Thermogravimetric analysis, composition

Thermal stability is a crucial factor when polysaccharides are used as reinforcing agents because they suffer from inferior thermal properties compared to inorganic fillers. However, thermogravimetric analysis (TGA) of biocomposites suggested that the degradation temperatures of biocomposites are in close proximity with those of carbon black composites (Table-1). 

When solids react, we would like to know at what temperature the solid state reaction takes place. If the solid decomposes to a different composition, or phase, we would like to have this knowledge so that we can predict and use that knowledge In preparation of desired materials. Sometimes, intermediate compounds form before the final phase. In this chapter, we will detail some of the measurements used to characterize the solid state and methods used to foUow solid state reactions. This will consist of various types of thermal analysis (TA), including differentlEd thermal analysis (DTA), thermogravimetric analysis (TGA) and measurements of optical properties. 

In this study, we extend the range of inorganic materials produced from polymeric precursors to include copper composites. Soluble complexes between poly(2-vinylpyridine) (P2VPy) and cupric chloride were prepared in a mixed solvent of 95% methanol 5% water. Pyrolysis of the isolated complexes results in the formation of carbonaceous composites of copper. The decomposition mechanism of the complexes was studied by optical, infrared, x-ray photoelectron and pyrolysis mass spectroscopy as well as thermogravimetric analysis and magnetic susceptibility measurements. 

Recently, Kroeze et al. prepared polymeric iniferter 34 including poly(BD) segments in the main chain [152]. They successfully synthesized poly(BD)-block-poly(SAN), which was characterized by gel permeation chromatography, elemental analysis, thermogravimetric analysis, NMR, dynamic mechanical thermal analysis, and transmission electron microscopy. By varying the polymerization time and iniferter concentration, the composition and the sequence length were controlled. The analysis confirmed the chain microphase separation in the multiblock copolymers. 

Thermogravimetric analysis In thermogravimetric analysis (TGA) a sensitive balance is used to follow the weight change of the sample as a function of temperature. Its applications include the assessment of thermal stability and decomposition temperature, extent of cure in condensation polymers, composition and some information on sequence distribution in copolymers, and composition of filled polymers, among many others. 

The nature of the material to be studied, which means its degree of crystallinity and perfectness of crystal structure, may have a significant effect on the thermoanalytical behavior. In spite of identical chemical composition of a certain material the variations with respect to structure, imperfections, grain boundaries, etc. are almost infinite. Of course many of these will not show in normal thermogravimetric analysis, with very sensitive apparatus characteristically different TG curves18, 19 may be obtained however. As an example Fig. 26 shows the thermal decomposition of hydrozincite, Zn5(OH)6(003)2, whereby equal amounts of samples from natural origin and synthetic preparations are compared. 

The elemental composition of CuCr204 Cu 27.44%, Cr 44.92%, O 27.64%. The catalyst is analysed by measurement of surface area and pore volume also by differential thermal analysis, thermogravimetric analysis and x-ray studies. 

Elemental composition (for anhydrous K2C2O4) K 47.05%, C 14.45%, O 38.50%. The water content of the monohydrate, K2C204 H20 is 9.78%, which may be measured by thermogravimetric analysis. Potassium may be analyzed by AA, flame photometry or ICP/AES (see Potassium). The concentration of oxalate in the aqueous solution of the salt may be determined by titrating... 

The section Analysis starts with elemental composition of the compound. Thus the composition of any compound can be determined from its elemental analysis, particularly the metal content. For practically all metal salts, atomic absorption and emission spectrophotometric methods are favored in this text for measuring metal content. Also, some other instrumental techniques such as x-ray fluorescence, x-ray diffraction, and neutron activation analyses are suggested. Many refractory substances and also a number of salts can be characterized nondestructively by x-ray methods. Anions can be measured in aqueous solutions by ion chromatography, ion-selective electrodes, titration, and colorimetric reactions. Water of crystallization can be measured by simple gravimetry or thermogravimetric analysis. 

