Fluorocarbons are among the more expensive plastics, but design engineers have found them to be adaptable to a variety of requirements. They offer a unique combination of heat resistance and low friction together with good chemical and electrical properties. Fluorocarbons can be used over a wide temperature range, from as low as 110 o F to as high as 500 0 F.
The most prominent fluorocarbon is TFE. It is inert to almost all chemicals, cannot be dissolved and exhibits no moisture absorption. Typical applications would include chemical mixing rod bearings, gaskets and diaphragms in meters, chemical pump liners, bushings and bearings, containers for corrosives, valve seats, balls, thrust washers and seal rings.
In addition TFE has good electrical properties, including high arc resistance. This gives it applications in high frequency insulation and stand-off insulators, bus bars in chemical electro plating, coaxial cable connectors, terminal insulators, transformers, capacitors, relays and electrical push rods.
The extreme "slipperiness" of fluorocarbon materials gives them many applications where low friction is required. In food industries, they can be used to cover work surfaces to avoid having sticky materials coat the parts. Laboratories use them to cover surfaces where tacky or corrosive compounds will be used. The anti-friction property of fluorocarbons used in moving parts may actually improve with time. A thin layer of material may be deposited on the contacting surface so that you have the condition of fluorocarbon rubbing against itself.
Some fluorocarbons may be filled or alloyed to enhance certain properties. The most common filler is glass, which can greatly increase certain mechanical properties such as modular and strength. The desirable fluorocarbon properties of chemical and heat resistance are generally retained, but the price is, of course, greater for a filled system. Filled fluorocarbons have been used in journal bearings, piston rings and bushings.
PTFE or TFE - polytetrafluoroethylene is a very dense material having a density of 2.13-2.19 grams/cc. PTFE is well known for its chemical resistance. It is insoluble in all organics with the exception of a few exotics. Electrical properties are excellent. Impact strength is high, but its resistance to wear, tensile strength and creep resistance are low in comparison to other engineering materials. Mechanical properties can be improved by adding fillers such as glass fibers, bronze, carbon and graphite. PTFE has an extremely low coefficient of friction. Very few materials will stick to it. It has useful properties from cryogenic temperatures up to 260 0 C (550 0 F). PTFE is produced as TEFLON® by duPont, as HALON® by Allied Chemical Corp., and as FLUON® by I.C.I. While most of the fluorocarbons can be processed by conventional methods, PTFE must be processed by the press and sinter method, or by ram extrusion. Applications for PTFE are many and varied. Chemical plants use PTFE in process equipment. Electronics utilize the excellent electrical properties. Use you imagination to match the properties with applications. Sheets, rods, tubes and tape and available shapes as standard items. Other shapes can be produced.
FEP - fluorinated ethylene propylene has all the desirable properties of PTFE but with a service temperature of 200 0 C (392 0 F). FEP can be extruded by conventional methods into rods or tubes, and special shapes. It is, like PTFE, a soft material with lower tensile strength, wear resistance and creep resistance. It is chemically inert and insoluable in all but a few exotic solvents. FEP is manufactured by duPont and sold under the trade name TEFLON®. Applications include electronic items such as wire covering and spaghetti tubing, linings for pipes in the chemical industry, aircraft wiring and glazing for solar energy collectors. Availabilities include film, sheet, rod and tubing.
PVDF - poly-vinylidene fluoride is a high molecular weight polymer. PVDF exhibits greater strength and wear and creep resistance than PTFE and FEP. It has good weathering properties and resists most chemicals. It has a high dielectric constant and a high loss factor. Temperature range is - 100 0 to 150 0 C. Major markets are in electrical insulation and chemical processing. It is marketed under the trade name of KYNAR® by Pennwalt Co., and is available in sheets, rods, tubes, pipe, valves and fittings.
PFA - perfluoroalkoxy is a melt processible fluoroplastic. Properties are similar to PTFE and FEP, although PFA has slightly better mechanical properties than FEP above 150 0 C. It is a duPont product sold under the TEFLON® trade name. Applications include liners for valves, pumps, pipe and fittings, heat shrinkable tubing for electronics, roll covers and electric wire insulation. PFA is optically clear with a refractive index of 1.3.
PCTFE - polychlorotrifluoroethylene is resistant to most reactive chemicals. However, a few solvents dissolve PCTFE at temperatures above 100 0 C. Others will cause swelling. It has outstanding barrier properties to gases, especially water vapour. Electrical properties are excellent. It is used in chemical process equipment, electrical applications and cryogenic situations. The product is produced by the 3M Co., as KEL-F® and as ACLAR® film by Allied Chemical Corp. KEL-F® is available in rods and slabs.
ECTFE - ethylene-chlorotrifluoroethylene has greater strength, creep resistance and wear resistance than PTFE, FEP and PFA. Mechanical properties are similar to Nylon 6. It is resistant to most corrosive chemicals and organic solvents. UL rates ECTFE as 94V-0 in thickness as low as .007". Temperature ranges from cryogenic to 180 0 C and for short periods to 200 0 C. ECTFE is sold under the trade name of HALAR® . Applications are in the electrical field, valve parts, watch parts, lab tubing and containers for corrosive chemicals.
ETFE - ethylene-tetrafluoroethylene has impact resistance, strength, chemical resistance, electrical properties and weather resistance which nearly approach those of PTFE and FEP. It is a duPont product marketed as TEFZEL®. It can be purchased in film, rod and tubing. It is used for its good electrical properties and in valves and other chemical process equipment.
PVF - polyvinyl fluoride is a highly crystalline plastic produced by duPont as a film under the trade name of TEDLAR®. It has outstanding weathering properties. It has good abrasion resistance and resistance to staining. It is often laminated to other materials to make use of its superior properties. It is also used by itself as a glazing material for solar collectors.
For more information, visit Allplastics .