Acacia hybrid (Acacia mangium=auriculiformis) sapwood was heat-treated in nitrogen under laboratory conditions for 2-6 h at 2108C-2308C. Chemical composition and physical properties including water absorption and swelling were examined. The results showed that these properties were reduced significantly by heat treatment, and there is an interactive effect of temperature and time on them. Chemical changes of the wood surface were determined by X-ray photoelectron spectroscopy analysis. Results indicate that the O/C ratio decreases as a function of treatment intensity due to the migration of extractives and degradation products to the surface during heat treatment. The C 1s peaks showed an elevated content of lignin and extractives, whereas the hydroxyl group content was diminished with elevated treatment temperature. The O 1s peaks revealed an increase in the O 1 peak and confirmed the course of C 1s peaks. These results coincide with the decrease in water absorption and swelling of wood after heat treatment.
The hydrophobicity and color stability of wood are important properties that can be easily changed when wood is used as a raw material for outdoor products, reducing the service life of wood. Herein, an epoxy@ZnO coating was applied by a two-step simple spray coating method to improve the hydrophobicity and color stability of Styrax tonkinensis wood. The hydrophobicity, robustness of coating, as well as the color stability of uncoated wood samples and epoxy@ZnO coated wood samples were evaluated. The microstructure morphology and crystal structures of the coating were also characterized by a field-emission scanning electron microscope (FESEM) and X-ray diffraction (XRD) analysis, respectively. Results showed that the obtained epoxy@ZnO coating was not only superhydrophobic with an average water contact angle of 154.1°, but also maintained superhydrophobicity with an average water contact angle of 149.6° after five water jetting tests. The color stability of the coated wood samples was improved by around 50% compared to that of uncoated wood samples. Additionally, a continuous epoxy@ZnO coating with hierarchical micro/nanoscale structures constructed by the wurtzite hexagonal structure of ZnO micro/nanoparticles on wood surfaces was confirmed.
TiO 2 -treated acacia hybrid (Acacia mangium x auriculiformis) wood was fabricated by combined pressure-impregnation and hydrothermal posttreatment. The wettability and microstructure morphology, as well as the crystalline structure of the titanium dioxide (TiO 2 ) gels of the TiO 2 -treated wood, were studied. Contact angle measurements of the blank wood and the TiO 2 -treated wood indicated a significant increase in hydrophobicity, with contact angles of above 150° in treated samples. Furthermore, the water-resistant property of the treated wood was quite stable, even after immersion in boiling water. Field emission scanning electron microscopy (FE-SEM) results showed that the microstructure morphology and the size of TiO 2 gels on the wood surface were dependent on the pH of the post-treatment solutions. Additionally, the presence of amorphous TiO 2 gels was indicated by X-ray diffraction (XRD) analysis. The results of this study indicate that combined pressure-impregnation and hydrothermal post-treatment can create a hydrophobic wood-TiO 2 composite.
Acacia hybrid (Acacia mangium x auriculiformis), a wood species of low dimensional stability which is used almost exclusively for pulp, paper, or as firewood, was heat treated in nitrogen at 210-230 ºC for 2 to 6 hours. The changes in color and anti-swelling efficiency (ASE) of wood after heat treatment were determined for the different heat treatment conditions. The results show that heat treatment mainly resulted in the darkening of wood tissues, and heat-treated wood had better dimensional stability than those of the control samples. Chemical modifications of wood components were determined by FT-IR analysis. Spectra indicated that the hydroxyl group content was reduced by increased treatment intensity. This result coincides with the increase in dimensional stability of heat-treated wood. Heat treatment of acacia hybrid wood shows an interesting potential to improve the quality and value for solid wood products from plantation-grown wood species.
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