A calibration of complex heat capacity obtained by temperature-modulated DSC in the melting region of polymer crystals

Complex heat capacity obtained in melting region of polymer crystals by tem perature-modulated differential scanning calorimetry of heat flux type has been calibrated with a method based on a model proposed by Hatta. The calib ration method corrects for the effect of thermal conductivity of the DSC ap paratus on the magnitude and phase angle of the heat capacity. The validity of the correction has been confirmed by examining the reversible melting a nd crystallization of indium under quasi-isothermal conditions. For the irr eversible melting of polymer crystals analyzed with an additional underlyin g heating rate, the calibrated heat capacity becomes a complex quantity wit h a frequency dependence roughly approximated by Debye's type, the characte ristic time of which depends on the underlying heating rate. This behavior qualitatively agrees with the previous results obtained by the calibration of baseline-subtraction from the phase angle. The applicability of the "bas eline-subtraction" has also been discussed. (C) 2000 Elsevier Science Ltd. All rights reserved.