Kraft pulp hornification: A closer look at the preventive effect gained by glucuronoxylan adsorption

Xylan is known to adsorb irreversibly on cellulose and on bleached kraft pulp fibres. This investigation shows that adsorption of birch glucuronoxylan (GX) reduces the degree of drying-induced property changes of bleached softwood kraft pulp fibres. GX was adsorbed at different amounts on never-dried fibres, which provided pulps with xylan contents ranging from 67 to 126 mg/g. By fluorescent labelling of the GX, followed by adsorption and subsequent imaging using confocal laser scanning microscopy, it was concluded that GX adsorbs on fibril surfaces throughout the fibre wall with enrichment on the outer fibre surface. Adsorption of GX before drying preserved a considerable part of the fibre-swelling (water retention value and fibre saturation point), specific fibre surface area, and wet fibre flexibility observed in the never-dried state. It is therefore suggested that GX adsorption reduces the degree of drying-induced fibre wall cross-linking. The use of GX as a hornification inhibitor would provide once-dried pulps with increased tensile strength and beatability.