Epoxy resin was modified by incorporating polysulfone in order to improve the fracture toughness. Morphology gradient was obtained by inserting polysulfone film in epoxy resin and controlling the relative rate of dissolution of polysulfone and the polymerization of epoxy.
The formation of morphology gradient was confirmed by scanning electron microscopy. Homogeneous phase of epoxy/polysulfone, sea(polysulfone)-island(epoxy), nodular, and sea(epoxy)-island(polysulfone) morphology was observed in sequence as the concentration of polysulfone decreased.
The fracture toughness of epoxy/polysulfone having morphology gradient showed KIC value of $1.2 MN/m^1.5$, which was higher than that of epoxy/polysulfone semi-IPN with uniformly distributed morphology.
