RELATIONSHIP AMONG EXTRACTIVES, LIGNIN AND HOLOCELLULOSE CONTENTS WITH PERFORMANCE INDEX OF SEVEN WOOD SPECIES USED FOR BOWS OF STRING INSTRUMENTS

In this paper we investigate the influence of extractives, lignin and holocellulose contents on performance index (PI) of seven woods used or tested for violin bows. Woods with higher values of this index (PI = root MOE/rho, where MOE is modulus of elasticity and rho is density) have a higher bending stiffness at a given mass, which can be related to bow wood quality. Extractive content was negatively correlated with PI in Caesalpinia echinata, Hanclroanthus sp. and Astronium lecointei. In C. echinata holocellulose was positively correlated with PI. These results need to be further explored with more samples and by testing additional wood properties. Although the chemical constituents could provide an indication of quality, it is not possible to establish appropriate woods for bows solely by examining their chemical constituents.

EFEITO DA IDADE E POSIÇÃO DE AMOSTRAGEM NA DENSIDADE E CARACTERÍSTICAS ANATÔMICAS DA MADEIRA DE Eucalyptus grandis

The knowledge of the variations in the wood characteristics produced by eucalyptus trees according to age and sampling positions is essential for its proper use. This study had as objective to evaluate the influence of the age, longitudinal and radial positions on basic density and anatomical characteristics in Eucalyptus grandis wood. The trees were planted in 3x2 m spacing and fertilized with commercial fertilizers in planting, 6th and 12th months. According to basal area distribution, fifteen trees were selected (24, 36 and 72 months of age) - five trees per age. Disks at DBH position (1.3 m) were taken for fiber determination (length, wall thickness, lumen diameter and width) and vessels (tangential diameter, frequency and area occupied) and in other different sampling positions for basic density determination. Wood basic density increased from 0.43 to 0.46 g.cm(-3) as well as the trees age increases with a longitudinal variation model, characterized through a decrease in base-3m (0.42-0.49 -> 0.40-0.46 g.cm(-3)) and an increase to the top of the trunk (0.46 -> 0.54 g.cm(-3)) Fibers and vessels dimensions showed variations related to age and to pit-bark direction. Wood properties behavior and variations indicate that, until this period, the juvenile wood is being formed.

DETERMINATION OF THE E/G RATIO OF WOOD LOGS USING TRANSVERSE VIBRATION

The Bernoulli's model for vibration of beams is often used to make predictions of bending modulus of elasticity when using dynamic tests. However this model ignores the rotary inertia and shear. Such effects can be added to the solution of Bernoulli's equation by means of the correction proposed by Goens (1931) or by Timoshenko (1953). But to apply these corrections it is necessary to know the E/G ratio of the material. The objective of this paper is the determination of the E/G ratio of wood logs by adjusting the analytical solution of the Timoshenko beam model to the dynamic testing data of 20 Eucalyptus citriodora logs. The dynamic testing was performed with the logs in free-free suspension. To find the stiffness properties of the logs, the residue minimization was carried out using the Genetic Algorithm (GA). From the result analysis one can reasonably assume E/G = 20 for wood logs.

EFFECT OF THERMAL TREATMENT ON THE CHEMICAL CHARACTERISTICS OF WOOD FROM Eucalyptus grandis W. Hill ex Maiden UNDER DIFFERENT ATMOSPHERIC CONDITIONS

Thermal treatment (thermal rectification) is a process in which technological properties of wood are modified using thermal energy, the result of Which is often value-added wood. Thermally treated wood takes on similar color shades to tropical woods and offers considerable resistance to destructive microorganisms and climate action, in addition to having high dimensional stability and low hygroscopicity. Wood samples of Eucalyptus grandis were subjected to various thermal treatments, as performed in presence (140 degrees C; 160 degrees C; 180 degrees C) or in absence of oxygen (160 degrees C; 180 degrees C; 200 degrees C) inside a thermal treatment chamber, and then studied as to their chemical characteristics. Increasing the maximum treatment temperatures led to a reduction in the holocellulose content of samples as a result of the degradation and volatilization of hemicelluloses, also leading to an increase in the relative lignin content. Except for glucose, all monosaccharide levels were found to decrease in samples after the thermal treatment at a maximum temperature of 200 degrees C. The thermal treatment above 160 degrees C led to increased levels of total extractives in the wood samples, probably ascribed to the emergence of low molecular weight substances as a result of thermal degradation. Overall, it was not possible to clearly determine the effect of presence or absence of oxygen in the air during thermal treatment on the chemical characteristics of the relevant wood samples.

Employing perichromism for probing the properties of carboxymethyl cellulose films: an expedient, accurate method for the determination of the degree of substitution of the biopolymer derivative

The properties of films of carboxymethyl cellulose, CMC, of different degree of substitution, DS, have been examined by the use of perichromic indicators (probes). The film properties that have been determined are: empirical polarity, E-T(33); "acidity", alpha; "basicity", beta; and dipolarity/polarizability, pi*. This has been achieved by employing the following perichromic probes: 4-nitroaniline, 4-nitroanisole, 4-nitro-N,N-dimethylaniline, and 2,6-dichloro-4-(2,4,6-triphenyl-pyridinium-1-yl)phenolate, WB. The correlations between both E-T(33)- or pi* and DS were found to be linear; that between beta and DS is a second order polynomial; no obvious correlation was found between alpha and DS. The polarities of CMC films are in the range of those of butyl alcohols. As models for CMC, we have employed cellulose plus CMC of high DS; oxidized cellulose with degree of oxidation = 0.5; sodium glucuronate. The former model behaved akin to CMC, but the plots of the perichromic properties versus DS showed different slopes/intercepts. FTIR data and molecular dynamics simulations on the solvation of WB have shown that this difference can be traced to more efficient hydrogen bonding between the film of the model and the probe. This affects the intra-molecular charge-transfer energy of the latter, leading to different responses to the variation of DS. Based on the excellent linear correlation between E-T(33) and DS, for CMC from different origins, we suggest that perichromism is a simple, accurate, and expedient alternative for the determination of DS of the biopolymer derivative.

