Tri-functional Bio-friendly Cross-linker for UV-Curable Coatings: Synthesis and Study of Viscoelastic Properties

Protection of the environment and keeping it from contaminants are critical issues. Polymers and oil-based plastics are unrenewable and entail a wide range of environmental pollution due to the long degradation. This study aims to synthesize bio-based coatings using natural substances, and evaluate their viscoelastic properties. Accordingly, first, UV-curable tri-functional castor oil-based waterborne urethane acrylate as a bio-friendly cross-linker was synthesized. Next, different weight percentages of the synthesized cross-linker were added to the UV-curable urethane acrylate resin, followed by UV radiation exposure to prepare, different flexible composite coatings. FT-IR spectroscopy was used to examine the progress of the cross-linker synthesis. The particle size analysis confirmed the stability and homogeneous distribution of the cross-linker particles in the emulsion. By DMTA analysis, viscoelastic characteristics of the films were studied. As a result, adding specific weight percentages of cross-linkers to the polymer matrix caused an increase in storage modulus and improvement of Tg of the coatings. The cross-link density of the film coatings was estimated from DMTA. The more weight percent of the cross-linker, the more is the cross-link density. Keywords