THE EFFECT OF WOOD RAW MATERIALS AND FIBRE PROPERTIES ON THE DEVELOPMENT OF BONDING ABILITY AND PAPER PROPERTIES OF TMP

The main objective of this study was to investigate the correlation between specific surface area in the paper structure and bonding ability of mechanical pulp. A secondary objective was to investigate the effect of fibre properties on paper cross-sectional characteristics and paper properties. Fibre bonding ability of mechanical pulp fibres was assessed by testing handsheets for density and tensile strength. The specific surface area of handsheets with different fibre characteristics (fibre wall thickness, fibril angle), was measured using scanning electron microscopy. The specific surface area in paper increased with specific refining energy and external fibrillation of long fibres, thus contributing to improved paper strength. The results showed that the specific surface area is increasing with the fines content in paper, leading to dense and strong paper. To describe the quantitative effect of fibre dimensions on paper properties, linear regressions models were applied. The regression models showed that fibres with thin walls give dense and strong papers, whereas fibres with low fibril angle give low roughness values, probably because the fibres collapse more easily.