Recently, cellulose nanofibril (CNF) has emerged as a promising, sustainable reinforcement with outstanding potential in material science. Owing to the properties of CNF, it has been explored in food, cosmetic, and pharmaceutical applications, as well as in industrial applications such as paints, drill muds, packaging, and papermaking. The application of CNF in papermaking is expected to be implemented in the near future to broaden the commercial market of cellulose. Numerous studies and patents have reported on the manufacturing, properties, and applications of nanocellulose. This present paper focuses on the recent progresses in the application of CNF as a wet-end additive in papermaking.

In this study, carboxymethylation, which introduces carboxyl groups to hydroxyl sites in pulp fibers, was used as a pretreatment before mechanical nanofibrillation.The carboxyl group content of the pulp fibers was greatly affected by the dosage of chloroacetic acid and the reaction temperature.During the following fibrillation process, it was found that pulp fibers with higher carboxyl group content exhibited higher water holding capacities and smaller dimensions.A more homogenous structure with a higher amount of individual fibrils was also observed in FE-SEM images of pulp fibers with high carboxyl group content.This can be explained by a high ionic group content in the fiber wall resulting in lower delamination resistance, making the fibrils easier to separate.Carboxymethylation pretreatment as a facilitator of fibrillation in cellulosic pulps is an efficient way to obtain cellulose nanofibrils and consequently decrease the energy consumption of the process.