Non-stick surface

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Food in a non-stick pan Blintzes in frying pan.jpg
Food in a non-stick pan

A 'non-stick surface' is engineered to reduce the ability of other materials to stick to it. Non-sticking 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. In the twenty-first century, other coatings have been marketed as non-stick, such as anodized aluminium, silica, enameled cast iron, and seasoned cookware.

Contents

Types

Seasoning

Cast iron skillets, before seasoning (left) and after several years of use (right) Castiron-skillets.jpg
Cast iron skillets, before seasoning (left) and after several years of use (right)
Commercial waffle iron requiring seasoning Belgian waffles cooked in a Krampouz cast-iron waffle iron.JPG
Commercial waffle iron requiring seasoning

Cast iron, carbon steel, [1] stainless steel [2] and cast aluminium cookware[ citation needed ] 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 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 or PTFE). PTFE was invented serendipitously by Roy Plunkett in 1938, [3] [4] 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 gas used in development of the atomic bomb during World War II, 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. [5]

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. [6] [7]

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. [5]

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. [8] [9] The irregular surface promotes adhesion of the PTFE and also resists abrasion of the PTFE. [10] Then one to seven layers of PTFE are sprayed or rolled on. The number and thickness of the layers and quality of the material determine the quality of the non-stick coating, with more layers being better. [11] 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, 260 °C (500 °F). [12]

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 260°C (500°F) the PTFE coating begins to dissociate, releasing hydrofluoric acid and a variety of organofluorine 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. [5] [13] [14] [15]

Processing of PTFE in the past used to include PFOA as an emulsifier; however, PFOA is a persistent organic pollutant and poses both environmental and health concerns, and is now being phased out of use in PTFE processing. [16]

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. [17]

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. [18]

Ceramic

Not all non-stick pans use Teflon; other non-stick coatings have become available. For example, a mixture of titanium and ceramic can be sandblasted onto the pan surface, and then fired at 2,000 °C (3,630 °F) to produce a non-stick ceramic coating. [19]

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. [20] The coating layer of Ceramic nonstick pans starts to break down at about 370 °C (700 °F). [21] The coating layer of PTFE cookware starts to break down when heated to 260 °C.

With the EPA imposing stricter limits on the use of PFAS, [22] some companies are voluntarily replacing their PTFE cookware with ceramic options. [23]

Xylan

Xylan is a trademarked fluoropolymer‑based industrial coating, most commonly used in non-stick cookware. Xylan is formulated as a composite system that typically combines one or more fluoropolymers—such as PTFE, perfluoroalkoxy alkane (PFA), and fluorinated ethylene propylene (FEP)—with specialized binder resins to improve adhesion and wear resistance. [24] [25]

Other

Various other proprietary fluoropolymer‑based coatings exist, such as Starflon by Tramontina which is a nonstick coating marketed as "PFAS free" but still developed using PTFE. [26] [27]

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. [28] [29] Generally speaking, superhydrophobic coatings are made from composite materials where one component provides the roughness and the other provides low surface energy. [30]

This image shows highly absorbent filter paper coated with a super-hydrophobic paint developed at University College London. This repels water (which has been dyed orange for greater contrast) Super-hydrophobic coating.jpg
This image shows highly absorbent filter paper coated with a super-hydrophobic paint developed at University College London. This repels water (which has been dyed orange for greater contrast)

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. [31] The liquid must have a surface energy well-matched to the substrate in order to form a stable film. [32] 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

Related Research Articles

<span class="mw-page-title-main">Polytetrafluoroethylene</span> Synthetic polymer

Polytetrafluoroethylene (PTFE) is a synthetic fluoropolymer of tetrafluoroethylene, and has numerous applications because it is chemically inert. The commonly known brand name of PTFE-based composition is Teflon by Chemours, a spin-off from DuPont, which originally invented the compound in 1938. Polytetrafluoroethylene is a fluorocarbon solid, as it is a high-molecular-weight polymer consisting wholly of carbon and fluorine. PTFE is hydrophobic: neither water nor water-containing substances wet PTFE, as fluorocarbons exhibit only small London dispersion forces due to the low electric polarizability of fluorine. PTFE has one of the lowest coefficients of friction of any solid.

