Microstructural surface properties of powder film in electrostatic coating process

Abstract

In an electrostatic powder coating process, several forces effect the deposition of charged polymer paint particles and the adhesion of the deposited particles on the grounded substrate being painted. In this paper, the authors discuss the roles and relative magnitudes of these forces. They present a model on the deposition of a charged particle approaching the surface of the substrate. Once the particle deposits on the surface and when the high voltage is turned off, the particle experiences (1) the force due to the image charge of the underlying powder layer, (2) the force due to the image charge of the particle, (3) the repulsive force between the charged particle and the charge on the powder layer, and (4) the van der Waals force between the particle and the adjacent particles deposited on the substrate. The model shows criteria on whether the particles will deposit on the substrate and, if deposited, whether it will remain on the surface of the powder layer once the corona field is turned off. These relative forces influence the microstructure of the powder layer and may affect the ultimate appearance or the texture of paint film after curing. >