Coefficient of Friction – Static, Kinetic Horizontal Plane

Coefficient of Friction (COF) is a measure of the force required to overcome the friction between two surfaces. Static COF is a measure of the force required to start movement, while Kinetic COF is a measure of the force required to keep the surfaces in motion.  We measure both of these properties with a horizontal plane COF tester, following TAPPI Test Method T549.  A 3 by 12 inch sample, test side up, is attached to the base of the tester.  A 2.5 by 2.5 in sample, test side down, is placed under a 200-gram sled which is then placed on top of the first sample.  The samples are usually tested in the machine direction, but can also be tested in the cross direction if desired.  At the completion of the test, both static and kinetic coefficients are displayed on the instrument.