Scielo RSS <![CDATA[Maderas. Ciencia y tecnología]]> vol. 20 num. 2 lang. es <![CDATA[SciELO Logo]]> <![CDATA[Kraft scrap paper pulp as a substitute of wood chips in manufacture of particleboards resinated with hybrid pf/pmdi resin]]> Abstract: This study analyzed feasibility of manufacture of composite particleboards resinated with a mixture of phenol-formaldehyde resin and 4,4′-methylenediphenyl isocyanate in the weight ratio 70:30. For this purpose 3-layer particleboards were produced with varying shares of Kraft scrap paper pulp in the core. Experimental boards were manufactured applying 0, 10, 15, 25, 50 and 75% substitution of wood chips with Kraft paper pulp. Analyses were conducted to determine physico-mechanical properties of boards, i.e. bending strength, modulus of elasticity, internal bond before and after the boiling test and swelling in thickness after 24 soaking in water. Based on recorded testing results it was stated that moisture resistant composite boards manufactured with a 25% substitution of wood chips with Kraft paper pulp meet the requirements of the EN 312 standard for boards used in humid conditions in terms of their strength and moisture resistance specified in the internal bond after the boiling test. <![CDATA[Efecto del ataque de <em>Leptocybe invasa</em> en plantaciones de eucalipto destinadas a la producción de pulpa de celulosa kraft]]> Resumen: El objetivo de la investigación fue evaluar el efecto del ataque de Leptocybe invasa en las propiedades dendrométricas de la madera de dos clones de eucalipto (Eucalyptus urophylla y Eucalyptus tereticornis), cultivados en los municipios de Imperatriz (Estado do Maranhão) y Darcinópolis (Estado de Tocantins), Brasil, destinados a la producción de pulpa kraft. Se analizaron 10 árboles de 3 años de edad atacados por Leptocybe invasa, para cada clon. El diagnóstico fue basado en la formación de grandes agallas en la copa, y con orificio de emergencia (cerrando el ciclo). Los resultados fueron constatados por la variación de las características de las especies evaluadas con relación a su altura total, diámetro, volumen de corteza, frecuencia de vasos, longitud de fibras, perfil radial de densidad y contenido de cenizas. Los árboles hospederos presentaron alteraciones en las variables dendrométricas, contenido de pentosanos y cenizas en la madera para ambos materiales genéticos, no siendo observadas variaciones en la densidad básica, dimensión de vasos y fibras, así como en los contenidos de lignina y extractivos de la madera.<hr/>Abstract: The aim of the research was to evaluate the effect of the attack Leptocybe invasa in dendrometric variables and wood properties of two clones of eucalyptus (Eucalyptus urophylla and Eucalyptus tereticornis), grown in the municipalities of Imperatriz (state of Maranhão) and Darcinopolis (state of Tocantins), Brazil, for Kraft pulping. Data were collected 10 trees for each clone, the 3-year-old attacked by L. invasa. The diagnosed was based on formation of large guts all over the glass, and emergency hole (closing the loop). The results were confirmed by the variation of the characteristics of species assessed relative to their total height, diameter, volume of bark, vessel frequency, fiber size, radial density profile vessel frequency, fiber size, radial density profile, and ash content. Host trees obtained alterations in dendrometric variables, content of pentosans and wood ashes for both genetic materials, not being observed variations in specific gravity, and size of vessels and fibers, as well as the contents of lignin and wood extractives. <![CDATA[An exploratory evaluation of the pulpability of <em>Brachystegia spiciformis</em> and <em>Pericopsis angolensis</em> from the angolan miombo woodlands]]> Abstract: Brachystegia spiciformis and Pericopsis angolensis are two hardwood species found in the Miombo woodlands. The wood features, kraft pulping and strength pulp properties of both species were evaluated in order to determine their potential as raw material for papermaking. Brachystegia spiciformis wood density was 640 kg m-3 and Pericopsis angolensis was 795 kg m-3. Pericopsis angolensis wood has higher cell wall thickness and occluded fibre lumen as remarkable anatomical properties. Runkel ratio, slenderness ratio, and the coefficients of flexibility and rigidity in Brachystegia spiciformis were 1,5; 65,7; 41,2% and 29,4% while in Pericopsis angolensis these values were 17,6; 59,9; 5,4% and 47,3%, respectively. Brachystegia spiciformis has a higher cellulose content, lower hemicellulose and lignin content, and higher S/G ratio than Pericopsis angolensis. In kraft pulping, a higher demand of active alkali was needed for both species, and pulps with high kappa number (24-27) and low pulp yield (40%) were obtained. Pericopsis angolensis pulps reached tensile, tear and burst indexes of 99,6 Nm g-1; 5,9 mN.m2 g-1 and 4,9 kPa.m2 g-1, respectively. Brachystegia