Quantifying Surface Energy Values on Polyolefin Packaging Materials
Polyolefin surface energy quantification relies on standardized liquid titration or goniometry to secure ink adhesion and lamination bond strength across runs.
Corona Discharge Oxidation
Surface Activation
Surface activation technique using high-voltage electrical fields increases the energy of polymer films to improve liquid adhesion. Applying corona discharge oxidation introduces polar groups, particularly hydroxyl and carboxyl species, to the chemically inert surface of materials like polyethylene or polypropylene. This adjustment raises the surface tension of the substrate, which allows aqueous inks and adhesives to wet out evenly without reticulation.
Treatment Mechanism
High-voltage electrodes discharge ionized air across a grounded roller to generate a localized plasma that breaks molecular bonds on the moving web. The process must be carefully controlled because excessive electrical intensity can damage the substrate, causing pinholes or back-side treatment where the roll side becomes unwantedly polar. Online monitoring of the discharge power ensures consistent treatment levels during high-speed converting runs.
Decay Rate
Chemical changes from the electrical treatment are temporary because the polar groups rotate back into the bulk polymer over time or are masked by migrating additives. Extruded films subject to corona discharge oxidation should be printed or laminated within a short window after treatment to avoid adhesion failure. Storage temperature accelerates this decay, meaning that warm warehouse conditions can quickly reduce the surface energy of treated rolls to their original untreated states.
High-slip additives migrate rapidly to the surface, where they form a barrier that cancels the effect of the oxidation process within days of production.