Slip and Antiblock Additives Migrating into a Sealed Film
Excess primary amide migration depresses hot tack and seal peel strength; control with secondary amides or non-migrating siloxanes verified via ATR-FTIR.
Oleamide Blooming
Meaning
The surface accumulation of a fast-migrating primary amide slip agent on a polymer film or molded part reduces the static and dynamic friction of the plastic. This phase-separation process, known as oleamide blooming, governs the rapid development of slip properties in polyethylene films within hours after extrusion. The phenomenon applies to low-density polyethylene and linear low-density polyethylene films but ceases to be effective if the storage temperature drops below the glass transition temperature of the polymer.
Crystalline Exclusion
Crystalline regions in the cooling polymer reject the amide molecules due to their low solubility in the solidifying resin. Oleamide blooming is driven by this migration from the crystalline structure into the amorphous zones and then to the surface. This migration occurs much faster than that of erucamide due to the shorter molecular chain of the oleamide molecule.
Friction Reduction
The migrated additive forms a microscopic crystalline layer on the surface that acts as a solid lubricant. This layer reduces the coefficient of friction, allowing film webs to slide smoothly over machinery during bag-making operations. Converting plants rely on this change to maintain high-speed production line throughput.
Surface Contamination
Excessive surface blooming of the additive creates a white haze that reduces the optical clarity of clear packaging films. This heavy layer also prevents adhesion of printing inks and laminated layers to the film surface. Extruder operators must monitor the dosage of the slip concentrate to avoid these surface issues.