Volatilization thermal

Samples thermally volatile to some extent to be desorbed... 

Thermal Volatilization. Thermal volatilization schemes have been popular for speciation of acidic sulfate compounds in aerosols. Both filter-... 

Freeze-dried DOM samples collected with the siphon-elution system (Kuzyakov and Siniakina, 2001) for the first time showed diurnal dynamics in the molecular-chemical composition of maize rhizodeposits (Kuzyakov et al., 2003). In a forthcoming study with maize, Melnitchouck et al. (2005) showed that amino acids, especially aspartic acid, asparagine, glutamic acid, phenylalanine, leucine and isoleucine contributed to the more intensive rhizodeposition during daytime than during nighttime. Furthermore, the maximum of thermal volatilization of peptides at low pyrolysis temperature in Figure 14.8 indicates the rhizodeposition or microbial formation of free amino acids rather than amino acids bound in peptides or trapped in soil humic substances. 

The characterization of the physical and chemical changes that occur in montmorillonite/PDMS nanocomposite elastomers as they are thermally aged is reported. Broadband Dielectric Spectroscopy (BDS) was used to track changes in the physical interaction between the polymer and clay associated with increases in non-oxidative thermal stability (as determined by TGA). The evolution of volatile siloxane species from the elastomers was characterized with Thermal Volatilization Analysis (TVA). Results suggest that the improved thermal stability and the increases in polymer/clay association are a result of significant re-structuring of the polymer network. 

Thermal volatilization analysis (TVA) A pyrolysis technique in which the pressure of... 

Villermaux J., Antoine B., Lede J. and Soulignac F. (1986) A new model for thermal volatilization of solid particles undergoing fast pyrolysis. Chemical Engineering Science, 40, No. 1,151-7... 

Thermal volatilization analysis (TVA) of blends or mixtures of PP and poly(methyl methacrylate) (PMMA) reveals that the PMMA component tends to be stabilized and the PP destabilized. Pre-Irradlatlon of blends strongly suppresses the yield of monomeric methyl methacrylate but methyl methacrylate units appear In the chain fragment fraction. 

Figure 5 compares Thermal Volatilization Analysis (TVA) thermograms for unlrradlated and preirradiated polypropylene. The lack of coincidence of the traces In each thermogram Indicates a... 

When sparks are used for the ablation of electrically conducting solids, less changes with variations in the matrix composition than in the case of arc ablation occur. This is due to the fact that thermal volatilization plays less of a role. However, in the case of brass, it is seen from x-ray analyses of the ablated material on a Nudepore filter, for samples of the crater wall and the burning crater, that zinc volatilizes more than copper (Table 5), which makes the method difficult to apply to these samples. 

Pigmented polymer coatings on steel and PTFE as well as PTFE-based copolymers can be analyzed by rf-GD-MS in order to fingerprint them [648]. Advantages compared with SIMS and x-ray photoelectron spectroscopy are that the method is fast and does not require dissolution of the sample, and thermal volatilization processes do not appear to take place. 

The degradation behaviour of polymethylmethacrylate is easily characterized by thermal volatilization analysis [87] (Fig. 29). Monomer is obtained in very high yield in all cases. A polymer sample prepared by a free radical reaction undergoes a rapid depolymerization at about 275°C as indicated by the first peak. The second peak, situated between 350 and 400°C, corresponds to a second mode of initiation of chain depolymerization. For samples prepared by anionic polymerization, the first peak is not observed. Depolymerization of the whole sample occurs above 350°C. 

A thermal volatilization analysis of polyvinylacetate degradation has been reported by Gardner and McNeill [200] (Fig. 54). Two maxima are observed at 322 and 435°C. The Pirani gauge situated after the 0°C trap responds to all volatile products, while the gauge situated after the —196°C trap responds only to non-condensable gases. Infrared analysis has shown the presence of carbon monoxide and methane in this last fraction. The... 

Fig. 54. Thermal volatilization analysis for polyvinylacptate. 100 mg film sample, 5 degCmin-1 1200].

The rates of production of volatile material from polyvinylacetate, polyvinylchloride and vinylacetate vinylchloride copolymers, covering the entire composition range, have been compared by thermal volatilization analysis. It has been found that, at both extremes of the composition range, incorporation of the comonomer unit induces de-stabilization. Minimum stability occurs for composition of approximately 40—50 mole % vinylacetate. The rate of volatilization as a function of the composition of the copolymers is given in Fig. 74. The results were confirmed by a study of the thermal degradation in tritolylphosphate solution. The stability of the copolymers is a minimum at 30—40 mole % vinylacetate. HC1 and acetic acid catalyse the degradation of the... 

The thermal volatilization analysis of a mixture of polyvinylchloride and polystyrene is given in Fig. 81. The first peak corresponds to the elimination of HC1 and the second to that of styrene. Dehydrochlorination is retarded in the mixture. The production of styrene is also retarded styrene evolution, in fact, does not occur below 350°C. This contrasts with the behaviour of polyvinylchloride-polymethylmethacrylate mixtures for which methacrylate formation accompanies dehydrochlorination. The observed behaviour implies that, if chlorine radical attack on polystyrene occurs, the polystyrene radicals produced are unable to undergo depolymerization at 300° C. According to McNeill et al. [323], structural changes leading to increased stability in the polystyrene must take place. This could also occur by addition of Cl to the aromatic ring, yielding a cyclohexadienyl-type radical which is unable to induce depolymerization of the styrene chain. 

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