Effects of Different Drying Methods on Bamboo's Physical and Mechanical Properties

In this work, a comparative study on microwave-vacuum-drying (MVD) and hot-air-drying (HAD) of bamboo culms was conducted. Related physical and mechanical properties of bamboo culms were investigated. MVD results showed no drying defects of bamboo culms. Compared with that of the HAD method, the drying time of MVD was reduced. The shrinkage of both bamboo culm diameter and wall thickness increased with drying time. The crystallinity was changed with drying time between MVD and HAD. The CIELAB color system (L*, a*, b*) was used for analyzing bamboo color changes. All the values of L*, a*, and b* were increased after MVD, which caused the bamboo culms to become golden yellow. However, after HAD, L*, a*, and b* decreased and samples became brown. The mechanical properties of samples were improved after MVD, and did not show any significant changes after HAD. The pore structure after MVD showed higher adsorption capacity, higher specific surface area, and greater volume compared with HAD. Therefore, taking into consideration the dried product quality and short drying time, MVD provides a potential method for drying bamboo.