Sustainable Waterborne Polyurethanes with Improved Self-Healing and Performance Using Bio-Derived Vanillin and Olive Oil Polyols

Abstract This study introduces a new waterborne polyurethane (WPU) system that incorporates a vanillin-derived diol with dynamic Schiff base linkages, enabling reversible covalent interactions within the polymer matrix. Vanillin, an economical, bio-sourced molecule, was utilized to synthesize this functional diol, which was included as a chain extender with olive oil-derived polyols (OOP) and isophorone diisocyanate (IPDI). The incorporation of Schiff base chemistry into the system imparts self-healing and reprocessability properties to the material while also enhancing its mechanical integrity. A Design of Experiments (DoE) methodology was employed to optimize the formulation, concentrating on key factors including dimethylolpropionic acid (DMPA), vanillin diol (VAN-OH), and olive oil polyols. The optimized WPU-VAN-OH formulation demonstrated a tensile strength of 9.2 MPa and showed exceptional thermal stability, with a degradation onset temperature of 354°C. The WPU-VAN-OH formulation demonstrated remarkable self-healing capabilities, with full restoration of surface scratches within 30 minutes at 70°C. The synthetic WPU films were evaluated for their structural, thermal, and mechanical properties using NMR, FT-IR, SEM, and mechanical tests. The findings demonstrate the appropriateness of the WPU-VAN-OH system for applications necessitating durable, self-repairing, and eco-friendly materials.