Additive Diffusion
Fatty acid amide movement within polymeric structures determines the friction properties of converted films. The occurrence of erucamide slip migration involves the slow diffusion of slip additives from the inner bulk of a polyethylene film to its outer surface. This movement begins immediately after extrusion, as the amide molecules are incompatible with the crystalline regions of the polymer.
The resulting microscopic layer on the film surface lowers the coefficient of friction, enabling smooth handling on packaging lines.
Friction Regulation
High concentration of slip additives on the surface can interfere with printing and lamination. If the migration process occurs too quickly or extensively, the accumulated amide layer blocks the adhesion of inks and solventless adhesives. This interference results in ink flaking or poor bond strength between laminated layers.
Controlling the extrusion temperature and storage conditions is necessary to manage the rate at which the additive moves to the surface.
Treatment Interference
Corona treated films suffer from reduced surface energy when slip molecules mask the newly formed polar groups. The migration of these amides can cover the active sites created by the treatment, rendering the surface non-receptive to inks. The rate of this interference depends on the thickness of the film and the concentration of the slip additive used during manufacture.
