Scielo RSS <![CDATA[Maderas. Ciencia y tecnología]]> vol. 22 num. 4 lang. pt <![CDATA[SciELO Logo]]> <![CDATA[Variability in the physico-chemical properties of wood from <em>Eucalyptus robusta</em> depending on ecological growing conditions and forestry practices: The case of smallholdings in the Highlands of Madagascar]]> Abstract: 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&lt;0,001) that wood density (543 - 836 kg/m3), 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&lt;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. <![CDATA[Hydrothermal treatments to promote surface inactivation and increased flexibility in three hardwoods]]> Abstract: 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. <![CDATA[Durability of Eucalypts wood in soil bed and field decay tests]]> Abstract: 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. <![CDATA[The efficiency of <em>Pistacia atlantica</em> gum for increasing resistance of rapeseed oil-heat treated wood to fungal attacks]]> Abstract: 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. <![CDATA[Enhancing mechanical and surface properties of <em>Eucalyptus</em> wood]]> Abstract: 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. <![CDATA[Cutting energy required during the mechanical processing of wood species at different drying stages]]> Abstract: 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. <![CDATA[Estimation model of mechanical properties from the compressive strength values]]> Abstract: To ensure the safety of wooden structures, estimation of wood strength is based on the characteristic strength values. The Brazilian standard (NBR, in Portuguese Norma Brasileira Regulamentadora) 7190 proposes equations to estimate the strength properties with a simplified procedure, which allows obtaining the characteristic values through relations that correlate different mechanical properties. Using these equations, the values of tensile (f t0,k) and shear (f v0,k) strength can be calculated in a simplified way from the compressive strength (f c0,k) values. In the present work, 36 tropical hardwood species were evaluated for tensile, shear and compressive strength in the direction parallel to the grain, with a total of 1296 experimental measurements, and the precision of the relations defined by the Brazilian standard was assessed using the analysis of variance (ANOVA) method. Two-parameter regression models, based on linear, exponential, logarithmic and geometric functions, were used as an alternative proposal for the estimation of the strength properties. The statistical analysis validated the proposed relations, with the linear (f t0,k) and geometric (f v0,k) regression models being the models of best fit, with the coefficients of determination (R2) equal to 63,02 % and 70,15 %, respectively. In addition, new simplified equations were suggested. The least squares method was used to determine the optimal coefficient (α) for validation of the Brazilian standard equations. The obtained coefficients validated the tensile strength relationship (f t0,k = f c0,k / 0,77), but failed to validate the shear strength relationship (f v0,k = 0,12∙ f c0,k). In the latter case, the obtained values were significantly higher (up to 91 % higher) when compared to those estimated by the Standard. <![CDATA[Analysis of glue line and correlations between density and anatomical characteristics of <em>Eucalyptus grandis</em> × <em>Eucalyptus urophylla</em> glulam]]> Abstract: This study aimed to analyze the glue line thickness effect and its relation with the density and anatomical characteristics of eucalyptus wood. Thus, the thickness of main and secondary glue lines was measured as well as their interaction with the apparent density of elements glued with resorcinol-formaldehyde (RF) and castor oil polyurethane (CP) adhesives. Anatomical wood characterization of Eucalyptus grandis × Eucalyptus urophylla was performed by correlating glue line thickness. According to normative instruction, specimens were produced for delamination tests. The experiment was conducted in a completely random 2 × 2 design factorial scheme (two classes of wood apparent density and two adhesives). Pearson correlation (t &lt; 0,01) was performed among variables. It was found that there was adhesive penetration into vessels and rays of wood. Glue line thickness was higher in woods with density higher than to 580 kg/m3 glued with RF adhesive. There was a low correlation between wood density and vessel diameter to main and secondary glue lines (t &lt; 0,01). <![CDATA[Uptake of insecticides and fungicides by impregnable and refractory coniferous wood species treated with commercial bio-based emulsion gel formulations]]> Abstract: Even in dry state, wood can be prone to biological degradation. Preservation is a prerequisite to confer protection and durability to wood. This is conventionally achieved by impregnating the wood with pesticides. A key point in these treatments is the complex process of wood penetrability. We focused on the relation between the penetration of wood preservatives, wood microstructure, and the physical characteristics of formulations in the impregnation of the easily impregnable pine (Pinus sylvestris), and the refractory spruce (Picea abies). In this work, specimens from the two species were impregnated with three types of commercial bio-based emulsion gels formulations containing insecticides and fungicides. The effect of treatment method using dipping, surface spraying, and vacuum-impregnation, on the retention of the active agents was analyzed. Visual assessment, and qualitative and quantitative analyses of cypermethrin, permethrin and propiconazole by gas liquid chromatography coupled to mass