Glass Transition Temperature
Started by Lauren Hartle, Fall 2011.
The glass transition temperature, <math>T_g</math>, is the temperature at which an amorphous solid transitions continuously into a liquid state, and vice versa. This temperature depends on the material and the cooling rate; altering the cooling rate changes the timescale on which atoms and molecules must rearrange to reach their equilibrium configuration. Depending on the cooling rate, the resulting amorphous structure can change. For most materials, the glass transition temperature is fairly well-defined and only weakly cooling rate-dependent.
There are several quantitative definitions of this temperature, detailed by Debenedetti and Stillinger :
1. In a plot of volume versus temperature, the intersection of the liquid and glass curves marks <math>T_g</math>. Figure 1 , shows this phenomenon.
2. Temperature at which the material viscosity reaches <math> 10^[13}</math> poise.
 Debenedetti and F. H. Stillinger. "Supercooled liquids and the glass transition". Nature, Vol 410, 8 March 2001.