Differential thermal analysis plots

Figure 7 Schematic differential thermal analysis plot (DTA).

Fig. 3 Schematic diagram illustrating the essential aspects of the differential thermal analysis technique. The experimental observable is the differential temperature between sample and reference, which will be plotted as a function of the system temperature.

Experimental Methods In Differential thermal analysis (DTA) the sample and an inert reference substance, undergoing no thermal transition in the temperature range under study are heated at the same rate. The temperature difference between sample and reference is measured and plotted as a function of sample temperature. The temperature difference is finite only when heat is being evolved or absorbed because of exothermic or endothermic activity in the sample, or when the heat capacity of the sample changes abruptly. As the temperature difference is directly proportional to the heat capacity so the curves are similar to specific heat curves, but are inverted because, by convention, heat evolution is registered as an upward peak and heat absorption as a downward peak. 

Differential thermal analysis (DTA) involves heating (or cooling) a test sample and an inert reference sample under identical conditions and recording any temperature difference which develops between them. Any physical or chemical change occurring to the test sample which involves the evolution of heat will cause its temperature to rise temporarily above that of the reference sample, thus giving rise to an exothermic peak on a DTA plot. Conversely, a process which is accompanied by the absorption of heat will cause the temperature of the test sample to lag behind that of the reference material, leading to an endothermic peak. 

Differential Thermal Analysis (DTA) — A procedure for recording the difference in temp between a substance and a reference material, against either time or temp as the two specimens are subjected to identical temp regimes in an environment heated or cooled at a controlled rate. The record is the differential thermal or DTA curve the temp difference (A T) is usually plotted on the ordinate with endothermic reactions downward and time or temp on the abscissa increasing from left to right Differential Scanning Calorimetry (DSC) —... 

Differential Thermal Analysis. A sample of film pressed in air at 200°C was heated at the rate of 10°C/minute from 25°-500°C in a nitrogen atmosphere. The Tg and the temperatures for the onset of HC1 evolution and the peak endotherm were determined from the DTA plot. 

One of the simpler ways to obtain such information is called differential thermal analysis (DTA), and a typical apparatus is described in Figure 2.37. Basically, the polymer sample P and an inert reference material R are heated from the same source. Thermocouples measure the temperature of the polymer and that of the reference, and the temperature difference AT =TP- TR is then plotted as a function of the temperature of the polymer. 

MgCOj decomposes at substantially lower temperatures the dissociation pressure reaches atmospheric pressure at 400—480 C. The reaction enthalpy is 121 kJ (28.9 kcal) per mole at 25 °C. MgC03 bound in dolomite decomposes at a temperature somewhat higher than pure MgC03. The dissociation pressures are plotted in Fig. 27. The decomposition of dolomite proceeds in two stages as illustrated by differential thermal analysis curves, showing two distinctly separate endothermal peaks for MgCOa and CaCOj respectively. The DTA curves for various minerals are shown in Fig. 28 (Ivanova et al., 1974). 

Frey s variant of the silvered vessel test has been in use in the Germany. In its variant, different amounts of heat are supplied to the electric heating elements mounted inside the Dewar flask, and the temperature differences between the interior of the Dewar vessel and the furnace are measured by thermocouples. A calibration curve is plotted from the values thus obtained, and the heat of decomposition of the propellant is read off the curve. In this way, the decomposition temperature at a constant storage temperature can be determined as a function of the storage time, and the heat of decomposition of the propellants can thus be compared with each other. If the measurements are performed at different storage temperatures, the temperature coefficient of the decomposition rate can be calculated. (-< also Differential Thermal Analysis.)... 

Differential thermal analysis (DTA) measures the temperature difference between a sample and a reference as the temperature is increased. A plot of the temperature difference (thermogram) reveals exothermic and endothermic reactions that may occur in the sample. The temperature for thermal events such as phase transitions, melting points, crystallization temperatures, and others can be determined... 

Differential thermal analysis, DTA, was also carried out to determine the optimum nucleation temperature according to the method reported by Marotta et al. who concluded that, if samples are held for the same time tn, at each heat-treatment temperature Tn, then In 1 (kinetic rate constant for nucleation) is proportional to (1/Tp) - (1/Tp ), where Tp and Tp are, respectively the crystallization exotherm temperatures obtained with and without a nucleation hold. Plotting (1/Tp) - (1/Tp ) against nucleation hold temperature gives a bell shaped curve, with the optimum nucleation... 

K. Matusita and S. Sakka, Kinetic-Study on Crystallization of Glass by Differential Thermal-Analysis - Criterion on Application of Kissinger Plot , J. Non-Cryst. Solids, 38-39, 741-46 (1980). 

The thermal behavior of coal may also be investigated by use of the differential thermal analysis method. In this technique, the differential change in temperature that occurs when a coal is heated at a given rate is noted to that for a reference material. The derivative is plotted against temperature to produce the thermogram a positive slope indicates an exothermic reaction whereas a negative slope indicates an endothermic reaction. 

The slope of the phase boundary curve dpidt can be estimated from the Ttr - Pit plot obtained by using a PVT or high-pressure differential thermal analysis (DTA) method [118,119]. The volume-dependent entropy (correction for the volume change) ASy, the transition entropy (AStr)p under ordinary pressure, and the constant-volume entropy (AStr)v obtained therefrom are arranged in this order in Tables 2,3, and 4. 

Filled PVC compounds can be flame-retarded by alumina trihydrate. Figure 5.9 shows the burning time of flame-retarded PVC plasticized by 50 phr. of di-isooctyl phthalate. Extinction time after the ignition of a horizontal rod specimen at environmental temperature of 100 or 120 °C is plotted against the additive content. In Figure 5.10, differential thermal analysis (DTA) curves of the same PVC compounds are presented. 

Differential thermal analysis curve Graphical representation of data collected by a differential thermal analyser, where the difference temperature is plotted as a function of temperature (scanning mode) or time (isothermal mode). 

The most extensively used methods for monitoring these heat induced changes in fibers are differential thermal analysis (DTA) and differential scanning calorimetry (DSC). In DTA, both sample and inert reference are heated at the same rate by the same heat source. When a thermally induced transition occurs in the sample, a temperature difference between the sample and reference results can be recognized. A plot of the difference in temperature between the two against increasing applied temperature exhibits deviations from the initial baseline, depending on... 

ETA is usually carried out in conjunction with other TA techniques, most notably differential thermal analysis (DTA) and EGA. In this context, ETA can be considered as a coupled TA technique. Carrier gas, at a constant flow rate, is used to carry released gas from the sample to appropriate detectors -usually radioactive counting devices. In the case of desorbed radon, a scintillation counter is used, whereas Geiger counters are used for krypton, xenon, and argon. A typical ETA system is shown schematically in Figure 1. An ETA curve is a plot of emanating power E as a function of time and the E/time relationship has been developed and defined by Balek. 

DTA n. Differential thermal analysis measurement of melting temperature generates a plot of heat versus temperature and semiquantiative, but higher temperature range than DSC. DTA is capable of measuring events (e.g., melting, crystallization, and decomposition) but not heat of melting or crystallization whereas DSC is quantitative and appropriate for thermally... 

Differential thermal analysis (DTA) has been used to study the effect of side-chain lengthin polymers on the melting point and the effect of heating rate of polymers on their melting point. DSC has been used to evaluate multiple peaks in polymers [12, 13]. DSC has also been used to study the heat changes occurring in a polymer as it is cooled (plots of temperatures versus heat flow). 

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