Integrated Production of Cellulose Nanofibers and Sodium Carboxymethylcellulose through Controllable Eco-carboxymethylation under Mild Conditions

In the past few decades, the preparation of cellulose nanofibers (CNF) has been restricting its application in industrialization. A fast and green preparation method is urgently needed to promote the industrialization process. In this paper, eco-carboxymethylation of cellulose was first used to enable the carboxymethylation of eucalyptus wood dissolving pulp (EWDP) and then we introduced a new idea of isopropanol alcohol (IPA) washing followed by drying to disintegrate chemical modified fibers into dried nanometer-sized cellulose powders. The cellulose powders were transferred into CNF with a width of 18 nm and length of several hundred nanometers after high-pressure homogenization. The powder form of cellulose provided more chances for fibrillation which resulted in low energy consumption and high yield of CNF. The obtained CNF were employed to prepare nanopaper and conductive nanopaper by vacuum filtration. The fabricated nanopaper exhibited a high optical transmittance of 92% with a maximum tensile stress of 107.5 MPa. However, the optical transmittance of conductive nanopaper slowly decreased to 68% when the square resistance reached 18 Ω/sq. This novel route for preparing CNF was low toxicity, environmentally friendly and solved the blocking of the high-pressure homogenization process. The fabricated transparent flexible conductive nanopaper with smooth surface, high transmittance, high strength and good conductivity has great potential in the field of optoelectronics.