spectroscopy showed enhanced penetration of the active agents, and revealed differences of penetration performance of each agent. The suitable combinations of solvents and surfactants used in the bio-based formulations enabled rapid wood penetration and high yields retention. The capacity of penetration and retention of our gel formulations is discussed in terms of the connectivity of the conducting cells network of the two wood species. <![CDATA[Evaluation of <em>Pleurotus ostreatus</em> basidiomes production on <em>Pinus</em> sawdust and other agricultural and forestry wastes from patagonia, Argentina]]> Abstract: The basidiomes production of two strains of Pleurotus ostreatus (one native from Patagonia, Argentina, isolated from the conifer Araucaria araucana and the other one a commercial strain) grown in different agricultural and forestry wastes was studied. The ability of the native strain generates interest to know its degradative capabilities for its use with conifer waste from the regional forest industry, which is dominated by the use of exotic Pinus species. In addition, white poplar (Populus alba), southern beech (Nothofagus pumilio), wheatgrass (Thinopyrum ponticum) and residues from beer brewing were also explored as substrates. The native strain showed better productivity of basidiomes with a biological efficiency of 17,86 % ± 3,74 % on pine wood shavings in comparison with the commercial strain used as control. The best substrates were poplar and wheatgrass with biological efficiency between 35,28 % to 88,5 % and 27,84 % to 84,01 %, respectively. Supplemented substrates showed better productivity than those without supplement. The low biological efficiency on pine could be attributed to the aromatic compounds contents because, in growth test, the diameter of the fungal colony was affected negatively by the addition of pine resin volatiles, mainly with α-limonene and δ-3-carene. In spite of the low biological efficiency, promising inter-breeding or hybrids generation could improve yields in future assays. <![CDATA[Determination of the physical and mechanical properties of wood-cement boards produced with <em>Pinus</em> spp and pozzolans waste]]> Abstract: The objective of this research was to evaluate the physical-mechanical properties of wood-cement boards produced with waste particles of Pinus spp. and sufficient levels of pozzolans to assimilate all Ca(OH)2 produced during the hydration reactions of Portland cement. The pozzolans used were: silica fume, metakaolin, rice husk ash, and calcined ceramic waste. The values of the pozzolans were determined based on the theoretical determination of the Ca(OH)2 content produced by the hydration reactions of Portland cement. The pozzolanic activity index was determined by the modified Chapelle test. The boards were produced through cold compression, and the test specimens were produced and tested for physical and mechanical properties at 28/91 days of curing. The minimum values employed in the Bison® commercial process were used as a reference for the physical-mechanical characterization. The boards produced presented good physical-mechanical properties even with high levels of replacement of cement by pozzolans. These properties were similar to the ones presented by the reference boards, despite the significant reduction in the specific mass of the prototype boards, which demonstrates the technological possibility of the use of these materials in the production of wood-cement boards. <![CDATA[Economic profitability of particleboards production with a diversified raw material structure]]> Abstract: To achieve sustainable development, coherence of three key elements is necessary: economic growth, social inclusion and environmental protection. They are interconnected and all are extremely important for achieving the well-being of individuals and entire societies. One of the key drivers of sustainable economic growth is the furniture industry, which is related to the maximum optimization of production cost while maintaining the high quality of the offered products. However, the expected material deficit may contribute to a significant weakening of growth dynamics. One of the possible solutions to this problem is harvesting timber from plantations of fast-growing trees that could supplement the increasing deficit of wood raw material. The research aimed to determine the cost-effectiveness of particleboard technology modification involving the change in the structure of raw material by introducing wood from fast-growing tree plantations. The research included an estimation of the unit cost of 1 m3 particleboard manufactured in the series production process. The analysis was carried out on the example of one of the leading particleboard suppliers for the Polish furniture industry and consisted in comparing the cost of production of particleboards based on wood from fast-growing tree plantations with the cost of particleboards, which are commonly available on the market. Three variants of the diversified raw material structure were taken into account: 100 % share (1), 50 % share (2) and 25 % share (3) of raw material from fast-growing tree plantations. The time range of the studies was adopted for the years 2014-2020. The research indicates that the introduction of wood from fast-growing tree plantations into the production of particleboards enables the production of material and energy cost savings at the level of 6 % (3rd variant) to even 17 % (1st variant). Variant 1 of material structure can lead to cost reduction at the level of US$ 13,0 million (in case of particleboards production capacity 570000 m3). <![CDATA[Effect of expanded polystyrene content and press temperature on the properties