Lecture 2 - Emulsion Technology Flashcards

1
Q

What is a cosmetic?

A

A product, except soap, intended to be applied to the human body for cleansing, beautifying, promoting attractiveness or altering the appearance

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2
Q

When is a cosmetic also a drug?

A

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

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3
Q

“Intended Use” within the meaning of the FD&C Act is determined from…

A

its label or labeling

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4
Q

What is a colloidal two phase system?

A

Submicron (

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5
Q

Why is water usually highest % in emulsions? What is a possible problem with it?

A
  • 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
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6
Q

2 phases of emulsion

A

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

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7
Q

examples of ingredients in aqueous phase

A
Water
Humectants
Hydrophilic actives
Preservatives
Emulsifiers
Thickeners
Salts
pH adjusters
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8
Q

examples of ingredients in oil phase

A
Emollients
Hydrophobic actives
Antioxidant
Emulsifiers
Waxes/Lipids
Silicones
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9
Q

The emulsion takes on the character of the _________ phase.

A

external (continuous)

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10
Q

Properties of o/w phase

A
  • stable pH
  • can be diluted with water (lowering the viscosity)
  • can be washed off the skin with water
  • will exhibit conductivity
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11
Q

Properties of w/o phase

A
  • 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
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12
Q

Bancroft’s rule

A

whichever phase the surfactant is most soluble in is the continuous phase

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13
Q

More than 74% internal phase leads to …

A
  • close particle interaction and deformation

- more possibility of coalescence

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14
Q

3 phase system theory of o/w emulsions

A
  • 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
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15
Q

3 types of emulsions based on droplet size

A
  • macroemulsions are in the > 1,000 nm range
  • “blue-white” emulsions in the submicron range 100+ nm
  • Microemulsion -
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16
Q

traditional method for producing emulsion

A
  • 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)
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17
Q

less traditional methods for emulsion mfg. (3)

A
  • 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.
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18
Q

All emulsions are…

A

inherently unstable (with the exception of spontaneously forming micro emulsions). All we can do is delay the day when the instability will arrive

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19
Q

product stability

A

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

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20
Q

shelf life: Before a cosmetic product is approved for distribution/sale, its manufacturer must be satisfied that the product is …

A

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.

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21
Q

for every temperature rise of 10 degrees C …

A

rate of biochemical reactions (most body functions) doubles, up to a point (when proteins break down)

22
Q

van’t Hoff’s rule

A

the velocity of chemical reactions is increased twofold or more for each rise of 10°C in temperature; generally true only when temperatures approximate those normal for the reaction

23
Q

4 types of emulsion instability

A

Ostwald Ripening
Creaming and Sedimentation
Aggregation / Flocculation
Coalescence

24
Q

Aggregation / Flocculation

A

Particles approach each other (reversible)

25
Q

Coalescence

A

particles approach each other and their films rupture (not reversible)

26
Q

Stoke’s Law Equation

A

V = (2change in densgr^2) / (9visc)

27
Q

3 ways to prevent coalescence

A
  • Prevent creaming / sedimentation and aggregation
  • Gibbs - Marangoni effect (surfactant choice)
  • Viscosity enhancement and protection of droplets through lamellar gel network phases and / or other thickeners
28
Q

Gibbs - Marangoni effect

A
  • A movable elastic surfactant film at the oil -water interface
  • adds interfacial tension gradients to stabilize droplets in close proximity.
29
Q

Particle size influenced by what 4 things?

A
  • Choice of emulsifier
  • Placement of emulsifier
  • Concentration of emulsifier
  • Processing (mixing time, temp, order of addition)
30
Q

General mechanism of stabilization with gel network. What are the benefits?

