Sistema Regional de Información
en línea para Revistas Científicas de América Latina,
el Caribe, España y Portugal

Special tubular fiberboard with a density of 550 kg/m3 was manufactured using the round rods for creation of the holes. Physicomechanical properties of tubular fiberboard (6, 8, 10, 12 (mm)) with various hole diameters and number of hole (0, 1, 2 and 3 in a constant cross section) were evaluated. The surface layers density, especially on top of the holes, considerably elevated with increasing the hole diameter. This did create higher bending properties as well as higher internal bond and surface soundness. The structure of webs between the holes, when the holes’ number increases, were predominant factor influencing the panel properties. Weak and loose web structure were obtained by increasing the holes’ number from 1 to 3 within a constant cross section (50 mm × 16 mm) that was due to the less transferred fiber during pressing in the webs’ sections. A corresponding comparison of panel properties with those in American and European standards presents that the minimum requirements according to most of the standards (ANSI A208/2, EN 14755, EN 312/P2 and EN 622-5/P1) were obtained.

Chemical modification with acetic anhydride is an effective method to stabilise wood against dimensional movement and improve decay resistance of wood. It has also been reported to retard UV light induced color darkening on wood surface. Coatings of wood surfaces with certain nano metal oxides have also shown promise as UV screening agent. In this work, we have evaluated synergistic effect of acetylation of wood and application of nano material on wood surfaces to enhance their UV stability. Photo-stability of acetylated Wrightia tinctoria wood coated with zinc oxide (ZnO) nanodispersion was evaluated by irradiating these wood specimens to UV radiation in an accelerated weathering tester. Acetylation of wood with acetic anhydride exhibited photo-bleaching and inhibited light-induced color darkening observed in unmodified wood. Coating of unmodified and modified wood surfaces with ZnO nanodispersion reduced photo-discolouration and degradation of wood polymers. The photo-bleaching observed in chemically modified wood upon light irradiation was further enhanced by application of nano coating on wood surfaces.

This study set out to determine which environmental factors of growth and silvicultural practices can affect the properties of Eucalyptus robusta coppice wood and also to study variability in those properties depending on the factors. Hundred and thirty-five coppice logs aged 2 to 10 years were collected from five zones in the Highlands of Madagascar. Wood density at 12% moisture content was measured by X-ray microdensitometry. Chemical properties, such as the total extractives, Klason lignin and holocellulose contents were predicted using near infrared spectrometry prediction models. The results significantly showed (p-value<0.001) that wood density (0.543 – 0.836 g.cm-3), total extractives (3.1 – 9.8%) and Klason lignin content (24.6 – 35.3%) increased with age, with the opposite occurring for holocellulose (63.8 – 69.9%). Wood density also varied significantly (p-value<0.001) depending on the zones, which was not the case for chemical properties. The densest woods were found at the hottest zones with less acid soils. Woods were less dense in zones, characterized by high rainfall and a soil rich in nitrogen and organic carbon. The plantation spacing, elevation of the zone and soil texture did not significantly affect wood properties.

In this research, we used Pistacia atlantica gum during cooling phase of oil-heat treatment of poplar wood (Populus deltoids) to improve its resistance to the white-rot fungus Trametes versicolor and growth of the mold fungus Penicillium expansum. Thermal modification was carried out using rapeseed oil at 180 °C, 200 °C and 220 °C for 2 hours and 4 hours. The modified wood specimens were then directly cooled in the oil containing 0 %, 5 % and 10 % (w/w) of the gum at 25 °C for 30 minutes. The chemical constituents of the essential oil extracted with a Clevenger type apparatus were determined by chromatography–mass spectrometry (GC-MS). The amounts of α-pinene, β-pinene and α-terpinolene of the essential oil were 60,2 %, 8,7 % and 3,9 %, respectively. The mold resistance was greatly improved, while the improvement against the decay fungus was only observed for the specimens modified at 180 °C. Our results confirmed that the enhanced fungal resistance was not only due to the presence of monoterpenes in the essential oil, but also to a further reduction in the hygroscopicity of the treated wood.

We investigated the effect of adding nano-wollastonite on the physical, mechanical and morphological properties of gypsum Composites. The ratio percentage of bagasse mixing as lignocellulosic material with gypsum at three levels (85:15; 75:25; 65:35) and nano-wollastonite at three levels of 0 %, 5 % and 10 %. Specimens were prepared according to the ISO 11925 specifications for the fire resistance (weight loss) properties and according to the DIN EN 634-1: 1195-04 specifications for the mechanical and physical properties. Scanning Electron Microscopy (SEM) were also used to study the properties of composite morphology and distribution of samples. The results showed that by increasing the amount of nano wollastonite, physical and mechanical properties improved. The MOR, MOE and IB of boards decreased with increased bagasse usage amount, and its maximum value was obtained in using 15 % bagasse. The results also showed that increasing the amount of bagasse in boards caused a significant increase in the TS of the boards. The results from microscopic images showed that the optimal level of nano-wollastonite can fill the empty holes and create a uniform structure, thereby improving the properties of the boards.

