Biobased Catalyst-Free Polyester–Epoxy Powder Coatings with Self-Healing Functionality

Powder coatings represent an environmentally friendly alternative to conventional liquid coatings, offering solvent-free application, high material efficiency, and excellent mechanical performance. However, they still face several sustainability challenges, including reliance on fossil-derived resources, the use of toxic curing agents, and limited repairability after damage. In this study, three carboxy-functional polyester resins (PES) containing increasing amounts of internal tertiary amine moieties were synthesized from renewable succinic acid and isosorbide. The resins were subsequently blended with a resveratrol-derived epoxy (REP) curing agent to produce biobased powder coatings with enhanced sustainability and intrinsic self-healing capability. All formulations contained at least 86.7% renewable content and exhibited excellent solvent resistance as well as strong adhesion to metal substrates. Importantly, the incorporated tertiary amine moieties act as internal catalysts for dynamic transesterification reactions, imparting repairability to the cured coatings. Without applied pressure, the coating with the highest tertiary amine content achieved a repair ratio of 85.7% after heating at 200 °C for 10 min. This study presents a promising strategy for developing catalyst-free powder coatings that combine high performance, high biocontent, and intrinsic self-healing capability.