Surface Diffusion
Spontaneous diffusion of fatty acid amide additives from polymer matrices to film surfaces lowers kinetic and static coefficients of friction. Flexible packaging testing evaluates polyolefin slip agent migration to track fatty acid amide movement in polyethylene and polypropylene extrusion coatings. Erucamide and oleamide additives dissolve in molten polymer during extrusion, then recrystallize and migrate toward the surface during film cooling and storage.
Diffusion rates depend on polymer crystallinity, storage temperature, and additive molecular weight.
Friction Modification
Exuded slip agent molecules form an oriented monomolecular layer that reduces sliding friction between film layers and packaging equipment metal surfaces. Lower friction coefficients prevent web dragging, jamming, and telescoping during film unwinding and pouch forming. Excessive additive concentrations, however, lead to blooming, where thick slip agent deposits create surface haze and greasy residues.
Converters measure static and dynamic friction over storage time to verify that slip performance stabilizes within target parameters.
Converting Interference
Excess slip additive accumulation on polymer coated paperboard surfaces impairs downstream converting operations like printing and heat sealing. Migrated fatty amides lower surface energy, causing solvent-based and water-based printing inks to bead up or flake off converted packaging. Heat seal strength declines when thick slip layers interfere with polymer chain entanglement across heat seal interfaces.
Polyolefin slip agent migration monitoring allows packaging converters to balance low friction requirements against ink adhesion and seal integrity in high speed form-fill-seal packaging operations. Proper additive dosage ensures optimal runnability without compromising structural packaging bond performance.
