The Effect of Silica Nanoparticles and Carbon Nanotubes on the Toughness of a Thermosetting Epoxy Polymer

Silica nanoparticles and multiwalled carbon nanotubes (MWCNTs) have been incorporated into an anhydride-cured epoxy resin to form "hybrid'' nanocomposites. A good dispersion of the silica nanoparticles was found to occur, even at relatively high concentrations of the nanoparticles. However, in contrast, the MWCNTs were not so well dispersed but relatively agglomerated. The glass transition temperature of the epoxy polymer was 145 degrees C and was not significantly affected by the addition of the silica nanoparticles or the MWCNTs. The Young's modulus was increased by the addition of the silica nanoparticles, but the addition of up to 0.18 wt % MWCNTs had no further significant effect. The addition of both MWCNTs and silica nanoparticles led to a significant improvement in the fracture toughness of these polymeric nanocomposites. For example, the fracture toughness was increased from 0.69 MPam(1/2) for the unmodified epoxy polymer to 1.03 MPam(1/2) for the hybrid nanocomposite containing both 0.18 wt % MWCNTs and 6.0 wt % silica nanoparticles; the fracture energy was also increased from 133 to 204 J/m(2). The mechanisms responsible for the enhancements in the measured toughness were identified by observing the fracture surfaces using field-emission gun scanning electron microscopy. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 119:2135-2142, 2011