Studies on the phase separation of polyetherimide-modified epoxy resin .1. Effect of curing rate on the phase structure

The effect of the curing rate on the phase structure of a new polyetherimide-modified epoxy systems was studied. Through changing cure agents and cure temperature, selecting different molecular weights and end groups of the polyetherimide (PEI) polymers, the curing rates, the phase separation processes and the morphology of the cured blends were observed employing differential scanning calorimetry, time-resolved light scattering and scanning electron microscopy. The highly active cure agent 4,4'-oxydianiline leads to phase separation in the early stage of spinodal decomposition and to a co-continuous phase structure. As to the 4,4'-diaminodiphenyl sulfone cured systems, not only the curing rate, but the mobility of the PEI molecule also affected the final morphology of the PEI-modified epoxy resin.