Thermogravimetric-Fourier-transform analysis

The solid-state properties like crystallinity, polymorphism (crystal structure), shape (morphology), and particle size of drugs are important in the stability, dissolution, and processibility of drugs. Some commonly used methods in solid-state studies include microscopy, hot stage microscopy with polarized light, x-ray powder diffraction (XRPD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), Fourier transform infrared FTIR/Raman, and solid-state NMR. 

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. 

Comparison of several techniques (namely Fourier transform infrared spectroscopy (FTIR), simultaneous thermogravimetric analysis-differential scanning calorimetry (TGA-DSC) and ultrasonic spectroscopy) for assessing the residual physical and mechanical characteristics of polymer matrix composites (PMCs) exposed to excessive thermal loads showed the measured power spectra of ultrasonic energy to correlate with performance of graphite fibre epoxy matrix composites exposed to thermal degradation, and also that analyses with the three techniques all pointed to the same critical temperature at which thermally induced damage increased sharply [58],... 

The catalysts were characterized by N2 adsorption-desorption isotherms, thermogravimetric analysis (TGA), temperature-programmed desorption of ammonia (NH3-TPD), X-ray diffraction (XRD), Raman spectroscopy, in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and X-ray photoelectron spectroscopy (XPS). The procedures and experimental conditions have been detailed elsewhere [9]. 

Pyrolysis of ammonia-borane is a complex process, and the products of the decomposition reaction markedly depend on the conditions employed. Furthermore, the initial process is a solid-state reaction for which the onset of decomposition is a function of heating rate of the substrate (P). In thermogravimetric analyzer-Fourier transform infrared (TGA-FTIR) and thermogravimetric analyzer-differential scanning (TGA-DSC) analysis, heating a borazane sample to 90°C at a rate of 0.5°C/ min and then holding it at that temperature for 200 min resulted in a loss of about 10.2% of initial... 

The hydrophobic matrix (pure silica) and the sol-gel-encapsulated CGTase, produced fixim the precursor TEOS were characterized by thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FTIR). 

Programmable fnmaces may be interfaced to a gas chromatograph, generally with some sort of intermediate trapping, bnt are rarely interfaced directly to spectroscopic techniqnes. Thermogravimetric analysis coupled with Fourier-transform infrared spectroscopy (TGA-FT-IR) is an important exception, since many thermal units are capable of heating samples to pyrolysis temperatnres, with the resnlting pyrolysate swept directly into the cell of the FT-IR."... 

Blends of polyethylene terephthalate and linear low-density polyethylene were compatibilised using diethylmaleate grafted polyethylene, and characterised using Fourier transform infra-red spectroscopy, thermogravimetric analysis and scanning electron microscopy. Interactions between the components in the blends were observed, which affected the glycol sequences of the polyester and also improved the thermal oxidative stability of the blends. The introduction of the compatibiliser resulted in a particle size reduction of the dispersed phase and better adhesion between the phase and the matrix. 15 refs. 

Thermogravimetric analyzers may be connected to a variety of chemical analyzers to determine the exact composition ofthe outgassed materials as they are evolved. Among chemical analysis methods are gas chromatography, infrared spectroscopy, and mass spectroscopy for example, a TGA apparatus may be coupled with a Fourier Transform Infrared (FTIR) spectrophotometer to measure the thermal oxidative stabilities of several fluorinated polyimides. 

Several typical technologies for characterization-modified LDH are introduced in this section and organic LDH modified by DBS as a model example. In detail, the technologies include wide angle x-ray scattering (WAXS), Fourier transform infrared spectra (FTIR), thermogravimetric analysis (TGA), elemental analysis (EA), and Al NMR and H MAS NMR. A comparison between modified and unmodified LDH are also shown. 

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