Superheated steam treatment of rubberwood to enhance its mechanical, physiochemical, and biological properties

This research was aimed to investigate mechanical properties, color and cell-wall components changes, and durability of pre-dried rubberwood (Hevea brasiliensis) after superheated steam (SS) treatment. Wood samples were treated at different SS temperatures (140-180 degrees C) for 1-3 h. The highest compression strength parallel-to-grain, hardness and impact strength were found for samples treated at 160 degrees C for 3 h (30.7% higher than untreated), at 150 degrees C for 1 h (26.6% higher than untreated) and at 150 degrees C for 2 h (52.6% higher than untreated), respectively. The surface color became darker after each treatment in comparison with the untreated wood. The number of accessible hydroxyl groups decreased and the relative cellulose crystallinity increased with SS temperature, indicating decreased hygroscopicity of the treated wood. Also, SEM micrographs of wood surface showed consistent decrease in starch particles with treatment temperature. Both decay and termite resistances of treated rubberwood improved with treatment temperature. All the analyzes showed that dried rubberwood treated with SS had some improvements in the mechanical properties, decreased hygroscopicity, and increase resistance to decay.