1,720,982 research outputs found
ON THE NATURE OF INTERMOLECULAR INTERACTIONS IN POLYMER BLENDS - USE OF MODEL COMPOUNDS AS A TOOL FOR INVESTIGATING POLYMER-POLYMER MISCIBILITY
No full textAn FTIR study has been performed on two low molecular weight model compounds of diethylmaleate functionalized polyethylene, ethyl 3-carbethoxy-4-propylheptanoate (EPH) and ethyl 3-carbethoxy-4-hexyldecanoate (EHD), recording spectra in different solvents (heptane, tetrahydrofuran, carbon tctrachloride, chloroform) and in the presence of a presumable PVC model, 2-chlorobutane (2CB). These different systems allowed the observation of some correlations between spectroscopic data and chemical composition of solutions and functionalized polyethylene/PVC blends, supporting the hypothesis of specific hydrogen bond type interactions between the carboxylic oxygen of the functionalized polyethylene and the methinic hydrogens of PVC
LOW-TEMPERATURE AIR OXIDATION OF COAL AND ITS PYRIDINE EXTRACTION PRODUCTS - FOURIER-TRANSFORM INFRARED STUDIES
No full textFourier transform infrared spectroscopy has been used to study the evolution of the structure of a bituminous coal and its pyridine extraction products during oxidation. Different methods of analysis of the spectra have been used, such as curve-resolving routines, coupled to second derivative methods and area integration. The pyridine extract has been found to maintain the characteristic absorption bands of the original coal and to present marked susceptibility towards oxidation, to a greater extent than its parent coal. The analysis of the coal, extract and residue spectra and their comparison as oxidation proceeds, give an insight into the complex phenomena occurring. Pyridine extract spectra present a better separation of contributions of the bands involved, by the low temperature oxidation of low rank coals, particularly in the zones 3500-2800 and 1800-1500 cm-1
FUNCTIONALIZATION OF MONTMORILLONITE BY ACRYLAMIDE POLYMERS CONTAINING SIDE-CHAIN AMMONIUM CATIONS
No full textNon-extractable poly(methyl methacrylate) (PMMA)-montmorillonite adducts were prepared by two distinct processes: (a) In the first method, free-radical copolymerization of MMA with clay previously treated with 2-(N-methyl-N,N-diethylammonium iodide) ethyl acrylate (QD1) or 2-(N-butyl-N,N-diethylammonium bromide) ethyl acrylate (QD4) was performed. (b) The second method was based on the direct interaction of montmorillonite with various copolymers of MMA with QD1 or QD4. The structure of the adducts as determined by Fourier-transform infra-red spectroscopy, thermogravimetric analysis and X-ray diffraction was shown to consist of the insertion of MMA macromolecules between lamellar layers whose separation was consequently higher than in the polymer-free clay. The polymer was strongly fixed to the inorganic surfaces, probably due to cooperative formation of electrostatic bonding. The thermal stability of the organic polymers was substantially enhanced in the adducts
FT-IR Investigation of the Structural Changes of Sulcis and South Africa Coals under Progressive Heating in Vacuum: Correlation with Volatile Matter
Full text linkThe analysis of gas evolving during the pyrolysis of two very different rank coals was studied by using FT-IR spectroscopy. These coals, coming from Sulcis (Sardinia, Italy) and from South Africa, respectively, were subjected to progressive heating up to 800°C in vacuum. The thermal destruction of coal was followed by monitoring the production of gases in this range of temperature. The gases evolving in the heating from room temperature to 800°C were collected at intervals of 100°C and analysed by infrared spectroscopy. The relative pressures
were plotted against temperature. These graphs clearly show the correlation among qualitative gas composition, temperature, and the maximum value of emissions, thus confirming FT-IR analysis as a powerful key for pyrolysis monitoring
“ Polymer composites with HEMP fibres: compatibilization, Morphology, Thermal And mechanical properties
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New monodispersed palladium nanoparticles stabilized by poly-(N-vinyl-2-pyrrolidone): Preparation, structural study and catalytic properties
No full textMesitylene/1-hexene solvated palladium nanoparticles, obtained by metal vapour synthesis (MVS) technique,
were stabilized in solution at room temperature with poly-(N-vinyl-2-pyrrolidone) (PVP) and isolated
by precipitation with a diethyl ether or THF as brown powder. HRTEM and FT-IR analyses on
samples with different Pd/PVP ratio (1%, 5%, 10%, 15%, 20 w/w%) showed palladium nanoparticles with
mean diameters limited in the range 1.5–2.5 nm and the presence of competitive intermolecular interactions
between C@O groups and palladium atoms on nanoparticle surface. The Pd–PVP systems, dissolved
in EtOH solvent, showed excellent catalytic activity and selectivity in the hydrogenation of
aliphatic alkynes (1-hexyne, 2-hexyne, 3-hexyne, 3-hexyne-1-ol) to the corresponding (Z)-alkenes. The
catalytic activity of Pd–PVP samples, dissolved in 1-methyl-2-pyrrolidinone (NMP), has been also evaluated
in the Mizoroki–Heck C–C coupling reaction of iodobenzene and bromo-arenes with butyl acrylate
showing high efficiency. Moreover, the catalyst can be quantitatively recovered at the end of the reaction
by precipitation with diethyl ether and reused without significant loss of catalytic activity
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