The glass transition temperature versus the fictive temperature

A comparison of the values of the glass transition temperature (T_g) measured on cooling and the limiting fictive temperature measured on heating as a function of cooling rate is performed for a polystyrene sample using both capillary dilatometry and differential scanning calorimetry (DSC). The results from both techniques indicate that is systematically lower than T_g presumably due to the breadth of the relaxation on cooling. The Tool-Narayanaswamy-Moynihan (TNM) model is used to fit the experimental data from dilatometry and DSC in order to ascertain the origins of the higher value of T_g compared to .