Super-strong and flexible wood through cell wall swelling-assisted spontaneously fibers aggregation

Abstract

Abstract The highly oriented cellulose microfibrils in secondary cell wall provide a unique advantage for developing super-strength wood. Here, we developed a two-tiered dynamic strategy that realized the self-densified wood by adequate swelling and moisture evaporation process without further hot pressing or via chemical oxidation pre-treatment. Our method requires only exposing delignified wood to a poor solvent that is able to infiltrate the cellulose skeleton without molecular-level dissolution, thus facilitating the effective penetration of moisture upon water replacement. The following natural moisture evaporation triggers self-aggregation of cellulose fibrils accompanying with dynamic re-formation of hydrogen bonds, thereby leading to a super-high mechanical strength (tensile strength: 596.24 ± 57.01 MPa, toughness: 10.43 ± 2.07 MJ m−3, and flexural strength: 418.51 ± 23.86 MPa (balsa wood), 296.52 ± 10.41 MPa (pine wood)) to the resulting self-densified wood. More importantly, the swollen wood has the hydroplastic processing ability (using air-drying to design the shapes). The “cold” processing method satisfies the self-densification for various species of wood, providing a general strengthening strategy.