Cellulose nanofiber assisted dispersion of hydrophobic SiO2 nanoparticles in water and its superhydrophobic coating

It is challenging to build a superhydrophobic coating with aqueous dispersions since hydrophobic substances are usually dispersed in pure organic or water/organic mixed solvents. In this study, hydrophobic SiO2 nanoparticles were dispersed in water assisted with cellulose nanofiber (CNF) and the superhydrophobic surface was manufactured by coating a waterborne dispersion composed of CNF, hydrophobic SiO2 nanoparticles and methyltrimethoxysilane (MTMS). It was found that the dispersion of SiO2 in water can be improved by CNF. Meanwhile, the coated paper surface retained its hydrophobicity after 10 abrasion cycles due to the adhesion of the coating surface promoted by MTMS. When SiO2 content over 0.25 wt%, the coated paper surface displayed a superhydrophobic property, and the moisture absorption decreased to 31-34%. The contact angle of the coating surface was 162 degrees, the contact angle hysteresis was 1.96 degrees and the rolling contact angle was 1.33 degrees when SiO2 content was 1 wt%.