DSC runs

Using the Toolbox, Transform, and Identify functions, the analyst can perform many general analyses such as a Tg of a DSC run or the weight loss in a TGA run. For Instance, to identify a TGA weight loss the operator could draw two guide lines on the screen, use the Identify function to measure the displacement, and the report generator to output the displacement and units. 

Differential Scanning Calorimetry. A sample and an inert reference sample are heated separately so that they are thermally balanced, and the difference in energy input to the samples to keep them at the same temperature is recorded. Similarly to DTA analysis, DSC experiments can also be carried out isothermally. Data on heat generation rates within a short period of time are obtained. Experimental curves from DSC runs are similar in shape to DTA curves. The results are more accurate than those from DTA as far as the TMRbaiherm is concerned. 

The same appears to be valid for chemiluminescence and DSC runs of PP films oxidized at 120-140°C (Figure 13). 

Figure 26 Comparison of non-isothermal chemiluminescence experiments with DSC runs in oxygen for Whatman cellulose of different pH due to the presence of magnesium carbonate.

A DSC run in scanning mode does not provide the proper experimental conditions for autocatalytic decomposition to be identified as such because there is a continuous increase in temperature in the operation. In particular, the test does not determine the true thermal characteristics of autocatalytic... 

DSC, TGA, and DMA were performed using a DuPont 9000 system. DSC runs were performed at scan rates of 10° C/minute and repeated at least one time. TGA runs were also carried out at 10° C/minute. DMA scans were at 5° C/minute with a 0.2 mm oscillation amplitude. 

The first and third reactions involve a breaking of Ni-N bonds whereas the second step involves an exothermic rearrangement to a square pyramidal species and the final step an exothermic rearrangement to the diamagnetic, purple parent complex. The color changes accompanying the dsc runs are indicated above. 

By working with vinyl ester (specifically DERAKANE 411-C50), Michaud [9] observed a drastic influence of the fibers (E-glass) on the induction time (i.e., the time required for the reaction to become observable at a specific temperature). An induction time of 90 minutes and 5.5 hours was necessary for RTM runs at 53°C and DSC runs at 50°C, respectively. Lee and Lee [33] affirmed that the age of the resin can also alter the induction time A reduction time of 50 percent was found after 10 months of storage at 70°C. All these effects are more evident at low temperatures. 

Isothermal and nonisothermal DSC runs for this particular system could be fitted by the following autocatalytic equation (Montserrat and Malek, 1993) ... 

But a striking behavior was observed when analyzing dynamic DSC runs at a constant heating rate of 10 K min-1. In these runs, the first-order behavior was found over the whole conversion range, but the activation energy was E = 110 kJ mol-1 (35-40 kJ mol-1 higher than the isothermal value). Therefore, the simple first-order kinetics seems to be an apparent... 

Figures 12 and 14 show first and second DSC runs of Nylon 6 and Nylon 6-6 using seventy to eighty microgram quantities of fiber. In the initial run on this particular sample of Nylon 6, no thermal phenomena are discernable up to the melt, which is a...

Figure 10.10 shows the non-isothermal DSC runs for different PEEK/SWCNT composites containing 1 wt% CNT loading. The incorporation of SWCNTs leads to a significant shift of the... 

Fig. 9 Quality control of excipients by using the glass transition. Example of Carbopol 974 P. Second DSC run in order to eliminate water and relaxation Influence of the heating rate.

Acidity modification of the external surface was characterized by differential scanning calorimetry (DSC) after pre-adsorption of 4-methyl quinoline which cannot enter the pore system. For comparison, sample OW-ZSM-5 and sample lOW-ZSM-5 were subjected to DSC measurements without amine pre-adsorption. In each case, after completion of the first DSC run and re-establishment of initial conditions a second run was performed, and the resulting profile was substracted from that of the first run. In this way, device-dependent factors are eliminated. Measurements were performed by means of a SETARAM DSC-92 equipment under 3 1/h air and nitrogen, respectively, and a heating rate of 5 K/min. 

Figure 4. DSC run of sample lOW-ZSM-5 after pre-adsorption of 4-methyl quinoline in nitrogen. Experimental conditions as in Figure 3.

Figure 7.9. First and second temperature DSC run for an injection moulded starch sample. (From Balta Calleja et al, 1999.)...

Recrystallization of amylopectin is a reversible process that can be analyzed by DSC below 100°C (Miles et al., 1985). Amylopectin retrogradation was measured in starch systems containing sucrose from DSC runs immediately after freezing and after 91 days of storage at —80 and — 18°C. Aliquots of gelatinized pastes were run between 20 and 120°C at a heating rate of 10°C min in order to detect the presence of the amylopectin retrogradation peak. 

This loading plot shows features similar to the sigmoidal curve generated by the integrated heat flow during a DSC run for the analysis of epoxy-resin cure (Figure 3.5, Section 3.2.2) that measures the extent of reaction as a function of cure time. 

The third scenario (Figure 3.3c) represents the situation when Form 1 is present below T0, in which case it will be metastable with respect to 11 and may undergo a spontaneous solid state transformation to the latter. Examination of Figure 3.2a indicates that in this case the transformation will be exothermic. Form 11 may then undergo a second solid state transformation to 1 at 7 , that will then melt at Ml-Finally, metastable Form 1 may be present at the outset of the experiment and remain kinetically stable throughout the DSC run it will then simply melt at Tm (Figure 3.3d). 

---