Differential thermal analysis temperature

Thermal analysis iavolves techniques ia which a physical property of a material is measured agaiast temperature at the same time the material is exposed to a coatroUed temperature program. A wide range of thermal analysis techniques have been developed siace the commercial development of automated thermal equipment as Hsted ia Table 1. Of these the best known and most often used for polymers are thermogravimetry (tg), differential thermal analysis (dta), differential scanning calorimetry (dsc), and dynamic mechanical analysis (dma). 

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. 

Thermal Properties. The thermal stabiUty of cellulose esters is deterrnined by heating a known amount of ester in a test tube at a specific temperature a specified length of time, after which the sample is dissolved in a given amount of solvent and its intrinsic viscosity and solution color are deterrnined. Solution color is deterrnined spectroscopically and is compared to platinum—cobalt standards. Differential thermal analysis (dta) has also been reported as a method for determining the relative heat stabiUty of cellulose esters (127). 

Differential thermal analysis curves of iUite show three endothermic peaks in the ranges 100—150, 500—650, and at about 900°C, and an exothermic peak at about 940°C, or immediately following the highest endothermic peak. Minerals formed from iUite at high temperature vary somewhat with the... 

A variety of instmmental techniques may be used to determine mineral content. Typically the coal sample is prepared by low temperature ashing to remove the organic material. Then one or more of the techniques of x-ray diffraction, infrared spectroscopy, differential thermal analysis, electron microscopy, and petrographic analysis may be employed (7). 

In given work the possibilities enumerated above of varieties of thermal analysis used to reseai ch of solid solutions of hydrated diphosphates with diverse composition. So, for example, the results of differential-thermal analysis Zn Co j P O -SH O showed, that it steady in the time of heating on air to 333 K. A further rise of temperature in interval 333 - 725 K is accompanied with the masses loss, which takes place in two basic stages, registered on crooked TG by two clear degrees, attendant to removal 4,0 and 1,0 mole H O. On crooked DTA these stages dehydration registers by two endothermic effects. In interval 603 - 725 K on crooked DTA is observed an exothermal effect. 

Differential thermal analysis (DTA) Onset temperature of exotherms, heat of reaction, Cp, approximate kinetics... 

What are the consequences What is the maximum pressure Vapor pressure of solvent as a function of temperature Gas evolution Differential Thermal Analysis (DTA) / Differential Scanning Calorimetry (DSC) Dewar flask experiments... 

The procedures of measuring changes in some physical or mechanical property as a sample is heated, or alternatively as it is held at constant temperature, constitute the family of thermoanalytical methods of characterisation. A partial list of these procedures is differential thermal analysis, differential scanning calorimetry, dilatometry, thermogravimetry. A detailed overview of these and several related techniques is by Gallagher (1992). 

Reactivity (instability) information Acceleration rate calorimetry Differential thermal analysis (DTA) Impact test Thermal stability Lead block test Explosion propagation with detonation Drop weight test Thermal decomposition test Influence test Self-acceleration temperature Card gap test (under confinement) JANAE Critical diameter Pyrophoricity... 

Fig. 7.10. The solid state reactivity of shock-modified zirconia with lead oxide as studied with differential thermal analysis (DTA) shows both a reduction in onset temperature and apparent increase in reaction rate. The shock-modified material has a behavior much like the much higher specific surface powder shown in B (after Hankey et al. [82H01]).

Low-Temperature Differential Thermal Analysis of Hydroxy-Terminated and Carboxy-Termi-nated Polybutadiene , Rept No CRREL-SR-149 (1970) 7a) H.F. Mark, Ed, Encyclopedia of... 

The techniques referred to above (Sects. 1—3) may be operated for a sample heated in a constant temperature environment or under conditions of programmed temperature change. Very similar equipment can often be used differences normally reside in the temperature control of the reactant cell. Non-isothermal measurements of mass loss are termed thermogravimetry (TG), absorption or evolution of heat is differential scanning calorimetry (DSC), and measurement of the temperature difference between the sample and an inert reference substance is termed differential thermal analysis (DTA). These techniques can be used singly [33,76,174] or in combination and may include provision for EGA. Applications of non-isothermal measurements have ranged from the rapid qualitative estimation of reaction temperature to the quantitative determination of kinetic parameters [175—177]. The evaluation of kinetic parameters from non-isothermal data is dealt with in detail in Chap. 3.6. 

In differential thermal analysis, a sample and reference material are placed in the same large metal heat sink. Changes in the heat capacity of the sample are measured by changes in temperature between the sample and the reference materials as they are heated at the same rate. 

The thermal stability of peroxides can be expressed in terms of their half-hfe (ti/a)- Half-life values can be estimated in solution utilizing the technique of differential thermal analysis. These values, or more precisely the temperatures at which their half-life is equivalent, provide an indication of practical vulcanization temperatures [49] (Table 14.29). 

Thermal properties of several chlorinated phenols and derivatives were studied by differential thermal analysis and mass spectrometry and in bulk reactions. Conditions which might facilitate the formation of stable dioxins were emphasized. No two chlorinated phenols behaved alike. For a given compound the decomposition temperature and rate as well as the product distribution varied considerably with reaction conditions. The phenols themselves seem to pyro-lyze under equilibrium conditions slowly above 250°C. For their alkali salts the onset of decomposition is sharp and around 350°C. The reaction itself is exothermic. Preliminary results indicate that heavy ions such as cupric ion may decrease the decomposition temperature. 

Succinonitrile that is kept at a temperature of 80°C for forty six hours caused a violent decomposition, after being heated to 195°C to eliminate some compound solidified in a pipe. Differential thermal analysis showed that the reaction was self-accelerated with a period of induction of thirty three hours at 200°C and an hour and a half at 280 C. No heat was given off during the period of induction. Once started, the decomposition is very fast and there is no inhibitor. The cyanide ion shortens the period of induction. 

Dimethyiacetamide (DMA) behaves the same way the interaction exothermicity is higher than with DMF. A differential thermal analysis of the 1 1 mixture of DMA/CCI4 shows two exothermic peaks at 91-97 and 97-172°C (maximum at 147°C), respectively. An experiment made in an autoclave shows that the final temperature reaches 450°C and a pressure of 12.8 bar that is bonded to a substantial gas release. If 1 % of iron is present, the first exotherm occurs at 71 C. 

Differential Thermal Analysis (DTA). One of the characteristics of a rubber useful in tire rubber compounds is that it is amorphous at room temperature but readily undergoes strain induced crystallization. For this reason, copolymers were prepared in order to appropriately adjust the crystalline melt temperature. 

Differential thermal analysis (DTA) is the monitoring of the difference in temperature between a sample and a reference as a function of temperature [42], Differences in temperature between the sample and reference are observed when changes occur that require a finite heat of reaction. If AH is positive (endothermic reaction), the temperature of the sample will lag behind that of the reference. If the AH is negative (exothermic reaction), the temperature of the sample will exceed that of the reference. Differential thermal analysis is not normally used for quantitative work instead it is used to deduce temperatures associated with thermal events. 

---