Estudo do ângulo microfibrilar da madeira de Eucalyptus grandis, úmida e seca, por microscopia de luz polarizada e estimada por difração de raios X

Abstract

Wood drying is indispensable for most of the purposes for which it is intended, however, the removal of water from the wood can lead to defects. From the point of view of the ultrastructure of the cell wall, the information are scarse about the influence of drying, even in the microfibril angle (MFA). The objectives of this work were to use the X-ray diffraction technique to estimate the microfibril angle and to evaluate the variation of the microfibril angle after wood drying of Eucalyptus grandis Hill ex Maiden. The basal discs of two 22-year-old trees were used to produce the specimens used for both MFA measurement by polarized light microscopy and X ray diffraction method. These specimens also were used for evaluation of the influence of drying on the MFA. From the obtained results it was possible to observe that: the average MFA measured by polarized light microscopy was equal to 7°. It was possible to estimate the AMF as a function of the T value obtained from the X ray diffraction using the cubic model AMF = -12.198T 3 + 113.67T 2 – 348.4T + 358.09 (R 2 = 0.99). The average AMF estimated by this equation was 7.35°. The microfibril angles decreased after the wood drying.