<span class="mw-page-title-main">Gore-Tex</span> Trademark for a waterproof, breathable fabric

Gore-Tex is W. L. Gore & Associates's trade name for waterproof, breathable fabric membrane. It was invented in 1969. Gore-Tex blocks liquid water while allowing water vapor to pass through and is designed to be a lightweight, waterproof fabric for all-weather use. It is composed of expanded PTFE (ePTFE), a stretched out form of the PFAS compound polytetrafluoroethylene (PTFE).

<span class="mw-page-title-main">Cookware and bakeware</span> Food preparation containers

Cookware and bakeware is food preparation equipment, such as cooking pots, pans, baking sheets etc. used in kitchens. Cookware is used on a stove or range cooktop, while bakeware is used in an oven. Some utensils are considered both cookware and bakeware.

<span class="mw-page-title-main">Perfluorooctanoic acid</span> Perfluorinated carboxylic acid

Perfluorooctanoic acid is a perfluorinated carboxylic acid produced and used worldwide as an industrial surfactant in chemical processes and as a material feedstock. PFOA is considered a surfactant, or fluorosurfactant, due to its chemical structure, which consists of a perfluorinated, n-heptyl "tail group" and a carboxylic acid "head group". The head group can be described as hydrophilic while the fluorocarbon tail is both hydrophobic and lipophobic.

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 "Teflon," trademarked by the DuPont Company.

SilverStone is a non-stick plastic coating made by DuPont. Released in 1976, this three-coat (primer/midcoat/topcoat) fluoropolymer system formulated with PTFE and PFA produces a more durable finish than Teflon coating.

<span class="mw-page-title-main">Cast-iron cookware</span> Cookware valued for heat retention properties

Heavy-duty cookware made of cast iron is valued for its heat retention, durability, ability to maintain high temperatures for longer time duration, and non-stick cooking when properly seasoned. Seasoning is also used to protect bare cast iron from rust. Types of cast-iron cookware include frying pans, dutch ovens, griddles, waffle irons, flattop grills, panini presses, crepe makers, deep fryers, tetsubin, woks, potjies, and karahi.

<span class="mw-page-title-main">Fluorinated ethylene propylene</span> Polymer

Fluorinated ethylene propylene (FEP) is a copolymer of hexafluoropropylene and tetrafluoroethylene. It differs from the polytetrafluoroethylene (PTFE) resins in that it is melt-processable using conventional injection molding and screw extrusion techniques. Fluorinated ethylene propylene was invented by DuPont and is sold under the brandname Teflon FEP. Other brandnames are Neoflon FEP from Daikin or Dyneon FEP from Dyneon/3M.

Perfluoroethers are a class of organofluorine compound containing one or more ether functional group. In general these compounds are structurally analogous to the related hydrocarbon ethers, except for the distinctive properties of fluorocarbons.

<span class="mw-page-title-main">Perfluorinated compound</span> Type of organic chemical

A perfluorinated compound (PFC) or perfluoro compound is an organofluorine compound that lacks C-H bonds. Many perfluorinated compounds have properties that are quite different from their C-H containing analogues. Common functional groups in PFCs are OH, CO2H, chlorine, O, and SO3H. Electrofluorination is the predominant method for PFC production. Due to their chemical stability, some of these perfluorinated compounds bioaccumulate.

<span class="mw-page-title-main">Frying pan</span> Flat bottomed pan for cooking food on a stove

A frying pan, frypan, or skillet is a flat-bottomed pan used for frying, searing, and browning foods. It is typically 20 to 30 cm in diameter with relatively low sides that flare outwards, a long handle, and no lid. Larger pans may have a small grab handle opposite the main handle. A pan of similar dimensions, but with less flared, more vertical sides and often with a lid, is called a sauté pan. While a sauté pan can be used as a frying pan, it is designed for lower-heat cooking.

<span class="mw-page-title-main">Seasoning (cookware)</span> Process of treating the surface of cooking vessels with oil

Seasoning is the process of coating the surface of cookware with fat which is heated in order to produce a corrosion resistant layer of polymerized fat. It is required for raw cast-iron cookware and carbon steel, which otherwise rust rapidly in use, but is also used for many other types of cookware. An advantage of seasoning is that it helps prevent food sticking.

