Emulsions Stabilized by Microfibrillated Cellulose: The Effect of Hydrophobization, Concentration and O/W Ratio

Abstract

The properties of emulsions stabilized by nanosized cellulose particles (denominated also microfibrillated cellulose; MFC) were investigated. The wettability (hydrophobicity) of the MFC was changed through surface modification with chlorodimethyl isopropylsilane. The modified MFC was characterized with Fourier transform infrared spectroscopy (FTIR), and x-ray photoelectron spectroscopy (XPS). Using MFC of intermediate hydrophobicity resulted in water-in-oil emulsions within a range of oil/water ratios. The emulsifying capacity of the MFC was found to be proportional to both the relative amount of MFC used and its wettability (degree of surface substitution; DSS). The emulsions separated rapidly from the excess oil phase; the separated emulsion layers were highly stable towards gravity-induced sedimentation and, once a stable MFC network was formed, were also stable towards coalescence. The influence of the oil/water ratio, the concentration and DSS of the MFC on the stability of the emulsions toward coalescence, and the inversion to oil-in-water emulsions was also investigated. The results verify that MFC can be efficiently used as a stabilizer of oil/water emulsions within a range of oil/water ratios and particle concentrations.

Keywords:

• Emulsion stability
• MFC hydrophobicity
• microfibrillated cellulose
• nanosized cellulose
• w/o emulsions

Acknowledgments

This project was supported by the Research Council of Norway, Södra Cell, Akzo Nobel and Jotun. Dr. Leena-Sisko Johansson, Helsinki University of Technology, is thanked for the XPS analyses. Dr. Kristofer Paso, Ugelstad Laboratory, Norwegian University of Science and Technology is thanked for the AFM pictures.

Notes

^a Ash-free pure cellulose filter paper.

^b Nonsilylated sample.