For surfaces with a low surface tension, coating or bonding with adequate results is not possible. In many cases, and by means of plasma technology in practically every case, the surface tension can be increased to ensure perfect bonding.
Activating plasticsMost plastics have a very low surface tension. It usually is smaller than the surface tension of most liquids which form the basis of adhesives, varnishes and paints. Thus, no wetting by the coat takes place, and thus the coat will not adhere.
This is attributable to the non-polar character of most plastics.
The surface tension of non-polar plastics can be considerably increased in the oxygen plasma. Due to their high reactivity, oxygen radicals can form polar bonds which create the bonding spots for liquids applied to the substrate. This increases the surface tension and provides wettability. When plasma treatment in the oxygen plasma is continued for a prolonged time, the plastic will be etched. This may be desirable or not. Etching of plastics primarily increases the surface, which promotes good bonding. fördert.