Thermal sample weight

In the presence of oxygen (air), the thermal decomposition of amphiboles is associated with an oxidation of divalent iron to trivalent iron, which may lead to an increase in the sample weight the oxidation process also induces an obvious color alteration, the fibers acquire the characteristic ferric oxide... 

A Perkin-Elmer DSC-7 was used for thermal characterization of the starting phenolic resins and copolymers prepared. Scans were run at 10"C/min using sample weights of 15-25 mg. In all cases the amorphous, powdered polymers were used for the evaluation. 

Changes in catalysts during preparation, which often involves thermal calcination, oxidation, and reduction, can also be followed by recording the associated variations in sample weight, as in normal thermogravimetry (TG) or differential thermogravimetiy (DTG) or in sample temperature,... 

The vacuum-thermal weight loss results presented in Figure 3 show a two-step weight loss pattern for the irradiated sample. Weight loss associated with volatilization of the first product begins before 100°C and the second near 150°C. No weight loss was observed below 225°C for the nonirradiated composite sample. 

Fig. 27. Effect of sample weight and volume on the thermal decomposition of calcite...

Four nitrosamines, seven nitramines, three nitroesters and the explosives Semtex 10 and Composition B have been investigated by TGA. Linear dependence was confirmed between the position of the TGA onsets, as defined in the sense of Perkin-Elmer s TGA-7 standard program, and the samples weights. The slope of this dependence is closely related to the thermal reactivity and molecular structure. The intercept values of the dependence correlate with the autoignition temperatures and with the critical temperatures of the studied compounds, without any clear influence from molecular structure. Results show that Semtex 10 exhibits approximately the same thermostability as its active component pentaerythrityl tetranitrate (PETN, 274). Results also show that TGA data for Composition B do not correlate with analogous data for pure nitramines564. 

Figure 3. Thermal gravimetric analysis of DuPont PI2545. Conditions temperature scan, 4°C/min precured 20 min at 70°C and 30 min at 120°C sample weight,...

Differential Scanning Calorimetry (DSC). A DuPont 990 thermal analyzer equipped with a DSC cell was employed to record the endothermic and exothermic reactions which occurred during temperature-programmed (10°C/min) heating of the polymer samples. Sample weights were 15 mg, and the ambient atmosphere was either prepurified nitrogen or line air. 

TG) were carried out with a DuPont Thermal Analyzer, Type 990, with a 10 mg sample in air. The sample weight was recorded against temperature in a range of 20-600°C at a heating rate of 10°C/min. 

One of the best features of thermal conductivity detectors with helium carrier gas is the ease of quantitative analysis. It has been shown experimentally that relative response factors, where sample weight is used, are independent of (a) type of detector (filament or thermistor), (b) cell and sensor temperature, (c) concentration of sample, (d) helium flowrate, and (e) detector current. In addition, relative response factors change only slightly within a series of homologous compounds. The first systematic study of TCD responses in helium was done by Rosie and Grob and are summarized in reference (6). 

Fig. 12. Thermal behavior of H3[PMo1204ol 16.5 H20 in nitrogen (sample weight for tga = 0.3062)...

Fig. 12. The thermal decomposition of (NH4)2Mo02S2 under nitrogen (sample weight 134.9 mg)...

Although a large number of thermal analysis techniques have been developed, the most commonly applied are those of thermogravimetry (TG, the measure of thermally induced weight loss of a material as a function of applied temperature), differential thermal analysis (DTA, the difference in temperature existing between a sample and a reference as a function of temperature), and differential scanning calorimetry (DSC, the difference in heat capacity between the sample and... 

There are two sources of interferences in this test method—moisture and particle size. Moisture increases the mass loss, the moisture-free sample weight is decreased by the amount of moisture actually present in the test sample, and the particle size range of the analysis sample affects the volatile matter. The coarser the sample, the lower the reported yield of volatile matter. The method is not satisfactory for determining the content of dust control material, and samples with a thermal history above 600°C (1112°F) are excluded from this test. 

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