Surface Preparation of Polymers. Corona treatment is a quick and inexpensive method for improving surface energy on plastics. This process involves the atmospheric generation of ozone in an electrical discharge, which induces oxidation of the surface. Because corona treatment can be quixotic in its effect, an alternative is oxygen plasma treatment, which requires a closed chamber but leads to more reliable oxidation. Strong plasma treatment can damage subsurface layers, so it is essential to use correct power and exposure times.
Flame treatment is effective and inexpensive but requires good process control to prevent scorching.
Strong oxidizing acids, such as chromic acid, can also be used to oxidize a substrate surface, though acid oxidation carries the drawback of hazardous material handling and waste. Grit blasting or scuff sanding can be useful on some plastics, although these methods merely increase surface area and do not improve surface energy. Thus, if the surface energy is poor, one has simply increased the amount of poorly bonded surface. Primers can be used to form a modification layer on the surface that provides an interactive surface chemistry for the adhesive. Priming can be combined with other methods such as surface abrading or etching, as is frequently the case with metals bonding.