Browsing by Author "Pascoal Neto, C."
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- Comparative analysis of the lignins of cork from Quercus suber L. and wood from Eucalyptus globulus L. by dry hydrogen iodide cleavagePublication . Akim, L. G.; Cordeiro, N.; Pascoal Neto, C.; Gandini, A.
- Cork suberin as a new source of chemicals.: 1. isolation and chemical characterization of its compositionPublication . Cordeiro, N.; Belgacem, M.N.; Silvestre, A.J.D.; Pascoal Neto, C.; Gandini, A.Extractive-free cork from Quercus suber L. was submitted to a solvolysis treatment with methanolic NaOH which yielded 37% (o.d. cork) of suberin. This mixture of compounds was thoroughly characterized by FTIR, 1 H- and 13C-NMR, gas chromatogra phy coupled with mass spectrometric (GC–MS) analysis, vapour pressure osmometry (VPO), mass spectrography (MS) and gel permeation chromatography (GPC). After derivatization, the main components of the volatile fraction, representing less than half of the total, were found to be v-hydroxymonocarboxylates, a,v-dicarboxylates, simple alkanoates and 1-alkanols, all with chain lengths ranging from C16 to C24. A second fraction, with an average molecular weight about three times higher, was detected by VPO, MS and GPC. The presence of this important fraction in cork suberin had not been recognized in earlier studies. Both fractions constitute interesting precursors for the elaboration of new materials.
- Cork suberin as an additive in offset lithographic printing inksPublication . Cordeiro, N.; Blayo, A.; Belgacem, N.M.; Gandini, A.; Pascoal Neto, C.; LeNest, J.-F.Suberin oligomers, isolated from cork (Quercus suber L.), were used as additives in ‘Waterless’ and vegetable-oil ink formulations, in the range of 2–10% w/w. The rheological behaviour of the suberin oligomers as well as of the inks, with and without suberin, were investigated as a function of temperature. It was shown that the addition of suberin induces a decrease of viscosity of both inks. The tack of pristine inks, suberin oligomers and their mixtures were determined at different temperatures: the variation of this parameter as a function of time provided information about the drying kinetics of these formulations. The tack of the ‘Waterless’ ink was found to increase with the introduction of suberin, whereas that of vegetable-oil based counterparts decreased. All the trends observed were interpreted in terms of the differences in composition between the two types of inks. Preliminary printing tests were carried out with the various suberin-containing inks.
- Suberin-based polyurethanes: synthesis, characterization and kinetics of their formationPublication . Cordeiro, N.; Belgacem, M. N.; Gandini, A.; Pascoal Neto, C.
- Urethanes and polyurethanes from suberin 2: synthesis and characterizationPublication . Cordeiro, N.; Belgacem, M.N.; Gandini, A.; Pascoal Neto, C.Polyurethanes based on suberin from cork of Quercus suber L. and conventional isocyanate monomers were prepared and fully characterized in terms of both structure (FTIR and 1 H NMR spectroscopy) and thermal properties (differential scanning calorimetry and thermogravimetric analysis). Two fractions were systematically isolated, namely (i) methylene-chloride soluble products, which corresponded to linear and branched macromolecules and (ii) methylene-chloride insoluble products, representing the crosslinked material. The structures of these polymers were regular and no appreciable side reactions were detected. DSC analyses provided information about the glass transition temperature of both fractions and this parameter was correlated with the stiffness of the isocyanate used. The TGA of these polyurethanes showed that they started to degrade at about 175°C and that the residue at 400°C was around 50%. The highest amounts of insoluble fractions, as well as the highest Tgs, were reached when an initial [NCO]/[OH] of unity was used.