Premium
Morphological changes in segmented polyurethane elastomers by varying the NCO/OH ratio
Author(s) -
Spathis G.,
Niaounakis M.,
Kontou E.,
Apekis L.,
Pissis P.,
Christodoulides C.
Publication year - 1994
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.1994.070540701
Subject(s) - differential scanning calorimetry , fourier transform infrared spectroscopy , elastomer , polymer chemistry , polyurethane , hydrogen bond , polymerization , thermoplastic elastomer , phase (matter) , materials science , isothermal process , chemistry , analytical chemistry (journal) , chemical engineering , molecule , polymer , composite material , copolymer , thermodynamics , organic chemistry , physics , engineering
The morphological changes induced to segmented polyurethane elastomers by varying the NCO/OH ratio during the second step of polymerization, while keeping constant the total hard‐segment content (∼ 30%), were studied by means of fourier transform infared spectroscopy (FTIR), differential scanning calorimetry (DSC), and the thermally stimulated depolarization current method (TSDC). The DSC results gave evidence for the existence of phase separation in thermoplastic polyurethanes, whereas the elastomerc ones appeared to form a more homogeneous network. The FTIR results gave additional evidence regarding phase separation be detecting the sterength of the hydrogen bonds. Moreover, an attempt was made to assess the relative contribution made to the hydrogen bonding in such systems by the two potential acceptors: ester and urethane carbonyls. The TSDC results gave a relaxation mechnism that is due to interfacial (Maxwell–Wagner–Sillars) polarization, providing evidence of the existence of an interfacial phase. The introduced secondary chemical cross‐links was found to affect mainly the irregularly packed hard domains and to form a more homegeneous network at higher values of the NCO/OH ratio. © 1994 John Wiley & Sons, Inc.