Differential calorimetric analysis

Figure 2. Differential scanning calorimetric analysis of a cobalt chloride modified BDSDA-ODA polyimide film.

Interest in the use of calorimetry as a routine diagnostic or analysis tool has gained significant momentum only in the last 50 years. This interest has lead to the development of popular procedures such as differential thermal analysis (DTA) and differential scanning calorimetry (DSC). A wide variety of solution calorimetric techniques exist today. These techniques include thermometric titration, injection and flow emhalpimetry. The major growth of commercial instrumentation for calorimetry has occurred to address applications in routine analysis and the rapid characLerizaiion of materials. 

Differential scanning calorimetric methods are applied for the determination of heat of fusion, purity, specific heat and activation energy of decompn for undiluted, unmixed samples of TNT, TNB, Tetryl, RDX, HMX and PETN (Ref 28). The differential thermal analysis thermo-... 

For the determination of reaction parameters, as well as for the assessment of thermal safety, several thermokinetic methods have been developed such as differential scanning calorimetry (DSC), differential thermal analysis (DTA), accelerating rate calorimetry (ARC) and reaction calorimetry. Here, the discussion will be restricted to reaction calorimeters which resemble the later production-scale reactors of the corresponding industrial processes (batch or semi-batch reactors). We shall not discuss thermal analysis devices such as DSC or other micro-calorimetric devices which differ significantly from the production-scale reactor. 

Provenzano, M. R., Ouatmane, A., HaAdi, M., and Senesi, N. (2000). Differential scanning calorimetric analysis of composted materials from different sources. J. Therm. Anal. Calorim. 61(2), 607-614. 

Differential Thermal Analysis (DTA) earlier DTA data showed an unusually large heat of transformation endothermic in heating and exothermic in cooling. Later, through precision calorimetric methods [13], it was determined that the AH to be as high as 4,150 (J/mole), and also established the nature of the transition to be second order which is in agreement with our earlier single crystal X-ray diffraction study [6],... 

All methods in which the sample to be analyzed is gradually heated and its calorimetric behavior studied. The method includes thermogravimetry (TG) and differential thermal analysis (DTA). 

Figure 11.10. Differential thermal analysis (DTA). (a) Oassical apparatus (S = sample R = reference), (b) Calorimetric...

In the classical differential thermal analysis (DTA) system both sample and reference are heated by a single heat source. The two temperatures are measured by sensors embedded in the sample and reference. In the so-called Boersma system, the temperature sensors are attached to the sample pans. The data are recorded as the temperature difference between sample and reference as a function of time (or temperature). The object of these measurements is generally the determination of enthalpies of changes, and these in principle can be obtained from the area under a peak together with a knowledge of the heat capacity of the material, the total thermal resistance to heat flow of the sample and a number of other experimental factors. Many of these parameters are often difficult to determine hence, DTA methods have some inherent limitations regarding the determination of precise calorimetric values. 

Secondly, calorimetric measurements from the vapor phase may refer to nonequilibrium distributions of water vv ithin the crystals and through the zeolite bed. The very energetic vv ater-zeolite bond, especially for smaller water uptakes, means that water molecules may stick on sites vv here they first land. Subsequent redistribution can be very slow on the time scale of the experiment, particularly at the low temperatures employed 19, 21), 23° and 44°C. Finally, the information derived from differential thermal analysis is qualitative or at best only semiquantitative. 

TABLE 2 Differential Scanning Calorimetric Analysis of Lactose Calibration Standards 48... 

The differential calorimetric curves (DSC) of the various crystalline forms of triamterene grown from organic solutions containing water and from absolute organic solutions, and the DSC curves of triamterene crystals dried under reduced pressure have been described. The differential thermal analysis-thermogravimetry analysis (DTA-TG) thermograms are also given. 

All the obtained xerogels were amorphous solids, characterized by very broad IR bands in the region 1000-600 cm. TGA analysis of all the prepared xerogels showed two successive weight losses associated with endothermal peaks (evidenced by the differential calorimetric scan at 10°C min ) at about 100°C, due to the elimination of residual water and 2-propanol, and 200°C, related to the elimination of residual alkoxide l%ands for all the prepared xerogels. BET surface area measurements are reported for the calcined catalysts in Table 1. 

Calorimetric analysis was performed by a modified differential scanning calorimetry (DSC) procedure.HPLC was used to analyse the reconstituted solutions. After freeze-drying, the DSC traces of the three formulations shown in Table 1 displayed the three states that are typically encountered in freeze-dried solutions, namely complete crystallisation, partial crystallisation and complete amorphisation (glass formation). 

Figure 2. Differential scanning calorimetric analysis of trifluoroacetates in air at 4 CAnin. (a) 1-2-3 mixture, (b) Cu, (c) Ba, and (d) Y trifluoroacetate.

The heat of reaction and the rate of heat production in a reaction mixture as a function of temperature are important quantities for the design of reactors in chemical industry. Presently, several methods for the determination of these quantities are available, such as Differential Scanning Calorimetry, Differential Thermal Analysis, Bench Scale Calorimetry / / and adiabatic calorimetric methods. 

In contrast, one finds many DSCs which are used only for qualitative DTA work on transition temperatures. The often-posed question of the difference between DTA and DSC is therefore easily answered DTA is the general term covering all differential thermal analysis techniques, while DSC must be reserved for scanning experiments that yield calorimetric information. 

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