991 resultados para Eucalyptus wood


Relevância:

30.00% 30.00%

Publicador:

Resumo:

Native Mediterranean forests in Australia are dominated by two tree genera, Eucalyptus and Acacia, while Pinus and Eucalyptus dominate plantation forestry. In native forests, there is a high diversity of phloem and wood borers across several families in the Coleoptera and Lepidoptera. In the Coleoptera, cerambycid beetles (Cerambycidae), jewel beetles (Buprestidae), bark, ambrosia and pinhole beetles (Curculionidae) and pinworms (Lymexelidae) are some of the most commonly found beetles attacking eucalypts and acacias. In the Lepidoptera, wood moths (Cossidae), ghost moths (Hepialidae) and borers in the Xyloryctidae (subfamily Xyloryctinae) are most common. In contrast to native forests, there is a much more limited range of native insects present in Australian plantations, particularly in exotic Pinus spp. plantations, although eucalypt plantations do share some borers in common with native forests. This chapter reviews the importance of these borers in Australian forests primarily from an economic perspective (i.e. those species that cause damage to commercial tree species) and highlights a paucity of native forest species that commonly kill trees relative to the large scales regularly seen in North America and Europe.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

The objective of the present work is to evaluate the effects of the surface properties of unrefined eucalyptus pulp fibres concerning their performance in cement-based composites. The influence of the fibre surface on the microstructure of fibre-cement composites was evaluated after accelerated ageing cycles, which simulate natural weathering. The surface of unbleached pulp is a thin layer that is rich in cellulose, lignin, hemicelluloses, and extractives. Such a layer acts as a physical and chemical barrier to the penetration of low molecular components of cement. The unbleached fibres are less hydrophilic than the bleached ones. Bleaching removes the amorphous lignin and extractives from the surface and renders it more permeable to liquids. Atomic force microscopy (AFM) helps in understanding the fibre-cement interface. Bleaching improved the fibre- cement interfacial bonding, whereas fibres in the unbleached pulp were less susceptible to the re-precipitation of cement hydration products into the fibre cavities (lumens). Therefore, unbleached fibres can improve the long-term performance of the fibre-cement composite owing to their delayed mineralization.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

Kraft pulp is currently bleached largely by the elemental chlorine free (ECF) technology with oxygen, chlorine dioxide, and hydrogen as active agents. This technology brought about significant environmental improvements in relation to standard processes based on chlorine gas and hypochlorite, but there is still need for further improvements. This study presents a novel environmentally friendly bleaching stage - the so-called `hydrogen peroxide in supercritical carbon dioxide`, P((SC-CO2)) - that can be adapted to current ECF bleaching processes, with preference in cases where hydrogen peroxide is already used. In this study, the P((SC-CO2)) stage was evaluated as a replacement to the last peroxide stage of the D(EP)DP bleaching sequence and to the first peroxide stage of the D(EP)DP sequence, for an oxygen delignified eucalypt kraft-O(2) pulp. The P((SC-CO2)) stage was run with 0.5% hydrogen peroxide, at 15% consistency, 70 degrees C, and 73 bar. The reaction time was 30 min. The performances of regular P stages and the new P((SC-CO2)) stage were compared. Promising results were observed with the DEP((SC-CO2))DP sequence; the P((SC-CO2)) decreased kappa number from 2.7 to 2.1, and the hexenuronic acid groups from 17.0 to 12.4 mmol kg(-1). The P((SC-CO2)) stage showed poor performance when applied in the D(EP)DP((SC-CO2)) sequence. It is concluded that the process presents potential but requires further optimization to improve selectivity and efficiency.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

A caracterização anatômica, física, mecânica e química da madeira fornece informações importantes para sua melhor utilização. Contudo, para que madeiras se tornem boa opção para o mercado de pisos, adicionalmente é necessária a realização de ensaios que simulem suas reais condições em serviço. Esses ensaios simulam o pisoteio executado pelos sapatos de salto com pequenas áreas de pressão, o arraste e a queda de objetos, a resistência à abrasão da superfície e o atrito oferecido durante o deslocamento de pessoas que caminham sobre ele. Grande dificuldade da seleção de novas madeiras para pisos está na ausência de valores de referência físico-mecânicos. O presente trabalho visou a caracterizar as madeiras de Eucalyptus clöeziana F. Muell, de Eucalyptus microcorys F. Muell e de Corymbia maculata Hook, para as propriedades de densidade básica, retratibilidade, aplicação de carga rolante, de atrito estático e dinâmico, endentação causada por cargas aplicadas em pequenas áreas, impacto da esfera de aço cadente e resistência à abrasão. Foi observado que as madeiras estudadas podem ser utilizadas para a confecção de pisos, de acordo com seus resultados obtidos e por meio de comparações com resultados de literatura.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

