Emulsion

In this blog we are discussing about the emulsion. What is an emulsion short answer, What is an emulsion explain the classification of emulsions with examples, How many types of emulsion theories are there, What is the stability of emulsions, How do you preserve emulsion and What are the rheological properties of emulsion. so friends read the blog till the end for full information.

What is an emulsion short answer?

It is a biphasic system of two immiscible  liquid where one liquid [dispersed phase ] is dispersed into another liquid [dispersion medium]. with the help of any emulsifying agent.

eg., vanishing cream, gel, lotion, ointment etc.

What is an emulsion explain the classification of emulsions with examples?

It can be classify into four types:- 

i. Oil in water type (O/W) emulsion.

ii. Water in oil type (W/O) emulsion.

iii. Multiple emulsion.

iv. Micro emulsion.

i. Oil in water type (O/W) emulsion:- [Aqueous emulsion].

        This are those emulsion in which dispersed phase is oil and continuous phase in water.

        eg. Milk, lotion, liniments etc.

⦁ Non-greasy nature [easily remove from body].

ii. Water in oil type emulsion:- [oil emulsion].

         This are those emulsion in which dispersed phase is water and continuous phase is oil.

         ex. Butter and cold creams etc.

⦁ Greasy in nature  [oily nature not easily removed from body].

iii. Multiple emulsion:- [ Double emulsion].

        Those emulsion which are made up of more then two phase. 

⦁ In which the droplets of one liquid are dispersed in droplet of second liquid. which is further                  dispersed in dispersion medium.

                                                                             Types

[O/W/O] Oil in water in oil	[W/O/W] Water oil in water
In which O / W emulsion dispersed in another oil phase.	In which W / O emulsion dispersed in another water phase.

•  This type of emulsion prepared to prolong the release of drugs.
• It enhance bioavailability.

iv. Micro emulsion:- 

        Those emulsion in which particles size of dispersed phase in less than (Micro).

⦁ It is clear, transparent and thermodynamically stable as compared to normal emulsion.

How many types of emulsion theories are there?     

Those theories which more and stay emulsion stable:-

i. Mono molecular Adsorption theory:-

⦁ During preparation of emulsion , the oil / water get dispersed in continuous phase partical get                  atomized [reduce particle size].

⦁ Due to small phase size surface area increases which further increases the surface free energy,                therefore system become unstable.

# To resolve this problem or to make system stable we add surfactants or emulsifying agents which                reduce the interfacial tension or surface free energy and make emulsion stable.

⦁ Mechanism:- Surfactant contain polar and nonpolar part. polar oriented toward oil and form a                  stable mono molecular film on the surface of dispersed droplet.

ii. Multimolecular adsorption theory:-

⦁ Monomolecular and multimolecular theory both used to stop flocculation, coulescence, also prevent the breaking of emulsion.

⦁ Mechanism:- In this, emulsifying agent's small-small particles join together and cover the dispersed particles and make multimolecular film.

⦁ They also act by making the medium viscous.

eg. Acacia, Methyl cellulose etc.

⦁ Flocculation- Small particles forms a one big particles called floccules.

iii. Solid particle absorption theory:- 

⦁ In this, we add solid emulsifying agent in emulsion which increases the viscosity of emulsion.

⦁ It also prevent (reduce) coalescence of dispersed particles.

               eg. Colloidal day etc.

iv. Formation of electrical double layer:-

⦁ In emulsion, oil droplets contain either negative or positive charge.

⦁ Due to present of change they, develop electrical double layer (already discussed).

⦁ Due to this oil droplets produce repulsion force into each other and they remain suspended.

⦁ They prevent coalescence and breaking of emulsion.

What is the stability of emulsions?

⦁ A stable emulsion is one in which the globules [dispersed phase] retain their size and as well as              remain uniformly distributed throughout the continuous phase.

⦁ Some instability occur during storage and formulation of emulsion.

i. Creaming:- 

It is a reversible phenomena. in which droplets of dispersed phase come together or deposit at the surface of the emulsion.

[O/W]	[W/O]
·       In this, oil have low density so they come together at the surface of emulsion. ·       Upward creaming.	·       In this density of water (dispersed phase) is more than continuous phase so particles come together at the bottom of emulsion. ·       Down ward creaming.

 ii. Coalescence:- 

In emulsion, oily particles [disperse phase] because of sticky nature attract each                other and they aggregate to form big particles.

iii. Breaking:- [Creching]

⦁ Due to improper mixing of oil and water in emulsion, Emulsion get separated into layer i.e. oil                and  water. 

⦁ It is also acquired due to improper ratio of oil and water.

iv. Flocculation:- 

        In this, due to increased surface free energy particle get aggregated to form                        floccules to decrease surface area.

v. Phase inversion:-

 In this the phase of emulsion get inverted i.e., O/W to W/O, W/O to O/W.

⦁ It happened due to mixing problem or by choosing wrong dispersed phase during formulation.

vi. Physical & chemical property change:- to prepare an emulsion we use stable emulsion.

⦁ Some time, addition of these agents cause changes in properties like color, pH, odour, taste etc.

How do you preserve emulsion?

• we have to keep emulsion stable and effective till expiry for this.
• emulsion- (ideal property of preservatives)
• not change their nature and properly.
• not react oil and water with each other.
• stable.

1. preservation from microorganisms-

• Microorganisms may arise in emulsion due to present of high water content.
• for this, we add preservative like methyl paraben, propyl paraben, benzoic acid etc.
• which inhibit the growth of bacteria.
• preservation should be:-
• non irritant and non-toxic
• tasteless, colourless and odour less
• should be stable.

2. Preservation on from oxidation-

oxygen present in atmosphere cause oxidative cause such as rancidity & spoilage for this, we use some antioxidant which can prevent the changes occurs due to atmospheric oxygen.

• Antioxidant should be;-
• non-toxic and non-irritant.
• effective at low concentration.
• eg. BHT (Butylated hydroxy toluene), Ethyl and propyl-gallate.

What are the rheological properties of emulsion?

These properties of emulsion are related to the flow of emulsion.

Application- 

• Spreadibility (for skin).
• removal from container (bottle).
• Flow of emulsion through hypodermic needle.
• Proper mixing (during manufacturing)

it can be of two types-

1. Newtonian flow-

• this type of flow show by dilute emulsion.
• eg. Micro-emulsion.

1. Non-Newtonian flow-

• This type of flow show by concentrated emulsion.
• eg. Lotions, creams etc.
• optimum viscosity is desirable for good stability of emulsion.
• the increase in the viscosity of the emulsion reduce the flocculation.
• Rheological property of emulsion can be controlled by-
• concentration of dispersed phase.
• nature and concentration of emulsifying system, etc.