Despite persistent claims to the contrary, Teflon did not appear as a by-product of the space program. Teflon is a brand name for polytetrafluoroethylene (PTFE), or fluoropolymer resin. Teflon was discovered completely by accident by Dr. Roy Plunkett in 1938. It went on commercial sale in 1946.
Polytetrafluoroethylene, or fluoroplastic-4, better known under the brand name "Teflon", is a polymer of tetrafluoroethylene (PTFE), a plastic with rare physical and chemical properties and is widely used in technology and in everyday life.
The word "Teflon" is a registered trademark of the American chemical company Chemours, a spin-off company of DuPont Corporation.
In April 1938, 27-year-old chemist Roy Plunkett of Kinetic Chemicals, while experimenting with gases belonging to the group of refrigerants (such as freon), discovered that a sample left under the influence of cold turned into a whitish waxy solid overnight with some interesting properties. Not only did the material have an unusually slippery surface, but it proved to be remarkably resistant to virtually all chemicals and solvents, including highly corrosive acids.
In 1941, Kinetic Chemicals was granted a patent for Teflon, and in 1949 it became a division of the American company DuPont. The new discovery was quickly put to practical use, first in the Manhattan Project (the codename for the 1942-1946 nuclear weapons program), and then in kitchen utensils.
To date, no one has been able to pinpoint the origin of the "cosmonautics" myth, except perhaps that the Apollo space program depended heavily on Teflon for cable insulation.
Other misconceptions about Teflon include the myth that Teflon-coated bullets are much better at penetrating body armor than any other bullets. In fact, the purpose of the Teflon coating is to reduce wear on the inside surface of the gun barrel, which has nothing to do with the effectiveness of the bullet itself.
Teflon does indeed have the lowest coefficient of friction of any known hard material, which is why it works so well as a non-stick coating for kitchen pans.
But if Teflon is so slippery, how is it made to stick to the pan? The process requires preliminary sandblasting, as a result of which many small scratches form on the surface of the pan, on which liquid Teflon is sprayed in a thin layer. All this is dried under the influence of high temperatures, Teflon hardens and seizes securely. Then it is coated with a special sealant and subjected to repeated heat treatment.
Next, we will consider in detail in which areas of human activity Teflon is used and how safe it is for our health.
Where else is Teflon used?
Teflon is a white, transparent substance in a thin layer, resembling paraffin or polyethylene in appearance. It has high heat and frost resistance, remains flexible and elastic at temperatures from -70 to +270 °C, an excellent insulating material. Teflon has very low surface tension and adhesion and is not wetted by water, fats or most organic solvents.
Fluoroplastic is a soft and fluid material, therefore it has limited use in loaded structures. It has very low adhesion (stickiness). DuPont lists the melting point for different types of Teflon from 260 °C to 327°C.
Teflon is used in the chemical, electrical and food industries, for the production of membrane clothing, in medicine, in vehicles, for military purposes, mainly as coatings. Fluoropolymers are best known for their widespread use in non-stick cookware. So, let's look at the main areas of application of this unique substance.
1. Food industry and life
Due to its low adhesion, non-wetting and heat resistance, Teflon in the form of a non-stick coating is widely used for the manufacture of extrusion molds and baking dishes, as well as frying pans and pots.
Teflon is also used in the manufacture of other household appliances. Teflon coating in the form of the thinnest film is applied to razor blades, which significantly prolongs their life and makes shaving easier.
Teflon coated cookware care
The Teflon coating does not have great strength, therefore, when cooking in such dishes, only soft – wooden, plastic or plastic-coated – accessories (shovels, ladles, etc.) should be used. Teflon-coated dishes should be washed in warm water with a soft sponge, with the addition of liquid detergent, without the use of abrasive sponges or cleaning pastes, and avoid overheating up to 415 °C and frying over high heat.
Interesting history of the Tefal brand
In 1954, French engineer Marc Gregoire discovered a method for applying polytetrafluoroethylene (Teflon) to aluminum. Thus the first non-stick pan was invented. Two years later, in 2, Tefal was founded in Sarcelles (France).
By the end of 1956, the new facility was turning out 100 pans a day. The invention was sold under the slogan "TEFAL Frying Pan – the first frying pan that really does not burn." By 1961, demand for Tefal pans reached 1 million units per month.
In 1968, Tefal became France's leading cookware manufacturer with sales of 49 million francs. And in the same year, the French group of companies for the production of household appliances Groupe SEB concludes a deal to acquire Tefal. Throughout its history, SEB has expanded its Tefal brand product range with new technologies and appliances for the home.
In 2009, Tefal produced its one billionth frying pan.
2. Industry and technology
In various industries, fibers derived from polytetrafluoroethylene (Teflon) have found wide application as high-temperature bag filters, various types of heat-resistant gaskets, threads for textile fabrics, as well as in automotive equipment, general-purpose industrial filters, elements of shut-off and control valves, agitators and pumps, filtration and separation equipment.
