Moisture diffusion properties of graded hierarchical structure of bamboo: Longitudinal and radial variations

Abstract

Determination of moisture diffusion properties of bamboo is necessary to evaluate its growth and development and optimize the manufacturing process of associated products as well. The moisture sorption and diffusion characteristics of bamboo in different locations were tested. Graded hierarchical structure in both longitudinal and radial directions influenced the moisture transportation efficiency of bamboo significantly. Quicker moisture diffusion was found at higher heights or outer radial positions. The high moisture diffusion coefficient (D) could be explained by the increment of the vessel fraction, or the large size of vessel lumen. D logarithmically increased with the increment of moisture content (MC) irrespective of height or radial position. By simplifying the hierarchical structured system of bamboo, moisture-activated diffusion processes in cell wall (DBW) and lumen (DV) were simulated. Calculated values of D, DBW and DV could be used to predict the changes of moisture transport in bamboo, regardless of its graded structure (i.e., location) or MC. Overall, the results of this study elucidated the longitudinal and radial variations of moisture diffusion, exploring possible adaptation strategies during the growth process of bamboo. These findings may also be relevant for the optimization of the manufacturing technology of bamboo-based products.