Hydrophobicity of alkyl ketene dimer-modified microfibrillated cellulose film

Microfibrillated cellulose (MFC) is a promising bio-based material owing to its excellent mechanical, optical, and barrier properties. However, its inherent hydrophilicity limits its applicability in moisture-sensitive environments. In this study, the surface hydrophobicity of MFC films was enhanced by incorporating an alkyl ketene dimer (AKD) and thermal curing. MFC was prepared from hardwood bleached kraft pulp via high-pressure homogenization to fabricate AKD-modified MFC films using vacuum filtration. The water contact angles of the AKD-modified MFC films were measured after thermal curing to determine the optimum manufacturing conditions for MFC film hydrophobicity. The presence of the AKD in the MFC matrix was confirmed by the appearance of alkyl chain C–H stretching bands in the Fourier transform infrared spectroscopy spectra. The water contact angle measurements showed that the addition of AKD alone improved the hydrophobicity but did not yield contact angles greater than 90°. However, with subsequent thermal curing at 105 °C, the contact angles increased significantly, reaching 104° under optimal conditions. The highest hydrophilicities were achieved with 2% AKD and 30 min curing and with 3% AKD and 10 min curing. These findings demonstrated that thermal curing was essential for activating the hydrophobic potential of AKD and achieving uniform, water-repellent MFC films.