spiciformis pulps reached tensile, tear and burst indexes of 100,3 Nm g-1; 10,7 mN.m2 g-1 and 6,1 kPa.m2 g-1, respectively. As a conclusion, Brachystegia spiciformis wood has better pulpability than Pericopsis angolensis wood, according to its pulps properties, despite of the similar pulp yield between both species. Both species may be suitable for unbleached wrapping papers and rigid cardboards manufacturing. <![CDATA[Discrimination of wood and charcoal from six Caatinga species by near-infrared spectroscopy]]> Abstract: Correct identification of species in wood and charcoal commerce is important, and rapid and nondestructive evaluation based on near-infrared techniques can be a good alternative. Four trees from Combretum leprosum, Croton argyrophylloides, Jatropha mutabilis, Luetzelburgia auriculata, Mimosa tenuiflora and Poincianella bracteosa, were cut in a natural forest in the municipality of Coremas, Paraíba state and stem discs with thickness of about 80 mm were taken at 0, 25, 50, 75 and 100% of commercial height. For charcoal production, each sample was wrapped in aluminum foil and carbonized in a muffle furnace, with a final temperature of 450 °C and a heating rate of 1,66 °C min-1. Spectra were collected directly from sample surface. The best pretreatment was second derivative, while the best classification method was PCA-LDA, and the analysis of full spectra (4000-10000 cm-1) was indicated. In classification, there was no difference between surfaces where spectra was collected, so in practice, in commercial control for example, the information can be obtained from any surface. For rapid analysis for purposes of control of forest practices or illegal commerce, spectra collected directly from wood and charcoal can be applied to distinguish these six Caatinga species. <![CDATA[Liquefaction behaviour of twelve tropical hardwood species in phenol]]> Abstract: Liquefaction of ligno-cellulosic biomass is one of the chemical conversion technologies for developing new materials, adhesives and energy systems. The liquefaction process also provides an opportunity to utilize ligno-cellulosic wastes such as saw-dust, woody wastes, branches and twigs, agro-residues, etc. for the development of value added products. This paper presents the liquefaction behaviour of wood meal of twelve tropical hardwood species in phenol as liquefying media to produce chemically active liquid which has potential to be used as a raw material for developing different products. The liquefaction was carried out at 140°C temperatures for 120 minutes at different liquid ratios. In all the cases, a viscous and sticky black liquid was obtained after the stipulated reaction time. The liquefaction efficiency was found to vary with species and liquid ratio. The highest liquefaction efficiency of 93% was achieved in balsa wood at 1:3 (wood: phenol) liquid ratio. The liquefied wood and residues were characterized by FTIR spectroscopy. The liquefied wood was found to be highly acidic in nature. Viscosity of liquefied wood at higher liquid ratio was independent of wood species. Correlation analysis revealed a strong negative relationship between wood basic density and liquefaction efficiency. <![CDATA[Estudio de cinética en procesos termogravimétricos de materiales lignocelulósicos]]> Resumen: La madera de pino representa el 20% de las especies forestales plantadas en todo el mundo, y actualmente es de vital importancia en aplicaciones industriales como en aserrío, fabricación de papel y medicina. Actualmente, se ha destacado su uso en aplicaciones energéticas. En este estudio se presenta una breve revisión sobre el análisis térmico realizado a diversas especies de madera de pino. Se enfoca principalmente al análisis de los resultados respecto a cómo varía el contenido de masa o pérdida de peso con el cambio de temperatura a partir del análisis de las curvas de termogravimetría y su derivada. Se considerarón diversas especies de madera de pino: Pinus caribaea, Pinus patula, Cupressus sempervirens, Pinus pinaster, Pinus radiata, Pinus sylvestris, Pinus pinea y Pinus taeda. Con el objetivo de mostrar las diferencias y similitudes respecto a la estabilidad térmica de las especies mencionadas, se han discutido los principales parámetros a partir de las curvas de termogravimetría como energía de activación, factor pre-exponencial y orden de reacción. Además, se examinan las etapas de descomposición de acuerdo a los principales componentes de la madera tales como agua, celulosa, hemicelulosa, lignina y extractivos.