Umidade de equilíbrio e retratibilidade da madeira de Corymbia citriodora (Hook.) K.D. Hill & L.A.S. Johnson na Bahia

Abstract

Determining the equilibrium humidity is important so that the wood does not present defects, such as cracks and warping, resulting from the drying process and contractions that occur in different ways in the structural planes of the wood. The objective of this work was to determine the equilibrium humidity and shrinkability for Corymbia citriodora wood in the municipality of Cruz das Almas/BA. A tree was selected and then discs were removed from the base and the remainder every 1.5 meters, totaling 10 discs. From these discs, 198 samples measuring 50 x 30 x 20 mm were taken. During a period of 27 months, the dimensions were measured with the aid of a digital caliper and subsequently weighed on an analytical balance to obtain the mass of each sample. With the data, it was possible to determine the humidity, total and partial linear contractions, volumetric contractions and the anisotropy coefficient. In this way, it was found that the equilibrium humidity of Cruz das Almas/BA is 12.65% and can vary from 11.47% to 13.83%; total longitudinal, tangential, radial and volumetric contractions presented average values ​​of 0.52%, 6.12%, 6.70%, 12.86%, respectively. The anisotropy coefficient above the PSF was 0.92. The longitudinal, tangential, radial and volumetric partial contractions presented average values ​​of 0.15%, 3.03%, 2.79%, 5.87%, respectively. At equilibrium humidity, the anisotropy coefficient was 1.11.