Teflon

= = **TEFLON ** Taken by Sarah C **HiSTORY ** Teflon is polytetrafluoroethylene, or PTFE. PTFE was accidentally invented by Roy Plunkett of Kinetic Chemicals in New Jersey in 1938. While Plunkett was attempting to make a new CFC refrigerant, the perfluorethylene  polymerized in its pressurized storage container, with the iron from the inside of the container acting as a catalyst. Kinetic Chemicals patented it in 1941 and registered the Teflon trademark in 1945.
 * = =**PROPERTY**= ||= =**VALUE**= ||
 * = Density ||= 2200 kg/m3 ||
 * = Melting Point ||= 327°C ||
 * = Young's Modulus ||= 0.5 GPa ||
 * = Yield Strength ||= 23 MPa ||
 * = Coeficient of Friction ||= 0.05-0.10 ||
 * = Dielectric Constant ||= ε=2.1,tan(δ)<5(-4) ||
 * = Dielectric Strength ||= 60 MV/m ||

= = **MOLECULAR STRUCTURE** The molecular structure of Teflon is based on a chain of carbon atoms, the same as all polymers. Unlike some other fluoropolymers, in Teflon this chain is completely surrounded by fluorine atoms. The bond between carbon and fluorine is very strong, and the fluorine atoms shield the vulnerable carbon chain. This unusual structure gives Teflon its unique properties. In addition to its extreme slipperiness, it is inert to almost every known chemical.

PTFE can be produced in a number of ways, depending on the particular traits desired for the end product. Many specifics of the process are proprietary secrets of the manufacturers. There are two main methods of producing PTFE. One is suspension polymerization. In this method, the TFE is polymerized in water, resulting in grains of PTFE. The grains can be further processed into pellets which can be molded. In the second method, dispersion plymerization, the resulting PTFE is a milky paste which can be processed into a fine powder. Both the paste and powder are used in coating applications.
 * HOW IT IS MADE **

//Making the TFE//

 * Manufacturers of PTFE begin by synthesizing TFE. The three ingredients of TFE, fluorspar, hydrofluoric acid, and chloroform are combined in a chemical reaction chamber heated to between 1094-1652°F (590-900°C). The resultant gas is then cooled, and distilled to remove any impurities.

//Suspension Polymerization//

 * The reaction chamber is filled with purified water and a reaction agent or initiator, a chemical that will set off the formation of the polymer. The liquid TFE is piped into the reaction chamber. As the TFE meets the initiator, it begins to polymerize. The resulting PTFE forms solid grains that float to the surface of the water. As this is happening, the reaction chamber is mechanically shaken. The chemical reaction inside the chamber gives off heat, so the chamber is cooled by the circulation of cold water or another coolant in a jacket around its outsides. Controls automatically shut off the supply of TFE after a certain weight inside the chamber is reached. The water is drained out of the chamber, leaving a mess of stringy PTFE which looks somewhat like grated coconut.
 * Next, the PTFE is dried and fed into a mill. The mill pulverizes the PTFE with rotating blades, producing a material with the consistency of wheat flour. This fine powder is difficult to mold. It has "poor flow," meaning it cannot be processed easily in automatic equipment. Like unsifted wheat flour, it might have both lumps and air pockets. So manufacturers convert this fine powder into larger granules by a process called agglomeration. This can be done in several ways. One method is to mix the PTFE powder with a solvent such as acetone and tumble it in a rotating drum. The PTFE grains stick together, forming small pellets. The pellets are then dried in an oven.
 * The PTFE pellets can be molded into parts using a variety of techniques. However, PTFE may be sold in bulk already pre-molded into so-called billets, which are solid cylinders of PTFE. The billets may be 5 ft (1.5 m) tall. These can be cut into sheets or smaller blocks, for further molding. To form the billet, PTFE pellets are poured into a cylindrical stainless steel mold. The mold is loaded onto a hydraulic press, which is something like a large cabinet equipped with weighted ram. The ram drops down into the mold and exerts force on the PTFE. After a certain time period, the mold is removed from the press and the PTFE is unmolded. It is allowed to rest, then placed in an oven for a final step called sintering.
 * The molded PTFE is heated in the sintering oven for several hours, until it gradually reaches a temperature of around 680°F (360°C). This is above the melting point of PTFE. The PTFE particles coalesce and the material becomes gel-like. Then the PTFE is gradually cooled. The finished billet can be shipped to customers, who will slice or shave it into smaller pieces, for further processing.

