Fiber Surface Modification of Kraft Pulp in Presence of Chitosan Polymer

The effect of fiber surface modification on physical and mechanical properties of Kraft pulp was studied with and without Chitosan. First, the amount of carboxyl groups of Kraft pulp at different addition levels (0, 2, 3, 4 and 6%) of hydrogen peroxide was determined by means of methylene blue test. Then, the samples containing the highest carboxyl groups were treated at pH=8.5 with Chitosan at 0.75% addition level (based on oven dry pulp). Results showed that individual surface modification of fibers increased the strength properties of paper. It was also indicated that alone application of Chitosan can act as a dry strength agent due to its ability to produce Hydrogen, Ionic and Covalent bonding. Also, surface modification of fibers by H2O2 lead to increase of Carboxyl groups followed by increasing anionic charge with together with Chitosan formed a dual system. The effect of Chitosan on apparent density, tensile index and burst index of Kraft paper were significant and on the tear index of paper was not significant. In the current study, the best results obtained at level of 3% hydrogen peroxide.