TEFLON® has almost become a generic name for PTFE. However, you must be careful when using the trade name TEFLON®. It is registered by E.I. du Pont de Nemours & Company (Inc.) and actually refers to a family of FLUOROPOLYMERS which includes PFA (Perfluoroalkoxy), FEP (Fluoroinated Ethylene Propylene) and PTFE (Polytetrafluoroethylene). In this section, we will first discuss PTFE then the remaining members of this family as well as other FLUOROPOLYMERS.
As you can see from the volume of specifications above, PTFE is an important, highly specialized and well-studied product. It is also quite expensive as the raw resin is costly, production of basic shapes is relatively labour intensive requiring a high capital investment and the cost of maintaining quality to meet such a range of specifications is high. But PTFE can function the way no other material is able. PTFE is an engineering polymer which maintains its useful mechanical properties over a very wide temperature range from -450°F to 550°F; it has an extremely low coefficient of friction; almost nothing sticks to PTFE; its chemical resistance is outstanding with only molten alkali metals and certain halogens, under special conditions, attacking the material; there are no known solvents for PTFE; electrical insulation and loss properties are remarkable as no other solid material maintains its dielectric constant over such a wide range of temperature and frequency; parts of PTFE are virtually unaffected by weather, i.e. extremes of heat and cold and ultra-violet light; moisture absorption is zero; PTFE will not burn under any conditions, it exhibits almost zero slip-stick; PTFE is unaffected by large doses of radiation. The ability of PTFE to accept a wide variety and loading of fillers and reinforcing materials results in increasing its low tensile strength by a factor of 2 to 3; increasing its poor wear resistance by as much as 500 times; increasing initial deformation under load by approximately 25%; increasing creep resistance by two fold; increasing hardness by about 10%; increasing thermal dimensional stability by a factor of 2.
Claremont Polymer Shapes can provide a wealth of technical and practical support for you in the design and production of quality PTFE parts. With the aid of mills producing rods, sheets, tubes, tapes, etc. as well we the resin producers, we can offer back up second to none. Should you require prototype or production quantities of PTFE parts and do not wish to manufacture such parts yourself, call on us; our facilities, and those of some outstanding craftsmen working with us, are at your disposal.
Effects of the most common reinforcing materials for PTFE are as follows:
Milled, short glass fiber is common to 25% by weight, providing uniform increase to tensile, impact and dimensional stability properties. Often used with graphite or molybdenum disulphide to reduce wear on mating parts; it has little effect on electrical properties; resists acids and oxidizers but is attacked by alkalis.
High purity coke powder in amounts of 25% to 35% by weight is used to increase wear resistance especially for heavy loads. It has little effect on chemical resistance but electrical properties can be inhibited.
A crystalline form of carbon, it is used alone or in combination with amorphous carbon or glass fiber often at 15% by weight. Compounds often have soft surfaces, which reduce wear on mating hard metals while improving friction and wear properties with little effect on chemical resistance but impairing electrical properties.
Powder in amounts from 40% to 60% by weight is used to increase machinability, creep and wear resistance, thermal conductivity and reduce friction and wear of soft metal parts. Chemical resistance to acids and bases plus electrical insulation are poor.
Provides many of the enhancements of GLASS FIBER but without abrasiveness, amounts to 15% yield a material with excellent wear resistance. Electrical properties and chemical resistance are lower; water absorption and flammability increasing slightly.
Moulded PTFE shapes are produced from Virgen Grade PTFE by pouring resin into an appropriate form. Pressure is exerted to force the resin into the shape. This preform is then heated to sintering temperature at which point the resin coalesces to a solid mass yielding the sheets, rods and tubes with which you are familiar. SKIVING is a process in which large diameter; heavy wall stock is peeled into thin sheeting. The stock is turned while a cutting blade is forced into the outer surface along its length in the same way that veneer is peeled from a wood log.
Virgin Grade PTFE is 100% pure material directly from the resin producer and has never been processed into a shape. Virgin PTFE has the highest physical and electrical insulation properties and the whitest colour compared to Mechanical Grade. In compounded formulations, Virgin PTFE is used almost exclusively. Mechanical PTFE contains some or all reground polymer that has been previously processed. Mechanical PTFE has similar chemical and tribiological properties, inferior physical properties, and greatly inferior electrical insulation properties and is not recommended for electrical insulation. Mechanical PTFE may not be as white, may contain dark spots and is cheaper.