Nanosilica-toughened polymer adhesives

• Adhesive bonding becomes increasingly more important in industries.
• Nanocomposite have potential as high performance adhesives.
• Transferring the toughening effect of bulk resins into thin-film adhesives.

High-performance adhesives are of great importance to achieving strong and durable adhesive bonds in a wide range of applications. This article presents an investigation of the use of nano-sized silica particles to improve the fracture toughness of polymer adhesives, focusing on the effects of particle size, matrix ductility and adhesive thickness. The results reveal that the performance of nano-silica as a toughening additive depends strongly on the matrix’s ductility and adhesive thickness. With merely 2.1 vol% nano-silica, the fracture toughness of an epoxy has been improved from 0.19 to 1.34 kJ/m2, representing a 605% improvement. Microscopy studies show that this improvement is attributed to the formation of a dilatation zone, approximately 2–3 μm thick, which dissipates energy. The nanoparticles in general produce a higher adhesive toughening effect than their micron-sized peers. A significant toughening effect has been made by dispersing the nanoparticles in a relative ductile matrix, while such an effect was not observed for the micro-sized particles.