Mechanism analysis of thermal treatment for the mechanical properties of bamboo veneer composites from the perspective of cellulose skeleton

High-performance bamboo veneer composite (BVC) is a typical application to achieve high efficiency of bamboo for sustainable engineering. As the important pretreatment during the manufacture process of BVC to improve dimensional stability and weather resistance, thermal treatment would weaken mechanical properties, whose influence mechanism has not been determined. Herein, we mainly focus on the main bearing substance of BVC- bamboo cellulosic fibers (BCFs), to expound the inherent interrelationship between macro-mechanical properties of BVC and microstructure of BCFs by studying their micro-mechanical properties, crystal structure, hydrogen bonding system, chemical structure and degree of polymerization (DP) under thermal treatment (140 °C and 200 °C). With the temperature increased, the diameter and orientation of BCFs basically remained unchanged, the crystallinity increases slightly, but the DP of BCFs decreased, causing the decrease of microscopic tensile properties of BCFs. Macro-mechanical properties of BVC are positively correlated with the micro-mechanical properties of BCFs.