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The inherent relationships between the surface phenomena and chemical structures of thermally modified bamboo were investigated to predict the intrinsic properties of bamboo during the thermal modification through the surface phenomena effectively. Moso bamboo was firstly treated by vacuum treatment at 150°C, 170°C, 190°C and 210°C for 1, 2, 3 and 4 h, respectively. And then the surface colour, contact angle and chemical compositions of heat-treated bamboo and in-situ chemical properties of the heat-treated cell wall were analysed by using the colour metre, contact angle metre and confocal scanning microscope. Results showed that the surface colour became darker and the hydrophobicity was increased after heat treatment. As compared to the control, the lightness (L*) value carried out in accordance with CIELAB of heat-treated bamboo decreased by almost 54% and the maximum increase of contact angle was 160%. The surface colour and contact angle of bamboo were closely related to the lignin content. The darkened colour and increased hydrophobicity of the bamboo surface were caused by the crack of C–O–C and the decrease of C=O in lignin. Furthermore, fluorescence analysis indicated that the lignin distribution in the cell wall increased gradually after heat treatment, especially in the thick-walled cells and the corners of cells. [ABSTRACT FROM AUTHOR]

Moso bamboo was firstly treated in a vacuum chamber at 150°C, 170°C, 190°C, and 210°C for 1, 2, and 3 h, respectively. Nano-TiO2 gel were then coated on the surface of thermally treated (TM) bamboo. Finally, specimens were radiated by an accelerated aging chamber of xenon lamp for 144 h. Chroma Meter, Scanning electron microscopy and Energy-dispersive spectroscopy (SEM-EDS) were applied to investigate the effect of nano-TiO2 coating on the surface color stability of TM bamboo. Results revealed that TM imposed a significant effect on the surface color of bamboo, e.g. when treatment temperature and duration increased, bamboo surface became darker. The color parameters of TM bamboo coated with nano-TiO2 gel after aging were close to the bamboo before aging, indicating that the photo-discoloration resistance of the TM bamboo has been improved. The nano-TiO2 gel with a concentration of 10% shows a better effect than that of 5%. After aging for 144 h, the ΔE of TM bamboo (190°C/2 h) coated by nano-TiO2 gel with a concentration of 10% was 2.90, which decreases by 25% compared with that of uncoated bamboo. Furthermore, the nano-TiO2 coating had no obvious aging failure after 144 h aging, which avoided the leaching of TiO2 particles during the long-term service. [ABSTRACT FROM AUTHOR]

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 FROM AUTHOR]

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 FROM AUTHOR]

Bamboo has shown great potential in many fields, including construction, furniture, and decoration due its fast growth rate, excellent mechanical properties, and short rotation cycle. Vascular bundles of bamboo culm walls are less studied owing to their complexity and uneven distribution. In this study, the changes in the mechanics of bamboo cell walls from the bamboo inner (BI) layer to the bamboo outer (BO) layer after hydrothermal modification of the bamboo sample were analyzed. These changes were investigated using a scanning electron microscope, nano-indentation, X-ray photoelectron spectroscopy, atomic force microscope, wet chemistry method, and Fourier transform infrared spectroscopy. The use of high-temperature water and high-pressure treatment deformed and distorted the structure of thermal-modified bamboo. In addition, the hemicellulose and cellulose contents of the bamboo cell wall decreased. Thermal-modified bamboo exhibited a higher lignin content (27.2%) than the control (22.4%). Statistical analysis showed no significant difference in hardness from the BI layer to the BO layer. However, the elasticity modulus of the bamboo middle layer was lower than that of BI and BO. Moreover, the creep ratio of the sample decreased after hydrothermal modification at 170 °C. Furthermore, the changes in macro-physical, mechanical, and anti-mildew properties and surface hydrophobicity were investigated. This study revealed and analyzed the change tendency in mechanical properties of bamboo cell walls from the BI layer to the BO layer. Furthermore, compared with untreated bamboo sample, hydrothermally modified bamboo samples exhibited excellent anti-mildew property in 30 days. • Micro-mechanical properties of bamboo in different parts. • Hydrothermal modification enhanced the anti-mildew property of bamboo. • The mechanics of bamboo cell walls increased significantly. [ABSTRACT FROM AUTHOR]

Thermal-treated (TMT) bamboo and TMT bamboo-based panel have a great potential application in the outdoor constructions. In this paper, the effects of the changes in terms of microstructure, chemical structure, and surface wettability of bamboo after TM on the adhesive penetration and shear strain distribution of glued TMT bamboo were investigated with scanning electron microscopy (SEM), Fourier transform infrared (FTIR), fluorescent microscopy, and digital image correlation (DIC). Results indicated that the partial pits on cell walls became smaller due to the shrinkage of bamboo cells and partial pits were covered by the coagulation of lignin after thermal treatment (TM). Both the changes in surface morphology, microstructure and the degradation of hemicelluloses decreased the permeability of phenol-formaldehyde adhesive on bamboo surface. The average penetration and effective penetration depth of phenol-formaldehyde adhesive on the TMT bamboo which was treated at 190 °C for 3 h decreased by about 24% and 37%, respectively, as compared to the control. The failure mode of glued TMT bamboo was mainly manifested as interlayer slipping and the strain accumulated in the bonding interphase of glued TMT bamboo during lap-shear test, which indicated that TM negatively affected the bonding performance of bamboo and phenol formaldehyde (PF) adhesive. As expected, the bonding strength of glued TMT bamboo at 190 °C for 3 h decreased by 63% in comparison with the control. • Pits on bamboo cell walls became smaller and were partially covered by the coagulation of lignin after TM. • The penetration of PF adhesive on the thermal-treated (TMT) bamboo decreased. • The strain accumulated in the bonding interphase of glued TMT bamboo during Lap-shear test. • The bonding strength of glued TMT bamboo decreased obviously in comparison with the control. [ABSTRACT FROM AUTHOR]