Preparation and Characteristics of High-Performance TEMPO-Functionalized Wood Powder-Polyvinyl Alcohol/Lithium Aluminum Hydrotalcite Composites
[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.
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