Differential scanning calorimetry calibration

A variety of techniques have been used to determine the extent of crystallinity in a polymer, including X-ray diffraction, density, IR, NMR, and heat of fusion [Sperling, 2001 Wunderlich, 1973], X-ray diffraction is the most direct method but requires the somewhat difficult separation of the crystalline and amorphous scattering envelops. The other methods are indirect methods but are easier to use since one need not be an expert in the field as with X-ray diffraction. Heat of fusion is probably the most often used method since reliable thermal analysis instruments are commercially available and easy to use [Bershtein and Egorov, 1994 Wendlandt, 1986], The difficulty in using thermal analysis (differential scanning calorimetry and differential thermal analysis) or any of the indirect methods is the uncertainty in the values of the quantity measured (e.g., the heat of fusion per gram of sample or density) for 0 and 100% crystalline samples since such samples seldom exist. The best technique is to calibrate the method with samples whose crystallinites have been determined by X-ray diffraction. 

Differential Scanning Calorimetry. A Perkin-Elmer Model DSC-IB calorimeter was used to examine crystallinity by measuring areas under the fusion curve as a function of elastomer composition and processing variables. Areas of endotherms were calibrated against an indium standard and the crystallinity calculated using a value of —138 J/g for a 100% crystalline polypropylene polymer (II). 

Differential scanning calorimetry (DSC) was used in investigating the curing kinetics of the unsaturated polyester resin. For the study, we used a DuPont 1090 Thermal Analyzer, equipped with a 910 DSC Module. Indium was used for temperature and calorimetric calibrations, following the procedure described in the operating meinual of the instrximent. The experimental procedure employed is very similar to that described in the literature (8-13) cind we have discussed it elsewhere (14). 

The thermal behavior of ot-chitin was examined by differential scanning calorimetry (DSC) using a DSC-25 Mettler instrument. Samples (each 5 mg) were hermetically sealed in aluminum pans and scanned over a temperature range of 0-350 °C at a scan rate of 5 °C/min. The instrument was calibrated using indium, and the calorimetric data were analyzed using STAR software (version 9). 

Correlation of total, bound, and surface water in raw materials was the topic of a paper by Torlini and Ciurczak in 1987.The NIR was calibrated by Karl Fischer titration, differential scanning calorimetry (DSC), and thermal gravimetric analysis (TGA) for the various water types. NIR could distinguish surface from bound water, whereas standard loss on drying (LOD) could not. 

Differential Scanning Calorimetry. DSC scans were made at 20°C min"1 on a Mettler TA300O system equipped with a DSC-30 low temperature module. Temperature calibration was done with a multiple Indium-lead-nickel standard. An indium standard was used for heat flow calibration. Thin shavings (ca. 0.5 mm thick) were cut with a razor blade from the cross-sectional edge of a plaque. These sections contained both surface and center portions. 

The deactivated catalysts were also burned in a calorimeter under compressed air flowing at 40 ml/min. (Thermal Analysis Station TAS 100 - Rigaku - TG 8110). Analysis were performed by differential scanning calorimetry (TPO/DSC) and combustion heats were obtained by integration of the profiles and using appropriate calibration samples. 

Using differential scanning calorimetry (DSC) (or, less directly, differential thermal analysis (DTA)) (see Section 2.8.5., above) it is possible to measure several of the thermodynamic properties of solids and of solid state reactions. The DSC response is directly proportional to the heat capacity, Cp, of the sample, so that by use of a calibrant it is possible to obtain values of this fundamental thermodynamic property, at a particular temperature, or as an average over a specified temperature range. Other thermodynamic properties are readily derived from such measurements ... 

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). 

Virtually every chemical process involves a change in the heat capacity of the sample. When measured by differential scanning calorimetry, such changes produce a curve similar to Figure 17.7 (except with a y-axis in cal/sec). The area under the DSC curve is determined in the same manner as in DTA. This area is proportional to the amount of heat evolved or absorbed by the reaction, and the heat of reaction is obtained by dividing this by the moles of sample used. If the heat of reaction is known, the moles of sample present can be calculated from essentially the same equation (i.e., the integral of Equation 17.6). All determinations should be preceded by an analysis of a standard sample of known mass and A/7 in order to calibrate the particular instrument used. 

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