Limitations of bleached eucalyptus pulp viscosity as determinant for its quality

Production segregation at pulp mills as a function of the results of viscosity analysis is very common. Erroneously, direct inferences about physical properties of the fibers are also made on the basis of its results. Aiming to demonstrate the non-existence of a direct relationship between viscosity and the physical properties of the pulp, the pulp viscosity was modified at the oxygen delignification by varying the alkaline charge. After bleaching, the samples were subjected to analysis of viscosity, pentose content, and refining, followed by an analysis of tensile strength and tear strength, and calculation of the elastic modulus and tenacity on the tension-deformation curve. The results showed that the increase in the alkaline charge at oxygen delignification leads to significant reductions in viscosity and pentose content. The tensile and tear indexes did not show significant variations as a function of viscosity, and alterations in the elastic modulus and tenacity were only observed at lower values, indicating that viscosity is not suitable for physical property prediction.