<hr/>Abstract: Pine wood accounts for 20% of the world's planted forest species, and is currently of vital importance in industrial applications such as sawmills, papermaking and medicine. Actually, its use in energy applications has been emphasized. This study presents a brief review on the thermal analysis of various species of pine wood. We focus mainly on the analysis of the results regarding how the mass content or weight loss varies with the temperature change from the analysis of the thermogravimetric curves and its derivative. Several species of pine wood have been considered: Pinus caribaea, Pinus patula, Cupressus sempervirens, Pinus pinaster, Pinus radiata, Pinus sylvestris, Pinus pinea and Pinus taeda. In order to show the differences and similarities with respect to the thermal stability of the mentioned species, we have discussed the main parameters from the thermogravimetry curves such as activation energy, pre-exponential factor and reaction order. In addition, the decomposition stages are examined according to the main components of the wood such as water, cellulose, hemicellulose, lignin and extractives. <![CDATA[Microstructural characterization and evaluation of certain important physical properties of thuja burl wood]]> Abstract: This investigation aimed to characterize certain important anatomical, chemical and physical properties of Tetraclinis articulate (Thuja) burl wood from Morocco. Anatomical properties and constituent structure were analysed using image analysis system, environmental scanning electron microscope (ESEM) and powder x-ray diffraction techniques. A few important physical properties of Thuja burl wood such as density, specific gravity, equilibrium moisture content (EMC), total swelling and water absorption characteristics were evaluated. Real-time water absorption and swelling profiles were recorded electronically using a digital force sensor and linear variable differential transformers (LVDTs) respectively. Microscopic structure observed on fractured surfaces showed very compact and thread-like fibers. Average crystallinity index and diameter of cellulose crystallite was found to be 0,35±0,03 and 36±5,58 Å respectively. The average values of air-dry density and the EMC of Thuja burl wood were 932,67±50,57 kg/m3 and 10,19±1,43% respectively. Swelling profile as a function of the water immersion duration followed a curvilinear variation with maximum swelling coefficient of 2,9±0,43% after 24 hour from oven-dry condition. The suitability of this wood for decorative and handicraft items is attributed mainly to its dense microstructure, higher dimensional stability, lower water absorption, random grain texture, dark brownish with intense and pleasant smell. <![CDATA[Wettability of the surface of heat-treated juvenile teak wood assessed by drop shape analyzer]]> Abstract: This study investigated the effect of the heat treatment on the wettability of the surface of juvenile teak (Tectona grandis) wood assessed by drop shape analyzer. Heartwood and sapwood samples were heat-treated at 180 and 200ºC. Contact angle measurements were done every 5 s for 120 s using a KRÜSS DSA100. Heartwood had lower wettability than sapwood. Heat-treatment decreased the surface wettability of both heartwood and sapwood, especially in the wood treated at 200ºC. Heartwood had lower wettability than sapwood, even after heat treatment. <![CDATA[Ten-year field study of wood plastic composites in Santiago, Chile: biological, mechanical and physical property performance]]> Abstract: Outdoor durability of wood plastic composites is a major focus of research and development efforts toward development of more robust building materials. Exterior exposure of wood plastic composites can result in weathering, moisture absorption, fungal and termite attack to various levels of severity depending on the composite formulation. Long-term (&gt; 6 years) field exposure studies of wood plastic composites are lacking in the scientific literature. It is the overall goal of this paper to report on a ten-year field study of wood plastic composites performed in Santiago, Chile. The wood plastic composite formulations were comprised of polypropylene, wood flour, and various additives. Qualitative measurements were made on the stakes each year including the determination of decay and termite ratings on a scale of 1 to 10 as specified in American Wood Preservers’ Association Standards. Surface weathering or discoloration, surface fungi colonization, presence of mold, and/or lichen was noted. The amount of dimensional change (swelling) of the samples in ground contact was determined. Determination of flexural properties of the control and 10-year exposed wood plastic composite stakes were conducted. All the wood plastic composite stake formulations maintained excellent performance ratings after the 10-year field exposure with ratings of 10 for decay and 10 for termites. The wood plastic composites stakes experienced swelling in contact with the soil with the majority of swelling occurring during the first year of exposure. Although the wood plastic composite stakes did well regarding decay and termite performance, the portion of the stakes exposed above ground exhibited various amounts of weathering, surface fungal colonization, and mold and mildew