Abstract
The microstructure and dynamic mechanical properties of segmented polyurethaneurea (SPUU) in concentrated dimethyl acetamide (DMAc) solutions have been investigated by means of small-angle X-ray scattering (SAXS) and viscoelastic measurements, respectively. Kratky plots of SAXS intensity functions indicated the following: (1) Formation of hard segment domains introduced mainly by hydrogen bondings is promoted with increasing ratio of isocyanate to hydroxyl groups ([NCO]/[OH]) and polymer concentration, C p. (2) The degree of completion of the hard segment domains increases with temperature up to 55°C and then gradually decreases by further increase of temperature. An analogy was found between [NCO]/[OH] dependence of the dynamic storage G′( ω) and loss shear moduli G″( ω) for SPUU in DMAc and time dependence of those for a chemically gelling system. G′( ω) and G″( ω) indicated that the properties of SPUU solutions change from sol-like to gel-like with increasing [NCO]/[OH]. By varying [NCO]/[OH], a relationship of G′( ω) ≈ G″( ω) ≈ ω k was observed around [NCO]/[OH] = 1.6. The exponent k is evaluated to be 0.67, which was similar to the literature value obtained at the gelation point. This corresponds to the ‘gelation threshold’ of the chemical gelation process.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
