A. Hensel et C. Schick, TEMPERATURE CALIBRATION OF TEMPERATURE-MODULATED DIFFERENTIAL SCANNING CALORIMETERS, Thermochimica acta, 305, 1997, pp. 229-237
Calibration of differential scanning calorimeters (DSC) is essential b
ecause it is not possible to calculate heat-how rate and sample temper
ature directly from the quantities measured. The question arises wheth
er the calibration used in the conventional DSC mode is also valid for
temperature-modulated DSC (TMDSC). To prove this, a well-defined tran
sition is needed which does not disturb the temperature profile within
the sample during the modulation, the response of the whole system (c
alorimeter, sample, transition) must be linear. Some low-energy liquid
-crystal transitions behave in this way under certain conditions and c
an be used for temperature calibration in TMDSC. The procedure is demo
nstrated for a smectic-A-nematic transition in a cyanobiphenyl liquid
crystal (80CB). Limitations of the method are discussed - in particula
r, rate effects. The TMDSC measurements also give some information abo
ut the order of phase transitions (80CB:SN - second-order; NI - first-
order). (C) 1997 Elsevier Science B.V.