Viscosity and shear response at the dynamic glass transition of glycerol

Viscosity measurements in a broad temperature range display a variation ove r 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, di vided by temperature, decreases by a factor of 3.5 while viscosity varies b y seven orders of magnitude. Dynamic shear measurements on glycerol are rep orted for the temperature of T=192.5 K. The shape of the shear dispersion i n the alpha relaxation zone was fitted with Havriliak-Negami and stretched exponential functions. The shape parameters show considerable differences b etween different relaxation methods. No indications of a separate (beta) se condary relaxation were found below the glass temperature T-g. (C) 2000 Ame rican Institute of Physics. [S0021-9606(00)50944-1].