Study on the modification of bleached eucalyptus kraft pulp using birch xylan

In this study, birch xylan was deposited onto elementally chlorine free (ECF) bleached eucalyptus kraft pulp, and the corresponding changes in physical properties were determined. An aqueous 5% birch xylan solution at pH 9 was added to 5 wt% slurry of bleached kraft eucalyptus fibers, with stirring at 70°C for 15 min after which the pH was adjusted to 5-6. The xylan enriched fibers were isolated by filtration and used for physical testing. A 1.15 wt% adsorption of birch xylan on the kraft fibers at 8% xylan addition increased the tensile index, strain and tensile energy absorption values by ∼10%, while the burst index increased by 20.15%. The tear index increased by 2.55% with the adsorption of 0.87 wt% birch xylan on the eucalyptus kraft pulp at 3% xylan addition. The pulp beatability was also improved by adding birch xylan. The surface morphology of the unmodified and modified pulp samples were analyzed using atomic force microscopy (AFM) in the tapping mode. The analysis revealed the differences in the fine structure of fibers which showed micrometer-sized xylan structures spreading over the fiber surfaces.