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,

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

Belgian waffles cooked in a Krampouz cast-iron waffle iron

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 impuri ...

carbon steel Carbon steel is a steel with carbon content from about 0.05 up to 2.1 percent by weight. The definition of carbon steel from the American Iron and Steel Institute (AISI) states: * no minimum content is specified or required for chromium, coba ...

stainless steel Stainless steel is an alloy of iron that is resistant to rusting and corrosion. It contains at least 11% chromium and may contain elements such as carbon, other nonmetals and metals to obtain other desired properties. Stainless steel's r ...

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, ...

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

(polytetrafluoroethylene or PTFE). PTFE was invented serendipitously by

Roy Plunkett Roy J. Plunkett (June 26, 1910 – May 12, 1994) was an American chemist. He discovered polytetrafluoroethylene (PTFE), better known as Teflon, in 1938. Personal life and education Plunkett was born in New Carlisle, Ohio and attended Newton Hi ...

in 1938, while working for a joint venture of the

DuPont DuPont de Nemours, Inc., commonly shortened to DuPont, is an American multinational chemical company first formed in 1802 by French-American chemist and industrialist Éleuthère Irénée du Pont de Nemours. The company played a major role in ...

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 gas used in development of the

atomic bomb A nuclear weapon is an explosive device that derives its destructive force from nuclear reactions, either fission (fission bomb) or a combination of fission and fusion reactions ( thermonuclear bomb), producing a nuclear explosion. Both 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 World War II by country, vast majority of the world's countries—including all of the great power ...

, 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

NYU Tandon School of Engineering The New York University Tandon School of Engineering (commonly referred to as Tandon) is the engineering and applied sciences school of New York University. Tandon is the second oldest private engineering and technology school in the United Sta ...

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 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 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, resistant to corrosion i ...

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 onto the pan surface, and then fired at to produce a non-stick ceramic coating.

PTFE (Teflon)

Polytetrafluoroethylene 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 ...

(PTFE) is a synthetic

fluoropolymer A fluoropolymer is a fluorocarbon-based polymer with multiple carbon–fluorine bonds. It is characterized by a high resistance to solvents, acids, and bases. The best known fluoropolymer is polytetrafluoroethylene under the brand name "Tefl ...

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 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 ...

, then sometimes electric-arc sprayed with

. 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 Hydrofluoric acid is a solution of hydrogen fluoride (HF) in water. Solutions of HF are colourless, acidic and highly corrosive. It is used to make most fluorine-containing compounds; examples include the commonly used pharmaceutical antidepres ...

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, r ...

compounds which can cause

polymer fume fever __NOTOC__ Polymer fume fever or fluoropolymer fever, also informally called Teflon flu, is an inhalation fever caused by the fumes released when polytetrafluoroethylene (PTFE, known under the trade name Teflon) reaches temperatures of 300 � ...

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 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 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 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 (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. 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 The Environmental Protection Agency (EPA) is an independent executive agency of the United States federal government tasked with environmental protection matters. President Richard Nixon proposed the establishment of EPA on July 9, 1970; it be ...

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. Super-hydrophobic coating

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 Deicing is the process of removing snow, ice or frost from a surface. Anti-icing is the application of chemicals that not only deice but also remain on a surface and continue to delay the reformation of ice for a certain period of time, or prev ...

and biofilm-resistant medical devices.

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.
PTFE Properties
Materials science Surface science Cookware and bakeware