provide its target audience an insight into the way many things work. The site uses various media to explain complex concepts, termin ...
.
PTFE Properties
Materials science Surface science Cookware and bakeware