Micro Encapsulation by Air Suspension Technique:

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Micro Encapsulation by Air Suspension Technique:

What is Micro encapsulation?

It is a process in which relatively thin coatings are applied to small particles of droplets of liquid or solids and dispersions.

It is a very useful process in:

1. Altering colloidal and surface properties

2. In converting liquids to solids

3. To protect form the environment

4. Controlled release

5. Sustained release

6. Taste masking in powders, suspensions and chewable tablets

Various methods by which micro encapsulation can be done is:

1. Air suspension

2. Coacervation-phase separation

3. Pan coating

4. Solvent evaporation techniques and

5. Spray drying and congealing

Air Suspension Method:

It is invented by the Professor Dale E. Wurster at University of Wisconsin.
In this process particulate core material which is solid is dispersed in the supporting air stream. Inside the coating chamber the particles are made to suspend on an upward moving air stream.

The recirculation of the particles in the coating zone portion is effected by the design of the chamber and its operating parameters. This cyclic process is repeated about several hundred times until the required micro encapsulation is done i.e. whether the required parameters such as coating thickness etc.., are achieved.

The air stream which supports the particles also helps in the drying of particles, and these drying rates are directly proportional to the temperature of the air stream which assists in supporting.

Various variables to be considered during this process are:

* Volume of the air required to fluidize and support the core

* Coating material application rate and its concentration

* Amount of coating material required

* Temperatures of the inlets and outlets

* Various parameters of core material such as its melting point, density , surface area, friability, volatility, crystallinity, flow ability and solubility.

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Author: Shanthi Priya

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