Pm. Mehl et Fg. Shi, THERMODYNAMIC STRENGTH OF THE GLASSY STATE AND THE MAXIMUM ENTHALPY STORED IN THE PROPYLENE GLYCOL-D2O SYSTEM, Thermochimica acta, 280, 1996, pp. 501-509
The glassy state of several concentrations of propylene glycol in D2O
is presently characterized by enthalpy relaxation experiments. The exi
stence of a lowest glass transition temperature T-s has defined an utm
ost excess enthalpy that can be stored by the glass during cooling. Si
milar to the thermal behavior of the shear viscosity for liquids, thes
e T-s values are maximum for the binary system with compositions in th
e range 78-82% (w/w) propylene glycol in D2O, suggesting that these co
ncentrations correspond to the strongest glasses, and provide a higher
thermodynamic strength for these glasses. These glasses correspond al
so to the maximum excess enthalpy that can be stored by the glassy sta
te during cooling. These concentrations present, however, an apparent
minimum threshold stress to induce fracture nucleation in the glasses
with the definition of a maximum mechanical fragility. The present res
ults underline a problem in the definition of the thermodynamic and me
chanical strength of the glassy state as an extension of the fragility
definition for liquids.