Pa. Gunatillake et al., POLYURETHANE ELASTOMERS WITH LOW MODULUS AND HARDNESS BASED ON NOVEL COPOLYETHER MACRODIOLS, Journal of applied polymer science, 63(10), 1997, pp. 1373-1384
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.