Abstract:

Objective: In this study, the influence of polyvinyl alcohol/lithium aluminum hydrotalcite (PVA/LDH) dispersion on the physical and chemical properties of Balsa wood processing residues was investigated, which provided theoretical basis for constructing high performance wood - based composite materials, contributing to realize the high-value utilization of wood processing residues. Method: Inspired by the hierarchical“brick and mortar”structure of natural nacre, the Balsa wood processing residues (wood powders) were used as the main raw materials to obtain the 2,2,6,6-tetramethylpiperidine-1-oxylradi-cal (TEMPO)-functionalized wood powders (T-WP) through the delignification and oxidation modification process. Then, different proportions of PVA/LDH dispersion was added into the T-WP and a noval high-performance wood-based lamellar composites with natural organic polymers and inorganic nanosheets were assembled by intercalating inorganic LDH nanosheets through the vacuum filtration self-assembly process. What’s more, the FTIR, XPS, Zeta-potential and mechanical properties were tested and analyzed to investigate the interface interactions between the components and the synergistic enhancement mechanism of mechanical properties. Result: 1) When the particle size of wood powder was 100 mesh, the pure T-WP film showed optimal tensile strength of (225.25±0.82) MPa and toughness of (5.18±0.36) MJ·m^?3, respectively. 2) The PVA/LDH nanosheets were successfully intercalated on T-WP and formed hydrogen bonds, electrostatic interactions and covalent crosslinking with oxygen-containing functional groups on T-WP molecular chains. 3) The mechanical properties of T-WP-PVA/LDH films with different PVA/LDH contents were analyzed, which illustrated that the T-WP-PVA/LDH film reached the optimal mechanical properties with 20 wt% PVA/LDH, for example, the tensile strength and Young’s modulus reached up to (287.29±4.91) MP and (14.21±2.60) GPa, which were 1.28 and 2.40 times that of pure T-WP film, respectively. 4) Under the condition of 90% relative humidity and 25 ℃ for 16 h, the hygroscopic rate and the tensile strength of the as-prepared T-WP-PVA/LDH film were 45.43% and 105.40 MPa; in moist soil, the T-WP-PVA/LDH film exhibited excellent biodegradability. Conclusion: For T-WP-PVA/LDH bioinspired layered composites, the active oxygen-containing functional groups on T-WP molecular chains formed hydrogen bonding, electrostatic interactions and Al-O-C covalent cross-linking with PVA/LDH dispersion, establishing a synergetically reinforced biomaterials system, which remarkably enhanced the mechanical properties of T-WP-PVA/LDH films. Furthermore, these charming characteristics endowed the as-prepared wood-based layered composites with extensive application prospect in packings, mulching films and throw-away lunchboxs, which was expected to replace petroleum-based products such as polyethylene and polypropylene.

Key words: wood powders, TEMPO-mediated oxidation, lithium aluminum hydrotalcites, mechanical property, reinforcement mechanism, interfacial synergy