Improving the fracture toughness of epoxy with nanosilica-rubber core-shell nanoparticles

Nanocomposites from epoxy and nanosilica-rubber core–shell nanoparticles were fabricated. The soft shell was a copolymer synthesized from caprolactone and meso-lactide and was designed compatible with the cured epoxy system. The core–shell nanoparticles achieved a reasonably good dispersion in the matrix with minor aggregations. With the addition of the nanosilica based core–shell nanoparticles, the Young's modulus, maximum strength, and fracture toughness of the epoxy were all improved. The impact strength of the epoxy was improved by 39.4% with a loading of 2.0wt% nanofillers. The glass transition temperature of the epoxy was slightly decreased with the addition of nanofillers. The toughening mechanisms were investigated with the use of small angle X-ray scattering together with morphological observations. It was confirmed that crazing, microcracks formation and debonding of nanoparticles from the matrix were the main causes leading to the improvement of fracture toughness.