Differential Scanning Calorimetry DSC tracings

Figure 24.1 Differential scanning calorimetry (DSC) traces for the different N,N -dimethylpyr-rolidinium (Pn) species. The y-axis has been adjusted to allow comparison between species. Thermal transitions are recorded as peaks (endothermic) or troughs (exothermic) and indicate changes of phase. The structurally similar dicyanamide (DCA) and thiocyanate species both show broad phase transitions in comparison to the TFSA species.

Figure 3. Differential scanning calorimetry (DSC) traces of the PF resin alone and of the PF resin + 6% NaMMT.

At the nominal melting point Tm there is a first-order phase transition from the crystal to the mesophase with the usual discontinuities in the extensive properties (e.g. volume and entropy). In Fig. 5.7, we schematically illustrate a hypothetical differential-scanning-calorimetry (DSC) trace and the variation in volume of the sample versus temperature for an ideal nematic. The values for the changes in enthalpy (AH 45 kJ mol" ) and volume (A V 10%) at are typical of those changes in extensive properties that occur on melting ordinary organic molecular crystals. However, if you continue to heat the opalescent-looking mesophase, there is a second transition to a transparent isotropic state above Td. Nematic melts... 

Figure 19.2 shows the differential scanning calorimetry (DSC) traces of a sample after application as a thin film in the sample holder and drying at 80° C to remove the solvent. From DSC the sample appears stable up to 120°C, above which the thermal initiator activates the thermal polymerization of the acrylate monomer. 

Cross-linking constrains the conformational flexibility of biopolymers and, as a rule, stabilizes their secondary, tertiary, and quaternary structures against the denaturing effects of high temperatures.29 We used differential scanning calorimetry (DSC) to compare the heat-induced conformational transitions of selected RNase A samples that were characterized in Figure 15.2. A brief introduction to DSC is provided in Section 15.15.1 for those readers unfamiliar with this biophysical method. Trace 1 in Figure 15.3a is the heat absorption... 

When a number of polymorphs are identified in step one they should be characterized by Differential Scanning Calorimetry (DSC) to obtain AHm and Tm data. This information confirms their relative stabilities with respect to temperature. If DSC data cannot be obtained then slurry experiments should be performed. It is always good practice to confirm the relative stability with sluny experiments because DSC traces can be difficult to interpret correctly, and can mask subtle effects. 

Sugama and Allan [5] used calcium aluminates (tricalcium aluminate, C -A, monocalcium aluminate, C A, or calcium dialuminate, C A2) as the cation donors and reacted them with an ammonium polyphosphate fertilizer solution and formed quicksetting cements. The purpose of this study was to develop cements that are not affected by the CO2 environment and are useful as downhole cements in geothermal wells (see Chapter 15). The composition of the fertilizer was 11.1 wt% N as ammonia, 37.0 wt% P2O3, 50.79 wt% water, and the rest trace elements. Differential scanning calorimetry (DSC) showed that the reaction rates of the three minerals are in the decreasing order ... 

Differential scanning calorimetry, DSC, and differential thermal analysis, DTA show similar traces for T measurements although the property being measured is different. DSC measures the amount of heat required to increase the sample temperature over that required to heat up a reference material, normally an empty pan, to the same temperature. The variation in power necessary to maintain this level during a transition is monitored. DTA measures the difference in temperature between the sample and the reference material when both are heated at the same temperature rate. These techniques require a small amount of specimen, about 15 mg, and have... 

The thermogravimetric analyses (TGA) of microcrystalline powders of this complex trace revealed two discrete mass losses at 110 °C and 145 °C corresponding to a mass percent of four (4.5%) and twelve benzene molecules (13.5%) respectively. It was rationalized that the initial mass loss corresponded to the loss of four disordered benzene units. The mass loss at 145 °C was attributed to the loss of the ordered twelve benzenes. Differential scanning calorimetry (DSC), optical microscopy and X-ray powder analysis showed that there was no phase change associated with the first mass loss. 

Figure 4.19B shows the progress of crystallization during the in situ activation as determined by differential scanning calorimetry (DSC) and X-ray diffraction (XRD). The bulk structural changes of the glassy metal alloy during the in situ activation are reflected by the XRD traces shown in Fig. 4.20, which depicts the results of two analyses from samples taken at typical points in the activation curve (Fig. 19A) namely, in the low activity region (top trace in Fig. 4.20) and in the final stage of activation (bottom trace in Fig. 4.20). Comparison of the two wide scans in Fig. 4.20 shows the significant increase in...

The equilibrium water uptakes of series 2 polymers in distilled water are illustrated in Fig. 4 along with that of soluble PH PM A, (f) which was prepared by a similar method. As expected, water content of all three series increased monatonically with the HEMA content in the polymer. We were encouraged that the EWC of PHEMA appeared very similar to that of crosslinked PHEMA hydrogel. Unexpectedly, the EWC of these polymers changed dramatically in phosphate buffered saline (PBS). Some of the more hydrophilic polymers in series 1 dissolved in PBS, the EWC of hydrophilic series 2 polymers increased dramatically and that of series 3 polymers to a lesser extent. Differential Scanning Calorimetry (DSC) of hydrated polymer indicated that the content of freezable water (82, 83) in the more hydrophilic polymers increased dramatically also in PBS. We attribute these changes to ionization of trace quantities of acidic impurity in the PBS buffer. 

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). 

The isobaric heat capacity is obtained mathematically by differentiation of the specific enthalpy. Graphically, Cp is given by the slope of the enthalpy versus temperature trace leading to an individually constant number for isobaric heat capacity in the liquid state and also for the solid state, if no phase transitions occur. This result for the solid state is in contradiction with measurement data obtained by techniques such as differential scanning calorimetry (DSC) but has been proved to be correct for the liquid state. Dynamic pulse-heating rates are usually too fast and small phase transitions, which are detectable by DSC or similar instruments, become undetectable. As a result, pulse-heating data for Cp... 

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