Temperature modulated differential scanning calorimetry (TMDSC) in the region of phase transitions. Part 1: Theoretical considerations

For temperature modulated differential scanning calorimetry (TMDSC) a simpl e model, the low pass filter, is presented which allows to see and calculat e the influence of heat transfer into the sample on magnitude and phase shi ft of the modulated part of the measured heat flow rate and the heat capaci ty determined from it. A formula is given which enables to correct the meas ured magnitude of the periodic heat flow rate function and the calculated h eat capacity in dependence on the thermal resistance and heat capacity of t he sample. The correction becomes very important in regions where the heat capacity changes considerably as in the melting region. The approach is suc cessfully tested with model substances with well-known excess heat capacity in the transition region. (C) 1999 Elsevier Science B.V. All rights reserv ed.