Microcapsules encapsulation physical method

Production of microcapsules is based on three main methods (24,25). The oldest, that of phase separation or coacervation, uses emulsification to produce core droplets containing the pesticide dispersed in an immiscible phase in which the wall material is dissolved but then precipitates around the core droplets. Interfacial encapsulation is done by emulsifying or dispersing the pesticide solution in a continuous phase and a polymerization reaction takes place at the interface. Finally, in the physical methods the wall material is spread around the pesticide containing core to make the microcapsule. 

There are two different ways to prepare microencapsulated PCM, the physical and the chemical method. Figure 8.4 shows the flowchart of these two different manufacturing techniques of micro-encapsulated PCM. Physical methods result in a relatively large size, and rough surface microcapsules compared to chemical methods [1,12], Among the chemical methods, better structure and smaller shell are obtained by the in-situ polymerization technique. 

Microcapsules are non-dense spherical shaped volumes. They are formed by a shell (polymeric wall in this case) with an empty volume inside that can be used to encapsulate compounds. The structure of the shell (a thin, dense layer, or a thick, porous layer, etc.), together with its nature (chemistry, material), determines the release rate of the encapsulated compound. There are several ways to obtain microcapsules. Some of these methods are based only on physical phenomena, certain are based on polymerization reactions and others combine both physical and chemical procedures. Most authors agree in classifying them all in two different groups chemical processes (like in-situ polymerization or desolvation in liquid media) and mechanical processes (e.g. spray drying or electrostatic deposition) [44]. A novel technology for microcapsule production, based on the employment of microdevices in continuous mode, has been presented [45]. Immersion precipitation is used in this case, in a way similar to that explained for flat membranes. 

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