Calculation of smoothing factors for the comparison of DSC results

Complex mixtures of long chain organic compounds often show overlapping glass transition temperatures (T gs) when analyzed by differential scanning calorimetry (DSC) or modulated DSC (MDSC). In such cases, subjective and inconsistent smoothing of data acquired under different conditions can lead to the misinterpretation of results. A quantitative method for the selection of smoothing factors for the analysis and comparison of (M)DSC results is presented. The method is most useful for the analysis of the derivative of the heat capacity, dC p/dt or dC p/dT, plots which best highlight overlapping T gs. Four equations are shown to relate the heating rate and the smoothing factor. The equations allow a comparison of data acquired i) at different heating rates and plotted vs. temperature, ii) at a single heating rate and plotted vs. both time and temperature, i.e., dC p/dt vs. dC p/dT, iii) at different heating rates and plotted vs. both time and temperature, and iv) at different heating rates, and shown exclusively in the time domain. Examples of the use of the equations are provided for the analysis of bitumen, a complex mixture of natural origin.