The coefficient of friction, or COF, is one of the first properties considered when determining the type of polyurethane roller needed for a particular application. Polyurethane is an extremely versatile material that can be manufactured into many different shapes, sizes, and colors, as well as be developed to varying magnitudes of hardness and degree of friction. And depending on the application, the coefficient of friction may be very important, as it is in the case of polyurethane rollers.
Polyurethane rollers are typically made to a higher coefficient of friction. Rollers, by nature, have to move something else along, and a common use of rollers is on powered or motorized conveyor systems to move the belt along smoothly regardless of the load applied to it. A lower coefficient of friction would mean that the conveyor belt would simply remain in place. On the other hand, rollers on some manual conveyor systems are made to a lower coefficient of friction, as the rollers rely on manual force to move the load along.
There are two types of friction that must be considered when deciding on a particular type of polyurethane roller for its intended application. The first is the static coefficient of friction (SCOF), which is a measure of the friction between the roller and the belt (or other equipment) while both are at a state of rest. An engineer can calculate the static coefficient of friction easily enough using the standard formula in order to get a good idea of the type of polyurethane roller needed for the final application.
The second type of friction to be considered is the dynamic (or kinetic) coefficient of friction (DCOF). This is best measured with laboratory equipment such as tribometers or other friction testers for an accurate measurement to be obtained, as it is measured while the equipment is in motion. Manufacturers and/or third-party labs would be able to accurately measure the dynamic coefficient of friction and further determine which type of roller would be best for the intended application. There are many types of polyurethane rollers, and determining the amount of friction for a particular application or piece of equipment will help narrow the field.