ABSTRACT

I. INTRODUCTION Emulsions are small drops of one Liquid dispersed in another liquid, Everyday examples include paints, cosmetics, and foods: mayonnaise and salad dressing, for instance, are concentrated oil-in-water emulsions, In the area of plastics technology, we find thai polymers are mutinely blended with each other with a view toward producing materials witb improved properties, A specific example of the success of this approach is the improvement in impact strength of plastics such as nylons and polyesters by the addition of thermodynamically immiscible, mbber-type polymers II, for example], High-impact polystyrenes and ABS polymers generally contain microgel rubber particles in which the rubber particles are also graft polymers, and the morphology of the dispersed particles may be quite complex,

The ability of one polymer to toughen another polymer depends, in part, on how fine a dispersion can be generated, ln particular. it is necessary that the minor phase be dispersed in the major phase in the form of micron-or submicronsized spherical droplets; this is typically achieved in corotating twin-screw extruders, A novel application of emulsions that is related directly to their rheological properties is the pipeline transport of heavy crude oils having a viscosity as high as 500 Pa-sec [2], Ordinarily, to economically pump such viscous liquids, we would have to either beat or dilute the crude oils, but these crudes can be pumped easily in the form of concentrated (but low-viscosity) oil-in-water emulsions having an oil volume fraction in excess of 0,7, When the ratio of the dispersed-phase viscosity to the continuous-phase viscosity is this high, the emulsion

behaves essentially as a suspension, and its viscosity can be predicted using the equations presented in Chap. I 0 [ 3]. The emulsion viscosity is typically low because of the very large value of the maximum packing fraction that results from a wide distribution of droplet sizes. Note that such emulsions are often produced naturally during enhanced oil recovery using water flooding.