A comparison of the surface properties of ECF and TCF bleached softwood kraft pulp

The aim of this study was to determine the influence of different bleaching sequences on the fibre surface properties of softwood kraft pulp, before and after ageing. This was done by measuring the Dynamic Contact Angle (DCA) in water and by performing Electron, Spectroscopy for Chemical Analysis (ESCA) on the pulp fibres. The study, which was conducted on Elemental Chlorine Free (ECF) and Totally Chlorine Free (TCF) bleached softwood pulps, showed that there were measurable fibre surface differences between bleached pulps, depending on the bleaching method applied. The DCA was consistently higher for the TCF fibres. The change in the fibre properties after a storage period of six months, measured as DCA, was more pronounced for the ECF fibres. A higher contact angle of the fibres after storage indicated either a migration of extractives and/or lignin from the fibre wall to the surface or a change in the components on the fibre surface which caused it to become more hydrophobic.