Caracterização da madeira de tração em Eucalyptus grandis e sua influência na produção de polpa celulósica / Characterization of tension wood in Eucalyptus grandis and evaluation of its effect on Kraft pulp production

AUTOR(ES)

Leonardo Chagas de Sousa

DATA DE PUBLICAÇÃO

2004

RESUMO

The reaction wood in broadleaved tress, usually called tension wood, is found on the top side of stems and branches, causing them to reorient themselves by longitudinal shrinkage. It is characterized by a high proportion of cellulose and low of lignin, when compared to normal wood. The fibers usually show an abnormally thick wall, called gelatinous layer, on the inside of the secondary wall. Due to its effect on wood properties, reaction wood may be considered a serious problem in cellulose manufacture and also for the industry of solid wood products. This study had the objective of characterizing tension wood in Eucalyptus grandis and of evaluating its effect on cellulose production. Three inclined trees were chosen, harvested and cross-cut in 1.0 m long logs, from the bottom of the trees up to the first branch. Results showed that the tension wood in the trees had higher specific gravity and higher shrinkage values. The chemical composition also changed, with a smaller percentage of lignin and of extractives. Anatomically, it was found that the fiber width remained the same as that in normal wood, although its wall thickness increased due to the gelatinous layers. The fibers are also significantly longer. The vessels found in tension wood were smaller and less frequent. As to pulping, it was found that tension wood required a smaller quantity of chemicals to reach a prescribed kappa number. This is due to the low lignin concentration. The viscosity of pulp from tension wood was the same as that of normal wood, this indicating that the degree of polymerization is lower in tension wood, seeing that less pulping chemicals were used. A very important finding was that the yield was significantly higher in pulping tension wood, mostly due to the presence of the gelatinous layer. The yield for normal wood was 49%, while that for tension wood reached about 58%.

ASSUNTO(S)

madeira de tração eucalyptus grandis celulose kraft tension wood eucalyptus grandis kraft pulp recursos florestais e engenharia florestal

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