EXPERIMENTAL STUDIES IN PHASE SEPARATION OF REACTION INJECTION MOLDED (RIM) POLYURETHANES.

Very large differences have been found in RIM polyether based urethane depending on whether the reactive mixture is catalyzed or not. Samples catalyzed at levels typical of commercial RIM formulations appear to have more phase mixing in their domains as observed from low crystallinity and broadened relaxation mechanisms. They show better mechanical properties due to high molecular weight and domain connectivity. The phase separation in these systems appear to be controlled by the high speed of the reaction. Samples prepared without catalyst present better phase separation as measured from hard segment crystallinity, flatter rubbery plateau and sharper relaxation mechanisms. Low molecular weight and poor domain connectivity makes these samples mechanically poor. Their morphology appears to have developed from a diffusion controlled reaction.