Physiochemical Properties of PGW Fibres as Determined by the Process Intensity and Wood Fibre Morphology, 1999 International Mechanical Pulping Conference Proceedings

Kathrin Mörseburg and Bruno Lönnberg

Åbo Akademi University

Automatic image analysis has revealed the existence of distinctive fibre width fractions in pressure groundwood pulps from Norway spruce (Picea abies Karst.). These width classes were identified as ribbon and string-like particles of a high slenderness, fibre fragments and residues of tracheids with a more particular character. The proportions of these different components in a certain pulp were strongly determined by the specific energy consumption and the morphological characteristics of the selected raw material.

Grinding introduces a significant extension of the width and the cell wall thickness to the fibre, which is due to delamination and splitting of the fibre wall. The increase in fibre width is higher for thinwalled tracheids. The generation of smaller particles in grinding is as well a result of the structural alterations of fibre wall as an effect of the fibre length reduction. Hence the various size fractions in pressure groundwood pulps also show a rather gradual variation of their chemical composition.