Browsing by Author "Belgacem, Mohamed Naceur"
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- Characterization of the cork surface by inverse gas chromatographyPublication . Cordeiro, Nereida; Neto, Carlos Pascoal; Gandini, Alessandro; Belgacem, Mohamed NaceurInverse gas chromatography (IGC) at infinite dilution has been used to study the surface properties of cork from Quercus suber. The dispersive component of its surface energy was determined at different temperatures using n -alkanes as probes, and a γDS value of 38 ± 1 mJ · m-2 at 40°C was obtained. The surface acid (A)/base (B) properties were also evaluated by using polar probes and the results indicate that cork has an amphoteric character, with a KA /KB = 1.1. The advantages of IGC, compared with the technique of contact angle measurements in the characterization of the cork surface, are discussed.
- Dwarf cavendish as a source of natural fibers in poly(propylene)-based compositesPublication . Faria, Helena; Cordeiro, Nereida; Belgacem, Mohamed Naceur; Dufresne, AlainComposite materials were prepared by com pounding and hot-pressing PP or MAPP and lignocellulosic fibers extracted from the rachis of Musa acuminate Colla var. Dwarf Cavendish banana tree. The fibers were used as raw filler or after a chemical treatment expected to remove most of the extractible compounds. The resulting materials were characterized using SEM, DSC, DMA, tensile tests and water sorption experiments. All results show that the main aspect involved in the interfacial adhesion between the polar filler and the non-polar matrix is the extraction of lignin and fatty substances. This results in higher values of the degree of crystallinity and crystallization temperature of the matrix, higher mechanical properties and lower water sensitivity. Scanning electron micrograph showing the cross section of the lignocellulosic filler obtained from rachis of banana tree: (a) raw, and (b) extracted fibers.
- Properties and processing of cork powder filled cellulose derivatives compositesPublication . Godinho, Maria Helena; Martins, Assis Farinha; Belgacem, Mohamed Naceur; Gil, Luís; Cordeiro, NereidaThis paper deals with the use of cork powder, a by‐product from cork industry, as a filler to reinforce hydroxypropyl cellulose (HPC) matrix. Several films were prepared using HPC, as a matrix, filled with different amounts of cork powder (average diameter < 50 μm) (0.0; 0.5; 1.0 and 10.0% w/w) and in the presence or not of 1,4‐diisocyanatobutane (BDI) (7.0% w/w). Before the elaboration of these films, the surface properties of cork powder as well as that of suberin (main component of cork) were determined by Inverse Gas Chromatography (IGC). The tensile properties of the solid films obtained were studied and, as expected, for the films with BDI but without cork powder, the Young's modulus and the tensile strength increased, while the elongation decreased. However with the filled films it seemed that the Young's modulus decreased and the elongation increased. The Scanning Electron Microscopy showed that the fractured plane of samples with cross‐linking agent and cork powder displayed some nucleation points (0.3 μm) which indicates a strongly bonded interface and which could be considered as a responsible for the high mechanical properties observed.
- Surface modification of banana-based lignocellulose fibresPublication . Cordeiro, Nereida; Oliveira, Lúcia; Faria, Helena; Belgacem, Mohamed Naceur; Moura, João C. V. P.Lignocellulosic raw materials were isolated from rachis of Musa acuminata Colla var. cavendish and characterised before and after chemical modification. The rachis was submitted to different mechanical treatments, milling and defibration, resulting in rachis powder and rachis fi bers, respectively. The chemical composition of these two samples was established and it was shown that rachis fibres exhibited higher polysaccharide and lignin contents and lower amounts of ash and extractives components, as compared with the rachis powder. The effects of solvent extrac tion, alkali treatment and chemical modification using phenyl isocyanate, maleic anhydride, alkenyl succinic anhydride and alkyl ketone dimer as grafting agents were studied. The materials were characterized in terms of chemical structure by ATR–FT-IR and 13C-CP-MAS-NMR spectroscopy, morphology by scanning electron microscopy and surface energies by inverse gas chromatography and contact angle measurements. The surface energy of these materials was found to be very close to other similar lignocellulosic materials. Finally, the water absorption of these materials before and after treatment was ascertained. The modified fibres showed considerable changes in ATR–FT-IR and 13C-CP-MAS-NMR spectra and surface properties, providing very convincing evidence that chemical grafting had occurred.
- Surface properties of suberinPublication . Cordeiro, Nereida; Aurenty, Patrice; Belgacem, Mohamed Naceur; Gandini, Alessandro; Neto, Carlos PascoalThe surface energy of suberin was determined by four different methods, namely, (i) contact angle measurements, (ii) Wilhelmy plate measurements, (iii) maximum bubble pressure, and (iv) inverse gas chromatography (IGC). The first three methods gave a gammasub value in the range 40-50 mN m-1 at room temperature. The major component of this value reflects the dispersive contribution. The IGC measurements showed a higher dispersive term, which is common with this method of characterization. The surface acid (A)/base (B) properties were also evaluated, and the results indicated that suberin has an acidic character.
- Urethanes and polyurethanes from suberin: 1. Kinetic studyPublication . Cordeiro, Nereida; Belgacem, Mohamed Naceur; Gandini, Alessandro; Neto, Carlos PascoalWithin the context of a study on the preparation and the characterization of polyurethanes based on suberin, as a polyol, and conventional polyisocyanates, it was deemed necessary to carry out a preliminary study on the reactivity of the hydroxy functions of suberin. Aliphatic and aromatic mono- and di-isocyanates were tested and the kinetics of this system followed the classical second order up to conversions of about 85%. The influence of the steric hindrance and the electronic factors, linked to the specific structures of both types of isocyanates, was established.
- Valorisation of different agricultural crops in papermaking applicationsPublication . Schott, Séverine; Chaussy, Didier; Mauret, Evelyne; Desloges, Isabelle; Anabela, Antunes; Cordeiro, Nereida; Belgacem, Mohamed Naceur