Preparation and characterization of UV-curable water-based alkyd-siloxane composition

A UV-curable alkyd-siloxane composition on a water basis was obtained, as an alternative to a similar composition based on an organic solvent. The emulsion was prepared using commercially available surfactants and free of volatile organic substances (VOCs). The most applicable technology for the production of alkyd-siloxane emulsions is direct emulsification at a temperature of 60°C, and using dynamic light scattering, the hydrodynamic radius of the particles was determined to be 132 ± 38 nm. The resulting emulsion has an aggregative and sedimentation stability during storage up to 3 months; however, the temperature difference causes the destruction of the colloidal system. The curing reaction occurs within 10 min to form a coating containing 95% gel fraction. Emulsion-based coatings have better properties relative to alkyd coatings but are not significantly inferior to coatings from an organo-soluble UV-curable composition. Coatings based on UV-cured materials have shown low chemical resistance, which limits their use in conditions where contact with aggressive liquids occurs. The presence of surfactants in the coating reduces the water contact angle by 4° and increases water absorption by 1.5% relative to coatings based on organo-soluble alkyd-siloxane composition. Sorption studies have shown that the diffusion coefficients of water into the coating from the emulsion and the organo-soluble system have the same values and amount to 8.35·10⁻⁹ cm²/s. The difference in the glass transition temperature of coatings obtained from an emulsion (21.0°C) and a solution (24.2°C), as well as a decrease in heat resistance, indicates a lower degree of crosslinking due to the presence of surfactants in the system. Elemental and morphological analysis showed that there is no phase decay during the process of coating formation, and all elements are evenly distributed over the surface. A comparative analysis of the results of the study with the literature data showed that the obtained emulsion is not inferior in properties to other UV-curable water-based materials.