Lecture 2 - Emulsion Technology Flashcards
What is a cosmetic?
A product, except soap, intended to be applied to the human body for cleansing, beautifying, promoting attractiveness or altering the appearance
When is a cosmetic also a drug?
When it is intended to cleanse, beautify, or promote attractiveness as well as treat or prevent disease or otherwise affect the structure of any function of the human body
“Intended Use” within the meaning of the FD&C Act is determined from…
its label or labeling
What is a colloidal two phase system?
Submicron (
Why is water usually highest % in emulsions? What is a possible problem with it?
- It is cheap, innocuous, and a good diluent
- Problem: microbes can grow in water and other ingredients in formula can serve as nutrients, need to use a preservative system
2 phases of emulsion
The oil phase contains any emollients, fragrance, oil soluble dyes and actives.
The water phase contains water soluble dyes, humectants, water soluble actives, and viscosity enhancers.
Surfactants are at interface and in both phases
examples of ingredients in aqueous phase
Water Humectants Hydrophilic actives Preservatives Emulsifiers Thickeners Salts pH adjusters
examples of ingredients in oil phase
Emollients Hydrophobic actives Antioxidant Emulsifiers Waxes/Lipids Silicones
The emulsion takes on the character of the _________ phase.
external (continuous)
Properties of o/w phase
- stable pH
- can be diluted with water (lowering the viscosity)
- can be washed off the skin with water
- will exhibit conductivity
Properties of w/o phase
- unstable pH (due to discontinuous water phase)
- will feel heavy and greasy (silicones can improve this)
- can be diluted with oil or solvent (lowering the viscosity)
- cannot be readily washed off the skin
Bancroft’s rule
whichever phase the surfactant is most soluble in is the continuous phase
More than 74% internal phase leads to …
- close particle interaction and deformation
- more possibility of coalescence
3 phase system theory of o/w emulsions
- external bulk water phase (external phase)
- dispersed liquid oil phase (internal phase)
- emulsifier forms a gel network of liquid crystalline, lamellar structures in water
- oil phase is dispersed in between the gel network
3 types of emulsions based on droplet size
- macroemulsions are in the > 1,000 nm range
- “blue-white” emulsions in the submicron range 100+ nm
- Microemulsion -
traditional method for producing emulsion
- Heat oil phase to 5-10C above melting point of lowest melting point wax, generally 70-80C
- Add internal phase to external phase slowly.
- Heat water phase to approximately same temperature
- Mix without heating until the temperature reaches 5C below the lowest melting point wax and then rapid cooling may take place.
- At 30-40C add temperature sensitive ingredients (Fragrance, Preservatives, Biologicals/ Actives)
less traditional methods for emulsion mfg. (3)
- Add external phase slowly to the internal phase to produce a clear phase inversion. This only works for O/W emulsions.
- Make an emulsion concentrate and then dilute it with the external phase. This allows the emulsifier the optimal opportunity to adsorb at the interface.
- One pot processing.
All emulsions are…
inherently unstable (with the exception of spontaneously forming micro emulsions). All we can do is delay the day when the instability will arrive
product stability
The stability of the product stored in an inert, impermeable container with which it does not interact and which fully protects it from ambient atmosphere
shelf life: Before a cosmetic product is approved for distribution/sale, its manufacturer must be satisfied that the product is …
safe, stable and usable, for some specified time during normal storage and handling, under extraordinary warehouse and shipping conditions and even when mishandled by consumers.
