Differential scanning calorimetry apparatus

In differential scanning calorimetry (DSC), higher precision can be obtained and heat capacities can be measured. The apparatus is similar to that for a DTA analysis, with the primary difference being that the sample and reference are in separate heat sinks that are heated by individual heaters (see the following illustration). The temperatures of the two samples are kept the same by differential heating. Even slight... 

DSC (differential scanning calorimetry) was performed using a Netzsch Phoenix El apparatus. Typically, samples of about 20 mg were applied in aluminium cold-sealed crucibles with heating/cooling rates of 5 °C/min. 

Power-compensated differential scanning calorimetry (DSC) apparatus (S = sample R = reference). 

Differential scanning calorimetry (DSC) compares the two different heat flows one to or from the sample to be studied, the other to or from a substance with no phase transitions in the range to be measured e. g. glassmaking sand. Figure 1.45 is the scheme of a DSC system Fig. 1.46 is a commercial apparatus for DSC measurements. 

Characterization. Differential scanning calorimetry and thermal mechanical analysis data were obtained on a DuPont 990 thermal analyzer coupled with a DuPont DSC or TMA cell. Isothermal aging studies were carried out with an automatic multisample apparatus. 

Differential scanning calorimetry is performed at a heating rate of 2°C/min from 20°C to 100°C. The checkers used a conventional melting point apparatus. 

Figure 2.39 Differential scanning calorimetry (DSC) apparatus. Reprinted with permission from J. E. Mark, Physical Chemistry of Polymers, ACS Audio Course C-89, American Chemical Society, Washington, DC, 1986. Copyright 1986, American Chemical Society.

This would not be problematic if standardized, reliable, reproducible, and inexpensive laboratory tests were available to estimate each of the required properties. Although several specialized laboratory tests are available to measure some properties (e.g., specific heat capacity can be determined by differential scanning calorimetry [DSC]), many of these tests are still research tools and standard procedures to develop material properties for fire modeling have not yet been developed. Even if standard procedures were available, it would likely be so expensive to conduct 5+ different specialized laboratory tests for each material so that practicing engineers would be unable to apply this approach to real-world projects in an economically viable way. Furthermore, there is no guarantee that properties measured independently from multiple laboratory tests will provide accurate predictions of pyrolysis behavior in a slab pyrolysis/combustion experiment such as the Cone Calorimeter or Fire Propagation Apparatus. 

For the examinations three different mono- and multifilament PET-yams were used. As seen by the effective temperature two of the fibers (220 dtex multifil and 360 monofil) were heat setted in air at 160°C. The experiments in air and supercritical C02 were carried out in a 400 ml autoclave, the DSC measurements (Differential Scanning Calorimetry) under pressure in a home-made apparatus with an integrated TA-Instruments calorimeter. 

Polymorphism and kinetics of crystallization of TAG and fat under static conditions (e.g., in differential scanning calorimetry [DSC] apparatus) have been studied for a long time and are summarized in many reviews (2-6). Yet, these conditions are far-removed from industrial applications, where crystallization is usually achieved under shear (dynamic). Shearing has a major effect on crystallization kinetics it induces a faster and more homogeneous crystallization, often in the stable form and with a refined grain size. Yet, its effect is far from being fully understood. Recently, several studies of dynamic crystallization of lipids have been reported (7-12). 

Thermal Behavior. The thermal behavior of the compounds prepared in this study was investigated using a capillary melting point apparatus, hot stage polarized light microscopy, and differential scanning calorimetry. Melting was not observed... 

The temperature dependence of K for the DuPont DTA sample holder is illustrated in Figure 5.39 (106). As can be seen, the calorimetric sensitivity of the apparatus decreases with temperature that is, more heat is required per unit area. In differential scanning calorimetry, such as with the Perkin-Elmer instrument, K is independent of temperature hence, only a one-temperature calibration is required. The problem of multitemperature calibration in DTA is also eliminated in the technique of constant-sensitivity DTA proposed by Wendlandt and Williams (107). 

Since AH is proportional to the area of the DTA peak, one ought to be able to measure heats of reaction directly, using the equation 3.5.22. Indeed we can and such is the basis of a related method called Differential Scanning Calorimetry (DSC), but only if the apparatus is modified suitably. We find that it is difficult to measure the area of the peak obtained by DTA accurately. Although one could use an integrating recorder to convert the peak to an electrical signal, there is no way to use this signal in a control-loop feed-back to produce the desired result. 

Curing studies were performed using a DuPont 990 Thermal Analyzer for differential scanning calorimetry (DSC) and a specially designed apparatus for DC resistance measurements. 

In calorimetry techniques, enthalpy changes accompanying physical or chemical events, whether they are exothermic or endothermic, are measured and monitored either as a function of temperature or time. Thus, a calorimeter is able to collect a heat flux exchanged between the sample and the sensible part of the apparatus, generally made of thermocouples, and to register it. The result is a profile of the rate of enthalpy change, either as a function of temperature as the sample is heated at a known linear rate in differential scanning calorimetry (DSC), or as a function of time when the calorimeter is held at constant temperatnre in isothermal differential calorimetry (DC). 

The overall crystallization kinetics of molten blends were analyzed by differential scanning calorimetry with a Perkin-Elmer DSC 2 apparatus. Following melting, the samples were heated at 85° C for 5 min. and isothermally crystallized at various T recording the heat of crystallization as a function of permanence time. The fraction of the material crystallized after time t was determined by means of the relation - Qt/Qoo> where Q - is the heat generated at time t and Qoo is the total heat of crystallization for t = . 

The metathesis activity of these new classes of catalysts has been tested in the solvent-free polymerization of dicyclopentadiene. In a first test we screened their activity in a Differential Scanning Calorimetry (DSC) apparatus and compared it with the activity of the arylthio substituted ruthenium carbene 7 and the "classical" benzylidene catalyst 6. The results are given in Table 8. 

---