An investigation of pulp fibre surfaces by atomic force microscopy

When wood fibres bond to form a paper sheet, it is their external surfaces that first come into contact. Thus, the external surface and its properties play a very important role in determining the strength of the paper sheet. In this study an atomic force microscope (AFM) was employed to probe the external surface of the fibre. Force spectroscopy studies performed on wet pulp samples indicated the presence of a compliant fibrillar layer at the surface, the thickness of which increased with the degree of beating. The moduli of the external compliant layer and the cell wall were obtained by fitting the force spectroscopy data to Sneddon's model. A Adhesion force measurements between a spherical AFM tip coated with hydroxypropyl cellulose and fibre surfaces indicated that the degree of bonding improved with beating. The presence of a fibrillar layer at the surface was confirmed by high-resolution total internal reflectance fluorescence microscopy.