ABSTRACT
Surfactants (amphipathic molecules consisting of hydrophobic and hydrophilic portions) are essential materials for preparation of many industrial systems, of which we mention dyestuffs, paper coatings, inks, agrochemicals, pharmaceuticals, personal care products, ceramics, and detergents. One of the most important applications of surfactants is in the preparation of oil-in-water (o/w) and water-in-oil (w/o) emulsions. In this case, the hydrophobic portion of the surfactant molecule should adsorb strongly at the o/w interface or it becomes dissolved in the oil phase, leaving the hydrophilic components in the aqueous medium, whereby they become strongly solvated by the water molecules. This confi guration provides an effective repulsive force, usually referred to as steric stabilization. A convenient method for selection of surfactants is based on the relative proportions of the hydrophilic and hydrophobic groups, that is, the hydrophilic-lipophilic balance (HLB) introduced by Griffi n [1,2]. For o/w emulsions, one chooses surfactants with an HLB number in the
range 8-18 (depending on the nature of the oil), whereas for w/o emulsions an HLB number in the range 3-6 is usually the case.
