Wood basic density effect of Eucalyptus grandis in the paper making

Résumé

The basic density is the main technical property of the wood due to the fact of the easy determination and
correlation with the others wood properties. In this article, it was evaluated wood chips from a five-years-old
Eucalyptus grandis in three different silvicultural treatments for pulp and paper production. First, a conventional
kraft pulping was executed in the same conditions and then submitted to some elemental chlorine free
(ECF) bleaching process to achieve the target brightness of 88 ± 1% ISO. The bleached pulps were refined in
a Jokro Mill at 0, 2250, 4500 and 6750 revolutions and their physical, mechanical and optical properties were
analyzed. The statistical analysis indicated a difference in the wood basic density from the different silvicultural
treatments. The yield of the pulping process was not affected by the variation of the wood basic density.
The denser wood had the advantage of a lower specific wood consumption while the disadvantage was a
greater difficulty in the delignification and a decrease in the selectivity of the pulping process. The denser
wood was the one with the best bleachability and the one that most consumed chlorine in the bleaching process.
The increase of the wood density caused gains in the fisical and optical properties of the bleached pulp
and losses in the mechanical properties.The optical properties of the pulps from denser woods are more resistant
than the negative effects of mechanical properties.
Keywords: Kraft pulping; pulp bleaching; paper properties.