| Abstract: | Phase-separation behavior of aromatic amine-cured diglycidyl ether of bisphenol-A (DGEBA) epoxy oligomer and poly(ether imide) (PEI) engineering thermoplastic-modifier mixtures was investigated by means of small-angle light scattering (SALS) and optical microscopy. The starting reactant mixtures comprising epoxy, PEI, and the curing agents, namely diamino diphenyl sulfone (DDS) and methylene dianiline (MDA), were found to be single phase. During curing, phase separation occurred in the epoxy/PEI/DDS system, whereas no phase separation took place in MDA-cured epoxy/PEI blends. The difference between the two systems has been attributed to thermodynamic and kinetic aspects of cure reaction in thermoplastic-modified thermosetting (TMT) polymeric blends. Spinodal decomposition as characterized by an increase of scattered intensity, shift of the peak angle to a smaller scattering angle, and development of a regularly phase-separated structure followed by coarsening was found to be the dominant mechanism of reaction-induced phase separation in DDS-cured epoxy/PEI blend compositions. |
