emulsions and creams

What are emulsions?

type of colloid, low viscosity disperse system

What is an emulsion made up of?

two immiscible phases and a surfactant, dispersions

Do particles dissolve in an emulsion?

no they are dispersed or suspended

What is the internal phase?

the substance that is dispersed.

What is emulsion stability?

the length of time a mixture remains an emulsion

What is creaming?

droplets rise upwards

When does creaming occur?

when dispersed particles are less dense

What is coalescence?

when droplets form together to form bigger droplets.

What is flocculation?

droplets come together to form floccs

What is sedimentation?

droplets fall down to the bottom.

What is Ostwald’s ripening?

small droplets disappear and larger droplets get larger.

What does a high zeta potential mean?

more repulsive particles, more stabilised system.

What factors affect emulsion?

HLB

Relative amount of phases

Bancroft rule

mixture of surfactants

What are creams?

semi solid emulsions for external application.

What is the difference between an o/w and w/o cream?

o/w is a vanishing cream- cooling action

w/o is an oily cream

What is the critical micelle concentration?

the concentration at which the adsorbed monolayer becomes saturated with surfactant, additional surfactant molecules will form micelles

Why do creams/ emulsions need to be manufactured in aseptic conditions?

they are susceptible to microbial growth in the aqueous phase.

Why are antioxidants used in emulsions?

prevent oxidation of the oily phase.

What are the two types of preparation methods?

solution method- surfactant dissolved in each phase.

dispersion phase- surfactant in the less soluble phase.