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- The organosolv fractionation of cork componentsPublication . Cordeiro, Nereid; Neto, Carlos Pascoal; Rocha, Joao; Belgacem, Mohamed N.; Gandini, AlessandroExtractive-free cork from Quercus suber L. was submitted to organosolv fractionation and the effects of different process variables, such as ethanol/water ratio, temperature, time and the presence of acidic or alkaline catalysts, were studied. The variation of the relative proportions of extracted components, as a function of the processing conditions, could thus be established. Whereas the addition of 0.1 M acetic acid only increased the yield of extracted materials from about 15 to 23%, the use of sodium hydroxide, at the same concentration, produced a jump to 76%. In the case of the alkaline organosolv fractiona tion, an increase in process temperature, time and catalyst concentration led to an increase in the extraction yield, although in some cases this increase did not follow a sustained trend, as in the case of reaction time. Increasing the ethanol/water ratio led to a higher selectivity in favour of suberin extraction. Residual cork from different organosolv processes was characterised by FTIR and 13C solid-state NMR. The latter technique provided some valuable information about both process selectivity and cork morphology, particularly with respect to the positioning of suberin macromolecules in the cell wall.
- 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.