ABSTRACT
Wood is easily affected by decay fungi, mildew fungi, insects, water, UV, and other factors when used outdoors. In particular, mildew on the surface of wood negatively affects the appearance and practical use of wood or wood-based engineered products. In recent years, as a class of popular crystalline materials, metal-organic frameworks (MOFs) have been widely applied in electrochemistry, adsorption, anti-mildew efforts, and other areas. In this study, we first grew a Co-based metal-organic framework (Co-MOF) in situ on a wood surface and subsequently converted the Co-MOF in situ into a cobalt-nickel double hydroxide layer, which formed micro- and nanohierarchical composite structures on the wood surface. The low surface energy of the CoNi-DH@wood was further modified via impregnation with sodium laurate to obtain the superhydrophobic wood (CoNi-DH-La@wood). We characterized the microstructure, chemical composition, water contact angle, and anti-mold properties of the CoNi-DH-La@wood using SEM, XRD, XPS, water contact angle tests, and anti-fungal tests. The SEM, XRD, and XPS results confirmed that the metal-organic framework was coated on the wood surface, with the long-chain sodium laurate grafted onto it. The CoNi-DH-La@wood had a water contact angle of 151°, demonstrating excellent self-cleaning ability. In addition, the fabricated superhydrophobic balsa wood exhibited excellent chemical and environment stability. Lastly, the CoNi-DH-La@wood exhibited excellent anti-mildew properties in a 30-day anti-mildew test because the superhydrophobic coating was successfully coated on the wood surface. In summary, this work presents an attractive strategy for obtaining wood with superhydrophobic properties at room temperature, thereby endowing the wood or wood-based engineered products with excellent anti-mildew properties.
ABSTRACT
In this paper, we introduced a bamboo longitudinal flattening technology and analyzed the effects of the softening-flattening process on the physical and mechanical properties of moso bamboo. This is a newer bamboo processing technology that can enhance the utilization and reduce pollution compared with traditional bamboo-based products. Results showed that the parenchyma cells distorted and compacted due to the flattening process. The hemicellulose and cellulose content decreased, while the content of lignin presented an increasing tendency. As expected, the dimensional stability of moso bamboo enhanced due to the decrement of hemicellulose. The softening-flattening process positively contributed to the micro-mechanical properties of treated bamboo specimens. For example, the hardness and modulus of elasticity of the untreated bamboo sample increased from 0.58 and 15.7 GPa to 0.8 and 17.5 GPa, respectively. In addition, the changes in cellulose crystallinity and mechanical properties were also investigated in this paper. The cellulose crystallinity increased from 37.5% to 43.2%, significantly. However, the modulus of rupture of the flattened bamboo board decreased from 9000 to 7500 MPa due to the grooves made by the flattening roller. The MOE of flattening bamboo board showed the same decreasing tendency.
ABSTRACT
In recent years, saturated steam heat treatment has been considered as an environmentally friendly and cost-effective modification method compared with traditional heat treatment media. In this study, bamboo was treated by saturated steam, and the change in chemical composition, cellulose crystallinity index, micro-morphology, and micromechanical properties were analyzed by a wet chemistry method, Fourier transform infrared (FTIR), scanning electron microscopy (SEM), X-ray diffraction (XRD), nanoindentation, and so on. Results illustrated that the parenchyma cell walls were distorted due to the decomposition of hemicellulose and cellulose in bamboo samples. As expected, the hemicellulose and cellulose content decreased, whereas the lignin content increased significantly. In addition, the cellulose crystallinity index and thus the micromechanical properties of bamboo cell walls increased. For example, the hardness increased from 0.69 GPa to 0.84 GPa owing to the enhanced crystallinity index and lignin content.
ABSTRACT
Bamboo scrimber is a new type of bamboo-based panel that is prone to be affected by biological and service environments under outdoor conditions. In this paper, the physical and mechanical performance and the microchemical and surface properties of untreated and hot-oil-treated bamboo scrimber were analyzed to illustrate the processing mechanism of scrimber. Methyl silicone oil treatment was carried out at 120, 140, and 160 °C for 2, 4, and 6 h. The density, mechanical properties, air-dried moisture content, surface morphology, chemical structure, swelling properties, color, and contact angle of the bamboo scrimber were analyzed to evaluate the treatment effectiveness. Observation of the environmental-scanning electron microscope indicated that the glue layer of the bamboo scrimber was not significantly damaged after hot oil treatment. At low temperatures, the mechanical properties did not change significantly. Infrared-spectrum analysis showed a significant decrease in mechanical properties at higher temperatures and longer treatment time for the degradation of hemicellulose. The contact angle test and swelling properties test showed that the hot oil treatment improved the dimensional stability and reduced the wettability on the surface of the bamboo scrimber. The above analysis results show that the treatment at 140 °C for 2 h is most effective.
