Electric conductivity measurements in water dispersion paints for mechanistic studies of reflection properties formation during surface painting and paint film drying

Abstract

Electric conductivity measurements of water dispersion paints were carried out in order to understand the mechanism of film formation and drying and the formation of painted surface reflection properties. The classical model of electric conductivity in viscous media based on a comparison of the Coulomb and Stokes formulas was used to determine the effective mechanism of the paint properties. This model was verified by measurements in the paint bulk. The classical concept of the electric conductivity of viscous liquids was found to be applicable to the conductivity analysis of the studied water dispersion paint specimens. The electric conductivity of the studied paints was found to be determined by the existing admixtures being soluble in water and/or dispersion organic particles. The formulated method for dynamic conductivity measurements of paint film thickness assumed a constant temperature and viscosity. Strong electrostatic phenomena were detected at the initial stage of paint aerosol deposition, while a compact film has not been formed yet. The film conductivity measuring experiments found that the film drying process consists of two stages. At the first stage, conductivity is sharply decreasing and the paint film reflectivity is sharply increasing. At the second stage, evaporation is delayed. It is limited by the diffusion transfer of volatile components from the film bulk and from the paint dispersion particles. Here, a slow growth of the reflectivity and a decelerating decrease in the conductivity is observed. A qualitative mathematical dynamic model was developed for the paint film reflectivity due to the orientation of pigment particles, and the calculations showed that the first stage of drying is the most important for the orientation.