Emulsions undergoing phase transition: Effect of emulsifier type and concentration

Abstract

Pickering emulsion stabilized by cellulose nanocrystals (CNCs) during the phase transition of the dispersed oil is poorly understood. We investigated the capability of CNC in stabilizing Pickering emulsions during the temperature-induced phase transition. Paraffin wax emulsions stabilized by sodium dodecyl sulfate (SDS) were less stable than CNC stabilized emulsions. The relationship between droplet size and emulsifier content was examined, and a new model describing this relationship is proposed. The droplet size of CNC-based systems was not affected by temperature variation, even at low CNC concentrations. The minimum CNC content required to stabilize the paraffin wax emulsion was lower than SDS. DSC results indicated that higher droplet surface coverage with emulsifiers enhanced the deformation resistance of the crystallized droplets, which enhanced the emulsion stability. Temperature sweep viscosity measurements showed that the stability of CNC-based systems was not significantly impacted by the phase transition of the paraffin wax. Rheological amplitude sweep analysis indicated that emulsions above the melting point of paraffin wax were more stable at all strain levels. However, the SDS-based systems displayed substantial heterogeneity after the liquid-solid transition. Frequency sweep tests revealed that CNC-stabilized emulsions were more stable than SDS-stabilized emulsions.