Dielectric Activation
High voltage electrical discharge applied to polymer film surfaces raises the dyne level of polyethylene and polypropylene substrates before printing or extrusion coating. Corona surface treatment bombards plastic webs with ionized air, oxidizing the molecular chains to create polar sites. Converting lines run at high speeds while electrode stations generate a plasma arc across the web width.
Low surface energy materials naturally repel aqueous coatings and solvent inks, which leads to poor bond strength and delamination on the converter floor. Molecular modification changes the inert surface into a receptive landing zone for inks, adhesives, and extruded laminating resins. Polymeric films extruded without this activation fail standard tape tests because the polar groups remain unformed.
Converters measure the resulting energy gain in dynes per centimeter using certified test inks applied immediately after the discharge station.
Molecular Oxidation
Oxygen molecules dissociate within the electrical arc and graft onto the polymer backbone, replacing hydrogen atoms with hydroxyl and carbonyl groups. Web speed, electrode gap, and applied wattage dictate the depth and density of these polar functional sites. Inadequate treatment leaves untreated islands across the web width, whereas excessive discharge degrades the polymer film and causes pinholes or back-side treating.
Laboratory testing verifies that oxidized sites decay over time, particularly under elevated storage temperatures and high humidity conditions.
Adhesion Optimization
Packaging laminators rely on sustained surface energy to anchor extrusion polyethylene onto metallized polyester or paperboard substrates. Lamination bond strength depends entirely on the permanence of the polar groups created during the upstream discharge phase. Converters compensate for dyne decay by placing the treating station directly before the coating nip or printing deck.
Laminated structures withstand retorting and pouch conversion forces only when the initial molecular oxidation exceeds specific threshold requirements.
