Selective plasma etching of powder coatings

The technology of selective plasma etching was applied in order to study particle distribution in powder coatings. Etching was performed in pure oxygen plasma. Plasma parameters were measured with a double Langmuir probe and a catalytic probe. At the neutral gas temperature of approximately 50 degreesC, the electron temperature was approximately 60 000 degreesC, the density of positive ions approximately 1 x 10(16) m(-3), and the density of neutral oxygen atoms 2 x 10(21) m(-3). In order to prevent sample overheating, plasma was applied in time intervals of 20 s. The removal of the polymer matrix was accomplished within 2-4 min. After plasma treatment, the samples were analyzed with a scanning electron microscope. All the pigment and filler particles were left intact thus enabling the determination of the original distribution of the particles in the coating. (C) 2003 Elsevier B.V. All rights reserved.