Conditions required for heat-capacity measurements using modulated-temperature calorimetry

Modulated-temperature calorimetry, in which the same apparatus as a standar d differential scanning calorimeter is used, is a powerful method for measu ring heat capacities. Precise heat capacity measurements are useful, for ex ample, to analyze anomalous behavior at the glass transition. However, owin g to the periodically-modulated temperature we have to pay attention to: (1 ) the thickness of the sample; (2) the thermal contact resistance between t he sample and the sample pan; and (3) the thermal contact resistance betwee n the sample pan and the base plate of the apparatus. This article will ill ustrate the following. The thickness of a sample should be chosen so as to satisfy uniformly-modulated temperature conditions throughout a sample, and subsequently both thermal contact resistances should be reduced so that th e relaxation times caused by the thermal contact resistances are adequately small in comparison with the period of modulated temperature. (C) 1999 Els evier Science B.V. All rights reserved.