What Is It?
PTFE (Teflon) is a member of the fluoroplastic family, which includes chlorotrifluoroethylene, CTFE or CFE, polyvinyl fluoride, PVF, and polyvinylidene fluoride PVF2. PTFE has exceptionally low friction, is water repellant, and extremely stable. It was first commercialized in the late 1940s as Teflon. Non-stick cooking utensils (Tefal = teflon coated aluminum) exploit its chemical inertness, its thermal stability, and its non-wettability – the reason nothing sticks to it. It is expensive as polymers go, but it is used in high-value applications (non-stick pans; GoreTex rain gear; artificial arteries).
PTFE is 2.7 times denser than polyethylene and 12 times more expensive. But it is much more resistant to chemical attack; it can safely be used from −270 to +250 C. It has remarkably low friction; and it has an exceptional ability to resist wetting. All fluoroplastics are white, and to some degree, translucent. They give long-term resistance to attacks of all sorts, including ultraviolet radiation. PTFE itself has a characteristically soft, waxy feel, partly because of the low coefficient of friction. It is an excellent electrical insulator, with low dielectric loss. It can be “foamed” to give a light, micro-porous film that rejects liquid water but allows water vapor to pass – the principle of GoreTex. The mechanical properties of PTFE are not remarkable, but it can be made more abrasive resistant by filling with inert ceramic, and it can be reinforced with glass, nylon, or Kevlar fibers to give a leather-like skin of exceptional toughness, strength, and weather-resistance (exploited in tensile roofs). Bonding PTFE is difficult; thermal or ultrasonic methods are good; epoxy, nitrile-phenolic, and silicone adhesives can be used.
The use of GoreTex derivatives in fabrics is expanding. The pore size in these fabrics can be controlled to reject not merely water, but bacteria, with potential for protective clothing for surgeons, and against certain kinds of biological weapons.
Wire and cable covers; high-quality insulating tape; corrosion resistant lining for pipes and valves; protective coatings; seals and gaskets; low friction bearings and skis; translucent roofing and weather protection for other polymers (e.g.
PTFE is non-flammable and FDA approved. Like all thermoplastics, simple PTFE can be recycled. But in making it into non-stick surfaces, or in transforming it into GoreTex, additives are made which prevent further recycling.
Fluorine is the most reactive of gases, yet combined with carbon to form polytetrafluoroethylene, PTFE, it becomes the most stable of molecules, resistant to practically everything except excessive heat. It has an exceptionally low coefficient of friction against steel, making it attractive for bearings and – in dispersed form – as a lubricant.