The effects of hard segment content on microphase separation and physical properties of non-linear,segmented copolyureas formed by RIM

Summary The properties of RIM-copolyureas formed from a polyether triamine and containing 30 to 70% by weight of MDI/DETDA hard segments (HS) were investigated. As-moulded (mould temperature 115°C) and postcured (200°C/1h) materials were compared using DSC, DMTA and tensile stress-strain measurements. Phase separation ratios (PSR) of as-moulded materials increased from 47 to 56% with increasing HS content. Postcuring increased PSR to 70% for all materials resulting in significant intensification of HS glass transition at Tg^H (220 to 250°C), and reduced mechanical damping and modulus-temperature dependence between –40 and 200°C. Agreement between experimental tensile moduli and those predicted by appropriate two-phase composite theory has confirmed the co-continuous morphology of these RIM-copolyureas over the entire composition range studied.