A method of studying carbon particle distribution in paint films

The process of dispersion of pigment particles within the resinous componen t of the system is one of the most important parameters in the manufacture of any surface coating. Determining the degree of pigment dispersion is of fundamental importance, since it affects the optical, color strength and rh eological properties of a paint system. In the present paper we describe a method of treatment of carbon black paint film which enables the determinat ion of distribution of carbon black particles in the film. The method is ba sed on selective etching of the paint using a low pressure weakly ionized h ighly dissociated oxygen plasma. At the pressure of 50 Pa, the neutral gas temperature of approximately 50 degreesC, the electron temperature of 5 eV, the density of charged particles of 2 x 10(15) m(-3) and the density of ne utral oxygen atoms of 4.4 x 10(20) m(-3), high selectivity of etching is ob tained. At these conditions, optimal time of etching is approximately 30 s. The etching is due mainly to interaction of neutral oxygen atoms with surf ace carbon atoms and the probability for interaction is estimated to 0.026. (C) 2000 Elsevier Science S.A. All rights reserved.