Physical and chemical changes in juvenile and mature woods of Pinus elliottii var. elliottii by thermal modification
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This study is aimed at evaluating the effect of thermal treatment on the physical and chemical properties of juvenile and mature wood from Pinus elliottii. Boards were taken from 35-year-old P. elliottii var. elliottii trees. The boards were thermally modified at 200 A degrees C in the Laboratory of Wood Drying and Preservation from UNESP, Botucatu, SP, in Brazil. The results indicated that the thermal modification caused: (1) decreases of 20.1 % and 16.1 % in the equilibrium moisture content and volumetric swelling of mature wood, respectively; (2) decreases of 22.9 % and 14.8 % in the respective properties of juvenile wood; (3) increases of 34.1 % and 89.2 % in the extractive content of juvenile and mature wood, respectively; and (4) decreases of 3.4 % and 4.6 % in the respective holocelluloses content due to degradation in the hemicelluloses. It was found that juvenile wood presents an adverse effect on the chemical modification caused by thermal treatments. The influence of thermal modification in juvenile wood was lower than in mature wood and caused a greater uniformity in the physico-chemical variations between these types of wood.