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We compared the chemical composition of wood fibres and fibre surfaces of several eucalypt species and hybrids originating from various growth sites in South Africa. The objective was to test for differences in chemical surface composition due to genetics or site with the ultimate aim to facilitate a tailor-made supply of wood for pulping that results in an optimal blend of fibres that can be pulped together with similar yields. This, however, requires a sound knowledge of the fibre properties. The surface functionality on the single fibre level is a key property, because it determines how good inter-fibre bonding will be when paper is formed, which depends amongst other fibre properties on the amount of free hydroxyl groups that are available and therefore on the cellulose content on the fibre surface. The cellulose and lignin content on the fibre surface were determined with chemical force microscopy, a variation of atomic force microscopy. Since the general bulk composition of the fibre and the surface composition might differ, both parameters were determined. We found significant differences in the cellulose and lignin content on fibre surfaces, with regard to genotype and site, respectively. In some, but not all, cases, the surface composition of wood fibres followed the bulk composition, and differences were generally more pronounced. Differences due to genotype were significant, especially with regard to the surface lignin content-but variation due to site was also distinctly recognisable. This variation in surface functionality could be the reason why some pulpwood blends result in a lower pulp yield and different quality.

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This research work focuses on the effect of Libyan Kaolin clay particle size on the reheological, surface and mechanical properties of high density polyethylene (HDPE)/clay nanocomposites. Three polymer clay nanocomposites (PCNs) using 2 wt.% clay with different particle size (< 75, 75-150 and 150-300 μm) and 2 wt.% polyethylene grafted maleic anhydride (PE-g-MA) were prepared by melt processing method. The rheological (viscosity and melt flow rate), surface (wettability/hydrophilicity), and mechanical properties (tensile strength, elongation at break, Young's modulus, hardness and impact strength) were investigated. The obtained properties of PCNs were compared with HDPE. A better enhancement in the rheological properties properties was observed when clay particle size of < 75 µm was used. It was exhibited lower viscosity and higher MFR value, which provide better processing properties in comparison to HDPE and other PCNs. PCN with clay particle size of (75-150 µm) had more wettability and/or hydrophilicity than HDPE and other PCNs. Mechanical properties results showed significant improvement only in the impact properties as compared to HDPE. In short, PCN made with Libyan kaolin clay with particle size 75-150 μm appears to has comparatively better overall properties in comparison to other PCNs.