Altera??es na estrutura anat?mica da madeira de cavacos de eucalyptus grandis em três condi??es de desfibramento para a confec??o de painéis MDF

摘要

The use of eucalyptus wood for production of MDF panels is recent, becoming necessary to understand the changes in the anatomical structure during the stages of industrial processing, especially during wood chip refining. With this aim, in the present work three different conditions of wood chip refining were applied (i) chip heating time, (ii) digestion and refining pressures and (iii) the specific refining energy, and the anatomical characteristics of wood cell components were evaluated. Increase in the intensity of wood chip refining reduced the fiber mean length and increased the percentage of broken fibers. This corroborated with the images of scanning electronic microscopy, besides decreasing the number of vessel elements and parenchyma cells. The more intense refining condition promoted a characteristic darkening of the pulp composed by the wood cell elements. The application of lighter refining variables increased the frequency of fiber bundles, number of vessels and parenchyma, resulting in pulp with clearer coloration. The morphological changes in cell components of eucalyptus wood chips caused by the refining treatment were related with the stages of the operational process and the technological quality of MDF fiberboard.