Bamboo–Alginate Composite as a Sustainable Structural Material

In the current context of environmental concern and energy crisis, wood-based composites are attracting attention as sustainable materials; however, their mechanical properties require improvement. Herein, we report a novel method for the preparation of bamboo composites with excellent mechanical properties and formability. After delignification of bamboo, an alginate solution was filled into the voids of delignified bamboo (DB) under reduced pressure to obtain alginate-impregnated DB (ADB). Then, the alginate was subjected successively to ionic and chemical cross-linking by adding CaCl2 and glutaraldehyde, respectively. The mechanical strength of the resulting dually cross-linked ADB (DCB) was improved by removing unfilled voids via a hot-press forming process. The tensile and flexural strengths of the hot-pressed DCB (HP-DCB) showed the highest values ever reported for wood composites, i.e., 1.12 GPa and 678 MPa, respectively, which can be attributed to the strong adhesion and effective load transfer stemming from the dual cross-linking of alginate between the bamboo fibers. In particular, the presence of flexible and adhesive alginate enabled the reshaping of HP-DCB into desired shapes through rehydration and molding, demonstrating its potential for various applications requiring ecofriendly, high-strength, and lightweight materials.