Effects of Microstructure and Chemical Composition on the Visual Characteristics of Flattened Bamboo Board

Flattened bamboo board is a new type of bamboo-based panel with various colors that maintains the natural texture of bamboo, and is gradually being used in indoor home decoration. Revealing the influence mechanism on the visual effect of flattened bamboo boards is the key to improving the processing of such boards for household materials. This study employed visual physical quantity measurement methods, field emission scanning electron microscopy, FTIR spectroscopy, and XPS to investigate the visual physical quantities, morphology, and chemical composition of flattened bamboo boards. The results showed that compared with the control samples, the bamboo outer layer boards were dark brown, with the largest Delta E* (38.55), while the outer boards were reddish-brown, with the largest a* (8.82). The inner boards were yellow-red and showed a lower Delta E* (6.55). Due to the elevated density, abundant inclusion, and wax, the bamboo outer layer board exhibited the highest glossiness and darkest color, followed by the outer board and the inner board. The FTIR spectroscopy revealed that hemicellulose decomposed, and the relative content of lignin increased, leading to color changes in the flattened bamboo boards. The bamboo outer layer board was the darkest due to changes in C=C bonds at 1600 cm-1 and 1509 cm-1. The surface color of the outer board was mainly red, which may be caused by C-O bonds at 1239 cm-1. The surface of the inner board was mainly yellow, which may be caused by the C-H stretching vibration of lignin at 1108 cm-1. XPS analysis showed that the proportion of C1 and O1 increased, while C2, C3, and O2 decreased, indicating that hemicellulose degraded at high temperatures, which increased the relative lignin content. Changes in the relative content of oxygen-containing functional groups and SiO2 in the flattened bamboo board were important factors responsible for the change in visual physical quantities.