EFFECT OF SOFT-SEGMENT CH2 O RATIO ON MORPHOLOGY AND PROPERTIES OF A SERIES OF POLYURETHANE ELASTOMERS/

A series of six thermoplastic polyurethane elastomers were synthesized from a 4,4'-methylene diphenyl diisocyanate (MDI) and 1,4-butanediol (BDO) chain extender, with poly(ethylene oxide) (PEO), poly(tetramethy lene oxide) (PTMO), poly(hexamethylene oxide) (PHMO), poly(octamethyle ne oxide) (POMO), poly(decamethylene oxide) (PDMO), and poly(1,6-hexyl carbonate)diol (PCDO) macrodiol soft segments. The soft-segment molec ular weights employed were similar (approximately 1000 g/mol) and each polyurethane contained 55% (w/w) of the soft-segment macrodiol. Diffe rential scanning calorimetry (DSC), dynamic mechanical thermal analysi s (DMTA), wide-angle X-ray diffraction (WAXD), and Fourier transform i nfrared spectroscopy (FTIR) techniques were employed to characterize t he morphology. Tensile and Shore hardness tests were also performed. M aterials were tested in the as-molded, solvent-cast, and annealed stat es. It was found that the polyurethanes produced from macrodiols with the highest CH2/O ratio displayed greater hard-domain crystallinity, a higher degree of phase separation, and the greatest hardness, stiffne ss, and opacity. POMO- and PDMO-based polymers displayed evidence of p aracrystallinity in the soft domains. The PCDO-based material displaye d a higher degree of phase mixing compared to the polyether-based mate rials. Annealing increased hard-domain crystallinity in all the polyet her-based materials. The solvent-cast POMO- and PDMO-based materials h ad poor mechanical properties and were difficult to cast. The material s containing macrodiols with the lowest CH2/O ratio were more readily solvent-cast and produced strong, useful films. Morphologies of the so lvent-cast materials differed greatly from those of the molded materia ls. (C) 1996 John Wiley & Sons, Inc.