New insight into relaxation dynamics of an epoxy/hydroxy functionalized polybutadiene from dielectric and mechanical spectroscopy studies

Abstract

Dielectric and mechanical spectroscopy methods have been employed to describe the temperature dependencies of the segmental and macromolecular relaxation rates in epoxy/hydroxy functionalized polybutadiene. Dielectric studies on the dynamics of segments of the polymer as well as the mobility of small ions trapped in the system have been carried out both as a function of temperature and pressure under isobaric and isothermal conditions, respectively.

Rethinking the Analysis of the Linear Viscoelastic Behavior of an Epoxy Polymer near and above the Glass Transition

“…The relaxation map for the epoxy resin shown in Figure suggests a different picture of the overall viscoelastic and dielectric relaxation processes than is typically assumed by the community. First, there is a smooth transition between the various relaxation processes relative to the assumption that there are discrete processes associated with α+, α, and the excess wing. , Second, none of the relaxation times exhibits an Arrhenian temperature dependence, which is not surprising in the α+ and α regions, but the excess wing is typically assigned an Arrhenian temperature dependence, ,− although there are contradictory reports. , In a subsequent publication, we will continue the relaxation map to include lower-temperature isotherms where the γ process is dominant, where again there is a smooth evolution of the individual relaxation times versus a collection of individual processes. This suggest a different perspective on relaxation in amorphous materials where looking for molecular relaxation events/processes giving rise to distinct peaks/shoulders in the viscoelastic and dielectric response may not be consistent with the smooth evolution of the relaxation map as shown in Figure .…”