of low-density wood particleboard]]> Abstract: In this study, three-layer low-density (about 400 kg/m3) particleboards consisting of a mixture of wood particles and expanded polystyrene (EPS) were manufactured. EPS bead was incorporated in the core layer as a light filler. The influence of EPS content (0 %, 2,5 %, 5 %, 7,5 %, 10 %, and 12,5 %) and press temperature (110 °C and 140 °C) on the microstructure, density profile, bending properties, internal bond and thickness swelling of the panels were investigated. Results showed that incorporation of EPS beads filled in the voids between wood particles improved the core layer integrity, and generated a more pronounced density profile. Consequently, the bending properties and internal bond of panels adding EPS were remarkably improved, and the thickness swelling was decreased. However, the variation of the number of EPS from 2,5 % to 12,5 % had no significant effect on the bending properties and thickness swelling. Comparing the two press temperatures, higher temperature (140 °C) was more favourable in control panels without EPS as filler. For panels adding EPS filler, 140 °C had a negative effect on the properties of panels, especially at high EPS contents (10% and 12,5%), attributing to the shrinkage of EPS bead under press temperature that is much higher than its glass transition temperature (104 °C). <![CDATA[Relación entre la velocidad de la onda acústica y distintas características de la madera, en árboles de <em>Eucalyptus nitens</em> con dimensiones aserrables]]> Abstract: In this study, the relationships of acoustic wave velocity measured on the standing trees (VÁRBOL) and logs (VTROZA) to different wood characteristics of Eucalyptus nitens trees of 18-year-old, grown at the Biobío region Chile, with sawing dimensions were investigated. Nine trees were randomly selected. In each selected tree the VÁRBOL at North, South, East, and West of cardinal exposition of the stem was measured. VTROZA in the middle of logs taken at a fixed height of 2 m and 33 %, 66 %, and 100 % of the tree merchantable height was measured. In each log green moisture content (CHv), green density (Dv), basic density (DB), dynamic modulus of elasticity (MOEd), growth stress indicator (GSI), modulus of elasticity in tension (Et), and longitudinal growth stress (σL) were obtained. There were no significant correlations among VÁRBOL and different characteristics examined in wood (CHv, Dv, DB, GSI, Et y σL). Acoustic wave velocity of log (VTROZA) changed significantly with the log position in the tree, increasing with tree height. VTROZA was significantly correlated to different parameters of wood quality and this variable could be used to segregate logs with a higher modulus of elasticity in tension (Et), lower green moisture content (CHv), and lower green density (Dv).<hr/>Resumen: En el presente estudio se investigaron las relaciones entre la velocidad de la onda acústica obtenida en árboles en pie (VÁRBOL), y la obtenida en trozas (VTROZA), con distintas características de la madera, en árboles de Eucalyptus nitens con dimensiones aserrables, provenientes de una plantación de 18 años de edad, crecida en la región del Biobío, Chile. Se seleccionaron 9 árboles aleatoriamente. En cada árbol seleccionado se determinó la VÁRBOL en las exposiciones cardinales Norte, Sur, Este y Oeste del fuste. La VTROZA se midió en trozas de 2,4 m de largo, centradas en longitud; a la altura fija de 2 m y al 33 %, 66 % y 100 % de la altura comercial del árbol. Para cada troza se obtuvo el contenido de humedad verde (CHv), la densidad verde (Dv), la densidad básica (DB), el módulo de elasticidad dinámico (MOEd), el indicador de la tensión de crecimiento (GSI), el módulo de elasticidad en tensión (Et) y las tensiones de crecimiento longitudinales (σL). No hubo correlaciones significativas entre la VÁRBOL y las distintas características examinadas en la madera (CHv, Dv, DB, GSI, Et y σL). La velocidad de la onda acústica en trozas (VTROZA), cambió significativamente con la posición de la troza en el fuste, aumentando en dirección base - ápice. La VTROZA se correlacionó significativamente con distintos parámetros de calidad de la madera; ésta variable podría ser utilizada para clasificar trozas con un mayor módulo de elasticidad en tensión (Et), un menor contenido de humedad verde (CHv), y una menor densidad verde (Dv). <![CDATA[Effect of the thermal modification and nano-ZnO impregnation on the deterioration of Caribbean pine wood]]> Abstract: This study aimed to investigate the effect of thermal modification and nano-zinc oxide (nano-ZnO) particle impregnation on the deterioration of Caribbean pine wood under field conditions. Samples were thermally-modified at various temperature levels (control, 180 °C, 200 °C, and 220 °C). Nano-ZnO impregnation was done with an aqueous solution at 1,5 % in an autoclave under two-steps of pressure and vacuum. Unmodified and thermally-modified, non-impregnated and nano-ZnO impregnated samples were exposed to deterioration for five months in field tests. A deterioration index was used to evaluate the health condition of the samples. The mass loss and occurrence of termite tunnels in percentage were also determined. The nano-ZnO impregnation improved the resistance of unmodified wood to field-deterioration. The thermal modification at 180oC, and 200ºC increased the wood deterioration and nano-ZnO impregnation did not improve their resistance. Unmodified and 220 ºC modified samples had a lower mass loss by xylophages than other thermal treatments regardless of the nanoparticle impregnation. The nano-ZnO impregnation decreases the occurrence of termite tunnels in unmodified, 200 ºC and 220 ºC-modified samples.