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It is a formidable challenge in thermoplastic/lignin composites to simultaneously boost tensile strength and elongation performance due to the rigidity of lignin. To address this issue, sodium-alginate-doped lignin nanoparticles (SLNPs) were prepared by combining solvent exchange and a coprecipitation method and used as an eco-friendly filler for poly(butylene adipate-co-terephthalate) (PBAT). The results indicated that the 1% polyanionic sodium alginate solution contributed to the formation of SLNP in lignin/THF solution. SLNP with a mean hydrodynamic diameter of ~500 nm and a Zeta potential value of −19.2 mV was obtained, indicating more hydrophobic lignin nanoparticles and a smaller number of agglomerates in SLNP suspension. Only 0.5 wt% SLNP addition improved the yield strength, tensile strength, and elongation at break by 32.4%, 31.8%, and 35.1% of the PBAT/SLNP composite films, respectively. The reinforcing effect resulted from the rigid aromatic structure of SLNP, whereas the enhanced elongation was attributed to the nanostructural feature of SLNP, which may promote boundary cracking. Additionally, the PBAT/SLNP composite films displayed excellent ultraviolet (UV) resistance with a UV shielding percentage near 100% for UVB and more than 75% for UVA, respectively. The addition of SLNP hindered water vapor, enhancing the moisture barrier properties. Overall, this study provides an effective strategy to eliminate the decrement in elongation performance for PBAT/lignin composites and suggest they are good candidates to be extensively utilized.

A compound aircraft with a collectible rotor has the ability of vertical take-off and landing (VTOL), high-speed flight and long-range cruising. Compared to systems in other compound aircraft, the collectible rotor can work as a conventional rotor in helicopter mode and can be gathered into a disk in the center in fixed-wing mode, thereby relieving the rotor's limitations pertaining to forward flight performance. The collectible rotor is a key component in the design and realization of a compound aircraft. Based on a 35-kg-level prototype, in this study, the principle of a folding rotor is proposed, a dynamic model of the rotor is established considering the complex nonlinear compound motion of rotation and folding, and the aerodynamic and dynamic characteristics are analyzed considering the coupling of different speeds of the rotor and folding strategies for the folding process. According to the above research, a complete rotor system, including an unconventional rotor structure, closed-loop real-time control system, and high-torque driving system, is designed. A demonstration model was constructed to verify the feasibility of the folding rotor. Finally, through an on-board test, the folding rotor system was verified in a simulated real flight state. This paper provides a theoretical basis for folding rotor design and proposes a set of design methods and research concepts. [ABSTRACT FROM AUTHOR]