Maria Fernanda Vieira Rocha

Influence of spectral acquisition technique and wood anisotropy on the statistics of predictive near infrared–based models for wood density:

Wood density is an important criterion for material classification, as it is directly related to quality of wood for structural use. Several studies have shown promising results for the estimation of wood density by near infrared spectroscopy. However, the optimal conditions for spectral acquisition need to be investigated in order to develop predictive models and to understand how anisotropy and surface roughness affect the statistics of predictive partial least square regression models. The aim of this study was to evaluate how the spectral acquisition technique, wood surface, and the surface quality influence the ability of partial least square–based models to estimate wood density. Near infrared spectra were recorded using an integrating sphere and fiber-optic probe on the tangential, radial, and transverse surfaces machined by circular and band saws in 278 wood specimens of six-year-old Eucalyptus hybrids. The basic density values determined by the conventional method were then correlated with near infrared spectra acquired using an integrating sphere and fiber-optic probe on the wood surfaces by means of partial least square regressions. The most promising models for predicting wood density were generated from near infrared spectra obtained from the transverse surface machined by the bandsaw, via an integrating sphere ( r p 2 = 0 . 87 , RMSEP = 23 kg m−3 and RPD = 3.0) as well as for the optic fiber ( r p 2 = 0 . 78 , RMSEP = 35 kg m−3 and RPD = 2.1). Surface quality affected the spectral information and robustness of predictive models with a rougher surface, caused by band sawing, showing better results.

Wood Knots Influence the Modulus of Elasticity and Resistance to Compression

The objective of this study was to establish the correlation between the size of the wood knots and the modulus of elasticity (MOE) and the compressive strength (Fc) in Eucalyptus wood. 156 Eucalyptus urophylla samples with knots were separated into 3 classes (small, medium and large knots), and samples were selected from the same tree and submitted to the parallel fiber compression test for MOE and Fc determination. There was a significant difference between the MOE and Fc of the smaller knot class (Class 1) and the other classes with larger knots (Classes 2 and 3). In general, the larger the knot, the greater the difference between the MOE and Fc. Wood with small knots (8.31 mm2) presents stiffness and strength statistically equal to wood free of defects. Eucalyptus wood stiffness is more sensitive to the presence of knots than the strength when compared to clear wood samples.

The effect of reaction wood on the properties of eucalyptus kraft pulp - Part II

The fibers of Eucalyptus wood have characteristics relevant to the Brazilian pulp industry in the production of tissue papers, printing and writing papers, and more recently paper for packaging. The chemical composition and morphology of the fibers of reaction wood are distinct from normal fibers, and can influence both the pulping parameters and the paper properties. The objective of this study was to evaluate the quality of bleached Eucalyptus Kraft pulp, from reaction wood, on paper production. For that, the physicalmechanical and optical properties of bleached eucalyptus pulps produced from trees with straight stem and inclined stem, normal and reaction wood, respectively, were analyzed. The reaction pulp presented physical, mechanical and optical properties superior to the normal pulp, with the exception of tear resistance and apparent specific volume. As such, the reaction pulp obtained higher potential for paper production than the normal pulp. For sanitary purposes, the reaction pulp achieved good water absorption results and also reduced the energy consumption during refining, despite a slight decrease in the tensile and tear index. For the production of printing and writing papers, the reaction pulp had better performance in the optical mechanical resistance properties, with the exception of tear resistance. ADDRESSES OF THE AUTHORS: Walter Torezani Neto Boschetti (walterboschetti@gmail.com), Rubens Chaves de Oliveira (rchaves@ufv.br), and Ana Márcia Macedo Ladeira Carvalho (ana.marcia@ufv.br), Federal University of Viçosa, Department of Forest Engineering, Viçosa, Brasil; Maria Fernanda Vieira Rocha (mfvrocha@yahoo.com.br), Federal University of Lavras, Department of Forestry Sciences, Lavras, Brasil. Corresponding author: Walter Torezani N. Boschetti