STRUCTURE AND THERMAL-PROPERTIES OF POLYETHER POLYURETHANEUREA ELASTOMERS

Three series of polyether polyurethaneurea (PEUU) elastomers based on poly(tetramethylene glycol) (PTMG, MW = 1000 or 2000), 4,4'-diphenylmethane diisocyanate (MDI), and three kinds of diamine chain extenders, i.e., 4,4'-diaminodiphenylmethane (DAM), m-phenylenediamine (MPD), and p-phenylenediamine (PPD) were synthesized in dimethylformamide or DMF-LiCl solvent by the prepolymer method. The degree of phase separation was higher in the samples with PTMG-2000 than in those with PTMG-1000. Three-dimensional hydrogen bonding between hard segments led to strong hard domain cohesion, but solubilized soft segment and the remaining LiCl within hard domains interfered with microstructural ordering of hard segments. According to the TG/DTA analyses, as-cast PEUU elastomers showed two-stage degradation behavior at a heating rate of 20 degrees C/min in a nitrogen atmosphere. Initial degradation temperature was closely related with both hard-segment content and microstructural ordering, i.e., most of the hard segments were degraded in the first stage and samples with less ordered hard segments degraded at a lower temperatures. (C) 1993 John Wiley & Sons, Inc.