Abstract
AbstractTwo series of polyurethanes (PUs) were synthesized from a low molecular weight diol - 4,4’-bis(6-hydroxyhexoxy)biphenyl (BH6), a high molecular weight diol - poly(1,6-hexylene adipate)diol (PHA) and 4,4’-methylenebis (cyclohexyl isocyanate) (HMDI) using two fractions of different trans,trans isomer content (uT), respectively: 16%, 46%. The effect of low molecular diol content (uB) in the total mass of the diols used for synthesis on properties of PUs was investigated by DSC, DTA, TGA, polarization microscopy, WAXS, DMTA and tensile testing. For segmented PUs microphase separation is observed and melting temperatures of hard segment (HS) microphases are almost constant within the series for uB≥ 40%. The growth of hard segment content (uHS) induces rectilinear growth of crystallization enthalpy of HS microphases. PUs of uT= 46% show birefringence of HS microphases at uBB ≥ 40%. Glass transition temperatures of HS microphases shift towards lower values with a decrease of uB. PUs of u B = 80 and 100% are stiff, for 20 - 60% elastomeric properties are observed, and in absence of low molecular diol moieties (uB= 0%) plastic behaviour is shown when stretched. Phase inversion is observed between u B BB = 60 and 80%. Thermal stability of PUs (by TGA and DTA) does not depend on uBand uT.
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