Spectroscopic ellipsometric characterization of an aqueous polyacrylic dispersion on steel

Besides thickness and optical constants of the layer, it is equally important to obtain information about how the polyacrylic film is formed on the substrate. Subsequently, the optical model was then used to study the formation of a thin organic layer from an aqueous polyacrylic dispersion at three different temperatures (23 °C, 33 °C and 60 °C). VISSE measurements showed a decrease in layer thickness and an increase in the refractive index of the layer as a function of the drying time for temperatures above the Minimal Film forming Temperature. In order to determine the amount of voids in the acrylic layer, the model was adapted to include a Bruggemann Effective Medium Approximation. It allowed the extraction of the amount of air at every instant during the drying of the layer. It is thus possible to study a polyacrylic layer on a steel substrate using VISSE.