Thermogravimetric analysis isotherms

Contact angle measurements Isothermal microcalorimetry Gravimetric sorption Inverse gas chromatography Differential scanning calorimetry Thermogravimetric analysis Isothermal microcalorimetry Infra red analysis X-ray diffraction... 

The main focus of the project was the elucidation of particle-stabilizer-solvent interactions as a function of the binding strength, the chain length, the concentration of the stabilizers, the polarity of the solvents, and the surface configuration as well as the size and morphology of the metal oxide nanoparticles. Therefore, to characterize the stabilization kinetics, a number of analytical methods, such as thermogravimetric analysis, isothermal titration calorimetry, and spectroscopic methods, were combined. 

In a study on the thermal and UV ageing of two commercial polyfoxymethy-lene) (POM) samples, one of which was a copolymer (see related study discussed later under Section 4.3, thermogravimetric analysis (TGA)), used in car interior applications, involving both DSC and TGA, isothermal OIT measurements were made at several different temperatures [8]. One conclusion from this study was that "extrapolation of the OIT data from high temperatures (molten state) to ambient temperatures in the solid state does not reflect effective antioxidant performance at room temperature", and thus measurements close to the melting point are not appropriate for reliable lifetime estimations. 

Nitrogen adsorption was performed at -196 °C in a Micromeritics ASAP 2010 volumetric instrument. The samples were outgassed at 80 °C prior to the adsorption measurement until a 3.10 3 Torr static vacuum was reached. The surface area was calculated by the Brunauer-Emmett-Teller (BET) method. Micropore volume and external surface area were evaluated by the alpha-S method using a standard isotherm measured on Aerosil 200 fumed silica [8]. Powder X-ray diffraction (XRD) patterns of samples dried at 80 °C were collected at room temperature on a Broker AXS D-8 diffractometer with Cu Ka radiation. Thermogravimetric analysis was carried out in air flow with heating rate 10 °C min"1 up to 900 °C in a Netzsch TG 209 C thermal balance. SEM micrographs were recorded on a Hitachi S4500 microscope. 

Thermogravimetric analysis (TGA) has often been used to determine pyrolysis rates and activation energies (Ea). The technique is relatively fast, simple and convenient, and many experimental variables can be quickly examined. However for cellulose, as with most polymers, the kinetics of mass loss can be extremely complex (8 ) and isothermal experiments are often needed to separate and identify temperature effects (9. Also, the rate of mass loss should not be assumed to be related to the pyrolysis kinetic rate ( 6 ) since multiple competing reactions which result in different mass losses occur. Finally, kinetic rate values obtained from TGA can be dependent on the technique used to analyze the data. 

The data (Table II) for the percent residue at 500°C under isothermal thermogravimetric analysis also show reasonable agreement with the data for the residue from the experiments in the FMRC Small-Scale Flammability Apparatus where large-scale fire conditions are simulated. Thus, the TG analysis for flammability assessment of FRC materials may be more useful than previously considered. 

For applications requiring high temperature and extraction resistance, polymeric esters are used (88). New polymeric plasticisers are in development (87) including adipate based for improved low temperature properties (103). Plastisols based on propyleneglycol adipate have been examined (198) and the thermal degradation has been determined using dynamic and isothermal thermogravimetric analysis (188). 

Thermogravimetric analysis (TGA) was performed with a TA Instrument 2050 thermal analyzer in order to determine the oxygen deficiency of the samples. The samples were ramped at 10°/min to 900 °C and remained isothermal in the presence of O2 gas until oxidation was complete. The oxidized powders were analyzed by PXD and the lattice parameters were compared to published values of StjCrNbO [9] to confirm complete oxidation. 

Thermogravimetric analysis (TGA) and differential thermal analysis (DTA) were performed in air at a heating rate of lOK/min. on a PTC-lOA thermogravimetric analyzer. The adsorption isotherms for vapor-phase water and ethanol were measured using the BET method. The saturation pressures, Pq, of water and ethanol at 299K are 758 mmHg. Prior to the adsorption experiments, the samples were dehydrated at 673K in air for 4 h. 

Application of difiFerential thermal analysis and thermogravimetric analysis techniques to the pyrolysis of cellulose is obviously complicated by the complexity of the reactions involved, and the corrections and simplifying assumptions that are required in calculating the kinetic parameters. Consequently, these methods provide general information, instead of accurate identification and definition of the individual reactions (and their kinetics), which are traditionally conducted under isothermal conditions. The data obtained by dynamic methods are, however, useful for comparing the efiFects of various conditions or treatments on the pyrolysis of cellulose. In this respect, the application of thermal analysis for investigating the effect of salts (and flame retardants in general) on the combustion of cellulosic materials is of special interest and will be discussed later (see p. 467). 

The influence of sorbed moisture on chemical stability and the flow and compaction of powders and granulations is well established. The moisture content and hygroscopicity of excipients is particularly important as total product processing as well as finished product stability can be affected. Hygroscopicity, moisture-sorption isotherms, and equilibrium moisture content can be determined by thermogravimetric analysis and Karl Fisher titration methods. 

The catalysts were characterized by N2 adsorption-desorption isotherms, thermogravimetric analysis (TGA), temperature-programmed desorption of ammonia (NH3-TPD), X-ray diffraction (XRD), Raman spectroscopy, in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and X-ray photoelectron spectroscopy (XPS). The procedures and experimental conditions have been detailed elsewhere [9]. 

FIGURE 255 Thermogravimetric analysis of silica samples, each heated at 40 °C per hour to 900 °C but interrupted by a 24 h isothermal hold period at various temperatures. 

High thermal and oxidative stability of the imide-linked fluorocarbon ether polymers is shown by thermogravimetric analysis in air (Figure 2). The weight loss was less than 5% to a temperature of 450°C. Isothermal weight loss in air at 260°C was less than 0.3% in 112 hours for the polymer where x + y = 3. 

A Perkin-Elmer TGA-7 instrument calibrated by Curie points of several metal standards has been employed for non-isothermal thermogravimetric analysis. The measurements were carried out at a desired heating rate (in the range of 3 - 40 K/min) in both inert (argon) and oxidizing (oxygen) atmospheres, as appropriate. 

Isothermal methods have generally been used for the study of thermal degradation mechanisms and the determination of kinetic parameters. In recent years, however, dynamic thermogravimetric analysis (TGA) has been developed. In this case, polymer samples are weighed in a... 

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