Hyphenated thermal analysis Applications

Apart from combined TA techniques (on-line or not) the actual trends in thermal analysis are the introduction of modulated and high-resolution techniques, hyphenated thermal analysis methods e.g. TG-FTIR, TG-MS, DSC-XRD, etc.), alternative heating modes, microthermal analysis methods, industrial standardisation and quality control. Modulation means a periodic perturbation of a temperature program. Temperature modulation finds application in DSC, TG, DETA, TMA and uTA. Temperature-modulated techniques, such as Modulated DSC (MDSC ) and Modulated TGA (MTGATM), broaden the insight into the material properties. The use of modulated temperature programs in thermal methods has been reviewed [37,37a]. 

The thermal characterisation of elastomers has recently been reviewed by Sircar [28] from which it appears that DSC followed by TG/DTG are the most popular thermal analysis techniques for elastomer applications. The TG/differential thermal gravimetry (DTG) method remains the method of choice for compositional analysis of uncured and cured elastomer compounds. Sircar s comprehensive review [28] was based on single thermal methods (TG, DSC, differential thermal analysis (DTA), thermomechanical analysis (TMA), DMA) and excluded combined (TG-DSC, TG-DTA) and simultaneous (TG-fourier transform infrared (TG-FTIR), TG-mass spectroscopy (TG-MS)) techniques. In this chapter the emphasis is on those multiple and hyphenated thermogravimetric analysis techniques which have had an impact on the characterisation of elastomers. The review is based mainly on Chemical Abstracts records corresponding to the keywords elastomers, thermogravimetry, differential scanning calorimetry, differential thermal analysis, infrared and mass spectrometry over the period 1979-1999. Table 1.1 contains the references to the various combined techniques. 

Spectroscopy has become a powerful tool for the determination of polymer structures. The major part of the book is devoted to techniques that are the most frequently used for analysis of rubbery materials, i.e., various methods of nuclear magnetic resonance (NMR) and optical spectroscopy. One chapter is devoted to (multi) hyphenated thermograviometric analysis (TGA) techniques, i.e., TGA combined with Fourier transform infrared spectroscopy (FT-IR), mass spectroscopy, gas chromatography, differential scanning calorimetry and differential thermal analysis. There are already many excellent textbooks on the basic principles of these methods. Therefore, the main objective of the present book is to discuss a wide range of applications of the spectroscopic techniques for the analysis of rubbery materials. The contents of this book are of interest to chemists, physicists, material scientists and technologists who seek a better understanding of rubbery materials. 

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. 

HPLC has been applied to lipid analysis mainly in consideration of the necessity to avoid high temperatures, so at the very beginning, its applications dealt with thermally unstable molecules (e.g., tocopherols, phenolics, oxidation products) and often it was used as an ancillary technique, as a preparative step prior to MS analysis. The limits were in the high volume of the HPLC band that strongly limited the possibility to transfer it to a GC or to a MS. Only in the last 20 years or somewhat less, this kind of hyphenation has become commercially available. 

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