Xylan is a fluoropolymer-based industrial coating, most commonly used in non-stick cookware. Generally, it is applied in a thin film to the target material to improve its durability and non-stick properties.

In cooking several factors, including materials, techniques, and temperature, can influence the surface chemistry of the chemical reactions and interactions that create food. All of these factors depend on the chemical properties of the surfaces of the materials used. The material properties of cookware, such as hydrophobicity, surface roughness, and conductivity can impact the taste of a dish dramatically. The technique of food preparation alters food in fundamentally different ways, which produce unique textures and flavors. The temperature of food preparation must be considered when choosing the correct ingredients.

<span class="mw-page-title-main">Superhydrophobic coating</span> Water-repellant coating

A superhydrophobic coating is a thin surface layer that repels water. It is made from superhydrophobic materials, and typically cause an almost imperceptibly thin layer of air to form on top of a surface. Droplets hitting this kind of coating can fully rebound. Generally speaking, superhydrophobic coatings are made from composite materials where one component provides the roughness and the other provides low surface energy.

<span class="mw-page-title-main">Fluorochemical industry</span> Industry dealing with chemicals from fluorine

The global market for chemicals from fluorine was about US$16 billion per year as of 2006. The industry was predicted to reach 2.6 million metric tons per year by 2015. The largest market is the United States. Western Europe is the second largest. Asia Pacific is the fastest growing region of production. China in particular has experienced significant growth as a fluorochemical market and is becoming a producer of them as well. Fluorite mining was estimated in 2003 to be a $550 million industry, extracting 4.5 million tons per year.

<span class="mw-page-title-main">Swiss Diamond International</span>

Swiss Diamond International is a Swiss based cookware company. It is a privately held company, headquartered in Sierre, Switzerland and founded in 2001.

<span class="mw-page-title-main">Perfluoroalkoxy alkane</span> Family of polymers

Perfluoroalkoxy alkanes (PFA) are fluoropolymers. They are copolymers of tetrafluoroethylene (C2F4) and perfluoroethers (C2F3ORf, where Rf is a perfluorinated group such as trifluoromethyl (CF3)). The properties of these polymers are similar to those of polytetrafluoroethylene (PTFE). Compared to PTFE, PFA has better anti-stick properties and higher chemical resistance, at the expense of lesser scratch resistance.

The Chemours Company is an American chemical company that was founded in July 2015 as a spin-off from DuPont. It has its corporate headquarters in Wilmington, Delaware, United States. Chemours is the manufacturer of Teflon, the brand name of polytetrafluoroethylene (PTFE), known for its anti-stick properties. It also produces titanium dioxide and refrigerant gases. It is currently being sued by the PA Attorney General, for knowingly exposing the public to PFAS.

This timeline of events related to per- and polyfluoroalkyl substances (PFASs) includes events related to the discovery, development, manufacture, marketing, uses, concerns, litigation, regulation, and legislation, involving the human-made PFASs. The timeline focuses on some perfluorinated compounds, particularly perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) and on the companies that manufactured and marketed them, mainly DuPont and 3M. An example of PFAS is the fluorinated polymer polytetrafluoroethylene (PTFE), which has been produced and marketed by DuPont under its trademark Teflon. GenX chemicals and perfluorobutanesulfonic acid (PFBS) are organofluorine chemicals used as a replacement for PFOA and PFOS.

