Abstract:
: IR spectra of two series of polyether poly(urethaneureas) based on 2,4-toluene diisocyanate, ethylenediamine, and either 1000 or 2000 molecular weight poly(tetramethy1ene oxide) were examined first to elucidate the state of the hydrogen bonding in the hard segment domain and at the interface between the domains and the soft segment phase. In both series, IR analysis suggests the presence of three-dimensional hydrogen bonding within their hard segment domains, where one urea carbonyl oxygen is bonded to two NH groups. The interface between domain and the soft segment matrix is quite sharp since most of the urethane carbonyl is free from bonding. Mechanical properties, specifically stress-strain behavior, hysteresis, and stress relaxation, are reported in this study to demonstrate the consequences of improved phase segregation and domain structure and to differentiate the morphologies of the two series. At the same urea content (30%), the domain in the PTMO 1000 sample is more interconnected than that in the PTMO 2000 sample, and, also, the soft segment phase of the former contains more solubilized hard segment than that of the latter. The PTMO 2000 sample, which has a better phase segregation than the PTMO 1000 sample, exhibits better mechanical properties, such as higher elongation at break, greater toughness, lower hysteresis, and a slower rate of stress relaxation, even though ultimate tensile strength is slightly lower.