Structure-property relations in non-linear, segmented copolyureas formed by reaction injection moulding, RIM

Segmented copolyureas have been formed by RIM using a MDI-based polyisocyanate (RMA400) and mixtures of a polyether triamine (Jeffamine T5000) and diethyltoluene diamine (DETDA) chain extender. Hard segment (HS) content was varied between 35 and 65% w/w at a constant overall stoichiometric ratio of -NCO to -NH2 groups of 1.03. All the copolyureas were translucent and DSC confirmed their totally amorphous structure. The copolyureas were shown by dynamic mechanical-thermal analysis to possess a two-phase morphology comprising polyether soft segments of constant Tgs of -40°C and aromatic polyurea hard segments with TgH increasing from 215 to 236°C as HS content increased. The ratio of flexural moduli at -35 and 65°C, decreased from 4.9 to 2.2 at 65% HS, and mechanical integrity was retained at temperatures in excess of 250°C, with flexural moduli of 10MPa at 270°C. Tensile stress-strain studies showed the polyureas to range from semi-rigid elastomers to stiff plastics with moduli greater than IGPa. Postcuring significantly improves materials toughness at high HS contents. © 1987 Springer-Verlag.