Reduction in dimensional changes of Jatobá (Hymenaea sp.) and Muiracatiara (Astronium sp.) submitted to additional heat treatment.

Dimensional changes are undesirable wood characteristics and are caused, mainly, by its hygroscopic nature. Seeking to reduce this effect, the present study aimed to improve the dimensional stability of two hardwood species, with the application of additional heat treatments to seasoned lumber as well as to kiln dried lumber. The selected wood species are commercially known as Jatoba and Muiracatiara. The heat treatments consisted in wood exposition to temperatures at 60 degrees C, 75 degrees C and 90 degrees C during 24, 48, 72 and 96 hours, respectively. After the heat treatment, the samples were placed in an environment with low relative humidity (Condition 1) and, after reaching equilibrium moisture content, they were stored in an environment with high relative humidity (Condition 2). At the end of storage, the shrinkage and swelling rates of samples were measured. The results show that the heat treatments reduced dimensional changes of wood caused by changes in the moisture content changes. The temperature of 90 degrees C provided the lowest shrinkage and swelling rates, both in air dried and kiln dried lumber.