Artificial simulated aging of bamboo slips and its degradation mechanism

Abstract

Bamboo slips record the development of Chinese civilization and are crucial for historical and cultural research. Due to the long-term erosion by groundwater during burial, most of them were waterlogged. The sudden change in the environment after excavation poses risks such as cracking, peeling, and deformation to these bamboo slips. However, there is a lack of effective real bamboo slips for systematic research on dehydration, shaping, protection, and restoration. Therefore, the preparation of artificially simulated aged bamboo slips has important practical significance. In this study, artificial simulation aging of bamboo slips was carried out using water bath method and hydrothermal method in NaOH solution, respectively. The effects of water bath treatment time and concentration of hydrothermal NaOH solution on the moisture content, structure, morphology, chemical composition and physical properties of the simulated bamboo slip samples were thoroughly studied, and the degradation mechanism was elucidated. The results show that the maximum moisture content of artificially degraded simulated bamboo slips could be controlled between 200 and 650 %, and the samples were soft and sponge-like, which was in line with the characteristics of the saturated bamboo slips as reported before. NaOH solution could promote the preferential degradation of hemicellulose and lignin, as well as partial degradation of amorphous cellulose, which was especially accelerated by the hydrothermal method. With the extension of water bath time, the maximum moisture content of the simulated sample changed slightly (maintaining ∼ 200 %), but the strength and hardness decreased obviously. In contrast, for the hydrothermal method with high temperature and high pressure conditions, the dense structure of bamboo surface was destroyed. With the increase of NaOH concentration, the chemical reaction rate increased, and the degradation degree of hemicellulose, lignin, and cellulose increased, leading to the collapse of thin-walled and fibrous tissues. The porosity and moisture content of the sample increased, reaching a maximum of 594.70 ± 32.01 %, and the mechanical properties decreased sharply. This method provides an important reference for the simulation preparation of bamboo slips with different moisture contents, laying the foundation for subsequent research on reinforcement materials and evaluation systems of bamboo cultural relics.