Modeling the wetting of titanium dioxide and steel substrate in water-borne paint and varnish materials in the presence of surfactants

Abstract

This paper reports the results of studying the effect of two additives such as polyether siloxane (PS) and sodium polyacrylate (SPA) on the wetting of various substrates in water-borne paints (WB paints). Titanium dioxide (TiO2), paraffin (PA), steel (ST), and glass (GL) were used as solid substrates. The edge wetting angle (θ0) and the ratio (dCosθ/dСS) were used as the criterion for assessing the wettability of solid substrates. In aqueous solutions (without acrylic resin), both surfactants improve the wetting of the substrates. For PS, all the substrates studied, depending on θ depression, can be arranged in a row: ST>PA>GL>TiO2. For SPA: PA>TiO2>GL>ST. The introduction of an acrylic film-forming agent in the composition enhances the wetting ability of SPA (in comparison with the aqueous solution of surfactants). With an increase in the concentration of SPA from 0 to 4 g/dm3 in acrylic resin solutions, the edge wetting angle of steel decreases by 6÷8° (while in water by only 3°). With respect to TiO2, the wetting activity of SPA does not depend on the acrylic content of the water. PS in acrylic-containing compositions exhibits worse wetting activity than SPA. The introduction of surfactants in the compositions improves the quality of coatings. With optimal SPA contents in the compositions, the corrosion rate of coatings is reduced (in distilled water by 45 %, in 60 % NaCl solution by 60 %). At the same time, the gloss of coatings increases by 50 % while adhesion increases by 2 points (according to ISO 11845: 2020). This is fully correlated with the nature of the effect of surfactants on the wetting of the steel substrate and pigment (titanium dioxide). Based on probabilistic-deterministic planning, the compositions of WB paints were optimized, ensuring their maximum wetting of TiO2 and ST. Equations for calculating cosθ depending on the content of acrylic polymer and surfactants have been derived