Nanotailoring of epoxy adhesives by polyhedral-oligomeric-sil-sesquioxanes (POSS)

The development and commercialization of nanoparticles such as nanoclays, carbon nanotubes and polyhedral-oligomeric-sil-sesquioxanes (POSS) offer new possibilities to tailor adhesives in the nanoscale range. Due to the large surface area of the nanosized particles, only small amounts are needed to cause significant changes in properties of adhesives. Properties affected include shear and peel strengths, thermal characteristics, etc. mental results showed that only small amounts of POSS (<5 wt%) were needed to enhance the shear strength of epoxy adhesives and double the peel strength compared with that of the neat epoxy adhesive. The glass transition temperature was increased significantly when the POSS moiety contained reactive groups. In all cases, the increase in properties was obtained at low concentrations of POSS. Above the optimal concentration of POSS, the properties decreased. The mechanical and thermal results were complemented with atomic force microscopy (AFM) characterization of the fracture surfaces of the POSS/epoxy adhesives. AFM results indicated that the surface roughness changed with concentration of POSS. At low levels of POSS, the typical roughness was low and the roughness increased with concentration of POSS. The results led to the conclusion that incorporation of tailored POSS particles in adhesives could improve structural adhesives and composite matrices.