Viscosity and shear response at the dynamic glass transition of glycerol

Abstract

Viscosity measurements in a broad temperature range display a variation over 11 orders of magnitude and show a crossover at about T+=285 K, comparable with dielectric results from a Stickel evaluation. The index R, i.e., the product of dielectric loss peak maximum frequencies times the viscosity, divided by temperature, decreases by a factor of 3.5 while viscosity varies by seven orders of magnitude. Dynamic shear measurements on glycerol are reported for the temperature of T=192.5 K. The shape of the shear dispersion in the α relaxation zone was fitted with Havriliak–Negami and stretched exponential functions. The shape parameters show considerable differences between different relaxation methods. No indications of a separate (β) secondary relaxation were found below the glass temperature Tg.