Rubber‐modified epoxies. I. Transitions and morphology

A variety of different morphologies, and therefore mechanical properties, can be obtained from a single rubber‐modified epoxy formulation. The volume fraction, domain size, and the number of particles of phase‐separated rubber are determined by the competing effects of incompatibility, rate of nucleation and domain growth, and the quenching of morphological development by gelation. These factors can be varied by the butadience/acrylonitrile ratio of the reactive rubber, the temperature of cure, and the gelation time. These ideas have been exploited to control the development of morphology of these amorphous systems. Phase separation was investigated by electron microscopy, viscometry, and dynamic mechanical analysis.