The Use of Mercury Intrusion Porosimetry to the Characterization of Eucalyptus Wood, Pulp Andpaper

Mercury intrusion is frequently used for the characterization of porous materials, giving assess to parameters such as porosity and pore size distribution as well as density (skeletal and bulk). In the pulp and paper technology field, measurements of wood porosity are important, for instance to anticipate the liquor impregnation ability in the pulping stage. With regard to pulp and paper, porosity data also contribute to study the fibre network structure, enabling a better understanding of the influence of the process conditions on this structure. The present work aims at studying the suitability of the mercury intrusion technique to evaluate the pore structure of wood (Eucalyptus globulus) and also of pulp handsheets and commercial paper sheets. From the intrusion curves of the wood samples, it was possible to identify the pores corresponding to the vessels and to the fibre lumens. In the beaten pulp sheets as well as in the commercial papers, a consistent bimodal distribution of pores was obtained corresponding to two ranges of porosity: the internal porosity, with pores from 0.1 to 10 m, and the surface porosity, that includes pores in the range 10 −100 m. Changes in fibrous raw materials and in process conditions could be easily detected by differences in these porosities. Additional measurements by gas pycnometry, used to determine the true density of the samples, revealed the existence of a small quantity of pores inferior to 0.007 m that are not accounted for by the porosimeter utilized.