Browsing by Author "Fernandes, Ana Paula"
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- Adhesives from liquefied eucalypt bark and branchesPublication . Esteves, Bruno; Cruz-Lopes, Luisa; Fernandes, Ana Paula; Martins, Jorge Manuel; Domingos, Idalina; Ferreira, José; Silva, Silvia Helena Fuentes; Labidi, JalelAdhesives made from lignin are one of the most promising alternatives to common ureaformaldehyde adhesives. One of the possible sources is from wood or bark liquefaction at low temperatures and pressure. The possibility of using forest wastes for the production of adhesives was the objective of this work. Eucalypt bark and branches are wastes produced in the company Pedrosa & Irmãos, which is a forest management company based in Portugal (Leiria). The wastes were liquefied with polyalcohols catalyzed by sulfuric acid. The water insoluble fraction of the liquefied material was used for the production of the bio-adhesive. Both fractions were characterized and the bonding performance of the bio-adhesive was tested by ABES. The bio-adhesives obtained from bark or branches were similar, exhibiting a bonding strength approximately half of the conventional UF resin.
- Eco Valorization of Eucalyptus globulus Bark and Branches through LiquefactionPublication . Fernandes, Ana Paula; Cruz-Lopes, Luísa; Dulyanska, Yuliya; Domingos, Idalina; Ferreira, José; Evtuguin, Dimitri; Esteves, BrunoEucalyptus globulus forest residues, bark, and branches, were characterized by wet chemistry methods and involved in the liquefaction process using a glycerol-ethylene glycol reaction mixture (1:1, v/v) catalyzed by strong mineral acid (3% H2SO4) or strong mineral base (6% KOH). The effect of the reaction conditions (temperature and duration) and the particle size on the yield of liquefied products have been evaluated. Acid catalysis revealed remarkably higher yields (25–50%) than when using basic catalyst. It was considered that bark was more vulnerable to liquefaction with respect to particle size than branches. Too high temperatures (>180 °C) are not advantageous regarding the liquefaction yields and, therefore, temperatures around 160–180 °C would be preferable. The best yield for the bark sample (>80 mesh fraction) was obtained at 180 °C for 60 min (61.6%), while for the branches the best yield was obtained at 160 °C for 60 min (62.2%). Under compromised conditions (180 °C for 60 min), the fine fraction (>80 mesh) of bark and branches did not show significant differences between their liquefaction yields and can be processed together while adjusting the suitable processing time. The main advantage of the use of these residues instead of solid wood is that it would bring the Forest managing companies a much higher income for their wastes that are usually burned and the use of lignocellulosic materials in detriment of petroleum-based materials for the production of polymers would make industry less dependent on oil prices fluctuations.
- Occurrence of cellobiose residue directly linked to galacturonic acid in pectic polysaccharidesPublication . Nunes, Claudia; Guiné, Raquel; Silva, Lisete; Fernandes, Ana Paula; Domingues, M. Rosário; Coimbra, Manuel A.Pectic polysaccharides are present in all plant cell walls. These polymers are constituted by different associated polysaccharides, such as homogalacturonan, xylogalacturonan, rhamnogalacturonan type I, rhamnogalacturonan type II, arabinan, and arabinogalactan [1]. This work describes the structural features of pectic polysaccharides extracted from plum (Prunus domestica L.) and pear (Pyrus communis L.) cell walls and commercial pectin, obtained from Citrus. The alfa-(1→4)-D-galacturonic acid backbone was submitted to a selective hydrolysis with endo-polygalacturonase (EPG) and the fractions with low molecular weight (< 1000 kDa) obtained by size-exclusion chromatography were analysed by mass spectrometry using electrospray ionisation (ESI-MS and ESI-MSn) and by methylation analysis The ESI-MS spectra obtained revealed the presence, in all samples, of several [M+Na]+ ions of pectic oligosaccharides identified as belonging to different series, including oligosaccharides constituted only by galacturonic acid residues (GalAn, n=1-5) and galacturonic acid residues substituted by pentose residues (GalA3Pentn, n=1-2). Surprisingly, it was also observed the occurrence of galacturonic acid residues substituted by hexose residues (GalAnHexm, n=2-5, m=1-2). The fragmentation of the observed [M+Na]+ ions, obtained under ESI-MS/MS and MSn allowed to confirm the proposed structures constituent of these pectic oligosaccharides. Furthermore, the ESI-MSn spectra of the ions that could be identified as GalAnHexm (n=2-5, m=1-2) confirmed the presence of Hex or Hex2 residues linked to a GalA residue. Methylation analysis showed the presence, in all EPG treated samples, of terminally- and 4-linked glucose. These results show that pectic polysaccharides from different origins (plum, pear, and citrus) and structural features (different proportions of branching residues) have Glc residues directly linked to GalA as single residues or as cellobiose residues. The occurrence of GalA substituted by Glc, and Glc-beta-(1→4)-Glc are structural features that, as far as we know, have never been reported to occur in pectic polysaccharides.
- Polyurethane Foams from Liquefied Eucalyptus globulus BranchesPublication . Domingos, Idalina; Fernandes, Ana Paula; Ferreira, José; Cruz-Lopes, Luísa; Esteves, BrunoCurrently, polyurethane (PU) production is completely dependent upon fossil oil, as the two primary reagents necessary for PU production, polyol and isocyanate, are derived from fossil fuels. Eucalyptus branches are waste products for most forest management companies. In this work, polyols obtained by the liquefaction of eucalyptus branches were used for foam production. The influence of the isocyanate, catalyst, surfactant, and blowing agent contents on the foam properties was studied. Overall the amount of each chemical used in the production of PU foams had a noticeable effect on the density and compressive properties. The amount of water (blowing agent) had the strongest effect and decreased the density and compressive properties because of higher foam expansion. The other chemicals increased or decreased the density and compressive stress depending on the amount used. The density of the produced foams ranged from 36 kg/m3 to 108 kg/m3, the compressive stress ranged from 15 kPa to 149 kPa, and the Young’s modulus ranged from 64 kPa to 2100 kPa. The results showed that it is possible to convert these forest residues into PU foams with properties somewhat similar to those of commercial foams, although with a lower compressive strength.