Dynamic temperature-programmed thermogravimetry

The Stanton-Redcroft TG 750 thermobalance was used, applying the standard parameters heating rate = 10 K/min and a gas flow rate of 25 cmVmin. 

The TGA curves already known for bitumens were obtained. The TGA curves of B80/1 and PMB/1 are congruent up to approximately 475 °C. There is only a difference in the coking behavior (Fig. 4-83). Comparison between B200/3 and PMB/3 reveals differences the curve of PMB/3 is shifted towards lower temperatures (Fig. 4-84). This due to the 

During the experiments in air the pair B200/3 and PMB/3 shows divergence of the curves at low temperatures (Fig. 4-85). The low values of 71 % and T5 % for PMB/3 indicate loss by evaporation, prior to the start of the oxidation at approximately 330 °C. The other three pairs also have congruent curves in the oxidation experiments. 

The index numbers of the experiments in argon are listed in Table 4-113, those of the experiments in air in Table 4-114. 

The residues at 600 °C and 800 °C of the experiments in air consist of inorganic material (ash). The experiments in argon demonstrate only one DTG peak maximum for the 

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Thermal analysis iavolves techniques ia which a physical property of a material is measured agaiast temperature at the same time the material is exposed to a coatroUed temperature program. A wide range of thermal analysis techniques have been developed siace the commercial development of automated thermal equipment as Hsted ia Table 1. Of these the best known and most often used for polymers are thermogravimetry (tg), differential thermal analysis (dta), differential scanning calorimetry (dsc), and dynamic mechanical analysis (dma). 

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. 

In the direct calorimetric determination, (- AH =f nn)T), the amount adsorbed ( ta) is calculated either from the variations of the gas pressure in a known volume (volumetric determination) or from variations of the weight of the catalyst sample in a static or continuous-flow apparatus (gravimetric determination). In a static adsorption system, the gas is brought into contact with the catalyst sample in successive doses, whereas the catalyst is swept by a continuous flow in a dynamic apparatus. Comparative calorimetric studies of the acidity of zeolites by static (calorimetry linked to volumetry) and temperature-programmed (differential scanning calorimetry linked to thermogravimetry) methods of ammonia adsorption and desorption have been performed [23]. 

Such a differential heating program leads to increased sensitivity and resolution in TGA but also to a much increased time-frame for the analysis. Dynamic rate TG appears to have addressed both of these features and hence has much potential as a high resolution/ rapid thermal analysis system, which, unlike SCTA, can be applied for rapid and reproducible thermal analysis of a wide range of complex materials. Finally, modulated temperature thermogravimetrie analysis has enhanced potential for the kinetic analysis of thermal decomposition reactions over conventional TGA because of its greater resolution of thermal events. 

Thermal analysis techniques are used to study the properties of polymers, blends and composites and to determine the kinetic parameters of their stability and degradation processes.Here the property of a sample is continuously measured as the sample is programmed through a predetermined temperature profile. Among the most common techniques are thermogravimetry (TG) and differential scanning calorimetry (DSC). Dynamic mechanical analysis (DMA) and dielectric spectroscopy are essentially extensions of thermal analysis that can reveal more subtle transitions with temperature as they affect the complex modulus or the dielectric function of the material. 

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