Thermogravimetric properties, correlations

Thermo-Raman spectroscopy Raman spectroscopy is a useful technique to extract information during dynamic thermal processes and this specific application is termed as thermo-Raman spectroscopy (TRS). It is possible to investigate thermally induced changes in Raman band positions, band intensities, and bandwidths and correlate with corresponding structural changes in samples. TRS can also provide quantitative information related to the dynamics thermal processes. Unlike techniques such as thermogravimetric analysis (TGA) and differential thermal analysis (DTA) which can only provide bulk information associated with thermal properties of a solid sample, TRS can be used to study thermally induced structural transformation in solids [17]. 

Data on the melt basicity estimations by the determination of acidic gases (SO3, CO2, H2O) solubilities are presented elsewhere. Sulphur trioxide solubility in molten sodium phosphate was determined by thermogravimetric analysis, the correlation between the melt basicity and the SO3 solubility was found. The use of CO2 and H2O for basicity estimation was described elsewhere. The similar methods may be used only for basic melts since acids displace the acidic gas from the melt. Furthermore, the interaction products of the acidic gas with the melt may be relatively stable, especially in basic solutions, and their formation leads to irreversible changes of the melt properties. 

Three carbon fibre-reinforced polyimides were exposed to UV radiation at 177C, at three different intensities for three different times, so that the product of intensity and time was a constant. Intensities of 1,2 and 3 suns, where one sun is the power in space at one earth-sun distance, were used, for a time periods of 500, 250 and 167 h. The samples were characterised by X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis, thermomechanical analysis and dynamic mechanical analysis. Measurement of bulk properties showed no difference between samples exposed to heat and UV radiation, and control samples. Surface analysis by XPS showed an apparent decrease in carbonyl concentration on the surface of some exposed samples. This was correlated to surface contamination by a silicone-containing material. 3 refs. 

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