Manipulating a novel epoxy film adhesive with UiO-66 and amine-functionalized UiO-66 for designing a structural adhesive in aluminum- aluminum bonded joints

Structural epoxy-based adhesives play a vital role in advanced industries; however, their inherent brittleness and low fracture toughness significantly limit their structural reliability. This study systematically investigates the reinforcement of an epoxy/novolac film adhesive using pristine UiO-66 nanoparticles and their amine-functionalized counterparts (NH 2 -UiO-66) to elucidate the role of interfacial chemical bonding. Nanocomposites were prepared with different nanoparticle loadings (0.3, 0.5, and 0.7 phr) of each nanoparticle, and their mechanical and thermal properties were evaluated. The results revealed remarkable improvements, with the sample containing 0.5 phr NH 2 -UiO-66 exhibiting optimal performance. Compared with neat epoxy, this nanocomposite showed increases of 97% in ultimate tensile strength (UTS), 317% in toughness, 52% in lap shear strength (LSS), and 87% in peel strength. X-ray photoelectron spectroscopy (XPS) analysis confirmed the formation of strong covalent bonds between the amine groups of the nanoparticles and the epoxy matrix. Moreover, differential scanning calorimetry (DSC) analysis demonstrated the effective role of the amine groups in enhancing the curing kinetics of the epoxy adhesive. This study highlights the critical role of nanoparticle surface functionalization in the rational design of next-generation high-toughness structural adhesives for advanced engineering applications.