Effects of pith ring on the hygroscopicity and dimensional stability of bamboo

Abstract

The pith ring is an important component of bamboo, which is located on the inner side of the culm wall. However, the effect of pith ring on bamboo properties is unclear. The study aimed to analyze the influence of pith ring on the hygroscopicity and dimensional stability of bamboo. The study used X-ray diffraction (XRD) and Fourier Transform Infrared (FTIR) to measure the crystallinity and chemical composition of bamboo pith ring and middle layer. The scanning electron microscopy and high-resolution computed tomography to observe the morphology of bamboo pith ring and parenchyma. The analysis showed a higher crystallinity and lignin content for the pith ring than the middle layer. In addition, the analysis revealed that the pith ring and the middle layer formed a criss-cross structure. The existence of the pith ring reduced the hygroscopicity and hygroscopicity hysteresis to a certain extent. In fact, the pith ring improved the dimensional stability of bamboo in radial and tangential directions, while it slightly reduced the dimensional stability in the longitudinal direction. These observations indicate that the pith ring was formed in bamboo during evolution to improve dimensional stability and to better adapt to complex environmental conditions. In the manufacture of bamboo products, the retention of pith ring can improve the utilization rate of bamboo and the dimensional stability of bamboo products.