Phase morphology and mechanical properties of a poly(ether sulfone)-modified bismaleimide resin

The polymerization-induced phase-separation behavior of a thermoplastic [poly(ether sulfone) (PES)]-modified thermosetting bismaleimide resin during isothermal curing was investigated with differential scanning calorimetry, time-resolved light scattering, and scanning electron microscopy with various contents and molecular weights of PES. The results suggested that the phase structure changed from a dispersed structure to a bicontinuous structure to phase inversion with an increase in the PES content. Three kinds of PES with different molecular weights were used to study the effects of the molecular weight on the phase structure and mechanical properties of modified systems. With higher molecular weight PES, a phase-inversion morphology could be obtained at lower PES contents. The curing conversion of bismaleimide was affected by the composition of the blend. The curing rate decreased with an increase in the PES content. A blend with 15 wt % PES of a suitable molecular weight had a higher tensile strength and elongation at break than that without PES. (c) 2007 Wiley Periodicals, Inc.