Mechanically robust and environmentally stable Al2O3/KH550 densified bamboo structural materials

Fast-growing bamboo composites with the delignification and densification fabricating processes have been widely applied for sustainable structural materials, but the environmentally stability still hinders its further development. Here, we demonstrate a robust and environmental stable modified densified bamboo composites consisting of hierarchical Al2O3 nanoparticles and organic coupling agent γ-Aminopropyl triethoxysilane (KH550) layer. KH550 densified bamboo exhibits superb tensile strength and flexural strength of 462 MPa and 364 MPa, which are, respectively, 237% and 198% higher than those of natural bamboo. Flexible molecular chains of KH550 decorate cellulose with silane groups and amino groups, the thermal decomposition temperature significantly delays ∼80 ℃ and hydrophilic densified bamboo turns hydrophobic with the contact angle of ∼112°. The obtained Al2O3 densified bamboo however shows rough and porous defects, and only exhibits slight increase in tensile properties, but decreases on flexural and thermal properties. Real-time acoustic emission also reveals that the introduction of coupling agent enhances the load delivery between fibers and parenchyma cells, leading to high energy consumption and fracture resistance. This work shows the complex effects of organic and inorganic modification designs for bamboo materials, which might arouse potential application prospects for environmentally stable, sustainable robust structural biomass composites.