Sustainable High-Performance Biocomposites Based on Wood Fibers and Self-Reinforced Micro-Fibrillated Cellulose Matrices

摘要

Given the decreasing availability of forest resources as a natural commodity, the efficient utilization of small-diameter shrubs is crucial for global sustainable development. This approach holds significant potential for conserving forest resources and reducing carbon emissions. However, small-diameter timber possesses inherent drawbacks such as its loose structure, susceptibility to cracking and deformation, and low strength, which considerably limit its range of applications. In this study, an efficient and eco‑friendly method was developed to prepare adhesive‑free biocomposites from discarded small‑diameter shrubs through ultrasonic pretreatment followed by thermoforming.After ultrasonic pretreatment, the flexural and tensile strengths of the biocomposites increased by 145 % and 132 %, respectively. The pretreatment disrupted the chemical bonds within the lignocellulosic biomass macromolecules via high‑speed shear and micro‑jet effects. This process significantly increased the number of binding sites on the cellulose fibers and further densified the cell walls during subsequent hot pressing. Moreover, the ultrasonic treatment removed certain components of the wood flour that act as fillers or density enhancers, leading to a slight reduction in the density of the resulting biocomposite. Simultaneously, lignin acted as an intrinsic binder, improving fiber bonding through both physical entanglement and chemical cross‑linking. As a result, a compact cellulose structure with a three‑dimensional lattice was formed, yielding a less hydrophilic surface as evidenced by a water contact angle of 81.72 °. Additionally, these high‑quality, binder‑free biocomposites emitted no harmful gases such as formaldehyde. Consequently, they are promising sustainable materials for future applications in building decoration and furniture manufacturing