Bio-based films with high antioxidant and improved water-resistant properties from cellulose nanofibres and lignin...

In this study, we propose a simple route for the fabrication of bio-based composite films from cellulose nanofibres (CNF) and lignin. First, CNFs were periodate oxidised to obtain dialdehyde cellulose nanofibres (DACNF). Subsequently, lignin nanoparticles (LNPs) with diameters between 50 and 150 nm were prepared using kraft lignin and mixed with DACNF to fabricate DACNF-LNP nanocomposite films via a condensation reaction. The addition of LNPs rendered the films with high ultraviolet-shielding and antioxidant properties. The water contact angle increased for the composite films compared with that of pure CNF film, while the water vapor transmission rate (WVTR) decreased. The mechanical properties of the nanocomposite films were significantly improved by the addition of LNPs. The dry tensile stress of DACNF-LNPs5 with 5 % LNPs significantly increased from 47 to 164 MPa. It was also higher than that of CNF-LNPs5 (105 MPa), in which CNFs were not periodate oxidised. After immersion in water for 1 h, the wet tensile strength of DACNF-LNPs5 was 31 MPa, 3 times higher than that of CNF-LNPs5 (7 MPa). These results indicate that the water-resistant properties of the composite films were significantly enhanced. The films prepared from green and renewable bioresources exhibited potential applications in food packaging and biomedical materials.