Influence of kappa number of unbleached pulp on ECF bleachability of Eucalyptus globulus kraft pulps

This work aims to investigate how kappa number of Eucalyptus globulus kraft pulps affect their bleachability by DEDED sequence and to establish correlations between bleaching response and the chemical structure of pulp. The amount of ClO2 required to reach 90.5 % brightness decreases as kappa number of unbleached pulp decreases. However, the resistance to bleaching (expressed as the amount of oxidation equivalents (OXE) required to reduce a kappa number unit) increases as kappa number of initial pulp decreases. The low bleaching response with the decreasing of pulps kappa number correlates with a decreasing content of betaO-4 units and increasing content of "condensed" structures in linin and hexenuronic acids in hemicelluloses. No clear correlation could established between extractives content composition and bleachability.