TGA curve

The definition of polymer thermal stabiUty is not simple owing to the number of measurement techniques, desired properties, and factors that affect each (time, heating rate, atmosphere, etc). The easiest evaluation of thermal stabiUty is by the temperature at which a certain weight loss occurs as observed by thermogravimetric analysis (tga). Early work assigned a 7% loss as the point of stabiUty more recentiy a 10% value or the extrapolated break in the tga curve has been used. A more reaUstic view is to compare weight loss vs time at constant temperature, and better yet is to evaluate property retention time at temperature one set of criteria has been 177°C for 30,000 h, or 240°C for 1000 h, or 538°C for 1 h, or 816°C for 5 min (1). 

Fig. 15. TGA curve of pure waxy starch and Ag-waxy starch nanocomposites with different concentrations of silver ion precursor (moles of AgN03)...

Fig. 2. Typical TGA curve and rate of conversion for the pyrolysis of waste PSP (heating rate = 10°C/min).

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

Tlie TGA curves of the "graft" polymer and the "in situ" polymer are different as well. Noteworthy in the former is a small weight loss between 100°C and 200°C, which begins at around 100°C. This initial... 

Figure 42 TGA curves for the good sample (lower, thick line) and the cracked sample (upper, thin line).

The decomposition temperature (Td) measured at maximum rate of heat loss from TGA curves was as follows ... 

Thus, we have chosen the alternating copolymer of DMBZMA with MST as our resist material for its high thermal stability (Tg=210°C). TGA curves of the DMBZMA-MST copolymers are compared with that of PDMBZMA in Figure 5. Although incorporation of MST does not affect the deprotection temperature, the copolymers exhibit lower main chain stability than PMAN (PDMBZMA becomes PMAN above 260°C) and behave like PMMA and poly(a-methylstyrene) in terms of their main chain stability. 

The mechanism of the action of the phosphonate as a flame retardant is generally believed to be decomposition into acid fragments which contribute to char formation. These acidic species catalyze decomposition of the polyester, and give rise to species which on reaction with the phosphorus moiety cause char formation. TGA curves of the copolymers confirm that the incorporation of phosphorus into the polymer increases the char residue (Figure 4). These curves, however, show little evidence that the presence of phosphorus has any effect upon the temperature or rate of decomposition of the polyester. The curves are all fairly similar up to about 450°C. After that point, the amount of residue is proportional to the amount of phosphorus in the terpolymer. 

At the other end of the temperature spectrum, with high thermal stability of siloxane-modified poly(arylene carbonates) also a desired property, the onset of thermal decomposition (40) for polymers 1-12 was found to be in the range of 385-456°C (as determined from TGA curves obtained by heating polymer samples in nitrogen at a heating rate of 20°C/min.). There does not appear to be any pronounced trend in regard to variation of the thermal stability with structure in polymers 1-12. The small differences in the values of T for these polymers can be due... 

Fig. 14.22 (a) TGA curves of carbon-supported materials with or without cobalt obtained in nitrogen atmosphere (b) Chronoamperometry results for Ppy-C-Co, P3MT-C-CO and Ppy-C in 0.5 M H2S04 under oxygen (Reprinted from [221] with permission from Elsevier). 

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. 

Aminopolysaccharides 9 and 10 can be expected to have unusual properties because of the hyperbranched structure. The thermal properties of 9 and 10 were examined (Figure 2) by thermogravimetric analysis (TGA). The TGA curve of 9 shows that decomposition of the tosyl group started at 166°C and showed a 45% weight loss up to 337°C. The residual material exhibited thermal resistance above 337°C, but a second weight loss occurred at... 

C. Decomposition was complete at 600°C. As shown in Figure 2, the thermal decomposition of 10 occurred gradually with 65% residual weight still observable at 600°C. The TGA curves of 9 and 10 indicated that the thermal stabilities of the present hyperbranched aminopolysaccharides were much higher than those of normal linear polysaccharides. For example, chitin showed a significant weight loss at 275 28°C. 

The copolymer compositions were studied by elemental microanalyses and H-NMR, revealing that the content of the copolymer units is in aU cases very similar to that of their corresponding feed. The PU(DiT-HDl) homopolymer exhibited a high crystallinity, but the introduction of the arabinitol-based diols led to a reduction in the crystallinity of the copolymers. In their TGA curves, the copolymers exhibited a mixed trend of the related homopolymers, and all of them were thermally stable, with degradation temperatures above 220°C. The degradation... 

TGA. Thermogravimetric analysis (TGA) and differential thermal analysis (DTA) are other means to confirm the above structural models. Figure 4.4.8 shows the thermal analysis data for sample I. Curve (a) shows a TG datum of a mass loss about 22% after heating over 350°C. The derivative curve (b) of mass loss curve (a) clearly shows that there are at least four steps during the decomposition of the sample. This finding was further confirmed by the DTA data curve (c) shown in the same figure. It is clearly seen that there are four endothermic peaks. The DTA and TGA curves were similar for all samples. Note that the relative ratios of mass... 

The results obtained are consistent with the existing views on the tendency of polyconjugated systems towards spontaneous stabilization upon thermal treatment heating makes the system more resistant to thermal degradation. TGA curves (Fig. 4.2) of the samples subjected to thermal treatment at 200 and 350°C are shifted to higher temperatures, with retention of the general pattern of weight loss. Thus, the carbon-rich structures were formed at relatively low temperatures. 

A TGA curve has limited ability to identify the sample or determine its composition if its nature is unknown. However, there are still many unique analytical applications based on TGA. Two primary applications are qualitative identification and compositional analysis. 

Fig. 15.2 Superimposed TGA curves of several polymers, ramp = 10°C/min, room temperature to 800°C, nitrogen gas purge.

Fig. 15.6 TGA curve of poly(styrene) from room temperature to 800°C with a 10°C/min ramp under nitrogen gas purge.

Amount of deposited material - The thermogravimetric curves of uncoated sulfur and sulfur encapsulated with different plasma polymers are given in Fig. 12. The weight losses in the TGA curves of the different encapsulated sulfur powders are all shifted to a higher temperature compared to uncoated sulfur. The... 

Onset is defined as the intersection of the tangents to the TGA curve of the pre-degradation region and region of steep decline. 

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