Friction

Friction is a complex subject and can be divided into sub-categories that include running friction, breakout friction, wear, lubrication, and more.  The full edition of the Parker O-Ring Handbook contains many details addressing each of these topics, as well as in depth calculations for estimating frictional properties.  

There a many design characteristics that influence frictional forces, including O-ring cross section, percent of compression, hardness, speed, and more.  A full list is shown below:

* Refer to rotary seals.
# A minor factor and should be ignored in design work other than for ultra high speeds.

Parker has a number of friction reducing treatments, such as PTFE and ParkerSlick coating which can be very beneficial at reducing installation or break out friction.  Additionally, there area number of specialty compounds which include ingredients such as molybdenum disulfide, powdered PTFE, or proprietary wax.  During O-ring service, these ingredients migrate to the surface with the benefit of reducing running friction.  Some popular internally lubed compounds include: