Derivative thermogravimetric

Thermal Analyses. Thermal techniques such as differential thermal analysis, thermal gravimetric analysis, and derivative thermogravimetric analysis have been successfully applied to characterizing various minerals in coal (58). The methods are based on measurements of weight loss or heat transfer during phase changes at temperatures from ambient to over 1000° C. 

The curve is the derivative thermogravimetric or DTG curve the derivative should be plotted on the ordinate with weight losses downward, and t or T on the abscissa increasing from left to right... 

Frequendy, it is not easy to determine the temperatures Ti,T2,..., owing to the nearly horizontal nature of the curve in those regions and the attendant indistinct beginning and ending temperatures of the reaction steps. This means also that it is not easy to determine accurately the mass loss in such cases. Because of this, some instruments also compute the trace of the first derivative of the mass curve simultaneously. This DTG (derivative thermogravimetric analysis) makes it much easier to determine where a zero slope indicates that the sample is undergoing no change in mass. Therefore, the reaction stoichiometry can be more accurately determined. 

A study of the relaxational transitions and related heat capacity anomalies for galactose and fructose has been described which employs calorimetric methods. The kinetics of solution oxidation of L-ascorbic acid have been studied using an isothermal microcalorimeter. Differential scanning calorimetry (DSC) has been used to measure solid state co-crystallization of sugar alcohols (xylitol, o-sorbitol and D-mannitol), and the thermal behaviour of anticoagulant heparins. Thermal measurements indicate a role for the structural transition from hydrated P-CD to dehydrated P-CD. Calorimetry was used to establish thermodynamic parameters for (1 1) complexation equilibrium of citric acid and P-CD in water. Several thermal techniques were used to study the decomposition of p-CD inclusion complexes of ferrocene and derivatives. DSC and derivative thermogravimetric measurements have been reported for crystalline cytidine and deoxycytidine. Heats of formation have been determined for a-D-glucose esters and compared with semiempirical quantum mechanical calculations. ... 

Thermogravimetric and derivative thermogravimetric curve of PVC. (Reprinted from Ref. 65, Copyright 1991, with permission from Elsevier Science.)... 

Thermal Data Obtained from Derivative Thermogravimetric Analysis (TGA) Curve of Polymethyl Methacrylate (PMMA), Ethylene Methacrylate (EMA), and Their Blends... 

Derivative thermogravimetric (DTG) curve Graphical representation of the data collected by a thermobalance, where the rate of change of mass with respect to temperature (or time) is plotted as a function of temperature (scanning mode) or time (isothermal mode). 

The decomposition temperature is a direct measure of the thermal stability of the nanocomposite materials. The derivative thermogravimetric analysis profile (DTA) (the inset of Figure 12.6a) shows two decomposition temperatures Tn and 7 2) for all the P3HT nanocomposites. The third decomposition temperature (7 ) assigned to MWNTs is visible only in the PM-5 and PM-10 samples. Tn originates... 

The thermal behavior of starch-based composites includes glass transition and thermal decomposition. Glass transition (Tg) is characterized by dynamic mechanical analysis (DMA), dynamic mechanical thermal analysis (DMTA), and differential scanning calorimetry (DSC). Thermal decomposition is determined by using thermogravimetric analysis (TGA) and derivative thermogravimetric analysis (DTG). 

Figure 14.1 Thermogravimetric analysis (TGA)/derivative thermogravimetric (DTG) curves of PPG with molecular weights of (a) = 26,900, and (b) M =...

Differential scanning calorimetry/calorimeter Differential thermal analysis Derivative thermogravimetric Differential temperature under load Divinylbenzene... 

To evaluate the apparent activation energy, the isoconversional methods are use as suitable analysis procedures. These methods are based on the assumption that at a constant extent of conversion degree (a), the decomposition rate da/dt is a function only of the temperature. In methods developed by Friedman and Flynn-Wall-Ozawa, linear functions are obtained from which slopes the apparent activation energy at constant conversion a is achieved. In the free kinetic method set by Kissinger is calculated from the slope of the linear function takes into consideration the relationship between the heating rate and peak temperature of the first-derivative thermogravimetric curve [97]. 

Figure 1. Comparison of formalized differential thermal (a) and derivative thermogravimetric (b) curves for the same hypothetical materials at identical heating rates, showing the various attributes of the peaks.

These points are clearly illustrated in Figure 3, which shows differential thermal, derivative thermogravimetric, and thermogravimetric curves for several minerals. 

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