Interfacial polymerization is still used because it gives the microcapsules a seal: when a hole forms in the wall, it is plugged by the polymer that forms at the interface by the reaction of the monomer present in the dispersion with the monomer present in the water.
Microencapsulation by Interfacial Polymerization
How microencapsulation works by Interfacial Polymerization
1. Dissolution of a monomer A in the product to be encapsulated
In a stirring tank, this monomer mixture A is dispersed and the active ingredient is encapsulated in water.
The size of the droplets obtained is regulated by the speed of the stirrer.
2. Introduction into the stirred tank of a monomer B.
Monomer B is then introduced into the stirred tank. The monomers, which are small molecules, will form a polymer by chemical polymerization reactions.
3. The polymerization reaction
The polymerization reaction takes place by a chemical reaction which occurs between the monomers A and B. It is initiated by changes in PH (acids or bases are introduced) or/and temperature. It can be accelerated by the use of catalysts. The polymer formed is deposited around the drops which leads to encapsulation.
4. Stabilization of the polymer structure
The polymer is then consolidated by changes in pH or temperature or the addition of additives (crosslinking). This leads to better isolation of the encapsulated asset. The finishing operations are then carried out, they consist in adjusting the acidity of the medium, as well as the viscosity.