Abstract: The series of RIM(reaction injection molding) polyurethaneureas(PUU) based on urethane-modified 4, 4'-diphenylmethane diisocyante, 2000 molecular weight ethylene oxide endcapped poly(propylene oxide) polyether, and either diethyltoluene diamine(DETDA) or 4, 4'-diphenylmethane diamine(MDA) were synthesized.The effect of hard segment structure and concentration on microphase separation has been studied by DSC.In this study, it is emphasized that polymerization kinetics plays an important role in the formation of phase structure in RIM PUU.The DSCresults show that the extent of microphase separation decreases with the increase of hard segment concentration.Aseries of RIM PUUin which MDAis used as extender has the nature of faster overall rate of polymerization and weaker driving force for microphase separation, and the series of RIM PUUshows lower extent of microphase separation under the condition that reaction rate of hard segment formation is faster than that of soft segment formation in this paper.Non-equilibrium morphology is formed because of very fast overall rate of polymerization and the strong hydrogen bonding between hard segments.The increase of overall rate of polymerization corresponds to the decrease of driving force for microphase separation.Much further research is needed to clarify the nature of endothermic behavior from room temperature to about 200℃ in RIM PUU.

Key words: Reaction injection molding(RIM), Polyurethaneurea, Microphase separation, Polymerization kinetics