Electro-rheological investigation on W/O emulsions morphology under electric fields

Abstract

Five w/o model emulsions were produced using mineral oil, deionized water and Span 80. The samples of higher stability and smaller mean droplet size were produced by increasing surfactant concentration. Critical electric field stability tests were conducted, both using electrocoalescence and electrorheology, to confirm that critical field increases with decreasing droplet size. As direct current field increases, measurements of G'/G" have shown an intersection between these moduli, from which emulsions presented a predominantly elastic behavior. Optical microscopy tests suggested that such crossing point is related to a minimum electric field in which an emulsion effectively undergoes structural changes due to droplets alignment. This minimum alignment field seems to be correlated with the critical electric field once it is approximately half of critical electric field value.