Curling behavior and mechanism of bamboo inner slivers induced by delignification treatment

Abstract Bamboo inner materials are often discarded due to their loose tissue structure and low mechanical strength. Delignification can effectively enhance material performance. To improve mechanical properties and increase utilization, this study respectively treated bamboo inner slivers with delignification using sodium hydroxide and acidified sodium chlorite solutions. After drying, the chemically treated bamboo inner slivers showed improved bending properties and tensile strength compared to untreated ones. In addition, the three types of slivers exhibited distinct curling behaviors: untreated slivers curled most longitudinally, sodium hydroxide-treated bamboo slivers showed the most pronounced curling in the transverse direction; the longitudinal bending curvature of slivers treated with acidified sodium chlorite fell between the two extremes, while transverse curling was minimal. Results indicated that the 5 wt% sodium hydroxide treatment removed lignin more effectively than the 4 wt% acidified sodium chlorite solution. Sodium hydroxide treatment caused collapse of parenchyma and pith ring cells, whereas acidified sodium chlorite largely preserved cellular structure. Therefore, the density and strength of bamboo slivers treated with sodium hydroxide show more significant improvement. The differences in curling behavior are closely associated with the extent of bamboo inner sliver lignin and hemicellulose removal and the corresponding microstructural changes.