Slip Migration
The movement of slip additives from the bulk polymer to the surface of a film reduces the coefficient of friction to facilitate high-speed handling. The process of oleamide exudation is a time-dependent and temperature-dependent phenomenon occurring in polyethylene films. This migration creates a microscopic lubricating layer that permits the film to slide smoothly over metal guides on packaging lines.
Frictional Change
Packaging films require precise friction properties to run efficiently through form-fill-seal machinery. Following extrusion, the additive molecules are dispersed throughout the film before oleamide exudation causes them to move to the outer surface over a period of hours or days. If this migration occurs too slowly, the film has high friction and sticks to the metal forming collars, which leads to jamming and tearing.
When the migration is too rapid or excessive, it creates a thick greasy layer that interferes with both ink adhesion during printing and the strength of thermal seal joints.
Process Interference
Converting facilities must manage storage temperatures carefully to control the rate of slip additive movement. High warehouse temperatures accelerate oleamide exudation, resulting in an excessive concentration of the slip agent on the outer film surface before printing or lamination. This surplus acts as a release barrier, preventing laminating adhesives or inks from bonding securely to the substrate.
Measuring the coefficient of friction and controlling the post-extrusion cooling times are critical steps in maintaining a consistent and printable polymer surface.
