High-performance epoxy nanocomposite adhesives with enhanced mechanical, thermal and adhesion properties based on new nanoscale ionic materials

Epoxy (EP) adhesives as high-shear strength permanent adhesives have been used in various engineering applications, particularly aerospace and automotive. However, these adhesives suffer from disadvantages such as high fragility, poor tensile strength, and toughness, which limits adhesion efficiency in structural bonding. Here, a novel EP nanocomposite adhesive-based SiO2-nanoscale ionic materials (SiO2-NIMs) with excellent adhesives strength, transparency, thermal stability, and mechanical properties was prepared via a solvent-free process. To prepare SiO2-NIMs, the sulfonated-SiO2 nanoparticles (SiO2-SO3H) were ionically tethered as a core-corona with Jeffamine-ED-2003 chains as a canopy. Then, SiO2-NIMs/EP nanocomposites with various SiO2-NIMs contents were fabricated. We demonstrate that SiO2-NIMs as high-performance additives, unlike conventional additives, via an exclusive mechanism can simultaneously improve interfacial bond strength, stiffness, and toughness of EP adhesive. The RMS and DMTA tests averred the liquid-like SiO2-NIMs played a magnificent multi-functional role that acts as nonvolatile solvents, reinforcing-agent particles, and toughening agents, causing improved shear strength and resistance to crack growth of epoxy adhesives. The core-corona-canopy parts of SiO2-NIMs make hydrogen bonds and ionic-electrostatic interactions between the adhesive and adherent layers. The single lap shear under different temperatures, TGA, tensile, and SEM tests were applied to investigate adhesion strength, thermal and mechanical properties, and fracture surface morphology of EP adhesives, respectively. For example, the 5 phr SiO2-NIMs/EP showed increased lap shear strength at RT, tensile toughness, tensile strength, stiffness, elongation% and char-yield% by 54%, 240%, 92%, 36%, 91%, and 50% compared to neat EP, respectively. This study introduces SiO2-NIMs as promising additives for high-performance EP adhesives.