Evaluation of Hydrophobicization of Cationic Cellulose Nanofibers Depending on the Type of Rosin Sizing Agents

Abstract

In this study, we evaluated the hydrophobicization of cationic cellulose nanofibers (CNFs) for different types of rosin sizing agents. Bleached hardwood kraft pulp was treated with microgrinding to prepare anionic CNF, and then cationic CNF was made from anionic CNF via a quaternization reaction. Thereafter, the particle size, fiber width, and zeta-potential of anionic and cationic CNFs were measured. The CNF films were prepared by adding rosin sizing agents to anionic and cationic CNF slurries. The contact angles of the CNF films for different rosin sizing agents and heat treatment were measured to evaluate the hydrophobicity of CNFs. The anionic and cationic CNFs were considerably nanosized showing no considerable difference in size, but the electrostatic properties were opposite to each other. Both the rosin sizing agents had a negative zeta-potential, and the fortified rosin sizing agent had a stronger anionic zeta-potential than gum rosin sizing agent. As the anionic and cationic CNF films containing rosin sizing agents were thermally cured, the contact angle of the CNF films increased and the cationic CNF film showed a higher contact angle than the anionic CNF film. Moreover, the fortified rosin sizing agent exhibited a higher contact angle of the cationic CNF film than the gum rosin sizing agent. In conclusion, the fortified rosin sizing agent was more effective in improving the hydrophobicity of the cationic CNF film than the gum rosin sizing agent.