Surface chemistry of eucalyptus wood pulp fibres:: Effects of chemical pulping

The surface chemistry of Eucalyptus grandis wood pulp fibres was investigated using the sessile drop apparent contact angle, XPS and TOF-SIMS techniques. Pulp fibres were studied using different chemical pulping conditions. The pulping affected the surface coverage of lignin and extractives, as indicated by XPS, and the work of adhesion with water, as estimated from contact angle determinations. The amount of surface lignin decreased while surface extractives and work of adhesion with water increased in relation to the amount of active alkali used in the pulping. Desorption and analysis of surface extractives by TOF-SIMS showed sterols, fatty acid calcium and sodium salts. After acetone extraction the spectra obtained by TOF-SIMS showed changes. However, calcium and sodium salts of fatty acids were still detected, indicating their resistance to solvent extraction. This resistance to extraction can affect the lignin and extractive surface coverage estimations using XPS due to the contribution of the carbon content after extraction. The extent of interference was, however, uncertain.