Paulo Ricardo Gherardi Hein

MICRO/NANOFIBRILAS CELULÓSICAS DE EUCALYPTUS EM FIBROCIMENTOS EXTRUDADOS

Uma forma alternativa para producao de fibrocimento e a extrusao, que permite entre muitas vantagens a producao de compositos cimenticios com geometrias diferenciadas e requer baixo investimento inicial para producao industrial. Nesse contexto,o objetivo desse trabalho foi obter micro/nanofibrilas celulosicas de Eucalyptus e avaliar o efeito da adicao de diferentes conteudos dessas micro/nanofibrilas nas propriedades fisico-mecânicas de fibrocimentos envelhecidos naturalmente e em ambiente climatizado. Micro/nanofibrilas celulosicas produzidas em desfibrilador mecânico foram caracterizadas quanto a sua morfologia. Compositos extrudados produzidos com 0,5% e 1,0% (em massa) de micro/nanofibrilas foram comparados com compositos sem micro/nanofibrilas. Compositos produzidos a partir das tres formulacoes foram submetidos aoenvelhecimento natural e em ambiente controlado para posterior caracterizacao por flexao estatica, vibracao flexural e propriedades fisicas. Nao houve diferenca significativa no modulo de ruptura (MOE), limite de proporcionalidade (LOP), e deformacao especifica total entre os compositos com reforco de 0,5 e 1,0% de micro/nanofibrilas e aqueles sem reforco. O modulo elastico estatico (MOE) aumentou, e a energia especifica diminuiu com 1,0% de micro/nanofibrilas. O modulo de elasticidade dinâmico (E) dos compositos aumentou com o incremento do conteudo de micro/nanofibrilas (1,0%) e do tempo de exposicao ao envelhecimento natural e controlado. O presente estudo indica que as propriedades fisicas (absorcao de agua - AA, porosidade aparente - PA e densidade aparente - DA) e mecânicas de fibrocimentos sao sensiveis a formulacao e que esse comportamento varia em funcao do tempo (135 dias). Essas informacoes devem ser consideradas uteis para o desenvolvimento de novos materiais reforcados com micro/nanofibrilas de celulose.

Relationships between microfibril angle, modulus of elasticity and compressive strength in Eucalyptus wood

Many traits are known to be important in determining the value of Eucalyptus wood as sawn timber. The commercial importance of the microfi bril angle (MFA) for wood quality is well established for a range of softwoods, but is less clear for hardwood species. For instance, the relationships of MFA with wood stiffness and compressive strength are unknown in Eucalyptus. Therefore, the aim of this study was to evaluate the correlation between MFA and the modulus of elasticity (E c0,m ) in compression parallel to grain and compressive strength (F c0,k ) using juvenile wood of Eucalyptus grandis from fast-growing plantations. The correlation between wood stiffness and compressive strength was high (0.91). The cellulose microfi bril angle presented a correlation of -0.67 with wood stiffness and of -0.52 with compressive strength in Eucalyptus juvenile wood. MFA was found to be important in determining the mechanical behaviour of wood and appears to be a useful parameter to indicate wood stiffness and strength in juvenile Eucalyptus from short-rotation plantations.

Correlations among microfibril angle, density, modulus of elasticity, modulus of rupture and shrinkage in 6-year-old "Eucalyptus urophylla × E. grandis"

The cellulose microfibril angle (MFA) in the cell wall is known to have major effects on wood stiffness and shrinkage. However, its influence on juvenile wood traits is not fully understood, especially in Eucalyptus. The aim of this study was to evaluate the relationships among MFA, density (ρ), dynamic modulus of elasticity (E), modulus of rupture (MOR), and shrinkage (δ) in 6-year-old Eucalyptus urophylla × E. grandis. Small clear specimens (L 410 mm x R 25 mm x T 25 mm) were cut from central boards for the determination of E and MOR. Cubic samples (25 mm³) were removed after the dynamic and static tests to evaluate ρ and δ. MFA was finally measured by X-ray diffraction on small strips coming from the cubic samples. A quasi-absence of statistical link was found for MFA - δ and MFA - ρ (R²<0.20). The parameter ρ/MFA was used to estimate E (R²=0.66) and MOR (R²=0.37). In a next step, the additive and interaction effects were investigated using multiple linear regressions with a forward selection method. The property E was found to be linked only with the additive effects of ρ and 1/MFA (R²=0.76). The additive and interaction effects were all significant for MOR (R²=0.54). This study showed that a general model including both additive and interaction effects should be used for the prediction of the modulus of elasticity and the modulus of rupture.