In aviation, for example, Teflon is used to make flexible metal-plastic pipelines for hydraulic systems operating under high pressure (more than 200 kgf / cm²) and with a high temperature of the working fluid.
F-4 brand fluoroplastic can be used to produce distillation columns, pumps, pipes, valves, bellows, facing tiles, gland packings. As a dielectric, polytetrafluoroethylene is successfully used in high and ultrahigh frequency technology. Rolled fluoroplastic film is used in the manufacture of high-quality cables, wires, capacitors, for insulating coils, grooves of electrical machines. As a structural material, polytetrafluoroethylene is used in the manufacture of various machine parts. Teflon is especially widely used in the manufacture of bearings operating without lubricant, with a limited amount of lubricant and in the presence of a corrosive environment.
Due to chemical inertness, hydrophobicity (contact angle of leakage 108 ± 2°), oleophobicity and fluidity, Teflon is widely used for sealing threaded and flanged joints (FUM tape or Teflon tape).
Due to their quality characteristics, Teflon self-adhesive tapes are very popular and are often used in the textile and food industries, as well as in everyday human activities. These can be: Teflon tape, Teflon tape for a vacuum sealer, Teflon-coated fiberglass, Teflon sealer tape, Teflon self-adhesive tape, etc.
Fluoroplast-4 (Teflon) is an excellent anti-friction material with a coefficient of sliding friction, the lowest known structural material available (even less than that of melting ice). Because of their softness and fluidity, solid PTFE plain bearings are rarely used. In highly loaded units, metal-fluoroplastic bearings-inserts and metal-fluoroplastic support tapes are used. Such a sliding element can withstand tens of kilograms per square millimeter and consists of a metal base on which a Teflon coating is applied.
Teflon is also used as an anti-friction additive (solid lubricant) that improves the sliding properties of base polymers, such as polyether ether ketone (PEEK) or polyphenylene sulfide (PPS), to obtain a "bearing" composition with high strength, wear resistance, creep resistance and good anti-friction properties.
Lubricants with finely dispersed fluoroplast introduced into their composition are known. They are distinguished by the fact that the filler, settling on rubbing metal surfaces, in some cases allows mechanisms to work for some time with a completely failed lubricant system, only due to the anti-friction properties of Teflon.
Teflon is widely used in high-frequency technology, since, unlike polyethylene or polypropylene with similar properties, it has a dielectric constant that changes very little with temperature, a high breakdown voltage, and extremely low dielectric losses. These properties, along with heat resistance, determine its wide application as wire insulation, especially high-voltage, all kinds of electrical parts, in the manufacture of high-quality capacitors, printed circuit boards.
In electronic equipment for special purposes, PTFE-insulated wiring is widely used, which is resistant to aggressive environments and high temperatures – wires of the MGTF, MS and a number of others brands. Wire in Teflon insulation cannot be melted with a soldering iron. The disadvantage of fluoroplastic is its high cold fluidity: if you keep the wire in fluoroplastic insulation under mechanical load (for example, put a furniture leg on it), the wire may become bare after a while.
FUM tape | wikimedia.org
Teflon self-adhesive tape | adobe.com
PTFE Coated Fabric with Self Adhesive Backing | Depositphotos.com
3. The medicine
Due to its biological compatibility with the human body, Teflon is successfully used for the manufacture of implants for cardiovascular and general surgery, dentistry, and ophthalmology. Polytetrafluoroethylene is considered the most suitable material for the production of artificial blood vessels and cardiac pacemakers.
In dentistry, non-resorbable Teflon membranes with or without titanium framework reinforcement are used in guided bone regeneration (GBR) techniques. There is also PTFE suture material.
In 2011, Teflon was first used for repair of damaged nasal septum and walls of the paranasal sinuses instead of titanium meshes. After 12–15 months, the implant completely dissolves and is replaced by the patient's own tissue.
In the production of modern high-tech clothing, membrane materials based on expanded polytetrafluoroethylene are used.
By physical deformation of Teflon, a thin porous film is obtained, which is applied to fabrics and used in tailoring. Membrane materials, depending on the manufacturing features, can have both windproof and water-proof properties, while the normalized pore size of the polytetrafluoroethylene membrane allows the material to effectively pass the evaporation of the human body.
There is a fabric-backed Teflon membrane material that allows air to pass through but does not allow wind to pass through.
Teflon is also used in the manufacture of carpets, umbrellas, raincoats, jackets, balls and many other items.
5. Other products that use Teflon
- heating lamps
- portable heaters (heaters)
- irons plates
- ironing board covers
- stove burners
- electric grills
- popcorn making equipment
- coffee pots
- rolling pins (with anti-stick coating)
- bread baking machines
- trays for skewer or wire rack
- ice cream molds
- teflon coated toilets
- cooker surfaces
- frying pans and pans
- woks (Chinese pots for frying vegetables and meat)
- baking dishes
- hot sandwich press
- waffle makers
- optical cryostats
- razor blades
- internal coatings of tank barrels
- electric rocket engines
- seals of articulated mechanisms (hinges)
- paints and varnishes
How does Teflon affect the human body?
