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

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.