Fluorine compounds Teflon

Teflon PFA [FLUORINE COMPOUNDS, ORGANIC - TETHAFLUOROETHYLENE-PERFLUOROVINYLETHERCOPOLYPffiRS] (Vol 11) -organic mat ls in carbon dioxide [SUPERCRITICAL FLUIDS] (Vol 23)... 

These ethers readily copolymerize with tetrafluoroethylene and other fluoroalkenes to commercially significant plastics, elastomers, and ion-exchange resins such as Teflon PFA, Kalrez, andNafton (see Fluorine compounds organic-tethafluoroethylene-perfluorovinylETHERcopolya rs EuASTOPffiRS, SYNTHETIC-FLUOROCARBONELASTOTffiRS lONIC POLYTffiRS). 

Stannous fluoride, a compound of tin and fluorine, is much less dangerous. It is added to drinking water and toothpaste to strengthen the enamel in the teeth of the user. Another compound of fluorine is teflon, a plastic made of carbon and fluorine, which is used in kitchenware. The fluorine-containing compound freon is used in air-conditioners and refrigerators, and is harmless. 

Fluorine compounds from fluorite (fluorspar, CaF2) are used in water treatment (to suppress dental caries) and to make fluoropolymers (such as Teflon), lubricants, and refrigerants. Molten cryolite (Na3AlF6) is essential as a solvent for Al203 in the electrolytic production of aluminum metal, while the isotopic enrichment of uranium for nuclear power reactors is usually achieved by diffusion or gas centrifugation of volatile UF6. 

Chemical Hazards. Chemical manufacturers and employees contend with various hazards inherent in production of even commonplace materials. For example, some catalysts used in the manufacture of polyethylene (see Olefin polymers) ignite when exposed to air or explode if allowed to become too warm the basic ingredient in fluorocarbon polymers, eg, Teflon (see Fluorine compounds, organic), can become violendy self-reactive if overheated or contaminated with caustic substances (45,46) one of the raw materials for the manufacture of acrylic fibers (see Fibers, acrylic) is the highly toxic hydrogen cyanide (see Cyanides). 

Many fluorides are corrosive to glass and some metals Even the very corrosive anhydrous fluorides, however, can be handled at room temperature in steel, stainless steel, copper, and Teflon equipment For reactions at higher temperature, nickel and Monel metal are indispensable More data on corrosion of materials are given in pages 22 and 23 of Chemistry of Organic Fluorine Compounds, published in 1976... 

One of the best-known thermal reactions of fluorine compounds is the pyrolysis of chlorodifluoromethane to tetrafluoroethylene as used in the production of Teflon polymer. This reaction was described by Park et in 1947, and Nor-ton" in 1957 reported an activation energy of 49 kcal.mole for the decomposition over silica at 425-525 °C. More recently, Gozzo and Patrick have made a kinetic study of the process using a helium flow system at 670-750 °C with a surface conditioned platinum tubular reactor. HCl is found to retard the raction and the following mechanism has been proposed... 

Small atom with a big ego was the title of the ACS Symposium in San Francisco in 2000, where a number of current scientific and industrial aspects of fluorine-related chemistry were discussed. This small atom has been providing mankind with a lot of benefits, in the form of special products such as Teflon , freon, fluoro-liquid crystals, pharmaceutical and agrochemical compounds, and so on, all of which have their own unique properties created by the characteristic nature of fluorine. Nowadays, organic fluorine compounds have attracted a great deal of interest from the scientists involved in many fields of science and technology. 

Hydrogen Fluoride.31 The acid HF is made by the action of concentrated H2S04 on CaF2 and is the principal source of fluorine compounds (Chapter 16). It is commercially available in steel cylinders, with purity approximately 99.5% it can be purified further by distillation. Although liquid HF attacks glass rapidly it can be handled conveniently in apparatus constructed either of copper or Monel metal or of materials such as polytetrafluoroethylene (Teflon or PTFE), Kel-F (a chlorofluoro polymer), etc. 

Fluorine is used to prepare fluorocarbons— very stable carbon—fluorine compounds used as refrigerants, lubricants, and plastics. Teflon ( FIGURE 22.9) is a polymeric fluorocarbon noted for its high thermal stability and lack of chemical reactivity. 

Uranium hexafluoride is a very reactive and corrosive compound, almost as reactive as fluorine itself. For building the separation equipment. Teflon and other fluorine compounds were utiHzed. 

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