Dynamic mechanical analysis of an epoxy/thermoplastic blend: polymerization-induced phase separation

Phase separation behaviour and analysis of the morphologies for a commercial epoxy resin based on tetraglycidyl‐4,4′‐diaminodiphenylmethane (TGDDM) with 4,4′‐diaminodiphenylsulfone (DDS) as hardener and blended with different amounts of poly(styrene‐co‐acrylonitrile) (SAN) thermoplastic, have been studied by dynamic mechanical analysis (DMA) supported by other techniques. In comparison with the neat system, the modified systems reach gelation and vitrification faster. These events have been assigned at the onset and the end of the storage modulus signals E′ in a DMA curve (E′ versus time). The results are explained by a phase‐separation phenomenon induced by polymerization. Scanning electron microscopy (SEM), focused on phase separation, has revealed a sea‐island type of morphology for low thermoplastic contents and an epoxy‐nodular or phase inverted structure for high thermoplastic contents. © 2002 Society of Chemical Industry