August 6, 2015
PTFE vs. Elastomer
As the telling of Creation goes, God rested on the seventh day. On the morning of the eighth day, some say the first thing He did was create PTFE! (Actually, it was a gentlemen named Roy Plunkett who created PTFE in 1938 while he was working at DuPont.) Polytetrafluoroethylene (a.k.a. Teflon) is one of the slipperiest solid substances known to man. Being slippery is just one of the great benefits and advantages PTFE has over an elastomeric seal when used in sealing solutions.
There are many different types of sealing solutions on the market today: bearing isolators, mechanical seals, cartridge seals, spring energized seals, rotary lip seals, face seals…the list seems nearly endless. But the types of material used in each of these seals is relatively limited when it comes to the base material. The two most common types of sealing material are either PTFE-based or elastomeric-based. So, what is the difference? Quite a bit, actually!
PTFE was created quite by accident, but the elastomeric materials (HNBR, FKM, Nitriles etc.) were created for specific purposes when it came to sealing solutions. The sealing industry pretty much began when Henry Ford realized that rope packing wasn’t going to work in his automobiles, so he sought out a more robust material, contracting Chicago Rawhide to make leather seals for him. As the industry and the demands of heat in applications grew, natural rubber replaced the leather packing. But demands for more robust solutions continued to rise, and synthetic rubber was created to meet these demands. These synthetic rubber (elastomeric) materials are still in use today. However, applications continued to become more severe, including the need to seal caustic chemicals and withstand extreme heat and higher pressures than ever before.
For basic applications, the elastomeric seal material was and is doing just fine. However, for an application with a pressure higher than 30 psi, or temperatures that exceed 275°F, most elastomeric seals will not last very long at all. Add acids or other caustic chemicals to the application, or even high RPMs, and you will, once again, experience a much shorter life with an elastomeric seal.
So, it was a good thing that God rested well on the seventh day. I really mean, thanks to Roy Plunkett for accidentally creating the material that is used in all the nastiest, hottest, fastest running applications of today: PTFE!
Contact Tritec today and we will create a rotary lip sealing solution for you with a perfectly blended, molded, and sintered PTFE material that will withstand your most extreme application!