Differential scanning thermograms

The solid fat content and differential scanning thermograms of milk fat and its fractions obtained from a two-stage fractionation process clearly demonstrates the differentiated physical properties that may be obtained by the process (Dimick et a ., 1996a). Figure 8.2 gives the typical melting... 

Figure 3. Differential scanning thermograms of 303-0, 303-50 and zinc stearate powder in a second melting pass.

Figure 4. Differential scanning thermograms of Zn-S-EPDM with various loadings of zinc stearate.

Polymer A showed a crystalline X-ray diffraction pattern and an endothermic peak at 31-42 C in differential scanning thermograms. The polymer had birefringence below 90 C under a polarizing microscope. It is of interest to speculate as follows. Both of the hydrocarbon side chains and the polysaccharide main chains are crystalline and the polymer A exhibits a unique two-stage melting process of both crystalline regions. The polymer possibly forms a liquid-crystalline mesophase between these two transition temperatures. 

We express our sincere appreciation to Charles Schramm, Alain Jacques, and Robert Steltenkamp for helpful discussions Christine Bielh, Francoise Deville, and Karla Tramutola for providing excellent technical assistance. We thank Suman Chopra and Rodman Heu for their help in obtaining differential scanning thermograms and electron micrographs, respectively. 

Vaisman et al. [103] formed a uniform, multi-walled nanotubes (MWNTs) distribution in water-soluble (poly(ethylene glycol)) and water-insoluble (polypropylene) polymers. In order to understand the surface-charge-related stability of the treated nanotubes solutions, zeta-potential measurements were applied. Quantification of the state of the M WNT dispersion was derived from particle-size analysis, while visual characterization was based on optical and electron microscopy. In order to estimate the nucleating ability of the surface-modified CNTs, the temperature of crystallization and the degree of crystallinity were calculated from differential scanning thermograms. 

Fig. 5. Differential scanning calorimetry thermogram. Amorphous PPS is heated from room temperature to 325°C at 20°C/min.

Fig. 10. Differential scanning calorimetry thermogram of a thermoset. The reaction order is 1.83, = 95 kJ/mol (22.7 kcal/mol), and the heat of...

In a testing context, it refers to the first detection of exothermic-activity on the thermogram. The differential scanning calorimeter (DSC) has a scan rate of I0°C/min, whereas the accelerating rate calorimeter (ARC) has a sensitivity of 0.02°C/min. Consequently, the temperature at which thermal activity is detected by the DSC can be as much as 50°C different from ARC data. 

Triethanolamine salts of alcohol sulfates form white crystals when obtained in pure form after recrystallization. At their melting point they are semisolid with gelatinous appearance and the transition is difficult to detect. Melting points, determined through thermograms obtained by differential scanning calorimetry, gave 72, 76, 80, and 86°C for dodecyl, tetradecyl, hexadecyl, and octadecyl sulfates, respectively [63]. 

The output of a differential scanning calorimeter is a measure of the power (the rate of energy supply) supplied to the sample cell. The thermogram in the third illustration shows a peak that signals a phase change. The thermogram does not look much like a heating curve, but it contains all the necessary information and is easily transformed into the familiar shape. 

A thermogram from a differential scanning calorimeter. The peak indicates a phase change in the sample, and the difference in base line before and after the phase transition is due to the difference in heat capacities of the two phases. 

Differential Scanning Calorimeter (DSC) thermograms were obtained on a Perkin Elmer DSC-2 run at 10°C per minutes. Dynamic Mechanical Thermal Analysis (DMTA) spectra were obtained on a Polymer Labs DMTA at a frequency of 1Hz with a temperature range from -150°C to +150°C at a scan rate of 5°C per minute. 

We use differential scanning calorimetry - which we invariably shorten to DSC - to analyze the thermal properties of polymer samples as a function of temperature. We encapsulate a small sample of polymer, typically weighing a few milligrams, in an aluminum pan that we place on top of a small heater within an insulated cell. We place an empty sample pan atop the heater of an identical reference cell. The temperature of the two cells is ramped at a precise rate and the difference in heat required to maintain the two cells at the same temperature is recorded. A computer provides the results as a thermogram, in which heat flow is plotted as a function of temperature, a schematic example of which is shown in Fig. 7.13. 

Figure 2. Comparison of the Differential Scanning Calorimetry (DSC) thermograms of the homopolymer HB and various block copolymers to that of the LDPE. Weight of each polymer sample is indicated in the parentheses. The instrument range is 2 mcal/s for all the runs.

The differential scanning calorimetry (DSC) thermogram of miconazole was obtained using a DuPont 2100 thermal analyzer system. The thermogram shown in Fig. 2 was obtained at a heating rate of 10°C/min and was run over the range 50—300 °C. Miconazole was found to melt at 186.55 °C. 

Fig. 2. Differential scanning calorimetry thermogram of miconazole nitrate.

The differential scanning calorimetry (DSC) thermogram of niclosamide was obtained using a General V4 IC DuPont 2100. The data points represented by the curve shown in Fig. 2 were collected from 200 to 400°C using a heating rate of 5°C/ min. It was found that the compound melted at 231.66°C with an enthalpy of fusion equal to 69.31 J/g. 

Fig. 2 Typical thermogram obtained using conventional differential scanning calorimetry on PNIPAM solution the temperature of maximum heat capacity (Tmax), the width of the transition at half-height (AT1/2), the heat of transition (AH), the difference in the heat capacity before and after the transition (ACp), and the demixing temperature (Tdem). (Adapted from Ref. [200])...

One such property, as has been demonstrated (see [26]), is the change in partial heat capacity of the copolymer solution upon the heat-induced conformational transition of macromolecules. Such a change was detected by high-sensitivity differential scanning calorimetry (HS-DCS). The DSC data for the NVCl/NVIAz-copolymers synthesized at initial comonomer ratios of 85 15 and 90 10 (mole/mole) are given as thermograms in Fig. 4. 

Differential scanning calorimetry can be extremely useful in the study of compound polymorphism. Suitably prepared films of 2,4-dinitrophenyl-2,4-dinitrobenzoate will exhibit phase transformations among all four polymorphs [46], as has been shown in Fig. 6. The complicated DSC thermogram contains... 

Fig. 6 Differential scanning calorimetry thermogram of 2,4-dinitrophenyl-2,4-dinitro-benzoate, illustrating the recrystallization of form IV into form III (Tl), the melting of forms III and II (T2 and T4), the solidification of the melts produced by T2 and T4 (T3 and T5), and the melting of form I (T6). (Data adapted from Ref. 46.)...

Fig. 10 Differential scanning calorimetry thermograms obtained for diflunisal, form I (lower trace) and form II (upper trace).

Fig. 12 Differential scanning calorimetry thermograms obtained for piretanide, as recrystallized from (a) f-butanol, (b) n-propanol, (c) i-propanol, and (d) IV V-dimethyl-formamide. (Data adapted from Ref. 34.)...

Probably the main weakness of DTA as a method of analysis remains the difficulty of linking the thermal changes shown on the thermogram, with the actual thermal processes taking place. It should be noted that data obtained by DTA are often similar to those available for differential scanning calorimetry. Indeed the two techniques overlap extensively and may be seen as complementary. A comparison of the two techniques is made at the end of the next section. 

Differential scanning calorimeter measurement, 10 17-18. See also DSC thermogram... 

Use of thermogravimetry to facilitate interpretation of differential scanning calorimetry thermograms... 

---