O Eucalyptus grandis é uma das espécies mais cultivadas no Brasil devido à sua produtividade e qualidade da madeira. Avaliaram-se o efeito da aplicação de lodo de esgoto tratado (0 a 40 t ha-1 base seca) e uma dose de adubo mineral nos atributos físicos e químicos da madeira de Eucalyptus grandis de árvores com cinco anos de idade, no Município de Itatinga, São Paulo, Brasil. O tipo de solo foi caracterizado como Latossolo Vermelho-Amarelo Distrófico (argila = 120 g kg-1 na camada de 0-20 cm) e o clima, como mesotérmico úmido (Cwa), segundo a classificação de Köeppen. O delineamento experimental foi o de blocos ao acaso, com seis tratamentos e quatro repetições. O diâmetro à altura do peito (DAP), a altura das árvores e o volume de madeira foram obtidos em todas as parcelas de oito árvores com DAP na classe de maior freqüência. As caracterizações físicas e químicas da madeira foram realizadas de acordo com as normas da ABTCP, TAPPI e ABNT. O lodo de esgoto diminuiu a densidade básica da madeira, mas não afetou os teores de celulose, lignina, extrativos e o poder calorífico da madeira. O decréscimo de densidade da madeira pela adubação com lodo de esgoto foi compensado pela maior produtividade de madeira.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

Com o objetivo de avaliar a eficiência da seleção precoce em Eucalyptus spp. foram usados dados de dois testes clonais avaliados quanto ao crescimento em altura (ALT), diâmetro à altura do peito (DAP) e volume individual de madeira (VOL) aos 25, 50 e 72 meses de idade. O delineamento experimental nos dois testes clonais foi o de blocos casualizados, com trinta tratamentos (clones), seis repetições, sendo um deles com seis e o outro com dez plantas em linha por parcela, no espaçamento de 3,0 m x 3,0 m. Foi feita a análise de variância para cada caracter e idade. Foram obtidas as estimativas de coeficiente de determinação genotípico e de correlações genotípicas entre os caracteres nas idades juvenis e na idade de rotação. Para verificar a viabilidade da aplicação da seleção precoce, foi simulada a seleção de 30% dos clones nas idades juvenis e na idade de rotação para cada um dos caracteres e idades avaliadas, obtendo-se as estimativas de ganhos genéticos com a seleção direta e indireta. Houve diferenças significativas entre os clones avaliados nos dois experimentos para todos os caracteres e idades. Com base nos resultados obtidos, é possível efetuar a seleção precoce aos 2 anos de idade sobre o caracter DAP em testes clonais de eucalipto.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

The study analyzed the wood basic density effect in two Eucalyptus grandis x Eucalyptus urophylla hybrid clones (440 kg/m(3) e 508 kg/m(3)) on bleached pulp quality (fiber dimensions and physical-mechanical properties). The woods performance on pulping, bleaching and beating results were analyzed. The Kraft pulping was carried out in forced circulation digester in order to obtain 17 +/- 1 kappa number targets. The pulps were bleached to 90 +/- 1 using delignification oxygen and D0EOPD1 bleaching sequence. Bleached pulp of low basic density clone showed, significantly, lowest revolutions number in the PFI mill to reach tensile index of 70 N.m/g, low Schopper Riegler degree and generated sheets with higher values to bulk and opacity. These characteristics and properties allow concluding that bleached pulp of low basic density clone was the most indicated to produce printing and writing sheets. The bleached pulp of high basic density clone showed higher values of bulk and capillarity Klemm and lower water retention value when analyzed without beating. The bleached pulp of high basic density clone showed more favorable characteristics to the production of tissue papers.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

The juvenile wood presents great difference in its anatomical and physical properties in relation to the mature wood. That heterogeneity of the wood causes a series of upset for the processing industry. The present research had as objective the study of the physical properties of the juvenile and mature wood of Pinus elliottii Engelm var. elliottii, with 25 years of age and of Eucalyptus grandis Hill ex Maiden, with 30 years of age, coming from the Experimental Station of Itapetininga and State Forest of Santa Barbara, belonging to the Forest Institute of the state of São Paulo. From both species there were taken from radial boards, specimens with dimensions of 20x30x50 mm, for the determination of density, swelling and swelling coefficient of the juvenile and mature wood. The results of the species showed that the mature compared with the juvenile wood presented: (1) an increase in the values of the basic density, at 0% and at 12% of moisture content and of the volumetric, radial and tangential swelling at 12% moisture content and maximum coefficient of radial and tangential swelling; (2) a reduction in the values of longitudinal swelling at 12% and maximum and of the longitudinal swelling coefficient.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

This study aimed to evaluate the adhesion ability of eucalyptus lumber from three tillage systems, using adhesives: resorcinol formaldehyde and two adhesives in water emulsion based on vinyl poly-acetate. The management systems were characterized by three strata, the stratum one (E1) characterized by wood from coppice and 70 months of age, the stratum two (E2) characterized by wood and retirement age of 166 months and stratum three (E3), also characterized by retirement at 70 months of age. The wood was derived from a random mixture of the first two sawn logs, each three feet from the base, which comprised three treatments on the adhesive used. We evaluated the shear strength by compression tests and the percentage of wood failure in the glue line. Based on the results obtained, it can be said that the adhesion had satisfactory performance with all the resins used, and the average values of shear strength of the glue line were shown to be equivalent to the shear strength of solid wood only for the samples which adhered with 'Wonderbond' adhesive and also provide higher values for wood failure (97.64%). The highest density present in the wood of the second stratum (E2) influenced only sticking with the resorcinol formaldehyde resin. For polyvinyl acetate (Cascorez 2590), shear values decreased in the third management condition (E3).

