Effect of Process Parameters in the Thermomechanical Densification of Pinus elliottii and Eucalyptus grandis Fast-growing Wood

Abstract

Densification parameters were investigated for the fast-growing pine and eucalyptus. Both woods showed optimal results in terms of apparent density and mechanical properties when milder treatments of 150 °C were applied. Pine showed mass loss and improved mechanical properties with a longer heating time of 60 min, while eucalypt performed better with shorter treatments of 30 min. Eucalypt has more highly acetylated hemicelluloses, mainly composed of xylose units, which degrade more quickly with consequent decrease in mass and mechanical properties. However, apparent densities close to 1.0 g·cm-3 were obtained, and greatly enhanced bending properties, hardness, and impact resistance were observed, especially when the optimal parameters were used. Treatments at 170 °C or greater, while resulting in well-densified specimens, yielded inferior mechanical properties. The densified woods also presented initial apparent contact angles greater than 85°, highlighting a considerable increase of hydrophobicity. The densification process therefore allows these less valuable timber species to be used in applications such as flooring and decking.