DTA/DSC applications

Seyler, R. J., "Applications of Pressure DTA (DSC) to Thermal Hazard Evaluation," Thermochimica Acta, 39 (1980). 

The applications of simultaneous TG-FTIR to elastomeric materials have been reviewed in the past. Manley [32] has described thermal methods of analysis of rubbers and plastics, including TGA, DTA, DSC, TMA, Thermal volatilisation analysis (TVA), TG-FTIR and TG-MS and has indicated vulcanisation as an important application. Carangelo and coworkers [31] have reviewed the applications of the combination of TG and evolved gas analysis by FTIR. The authors report TG-FTIR analysis of evolved products (C02, NH3, CHjCOOH and olefins) from a polyethylene with rubber additive. The TG-FTIR system performs quantitative measurements, and preserves and monitors very high molecular weight condensibles. The technique has proven useful for many applications (Table 1.6). Mittleman and co-workers [30] have addressed the role of TG-FTIR in the determination of polymer degradation pathways. 

DTA, DSC, and TG have become routine for monitoring polysaccharide solid-state transformations. Examples of important applications are hydra-... 

Thermal analysis involves observation of the usually very delicate response of a sample to controlled heat stimuli. The elements of thermal-analysis techniques have been known since 1887 when Le Chatelier used an elementary form of differential thermal analysis to study clays (4), but wide application did not come until the introduction of convenient instrumentation by du Pont, Perkin-Elmer, Mettler and other sources in the 1960 s. Currently, instrumentation and procedures are commercially available for DTA, DSC, TGA, TMA, and a number of so-called hyphenated methods. Several methods are currently under study by ASTM committees for consideration as to their suitability for adoption as ASTM standards. 

The application of thermogravimetry to a particular problem is possible if a mass-change is observed on the application of heat. If no mass-change is observed, then other thermal techniques such as DTA, DSC, TMA, and so on, may have to be employed. If the mass-change is very small (< 1%), then perhaps other techniques such as evolved-gas analysis (EGA) may be more useful. Mass-changes (generally mass-losses) which can be detected by TG techniques are summarized in Figure 4.1. 

More recently, Gallagher et al. (282) and Dunn (283) reviewed the applications of DTA/DSC for the study of catalytic activity and other processes. The technique is used to optimize the performance of a catalyst system to study the effects of variables such as catalyst composition, temperature, and gas flow rates on reaction rates to prepare catalysts to determine the most effective catalyst for a reaction and to find the effects of poisoning on the catalytic activity (283). 

One of the early fields of application of DTA was in the area of clays and minerals. These compounds, which gave birth to the theory and instrumentation of the technique, have been widely investigated. DTA was used to identify clays from various locations throughout the world and was widely used to determine the free quartz content of minerals. Numerous other applications were made of DTA DSC was little used due to the low-temperature capability of the latter. Most of the interesting thermal behavior of clays and minerals occur above 500°G and frequently above 1000°C. The applications of DTA to these materials is discussed by Mackenzie et al. (62, 186-188) and many others. 

Other applications of DSC and other TA techniques to the pharmaceutical industry include physico-chemical interactions (275), polymorphism in triglyceride suppository formulations (276) drug-excipient interactions (277), and many more. Reviews of the applications of DTA/DSC and different techniques to pharmaceuticals include those by Brennan (278), Daly (279), and others (280). 

Reviews of applications of DTA/DSC, and other TA techniques, to various technological areas include cements (262-264) electrical and electronics industries (265) automotive industries (266) and industrial raw materials (267). 

The main changes in this edition are as follows (1) Numerous new applications of thermal analysis techniques have been added to the chapters on TG, DTA, DSC, EGD/EGA, and others. (2) Other techniques, not used as often, are described in greater detail, such as EGD/EGA, TMA, DMA. thermoptometry, thermoelectrometry, thermosonimetry, and others. (3) The chapter on EGD/EGA has been rewritten, as has the chapter on miscellaneous techniques. (4) The determination of purity by DSC has been rewritten. (5) Commercially available instruments have been briefly described for each technique, including the application of microcomputers to many of these instruments. 

For extended applications, a DTA/DSC-EGD-GC on-line coupled simultaneous technique and relevant apparatus were established in the 1980s [63]. The CDR-1 E>SC analyzer was replaced by the Model CRY-1 DTA (ambient temperature ca 1200 C) for the purpose of high-temperature measurements. The scheme of the DTA-EGD-GC on-line coupled simultaneous apparatus is shown in Figure 2.37. DTA and a EGD-GC... 

