Cellulose nanofibers has unique properties such as high mechanical property and specific surface area, good thermal property, biodedradability, and biocompatibility. Therefore, it has been recognized as potential material for various applications. To wide its application, the compatibility with hydrophobic materials should be given to cellulose nanofibers. Chemical modification of cellulose nanofibers such as hydrophobization has been studied by various processes. Hydrophobization has been done to overcome the drawbacks originated from numerous hydroxyl groups on the surface of CNF. Among various hydrophobization processes, silylation that substitutes hydroxyl groups with silyl groups was focused in this study. Silylation by a sol-gel method allows to minimize use of organic solvents. In this study, cellulose nanofibrils (CNF) was silylated using methyltrimethoxysilane (MTMS) in aqueous system at different pH conditions. The hydrophobization was evaluated by water contact angle of the film made of the hydrophobized CNF. Fourier transform infrared (FT-IR) and X-ray photoelectron spectroscopy (XPS) analyses were carried out to investigate the characteristics of the silylated CNF films. The CNF films silylated at acidic and mild alkaline conditions showed the highest water contact angles, which was about 120 degree. When CNF was silylated in alkaline conditions, the films contained particles of self-condensated poylsiloxane structure which can deteriorate hydrophobicity. Therefore, a proper pH condition could be suggested to give high hydrophobicity to CNF.

Hydrophobization of cellulose nanofibers through silylation at different pH conditions of aquous system

2019 Spring National Meeting

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