Search results for "Pyrolysi"

Group 14 Metalloles, Ionic Species and Coordination Compounds

2009

1 Introduction 2 Synthesis 3 Organic Chemical Properties of Group 14 Metalloles 4 Polymeric Silole-Containing π-Conjugated Systems 5 Ionic Species and Coordination Compounds 6 Addendum 7 Conclusion 8 Acknowledgements Keywords: five-membered heterocyclic dienes; heterocyclopentadienes - heteroles or metalloles; group 14 metalloles, ionic species and coordination compounds; gas-phase pyrolysis of silacyclopent-3-enes; organometallic dihalide reaction with dilithio reagent; group 14 metalloles; HOMO stabilization; polymeric silole-containing pi-conjugated systems

Characterization of commercial synthetic resins by pyrolysis-gas chromatography/mass spectrometry: application to modern art and conservation.

2009

To characterize a set of synthetic resins, a methodology by pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) has been developed. The studied reference materials were commercial versions of a wide range of synthetic resins. For each polymer, the pyrolytic and chromatographic conditions were optimized to adequately resolve the fragment mixture in a short time. The proposed analytical method does not require previous treatment of the sample, and due to its high sensitivity, only a small sample quantity in the microgram range can be used. The pyrolysis temperature was found to have little effect on the obtained pyrograms. The summarized data set for the individual polymer materials, es…

Detection of poly(methylmethacrylate) wear particles in capsule tissue surrounding endoprotheses by pyrolysis gas chromatography

1982

Pyrolysis gas chromatography (PGC) is used to detect polymer wear particles in capsule tissue surrounding endoprotheses implanted with poly(methylmethacrylate) as bone cement. The method allows the detection of the polymer incorporated in tissue even in the range of 1 weight%.

Das erste verklammerte und stark deformierte Adamantan

1990

Naphthothiete und ihre Anwendung in der Heterocyclen-Synthese

1995

Naphtothietes and Their Application to the Synthesis of Heterocycles The three isomeric naphthothietes 5, 11, and 16 were prepared according to the reaction sequences shown in Schemes 1–3. The final step was in each case a flash vacuum pyrolysis (FVP) of the corresponding mercaptonaphthalenemethanol 4, 9, and 15, respectively. The thiete rings in 5 and 11 can be opened by gentle heating; the ring opening of the isomer 16 possesses a much higher activation barrier. A MNDO calculation of the ΔHf values of 5, 11, and 16 and the open isomers 5′, 11′, and 16′ provides an explanation for the different behavior. Photochemical ring opening represents a useful alternative. The reaction Schemes 4, 6,…

Pyrolysis of humic acids from digested and composted sewage sludge

2000

Humic acids (HAs) were extracted from four digested sewage sludge samples composted for four months, one, two and four years. HAs were pyrolyzed at three different temperatures applying both conventional and in situ methylation (ISM) pyrolysis. The pyrolysates were analyzed using gas chromatography-mass spectrometry (GC/MS). Derivatization (ISM) and pyrolysis temperature had dramatic effects on the composition and relative amounts of the pyrolysates. Among the derivatized HA fragments aliphatic compounds prevailed under all the pyrolysis conditions tested. Aromatic substances consisting mainly of guaiacyl-type compounds were detected in higher abundances only at elevated temperatures. Witho…

1978

The thermal degradation mechanism of three aromatic polymers containing double bridged phenylether units was investigated by direct pyrolysis in the ion source of a mass spectrometer. Thermal degradation reactions were followed directly by this method detecting the thermal and electron impact induced fragments. The results obtained have provided evidence that the double bridge between the aromatic rings is the preferred fragmentation site in these polymers. Furthermore in the double sulfur bridged polymer III, extrusion of S2 from the polymer backbone takes place above 400°C. The synthesis of polymers studied is reported in the text. Der Mechanismus des thermischen Abbaus von drei aromatisc…

Mass spectrometrical detection of polymer particles in capsule tissue surrounding joint endoprotheses of polyethyleneterephthalate

1982

Pyrolysis mass spectrometry of synthetic high polymers is described. The method is used to detect polymer wear particles in capsule tissue surrounding endoprotheses with polyethyleneterephthalate parts. An approximation of semi-quantitative determination of the polymer wear will be discussed.

Mesoporous silicon carbide via nanocasting of Ludox® xerogel

2016

Porous SiC with uniformly sized 12 nm and 22 nm spherical mesopores was synthesized from nanocomposites of polycarbosilane (PCS) preceramic polymer and xerogels of Ludox® SiO2 nanoparticles as templates. The influence of PCS type (Mw 800 and 2000 Da), PCS : SiO2 ratio, pyrolysis temperature 1200–1400 °C, and addition of Ni complex to the preceramic composite was studied with respect to the SiC porous morphology, crystalline structure and chemical properties. We found that the pore walls of Ni-free por-SiC are composed of relatively large (20 nm) crystallites embedded inside a poorly crystalline SiC/SiC1+x phase. Increasing the pyrolysis temperature resulted in an increase of the large cryst…

Copolyamides from adipic and truxillic acids: Synthesis and characterization by direct pyrolysis in the mass spectrometer

1977

The synthesis of a series of polyamides and copolyamides containing α-truxillic and adipic units in the chain is reported. The thermal degradation of these polymers was investigated by direct pyrolysis in the ion source of a mass spectrometer. Thermal degradation reactions were followed directly by this method by detecting the thermal- and electron-impact-induced fragments. The results obtained show a good correlation between the intensity of mass peaks characteristic of truxillic and adipic moieties and the composition of the copolyamides, as ascertained by elemental analysis. This is an important result since it shows the potential of the direct pyrolysis method in the analysis of copolym…