Friction Degradation
Dynamic friction coefficients between sliding contact surfaces often decrease during repeated mechanical movement as surface asperities wear down or slip additives migrate. Observing kinetic COF decay indicates a continuous reduction in sliding resistance over time or across multiple friction test passes. This physical change occurs when micro-roughness on paper coatings or polymer films smooths under sliding pressure, reducing mechanical interlocking between surfaces.
Surface Smoothing
Continuous contact on high-speed converting lines subjects packaging materials to repeated rubbing actions against metal guides and adjacent package surfaces. As kinetic COF decay progresses, slip agents such as erucamide or fatty acid amides shear under friction, creating a lubricated monomolecular layer at the contact interface. In paperboard coatings, soft synthetic waxes deform under sliding loads, filling surface micro-voids and lowering dynamic friction.
Laboratory friction testers record this decay across multiple test cycles, showing a steep drop in frictional force during initial passes before reaching a stable baseline. Uncontrolled loss of friction causes stacked folding cartons to destabilize during transport or high-speed palletizing.
Operational Limit
Excessively low friction levels disrupt pallet stack stability, causing unit loads to shift during transit. Converting lines adjust wax additive concentrations to maintain dynamic friction within safe processing bounds.
