Determination of the glass transition temperature

The definition of the glass transition temperature, T _g, is recalled and its experimental determination by various techniques is reviewed. The diversity of values of T _g obtained by the different methods is discussed, with particular attention being paid to Differential Scanning Calorimetry (DSC) and to dynamic techniques such as Dynamic Mechanical Thermal Analysis (DMTA) and Temperature Modulated DSC (TMDSC). This last technique, TMDSC, in particular, is considered in respect of ways in which the heterogeneity of the glass transformation process can be quantified.