Meaning
Migration of low molecular weight surface agents to the exterior of a polymer film creates a powdery or waxy film disruption. Slip additive bloom happens when internal lubricants like erucamide or oleamide push through the bulk matrix to the surface interface. This phenomenon decreases the coefficient of friction and modifies the tactile properties of the material for downstream packaging equipment.
The condition terminates when the additive concentration reaches equilibrium or the film surface saturation point causes visible residues.
Additive Kinetics
Molecular diffusion rates govern how quickly a film reaches its target friction profile after extrusion. Temperature fluctuations in storage accelerate the migration of fatty acid amides toward the surface area. High humidity or rapid cooling cycles alter the solubility of these agents within the polyethylene structure.
Moulders often observe that regrind fractions shift the timing of this effect because prior thermal history changes the remaining concentration of active agents.
Operational Penalty
Unintended surface deposition creates significant friction management issues during high speed bag forming or pouch filling operations. Excessive migration leaves white streaks on transparent packaging which compromises the visual quality of the product for the consumer. Accumulation of loose powder on rollers or sealing jaws requires frequent machine cleaning to prevent downtime or seal integrity failure.
Measurement Protocol
Technicians verify surface levels using a sliding sled test to quantify the kinetic and static friction forces of the polymer. Datasheet values describe the nominal additive loading but they rarely account for the variable transition period of material stored in high heat warehouses. Measurements taken on the shop floor vary from laboratory results because local environmental conditions dictate the current saturation state of the film.
Regular testing confirms whether the additive concentration maintains the specified performance range throughout the shelf life of the material.