The possible negative impact of polytetrafluoroethylene on human health has been the subject of controversy for many years. The polymer itself is very stable and inert under normal conditions. PTFE does not react with food, water or household chemicals.
When ingested, polytetrafluoroethylene is harmless. The World Health Organization asked the International Cancer Control Organization to conduct an experiment on rats. Experience has shown that when taken with food up to 25% polytetrafluoroethylene, it has no effect. This study was carried out in the 1960s and again in the 1980s on a general population of rats that consumed 25% of their total food intake of PTFE each day.
Research by French experts, published in the journal "60 Millions de Consomateurs" the results of a laboratory study of 13 samples of frying pans, confirm the safety of the non-stick coating. The French magazine reports that as a result of the tests, the complete safety of the pans was proved. All samples successfully passed the test after rubbing the surfaces with abrasive material a thousand times over two cycles.
Teflon is mainly biohazardous in two cases: in production and when the finished polymer is overheated (at temperatures above 200 °C).
When the PTFE is overheated, thermal decomposition occurs with the release of toxic substances.
The main source of biological risks in the production of fluoropolymers is considered to be perfluorooctanoic acid (PFOA, in English – PFOA), known under the name "C8". This compound has been used in the manufacture of Teflon in the US since the 1950s. The first health effects were reported from the 3M and DuPont factories in the 1960s. In the 1980s, scientific groups joined the study of biological effects. In the late 1990s, the US regulatory authorities drew attention to the problem, which resulted in the recognition of the danger of the substance and the regulation of maximum concentrations. Technological processes in the United States have been changed to completely phase out the C8. Large-scale campaigns have been launched to control PFOA concentrations and clarify its effects on human health.
DuPont has received hundreds of millions of dollars in legal claims (which was made into the film Dark Waters, 2019) from employees of the same company and neighboring residents in connection with harm to health and the silence of the dangers of production. For many years, corporate lawyer Robert Bilott, who uncovered the connection between a string of mysterious deaths and a large number of illnesses in a small town, and DuPont, a chemical company, sued the manufacturer over the fact that waters in the Parkersburg area were contaminated with PFOA, the rate of which at that time was not regulated. by law.
In 2006, DuPont, then the only U.S. producer of PFOA, agreed to remove the reagent residue from its facilities by 2015. As of January 2012, DuPont has not used PFOA in its cookware and bakeware, according to official company information.
Independent European studies have shown that non-stick coatings do not contain PFOA in amounts exceeding safe limits. The Chinese Academy of Quality Control, Inspection and Quarantine (GAQSIQ) and the Danish Institute of Technology confirm that no exposure to PFOA used in the manufacture of tableware has been detected.
Thermal decomposition of teflon
The GOST 10007-80 standard normalizes the operating temperature range of Teflon up to +260 °C and directly indicates the danger of toxic gases being released above this temperature. DuPont does not list toxic release characteristics, but does give a melting point according to ASTM D3418 for various types of Teflon from 260 °C to 327°C.
In general, signs of decomposition (pyrolysis) of Teflon are already detected at a temperature of 200 °C. But this process proceeds relatively slowly up to a temperature of 420 °C. However, at temperatures above 380 °C, perfluoroisobutylene appears (an extremely poisonous gas, which is about 10 times more poisonous than phosgene) and other pyrolysis products.
Experiments show that thermal decomposition products when Teflon is heated above 350 °C cause a poisoning picture reminiscent of foundry fever – symptoms are observed that are called "Teflon fever".
For more information about such experiments and the possible danger from overheating of Teflon, see the video at the end of this article.
Hack and predictor Aviator
Since the mass release of toxic substances with Teflon begins at temperatures above 450 °C, cookware with non-stick coatings is considered safe, since such temperatures cannot be reached during normal use. It should be borne in mind that manufacturers consider only heating with water or oil in a pan to be the norm. Water prevents the Teflon from overheating, and its complete evaporation indicates a significant heating of the dishes, which is now not visualized in any way and can become critical. Edible oils decompose at temperatures up to 200 °C with the release of smoke, making it easier to identify overheating. Heating on a dry cookware stove is considered abnormal and in this case the Teflon pyrolysis temperatures are easily achievable. To simplify operation, some models of Teflon cookware are equipped with built-in visual temperature indicators. In general, use Teflon cookware correctly!
Danger of Teflon decomposition products for birds
The special structure of the respiratory system of birds makes them hypersensitive to toxic substances contained in the environment. It has been established that even a minimal amount of perfluorooctanoic acid, getting into the body of a bird with inhaled air, affects its respiratory system, leading to death after a while (from several minutes to tens of hours).
Small birds are more sensitive to toxic substances, they only need a few seconds of inhalation of Teflon fumes and death occurs within the next 24 hours. There are a lot of reports about the death of poultry (for example, parrots) from the fumes of Teflon pans left unattended and overheated above a safe temperature.
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