Abstract
In an attempt to study the specific influence of cross-linking on the α relaxation in polymer networks, a series of model heterocyclic polymer networks (HPN) with well-defined cross-link densities and constant concentration of dipolar units were studied. Model HPN systems were prepared by simultaneous trimerization of 1,6-hexamethylene diisocyanate (HMDI) and hexyl isocyanate (HI). These HPN systems were characterized by dielectric relaxation spectroscopy in the 10−1 Hz<F<105 Hz frequency range and in the 123 K<T<493 K temperature interval. The α relaxation in these systems depends on network density and shifts toward higher temperatures as the cross-link density increases for high HMDI/HI ratios. Discussion of the α-relaxation shape in light of recent models indicates that segmental motions above the glass transition systematically experience a growing hindrance with increasing degree of cross-linking. Description of the temperature dependence of relaxation times according to the strong–fragile scheme clearly shows that fragility increases as polymer network develops.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: 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.