Slip Agents

Slip agents are typically fatty amide compounds, such as erucamide or oleamide, that are blended into resin at low concentrations, often well under one percent by weight. After the film is extruded, these molecules gradually migrate, or bloom, to the surface over a period of hours to days, forming a microscopically thin lubricating layer. That surface layer lowers the film's coefficient of friction, meaning film slides against itself or against metal machine parts more easily rather than dragging or sticking.

This is essential for how film performs on customer equipment; without adequate slip, film can jam in form-fill-seal machines, fail to feed properly off a roll, or bind up in high-speed bag-making equipment. Because slip agents need time to migrate to the surface, freshly extruded film often has a higher coefficient of friction than the same film a few days later, which is why converters and packagers sometimes specify an aging or curing period before film is run on demanding equipment.

Slip agents work in tandem with anti-block additives, since reducing surface friction and preventing layers of film from sticking together are related but distinct problems, and most commercial film masterbatches are formulated with a balance of both to get a film that runs smoothly without blocking on the roll.

A film that runs perfectly on a packaging line after sitting in inventory for a week, but jams or feeds poorly when used immediately off the extrusion line, is showing a classic slip agent migration timing issue rather than a defect in the resin itself.

It's a common misunderstanding that slip agent percentage can simply be increased indefinitely to fix any friction problem. Excess slip agent can actually interfere with print adhesion, lamination bonding, and heat sealing, since the same surface migration that reduces friction also contaminates the surface that ink, adhesive, or a heat seal bar needs to contact directly.