A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Pulp and Paper Technology

Thesis (M.Sc.) - Asian Institute of Technology, 2007

Eucalyptus camaldulensis wood chips were cooked to kappa number of 19.6 and 82.2 meq/kg HexA content by kraft pulping. Total carboxylic acid in unbleached pulp was 121.4 meq/kg and HexA group contributed about 68% of the total carboxylic acid content. The unbleached pulp was oxygen delignified and bleached to fu ll 90-92% ISO brightness. The bleaching sequence of Do(EOP)D1was found efficient to produce low HexA content of 3.7 meq/kg of pulp and Q(PO)DQ(PO) produced high HexA content of 10.4-49.7meq/kg of pulp. HexA did not show any effect on brightness reversion. Chlorine dioxide reduced effectively HexA group in pulp, oxygen and peroxide chemical were less reactive. Carboxylic acids group other than HexA group in pulp were not changed too much during the bleaching process and these acidic groups varied 33.7 to 41.9 meq/kg in bleached pulp. However, total carboxylic acid varied from 45.6 to 83.4 meq/kg. Fiber charge by both polyelectrolyte titration and conductometric titration method varied from 21.4 to 33.8 mmol/kg and 33.6 to 60.9 mmol/kg of pulp respectively. Higher HexA content in pulp produced high charge on the fibers. Higher HexA content up to some level in the pulp produced slightly better tear strength, Scott bond strength and stretch at the 50 to80Nm/g tensile index level than the low HexA pulp. Higher HexA pulp also produced better surface smoothness, formation and porosity. Considering all results, it might be stated that higher HexA content in pulp could improve its papermaking properties, although the effects are small.