Preparation of Hydrophobized Microfibrillated Cellulose Powder by Alkyl Ketene Dimer Treatment and Spray Drying

Abstract

Microfibrillated cellulose (MFC) is a sustainable, bio-based material with remarkable mechanical properties and a large specific surface area. However, its inherent hydrophilicity limits its application in hydrophobic composite systems. In this study, hydrophobized MFC powders were prepared by treating MFC suspensions with alkyl ketene dimer (AKD) and then spray-drying. The MFC suspensions were treated with varying AKD dosages (1 to 3%, based on oven-dried MFC) and spray-dried at different inlet temperatures to determine the best hydrophobization conditions. Contact angle measurements indicated that hydrophobicity increased with rising AKD dosage, and the maximum contact angle was obtained at an inlet temperature of 120 °C. Fourier transform infrared analysis supported the retention of AKD-derived hydrophobic alkyl groups in the spray-dried MFC powders. Field-emission scanning electron microscopy images further revealed morphological changes from fibrillated structures to compact particulate morphologies after AKD treatment and spray drying. Notably, high hydrophobicity was achieved without an additional curing process, indicating that spray drying provided sufficient thermal energy for AKD-mediated hydrophobization. These results demonstrate that spray drying combined with AKD treatment can effectively produce hydrophobic MFC powders potentially suitable for composite applications.