Characteristics of regenerated nanocellulosic fibers from cellulose dissolution in aqueous solutions for wood fiber/polypropylene composites
The effects of aqueous solutions were evaluated on the properties of regenerated cellulosic nanofibers prepared from pure cellulose fibers in various formulations of aqueous solutions. Thermoplastic composites were prepared with reinforcement of the regenerated cellulosic nanofibers. The regenerated cellulosic fibers from cellulosic woody biomass were obtained from dissolved cellulose solutions by coagulating with sulfuric acid and water for phase separation. The properties of the regenerated cellulosic fibers were characterized using Fourier-transform infrared spectroscopy (FTIR), wide angle X-ray diffraction (WAXRD), thermogravimetric analysis (TGA), field emission scanning electron microscopy, and tensile testing. The TGA, WAXRD, and FTIR spectra indicated that the regenerated nanofibers possessed cellulosic crystal type II. The micrographs of regenerated cellulosic fibers showed a dense composite structure and lower crystallinity than controlled fibers. The tensile strength of regenerated cellulosic fiber-reinforced polymer composites reached 30 MPa, which was 70% higher than the control fiber-reinforced composites. The composites prepared from regenerated fibers with sodium hydroxide (NaOH)/urea and NaOH/urea/thiourea aqueous solutions provided the best results. This work also provides a potential promising method to efficiently obtain nanocellulosic fibers as reinforcement materials in bio-based nanocomposites.