Thermogravimetric analysis atmospheres

Dyszel (1985) performed a thermogravimetric analysis/atmospheric-pressure chemical-ionization mass spectrometry (TGA/APCIMS) on green coffee beans. Using various combinations of 14 (M+1) ions, the author concluded that unknown coffees can be matched, with varying degrees of certainty, to known coffees for their country of origin. 

This was mentioned by Dyszel (1985) as found to be present in green coffee when trying to find a way for differentiating coffees of various origins. One of the ions (M+l) studied by thermogravimetric analysis/ atmospheric pressure chemical ionization mass spectrometry is 149 but the molecular weight of coumarin is 146. It is therefore difficult to determine where the error is. 

Dyszel S.M. (1985) Characterization of green coffee beans by combined thermogravimetric analysis/atmospheric pressure chemical ionization mass spectrometry. Thermochimica Acta 87, 89-98. 

The definition of polymer thermal stabiUty is not simple owing to the number of measurement techniques, desired properties, and factors that affect each (time, heating rate, atmosphere, etc). The easiest evaluation of thermal stabiUty is by the temperature at which a certain weight loss occurs as observed by thermogravimetric analysis (tga). Early work assigned a 7% loss as the point of stabiUty more recentiy a 10% value or the extrapolated break in the tga curve has been used. A more reaUstic view is to compare weight loss vs time at constant temperature, and better yet is to evaluate property retention time at temperature one set of criteria has been 177°C for 30,000 h, or 240°C for 1000 h, or 538°C for 1 h, or 816°C for 5 min (1). 

The thermal degradation of TsHs and other TsRs species (R = Me, /Bu, nCsHiy, Ph) in air and an inert atmosphere has been studied by thermogravimetric analysis and shows that for TsHs incomplete sublimation tends to occur, and, in air, oxidation competes with volatalization. ... 

Thermogravimetric analysis (TGA) of these poly(phosphazenes) shows their decomposition onset temperatures in an inert atmosphere to be ca. 350 to 400°C, depending on the side group. These temperatures are ca. 25-75°C higher than that reported for commercial materials based on the fluoroalkoxy substituted polymer, [(CFgCHjO PN],. (19) Interestingly, methyl rather than phenyl side groups yield the more stable materials, as shown by... 

Generally, fluorene homo- and copolymers show excellent thermal stability the Tdec of many PF exceeds 400°C (according to thermogravimetric analysis (TGA) analysis under inert atmosphere) [224]. 

Major instrumentation involved with the generation of thermal property behavior of materials includes thermogravimetric analysis (TG, TGA), DSC, differential thermal analysis (DTA), torsional braid analysis (TBA), thermomechanical analysis (TMA), thermogravimetric-mass spectrometry (TG-MS) analysis, and pyrolysis gas chromatography (PGQ. Most of these analysis techniques measure the polymer response as a function of time, atmosphere, and temperature. 

Thermogravimetric analysis (TG) under oxidizing atmosphere reveals a high-temperature exothermic weight loss of 1.5 wt.% for the TEA sample, compared to 6.6 and 9.3 wt.% for TPA and TBA nanoslabs, respectively. From IR and TG it is concluded that nanoslabs are formed in presence of TEA, but the lower TEA content and the lower intensity of the double five-ring vibration indicate that the solid contains also less structured silica. 

Thermogravimetric analysis (heating rate 10°C/min) of PPNA revealed that the polymer was stable to at least 220°C in an N2 atmosphere. (Figure 2) Differential scanning calorimetric measurements (heating rate 10°C/min) on several batches of PPNA indicated that Tg varied between 125-140°C. This variation may be a reflection of the amount of solvent (NMP) entrapped in the... 

Fig. 39. Thermogravimetric analysis of lanthanide alkoxides (programed heating rate 5 K min-1), observed in an atmosphere of predried helium gas at a measured flow rate of 45 ml min ) [16]...

The thermal conversion of the APTS coating layer upon pyrolysis can be probed from thermogravimetrical analysis. In figure 14.8, the mass lost from an aminopropylsilica is plotted as a function of treatment temperature. The analysis was performed under pure argon atmosphere. The sample was prepared by modification of dry silica gel with APTS in dry conditions. The resulting precursor has a monolayer aminosilane coating. 

---