lesson 2 Flashcards
Which phase of an emulsion contains emollients and fragrance?
oil
Which phase of an emulsion contains emollients and fragrance?
oil
Which phase of an emulsion contains humectants and viscosity enhancers?
water
Emulsifiers can be found in which phase of an emulsion?
Oil and water
Emulsions take on the character of the _____ phase
external
emulsion viscosity can be lowered by
diluting with water (o/w) or diluting with oil (w/o)
which type of emulsion has a stable pH
O/w
The type of emulsion is somewhat governed by _________, but mostly depends on _________
phase volume
type of surfactant
Bancrofts rule states that
the continuous phase will be whichever phase the surfactant is most soluble in
More than 74% internal phase leads to
close particle interaction and deformation
Explain the 3 phase-system theory of emulsions
- emulsifier forms a gel network of liquid crystalline and lamellar structures in water
- oil phase is dispersed in between gel network
Microemulsion droplet size
Less traditional method of producing an emulsion that allows the emulsifier the optimal opportunity to adsorb at the interface
Make an emulsion concentrate and then dilute it with the external phase
Purpose of stabilizing emulsions
delay the day when the instability will arrive, since all are inherently unstable
Shelf life requirements
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
van’t hoff’s rule says
rate of biochemical reactions doubles for every 10 degree celsius increase in temperature up to the point that proteins break down
Aggregation/floculation happens when
particles approach each other
this is reversible
Coalescence happens when
particles approach each other and their films rupture
this is not reversible
Phase inversion happens when
- HLB of nonionics decreases as temperature increases
- At a specific temperature (PIT) hydrophilic and lipophilic characteristics will be equal relative to required HLB of oil phase
Causes of emulsion instability
- Ostwald Ripening
- Creaming/Sedimentation
- Aggregation/flocculation
- Coalescence
Prevention of creaming
- Thicken outer phase
- Reduce particle size
- Density effects
The Gibbs-Marangoni effect describes the incorporation of movable elastic surfactant film at the oil-water interface to prevent coalescence by
creating interfacial tension gradient to stabilize droplets in close proximity
Prevention of coalescence
- Steric/electrostatic barriers to keep droplets apart through surfactant/polymer choice
- Surfactants/emulsifiers to lower interfacial tension
Ostwald ripening can be prevented by having
narrow range of particle sizes
Particle size is influenced by
- emulsifier choice
- emulsifier placement
- emulsifier concentration
- processing time/temperature/order of addition
Two mechanisms of stabilization
- Barrier forms around droplets to strengthen o/w interface
- Gel network is formed which extends from the droplet surface out into bulk of external phase to increase viscosity and impede droplet movement
Ways to retard coalescence AND creaming
- Viscosity enhancement
- Protection of droplets through lamellar gel network phases and/or thickeners
Type of surfactant association structure in which phases surround droplets to create a barrier to protect them from approaching closely
Lamellar liquid crystalline phase
Type of surfactant association structure that forms a network to enhance viscosity to stabilize the droplets, making particles less likely to sink or collide
Gel phase network
Emulsifying “wax” systems consist of
mixtures of hydrophilic and lipophilic emulsifiers
3 Functions of emulsifiers
- Reduce surface tension
- form complex interfacial films on surface of emulsion droplets
- form liquid crystalline structures which act as a barrier to coalescence
Surfactants lower
- surface tension of a liquid
- interfacial tension between two liquids
Above CMC, surface tension ________
remains constant
Which phase of an emulsion contains humectants and viscosity enhancers?
water
Emulsifiers can be found in which phase of an emulsion?
Oil and water
Emulsions take on the character of the _____ phase
external
emulsion viscosity can be lowered by
diluting with water (o/w) or diluting with oil (w/o)
which type of emulsion has a stable pH
O/w
The type of emulsion is somewhat governed by _________, but mostly depends on _________
phase volume
type of surfactant
Bancrofts rule states that
the continuous phase will be whichever phase the surfactant is most soluble in
More than 74% internal phase leads to
close particle interaction and deformation
Explain the 3 phase-system theory of emulsions
- emulsifier forms a gel network of liquid crystalline and lamellar structures in water
- oil phase is dispersed in between gel network
Microemulsion droplet size
less than 100 nm
Less traditional method of producing an emulsion that allows the emulsifier the optimal opportunity to adsorb at the interface
Make an emulsion concentrate and then dilute it with the external phase
Purpose of stabilizing emulsions
delay the day when the instability will arrive, since all are inherently unstable
Shelf life requirements
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
van’t hoff’s rule says
rate of biochemical reactions doubles for every 10 degree celsius increase in temperature up to the point that proteins break down
Aggregation/floculation happens when
particles approach each other
this is reversible
Coalescence happens when
particles approach each other and their films rupture
this is not reversible
Phase inversion happens when
- HLB of nonionics decreases as temperature increases
- At a specific temperature (PIT) hydrophilic and lipophilic characteristics will be equal relative to required HLB of oil phase
Causes of emulsion instability
- Ostwald Ripening
- Creaming/Sedimentation
- Aggregation/flocculation
- Coalescence
Prevention of creaming
- Thicken outer phase
- Reduce particle size
- Density effects
The Gibbs-Marangoni effect describes the incorporation of movable elastic surfactant film at the oil-water interface to prevent coalescence by
creating interfacial tension gradient to stabilize droplets in close proximity
Prevention of coalescence
- Steric/electrostatic barriers to keep droplets apart through surfactant/polymer choice
- Surfactants/emulsifiers to lower interfacial tension
Ostwald ripening can be prevented by having
narrow range of particle sizes
Particle size is influenced by
- emulsifier choice
- emulsifier placement
- emulsifier concentration
- processing time/temperature/order of addition
Two mechanisms of stabilization
- Barrier forms around droplets to strengthen o/w interface
- Gel network is formed which extends from the droplet surface out into bulk of external phase to increase viscosity and impede droplet movement
Ways to retard coalescence AND creaming
- Viscosity enhancement
- Protection of droplets through lamellar gel network phases and/or thickeners
Type of surfactant association structure in which phases surround droplets to create a barrier to protect them from approaching closely
Lamellar liquid crystalline phase
Type of surfactant association structure that forms a network to enhance viscosity to stabilize the droplets, making particles less likely to sink or collide
Gel phase network
Emulsifying “wax” systems consist of
mixtures of hydrophilic and lipophilic emulsifiers
3 Functions of emulsifiers
- Reduce surface tension
- form complex interfacial films on surface of emulsion droplets
- form liquid crystalline structures which act as a barrier to coalescence
Surfactants lower
- surface tension of a liquid
- interfacial tension between two liquids
Above CMC, surface tension ________
remains constant