ANALYSIS OF THE NATURAL VIBRATION FREQUENCY TEST METHOD TO OBTAIN THE MODULUS OF ELASTICITY OF WOOD STRUCTURAL COMPONENTS

There are several techniques to characterize the elastic modulus of wood and those currently using the natural frequencies of vibration stand out as they are non-destructive techniques, producing results that can be repeated and compared over time. This study reports on the effectiveness of the testing methods based on the natural frequencies of vibration versus static bending to obtain the elastic properties of reforested structural wood components usually employed in civil construction. The following components were evaluated: 24 beams of Eucalyptus sp. with nominal dimensions (40 x 60 x 2.000 mm) and 14 beams of Pinus oocarpa with nominal dimensions (45 x 90 x 2.300 mm) both without treatment; 30 boards with nominal dimensions (40 x 240 x 2.010 mm) and 30 boards with nominal dimensions (40 x 240 x 3.050 mm), both of Pinus oocarpa and with chromate copper arsenate (CCA) preservative treatment. The results obtained in thiswork show good correlation when compared to the results obtained by the static bending mechanical method, especially when applying the natural frequency of longitudinal vibration. The use of longitudinal frequency was reliable and practical, therefore recommended for determining the modulus of elasticity of wood structural elements. It was also found that no specific support is needed for the specimens using the longitudinal frequency, as well as no previous calibrations, reducing the execution time and enabling to test many samples.

Effect of aqueous extracts from Ceriporiopsis subvermispora-biotreated wood on the decolorization of Azure B by Fenton-like reactions

Aqueous extracts from wood biotreated with the white-rot fungus Ceriporiopsis subvermispora were evaluated for their Fe3+- and Cu2+-reducing activities and their anti- or prooxidant properties in Fenton-like reactions to decolorize the recalcitrant dye Azure B. The decolorization of Azure B was strongly inhibited in the presence of 10% (v/v) wood extracts. Only 0.1% (v/v)-diluted extracts provided some enhancement of the Azure B decolorization. The iron-containing reactions decolorized more Azure B and consumed substantially more H2O2 than the reactions containing copper. This study demonstrates that water-soluble wood phenols exert anti- or prooxidant effects that depend on their concentration in the reactions and on the type of cation, Fe3+ or Cu2+, used to convert H2O2 to OH radicals. Crown Copyright (C) 2012 Published by Elsevier Ltd. All rights reserved.

Roof modular system in wood and particle board (OSB) to rural construction

Wood is a material of great applicability in construction, with advantageous properties to form various structural systems, such as walls and roof. Most of the roof structural systems follow models that have remained unchanged for a long time. A roof modular system in distinguished materials is proposed: reforested wood (Pine), oriented strand board (OSB) and roof tiles made of recycled long-life packaging material in order to be applied in rural construction. In this alternative, besides the benefit of giving destination packages with long-life thermal comfort, it also highlights the use of reforestated wood being the cultivation of such species that provides incentive for agribusiness. The structural performance of this alternative was evaluated through computer modeling and test results of two modular panels. The analysis is based on the results of vertical displacements, deformations and stresses. A positive correlation between theoretical and experimental values was observed, indicating the model's feasibility for use in roof structures. Therefore, the modular system represents a solution to new architecture conceptions to rural construction, for example, storage construction, cattle handling and poultry, with benefits provided by prefabricated building systems.

Effect of thermal treatment on the chemical characteristics of wood from Eucalyptus grandis W. Hill ex Maiden under different atmospheric conditions

Thermal treatment (thermal rectification) is a process in which technological properties of wood are modified using thermal energy, the result of which is often value-added wood. Thermally treated wood takes on similar color shades to tropical woods and offers considerable resistance to destructive microorganisms and climate action, in addition to having high dimensional stability and low hygroscopicity. Wood samples of Eucalyptus grandis were subjected to various thermal treatments, as performed in presence (140ºC; 160ºC; 180ºC) or in absence of oxygen (160ºC; 180ºC; 200ºC) inside a thermal treatment chamber, and then studied as to their chemical characteristics. Increasing the maximum treatment temperatures led to a reduction in the holocellulose content of samples as a result of the degradation and volatilization of hemicelluloses, also leading to an increase in the relative lignin content. Except for glucose, all monosaccharide levels were found to decrease in samples after the thermal treatment at a maximum temperature of 200ºC. The thermal treatment above 160ºC led to increased levels of total extractives in the wood samples, probably ascribed to the emergence of low molecular weight substances as a result of thermal degradation. Overall, it was not possible to clearly determine the effect of presence or absence of oxygen in the air during thermal treatment on the chemical characteristics of the relevant wood samples.