Is It not Time to Go back to Tamman’s Tg?

Аннотация

Based on the analysis of numerous experimental data, it is shown that the currently generally accepted glass transition temperature T_g is not correct. It was the result of borrowing from G. Tamman the symbol T_g, which corresponds to the temperature at which a liquid in a viscous flow is transformed into a solid brittle glassy state, and using it instead of the symbol Tw. The latter corresponded to the bending temperature (for Tamman) on the property–temperature curve of glass-forming substances lying above Tamman’s T_g. The disclosed physico-chemical nature of the temperature curve Tw (currently, generally taken to be T_g), which is the temperature of the reverse direction of the interconversion of nanofragment patterns (of polymorphs) of the high- and low-temperature polymorphs that coexist in a vitreous substance, is based on the application of polymer-polymorphing representations of the structure of glass-forming substances. In the past few decades, the discovery of the preendothermal effect located, just as Tamman’s T_g, below the standard T_g, confirms the correctness of Tamman’s T_g characterized by the increased specific heat of the heated glass.