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The pulping and papermaking potential of Acacia dealbata and Acacia melanoxylon were studied using Eucalyptus globulus as a reference. Pulp yield, alkali consumption and delignification in the kraft process, of both species, compare very well with the reference. Pulp yield can be higher than that of E. globulus and the residual lignin content lower after cooking, which is in good agreement with the lower lignin and extractives content of the wood samples used. Pulps produced from Acacia have slightly lower fibre length and coarseness and higher fibre width and wet fibre flexibility than E. globulus pulps. As a consequence of fibre characteristics, the paper produced from Acacia is denser and exhibits higher tensile and burst strength, and lower tear resistance than that from E. globulus, at a given PFI revolution.

This paper reports on the relationship between the fibre morphology of six Acacia melanoxylon bleached kraft pulps, produced from wood chips with basic densities of 449, 489, 493, 505, 514 and 616 kg/m3, and their papermaking potential. Six wood samples were selected in order to provide pulps with markedly different fibre morphological properties. The pulps were beaten in a PFI mill at 500, 2500 and 4500 revolutions under a refining intensity of 1.7 N/mm and their papermaking potential evaluated. The mean values of fibre length, fibre width and coarseness ranged between 0.78 and 0.99 mm, 17.8 and 19.4 cm, and 4.8 and 6.2 mg/100 m, respectively. As expected, the fibres characteristics have very high impact on handsheet structure, including smoothness, and on mechanical and optical properties, for the unbeaten pulps. At a given beating input (same PFI revolutions), the differences between pulps remain very high. Moreover, for a given paper density, tensile and tear strength, and light scattering coefficient are very sensitive to mean pulp fibre characteristics.