Near infrared spectroscopy for estimating Eucalyptus charcoal properties

Steel can be produced from vegetable charcoal used as a thermo reducer in steel blast furnaces. Hence, the metallurgical industry requires new solutions for controlling the quality of their charcoal in order to maintain the same quality standard. The objective of this study was to assess the properties of charcoal by near infrared spectroscopy. Partial least square (PLS) regressions were established for estimating fixed-carbon, volatile matter content and gravimetric yield of charcoal. These models were validated by cross-validations and independent test sets and presented similar performance. PLS-R models obtained from untreated NIR spectra for FCC and VMC yielded promissory statistics [r2p of ∼0.9; root mean squared error of prediction (RMSEP) of ∼3.3%; and ratio of the standard error of prediction to standard deviation (RPD)>3] while the statistics of the calibrations for gravimetric yield had relatively lower magnitude (R2p of ∼0.8, a RMSEP of ∼2.2 and RPD<2). Since new solutions are required for controlling the quality of charcoal with speed and precision, these models can be useful for monitoring charcoal quality in steel industries.

Estimating Shrinkage, Microfibril Angle and Density of Eucalyptus Wood Using near Infrared Spectroscopy

Developing calibration models from near infrared (NIR) spectra for quickly and reasonably estimating key wood traits has become a prime step in tree breeding programmes. While the optimal procedures for the calibration of NIR-based models for chemical-related wood traits, stiffness and wood density of wood are relatively well established, relatively few studies have dealt with NIR calibrations for wood shrinkage and cellulose microfibril angle (MFA) of cell walls. MFA has major effects on wood stiffness and shrinkage; however, this ultra-structural cell wall feature has been under-utilised by breeding programmes due to the difficulty in measuring it. The aim of this study was to develop NIR models for estimating radial and tangential shrinkage and MFA in Eucalyptus wood. The calibration for MFA provided NIR predicted values suitable for making a selection of the most favourable trees for a given end-use in breeding programmes. The correlation (r2p) between NIR predicted and X-ray diffraction derived values of MFA was 0.75 and the root mean standard error of the predictions was 1.3 degrees. These estimates appear to be adequate for selecting potential trees in genetic investigations. Calibrations were also established for predicting the dimensional stability of the wood. However, the statistics for shrinkage indicated that the models were not satisfactory as they provided NIR estimated values of limited applicability. Further studies would be useful for establishing adequate protocols for NIR calibrations of these important (but complicated to measure) wood characteristics.

Estimation of the dynamic elastic properties of wood from Copaifera langsdorffii Desf using resonance analysis

Analysis of transverse vibrations has been identified as a simple, inexpensive, fast and effective method of characterizing the elastic properties of several materials, including wood. The objective of this study is to evaluate the dynamic elastic properties of wood from Copaifera langsdorffii through resonance analysis. A linear correlation was observed, with a coefficient of determination of 0.88, between the dynamic modulus of elasticity (Ed), as determined by BING (resonance analysis), and the static modulus of elasticity (E), as determined by a universal testing machine, for wood samples of Copaifera langsdorffii. A moderate correlation was observed (0.69) between the Ed and the apparent density (D) of the samples. The shear modulus (G) was negatively correlated with D, E, and Ed, yet not significantly. The specific modulus, which is the stiffness to density ratio, was linearly correlated with the internal damping. This viscoelastic correlation is rarely reported in literature and indicates, for instance, wood quality for the manufacture of musical instruments. The BING system provided fast, reliable results for estimation of elastic properties, particularly stiffness, in wood of Copaifera langsdorffii.

