Fuente: Journal of applied polymer Lugar: RESEARCH ARTICLE Dynamic hindered urea bonds endow UV-curable polyurethane-acrylate coatings with self-healing, recyclability, and improved protective performance.


ABSTRACT
To address health and safety concerns associated with volatile organic compounds (VOCs) in traditional solvent-based coatings, we developed recyclable, ultraviolet-curable polyurethane–acrylate (PUA) coatings incorporating dynamic hindered urea bonds (HUBs). The introduction of dynamic covalent bonds enables efficient self-healing, recycling, and reprocessing of chemically cross-linked networks, thereby extending the material lifecycle. Hindered urea bonds, formed from bulky amine and isocyanate groups, exhibit reversible behavior attributed to steric hindrance effects. In this study, 2-(tert-butylamino)ethyl methacrylate was employed as an end-capping agent to create partially formed urea bonds within the polyurethane backbone, enhancing hydrogen bonding and improving the mechanical rigidity of the coatings. The segmented structure of polyurethane, comprising soft and hard domains, further facilitates dynamic hydrogen bond formation, promoting superior self-healing and mechanical stability. Additionally, by adjusting the R value of polyurethane and the polydimethylsiloxane (PDMS) content, the hydrophobicity and environmental stability of the HUB-containing PUA coatings were effectively enhanced. The resulting coatings demonstrated high healing efficiency, recyclability, anticorrosion performance, and hardness retention. This work offers a sustainable and practical approach for developing multifunctional, eco-friendly protective coatings with potential applications in reducing waste and promoting material circularity.