//Dispersion polymerization//

 * Polymerization of PTFE by the dispersion method leads to either fine powder or a paste-like substance, which is more useful for coatings and finishes. TFE is introduced into a water-filled reactor along with the initiating chemical. Instead of being vigorously shaken, as in the suspension process, the reaction chamber is only agitated gently. The PTFE forms into tiny beads. Some of the water is removed, by filtering or by adding chemicals which cause the PTFE beads to settle. The result is a milky substance called PTFE dispersion. It can be used as a liquid, especially in applications like fabric finishes. Or it may be dried into a fine powder used to coat metal.

**HOW TEFLON AFFECTS US AND THE ENVIRONMENT** Teflon has many uses to the society. These are some of it. These uses of teflon basically make life easier for people. For the environment, there are also several advantages. One of these is the use of Teflon as a fabric protector which would help repel and release stains. Because of this, it can reduce the need for laundering and dry cleaning. That means that we'll be doing less washing, using lower wash and dry temperatures, and have less wear and tear on fabrics. By helping us reduce our water and energy usage and increasing the fabric's usable life, we have less impact on the planet.  ANOTHER INTERESTING FACT...
 * Coating for non-stick pans and other cookware materials making it easier for cooking.
 * Fabric protector for apparel and outerware, to bedding and upholstery to minimize the work done to clean the mess made on it.
 * Additive for paints and varnishes to make the newly painted or varnished furniture shiny and less susceptible to dust and dirt.
 * Eyeglass lens coating to make the eyglasses easier to clean and easier to see through it.
 * Hair care products coating to make personal hair care easier and faster
 * Coating for men's shavers
 * Protective coating for vehicle parts
 * Coating for marine vessels to make easy-sailing boats
 * Used in pyrotechnic compositions as oxidizers together with powdered metals such as aluminum and meagnesium. Upon ignition, these mixtures form carbonaceous soot and the corresponding metal fluoride, and release large amounts of heat. Hence they are used as infrared decoy flare and igniters for solid-fuel rocket propellants.
 * PTFE is also used in body piercings, such as a subclavicle piercing, due to its flexibility and biocompatibility.
 * In optical radiometry, sheets made from PTFE are used as measuring heads in spectroradiometers and broadband radiometers (e.g., illuminance meters and UV radiometers) due to its capability to diffuse a transmitting light nearly perfectly. Moreover, optical properties of PTFE stay constant over a wide range of wavelengths, from UV up to near infrared. In this region, the relation of its regular transmittance to diffuse transmittance is negligibly small, so light transmitted through a diffuser (PTFE sheet) radiates like Lambert's cosine law. Thus, PTFE enables cosinusoidal angular response for a detector measuring the power of optical radiation at a surface, e.g., in solar irradiance measurements.
 * PTFE is also used to coat certain types of hardened, armor-piercing bullets, so as to prevent the increased wear on the firearm's rifling that would result from the harder projectile.
 * PTFE's low frictional properties have also been used as 'feet' for computer mice such as the Logitech G5, Logitech G7, and Logitech G9 series and most Razer gaming mice (e.g., the Deathadder, Lachesis, etc.). The low friction provided by PTFE allows the mice to glide across surfaces more smoothly and with less effort.
 * PTFE's high corrosion resistance makes it ideal for laboratory environments as containers, as magnetic stirrer coatings, and as tubing for highly corrosive chemicals such as hydrofluoric acid, which will dissolve glass containers.
 * PTFE is also widely used as a thread seall tape in plumbing applications, largely replacing paste thread dope.
 * PTFE grafts can be used to bypass stenotic arteries in peripheral vascular disease, if a suitable autologous vein graft is not available.
 * PTFE can be used to prevent insects climbing up surfaces painted with the material. PTFE is so slippery that insects cannot get a grip and tend to fall off. For example, PTFE is used to prevent ants climbing out of formicaria.

