Calorimetric Study of Kinetic Glass Transition in Various Glasses

Differential scanning calorimetry (DSC) experiments were carried out for metallic, ionic, and polymer glasses below and above the glass transition temperature T-g. The values of T-g were determined from the DSC curves. A wide range of heating rate, q = dT/dt = 0.1-100 K/min, was adopted and the q dependence of the apparent value of T-g was investigated. As q was decreased, the value of T-g decreased rapidly, then more slowly, and approached a constant value at low q. The experimental result of this kinetic glass transition was analyzed, where the relaxation time of the transition was considered to be equal to a characteristic observation time of the process of the experiment. The Arrhenius and Vogel-Tammann-Fulcher relaxation-time forms were adopted. The latter form was found to be adequate for explaining the experimental results, and the parameters in the form were determined for various glasses. On the basis of these experimental results the characteristics of the relaxation near the glass transition were precisely discussed.