Modification of fibre surfaces during pulping and refining as analysed by SEM, XPS and ToF-SIMS

The effects of laboratory pulping and refining on the surface properties of eucalyptus kraft pulp fibres were investigated using Scanning Electron Microscopy (SEM), X-ray Photoelectron Spectroscopy (XPS or ESCA) and Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS). Refining affected fibre structure, surface morphology, lignin (φlig), carbohydrate (φcarb) and extractive (φext) surface coverage. The φlig and φcarb, estimated with XPS, decreased and increased with refining, respectively. The φext changed according to the pulping conditions. Cellulose, xylan, lignin, sterols, fatty acids and their salts were identified by ToF-SIMS. Significant changes in the normalized ToF-SIMS peak intensities were observed after refining. The release of xylan and fatty acid salt aggregates formed in pulping and entrapped in the cell wall pores with subsequent adhesion to the fibre external surfaces was suggested as a source of surface chemical modification by refining.