Atmospheric plasma
The Plasma sureface treatment technology is based on a simple physical principle.
Matter changes its state when energy is supplied to it: solids becomes liquid, and liquids becomes gaseous. If even more energy is supplied to a gas, it is ionized and goes into the energy-rich plasma state, the fourth state of matter.
With increasing energy input, the state of matter changes from solid to liquid to gaseous. If additional energy is then fed into a gas by means of electrical discharge, the gas will turn into plasma.
Plasma surface treatment: The principle
In comparison to low pressure plasma technology, no special chamber system is required when Openair® plasma technology is used.
The set-up of a corona system for foil treatment generally consists of one or several high-voltage electrodes arranged at a distance of between 1 to max. 3 mm from a grounded roller. If a high voltage is applied to the electrodes, a corona discharge occurs in the gap between the electrodes and the roller, and a plasma is formed. The electrodes and/or the roller are covered with a non-conductive barrier (e.g. ceramic, quartz or silicone), which has also given rise to the term barrier discharge. If a plastic film is guided over the grounded roller through the discharge gap, the surface of the film becomes oxidized. The oxygen in the air serves as the raw material for this oxidation.
As a result of the oxidation reactions, polar groups containing oxygen are implemented in the surface of the plastic, resulting in improved wettability of the surfaces and in most cases also improved bonding on the plastic surface.
How to measure the effect?
The effect of the flame treatment can be measured by contact angle measurement. In practice, test inks are also often used to measure this energy.
