DSC scan

Fig. 7. Dsc scan for glassy Alg Ni Fe2Gdg alloy where is the crystallisation temperature and T the eutectic temperature.

A dsc scan of a typical commercial ionomer shows two endotherms at about 50 and 98°C, respectively. The size of the lower peak can be correlated with stiffness and yield point. The thermal history of the sample influences the relative size of the lower peak and moves it to higher temperatures, while the upper peak decreases in size but remains at the same temperature. Room temperature aging also increases the size of the lower endotherm. 

Cure kinetics of thermosets are usually deterrnined by dsc (63,64). However, for phenohc resins, the information is limited to the early stages of the cure because of the volatiles associated with the process. For pressurized dsc ceUs, the upper limit on temperature is ca 170°C. Differential scanning calorimetry is also used to measure the kinetics and reaction enthalpies of hquid resins in coatings, adhesives, laminations, and foam. Software packages that interpret dsc scans in terms of the cure kinetics are supphed by instmment manufacturers. 

Figures DSC scans of (1) PS (M = 2.5.1(F) and its acylated derivatives with following contents of carboxyl group (2) 4.5, (3) 14.3, (4) 16.6, (5) 20.0 mol%, prepared by using FeCh, SnCLi, AICI3, and BF3-OEt2, respectively.

Dynamic DSC scans of resole resins show two distinguishable reaction peaks, which correspond to formaldehyde addition and die formation of edier and metiiy-lene bridges characterized by different activation energies. Kinetic parameters calculated using a regression analysis show good agreement widi experimental values.75... 

Figure 10 Oscillating differential scanning calorimetric (ODSC) curves showing the separation of the glass transition (reversible, i.e., thermodynamic component) and enthal-pic relaxation (irreversible, i.e., kinetic component) which overlap in the full DSC scan. (Reprinted with permission from Ref. 38.)... 

Figure 10 DSC scans for the normal (continuous line) and non-melt (dashed line) areas of the injection-molded sheet.

Figure 47 First heating cycle DSC scan of the failed part.

Figure 15.4 SDS-PAGE of formalin-treated RNase A fractions taken before (lanes 1-3) and after (lanes 4-6) the DSC scans shown in Figure 15.3c. Lanes 1 and 4, monomer lanes 2 and 5, dimer lanes 3 and 6, mixture of oligomers with >5 cross-linked proteins M, molecular mass markers as in Figure 15.2. See Rait et al.10 for details.

A DSC scan for nalidixic acid was performed by Houghtaling.(9) The instrument used was a Perkin-Elmer DSC-1B at a scan rate of l°/min. The curve is presented in Figure 7. A sharp peak at 229-230.5° (corr) represents the sample melting. 

For single reactions with uncomplicated kinetics and with availability of a truly representative sample, the DSC can be used with different scan speeds (temperature/time) to determine kinetic constants in the Arrhenius equation. This method, proposed by Ozawa [83] has been accepted by the ASTM Method E698. After determining kinetic constants by this method, it is desirable to check the constants by running an isothermal DSC aging test for a period of time followed by a DSC scan to see if the predicted fraction decomposition... 

An example of monotropic behavior consists of the system formed by anhydrous ibuprofen lysinate [41,42], Figure 4.12 shows the DSC thermogram of this compound over the temperature range of 20-200°C, where two different endothermic transitions were noted for the substance (one at 63.7°C and the other at 180.1°C). A second cyclical DSC scan from 25 to 75°C demonstrated that the 64°C endotherm, generated on heating, had a complementary 62°C exotherm, formed on cooling (see Fig. 4.13). The superimposable character of the traces in the thermograms demonstrates that both these processes were reversible, and indicates that the observed transition is associated with an enantiotropic phase interconversion [41]. X-ray powder (XRPD) diffraction patterns acquired at room temperature, 70°C, and... 

Fig. 11 Cooling and heating DSC scans (10°Cmin 1) of original and purified E24EP57EO19. (Reprinted with permission from [29], Copyright 2002 American Chemical Society)...

Figure 5.6. Dynamic DSC scan of PTFE (from Davis and Zimmerman7 4).

DSC scans were performed at 20,C/min after a rapid quench from above the sample glass transition temperature. A nitrogen atmosphere was used. 

Figure 13.15 A plot of In (v/Tm2) vs. 1/Tm for the thermal denaturation of thermolysin using DSC scan rates of 1.9,1.0, 0.5, and 0.2 °K/min. The plot assumes Arrhenius behavior holds. The slope of the plot is equal to -EalR. Using R = 1.9872 cal/deg-mol, one can calculate the activation energy to be 63.3 kcal/mol. (Data plotted were obtained from Reference 138.)...

Fig. 53. DSC scans of cyclohexane-modified cyanurates after curing at r=80 °C showing melting peaks of cyclohexane...

DSC scans of the quenched and annealed samples were recorded. 

DSC indicates a gradual increase in Tg with increasing PHBA/diol ratios except for the 60/40 ratio. Otherwise DSC scans of these polyols are complex and are strongly affected by the thermal history of the materials. The 40/60 and 50/50 PHBA/diol ratio materials often have two endothermic peaks, one near 10 and the other near 70°. The relative size of these peaks vary depending on sample history. Small peaks at about 100 are also sometimes observed. 

Under the DSC conditions (N, scanning rate = 10°C/min), it is apparent that the decomposition processes are occurring at a much faster rate at or near the temperature at which cure is taking place in all the pure dlcyanate samples. Both BADCy and THIOCy showed small exotherms (onset at 277°C and 226°C and peak at 308°C and 289°C, respectively). Their major decompositions began about 251°C and 246°C, respectively, as observed by TGA. On the contrary, all the 1 1 BCB/dlcyanate blends displayed the expected thermal transitions. Besides initial Tg s (20-28°C) and Tm s (171-183°C), all samples showed small exotherms in their DSC scans with maxima at 147-151°C. This is attributable to the thermally-induced crystallization in the mixtures, which also led to some initial phase separation. The polymerization exotherms are consistent with the typical temperature ranges for the known benzocyclobutene-based systems (onset 229-233°C max. 259-266°C). 

The authors wish to thank Dr. K. Nakamura, Industrial Research Institute of Kanagawa Prefecture, Yokohama, Japan, for recording the DSC scans shown in Figure 2. 

From a DSC scan of the homopolymer of PHBA one can observe a major endotherm at 350 °C and a much smaller one at 445 °C (see Fig. 3) [29], The first transition has been examined by electron diffraction [27-30], X-ray diffraction [28] and proton and 13CNMR [30]. Additional insights have been provided by synthesizing much lower molecular weight samples which permit study of these transitions at appreciably lower temperatures [29]. These low molar mass homopolymers can also go into a nematic phase under a modest shear. 

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