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The Significance of COF Test of Flexible Packaging Film and Test Method

Oct 10,2020

Source: Link Testing Instruments Co., Ltd

Coefficient of friction (COF) is one main physical index of plastic film or sheeting, which describes the ratio of force of friction when sliding over itself or other substances at specified conditions.

The flexible packaging film should be of proper coefficient of friction otherwise negative effects may be caused during the operation. To be specific, if the coefficient of friction is too high, it will require a higher pulling force to unwind the roll of the plastic film. As a result, the production efficiency will be compromised and even worse the film may be deformed after being stretched excessively. On the other hand, of the coefficient of friction is too low, the films may slip or fall off from the roll, which may cause suspension of production and unnecessary production cost. Therefore it is quite important to the manufacturers and users of flexible packaging film to control its coefficient of friction and select suitable packaging materials through COF tests.

There are various factors that may influence the coefficient of friction of flexible packaging film. They are additives, lubricants, surface texture and temperature, etc. The manufacturers can adjust the coefficient of friction of films by modifying those factors mentioned above according to the COF test results.

Currently the COF of flexible packaging film can be tested according to ASTM D1894: Standard Test Method for Static and Kinetic Coefficients of Plastic Film and Sheeting. The simplified testing procedures will be provided in the following for your reference.

Link Testing LTCOF-05A Coefficient of Friction Tester is used as the testing instrument. The test can be performed according to the following procedures.

  • Cut specimens. Do not touch the test area of the specimens when preparing and mounting the specimens. The specimen surface should be flat and free of creases or folds.
  • Tape the specimen to the plane with the machine direction of the specimen. Smooth the specimen to eliminate wrinkles if necessary, taking care not t alter the specimen surface through figure oils, etc.
  • Take the edges of the square film specimen to the back of the sled, using adhesive tape and pulling the specimen tight to eliminate wrinkles without stretching it.
  • Attach the specimen-covered sled through its eye screw to the nylon filament.
  • Start the driving mechanism. The test will be performed automatically. The test results will be given by the instrument after tests.

For more details about LTCOF-05A Coefficient of Friction Tester, please visit

About Link Testing Instruments Co., Ltd:

Link Testing Instruments Co., Ltd is one leading supplier of packaging testing instruments, which is headquartered in Jinan, China.

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