Coefficient of friction (COF) describes how easily one surface slides over another. On a self-adhesive label it is the number that quietly decides whether a roll runs cleanly through your applicator or jams at speed. We measure it in our label laboratory before a film or laminate goes into production for a high-speed line.
What the test measures
- Static COF — the force needed to start the surfaces moving. Too high and the web hesitates at start-up.
- Kinetic COF — the force needed to keep them moving. Too low and rolls telescope or stacks slide apart.
Method
| Item | Condition |
|---|---|
| Reference standards | ASTM D1894 / ISO 8295 |
| Sled | 200 g, 63 × 63 mm contact face |
| Test speed | 150 mm/min |
| Conditioning | 23 °C, 50 % RH, 24 h before testing |
| Pairings tested | face-to-face, face-to-liner, face-to-steel |
| Replicates | 5 per pairing, mean reported |
Reading the result
There is no universally “good” COF — there is only the value your equipment wants. A gloss-laminated BOPP label slides freely and suits fast rotary applicators; a matt varnish grips and suits hand-applied or stacked products. Tell us the applicator and the line speed and we will match the construction rather than guess it.
When to ask for this test
- Automatic applicators running above 100 labels/min
- Switching from paper to film face stock on an existing line
- Changing the surface finish — lamination to varnish, gloss to matt
- Labels that must resist slipping after application, e.g. stacked cartons
Related: BOPP labels · Label Laboratory · Postpress services