Current from reaction 16 is proportional to the total Cu in the sample. Current from reaction 15 is proportional to (Cu2 + 2Cus+), since Cus+ oxidized twice as much iodide as Cu2+. The relative currents from reactions IS and 16 can be used to deduce the fraction of Cu in the Cus+ state. A sample whose composition was YBa2Cus0699 by reductive thermogravimetric analysis appeared to be YBa2CusOe 92 by the rotating ring-disk electrode. 

By definition [26,27], thermogravimetric analysis is a technique in which the mass of a substance is measured as a function of time or temperature while the substance is subjected to a controlled temperature program. Because mass is a fundamental attribute of a material, any mass change is more likely to be associated with a chemical change, which may, in turn, reflect a compositional change. 

Improved heat-resistant UV compositions for optical fiber applications These compositions are nonurethane UV cure compositions that have neither carbamate moieties nor long-chain poly(alkylene oxide) soft segments and exhibit inherently better thermal stability measured by thermogravimetric analysis (TGA) than typical coatings for optical fibers based on urethane acrylate oligomers. 

In thermogravimetric analysis, a substance is heated, and its mass is measured as a function of temperature. Figure 27-3 shows how the composition of calcium salicylate changes in four stages ... 

Kundu and Bhattacharya14 have isolated dioxouranium complexes of benzohydroxamic acid with the compositions M[U02(C7H602N)3] [where M = Li, Na, K, Cs, Tl, N4, pyH+ (pyridinium) or agH+ (aminoguanidinium)] and M [U02(C7H602N)3]2 [where M = enH2+ (ethylene-diammonium)]. All the complexes, with the exception of the sodium compound, are insoluble in common organic solvents but are soluble in DMSO and DMF. The complexes have been characterized on the basis of electronic, IR and molar conductance data in DMF. Their fairly stable character is indicated by thermogravimetric analysis and the stability order is NH4+ < Tl+ < Cs+ < Li+ w Na+ agH+ < K+ pyH+ < enHl+. 

The reaction between toluene 2,4-diisocyanate and carboxylated MWCNTs afforded amido-functionalized nanotubes containing highly reactive isocyanate groups on their surface (Scheme 1.4). The amount of the isocyanate groups was determined by chemical titration and thermogravimetric analysis (TGA) [105]. The modified tubes may constitute promising components to prepare polymer-nanotube composites and coatings [106]. 

The thermal characterisation of elastomers has recently been reviewed by Sircar [28] from which it appears that DSC followed by TG/DTG are the most popular thermal analysis techniques for elastomer applications. The TG/differential thermal gravimetry (DTG) method remains the method of choice for compositional analysis of uncured and cured elastomer compounds. Sircar s comprehensive review [28] was based on single thermal methods (TG, DSC, differential thermal analysis (DTA), thermomechanical analysis (TMA), DMA) and excluded combined (TG-DSC, TG-DTA) and simultaneous (TG-fourier transform infrared (TG-FTIR), TG-mass spectroscopy (TG-MS)) techniques. In this chapter the emphasis is on those multiple and hyphenated thermogravimetric analysis techniques which have had an impact on the characterisation of elastomers. The review is based mainly on Chemical Abstracts records corresponding to the keywords elastomers, thermogravimetry, differential scanning calorimetry, differential thermal analysis, infrared and mass spectrometry over the period 1979-1999. Table 1.1 contains the references to the various combined techniques. 

Thermogravimetric analysis can yield a considerable amount of information about the composition of an elastomer system and is a common means of testing of EPDM rubber compounds [51]. The DTG curve may serve as an identifier of the type of elastomer in a compounded formulation. 

Sircar [138] has reviewed the analysis of elastomer vulcanisate composition by TG/DTG techniques. The classical ASTM method, D297-93 [139], is too lengthy to be of much practical use on a routine basis, often requires preliminary identification of the polymer and is costly. TG has gained itself wide acceptance as a method for quantitative compositional analysis of vulcanisates ASTM El 131 [140], is basically designed for the analysis of rubber compounds [141]. Thermogravimetric analysis can be used to determine ... 

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