Electrostatic Adsorption-Reinforced Carboxymethylated Cellulose Nanofiber-Lignin Sustainable Bioplastic for UV-Blocking and Water-Stable Packaging Materials

Petroleum-based plastic packaging products cause a great deal of environmental pollution and are potentially harmful to humans. Therefore, preparing biomass-based plastic products that are biodegradable and environmentally friendly has become an important alternative. Cellulose, as an important renewable biomass raw material, can be used to prepare a variety of bioplastics; however, they also have inherent problems such as poor water resistance and single functionality. Attempts have been made by adding lignin to cellulose, but the charge repulsion can induce lignin aggregation, ultimately leading to poor optical properties and reduced mechanical strength of bioplastics. In this study, a high-performance composite bioplastic composed of cation-modified nanocellulose and negatively charged lignin molecules was developed based on electrostatic adsorption and hot-pressing techniques. The structural design strategy of nanocellulose as the “framework” and lignin as the “adhesive” endowed the composite bioplastic with high tensile strength (>100 MPa), long-term water stability (6 months), tunable light transmission, and excellent ultraviolet (UV)-blocking properties (>99%). Additionally, the resulting bioplastic has superior comprehensive performance than commercial petroleum-based plastics and common cellulose-based films, and the concept confirms that our bioplastic can be used in food packaging materials.