Emulsion Flashcards
Emulsions
dispersion consisting of two virtually immiscible liquids stabilized by surface active agents
Oil-in-water emulsion
Water-in-oil emulsion
Oil-in-water emulsion: oil is the internal phase and water is the external phase
Water-in-oil emulsion: water is the internal phase and oil is the external phase
Interfacial Tension
force per unit length existing at the interface between two immiscible liquid phases (or two condensed phases)
Surface Active Agents
Surfactants are molecules that preferentially absorb at interfaces
Surfactants are classified based on the change of the _______ region
hydrophilic
The surface and interfacial properties of solutions containing surfactants change sharply over a narrow concentration range
Critical micelle concentration (CMC)
A surfactant having a greater hydrophilic than hydrophobic character promote formation of _______ emulsion
o/w
Interfacial Film Theory
-surfactant forms a thin layer of adsorbed molecules around the immiscible droplet
-the layer prevents the contact coalescence of the dispersed phase
Acacia, tragacanth, agar, pectin
Carbohydrate material (o/w emulsion)
Gelatin, lecithin, casein
Proteins (o/w emulsion)
Stearyl alcohol, cetyl alcohol, glyceryl monostearate
High molecular weight alcohols (o/w emulsion)
Three classic methods used in compounding
dry gum
wet gum
bottle/forbes method
Aggregation
internal oil phase can rise to the top of the emulsion
Creaming
separation of the globules
Coalescence
creamed emulsion resulting in individual droplets
improper surfactant selection
