Coefficient of Friction (COF) Test

The phenomenon of friction is encountered in all areas of life. Friction is the invisible force that allows or hinders the movement of two surfaces in contact with each other. The coefficient of friction (COF, coefficient of friction) of a packaging film expresses a relative indicator of its friction properties. Controlling this value allows manufacturers to optimize performance and avoid potential problems with the creation, transportation and storage of packages.

For example, in horizontal form fill and seal systems, too much friction on the fill side of the film causes the film to drag or jam as it passes over metal plates. In contrast, in vertical form fill and seal systems, too much friction on the sealant side of the film causes poor film feeding on the metal forming collars, inconsistent pack sizes and squeaking. Also, in both systems, too much friction causes lateral slip, resulting in leaks. Too little friction on the outside causes packages to slide or fall off inclined conveyor belts. Too much friction outside can slow the progress of packages through delivery channels.

Basically, the coefficient of friction (COF) is reported in two values:

• Static (force required to start motion)
• Kinetics (force required to maintain motion)

Kinetic COF is generally used for roll films. Static COF is of greater concern for stacked or palletized elements.

Generally, the coefficient of friction is obtained by adding some lubricant to a film resin during manufacture. The traditional approach to lowering the coefficient of friction is to add a compound that is incompatible with the film resin and is carried to the surface of the film over time. Non-migrating slip agents provide benefits in thermal stability and consistency, but can affect film clarity.

The coefficient of friction can be affected by a number of factors such as the additives used, antistatics, inks, varnishes and adhesives. In advanced laboratories, tests are carried out to determine the coefficient of friction. However, because these tests cannot simulate every element of any packaging process, the coefficient of friction cannot be considered an indicator of system-specific performance. In order to create and optimize an ideal packaging film for a product and its production process, a competent authority must be consulted.

In advanced laboratories, coefficient of friction tests are performed for a wide variety of applications, including a new cardboard coating, a polymer or plastic surface, or corrugated cardboard. These labs have the best coefficient of friction testing equipment for materials, from peel test to shear angle coefficient of friction testers.

In order to determine the static and kinetic friction of films and plastic coatings, the "ASTM D1894-14 Standard test method for the static and kinetic friction coefficients of plastic film and coating" developed by the American Testing and Materials Organization (ASTM) is generally followed. The test method described involves determining the initial and sliding friction coefficients of plastic film and sheet as they slide over themselves or other materials under specified test conditions. When performing these tests, a movable plane and a fixed sled or a fixed plane and a movable sled are used. Both methods yield the same coefficients of friction for a given sample.

In short, the determination of the coefficient of friction is made on a film or coating sample as it slides on itself or another material. The friction coefficients are related to the sliding properties of plastic films, which are of great interest in packaging applications. These methods provide empirical data for control purposes in film production. Usually, test results can be correlated with actual performance.

Our organization has a strong staff that closely follows the developments in the world in the field of science and technology and constantly improves itself. Coefficient of friction (COF) testing services are among the numerous test, measurement, analysis and evaluation studies given to businesses.