depending on the formulation. Flexural properties of the wood plastic composite stakes decreased or were maintained for the 10-year exposure depending on the composite formulation. <![CDATA[Mechanical parameters of thermally modified ash wood determined on compression in tangential direction]]> Abstract: Mechanical parameters of ash wood (Fraxinus excelsior) subjected to compression in tangential direction, before and after its thermal modification and measured at the moisture content close to the equilibrium moisture content of wood used inside and outside the house, (4 and 12%) were compared. Thermal modification of wood was performed at 190(C and 200(C for 2 hours in industrial conditions. During the measurements, the moisture content of the modified and control samples was the same. The parameters compared included: modulus of elasticity, stress at proportionality limit, relative linear strain at proportionality limit and accumulated elastic energy. Thermal modification of ash wood at 190°C contributed to the deterioration of its mechanical parameters determined during compression in tangential direction; the deterioration was greater for wood tissue of higher moisture content. The values of mechanical parameters of thermally modified wood (except for elastic energy), determined in compression test in tangential direction, decrease with the its increasing moisture more than for the control wood. <![CDATA[Production of blockboard from small athel slats end-glued by different type of joint]]> Abstract: This study evaluated the effect of joint type of short athel (Tamarix aphila) slats at three levels (butt joint, mitered joint, and half lap joint) in core layer veneer consisting of three wood species (Fir, Beech, and Oak). The joints were glued with PVAc and sandwiched by veneers with different ratios of melamine formaldehyde/urea formaldehyde resin (0:100, 25:75, and 50:50) in glue line to determine the modulus of rupture in dry and wet conditions. It was found that the highest dry and wet modulus of rupture was obtained in specimens having slats jointed with half lap joint veneered with fir by using MF/UF ratio of 50:50. The maximum modulus of rupture parallel to the face/back veneer grain value in dry condition (83,40 MPa) was observed to be higher than those values of modulus of rupture perpendicular to the face/back veneer grain (65MPa). However, the maximum modulus of rupture parallel to the face/back veneer grain value (53MPa) in wet condition were observed to be smaller than those values of modulus of rupture perpendicular to the face/back veneer grain value (56MPa). <![CDATA[Modelos descriptivos de distribución de madera juvenil y madura en <em>Robinia pseudoacacia</em>]]> Resumen: Los objetivos del trabajo fueron 1- Determinar los patrones de variación axial y radial de la densidad de la madera y longitud de fibras en el fuste de Robinia pseudoacacia, 2- Determinar la edad de transición entre madera juvenil y madera madura, 3- Construir un modelo descriptivo de distribución de la madera juvenil en el fuste en base a la densidad de madera y longitud de fibras. Se cortaron rodajas a 4 alturas en el fuste (0,3 m; 1,3m; 2,3m y 4m a partir del suelo) en 10 árboles (7-15 años) implantados en Buenos Aires, Argentina. Se determinó la densidad normal12% y la longitud de fibras en probetas radiales obtenidas cada 3 anillos de crecimiento en todas las alturas. La densidad de la madera mostró una homogeneidad de los valores a lo largo del fuste comercial (variación axial), con un rango que la clasifica como madera semi-pesada (750 - 823 kg/m3). La longitud de fibras mostró aumento radial de sus valores de médula a corteza y sin variaciones axiales. El modelo de madera juvenil se asemeja al modelo de cilindro central pero de menor diámetro en el ápice. El cono juvenil se formaría hasta la edad de 3-6 años.<hr/>Abstract: The objectives of the work were 1- to determine the patterns of axial and radial variation of wood density and fiber length in the loge of Robinia pseudoacacia, 2- to determine the transition age between juvenile and mature wood, 3- Construct a descriptive model of distribution of juvenile wood in the log based on wood density and fiber length. Slices were cut at 4 heights in the trunk (0,3 m; 1,3m; 2,3m y 4m above the ground) in 10 trees from Buenos Aires-Argentina (7-15 years old) implanted in the Province of Buenos Aires. The normal density12% and fibre length were determined in radial specimens obtained every 3 growth rings at all heights. The density showed homogeneity values along the commercial shaft, with a range of magnitude that classified as semi-heavy wood (750 - 823 kg/m3). The fiber length showed radial increase of their values from pith to bark and no axial variations. The model of juvenile wood resembles the model of central cylinder but of smaller diameter at the apex. The juvenile cone would form until the age of 3-6 years.