A total of 120 Acacia melanoxylon R. Br. (Australian blackwood) stem discs, belonging to 20 trees from four sites in Portugal, were used in this study. The samples were kraft pulped under standard identical conditions targeted to a Kappa number of 15. A Near Infrared (NIR) partial least squares regression (PLSR) model was developed for the Kappa number prediction using 75 pulp samples with a narrow Kappa number variation range of 10 to 17. Very good correlations between NIR spectra of A. melanoxylon pulps and Kappa numbers were obtained. Besides the raw spectra, also pre-processed spectra with ten methods were used for PLS analysis (cross validation with 48 samples), and a test set validation was made with 27 samples. The first derivative spectra in the wavenumber range from 6110 to 5440 cm -1 yielded the best model with a root mean square error of prediction of 0.4 units of Kappa number, a coefficient of determination of 92.1%, and two PLS components, with the ratios of performance to deviation (RPD) of 3.6 and zero outliers. The obtained NIR-PLSR model for Kappa number determination is sufficiently accurate to be used in screening programs and in quality control.

Two models were developed to evaluate total volume under and over-bark of Blackwood (Acacia melanoxylon R. Br.) stand trees. By variance analysis regarding volume with and without bark it was confirmed that trees age is responsible for 48 to 50% of its volumetric behaviour. Considered the averages of those variables and regarding the three homogeneous groups of the studied sites, a single model type was used (v=β 1

Se estudia en este trabajo el comportamiento de seis muestras de astillas de madera de Acacia melanoxylon, con densidades básicas de 449; 489; 493; 505; 514 y 616 kg/m³, en un proceso kraft de cocido y fabricación de papel. Las muestras de astillas fueron cribadas y enviadas al proceso de cocimiento kraft. Los ensayos fueron desarrollados con 1000 g. de madera seca en horno puestas en un digestor de circulación forzada. Las astillas cocidas fueron desintegradas, cribadas y lavadas. Los rendimientos cribados y totales, el número kappa y la viscosidad de la pulpa fueron determinados de acuerdo a métodos estándares.

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