Densificação termomecânica da madeira de Tectona grandis de 15 anos para produção de piso

Abstract

Teak wood from fast-growing plantations generally has a high proportion of juvenile wood and sapwood, which have less attractive characteristics for the industry, such as lighter color, greater dimensional instability, lower density and hardness values. This means that they are not used for higher value-added products such as flooring. In this context, thermo-mechanical densification could be an alternative treatment to improve some of the properties of juvenile wood and contribute to its greater use in the flooring industry. The aim of this study was to evaluate the use of thermomechanically densified 15-year-old Tectona grandis wood for the flooring industry. Processed T. grandis wood from a 15-year-old plantation was used, which was thermomechanically densified in a thermo-hydraulic press under different conditions: temperatures of 150°C and 170°C and densification rates of 24.0% and 36.7%, as well as raw wood (control). The compaction ratio, mass loss, spring back, surface changes in color, roughness, wettability and surface density were evaluated. The apparent density, wood moisture after equilibrium, water absorption, swelling in thickness, set recovery, changes in chemical constituents, Janka hardness and in-service flooring simulation tests were also evaluated. There was an increase in mass loss as the temperature rose, with values equal to 5.14% and 6.97% for treatment temperatures of 150oC and 170oC, respectively. The spring back had an average value of 5.62%. Thermomechanical densification made the wood surface more hydrophobic, darker and less rough. X-ray densitometry showed that the surface density of densified wood was higher (maximum 1.05 g.cm-3) than the central region of the specimen, whose average value was approximately 0.60 g.cm-3. FTIR showed a greater reduction in -OH bonds and degradation of hemicelloloses at the temperature of 170oC. The apparent density of the wood increased from 0.59 g.cm-3 to an average of 0.78 g.cm-3 for the treatments in which the 36.7% densification rate was applied at both temperatures. Wood moisture at equilibrium fell from 11.01% to 4.87% for wood treated at 170oC and 36.7% densification rate. All treatments showed greater water absorption than the control at 48 and 72 hours. For thickness swelling, all the treatments showed higher values than the control due to the greater amount of cell lumen available. Set recovery decreased as the densification rate increased, with values equal to 38.20% and 12.52% for densification rates of 24.0% and 36.7%, respectively. The Janka hardness of the densified wood ranged from 82.36 MPa to 89.60 MPa, with an increase of up to 141.18% compared to the control. There was an improvement in the mechanical resistance of the thermomechanically densified wood in the in-service floor simulation tests compared to the raw wood, for the falling steel ball, indentation applied to small areas and rolling load. Thermomechanically densified floors of the researched Teak wood can be suitable for moderate and heavy traffic environments, while natural floors would be only suitable for low traffic. It was concluded that the application of thermomechanical densification of wood promoted positive changes in the quality of wood used for solid flooring, improving the surface, chemical, physical and mechanical properties of 15-year-old T. grandis wood.