Fabrication and characterization of polyether polyester–based polyurethane/epoxy composites modified with zirconium dioxide nanoparticles

Epoxy resin adhesives are widely used in structural repair; however, their high cross–linking density often results in limited toughness and interfacial durability. Given the high surface energy and presence of hydroxyl groups, nanoparticles are prone to aggregation via strong intermolecular interactions. In this study, a silane–assisted dispersion strategy was proposed to enhance the toughness of polyether–type polyurethane/epoxy resins by adding ZrO 2 nanoparticles. Silane coupling agent (KH550) was employed to chemically modify the surface of ZrO 2 , and ultrasonic treatment was applied to improve nanoparticle dispersion within the PU/EP matrix. The repair performance of the composites was evaluated through the compressive and flexural bond strength tests. The results indicate that KH550-modified ZrO 2 (KH550-ZrO 2 ) can enhance the mechanical properties and adhesive strength of PU/EP interpenetrating network (IPN) composites, increasing the dry and wet bonding strengths to 6.52 MPa and 5.47 MPa, respectively. The tensile and compressive strengths of the composites reached maximum values of 71.12 MPa and 79.57 MPa at 0.8 wt% KH550–ZrO 2 .This study provides an effective strategy for enhancing the mechanical performance of ZrO 2 –reinforced PU/EP IPNs.