Fatty Acid Amide Transport Kinetics in Flexible Polyolefin Packaging
Polyolefin slip kinetics depend on additive supersaturation, where migrating fatty acid amides form nanometer-scale boundary layers to balance friction and seal integrity.
Stearamide
Meaning
Saturated fatty acid amides serve as slow-migrating slip agents that provide consistent friction reduction over the shelf life of a plastic part. Stearamide is frequently selected for applications requiring higher thermal stability and less interference with downstream printing or sealing compared to unsaturated alternatives. Its molecular structure allows it to move to the surface at a moderate pace, creating a stable lubricating film.
This additive is common in polypropylene and polyethylene resins used for caps, closures and durable goods. It helps in reducing the torque required to open containers while maintaining a clean surface appearance.
Heat Stability
Oxidation resistance is a primary feature of this saturated molecule during high-temperature melt processing. Unlike oleamide, it does not easily break down or cause odor when exposed to the heat of an injection moulding barrel. This makes it suitable for parts that require long residence times or multiple heat cycles.
The lack of double bonds in the carbon chain prevents the yellowing that can occur with less stable slip agents.
Bloom Profile
Surface concentration develops gradually, which allows for better control of the final coefficient of friction. The additive does not overwhelm the surface immediately, giving more time for processes like corona treatment or labeling. Because it is saturated, the film it forms is more uniform and less prone to becoming greasy or sticky.
This controlled migration is ideal for parts that need to maintain their performance for months or years.
Industry Choice
Rigid packaging manufacturers often prefer this grade for its reliability and neutral effect on the base polymer. It is used extensively in the production of polyolefin screw caps to ensure they can be easily applied and removed by the consumer. The additive also reduces the wear on the moulding equipment by lowering the friction between the plastic and the steel.
Its predictable behavior makes it a staple in the formulation of masterbatches for general-purpose moulding.