Concurrent thermal analysis

Smolder propagation is generally treated as a flame spread problem, thus, a similar thermal analysis to the one presented in Section 3.5.5.1 is conducted for both opposed and concurrent smoldering. Many expressions for a smoldering propagation velocity can be found in the literature. Here, we will use only the one presented by Torero et al. for illustration [27] ... 

A popular and useful device is a combined DTA/TG (simultaneous thermal analysis STA) system in which both thermal and mass change effects are measured concurrently on the same sample. An example STA study comprising DTA, TG, and DTG for the decomposition of calcium oxalate is shown in Figure 5.7. 

Although the principal thermal analysis techniques are thermogravimetry, differential thermal analysis, and differential scanning calorimetry (see Chapter 1), there are a number of other thermal techniques, besides those discussed elsewhere in this book, that are useful for solving chemical and technological problems. Some of these methods are of recent development and hence little used at the present time, but they possess the potential for wider use in the future. Many of these techniques are employed to supplement or complement the three principal techniques of TG. DTA. and DSC, either in the simultaneous (single sample) or concurrent multiple samples) modes. 

The application of dielectric constant techniques to thermophysical measurement of solids has been used for a number of years (114, 115). The early uses of the technique involved isothermal measurements employing bridge methods. Recently, techniques have been developed that permit the measurement of the dielectric constant of a solid as a function of temperature, in a manner similar to other TA techniques. Chiu (116) used the term dynamic electrothermal analysis (ETA) to describe the measurement of both the capacitance and the dissipation factor of polymeric samples. Nottenburget al (117) developed an automated technique that permitted the rapid determination of the dielectric properties of a substance over a wide range of temperature and frequencies. This technique, which was called dynamic dielectric analysis (DDA), was modified to measure concurrently the DTA curve of the sample as well (117, 118). This new technique was called dynamic dielectric analysis-differential thermal analysis, DDA-DTA,... 

PP/PA-6 maleated-PP (PP-MA) Thermal analysis and optical microscopy. One or two crystallization peaks were affected by PP-MA. T of PA-6 initially decreased Uien leveled off with PP-MA content, whereas that of PP was not affected. Blends with PP-MA showed concurrent crystallization at the T of PP. Moon et ah, 1994... 

This synthesis of monopyridineiodine(I) chloride, the most stable member of the series, is based on the work of Williams.Because of its extremely low conductivity in pyridine solution, he considered the compound to be a nonelectrolyte, [CsHsN-I-Cl], a structure in which the iodine atom becomes dicovalent by absorption of two of its valence electrons into its core. On the other hand, physicochemical studies (conductivity, thermal analysis, and electrolysis of the system iodine(I) chloride-pyridine led Fialkov and Muzyka to formulate the compound as an electrolyte, [C6H5N I] C1, in concurrence with an earlier view of Audrieth and Birr. Both views agree that the compound contains unipositive iodine. Fialkov and Muzyka report the existence of another compound, C5H6N-2IC1, which they formulate as [C5H5N I]+ICl2 . 

Differential thermal analysis (DTA) n. An analytical method in which the specimen material and an inert substance are heated concurrently in separate minipans and the difference in temperature between the two is recorded, along with the temperature of the inert substance (Gooch, 1997). DTA has been useful in the study of phase transitions and curing and degradation reactions in polymers. An example of a DTA thermogram is shown. An example of a DTA instrument is the Perkin-Elmer Diamond TG/DTA (courtesy of Perkin-Elmer Inc, New York). 

DSC Modifications and Simuitaneous Techniques. DSC and other thermal analysis instrumentation have imdergone many modifications and developments in recent years. Among these innovations is the coupling of various methods. In this context the terms parallel, concurrent, and simultaneous should be defined. Parallel techniques use separate samples, each in its own imique thermal environment. Concurrent or combined techniques also use separate samples, but the experiment is carried out in a common atmosphere and thermal environment. Simultaneous techniques use the same sample in the same atmospheric and thermal environment. Such methods are increasing in popularity. While a detailed treatment of this topic is outside the scope of this discussion, a brief list will be presented in order to provide input for those new to the subject area. Interested readers should consult the chapter by Gallagher (5) and the additional references mentioned therein. 

Copolymers of PBS and butylene adipate, PBSA, have been largely used to prepare bionanocomposites [338-343]. Ray and Bousmina [338] prepared PBSA/layered silicate nanocomposites by melt extrusion of PBSA and commercially available OMMT. They showed that increasing the level of interactions (miscibihty) between the organic modifier and PBSA matrix, increased the tendency of the sihcate layers to delaminate and distribute nicely within the PBSA matrix. Thermal analysis revealed that the extent of crystallinity of PBSA matrix was directly related to the extent of exfoliation of silicate layers in the nanocomposites and DMA and tensile property measurements showed concurrent improvement in mechanical properties when compared to the neat PBSA and the extent of improvement is directly related to the extent of delamination of silicate layers in the PBSA matrix. DMA also revealed remarkable increase in flexural storage modulus when compared with that of neat PBSA. Tensile properties were also improved with nanoclay addition [339], therefore in agreement with other studies reported in the literature for similar systems [344-347]. 

Hall and Cassel describe a complete, commercially available experimental system for detailed studies of the thermal history and other characteristics of fibers, a common form of evidence material. The Bureau of Alcohol, Tobacco, and Firearms has developed a large library of inks of known manufacture dates and reports excellent cooperation from industry in its tagging project (Brunelle and Cantu). Again, the application of a well established technique (in this case thin-layer chromatography, which is sensitive enough to allow concurrent handwriting and other supportive analysis) proves its value not only operationally but also from the viewpoint of legal admissibility (Brunelle and Cantu). 

In summary, high pressure liquid chromatography can be used not only in the analysis of nucleotides, but in the analysis of almost any biologically active compound. It is especially useful for the separation of those thermally-labile, non-volatile, polar cell components and drugs that are difficult to measure by other methods (14). In addition, drugs and their metabolites can be monitored concurrently with the effects of these drugs on the naturally occurring cell constituents. Therefore, this instrument is a valuable addition to any well equipped biomedical laboratory for use by itself or in combination with other available techniques. 

In addition to the individnal techniqnes cited above, there are sitnations where individnal samples are snbjected to a common atmosphere and thermal environment. This is referred to as a concurrent analysis. An example of this is the combined DTA and TGA measin-ement, where two separate measurement devices share the same oven. In some cases two or more measnrements are performed on the same sample. There is also the possibility of interfacing several techniqnes, such as TGA combined with some form of evolved gas analysis snch as gas chromatography, Mass Spectrometry (qv), or infrared spectroscopy (or some combination of these) (see Chromatography, AFPmiTY Vibrational Spectroscopy). This situation is referred to as coupling or a coupled technique. Since the possibilities for interfacing several analytical techniques are quite large, conciurent or coupled techniques will not be considered further in this presentation. 

Once a geometric model of data base is created it may be shared for many of the product development steps described earlier. The data base may be copied and scaled for shrink factors to enable a mold designer to do preliminary mold design, or an engineer can use the same data base to perform structural analysis. Numerical control tool paths may be developed concurrently with the final mold design. Such modeling tools as finite element analysis, mold fill, and mold thermal... 

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