Characterization techniques thermal analysis

As indicated in the previous sections, the antioxidant content in plastic material is often determined by chromatographic methods. Another widely used technique for polymer characterization is thermal analysis with differential scanning calorimetry (DSC). When the oxygen induction time (OIT) for a sample containing a phenoHc antioxidant is measured, a significant oxidative exothermic response is obtained in the DSC when all the phenolic antioxidant in a sample is consumed. The OIT is thus directly related to the antioxidant content in the material and to the stabihzing function, i.e. the antioxidant efficiency in the sample, if the consumption of phenolic antioxidants obeys zero-order kinetics at the temperature used [44]. Table 1 shows the amount of the antioxidant Irganox 1081 in polyethylene (PE) determined by HPLC and extraction by microwave assisted extraction (MAE),... 

Polymer Nanocomposites Characterized by Thermal Analysis Techniques... 

ADMET polymers are easily characterized using common analysis techniques, including nuclear magnetic resonance ( H and 13C NMR), infrared (IR) spectra, elemental analysis, gel permeation chromatography (GPC), vapor pressure osmometry (VPO), membrane osmometry (MO), thermal gravimetric analysis (TGA), and differential scanning calorimetry (DSC). The preparation of poly(l-octenylene) (10) via the metathesis of 1,9-decadiene (9) is an excellent model polymerization to study ADMET, since the monomer is readily available and the polymer is well known.21 The NMR characterization data (Fig. 8.9) for the hydrogenated versions of poly(l-octenylene) illustrate the clean and selective nature of ADMET. 

We report here the results of our recent studies of poly(alkyl/arylphosphazenes) with particular emphasis on the following areas (1) the overall scope of, and recent improvements in, the condensation polymerization method (2) the characterization of a representative series of these polymers by dilute solution techniques (viscosity, membrane osmometry, light scattering, and size exclusion chromatography), thermal analysis (TGA and DSC), NMR spectroscopy, and X-ray diffraction (3) the preparation and preliminary thermolysis reactions of new, functionalized phosphoranimine monomers and (4) the mechanism of the polymerization reaction. 

Most workers in the pharmaceutical field identify thermal analysis with the melting point, DTA, DSC, and TG methods just described. Growing in interest are other techniques available for the characterization of solid materials, each of which can be particularly useful to deduce certain types of information. Although it is beyond the scope of this chapter to delve into each type of methodology in great detail, it is worth providing short summaries of these. As in all thermal analysis techniques, the observed parameter of interest is obtained as a function of temperature, while the sample is heated at an accurately controlled rate. 

Besides the prediction of calcination temperatures during catalyst preparation, thermal analysis is also used to determine the composition of catalysts based on weight changes and thermal behavior during thermal decomposition and reduction, to characterize the aging and deactivation mechanisms of catalysts, and to investigate the acid-base properties of solid catalysts using probe molecules. However, these techniques lack chemical specificity, and require corroboration by other characterization methods. 

Morita, H. and Rice, H. M. (1955). Characterization of organic substances by differential thermal analysis—General technique. Anal. Chem. 27, 336-339. 

This chapter reviews the various methods used to identify and characterize iron oxides. Most of these are non-destructive, i. e. the oxide remains unaltered while being examined. These methods involve spectroscopy, diffractometry, magnetometry and microscopy. Other methods, such as dissolution and thermal analysis destroy the sample being examined. Only the principle of each method is given here. The main weight is put on the information about Fe oxides which can be extracted from the analytical results obtained by the different techniques together with references to relevant studies. A detailed description of each technique can be found in the appropriate texts listed in each section. 

Although a number of secondary minerals have been predicted to form in weathered CCB materials, few have been positively identified by physical characterization methods. Secondary phases in CCB materials may be difficult or impossible to characterize due to their low abundance and small particle size. Conventional mineral identification methods such as X-ray diffraction (XRD) analysis fail to identify secondary phases that are less than 1-5% by weight of the CCB or are X-ray amorphous. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM), coupled with energy dispersive spectroscopy (EDS), can often identify phases not seen by XRD. Additional analytical methods used to characterize trace secondary phases include infrared (IR) spectroscopy, electron microprobe (EMP) analysis, differential thermal analysis (DTA), and various synchrotron radiation techniques (e.g., micro-XRD, X-ray absorption near-eidge spectroscopy [XANES], X-ray absorption fine-structure [XAFSJ). 

Thermal analysis can be used to characterize the physical and chemical properties of a system under conditions that simulate real world applications. It is not simply a sample composition technique. 

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