Coefficient of Friction of Paper

ISO 15359, TAPPI T549

Understanding the Coefficient of Friction of Plastic Film

In the packaging, printing, and paperboard industries, the coefficient of friction of paper plays a pivotal role in quality control and material handling. This property determines how paper interacts with other surfaces during processing, conveying, stacking, or folding. From smooth feeding in printers to secure packaging during transportation, knowing the coefficient of friction ensures operational efficiency and product safety.

The coefficient of friction (COF) quantifies the resistance between two surfaces in contact—typically calculated using the formula:
μ = f ÷ N
where μ is the coefficient of friction, f is the frictional force, and N is the normal force. For paper and board materials, both static COF (μs) and kinetic COF (μd) are critical.

Coefficient of Friction Test Methods for Paper and Board

To evaluate the coefficient of friction of paper, several methods are available. Among the most widely adopted are the horizontal plane method, as defined by ISO 15359, and the incline plane method referenced in other standards like TAPPI T815. These tests help manufacturers ensure consistent material behavior across production batches.

Horizontal Plane Method (ISO 15359)

The horizontal plane method, outlined in ISO 15359, is one of the most accurate techniques for determining the paper board COF test. It involves placing a sled of known weight on a test specimen and pulling it at a constant speed over a horizontal surface made of the same material. This test measures:

Static COF (μs): The force required to start the sled’s movement.
Kinetic COF (μd): The force required to maintain a constant motion of the sled.

This method is highly suitable for smooth and uniform paper surfaces, and it’s a standard across packaging applications where reliability and repeatability are essential.

Key Parameters (ISO 15359-based):

Sled weight: 200 ± 1 g
Test speed: 100 mm/min
Specimen dimensions: Consistent across tests to ensure comparability
Ambient conditions: Controlled temperature and humidity

Why Coefficient of Friction Matters in Paper Applications

The coefficient of friction test is essential in determining how paper sheets interact in real-world use. Consider these scenarios:

Printing

Paper with too low a COF may slip and misfeed.

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Folding and gluing

High COF may cause jams in automated lines.

Stacking and packaging

COF values directly impact load stability during shipping.

Manufacturers of packaging materials, corrugated boxes, or coated paper must regularly test for COF to meet both functional and safety requirements.

Recommended Instruments for Paper Slip Coefficient Testing

For accurate and reliable testing, specialized instruments like the COF-01 Coefficient of Friction Tester by Cell Instruments are highly recommended. It is designed with:

PLC control and HMI touch screen, offering precise and user-friendly operation
Dual-mode testing, capable of measuring both static and kinetic COFs
Real-time curves and digital data recording, enhancing traceability
Compliance with ISO 15359, making it ideal for lab use and quality assurance

For tests that require evaluating paper slip coefficient using incline plane techniques, the COF-03 Incline Plane Tester is a great alternative. It is particularly effective for evaluating the initial angle at which a paper sample begins to slide—measuring only the static coefficient but offering quick comparative insights.