The influence of heat transfer on temperature-modulated DSC measurements

The calibration functions of amplitude and phase lag of the dynamic heat-flow rate of temperature-modulated DSC are investigated by model calculations. The results are experimentally verified for sapphire and polystyrene. The calibration functions depend on the sample as well as the heat-transport conditions on the sample holder. At low frequencies, these functions are constant. However, for calibration in the entire frequency range, the knowledge of these functions is necessary. The frequency dependence of phase lag and amplitude are investigated. The calibration functions are determined by the actual heat-transfer parameter. Using the presented model, this parameter can be evaluated from phase-lag information and can be used for the amplitude calibration. (C) 1997 Elsevier Science B.V.