Waterborne polyurethane coatings formulated using an innovative crosslinker, PBI-4NH2, exhibiting superior thermal and hydrophobic characteristics

A new crosslinker, terminal amine-based polybenzimidazole (PBI–4NH 2 ), was made by molecular structure design. The structure of PBI-4NH 2 is characterized by –NH 2 , which can interact with –NCO in aqueous polyurethane systems to form a crosslinking network in the main chain of WPUs efficiently. The PBI-4NH 2 contains five benzene rings, which can significantly improve the overall performance of WPUs. The impact of incorporating PBI-4NH 2 on the thermal resistance, hydrophobicity, and adhesion properties of WPU was examined. The enhancement of PBI-4NH 2 concentration in the WPU system markedly elevated the thermal stability of the coatings, as evidenced by the rise in the T50 % decomposition temperature from 374.1 °C to 394.6 °C. The system's water resistance was markedly enhanced, achieving a maximum water contact angle of 91.1° and a reduction in water absorption rate to 4.79 %. The film's peel strength rose to 3.53 N/mm, while the adhesion attained 1.24 MPa. The novel formulation demonstrated superior overall performance and offered significant reference value for the practical application of aqueous polyurethane coatings.