Fabrication and characterization of flexible natural cellulosic fiber composites through collaborative modification strategy of sodium hydroxide and γ-Aminopropyl triethoxysilane.

The primary purpose of this work is to study the fabrication of a flexible natural cellulosic fiber composite. In this respect, natural cellulosic fiber was obtained by modified poplar wood fiber through sodium hydroxide (NaOH) and γ-Aminopropyl Triethoxysilan. Then, the composites were fabricated by hot-pressing the modified wood fibers and polyurethane following characterization. Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and scanning electron microscope (SEM) observation results confirmed that some of the hemicellulose and lignin were removed from wood fibers after NaOH modification and successfully grafted with alkoxy structures after KH550 modification. NaOH&KH550 modification improved the interfacial compatibility between poplar wood fibers and polyurethane. The flexibility of the composites was improved (the slenderness value was reduced by 113 %), allowing flexible deformations such as bending, twisting, and knotting. In addition, thermal stability, tensile strength (increased by 105 %), elongation at the break (increased by 125 %), and water resistance were increased. This flexible natural cellulosic fiber composite is expected to be applied in the veneering of curved materials and special-shaped structure furniture, providing a theoretical basis for improving the added value of wood-based composites.

Enhancing interfacial interaction and crystallization in polylactic acid-based biocomposites via synergistic effect of wood fiber and self-assembly nucleating agent.

Incorporation of natural fibers into polylactic acid (PLA) provides a feasible pathway to improve the performance of PLA with a low environmental impact. However, the insufficient interfacial adhesion between fiber and matrix limits the reinforcement efficiency of fiber and final mechanical properties of the biocomposites. Herein we reported an efficient method to simultaneously enhance interfacial interaction, crystallization and mechanical performance of PLA-based biocomposites via combination of wood fiber (WF) and a self-assembly nucleating agent (TMC-300). The interactions between WF and TMC-300 and its influence on PLA, including interfacial crystal morphology, crystallization behavior, and mechanical performance were studied. The results showed that TMC-300 could self-assemble into dendritic-like structure on WF surface driven by hydrogen bonding, inducing the epitaxial crystallization of PLA. This unique interfacial crystallization integrated PLA matrix with WF, resulting in better interfacial adhesion. Under the optimal TMC-300 content (0.5 wt%), the flexural strength and notched impact strength of PLA composites increased by 10 % and 69 % compared with neat PLA, respectively. Additionally, TMC-300 and WF synergistically functioned as effective nucleating agents, which significantly accelerated the crystallization rate and improved the crystallinity of PLA. This work provides a new insight into the enhancement of interfacial bonding in natural fiber/PLA biocomposites.

Enhancing Crystallization and Toughness of Wood Flour/Polypropylene Composites via Matrix Crystalline Modification: A Comparative Study of Two ß-Nucleating Agents.

Incorporation of short wood fillers such as wood flour (WF) into polypropylene (PP) often results in a marked reduction of toughness, which is one of the main shortcomings for WF/PP composites. This research reports a facile approach to achieve toughening of WF/PP composites via introducing self-assembling ß-nucleating agents into PP matrix. The effect of two kinds of nucleating agents, an aryl amide derivative (TMB5) and a rare earth complex (WBG II), at varying concentrations on the crystallization and mechanical properties of WF/PP composites was comparatively investigated. The results showed that both nucleating agents were highly effective in inducing ß-crystal for WF/PP, with ß-crystal content (kß) value reaching 0.8 at 0.05 wt% nucleating agent concentration. The incorporation of TMB or WBG significantly decreased the spherulite size, increased the crystallization temperature and accelerated the crystallization process of WF/PP. As a result of PP crystalline modification, the toughness of composites was significantly improved. Through introducing 0.3 wt% TMB or WBG, the notched impact strength and strain at break of WF/PP increased by approximately 28% and 40%, respectively. Comparatively, although WF/PP-WBG had slightly higher Kß value than WF/PP-TMB at the same concentration, WF/PP/TMB exhibited more uniform crystalline morphology with smaller spherulites. Furthermore, the tensile strength and modulus of WF/PP-TMB were higher than WF/PP-WBG. This matrix crystalline modification strategy provides a promising route to prepare wood filler/thermoplastic composites with improved toughness and accelerated crystallization.