Polymeric Emulsifiers and Stabilizers

In nature as well as in technology, polymeric emulsifiers and stabiUzers play a major role in the preparation and stabiUzation of emulsions. Natural materials such as proteins, starches, gums, cellulosics, and their modifications, as well as synthetic materials such as polyvinyl alcohol, polyacryhc add, and polyvinylpyrrolidone, have several characteristics that make them extremely useful in emulsion technology. By the proper choice of chemical composition, such materials can be made to adsorb strongly at the interface between the continuous and dispersed phases. By their presence, they can reduce interfacial tension and/or form a barrier (electrostatic and/or steric) between drops. In addition, their solvation properties serve to increase the effective adsorbed layer thickness, increase interfacial viscosity, and introduce other factors that tend to favor the stabilization of the system. [Pg.263]

Finally, as can be seen from Equations (10.19) and (10.20), the frequency of particle encounters potentially leading to flocculation and/or coagulation is inversely proportional to the viscosity of the continuous phase. The presence of a polymer in solution will increase the viscosity of the system and impart added kinetic stability to the emulsion. [Pg.263]

The subject of the mechanisms and degree of polymer adsorption at interfaces is also discussed in more detail in Chapter 14. For now, suffice it to say that macromolecular additives to emulsion systems constitute a major pathway for attaining workable, long-lived practical emulsions. In fact, their use is essential to many important product types, not the least of which are food colloids, inks, pharmaceuticals, and the photographic industry. [Pg.264]

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