Thermogravimetric technique

The glycolysis of PETP was studied in a batch reactor at 265C. The reaction extent in the initial period was determined as a function of reaction time using a thermogravimetric technique. The rate data were shown to fit a second order kinetic model at small reaction times. An initial glycolysis rate was calculated from the model and was found to be over four times greater than the initial rate of hydrolysis under the same reaction conditions. 4 refs. 

The generation of material vapors can be quantified in terms of 1) relationship between weight loss and sample temperature. AMTL used thermogravimetric techniques for such quantification (J ), and 2) the relationship between the generation rate of material vapors and the heat flux. Factory Mutual Research Corporation (FMRC) has developed a technique using FMRC s Small-Scale Flammability Apparatus (2-10), which was used for the quantification. 

Hirtz et al demonstrated the hygroscopic nature of neomycin sulphate using a thermogravimetric technique. In a more recent study Russian workers18 determined the adsorption of water by neomycin sulphate at temperatures of 23, 90 100 C. Table 3 gives the results... 

Thermal analysis is a group of techniques in which a physical property of a substance is measured as a function of temperature when the sample is subjected to a controlled temperature program. Single techniques, such as thermogravimetry (TG), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), dielectric thermal analysis, etc., provide important information on the thermal behaviour of materials. However, for polymer characterisation, for instance in case of degradation, further analysis is required, particularly because all of the techniques listed above mainly describe materials only from a physical point of view. A hyphenated thermal analyser is a powerful tool to yield the much-needed additional chemical information. In this paper we will concentrate on simultaneous thermogravimetric techniques. 

Table 1.4 shows that the most numerous applications of hyphenated thermogravimetric techniques for the study of elastomeric material make use of TG-DTA, followed by TG-FTIR, TG-DSC, TG-MS and TG-DTA-MS, with only occasional recourse to TG-DSC-MS and TG-GC-MS. Table 1.5 indicates the general performance characteristics of the thermogravimetric techniques in use for the study of elastomeric materials. 

Hyphenated thermogravimetric techniques have been used in a wide variety of qualitative and quantitative problem-solving cases for elastomeric materials ... 

Table 1.5 Comparison of hyphenated thermogravimetric techniques for elastomer analysis ...

Table 1.4 lists applications of various hyphenated thermogravimetric techniques for the study of elastomeric materials. 

Future Prospects of Hyphenated Thermogravimetric Techniques in Elastomer Characterisation... 

For the reasons that we have just described, the measurement of residual moisture within an isolated vial or ampoule is a difficult undertaking. Joan May, in this book, also deals with this topic and she explains how the FDA developed very accurate standardized techniques to execute these determinations by chemical Karl Fischer titration or thermogravimetric techniques. The only drawback is that, in both cases, the material is destroyed. 

Comparing the results presented in Table 2 one can conclude, that for both silicas average pore diameters and specific pore volumes estimated by using various techniques are close together. The results indicate that fast thermogravimetric technique is a useful tool for characterization of porous solids containing meso-pores. 

The kinetics of the reaction between WO 3 and COCl j have been studied by thermogravimetric techniques although the nature of the products was not investigated, they were believed to be a mixture of WOCl and WOjClj on thermodynamic grounds (also, see Section 9.2.3) [1586d]. 

As a conclusion, one can say that the thermogravimetric technique is a usefull method in the investigations of the porosity of solids. Our analysis, based on the Kelvin equation, of the thermogravimetric curves for silica gel wetted with liquid n-butanol and carbon tetrachloride leads to core/pore size distributions curves which are similar, but not identical in shape to the pore size distribution curves derived by standard procedure from low temperature nitrogen adsorption/desorption isotherms. The linear heating mode is... 

The sample buoyancy changes using high-pressure thermogravimetric techniques have already been mentioned (28). 

Mass loss can be measured as a function of temperature by thermogravimetric techniques (cf. Section 3.1.1.1) but the thermal stability under isothermal conditions is often more informative. For this reason, mass loss is frequently studied as a function of time at different temperatures as shown in Figures 3.71 and 3.72. 

The important conclusions that can be drawn from this study are (i) the concentration of the cyclic monomer (IV) formed in the flash pyrolysis of cured polysulfide polymers reflects the structure of the cured polymer (ii) thermogravimetric data could be used to find the presence of mercaptide bonds in the cured polymers and (iii) Py-GC and thermogravimetric techniques can be used to characterise insoluble polymers, which is clearly brought out in the case of manganese dioxide-cured polymer. 

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