Viscosity Activation Energy

The standard procedure of determining the activation energy for shear viscosity from the slope "L" of the Arrhenius plot, lgn against 1/T leads frequently to overestimated values. The article discusses the significance of "L" & shows that important information can be retrieved from its value as the fragility parameter can be formulated as a=0.00Lg/Tg. Fragility parameter a=1 is an indication for a strong glass with constant activation energy. It is demonstrated that the average jump frquency model describes fairly the dependence of viscosity on chemical composition. However, models based on mean activation energy considerations fail completely.