COF-01 Coefficient of Friction Tester
Background
Coefficient of friction is the amount of friction existing between two surfaces. A low value of coefficient of friction means less force is required for sliding to occur. A higher value means more force is required. COF will be different depending on the materials that are interacting with each other. Packaging film COF refers to the level of 'slip' that the packaging material has when interacting with different parts of packaging machine or materials. Controlling COF is importance in optimizing performance and avoiding problems in forming, transporting, and storing of packages. COF can be affected by several factors including antiblock additives, corona treatment, antistats, inks, varnishes, adhesives.
Application
Coefficient of Friction Tester COF-01 is for the measurement of static and kinetic coefficients of friction of plastic films, sheets, rubber, paper, paper board, woven and non-woven, fabrics, metalplastic composite belts for communication cables, convey belts, wood, coatings, brake pads, windshield wipers, shoe materials and tires. By modification, it could be used for many other types of materials and test standards.
Standards ASTM D1894, ISO 8295, TAPPI T816, GB 10006 Formula:
COF is determined by dividing the force needed to move one surface across another by the force perpendicular to the surfaces. Its formula is μ = f÷N. Where μ is the coefficient of friction, f is the force of friction, and N is the normal force. It has two kinds: Static and Kinetic. Static COF µs is a measure of the force required to begin movement. In the packaging industry, static coefficient of friction is generally used to measure the friction between bags when they are stacked, cartoned or palletized (plastic on plastic). Kinetic COF µd is a measure of the force required to maintain movement. In the packaging industry, kinetic coefficient of friction is generally used for rolls of plastic films processed on packaging machines (plastic on metal).
In the laboratory tests, COF equals to: Force to cause sliding of film surfaces (gf) /sled weight (gf) Then a unitless number is obtained and this number is COF.
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