Abstract
The procedure for the calibration of differential scanning calorimeters (DSC) has been addressed by several authors. Most of the work published on this subject dealt mainly with the calibration on heating. For calibration on cooling, Menczel and Leslie suggested the use of thermally stable liquid crystals, for which the isotropic to nematic or cholesteric to isotropic transitions do not exhibit hysteresis on cooling. In this work, a new method is proposed to calibrate differential scanning calorimeters on cooling. It is suggested that the calibration on heating, with standard metals, may also be used to perform the calibration on cooling. The onset of the nematic to isotropic transition on heating (and vice-versa on cooling) will be used to support the method and to quantify the errors, which are of similar magnitude to those obtained by Menczel and Leslie with thermally stable high purity liquid crystals. Results of the change in the indium and lead crystallisation onset temperatures with the cooling rate are presented. Using as an example the non-isothermal crystallisation of polyethylene, the errors obtained with the standard calibration of the DSC and the new calibration on cooling are discussed.
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