Structural characterization of Nigerian coals by X-ray diffraction, Raman and FTIR spectroscopy

Analysis of carboxyl group in coal and coal aromaticity by Fourier transform infrared (FT-IR) spectrometry

A method with good precision has been developed to quantitatively measure the degree of α-, β-, and γ crystallinity in poly(vinylidene fluoride) (PVDF) by means of infrared spectroscopy. The phase composition of solution-deposited PVDF films was found to be strongly influenced by the presence of hydrophilic residues on the silicon substrate, the relative humidity present at film deposition, the spatial position on the substrate, and the thermal treatment of the deposited film. Films produced on pristine surfaces gave predominantly α-phase PVDF, but when a layer of polar solvent (acetone or methanol) remained on the surface, the films produced were predominantly γ phase. Higher humidity promoted a higher fraction of γ crystallinity in the solution-deposited PVDF films. Solution-cast films had highly variable composition across the substrate, whereas spin-cast films were uniform. High-temperature annealing of PVDF films normally converts the polymer to the γ phase, but annealing the film while still attached to the silicon substrate inhibited this phase transformation. Low-temperature annealing of freestanding films led to a previously unreported thermal event in the DSC, a premelting process that is a kinetic event, assigned to a crystalline relaxation. Higher-temperature annealing gave a double endotherm, assigned to melting of different-sized crystalline domains. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1093–1100, 2003

Determination of the crystalline phases of poly(vinylidene fluoride) under different preparation conditions using differential scanning calorimetry and infrared spectroscopy

Vibrational spectroscopic detection of beta- and gamma-turns in synthetic and natural peptides and proteins.

Analogue calorimetry for blends of poly(vinyl ester)s and polyacrylates has been studied. Hydrogenated monomers were used as analogues of the corresponding polymers. It is found that isomeric esters differing only in the orientation of the COO group mix with only small heat change, which can be positive or negative. The values of the interaction energy density, B12 (in cal/cm3), are −0.045, 0.031, and −0.076, respectively, for the following binary mixtures; ethyl acetate + methyl propionate, n-propyl propionate + ethyl butyrate, and phenyl propionate + ethyl benzoate. The negative heat of mixing for the two pairs of very similar liquids, although unexpected, explains why the corresponding polymers are miscible. The small positive heat of mixing for the other pair is sufficient to predict demixing of the corresponding polymers, viz., poly(n-propyl acrylate) and poly(vinyl butyrate), which contradicts the observation of their homogeneous mixing. This suggests that hydrogenated monomers are not always the pr...

Analogue Calorimetric Studies of Blends of Poly(vinyl ester)s and Polyacrylates

New monodispersed palladium nanoparticles stabilized by poly-(N-vinyl-2-pyrrolidone): Preparation, structural study and catalytic properties

FT-IR investigation of the structural changes of Sulcis and South Africa coals under progressive heating in vacuum

A semiquantitative analysis by means of midinfrared FT-IR spectroscopy was tuned for the simultaneous determination of cellulose, hemicellulose, and lignin in industrial crops such as giant reed (Arundo donax L.) and switchgrass (Panicum virgatum L.). Ternary mixtures of pure cellulose, hemicellulose, and lignin were prepared and a direct correlation area/concentration was achieved for cellulose and lignin, whereas indirect correlations were found for hemicellulose quantification. Good correspondences between the values derived from our model and those reported in the literature or obtained according to the official Van Soest method were ascertained. Average contents of 40–45% of cellulose, 20–25% of hemicellulose, and 20–25% of lignin were obtained for different samples of giant reed species. In the case of switchgrass, a content of 36% of cellulose, 28% of hemicellulose, and 26% of lignin was achieved. This analysis was also carried out on giant reed and switchgrass residues after a mild hydrolysis step carried out with dilute hydrochloric acid for the production of furfural with good yield. Reasonable compositional data were obtained, thus allowing an indirect monitoring which helps the optimization of the hydrothermal pretreatment for furfural production from hemicellulose fractions.

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Midinfrared FT-IR as a Tool for Monitoring Herbaceous Biomass Composition and Its Conversion to Furfural

Poly(vinylidene fluoride) (PVDF) samples, obtained by casting from tetrahydrofuran solutions and submitted to various thermal treatments, have been examined by Fourier transform-infrared microspectroscopy (FTIR-M) and differential scanning calorimetry (DSC). This kind of analysis allowed us to examine microdomains of samples with different morphological characteristics and to obtain an indication of the polymorphism of PVDF. In some cases the simultaneous presence of two or three forms has been evidenced thanks to the comparison of FTIR-M spectra and DSC traces. Vibrational spectra of single crystalline forms can be recorded by FTIR-M on phase homogeneous microdomains.

Aldo D'Alessio

Papers

New monodispersed palladium nanoparticles stabilized by poly-(N-vinyl-2-pyrrolidone): Preparation, structural study and catalytic properties

FT-IR investigation of the structural changes of Sulcis and South Africa coals under progressive heating in vacuum

Midinfrared FT-IR as a Tool for Monitoring Herbaceous Biomass Composition and Its Conversion to Furfural

FTIR-microspectroscopy and DSC studies of poly(vinylidene fluoride)

Low-temperature air oxidation of coal and its pyridine extraction products - fourier-transform infrared studies