IS TEFLON DANGEROUS TO HUMANS?

Though there were some reports of teflon being hazardous, especially as a non-stick coating in cookware, DuPont, the company where teflon is one of its major products, had made some responses to the public's insistent interrogations. According to them, over forty years of consumer use, along with laboratory testing and published peer-reviewed research, has affirmed that cookware made with Teflon non-stick coatings is safe for both consumer and commercial use at normal cooking temperatures. They also added that the U.S. Food and Drug Administration (FDA) concluded that fluoropolymer non-stick coatings for cookware are acceptable for conventional kitchen use and on its web site, the U.S. Environmental Protection Agency (EPA) has stated that it "does not believe there is any reason for consumers to stop using any consumer or industrial related [non-stick coated] products." In 2003, The U.S. Consumer Product Safety Commission rejected a petition to require a warning label for non-stick coatings. They have put up a recommended maximum use temperature for cookware with Teflon non-stick coating.

°F ||= Cookware Temperature, °C ||= Cooking Use ||  The fumes that are released by overheated polymer can produce symptoms referred to as "polymer fume fever" - flu-like symptoms that are relatively quickly reversed in humans. Over the past 40 years, there have been only a few reported accounts of polymer fume fever as a result of severely overheating non-stick cookware. So there is no real reason for the cookware coated with Teflon to be no longer used as long as it is used properly and according to the manufacturer's recommendations. In rare instances, a person may accidentally ingest a flake of non-stick coating from an aged pan. The coating flake is non-toxic and would pass through the body without being absorbed. Based on the inert characteristics of the coating, data indicate that there are no health effects from the incidental ingestion of pieces of non-stick coating  SUMMARY
 * = Cookware Temperature,
 * = 212 ||= 100 ||= Boiling point for water ||
 * = 325-400 ||= 163-204 ||= Normal range for baking cookies, cakes etc. ||
 * = 400-470 ||= 204-243 ||= Normal range for pan-frying meat ||
 * = 450 ||= 232 ||= Roasting poultry or vegetables ||
 * = 500-550 ||= 260-288 ||= Broiling ||

media type="youtube" key="-e72B9V2R8s" height="385" width="480" Here is a video summary of Teflon. enjoy!

Sources:

"Cookware coated with teflon non-stick". May 27, 2010  "DuPont Teflon: Safety of non-sticks: Cookware Safety". May, 28, 2010  "Environmental Advantages: Teflon Fabric Protector". May 30, 2010  "Home and Garden Products with Teflon". May 25, 2010  "Non-stick Bakeware". May 26, 2010 <http://www2.dupont.com/Teflon/en_US/products/bakeware.html> "Paint Products: Teflon non-stick coatings". May, 25, 2010 <http://www2.dupont.com/Teflon/en_US/products/paint.html> "Polytetrafluoroethylene". May 24, 2010 <http://en.wikipedia.org/wiki/Teflon> "Teflon". May 30, 2010 <http://www.youtube.com/watch?v=-e72B9V2R8s> "Teflon: How Products are Made". May 25, 2010 <http://www.enotes.com/how-products-encyclopedia/teflon> "Teflon @ 3Dchem.com". May 24, 2010 <http://www.3dchem.com/molecules.asp?ID=200> "Teflon Fabric Protector". May 26, 2010 <http://www2.dupont.com/Teflon_Fabric_Protector/en_US/index.html>