High-strength, lightweight and sustainable lignin contained cellulose nanofiber bulk materials for plastic replacement

As we all know, although petroleum-based plastic products greatly facilitated our life, they also caused great negative impacts on the environment and human health. In recent decades, cellulose nanofibers (CNFs) exhibit good degradability, renewability, and excellent mechanical properties, which is expected as a potential substitute for traditional petroleum-based plastic. Herein, we reported a facile preparation strategy of CNF dry powder based on TEMPO-oxidation process as well as the construction method of CNF-lignin bulk material which exhibited higher mechanical strength than most plastics. Among them, CNF-lignin bulk material containing 5% lignin performed excellent flexural strength (~198 MPa), which is much higher than that of most commercial plastics. Other important properties of this material such as super lightweight (~1.35 g/cm 3 ), good toughness (~8.5 kJ/cm 2 ), and high thermal stability (~295 °C) are also capable of meeting the requirements of replacing plastics. The mechanism investigation of lignin adding for improving the mechanical properties of CNF-lignin composite testified that the lignin in CNF-lignin composite filled the voids among CNFs and no chemical reactions happened between lignin and CNFs. Overall, this work offers a strategy to fabricate an environmentally friendly CNF-lignin bulk material, which is a promising alternative to petroleum-based plastics. • Dispersible CNF dry powder can be prepared from CNF suspension by solvent replacement and rotary evaporation. • CNF-lignin bulk material is prepared by mixing and drying CNF dry powder, lignin and water. • Lignin can improve the properties of CNF bulk materials which expected to be a substitute for petroleum-based plastics.