Applications of DTA for Polymers. Table 2 (Ref 5, Chapt. l) describes some of the many applications of DTA and DSC. Both DTA and DSC can be used to determine the temperature of the transitions, cited in Table 2. However, the DSC peak area, in addition, gives quantitative calorimetric information (heat of reaction, transition, or heat capacity). DTA can only do so when calibration with a standard material allows the quantitative conversion of AT to heat flow and, ultimately, heat of transition (AH) or heat capacity (Cp). Also, the response of DTA with increasing temperature may be affected by poor heat transfer in the system, detector sensitivity, etc (4). For these reasons, when there is a choice between DSC and DTA, DSC is the preferred method. The illustrations shown below for applications of DSC in characterization of polymers also generally apply for DTA, with the limitations mentioned above. Therefore, DTA applications will not be considered here. Illustrations of polymer applications for DTA can be found in the Thermal Analysis section by Bacon Ke (6) in the previous edition of this encyclopedia. 

Solid-solid reactions have also been successfully studied by these techniques, as have decompositions of high explosives. The applicability of DTA/DSC to very small samples is of obvious value here. Similarly, preliminary screening of potentially hazardous reaction mixtures is conveniently carried out in this way as a guide to the likelihood of exothermic reaction, the corresponding temperature range and magnitude, and possible effects of pressure and atmospheric conditions (see also Section 26.2.4.5). 

Before entering the specific argumenf about the application of DTA-DSC techniques to multicomponent liquids consisting of water or oil droplets coated with a surfactant shell and dispersed into an oil or water continuous phase, we consider some technical details of these two thermal methods of analysis [2]. 

Quantitative DTA methods for untreated cotton and fabric treated with P- and N-containing flame retardants were suitable for determining the efficiency of FRs and provided data that correlated with oxygen index values [184], Childress etal. [185] described DTA, DSC and TG studies on brominated phosphite and phosphate flame refardants. Nara et al. [186] have studied pyrolysis of tetrabrominated epoxy resin and its Are retardant mechanism. Pyrolysis of DER 542 (brominated epoxy resin) and Epikote 1001 (non-brominated epoxy resin) was investigated by DTA en TG. Bhatnagar et al. [187] have reviewed DTA and DSC studies on flame retardant polymers. Carroll-Porczynski [188] described the applications of simultaneous TG and DTA and DTA/MS analysis for predicting the flame retar-dancy of composite textile fabrics and polymers. The use of DTA to identify mineral flllers in rubber formulations is as old as the technique itself [189],... 

Netzsch Geratebau GmbH, Application Note TG-DTA/DSC, MS, FTIR Coupling Systems, Selb (n.d). 

There is a wide sphere of applicability of DTA/DSC technique, which is regularly described in satisfactory details in the individual apparatus manuals or other books [1,15,602,613,640,646]. The usage can be sorted in to two classes The methods based on the (1) modified instrumentation such as (i) high-pressure studies [647] or (ii) differential hydrothermal analysis [648] and the measurements applicable under the (2) ordinary apparatus set up such (iii) determination of phase boundaries [646,649], (iv) impurity measurements [650,651] and (ivi) reaction kinetics (see previous Chapter [3,425,508-510,521]. Specifically constructed instrumentations [1,15,602] falls beyond the scope of this book so that we shall concentrate on the second type of applications. 

Let us mention here only one of the earliest applications of DTA/DSC the rapid determination of the impurity (of mostly organic compounds) without the requirement for using a reference material [650,651,662,663], The procedure for quantitative evaluation of purity is based on the thermodynamic relationship for the depression of the melting point by the presence of usually unknown contamination. For the derivation of this procedure, it is assumed that (i) the solute forms an ideal solution upon melting, (ii) the solvent and solute are immisible in the solid phase, (iii) the concentration of impurities can be expressed as a mole fraction of solute and (iv) the enthalpy of fusion of the sample is unchanging over the range of temperatures investigated. 

The DSC applications for catalytic investigations are very similar to the ones described previously for the DTA technique. However the DSC measurement gives more possibilities as described in Sect.4.3, especially for adsorption investigations under normal [57] or high pressure [51]... 

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. 

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