A method of studying carbon particle distribution in paint films

The process of dispersion of pigment particles within the resinous component 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 rheological properties of a paint system. In the present paper we describe a method of treatment of carbon black paint film which enables the determination of distribution of carbon black particles in the film. The method is based on selective etching of the paint using a low pressure weakly ionized highly 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 neutral oxygen atoms of 4.4 x 10(20) m(-3), high selectivity of etching is obtained. At these conditions, optimal time of etching is approximately 30 s. The etching is due mainly to interaction of neutral oxygen atoms with surface carbon atoms and the probability for interaction is estimated to 0.026. (C) 2000 Elsevier Science S.A. All rights reserved.