Development of Self-Healing 2 K Waterborne Polyurethane Coatings with PVA/Polyurea Microcapsules for Enhanced Corrosion Protection

The inevitable damage to paint films during coating applications significantly reduces their protective performance, leaving the underlying substrate vulnerable. Developing self-healing coatings is therefore of critical importance. This study presents the synthesis of polyvinyl alcohol (PVA)/polyurea hybrid microcapsules (MCs) loaded with isophorone diisocyanate via interfacial polymerization in an oil-in-water emulsion, with PVA serving as the emulsifier. These microcapsules were incorporated into acrylic resin, along with a dispersant, co-solvent, and isocyanate curing agent, to formulate a microencapsulated self-healing two-component waterborne polyurethane (2 K WPU) coating. The microcapsules were characterized using TG, FTIR, and SEM. The influence of PVA's polymerization degree and alcoholysis degree on microcapsule properties was systematically analyzed. Results indicate that PVA 1799 as an emulsifier yields microcapsules with minimal surface folds and smooth morphology. When 9 wt% of MC 1799 was added to the 2 K WPU coating, the resulting formulation exhibited optimal performance, achieving an average particle size of 29 μm, along with superior self-healing and anti-corrosion properties. This research offers a novel approach for developing high-performance self-healing coatings with potential industrial applications.