Observing bamboo dimensional change caused by humidity

Abstract

Bamboo is a kind of natural biomaterials sensitive to moisture. The change of moisture content in bamboo leads to the cracking and deformation of bamboo. To understand the mechanism of swelling due to moisture change, the swellings were measured on bamboo blocks as well as separated fiber and parenchyma tissue under different humidity conditions in situ by using a dynamic vapor sorption (DVS) instrument and a charge-coupled device (CCD) camera. The results showed that when the relative humidity (RH) was above 40%, the main types of moisture in the bamboo blocks changed, and the area swelling of the bamboo blocks increased rapidly. When equilibrium moisture content (EMC) was 11.91%, the area swellings of the fibers (BF) and the vascular bundles (BV) in the bamboo blocks, and the bamboo blocks were 42.00%, 25.69%, and 4.26%, respectively. The content of the bamboo fiber plays a decisive role in bamboo swelling. For the separated fibers and parenchymal cells, when RH changed from 0% to 90%, the transverse swellings of the fibers and parenchymal cells were 7.24% and 2.22%, respectively. The longitudinal swellings of the fibers and parenchymal cells were 0.62% and 1.24%, respectively. The fibers had a higher transverse swelling rate than that of the parenchyma cells.