Hydrophobization of Cationic Cellulose Nanofiber Using Rosin Sizing Agent

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This study was conducted to explore a new method for imparting hydrophobicity to cellulose nanofiber (CNF) using a rosin sizing agent. Anionic CNF was made from hardwood bleached kraft pulp by micro-grinding; this anionic CNF was then used to prepare cationic CNF through quaternization. The hydrophobization of CNFs was performed by adding the rosin sizing agent to the anionic and cationic CNFs. The zeta-potentials of the CNFs were measured to identify the adsorption rate of rosin sizing agent in the CNFs. CNF films were made from anionic and cationic CNFs containing rosin-sizing agent. The contact angle, FT-IR spectra and burst strength of CNF films were analyzed after heat treatment was conducted to cure the rosin sizing agent.<BR>The zeta-potential of the cationic CNF decreased with the addition of the rosin sizing agent, however there was no significant change in the anionic CNF. After heat treatment of the films, the contact angle of the cationic CNF film was 95°, which was higher than that of anionic CNF film. These results indicated that the anionic rosin sizing agent adsorbed more on cationic CNF than on anionic CNF, and the FT-IR spectra showed the same trend. The burst strength of the CNF film showed the highest value at 3% of rosin sizing agent dosage. Therefore, it was concluded that the rosin sizing agent was effective for the hydrophobization of the cationic CNF and that the dosage should be less than 3% to simultaneously maintain the high contact angle and burst strength of the CNF film.