Abstract

Densification of wood leads to improvement of its mechanical properties. Specimens of Pinus radiata and Eucalyptus nitens wood were densified using heat, steam, and pressure to improve their mechanical properties and thus enhance their utilization. At a maximum steam pressure of 550 kPa and a maximum press hydraulic pressure ranging from 4.5 to 9 MPa, selected temperatures of 160 degrees C, 180 degrees C, and 200 degrees C were used to check the mechanical properties and to identify the chemical composition of wood samples before and after densification. Densified wood samples showed markedly reduced hygroscopicity. The chemical changes in the wood constituents occurring during densification were characterized using FT-IR, Py-GC/MS, and XPS. According to the densification process between pine and eucalyptus, the results obtained showed that the densification effects were better for Eucalyptus nitens than for Pinus radiata. The FT-IR analysis revealed a high condensation index for pine lignin and the low condensation index for eucalyptus lignin, indicating easier formation of C-C linkages by densification in pine lignin. Py-GC/MS analyses were performed to follow the lignin/carbohydrate ratio, and these revealed major carbohydrate losses during densification at the highest temperature.