Influence of continuous phase viscosity on emulsification by ultrasound

Power ultrasound is one means among others of mechanically producing emulsi ons. In spite of numerous publications on the basic principles of this tech nique, there is insufficient knowledge of continuous ultrasound emulsificat ion processes and the main parameters of practical relevance. A comparison of this system with other continuous mechanical emulsifying devices is made . The effect of continuous phase viscosity on droplet disruption due to ult rasound is the subject of a more detailed investigation. Continuous phase v iscosity is varied by means of water soluble stabilizers (o/w systems) and different oils (w/o systems). At constant energy density, droplet size decr eases when adding stabilizers, whereas the viscosity of the oil in w/o emul sions has no effect. Qualitative investigations of the local distribution o f cavitation have shown very small penetration depths of cavitation into th e liquid. This emphasizes the need for improvement of apparatus design to o ptimize the emulsification process. (C) 2000 Elsevier Science B.V. All righ ts reserved.