References

  1. ↑ How to Season a Wok- Serious Eats
  2. ↑ "How to Turn a Stainless Steel Skillet into a Nonstick Pan". 23 March 2017.
  3. ↑ "Roy J. Plunkett". Science History Institute . June 2016. Retrieved 21 February 2018.
  4. ↑ Center for Oral History. "Roy J. Plunkett". Science History Institute . Retrieved 21 February 2018.
  5. 1 2 3 Anne Cooper Funderburg. "Making Teflon Stick". Invention and Technology Magazine . Summer 2000. 16 (1). Retrieved 2015-02-21.
  6. ↑ "Inspired by teflon, researchers create super durable proteins".
  7. ↑ "Invention, Innovation and Entrepreneurship Begin at the NYU Polytechnic School of Engineering". 21 April 2014.
  8. ↑ Nicholas J. Wall, US 5069937 "Thermal spraying of stainless steel", 1988
  9. ↑ Laurence W. McKeen, Fluorinated coatings and finishes handbook, 2006, p. 117
  10. ↑ Excalibur brochure, PDF
  11. ↑ "Cooking For Engineers". Cookingforengineers.com. Retrieved 23 January 2016.
  12. ↑ "Cookware Safety by Teflon nonstick coatings". Chemours Web site. Retrieved 23 January 2016.
  13. ↑ "Safety of Teflon Non-Stick Coatings for Cookware". DuPont. Archived from the original on 2008-01-17. Retrieved 2009-05-06.
  14. ↑ American Cancer Society, Teflon and Perfluorooctanoic Acid (PFOA)
  15. ↑ Tugend, Alina (October 14, 2006). "Teflon Is Great for Politicians, but Is It Safe for Regular People?". New York Times. Retrieved 15 September 2013.
  16. ↑ Juliet Eilperin: Harmful Teflon Chemical To Be Eliminated by 2015. The Washington Post, 2006-01-26
  17. ↑ "Basic Information on PFAS". PFOA, PFOS and Other PFASs. Washington, D.C.: U.S. Environmental Protection Agency (EPA). 2018-02-18.
  18. ↑ Tony Polombo (2006). "Pots and Pans". Cooking - A Basic Repertoire. iUniverse. p. 20. ISBN   9780595378661.
  19. ↑ Pennie Stoyles and Peter Pentland (2007). "Non-stick pan". A to Z of Inventions and Inventors: M to P. Black Rabbit Books. pp.  17. ISBN   9781583407899.
  20. ↑ "You Can't Always Trust Claims on 'Non-Toxic' Cookware". Consumer Reports. 26 October 2022. Retrieved 2022-11-11.
  21. ↑ trk (2020-07-28). "Is Nonstick Cookware Safe?". the rational kitchen. Retrieved 2023-07-20.
  22. ↑ "EPA imposes stricter limits on four types of toxic 'forever chemicals'". the Guardian. 2022-06-15. Retrieved 2022-11-11.
  23. ↑ Ray, Joe. "Teflon Nonstick Pans Are Bad. Consider These Alternatives". Wired. ISSN   1059-1028 . Retrieved 2022-11-11.
  24. ↑ "Xylan". PTFE Applied Coatings. Retrieved 2025-02-04.
  25. ↑ "Xylan coatings | fluropolymer & fluroploymer hybrid coatings". www.impreglon.co.uk. Retrieved 2025-02-04.
  26. ↑ trk (2018-12-13). "Nonstick Cookware Brands: PTFE (Teflon®) or Ceramic? A Comprehensive Guide". the rational kitchen. Retrieved 2025-02-04.
  27. ↑ "Blog | Understand the meaning of nonstick, Starflon and triple-bottom". Tramontina Global (in Brazilian Portuguese). Retrieved 2025-02-04.
  28. ↑ Richard, Denis, Christophe Clanet, and David Quéré. "Surface phenomena: Contact time of a bouncing drop." Nature 417.6891 (2002): 811-811
  29. ↑ Yahua Liu, Lisa Moevius, Xinpeng Xu, Tiezheng Qian, Julia M Yeomans, Zuankai Wang. "Pancake bouncing on superhydrophobic surfaces." Nature Physics, 10, 515-519 (2014)
  30. ↑ Simpson, John T.; Hunter, Scott R.; Aytug, Tolga (2015). "Superhydrophobic materials and coatings: a review". Reports on Progress in Physics. 78 (8): 086501. Bibcode:2015RPPh...78h6501S. doi:10.1088/0034-4885/78/8/086501. PMID   26181655. S2CID   206022154.
  31. ↑ "US Patent # US 20130032316 A1". US Patent. USPTO. Retrieved 18 October 2013.
  32. ↑ Aizenberg, Joanna; Grinthal, Alison; Hatton, Benjamin D.; Smythe, Elizabeth J.; Tang, Sindy K. Y.; Kang, Sung Hoon; Wong, Tak-Sing (September 2011). "Bioinspired self-repairing slippery surfaces with pressure-stable omniphobicity". Nature. 477 (7365): 443–447. Bibcode:2011Natur.477..443W. doi:10.1038/nature10447. ISSN   1476-4687. PMID   21938066. S2CID   4300247.
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