DTA-curves

Melting temperatures of as-polymerized powders are high, ie, 198—205°C as measured by differential thermal analysis (dta) or hot-stage microscopy (76). Two peaks are usually observed in dta curves a small lower temperature peak and the main melting peak. The small peak seems to be related to polymer crystallized by precipitation rather than during polymerization. 

From the data of DTA and TGA analyses illustrated in Fig. 4, its evident that the visible exo-peaks in the range of 140-150°C appear in DTA curves (Fig. 4a), which can be taken as evidence of a crosslinking reaction of acylated macromolecules at the expense of side chain... 

Figure 2 DTA curves of melting and crystallization of PE at 200 MPa. Numbers in the figure correspond to the experimental conditions described in the text. (From Ref. 52.)...

The above DTA curve is similar to that of the following reaction ... 

DTA is especially suited in the construction of unknown phase diagrams of binary compounds. A hypothetical phase die am and the DTA curves which would be used to construct it are shown in the followii diagram, given as 7.2.1. on the next p e. 

Draw an expected TGA curve for all 3 compounds, using the temperatures that you used in your DTA curves. 

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. 

As it can be seen from reaction mechanisms, all water can be removed at up to 300-350°C. The small exothermal area on DTA curve at 400-450°C can be attributed to reciystallization processes after H20 and OH groups removal. 

The DTG and DTA curves for CMK-3N1.25, CMK-3N2.00, OCM-.NO.25 and OCM-.N0.75 reveal two peaks in the 600-800 K range, which indicates two kinds of carbons of different graphitisation levels in these samples. The CMK-3 material does not bum up totally (Table 1). It may be due to extra-skeleton siliceous fragments possibly present in large cylindrical pores of SBA-15 and/or to iron species trapped in the carbon products. 

In case of CMK-3N2.00 and OCM-.NO.25, the areas under the second peak of the DTA curves are much smaller than the areas under the first peak, although they correspond to similar mass losses reflected in the DTG curves. Presumably, burning up of carbon more strongly bound to the siliceous skeleton is more difficult and some carbon may remain unbumt, trapped between siliceous layers. 

Schematic DTA curve of a typical polymer. Note glass transitions reflect a heat capacity change and thus they are seen as steps on the baseline rather than peaks.

DTA curve of a seven-component polymer mixture showing endothermic peaks associated with melting. 

The DTA curves in Figures 7 and 8 were obtained with a DuPont Model 900 instrument. Figure 8 shows that the base melts sharply and Figure 7 shows that the hydrochloride melts with decomposition. Visually the hydrochloride melts at 274°C, but decomposition takes place over a large temperature range (Figure 7). 

Figure 9.1. TG-DTA curves for Bisphenol A-derived poly(formal) (A) and Bisphenol AF-derived poly(formal) (AF).

FIGURE 15.7 A representation of the results of the differential thermal analysis (a DTA curve) of a sample that melts at a particular temperature. 

FIGURE 15.8 Left, applying the temperature program in Figure 15.6(a) to a sample that undergoes an exothermic process. Right, a representation of the DTA curve of the exothermic process. 

Figure 2. Results of derivatographic researches of Zn(OH)2, CFO and ZnCFO a - DTA curves, b - TG curves...

The procedure is to heat up a sample of these materials in the thermobalance. Figure 10 shows the DTA-curve and the evaluation of point A and B. These can be... 

Fig. 65. Simultaneous TG-DTA curves of o-acetophenetitide measured at various pressures. A start of vaporization, B boiling point, C end of vaporization...

Stage I The endothermal dehydration of calcium acetate monohydrate occurs giving rise to the anhydrous salt. It is easily noticed by an endothermal band on DTA curve between 200°C and 250°C. 

Figure 2.40. Phase diagram of the Mg-Cu alloy system. For the alloys marked (1) (at 5 at.% Cu) and (2) (at 20 at.% Cu), the DTA curves are shown on the right. Notice that, on cooling, a sharp thermal effect due to the invariant eutectic transformation is observed. At higher temperature the crossing of the liquidus curves is detected. (The coordinates of the eutectic point are 485°C and 14.5 at.% Cu.)...

On the basis of an IR study of some s-triazines and HA systems, several authors reported that ionic bonding took place between a protonated secondary amino group of the s-triazine and a carboxylate anion on the HA [17,146,147]. Successive studies, mainly conducted by IR spectroscopy, confirmed previous results and also provided evidence for the possible involvement of the acidic phenol-OH of HA in the proton exchange of the s-triazine molecule [17, 146-150]. Differential thermal analysis (DTA) curves measured by Senesi and Testini [146, 147] showed an increased thermal stability of the HA-s-triazine complexes, thus confirming that ionic binding took place between the interacting products. 

FIGURE 6.10. TGA and DTA curves of the Ag/Si02 sample prepared by two-step method. 

Thermogravimetric analysis (TGA) and differential thermal analysis (DTA) curves of the Ag/Si02 sample prepared by the two-step method are shown in Fig. 6.10. The TGA curve exhibits two evident weight loses, which are in the range of ca. 100 to 250°C and 250 to 550°C, corresponding to the loss of solvent, water, ethanol and THF, and the decomposition of organic silica, respectively. Four evident endothermic peaks can be observed from DTA curve, which centered at ca. 200°C, 350°C, 425°C and 480°C, respectively. 

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