Temperature range of the liquid–glass transition

It has been shown that the currently used method for calculating the temperature range of $\delta T_{g}$ in the glass transition equation $q\tau_{g}=\delta T_{g}$ as the difference $\delta T_{g}=(T_{12}-T_{13})$ results in overestimated values, which is explained by the assumption of a constant activation energy of glass transition in deriving the calculation equation $(T_{12}$–$T_{13}$ are the temperatures corresponding to the logarithmic viscosity values of $\operatorname{lg}\eta$ = 12 and $\operatorname{lg}\eta$ = 13). The methods for the evaluation of $\delta T_{g}$ using the Williams–Landel–Ferry equation and the model of delocalized atoms are considered, the results of which are in satisfactory agreement with the product $q\tau_{g}$ ($q$ is the cooling rate of the melt and $\tau_{g}$ is the structural relaxation time at the glass transition temperature). The calculation of $\tau_{g}$ for inorganic glasses and amorphous organic polymers is proposed.