Authors:K. Ishikiriyama, A. Boller, and B. Wunderlich
The melting and crystallization of a sharply melting standard has been explored for the calibration of temperature-modulated
differential scanning calorimetry, TMDSC. Modulated temperature and heat flow have been followed during melting and crystallization
of indium. It is observed that indium does not supercool as long as crystal nuclei remain in the sample when analyzing quasi-isothermally
with a small modulation amplitude. For standard differential scanning calorimetry, DSC, the melting and crystallization temperatures
of indium are sufficiently different not to permit its use for calibration on cooling, unless special analysis modes are applied.
For TMDSC with an underlying heating rate of 0.2 K min−1 and a modulation amplitude of 0.5–1.5 K at periods of 30–90 s, the extrapolated onsets of melting and freezing were within
0.1 K of the known melting temperature of indium. Further work is needed to separate the effects originating from loss of
steady state between sample and sensor on the one hand and from supercooling on the other.
question arose, “Is there a better method?”
A literature check uncovered no previous work using temperaturemodulateddifferentialscanningcalorimetry (TMDSC) for phosphorous pentasulfide free sulfur measurement. We therefore investigated if this
Temperature-modulateddifferentialscanningcalorimetry (TMDSC) developed by Reading et al. [ 1 ] was commercialized shortly afterward and is being widely applied in different fields such as material research
Authors:Eiji Hashimoto, Yuichi Seshimo, Keita Sasanuma, Yuichiro Aoki, Hitoshi Kanazawa, Yuji Ike, and Seiji Kojima
The fragility of ethylene glycol and glucose aqueous solution systems has been investigated by temperature-modulated differential
scanning calorimetry (TMDSC). The frequency and temperature dependences of complex specific heat have been observed in the
vicinity of a glass-transition temperature Tg. It is shown that the value of the fragility index m can be determined from the temperature dependence of the α-relaxation times observed by TMDSC. We have also studied the elastic
properties of these aqueous solutions by micro-Brillouin scattering, and determined these relaxation times of elastic properties
in the gigahertz range.
The increment of heat capacity at the glass transition for semi-crystalline poly(ethylene terephthalate) (PET) observed by
temperature-modulated differential scanning calorimetry (TMDSC) shows significant deviations from a simple crystalline/amorphous
two-phase model. Introduction of a rigid amorphous fraction, which is non-crystalline but which also does not participate
in the normal glass transition, allows a much better description of the transition behaviour in semi-crystalline PET. Certain
questions arise such as what is the rigid amorphous fraction and over what temperature range do these rigid amorphous segments
devitrify? These TMDSC results show that the rigid amorphous component may be treated as an interphase between amorphous and
crystalline phases. This interphase does not exhibit a separate glass transition temperature at temperatures above the normal
Tg. The suggestion is made that the glass transition of the rigid amorphous component occurs continually between the glass transition
temperature of the amorphous phase and up to about 135C for this particular sample of PET.
The quality of measurement of heat capacity by differential scanning calorimetry (DSC) is based on strict symmetry of the
twin calorimeter. This symmetry is of particular importance for temperature-modulated DSC (TMDSC) since positive and negative
deviations from symmetry cannot be distinguished in the most popular analysis methods. The heat capacities for sapphire-filled
and empty aluminum calorimeters (pans) under designed cell imbalance caused by different pan-masses were measured. In addition,
the positive and negative signs of asymmetry have been explored by analyzing the phase-shift between temperature and heat
flow for sapphire and empty runs. The phase shifts change by more than 180° depending on the sign of the asymmetry. Once the
sign of asymmetry is determined, the asymmetry correction for temperature-modulated DSC can be made.