Advancing polyurethane acrylate coating with silane termination: Influence on structural and functional performance

Abstract

The exceptional synergistic effects and intrinsic stability of hybrid polyurethane resins make them a preferred choice for coating applications. We synthesized a range of in-situ silane-terminated polyurethane acrylate (SPUA) resins by modifying the proportions of Vinyltrimethoxy silane (VTMS) and 2-hydroxyethyl methyl acrylate (HEMA) during solution polymerization. Subsequently, the wood and mild steel panels were coated with SPUA hydride resin and cured using UV radiation. UV-curing triggered the initiation of free-radical polymerization, evidenced by the disappearance of CC absorption bands in FT-IR, resulting in the formation of a crosslinked network with the substrate. This resultant coating possesses transparency, a gloss value of 84–90 GU at 60°, high crosslinking (gel fraction >97 %), optimal viscosity (20–40 Pa s), lowered glass transition temperature (71-55 °C), and thermal stability (over 400 °C). The hybrid coating exhibited enhanced water absorption resistance, evidenced by an increased water contact angle (75–95 °C), attributed to a reduction in the surface free energy of the polar component. The strong bonding between the cross-linked silane-terminated polyurethane-acrylate network, and the substrate is the reason behind the significantly improved mechanical properties, including pencil hardness (3H–4H), impact strength (25–35 cm), flexibility (0.2–0.1), solvent rub resistance (>450) and adhesion strength on wood substrate (4.9–7 MPa). This study shows that organosilane modification of polyurethane-acrylate resin enhances coating properties, providing a viable alternative to conventional emulsion polymerization systems.