Do you know the role that Vetaphone’s Corona treatment has in your industry?
Many of us know the importance of Corona treatment when printing on the surface of synthetic materials, but how many of us really understand the science behind the process?
Corona treatment is a high frequency discharge that increases the adhesion of a plastic surface. Whether a liquid moistens the material well or badly depends mainly on the chemical nature of both the liquid and the substrate. Moisture is defined as the ratio between the energies of the surface of the liquid and the substrate.
The pre-treatment offered by the corona process is necessary to obtain sufficient wetting and adhesion on plastic film or foil before printing, laminating or coating takes place. A corona discharge unit is used to optimize wetting and adhesion, and the technique has proven to be highly efficient and cost-effective, especially since it can be carried out in-line.
Being a man-made synthetic material, plastic consists of chains of molecules joined end to end to form even longer chains. These bonded chains present few bonding opportunities on the surface and must be opened to increase wettability.
Directing a high-frequency discharge at the surface of the plastic from a close range simply breaks up the molecules by oxidizing them. The discharge splits carbon molecules and breaks oxygen into iodines, some of which enter the surface layer of the plastic and enhance bonding, while others form ozone that must be removed.
The new carbonyl groups created have a higher surface energy and this improves the chemical connectivity (dynes / cm) between the liquid and the plastic.
Corona treatment affects only the surface layer of the plastic, to a depth of 0.01 microns, and does not change its appearance or resistance.