The effects of kraft pulping on the interfacial properties of eucalypt pulp fibres were investigated using polyelectrolyte titration (PT) and contact angle measurements. Changes on surface composition were assessed by FTIR-ATR spectrometry combined with principal component analysis (PCA). Surface lignin was removed by increase in active alkali in pulping as indicated by FTIR-ATR and PCA. In parallel, the surface charge decreased while the surface energy and work of adhesion with water (Wap) increased. The acid-base component (Wap-AB) explained the increase of Wap. Our results suggested that the removal of surface lignin, exposure of carbohydrates and surface mobility of extractives are the main contributors to modifications of interfacial properties by kraft pulping. The role of interfacial properties on development of bleaching sequences and new pulp products was also briefly discussed.
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