This study investigates the impact of dibutyltin dilaurate (DBTDL) and dibutyltin diacetate (DBTDA) catalysts on the properties of bio-isocyanate trimer-based polyurethanes, focusing on their Diels-Alder (DA) self-healing mechanism. Polyurethane prepolymer, derived from polyethylene glycol and pentamethylene diisocyanate trimer, was functionalized with furfuryl amine and crosslinked with bismaleimide to form self-healing networks. Fourier-transform infrared spectroscopy (FTIR) analysis confirmed successful bond formation in both catalyst systems, with no significant chemical structural differences. However, differential scanning calorimetry (DSC) analysis showed DBTDL resulted in superior DA crosslinking, as indicated by a greater reduction in the PEG melting enthalpy and increased gel content compared to DBTDA. The thermal reversibility of the DA bonds was also demonstrated. Both qualitative (optical microscopy) and quantitative (tensile testing) assessments revealed over 100% self-healing efficiency for both catalysts, with DBTDL-catalyzed polyurethanes exhibiting better tensile strength recovery. These findings suggest DBTDL is more effective in enhancing DA crosslinking and polymer network recovery, thereby significantly improving the self-healing performance of bio-based polyurethanes. This emphasizes the importance of optimal catalyst selection for maximizing the mechanical properties and healing capabilities in sustainable coating applications.

Keywords: self-healing polyurethane, Diels-Alder reaction, biobased, isocyanate trimer, catalyst, dynamic crosslink.