High-speed calorimetry

SSA has been typically performed employing a constant sample mass (approximately 10 mg) and various heating rates (5, 10, and 20 C/min) in previous works [41,42]. However, Pijpers et al. [3] introduced high-speed calorimetry concepts... 

Pjpers TFJ, Mathot VBF, Goderis B, et al. High-speed calorimetry for the study of the kinetics of (de)vitrification, crystallization, and melting of macromolecules. Macromolecules 2002 35 3601-3613. 

High-speed calorimetry, as reported by Mathot and co-workers [2], has also proved extremely useful on a number of occasions for identification of very small inclusions. Figure 5.6 shows the melting point of a sample cut out of an extrusion filter. 

Another important technique is the thermal analysis technique of differential scanning calorimetry (DSC). Current high-speed DSC equipment (sometimes also referred to as hyper-DSC) allows for rapid heating (up to 500°C/min) and cooling of (small) samples and therefore an increased rate of analysis per sample... 

The versatility of the DSC method and the high speed of the experiments have costs in terms of accuracy. For example, the best accuracy in the determination of heat capacities of solids by DSC is typically 1% [3,248-250], at least one order of magnitude worse than the accuracy of the corresponding measurements by adiabatic calorimetry [251]. This accuracy loss may, however, be acceptable for many purposes, because DSC experiments are much faster and require much smaller samples than adiabatic calorimetry experiments. In addition, they can be performed at temperatures significantly above ambient, which are outside the normal operating range of most adiabatic calorimeters. 

We have observed such a transition in intact membranes of M. laidlawii which occurs at the same temperature as in the membrane lipids dispersed in water (77). Figure 11 shows representative endothermic transitions of membranes and lipids in water. Membranes were prepared for calorimetry by sedimenting at high speed, then 90-100 mg. of packed pellet were sealed in a stainless steel sample pan. The material was neither dried nor frozen before examination. Total membrane lipids were extracted with chloroform-methanol 2 1 v/v then dried and suspended in water. Lipids from the membranes of cells grown in the usual tryptose medium without added fatty acids are shown in a, while b and c are scans of intact membranes from the same cells. In b the membrane preparation had not been previously exposed to temperatures above 27 °C. The smaller transition at higher temperature probably arises from... 

Finally, significant advances in the techniques of both thermal and thermochemical measurements have come to fruition in the last decade, notably aneroid rotating-bomb calorimetry and automatic adiabatic shield control, so that enhanced calorimetric precision is possible, and the tedium is greatly reduced by high speed digital computation. Non-calorimetric experimental approaches as well as theoretical ones, e.g., calculation of electronic heat capacity contributions to di- and trivalent lanthanides by Dennison and Gschneidner (33), are also adding to definitive thermodynamic functions. 

McGregor, C. Saunders, M.H. Buckton, G. Saklatvala, R.D. The use of high-speed differential scanning calorimetry (Hyper-DSC ) to study the thermal properties of carbamazepine polymorphs. Thermochim. Acta 2004, 417, 231-237. 

At Senboku Works II, we are now using sonic calorimetry to monitor calorific values in LNG at unloading, and use Rauter meters for calorific value control of feed gas our optical interferometer is now undergoing field tests and further development to exploit the method s theoretical advantages in terms of high-speed response, high sensitivity, and simplicity and compactness of the apparatus. 

For this summary, forms of thermal analyses under extreme conditions are described for the measurement of heat and temperature, as dealt within Sects. 4.1-4. The distinction between DTA and DSC seen in these methods is described in Appendix 9. In Appendix 10, DTA or DSC at very low and high temperatures and DTA at very high pressures are mentioned. This is followed by a discussion of high-speed thermal analysis which, in some cases, may simply be thermometry. Finally, micro-calorimetry is treated. One might expect that these techniques will develop in this century [1]. The numbers in brackets link to references at the end of this appendix. 

Vanden Poel, G. and Mathot, V.B.F. (2006) High-speed/high performance differential scanning calorimetry (HPer DSC) Temperature calibration in the heating and cooling mode and minimization of thermal lag. Thermochim. Acta, 446,... 

PieUchowski K, Flejtuch K (2004) Some comments on the melting and recrystaUization of polyoxymethylene by high-speed and StepScan differential scanning calorimetry. PoUmery 49 80-82... 

Saklatvala RD, Saunders MH, Fitzpatrick S, Buckton G. A comparison of high speed differential scanning calorimetry (HyperDSC ) and modulated differential scanning calorimetry to detect the glass transition of polyvinylpyrrolidone the effect of water content and detection sensitivity in powder mixtures (a model formulation). /Drug Deliv Sci Technol 2005 15(4) 257-260. 

A more recent step to speed up DSC was taken in connection with a commercial power-compensation DSC (High Performance DSC) [6] and is now available as HyperDSC from the Perkin-Elmer Inc. It is claimed to reach 500 K min. For a pan of a diameter of 5 mm, the heating rates calculated in Fig. A. 10.1 corresponds to sample masses of 20, 2, and 0.2 mg, showing that it is the heating and cooling capacity of the DSC that limits fast calorimetry, not the properties of the sample. 

Three developments of calorimetry were thus combined in the last decade to dramatically enhance the capabilities of thermal analysis techniques and hence the study of the thermal properties of materials. These were the high precision of conventional adiabatic calorimetry, the speed of operation, and small sample size of DSC and the measurement of frequency dependence of thermal events and thus the MTDSC system evolved. Modulation is perhaps the most significant development with respect to thermal analysis techniques paralleling in significance the Fourier transform development of infrared spectroscopy. 

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