Wettability study and surface characterizacion by confocal laser scanning microscopy of rotary-peeled wood veneers

[ES]El objetivo de este trabajo fue estudiar las propiedades superficiales de chapas obtenidas por desenrollo de cinco especies de maderas duras: okume, ayous, chopo, fromager y eucalipto, y comparar el comportamiento de ambas caras de las chapas. Se han determinado los ángulos de contacto de equilibrio y se ha determinado la energía libre superficial de la madera así como sus componentes polar y dispersa. Asimismo, mediante microscopía de barrido láser confocal se ha evaluado la rugosidad superficial. La energía libre superficial osciló entre 49-64 mJ/m2 y disminuyó en el orden okume > fromager > chopo> ayous ~ eucalipto, lo que indica un descenso de la capacidad de mojado en ese orden. El okume con el mayor valor de la energía libre superficial y los menores valores del ángulo de contacto de equilibrio se confirmó como la especie con las mejores propiedades de mojado, siendo además la que presentó los mayores valores de los parámetros de rugosidad superficial. Comparando las propiedades superficiales para las dos caras de las chapas se encontró que dependieron de la especie, pero en general, con la excepción de la rugosidad, las diferencias no fueron muy significativas siendo los mayores cambios para las chapas de okume que presentaron un mejor mojado en su cara interior.[EN]The aim of this work was to study the surface properties of rotary-peeled veneers of five species of hardwoods: okume, ayous, poplar, fromager and eucalyptus and to compare the behavior of both sides of the veneers. The equilibrium contact angles were determined together with the wood surface free energy and its polar and disperse components. Additionally, surface roughness was evaluated using confocal laser scanning microscopy. Surface free energy ranged from 49-64 mJ/m2 and decreased in the order okume> fromager> poplar> eucalyptus ~ ayous, indicating a decrease in wettability in that order. Okume wood with the highest value of the surface free energy and the lowest values of the equilibrium contact angle was confirmed as the species with the best wetting properties, and also presented the highest values of surface roughness parameters. In general, there were not significant differences between the properties of both sides of the veneers, except for roughness. The largest differences were obtained for okume veneers whose interior side showed higher wettability

Adhesivos Fenol-Urea-Formaldehído Modificados con Taninos para Contrachapados de Uso Exterior

Se han estudiado la formulación y las características de adhesivos fenol-urea-formaldehído-taninos para su aplicación a tableros contrachapados de eucalipto de uso exterior. Los adhesivos se han preparado por copolimerización a temperatura ambiente de taninos de corteza de Pinus pinaster (5-17% en peso de adhesivo final) con prepolímeros fenol-urea-formaldehído previamente elaborados bajo diferentes condiciones de operación. Un estudio reológico ha puesto de manifiesto que la adición de taninos a los prepolímeros modifica sus características reológicas pasando de un comportamiento newtoniano a un comportamiento pseudoplástico en los adhesivos. Esta característica permite reducir considerablemente el consumo de adhesivo en la preparación de tableros contrachapados. En general, los tableros contrachapados de madera de eucalipto preparados han superado las normas europeas de calidad para tableros de uso exterior

Desarrollo de un Adsorbente Basado en Taninos de Corteza de Pinus pinaster

Se han preparado partículas de gel de taninos de corteza de Pinus pinaster empleando un proceso en dos etapas. En la primera etapa (de pre unión cruzada), los taninos reaccionan con formaldehído. En la segunda (de granulación), la disolución taninos-formaldehído parcialmente gelificada se dispersa sobre una mezcla de decalina y un agente tensoactivo no iónico. Se ha analizado la influencia de las condiciones de operación de ambas etapas sobre el rendimiento y características de las partículas obtenidas. Las partículas, ligeramente porosas y prácticamente esféricas, se han empleado para la adsorción de cadmio de disoluciones acuosas. Los espectros de dispersión de rayos X obtenidos tras la adsorción han confirmado la presencia de cadmio sobre la superficie de las partículas y, por tanto, su capacidad para la adsorción de cationes metálicos

Environmentally friendly wood adhesives based on chestnut (Castanea sativa) shell tannins

