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.
Corona Discharge Oxidation
Meaning
Electrical surface treatments create high-energy functional groups on the surface of non-polar polymers to improve wettability and adhesion. Corona discharge oxidation uses a high-voltage electrode to generate plasma that breaks molecular bonds, allowing oxygen to bond to the surface of films or moulded parts. This process increases the surface energy of materials like polyethylene and polypropylene, which are naturally resistant to inks and adhesives.
The treatment is typically performed inline during the extrusion or conversion process. It transforms a chemically inert surface into one that can form strong bonds with coatings.
Treatment Intensity
Power levels applied by the corona station determine the density of the oxygen-containing groups created on the surface. If the watt density is too low, the ink will not wet out and will bead up or flake off. Conversely, excessive power can damage the polymer surface or lead to back-side treatment on a roll of film.
Operators use dyne pens or contact angle measurements to verify that the energy level meets the specification for the intended application.
Surface Energy
Polar molecules introduced by the discharge provide the necessary sites for chemical and physical bonding. These groups include hydroxyl, carbonyl and carboxyl functionalities. They increase the attraction between the polymer and the liquid coating being applied.
Without this treatment, the surface energy of a polyolefin is usually below thirty-two dynes, which is insufficient for most industrial printing processes.
Degradation Rate
Decay of the treatment effect occurs as the modified surface groups migrate into the bulk of the polymer or are covered by blooming additives. Slip agents and antistats are particularly prone to moving over the treated surface, which lowers the effective dyne level. This means that a film treated today may not be printable in three months.
Storage conditions and resin formulation are major factors in how long the oxidation remains effective.