Development of all-cellulose sustainable composites from directionally aligned bamboo fiber scaffold with high strength, toughness, and low thermal conductivity

Based on a unique "concrete-steel bar" structure, directionally aligned bamboo fibers have been introduced into cellulose acetate as a scaffold to improve their mechanical properties. Here, we present a simple approach for preparing all-cellulose composites by using an innovative "crosslinking pretreatment-steam delignification" and cellulose-acetate deacetylation procedure. The chemical crosslinking introduced in this strategy can effectively preserve the completeness of raw bamboo, thus providing an effective framework for cellulose acetate infiltration. Through physical crosslinking, cellulose acetate improved the load distribution of the bamboo fibers, and densification from heat compression resulted in a strong fiber-volume fraction with intensive hydrogen bonding between nearby bamboo fibers. This approach endowed regenerated cellulose-delignified bamboo (RC-DB) composites with enhanced mechanical performance. The composite had a specific strength of 813.86 MPa g−1 cm3, which was superior to those of many other building composites. RC-DB exhibited a tensile strength of 1098.71 MPa and tensile modulus of 36.52 GPa, which were 6.87 and 4.53 times larger than those of natural bamboo, respectively. The toughness achieved was 25.61 MJ m−3. The RC-DB composite displayed a low thermal conductivity of 0.08 W m−1 K−1, resulting in exceptional thermal-insulation performance. Furthermore, this study demonstrated the viability of preparing large RC-DB composites. The high mechanical strength, excellent thermal management, biodegradability, and production scalability make RC-DB composites suitable for basic engineering applications.