What is the COF Test (Coefficient of Friction)? Methods and Standards for Measuring Friction Coefficient

The COF (Coefficient of Friction) test measures the friction resistance between two surfaces. It is used to determine the static and kinetic friction coefficients of materials using the horizontal plane method.

  • Static friction coefficient: The force required to initiate movement.

  • Kinetic friction coefficient: The force required to maintain movement.

The test is widely applied in industries such as packaging, paper, plastics, textiles, and automotive.

Purpose of the COF Test

The purpose of the COF test is to determine the surface friction resistance of various materials.
The test helps in:

  • Evaluating surface performance

  • Ensuring product usability

  • Maintaining quality control

  • Supporting research and development processes

COF Test Methods

Horizontal Plane Method

The horizontal plane method is used to determine both static and kinetic friction coefficients.

  • The sample is fixed on a flat surface.

  • A sled with a specific weight is pulled over the material.

  • The force needed to initiate and maintain movement is measured separately.

This method is reliable and widely accepted in international testing standards.

Applicable Standards

COF testing is performed according to the following international standards:

  • ISO 15359 – COF measurement for paper and board

  • ISO 8295 – Determination of friction for plastic films and sheets

  • ASTM D1894 – COF testing for plastic materials

  • ASTM D2534 – Friction tests for paper and paperboard

  • ASTM D3330 – Friction and peel tests for adhesive tapes

  • TS EN 1724 – European standard for surface friction testing

  • TS ISO 15359 – Turkish standard equivalent of ISO 15359

Evaluation of Test Results

COF values are compared with required quality limits.

  • High COF: Indicates high friction and difficult sliding.

  • Low COF: Indicates high slipperiness and possible control issues.

Factors that may cause incorrect results:

  • Contamination on the material surface

  • Temperature and humidity variations

  • Calibration issues in the test device

Test reports must include test conditions, device information, sample details, and measured results.

Industries Using COF Testing

  • Packaging

  • Plastics and polymers

  • Textiles and leather

  • Printing and paper

  • Automotive

FAQ (Frequently Asked Questions)

1. Which materials can be tested with COF?
Plastic films, paper, textiles, metal surfaces, adhesive tapes, and many other materials.

2. What is the difference between static and kinetic friction?
Static friction refers to the force needed to start movement; kinetic friction refers to the force needed to maintain movement.

3. Why is the horizontal plane method preferred?
Because it is simple, repeatable, and aligned with international standards.

4. How do COF test results affect product design?
Friction levels determine usability, safety, and functional performance during product development.

5. What does a non-compliant COF value indicate?
It indicates that the material does not meet required performance or quality standards.