This evaluated the natural resistance of wood from seven Eucalyptus trees in field decay and soil bed tests. Two 12-year-old trees were randomly sampled per species, with 2,2 m logs being obtained from the  basal section of each tree. The samples were taken in two positions in the radial direction of the stem (middle heartwood and transition zone; containing heartwood and sapwood). The field decay tests were installed in three municipalities in the southern state of Espírito Santo, and the soil utilized soil from the three field decay test areas. The field decay tests were evaluated after six, 12 and 18 months after installation and the soil bed tests after six months. The Scott-Knott test (p ≤ 0,05) was used in the analysis and evaluation of the tests. The sapwood-heartwood (transition region) exhibited the greatest mass losses for the field decay and soil bed tests. On average, for the soil bed test the lowest mass losses were observed for the soil of Vargem Alta (5,00 %), with greater mass losses observed for São José do Calçado (7,05 %) and Jerônimo Monteiro (9,90 %). In the field decay test the organisms present in the soil of São José do Calçado and related to the organic matter content Eucalyptus grandis and Eucalyptus saligna more intensely.

Eucalyptus is one of the most fast-growing trees. Therefore, in the last decades it has been extensively planted and harvested so that nowadays Eucalyptus is one of the most popular trees of the planet. There are many genres of this plant and they are often treated as a large bunch of the same timber characterized by moderate mechanical and surface properties which hinder their usage for any sight application (e.g. flooring, cladding, ceiling). In this study four species of Eucalyptus: E. grandis, E. dunnii, E. cloeziana and E. tereticornis were undergone to densification through hydro-thermo-mechanical treatment (HTM) first and then to oil heat-treatment (OHT) in order to improve their mechanical properties and hydrophobicity. It was observed that low density species (E. grandis) reaches higher compression degrees while heavier species (E. tereticornis) reach densities over 800 kg/m³; however, HTM decrease the variability of the properties. Treatments at higher temperature (160 °C) involves higher compression degree, lower set-recovery and higher surface hydrophobization, but also weaker mechanical properties. The hot oil post- treatment helps to contain the springback effect and to reduce the wettability of each specimen. Densified samples present similar surface hardness. The tailored application of the two treatments improves the properties of every Eucalyptus which can gain market also for nobler end-usages.

The aim of this study was to know the variation profile of the specific energy consumption required to cut woods with varying densities and moisture contents. Therefore, peripheral cuts were performed in the longitudinal direction of the grain with numerical control controlled by Computational Numerical Command in woods of different densities, established at different drying stages. An energy analyzer, capable of calculate the specific energy consumed during the wood processing, was used to measure the energy information. The results indicated that the higher the wood density, the greater the positive influence of the moisture content on the specific cutting energy. In the anhydrous condition, the higher the wood density, the higher the cutting energy. With increased moisture content, less cutting power was required during the wood processing. Therefore, it was possible to conclude that during the milling type mechanical processing of wood, moisture content has a great influence on the specific cutting energy consumption.

This study aims to evaluate the free and bound water flows in the different axes of Corymbia citriodora wood during drying. Wood samples were taken from the inner and outer regions of the tree stem from seven-years-old experimental plantations. The blocks were prepared for the water flow to occur in each wood axis and they were dried up to the final moisture content of 12%. Free water (FWFR), bound water (BWFR) and total water (TWFR) flow rates were calculated. The relationship between loss of moisture content and time presented an exponential curve, especially in the radial and tangential wood axes. Water flow in the three wood directions presented higher FWFR than TWFR (which was higher than BWFR). Free water flow was ~10 times higher than adsorbed water flow, considering values for moisture content between ~80% to ~12%. Free water movement in the longitudinal direction of the wood was ~2 times greater than in the radial axis and ~3 times greater than in the tangential axis. Bound water movement in the longitudinal direction of the wood was ~2 times greater than in the transverse direction. Bound water flow in the radial axis of the wood was statistically equal to the one in the tangential axis. The results indicate that the intensity of free and bound water flows changes according to the direction of Corymbia citriodora wood.

In the present study, three juvenile hardwoods (namely sycamore, pecan and london plane) were treated by boiling, steaming and microwave. Trees from Platanus x acerifolia (sycamore), Carya illinoinensis (pecan) and Luehea divaricata (london plane) were selected in homogeneous forests located in southern Brazil. Each hydrothermal treatment was performed for 60 min. In general, the hydrothermal treatments caused a certain surface inactivation effect, which was marked by decreased surface roughness, increased hydrophobic character and darkened colour patterns. Also, both decreased stiffness and strength, as well as increased deflectibility were obtained. These mechanisms were attributed to degradation in fine segments from amorphous polysaccharides, leaching of some organic extractives and fragmentation of lignin, as indirectly indicated by infrared spectra.