Glass transition temperature its exploitation and new conception of fragility

Relations between the magnitude of the change of the ratios of crystallization and melting temperature with glass transition temperature, that is T-c/T-g and T-m/T-g, determine the order of the values of relative change of glass stability (GS) parameters dK(H)/K-H,dK(w) /K-w and dK(u)/K-u. The linear correlation of new GS parameters F-K and F-KA which include fragility and reduced glass transition temperature with logR(c) is a better correlation of K-u. The stretching exponent increases as a linear function of T/T-g in the interval 1 <= T/T-g<1.1 for given values of the dynamic fragility parameter m. As result, it follows that the kinetic term in fragility can be neglected. The thermodynamic term, which has a dominant role in fragility can be determined by the expressions for configurational entropy and configurational heat capacity. We compared S-c(T) a function of temperature dependence of configurational entropy which was obtained by Sipp et al and S-cVFT(T) a function proposed by Yue. Both S-c(T) and S-cVFT(T) have the same temperature dependence and almost overlap. Therefore, using either S-c(T) or S-cVFT(T) we will get the same value of fragility index. From the dependence of ln S-c(T) versus lnT it is possible to successfully predict the relations between the values of m for different glass formers.