On the stabilization of emulsions by cellulose nanocrystals and nanofibrils: Interfacial behavior and synergism

Abstract

Competitive adsorption of cellulose nanofibers at oil-water interface in Pickering emulsion is reported here. Dodecane-in-water emulsions stabilized by either of two types of nanocelluloses, cellulose nanocrystals (CNC) or cellulose nanofibrils (CNF), as well as by their binary mixtures with increasing fractions of CNC, were prepared using particle concentrations of 0.1–0.5 wt% and studied. Despite differences in shape and morphology, both forms of nanofibers produced stable emulsion droplets even at low particle concentrations (0.1 wt%), with CNC producing smaller droplets and emulsions with higher stability. When mixed, an increased fraction of CNC in the mixture reduced the average droplet size, which however applied only for higher contents of oil (30 and 50 wt%) and higher total contents of cellulose particles used under emulsification. The CNC particles controlled the size of emulsion droplets, while the role of CNF contributed to the further surface coverage. When the fraction of CNF in the mixture increased, the capability of CNC particles to readily adsorb at the oil-water interface was reduced by the CNF nanofibrils present in aqueous phase. The stability of emulsions with respect to changes in droplet size and creaming index was influenced more by oil content and total particle concentration than by the fraction of CNC present in the mixture.