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The thermal analysis of polymers. V. Effects of crosslinking and hard block crystallinity on the mechanical behavior of polyurethane elastomers
Author(s) -
Miller Gerald W.
Publication year - 1971
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.1971.070150104
Subject(s) - elastomer , crystallinity , materials science , thermal expansion , prepolymer , enthalpy of fusion , polyurethane , block (permutation group theory) , polymer , triol , composite material , enthalpy , diol , thermoplastic elastomer , polymer chemistry , thermodynamics , melting point , copolymer , mathematics , geometry , physics
Linear expansion measurements have been used to correlated the degree of molecular ordering of a polyurethane elastomer with the increase in hard block content. The lower the value of the linear coefficient of expansion, α L , the higher the degree of molecular fit. The soft block exerts the major influence on the coefficient of expansion below its fusion temperature (45°C), and the value usually decreases as the hard block content increases. Extenstion with aromatic diols causes the α L to decreases at 100°C as the hard block content increases. Crosslinking a urethane prepolymer with triol increases the expansivity over the diol‐extended elastomer. Keeping the NCO/OH ratio in the range 0.975 to 1.06 causes the lowest coefficient of expansion. For elastomers of low crystallinity, no correlation can be made between hard block content and enthalpy.