POLYURETHANE ELASTOMERS WITH LOW MODULUS AND HARDNESS BASED ON NOVEL COPOLYETHER MACRODIOLS

A series of copolyether macrodiols was prepared from either 1,10-decan ediol or 1,6-hexanediol, by acid-catalyzed condensation polymerization using several comonomers to investigate the effect of copolymerizatio n on reducing macrodiol crystallinity. The comonomers used to disrupt crystallinity included 2,2-diethyl-1,3-propanediol, 1,4-cyclohexanedim ethanol, and 1,7-heptanediol. The product copolyethers were identified as hydroxy terminated copoly(alkylene oxides) by H-1- and C-13-NMR sp ectroscopy. Based on NMR results, the structures of the copolyethers w ere established as consisting of blocks of the principal monomer with comonomer 2,2-diethyl-1,3-propanediol incorporated to form only the en d structural unit, whereas 1,4-cyclohexanedimethanol incorporated to f orm the end unit as well as part of the main chain. DSC results confir med that the copolymerization produced macrodiols with lower crystalli nity and lower T-g than those of the corresponding homopolyethers of t he principal monomers, with two exceptions. The exceptions were 1,6-he xanediol/1,10-decanediol, and 1,10-decanediol/1,7-heptanediol copolyet hers where no reduction in crystallinity was observed. A series of pol yurethane elastomers with a constant hard segment percentage (40 wt %) was prepared using 4,4'-methylenediphenyl diisocyanate and 1,4-butane diol as the hard segment. Tensile test results and Shore hardness meas urements demonstrated that copolyether macrodiols produced several pol yurethanes with lower modulus and hardness than those of polyurethanes based on homopolyethers of the principal monomers. Of the comonomers studied, 2,2-diethyl-1,3-propanediol-based copolyether produced the po lyurethane with the lowest hardness and modulus. (C) 1997 John Wiley & Sons, Inc.