Preparation of a novel silica-stabilized oil/water emulsion

Colloidal silica (Ludox), flocculated with the homopolymer hydroxypropyl cellulose, has been used as the stabilizing agent to produce a highly stable oil/water (O/W) emulsion showing no signs of particle growth over a period 3 months; volume fractions as high as 0.81 have been prepared. The efficiency of the emulsification process has been very greatly imporved, compared with the methods of other workers who used different co-stabilizers, and it is estimated that to achieve stabilization it is necessary that the interface be coated with the equivalent of 29% close-packed silica spheres. It is, therefore, unnecessary to coat the oil droplets with a rigid crust of silica particles in order to achieve stabilization, as had been proposed in previous work. The mechanism for the stabilization has been established as the adsorption of silica flocs at the O/W interface. The rheological properties, as a result, are controlled by the colloid chemistry of silica; the elastic and viscous properties of the system increase as the attractive forces between the silica particles grow.