Thermal gravimetric analysis method

The heavy metal salts, ia contrast to the alkah metal salts, have lower melting points and are more soluble ia organic solvents, eg, methylene chloride, chloroform, tetrahydrofiiran, and benzene. They are slightly soluble ia water, alcohol, ahphatic hydrocarbons, and ethyl ether (18). Their thermal decompositions have been extensively studied by dta and tga (thermal gravimetric analysis) methods. They decompose to the metal sulfides and gaseous products, which are primarily carbonyl sulfide and carbon disulfide ia varying ratios. In some cases, the dialkyl xanthate forms. Solvent extraction studies of a large number of elements as their xanthate salts have been reported (19). 

Analysis. Excellent reviews of phosphate analysis are available (28). SoHds characterization methods such as x-ray powder diffraction (xrd) and thermal gravimetric analysis (tga) are used for the identification of individual crystalline phosphates, either alone or in mixtures. These techniques, along with elemental analysis and phosphate species deterrnination, are used to identify unknown phosphates and their mixtures. Particle size analysis, surface area, microscopy, and other standard soHds characterizations are useful in relating soHds properties to performance. SoHd-state nmr is used with increasing frequency. 

In addition to these standardised test methods set by regulation (in particular the transport regulations of dangerous substances), there are laboratory methods that can provide more details regarding substance behaviour. In particular, there is differential thermal analysis (DTA), thermal gravimetric analysis, calorimetry and thermomanometry, which will not be described here. 

Major methods involved with the generation of information about thermal property behavior of materials include thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), differential thermal analysis (DTA), torsional braid analysis (TBA), thermal mechanical analysis (TMA), and pyrolysis gas chromatography (PGC). 

Other characterization methods that are of value are dynamic scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). A sample DSC is shown in the middle of Figure 15.2. Most cure reactions are exothermic, and the heat generated by cure can cause excessive heat to build up in the polymer if control is not exercised. DSC measures the generation of heat as a function of time and temperature. This can be used to predict the temperature at which the laminate will begin to cure (the onset of the peak in Fig. 15.2) and the temperature or time at which cure will be complete, further improving the selection of cure cycles to try. 

The degree of hydration of the products from these preparations and the water content given by analytical procedures depends upon the heat treatment (method and history) of the product. A sample subjected to TGA (thermal gravimetric analysis) looses water almost continually from room temperature until it becomes the completely anhydrous heteropolytungstate salt at about 400°C. On the other hand, these crystals lose some lattice water rapidly upon removal from the mother liquor and exposure to air even at room temperature. 

The use of organic components increases the discrimination in soils that are otherwise similar. For example, soils that have identical Munsell color values could be discriminated by subtractive FTIR. A new ancillary method using thermal gravimetric analysis in addition to IR analysis on samples prior to and after pyrolysis has been applied to soils and could give additional valuable information for the discrimination of soils (Thermo electron corporation application note 50862). 

Conversion of the as-deposited film into the crystalline state has been carried out by a variety of methods. The most typical approach is a two-step heat treatment process involving separate low-temperature pyrolysis ( 300 to 350°C) and high-temperature ( 550 to 750°C) crystallization anneals. The times and temperatures utilized depend upon precursor chemistry, film composition, and layer thickness. At the laboratory scale, the pyrolysis step is most often carried out by simply placing the film on a hot plate that has been preset to the desired temperature. Nearly always, pyrolysis conditions are chosen based on the thermal decomposition behavior of powders derived from the same solution chemistry. Thermal gravimetric analysis (TGA) is normally employed for these studies, and while this approach seems less than ideal, it has proved reasonably effective. A few investigators have studied organic pyrolysis in thin films by Fourier transform infrared spectroscopy (FTIR) using reflectance techniques. - This approach allows for an in situ determination of film pyrolysis behavior. 

Thermal gravimetric analysis (TGA) is undoubtedly the most widely used method of moisture content determination. The sensitivity and sophistication of TGA instruments ranges from the classical moisture balance (LOD) to specially designed microbalances enclosed in chambers that may be evacuated. Microprocessor control of the temperature increase has led to more reproducible and discriminating information. 

HPLC and GC analyses are two commonly used methods for determining the levels of impurities and residual solvent in the cake. Thermal gravimetric analysis is another very powerful tool. It detects not only the level of residual solvent, but also the temperature at which the solvent evaporates. If the cake weight loss due to solvent evaporation occurs at the melting point of the solid, this is a clear indication that solvent is trapped within the cake. 

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. 

There are several nonspecific methods available that can determine the total amount of solvent(s) in a sample. Loss on drying (LOD) determines the amount of volatile components that are released from a sample under specific temperature and/or vacuum conditions. Thermal gravimetric analysis (TGA) measures the loss of volatile components from a sample over a temperature gradient. The advantage of these methods is that they give an estimate of the volatile component content of a sample relatively quickly. The disadvantages of these methods are that they do not speciate and cannot account for volatile components that are trapped in the lattice structure of the compound. By accepting the limitations of these methods, a total solvent amount can be... 

In this chapter we investigate and discuss the thermal, optical, electrical properties of the oligothiophene derivatives by means of differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), and UV-Vis spectroscopy. The thin films of these compounds produced by solution cast and vacuum deposition methods are characterised by AFM measurements in contact and non-contact mode, and by X-ray diffraction. Finally, an ultra-thin OFET is built, and the transistor characteristics are determined. 

Thermal Gravimetric Analysis/Solvent Extractables - We have used both methods to characterize the change in curing behavior induced by varying light intensity, type and concentration of crosslink agent. 

Elemental analysis (e.a.) and thermal gravimetric analysis (t.g.a.) were used as alternative methods to calculate the percentage photoinitiator species per silica (Table II). An inaccuracy in the results of the elemental analysis is possible by the influence of cdsor)3ed ethcuiol (from the washing process) on the carlDon values. In the thermal gravimetric analysis absorbed species should be removed below 200 C,... 

TGA— Thermal gravimetric analysis, a test method by means of heating and determining loss of weight. 

Other techniques are used to identify pigments based on their molecular fragments. These techniques include UV-visible reflectance spectroscopy, infrared (IR) spectroscopy, mass spectrometry, and X-ray diffraction (XRD). Some thermal methods exploit differences in physical characteristics that are sensitive to the bulk properties of a paint sample. Differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA) are often used. Finally, separation techniques such as liquid chromatography (LC) have been used to identify a wide range of dyes. 

Quantitation provides the highest accuracy level achievable by CaCOs methods. The digestion of calcium carbonate can be determined in four different ways (1) digestion with acid (2) thermal gravimetric analysis (TGA at 105°C, 450°C, 550°C, and 1000°C... 

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