Thermogravimetry - Fourier Transform Infrared Spectroscopy

The applications of simultaneous TG-FTIR to elastomeric materials have been reviewed in the past. Manley [32] has described thermal methods of analysis of rubbers and plastics, including TGA, DTA, DSC, TMA, Thermal volatilisation analysis (TVA), TG-FTIR and TG-MS and has indicated vulcanisation as an important application. Carangelo and coworkers [31] have reviewed the applications of the combination of TG and evolved gas analysis by FTIR. The authors report TG-FTIR analysis of evolved products (C02, NH3, CHjCOOH and olefins) from a polyethylene with rubber additive. The TG-FTIR system performs quantitative measurements, and preserves and monitors very high molecular weight condensibles. The technique has proven useful for many applications (Table 1.6). Mittleman and co-workers [30] have addressed the role of TG-FTIR in the determination of polymer degradation pathways. 

Some general applications of TG-FTIR are evolved gas analysis, identification of polymeric materials, additive analysis, determination of residual solvents, degradation of polymers, sulphur components from oil shale and rubber, contaminants in catalysts, hydrocarbons in source rock, nitrogen species from waste oil, aldehydes in wood and lignins, nicotine in tobacco and related products, moisture in pharmaceuticals, characterisation of minerals and coal, determination of kinetic parameters and solid fuel analysis. 

Curing reactions Vulcanisation reactions Isothermal ageing Product stability Thermal degradation Identification of processing aids Plasticisers Mould lubricants Blowing agents Antioxidants Flame retardants Safety concerns 

Product safety Product liability Fire hazards 

TG-FTIR of a silicone O-ring under nitrogen showed formaldehyde and hexamethylcyclotrisiloxane at 450 °C, and a hexamethylcyclotrisiloxane octamethylcyclotetrasiloxane mixture up to 550 °C [33]. Brame [37] used TG-FTIR for 

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Thermogravimetry-Fourier Transform Infrared Spectroscopy (TG-FTIR)... 

The flame retardant mechanism of PC/ABS compositions using bisphenol A bis(diphenyl phosphate) (BDP) and zinc borate have been investigated (54). BDP affects the decomposition of PC/ABS and acts as a flame retardant in both the gas and the condensed phase. The pyrolysis was studied by thermogravimetry coupled with fourier transform infrared spectroscopy (FUR) and nuclear magnetic-resonance spectroscopy. Zinc borate effects an additional hydrolysis of the PC and contributes to a borate network on the residue. 

When decomposition is evidently not simple, with two or more processes being observed to overlap, sufficient information must be obtained to enable the contributions from each of the participating reactions, including secondary reactions between products, to be distinguished. Use of mass spectrometry or Fourier transform infrared spectroscopy coupled with thermogravimetry (see below) allows the evolution of individual gaseous species to be measured as functions of time or temperature. 

The conventional thermoanalytical techniques (thermogravimetry TG, differential scanning calorimetry DSC, differential thermal alysis DTA, etc.) can provide fundamental data concerning the thermal behaviour of these substances, but the addition of mass spectrometry (TG-MS) or Fourier transform infrared spectroscopy (TG-FTIR) has permitted the identification of gaseous species evolved during thermal processes. 

Zou, H., Yi, C., Wang, L., Liu, H., Xu, W., 2009. Thermal degradation of poly(lactic acid) measured by thermogravimetry coupled to Fourier transform infrared spectroscopy. J. Therm. Anal. Calorim. 97, 929-935. 

Reports on the detailed thermal behaviour of PEEK/HAp composites [as well as other polymer/HAp (nano)composites] are scarce in the literature. Advanced thermal analysis methods, e.g., modulated temperature differential scanning calorimetry (MTDSC) or hyphenated thermoanalytical methods such as thermogravimetry coupled with Fourier transform infrared spectroscopy (TG-FTIR) or mass spectrometry... 

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. 

Often substances may crystallize as solvates or hydrates. A very convenient way to assess if a solvate or hydrate has been obtained is thermogravimetry (TG). In such an instmment, the sample is heated in an open sample pan while its mass is measured. During the measurement, a weak nitrogen flow (in the order of 10 ml/min) is applied over the sample. When the solvent evaporates, a mass loss is detected. In case the solvent molecule is bound in the crystal lattice and is not just present on the surface of the particles, the mass loss typically occurs above the boiling point of the respective solvent. Even more useful are TG-FTIR or TG-MS instruments, where the nature of the emitted gas is determined by Fourier transform infrared (FTIR) or mass spectroscopy (MS) (Figure 8.10). This also allows the detection of thermal decomposition of the sample. 

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