PTFE has the lowest coefficient of friction of any polymer known to mankind. However, once weve added the fillers and additives needed to improve its mechanical properties, it may not have such low friction.
Consider this: virgin PTFE has a coefficient of dynamic friction on the order of 0.04 to 0.06, but adding carbon fiber raises it up to 0.18 and glass can raise it up to 0.5 (yes, about 10x more friction). Fortunately, there are fillers and additives that can improve the coefficient of friction, and we’re going to take a look at some of the more common ones.
One additive that works wonders for bring the coefficient of friction down is Molybdenum disulfide, sometimes referred to in the industry as Moly. When added to PTFE with 15% glass fiber, the coefficient of friction goes from 0.5 to 0.15, which is much closer to virgin PTFE. When added to PTFE, Moly is typically combined with bronze or glass to reduce friction and improve wear characteristics.