International audienceThe aim of this work was the formulation of adhesives for particleboards based on tannins extracted from industrial lignocellulosic wastes, namely chestnut shell, chestnut bur and eucalyptus bark. The interest was centred on the possibility of completely removing formaldehyde from adhesive formulations. For this, hardener alternatives to formaldehyde were used: tris(hydroxymethyl)nitromethane (TRIS), glyoxal (GLY) and hexametilentetramine (HEX). The influence of the type and concentration of the hardener and pH on adhesive gel time and pot-life were studied. A comparative structural characterization of the adhesives was performed by 13C-NMR spectroscopy. Thermomechanical analyses (TMA) tests were carried out as an indication of the final strength of the adhesive systems. Particleboards type 2 of interior use (EN 312) were manufactured with adhesives based on chestnut shell tannins alone or mixed with chestnut bur/or eucalyptus bark tannins. Free-formaldehyde was determined, and boards were prepared with TRIS, GLY and HEX tannin adhesives were classified as E0

MALDI-TOF, HPLC-ESI-TOF and 13C-NMR characterization of chestnut (Castanea sativa) shell tannins for wood adhesives

International audienceMALDI-TOF, HPLC-ESI-TOF and 13C-NMR techniques were used to analyse the structure of non-purified aqueous chestnut shell tannin extracts. In addition, the influence of the extraction agent (water or aqueous solutions of Na2SO3 and/or NaOH) on tannin structure was analysed by MALDI-TOF in order to select the extract with the best properties for wood adhesives. Using HPLC-ESI-TOF, catechin/epicatechin, gallocatechin/epigallocatechin, dicatechin structures, dicatechin structures without a hydroxyl group, galloyl-glucoses and ellagic acid were identified as the main monomeric components in the aqueous extract. 13C-NMR and MALDI-TOF spectra revealed that extracts are mostly composed of procyanidin and prodelphinidin structures although prorobinetidins might be also present. MALDI-TOF spectrometry was used to identify the extract oligomeric components. Extractions with Na2SO3 and/or NaOH produced changes in the predominant structures in the extracts and on the amount of sugar units linked to the flavonoid structures, which decreased in the presence of Na2SO3. Extract obtained using low Na2SO3 and NaOH concentrations (1.5 and 0.75 %, respectively) was selected as more suitable for wood adhesive preparation

Estudio del mojado y caracterización superficial por microscopía de barrido láser confocal de chapas de madera obtenidas por desenrollo

The aim of this work was to study the surface properties of rotary-peeled veneers of five species ofhardwoods: okume, ayous, poplar, fromager and eucalyptus and to compare the behavior of both sidesof the veneers. The equilibrium contact angles were determined together with the wood surface freeenergy and its polar and disperse components. Additionally, surface roughness was evaluated usingconfocal laser scanning microscopy. Surface free energy ranged from 49-64 mJ/m2 and decreased in theorder okume> fromager> poplar> eucalyptus ~ ayous, indicating a decrease in wettability in that order.Okume wood with the highest value of the surface free energy and the lowest values of the equilibriumcontact angle was confirmed as the species with the best wetting properties, and also presented the highestvalues of surface roughness parameters. In general, there were not significant differences between theproperties of both sides of the veneers, except for roughness. The largest differences were obtained forokume veneers whose interior side showed higher wettability

Effect of the Extraction Technique and Operational Conditions on the Recovery of Bioactive Compounds from Chestnut (Castanea sativa) Bur and Shell

The aim of this work was to study the extraction of phenolic compounds from chestnut bur and shell, both waste products of chestnut processing in the food industry. Two extraction techniques were compared—maceration with solvents and microwaveassisted extraction. The influence of the solvent used (water, 50% MeOH or 50% EtOH) and temperature (25-50-75 C) on extraction yield and extract total phenols content and FRAP, DPPH, and ABTS antioxidant activities was studied. In the conventional extraction, the yield was significantly higher for the bur (8.54–19.58%) than for the shell (2.91–13.27%); however, the shell extracts showed substantially greater properties. The best extract properties were achieved at 75 C using 50% MeOH for the bur and water for the shell and phenolic compounds with demonstrated antioxidant properties, as gallic acid esters of glucose and ellagic acid, were identified in these extracts by RP-HPLC-ESI-TOF. In addition, the aqueous extracts showed ability to inhibit the growth of gram positive and negative bacteria but not fungi. The kinetic of the extraction process was well fitted by the Peleg’s model. The non-conventional microwaveassisted extraction slightly improved the chestnut bur extraction by reducing the extraction time.This work was funded by Ministerio de Ciencia e Innovación, FEDER Funds and Plan E Fundy (CTQ2009-07539) and Fundação para a Ciência e Tecnologia (Portugal) PEst-OE/AGR/UI0690/2011. The authors are also grateful to ‘‘Fundación Segundo Gil Dávila’’ for a research grant awarded to Adela Fernández Agull