Relevância:

30.00% 30.00%

Publicador:

Resumo:

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Relevância:

30.00% 30.00%

Publicador:

Resumo:

This paper mainly aimed to evaluate the physical and mechanical properties of LVL panels made from Eucalyptus grandis, from reforestation at the region of Senges, in Parana state, Brazil. LVL panels were manufactured using 23 veneers (2,4mm thick each one) in commercial dimension of 2.500 mm long and 1,200 mm wide. The properties of static bending were analyzed (strength and rigidity) in beams of the LVL, in the flatwise and edgewise positions. The properties of compression parallel to grain and shear parallel in the plans L-X and L-Y and density in this LVL panels were also analyzed according to ASTM-D 5456/4761 and ASTM-D 198 codes. The mean values to flatwise bending MOE and MOR were 13114 MPa and 88.76 MPa, respectively, and for edgewise bending MOE and MOR were 15871 MPa and 88.63 MPa, respectively. The density (12%) of the LVL panels and of the veneers were 690 kg/m(3) and 649 kg/m(3). The mean values to parallel compression MOE and MOR were 16856 MPa and 58.05 MPa, respectively. The mean values of the maximum resistance to shear parallel in the plans L-X and L-Y were 5.96 MPa and 591 MPa, respectively. All these values reached partially or they passed the medium limits of reference (normative codes, researches and commercial catalogs) established for LVL panels and original solid wood, attesting overall the quality of those panels produced with this wood.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Relevância:

30.00% 30.00%

Publicador:

Resumo:

Some Eucalyptus species are widely used as a plantation crop in tropical and subtropical regions. One reason for this is the diversity of end uses, but the main reason is the high level of wood production obtained from commercial plantings. With the advancement of biotechnology it will be possible to expand the geographical area in which eucalypts can be used as commercial plantation crops, especially in regions with current climatic restrictions. Despite the popularity of eucalypts and their increasing range, questions still exist, in both traditional planting areas and in the new regions: Can eucalypts invade areas of native vegetation, causing damage to natural ecosystems biodiversity?The objective of this study it was to assess whether eucalypts can invade native vegetation fragments in proximity to commercial stands, and what factors promote this invasive growth. Thus, three experiments were established in forest fragments located in three different regions of Brazil. Each experiment was composed of 40 plots (1 m(2) each one), 20 plots located at the border between the forest fragment and eucalypts plantation, and 20 plots in the interior of the forest fragments. In each experimental site, the plots were paired by two soil exposure conditions, 10 plots in natural conditions and 10 plots with soil exposure (no plant and no litter). During the rainy season, 2 g of eucalypts seeds were sown in each plot, including Eucalyptus grandis or a hybrid of E. urophylla x E. grandis, the most common commercial eucalypt species planted in the three region. At 15, 30, 45, 90, 180, 270 and 360 days after sowing, we assessed the number of seedlings of eucalypts and the number of seedlings of native species resulting from natural regeneration. Fifteen days after sowing, the greatest number of eucalypts seedlings (37 m(-2)) was observed in the plots with lower luminosity and exposed soil. Also, for native species, it was observed that exposed soil improved natural germination reaching the highest number of 163 seedlings per square meter. Site and soil exposure were the factors that have the greatest influence on seed germination of both eucalypt and native species. However, 270 days after sowing, eucalypt seedlings were not observed at any of the three experimental sites. The result shows the inability of eucalypts to adapt to condition outside of their natural range. However, native species demonstrated their strong capacity for natural regeneration in forest fragments under the same conditions where eucalypts were seeded. (C) 2011 Elsevier B.V. All rights reserved.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

Lepidopteran pests have occurred in eucalyptus plantations in Brazil since 1948, reaching high population levels, reducing tree growth and causing considerable losses in wood production. The control of defoliating caterpillars in eucalyptus forests is complex, mainly due to the large extent of forest plantations and tree height, necessitating the aerial application of chemical or biological insecticides. Due to this complexity, alternative control methods have been proposed, for instance biological control through the use of parasitoids. Trichospilus diatraeae Cherian & Margabandhu, 1942 is a gregarious pupal parasitoid that preferentially attacks species of the order Lepidoptera. This is the first report of T. diatraeae parasitizing pupae of the eucalyptus defoliator Euselasia eucerus Hewitson in Brazil. This parasitoid offers new perspectives for the biological control programmes of this species in eucalyptus plantations in Brazil.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)