Plastics in general have low surface energy. Many polymers are non polar, so that molecules of coating materials (glue, resins, laquer) do not find links to adhere. Special treatment of such surfaces must be provided to enable wetting of the surface and sufficient adhesion.
Activation of plastic surfaces therefore is a most important application of plasma technologies.
Prior to the activation process surfaces to be coated need to be high-puridity plasma cleaned. This process removes all antiadhesive deposits from the surface. The subsequent activation process generates reactive links to the polymers of the substrate. Very often terminating hydrogen atoms are removed from the surface by an oxygene plasma and replaced by oxygene atoms which provide links to the molecules of coating substances. Therefore this process may increase the surface energy of plastics drastically.