Differential Thermal Analysis and Differential Scanning Calorimetry
These techniques quantify the energy required, or released, during temperature programmed heating. Originally, differential scanning calorimetry (DSC), invented
Fig. 1 TGA and DTG curves for ATH decomposition in nitrogen at 10 °C min 1
by Perkin-Elmer, was deemed by the International Conference on Thermal Analysis (ICTA) to describe only the technique where a quantifiable amount of energy, as an electric current, was supplied to the sample (or reference) to maintain the sample and reference temperatures equal, now known as power compensation DSC.
In differential thermal analysis (DTA), the temperature of the sample is compared to the temperature of a reference (usually a matching empty crucible) during programmed heating (or cooling). Raw DTA data is recorded as temperature difference (between the sample and reference pans) as a function of temperature. Prior calibration using materials of known heat capacity, such as sapphire disks, together with software converts the temperature difference into energy units, to make the results comparable to power compensation DSC. Thus, calibrated DTA became known as heat flux DSC. Now it is recognized that both techniques provide the same information and are both classed as DSC (Laye 2002). Data is reported as a differential, showing endothermic (heat to sample) or exothermic (heat from sample) processes. DSC provides useful information about the thermal decomposition of both mineral fillers and polymeric materials.