A
  • A barrier forms around the emulsion droplets and strengthens the o/w interface.
  • A gel network is formed which extends from the surface of the droplets out into the bulk of the external phase.
  • This increases the viscosity and impedes droplet movement.
31
Q

How to retard creaming

A

Outer phase thickening
Particle size reduction
Density effects

32
Q

How to retard coalescence

A
  • Steric and / or electrostatic barriers to keep droplets apart- surfactants, polymers
  • Surfactants /emulsifiers lower interfacial tension and reduce the free energy difference between dispersed particles and coalesced liquid
33
Q

How to retard coalescence and creaming

A

Viscosity enhancement and protection of droplets through lamellar gel network phases and / or other thickeners

34
Q

benefit of: Lamellar liquid crystalline phases surrounding droplets and creating a barrier near the interface

A
  • Droplets are protected from each other (cannot approach closely)
  • builds up the continuous water phase
  • thickens and stabilizes
35
Q

benefit of: gel phase extending out into the continuous phase

A
  • Network is formed giving viscosity to the solution and stabilizing the droplets
  • Particles are less likely to rise or sink or collide with each other.
36
Q

Emulsifying wax systems

A
  • Mixtures of Hydrophilic and Lipophilic Emulsifiers
  • Usually non-ionic emulsifiers
  • “one step” emulsification
  • Popular in high pH systems
37
Q

emulsifiers - what is structure and type?

A
  • Longer hydrophobic chains (Less branching, Less unsaturation)
  • Nonionic, anionic, cationic headgroups
  • HLB system for selecting a range of nonionics (Mixtures of low & high HLB are more efficient & effective)
  • Particles can also stabilize an emulsion
38
Q

emulsifiers - function

A
  • Reduce surface tension
  • Form complex interfacial films (on the surface of emulsion droplets)
  • Form liquid crystalline structures which act as a barrier to coalescence
39
Q

Surfactants - what are they?

A
  • SURface ACTive ageNTS

- Surfactants are amphiphilic organic molecules

40
Q

Surfactants - function

A
  • lower the surface tension of a liquid, the interfacial tension between two liquids, or that between a liquid and a solid.
  • may act as detergents, wetting agents, emulsifiers, foaming agents, and dispersants.
41
Q

Surfactant - structure

A
  • The head group is water soluble
  • The tail group is insoluble in water, but soluble in organic oils
  • can be thought to have “2” solubility parameters (hydrophobe and hydrophile)
42
Q

What happens at the CMC (Critical Micelle Concentration) ?

A
  • Surfactants in water form micelles

- The system has the lowest surface tension and highest true solubility of surfactant

43
Q

Structure of surfactant hydrophobic tail group

A
  • commonly a hydrocarbon structure
  • Can be straight or branched chain
  • unstaurated
  • aromatic and aliphatic
  • can be 1-2 tail groups
  • C8-C20
44
Q

Which carbon length pf tailgroup is for surface activity?

A

C8

45
Q

Which carbon length of tailgroup is for water solubility?

A

C20

46
Q

Natural oils and fatty acids

A

Triglyceride esters with an even number of carbons, saturated (animal) or unsaturated (plant) or hydroxyl (plant)

47
Q

Structure of surfactant hydrophilic head group

A
  • strongly polar or has a charged ionic structure.

- can be Nonionic or Ionic (anionic, cationic, amphoteric)

48
Q

examples of anionic emulsifiers

A

TEA Stearate
Sodium Cetyl Sulfate
K-Cetyl Phosphate

49
Q

examples of cationic emulsifiers

A

Distearyl Dimonium Chloride

Stearalkonium Chloride

50
Q

examples of nonionic emulsifiers

A

PEG 40 Stearate
Polysorbate 60
Steareth 2

51
Q

examples of amphoteric emulsifiers

A

Stearyl Betaine

Sodium Coco Ampoacetate

52
Q

Examples of stabilizer polymers, gums, and solids

A
  • Carbomers/Alkyl Acrylates/other copolymers
  • Liquid dispersion polymers
  • Xantahm gum, guar gum, sclerotium gum
  • Cellulose derivatives (CMC, HEC)
  • Bentonite/Hectorite clats, MgAl Silicate clay