Effect of Coefficient of Friction (COF) in Packaging Industry

Labthink MXD-02 Coefficient of Friction Tester

Working in virtually nearly every facet of our lives, friction is the invisible force that allows, or hinders the movement of two surfaces that are in contact with one another. Coefficient of Friction is the ratio of the force that maintains contact between an object and a surface and the frictional force that resists the motion of the object.

A packaging film’s “coefficient of friction” (COF) provides a relative indication of frictional characteristics. Controlling COF gives processors the ability to optimize performance and avoid problems in forming, transporting, and storing of packages.

 In HFFS (horizontal form fill and seal) systems, too much friction of the sealant side of the film can lead to film dragging or jamming as it passes over metal plates.

 In VFFS (vertical form fill and seal) systems, too much friction of the sealant side of the film can cause poor film feeding over metal forming collars, inconsistent package sizes, and squealing.

 In either system, too much friction can result in lateral slipping that leads to poor seals (leakers).

 Too little friction on the outside can cause packages to slip or fall-off-of inclined conveyor belts.

 Too much friction on the outside can slow packages’ progress down delivery chutes.

 Too little friction on the outside can result in packages sliding off of stacks or pallets.

You can see that various applications require different fictional properties. Therefore, Coefficient of Friction (COF) measurement is very important and used for process control to ensure the consistent production of a kind of packaging (films etc).

Test Principles

As mentioned above, COF is a simple ratio equal to the force required to slide on surface over another, divided by the force perpendicular to the contacting surfaces.

COF = Force to cause sliding of film surfaces

sled weight

It’s a unitless coefficient. We can see that coefficient of friction should be between 0 and 1. Higher values indicate more resistance to sliding. There are two kinds of coefficient of friction – static and kinetic COF. Static COF is a higher value and is related to the force to get movement started.

International Standards

ISO 8295 -- Plastics -- Film and sheeting -- Determination of the coefficients of friction

ASTM D1894 -- Standard Test Method for Static and Kinetic Coefficients of Friction of Plastic Film and Sheeting

Coefficient of Friction Tester

Labthink Coefficient of Friction Tester MXD-02 provides a digital display of static and kinetic Coefficient of Friction (COF). It is designed according to ISO 8295 & ASTM D1894. It has a high accuracy test result (0.5% of reading value).