Читать книгу Encyclopedia of Glass Science, Technology, History, and Culture - Группа авторов - Страница 26

For the experimental timescales of the order of a few minutes typical of measurements of macroscopic properties, one observes that, regardless of chemical composition, time‐dependent results begin to be observed when the viscosity becomes higher than about 10¹² Pa. For convenience and comparison purposes, one defines the standard glass‐transition temperature, T_g, as the temperature at which the viscosity of the liquid reaches this value of 10¹² Pa.s.