Surface Activation
High voltage discharges applied to a moving web during the converting process increase the surface energy of non-polar substrates. The use of inline corona treatment allows for better adhesion of inks and coatings on materials like polyethylene or polypropylene. This process creates polar groups on the surface of the film, which makes it more receptive to water-based fluids.
Electrical Interaction
A power supply generates a high-frequency electrical signal that is sent to an electrode positioned above a grounded roller. As the film passes through the air gap, the discharge ionizes the oxygen molecules, which then react with the polymer chains on the surface of the material. This oxidation is confined to a very thin layer and does not change the bulk properties of the film.
The intensity of the treatment is controlled by adjusting the power output and the line speed.
Print Quality
Maintaining a high surface energy is needed to prevent the ink from beading up or scratching off after the printing process. Because the effects of the treatment can diminish over time, performing the process immediately before the coating station ensures maximum effectiveness. This step is a standard requirement for high-speed flexographic and gravure printing on plastic-coated boards.
Proper treatment levels are verified using dyne pens or contact angle measurements.
