Studies on the phase separation of polyetherimide-modified epoxy resin, 2") Effect of molecular weight of PEI on the structure formation

The effect of molecular weight on the structure formation of polyetherimide modified epoxy system was studied. Using time-resolved light scattering (TRLS) and scanning electron microscopy (SEM), the process of phase separation and the morphology of the blends were investigated. As the curing reaction proceeds, the phase separation occurs first in the large molecular weight polyetherimide (PEI) modified epoxy resin and the time of occurrence of phase separation is increased with the decrease of the inherent viscosity of PEI. Because of the different viscosity of the blends, the blends display varied morphologies from a PEI particle dispersion to co-continuous phases. Changing of the PEI molecular weight may be another possible route to control the morphology of the PEI modified epoxy resins.