Oxygen plasma etching of a two-component clear coating

Different polymers with various chemical and physical properties are used as a binder in pigmented coatings. The etching rate of these coatings with neutral oxygen plasma depends on the nature of the applied binder. To optimize the process, the chemical reaction of the oxygen plasma with the binder should be analyzed. The etching of a two-component polyester-polyisocyanate system was analyzed for these reasons. A low etching rate was observed when the exposure time was not longer than 100 s. No differences in the chemical structure of the etched layer were observed by the infrared analysis under these conditions. At longer exposure times a rapid increase of etching efficiency occurs where the chemical structure of the polymer changes appreciably. The infrared spectra show the partial breaking of cross-links between both components. The abrupt change in the chemical structure of the polymer corresponds to the rapid increase in etching efficiency. Practically no further changes were observed at longer exposure to the neutral oxygen plasma.