RESUMEN
In this study, all-cellulose nanocomposite (ACNC) was successfully prepared through a green and sustainable approach by using corn stalk as raw material, water as regeneration solvent, and recyclable two-component ionic liquid/DMSO as the solvent to dissolve cellulose. The morphology and structural properties of ACNC were determined by scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction analysis, indicating homogeneity and good crystallinity. In addition, a comprehensive characterization of ACNC showed that CNF not only improved the thermal stability and mechanical characteristics of ACNC, but also significantly improved the oxygen barrier performance. The ACNC prepared in this work has a good appearance, smooth surface, and good optical transparency, which provides a potential application prospect for converting cellulose wastes such as corn straws into biodegradable packaging materials and electronic device encapsulation materials.
RESUMEN
An electrolyte and aprotic solvent mixture were used to prepare cellulose solutions containing cellulose nanocrystals (CNCs). All-cellulose composite fibers were then produced by dry-wet spinning these solutions. The presence of CNC in the all-cellulose fibers was demonstrated, and the effects of the CNC on the fiber properties were investigated. The all-cellulose fibers were characterized by scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis, and electronic tensile measurements. These results showed that CNCs were present in the mixture and that their structure was maintained in the all-cellulose fibers. No compatibility problems between the CNC and cellulose II matrix were observed. Introducing CNC enhanced the crystallinity, thermal stability, and mechanical properties of the composite fibers.
RESUMEN
Microcrystalline cellulose grafted polycaprolactone (MCC-g-PCL) was successfully synthesized by ring-opening copolymerization catalyzed by 4-dimethylaminopyridine in a dual tetrabutylammonium acetate/dimethyl sulfoxide solvent system. A novel ultraviolet-shielding film based on MCC-g-PCL was prepared by introducing graphene oxide (GO). The results obtained showed that the introduction of GO not only obviously influenced the inherent structure of the MCC-g-PCL but remarkably changed the surface morphology of the composite film. Moreover, the GO/MCC-g-PCL composite showed a significant improvement in tensile strength, from 2.63 to 4.55 MPa, as well as elongation-at-break, from 6.4% to 15.5%, compared with the pure MCC-g-PCL film, owing to the strong hydrogen-bonding interaction that physically crosslinked GO with MCC-g-PCL. Importantly, GO/MCC-g-PCL composite films offered an effective high-energy light-shielding capacity; in particular MCC-g-PCL film containing 1.0 wt% GO possessed good absorbance between 200 nm and 300 nm. This study provides a framework for developing cellulose-based ultraviolet-shielding polymers and better understanding the ultraviolet-shielding mechanism.
RESUMEN
This work determined that southern yellow pine wood can almost be completely dissolved in the quaternary ammonium ionic liquid tetrabutylammonium acetate with dimethyl sulfoxide (in a 2:8 mass ratio), after minimal grinding, upon heating at 85 °C for three dissolution/reconstitution cycles, each 1.5 h. Approximately 34.6% of the native lignin and 67.4% of the native carbohydrates present in the original wood can subsequently be extracted, respectively, and were assessed. A gradual decrease in lignin with increased extraction cycles resulted in increased crystallinity index of the cellulose II in the cellulose-rich residue, as confirmed by X-ray diffraction. An increasingly homogeneous macrostructure in the cellulose-rich residue was also evident from scanning electron microscopy images. Membranes cast directly from either wood or cellulose-rich residue solutions in the same tetrabutylammonium acetate/dimethyl sulfoxide system, were prepared using a papermaking-like process. Morphological and mechanical studies indicated that lignin extraction made the membranes more uniform and flexible. Systematic increases in the fibril lengths and orientations of the recovered materials were also found with decreasing lignin contents on the basis of atomic force microscopy analysis. This work demonstrates that relatively efficient partial separation of pine wood and subsequent membrane preparation are possible using a quaternary ammonium ionic liquid.
