The effects of bulk and surface chemical composition on the mechanical properties (MP) of eucalyptus kraft pulp were investigated using Liquid Chromatography (HPLC), Scanning Electron Microscopy (SEM), X-ray Photoelectron Spectroscopy (XPS) and Principal Component Analysis (PCA). SEM images of fractured regions during tear (TrID), tensile (TsID) and burst (BuID) tests of refined pulps showed fibre deformation and low proportion of broken fibres, indicating an inter-fibre failure in the sheet network. TrID of unrefined samples was affected by lignin surface coverage (SLig) while TsID and BuID were affected by surface coverage of extractives (SExt) and carbohydrates (SCar). After refining, TrID was affected by uronic acids (UA) in xylan and the influence of bulk composition was more pronounced. Our results also indicated that the fibre-to-fibre bonding rather than the individual fibre strength was the limit factor for MP. A strategy combining surface modification and preservation of polysaccharides in pulping was suggested to improve the MP of this material.
eucalyptus; cellulosic fibre; surface composition; mechanical properties; XPS; PCA
