Fabrication And Properties Of Nanocellulose-based Functional Films

Due to its excellent properties of high aspect ratio, high crystallinity, high mechanical strength, renewable, bio-degradation and biocompatibility, nanocellulose(NC) is a promising substitute for petroleum based polymers in transparent film, food preservation, flexible electronics and some other fields. Therefore, NC and its composite materials is still a reseach focus at home and abroad. However, surface groups and morphology controlling are of great important factors for NC to combine with functional materials to form newly multi-functional NC-based composites. Herein, bamboo fiber as the raw material was used to prepare NC via the chemo-mechnical procedure, NC was handled with surface hydroxyl oxidation treatment, conbining with nanostructure ZnO and carbon dots to make the transparent multi-functional hybrid films.1) Bamboo was employed as the raw material by using acid treatment and high pressure homogenization to make 1D nanocellulose. The s-ZnO and b-ZnO conjoined with the NC fibrils to form NC-ZnO hybrid film via a pressure controlled extrusion process. When the addition of Zn O comes to 3wt%, the hybrid film contains both high transmittance and excellent UV-blocking properties. As the addition of s-ZnO comes to 6wt%, the transmittance of NC-s-ZnO hybrid film up to 97.79% and 99.13% at 300 nm, 225 nm, respectively, which is much higher than the same condition of NC-b-ZnO hybrid film.2) The primary hydroxyls of nanocellulse are converted to the carboxyl form by using TEMPO-mediated oxidation to make ONC. Microwave procedure is used to get fluorescence carbon dots derived from ONC. CDs combine ONC to assemble CDs-ONC through covalent bonding. The pressure controlled extrusion process is employed to obtain CDs-ONC hybrid film. The resultant nanocellulose based hybrid film has high transparency in bright field and strong blue luminescence under UV excitation. Moreover, the biocompatible hybrid film extracted from biomass exhibits excellent thermal stability and outstanding mechanical durability. The PL intensity of CDs-ONC film decreases 5% after bending for 2000 times.3) CDs-ONC-ZnO hybrid film for UV-blocking was assembled according to TEMPO-mediated oxidized nanocellulose and its derivatives of carbon dots incorporating with ZnO nanostructures via a pressure controlled extrusion process. The new obtained CDs-ONC-ZnO hybrid films presented a sharp increase of UV-blocking properties than the previous reported NC-ZnO hybrid films. When the addition amount of ZnO reaches to 4wt%, the UV-blocking Ratio(UVR) of CDs-ONC-ZnO hybrid film gets to nearly the same results compared to NC-ZnO hybrid film of 6wt% of ZnO added amount. The CDs-ONC-s-ZnO hybrid film could block over 90% of UV at 300 nm and 225 nm, better than the same condition of CDs-ONC-b-ZnO and CDs-ONC-p-ZnO(ZnO particles, p-ZnO) hybrid films.