Spatial variation of wood density, stiffness and microfibril angle along Eucalyptus trunks grown under contrasting growth conditions

Key messageSloped terrains tend to produce trees with higher radial variation in wood density while at high wind speeds, the wood tends to present higher stiffness and lower MFA inEucalyptus.AbstractFew studies have investigated the influence of environmental conditions on the within-tree variation in Eucalyptus wood traits. The genotype and environment effects and their interactions influence the wood properties. Their evaluations are crucial to estimate the genotype values and to select with efficiency. Thus, the aim of this study was to better understand the effect of ground slope and wind speed on the spatial variation of basic density (ρ), stiffness (MOE) and microfibril angle (MFA) of Eucalyptus wood. Wood discs cut along the trunk were sampled from one-hundred fifty 6-year-old Eucalyptus grandisxa0×xa0E. urophylla hybrids growing in three contrasting growing conditions influenced by ground slope and wind regime. Near infrared (NIR) calibrations previously developed for ρ, MOE and MFA were used to predict in our discs. 2-D plots presenting the spatial variation of predicted wood traits were compared. The higher the ground slope, the greater the magnitude of radial variation in ρ, principally in the medium zone of the trunk. The spatial variation of wood stiffness seems to be sensitive to two environmental conditions. The MFA radial decreases were more pronounced where the wind speed was higher. At the base and top of the trees, however, there was no significant effect of growing conditions on the radial variation of the wood properties considered here.

NIR Spectral Heritability: A Promising Tool for Wood Breeders?

NIR spectroscopy has been widely used in tree-breeding programmes for selection because it is able to characterize large wood samplings rapidly and at relatively low cost. NIR spectra were recorded on various radial and longitudinal positions on the wood of 150 Eucalyptus trees. Each NIR spectrum used for analysis consisted of 280 absorption values following data reduction. The ratio between the genetic variance and phenotypic variance of the NIR absorbance values was calculated for each wavenumber producing the broad-sense NIR spectral heritability estimates. The variations in NIR spectra are thought to be related to variation in lignin and cellulose and hemicelluloses contents. The findings suggest that the variations of some specific ranges of the NIR spectra are controlled by genetic factors. Some ranges of the NIR spectra showed heritabilities greater than 50%. Thus, these variations in NIR spectra are thought to be related to variation in lignin, cellulose and hemicelluloses contents. The indirect estimates of broad-sense heritabilities from NIR spectra recorded on wood appear to be an efficient and promising way to evaluate the genetic control for many wood traits simultaneously.

Essential oil content in Eremanthus erythropappus wood powder can be estimated using near infrared spectroscopy

Candeia [Eremanthus erythropappus (DC.) MacLeish], a Brazilian tree species, is being threatened by indiscriminate logging because the essential oil present in its wood has economic importance. The aim of this study was to develop a near infrared spectroscopic model for estimating the essential oil content in E. erythropappus wood to select trees with a high amount of essential oil before harvesting them. Essential oil from 103 wood powders was extracted via hydrodistillation. The values were calculated as the ratio between the mass of essential oil extracted and the oven dry mass of wood, and correlated to the NIR spectra recorded from the wood powders. Statistics associated with the predictive models have demonstrated that NIR has the potential to be a fast and feasible method to replace standard procedures for selecting trees with a high essential oil content. The NIR-based predictions in an independent validation set yielded a high correlation (r = 0.89) with the laboratory-determined values for essential oil content in E. erythropappus wood. This NIR model can be applied to guide wood managers for selecting high-oil-content trees before harvesting them and for developing sustainable strategies for industrial utilisation of Candeia populations.

INFLUÊNCIA DO DIÂMETRO E UMIDADE NO TRATAMENTO PRESERVATIVO DE MOIRÕES DE Eucalyptus

The aim of this study was to assess the effects of diameter class, general moisture and sapwood moisture over the retention of CCA-C (Chromated Copper Arsenate type C) on a Eucalyptus urophylla clone wood preserved in autoclave. 36 fence posts were used, belonging to the diameter classes of 7, 9, 11 and 13 cm, which were separated and exposed to three outdoor drying times: 20, 40 and 70 days. The pre-treatment moisture values, general and only sapwood, were determined by diameter class and drying times. After the preservation in autoclave, the treatment quality control was made by analyzing the CCA-C retention. Retention in fence posts of the 7 cm class was higher than those of 9, 11 and 13 cm classes, which did not vary statistically amongst each other. The increase in drying time from 20 to 40 days resulted in significant increase in average retention from 5.70 to 6.67 kg A.I.*m -3 . The mean variations of the general moisture and the sapwood were significant with variation of retention, showing good correlation between the factors. The correlation between the fence posts general moisture and retention of CCA-C (r = -0.86) was stronger than the correlation between sapwood moisture and retention (r = -0.70).