Microencapsulation by In-Situ Polymerization

Microencapsulation by a polycondensation process, which may be either normal dispersion polycondensation or interfacial polycondensation, is especially attractive for liquid active agents. The important advantage of this method is that in most cases very high active agent loadings can be obtained. These methods are well reviewed by Arshady [6], and are discussed in detail elsewhere in this book. 

The microencapsulation method utilized is as follows. An oil phase containing a catalyst (1,4-diazobicyclo [2,2,2] octane), MCR, diol and crosslinker trimethylol-propane (TMP) is dispersed in paraffin oil containing a steric polymeric stabiHzer (poly(butadiene-b-ethylene oxide)) in a reaction kettle maintained at 35 °C. The emulsion is stirred at 1200 rpm and TDI is added dropwise to the reaction mixture. After stirring the system at a specific stirring rate and temperature, PU microcapsules are formed which are then isolated by filtering the mixture, washing with hexane, and drying under vacuum. 

Scanning electron microphotographs of microcapsules containing MGR, and those from which MCR has been extracted, are shown in figure 5.1. The micro- 

and the microencapsulation method follows capsule-forming interfacial polycondensation. 

A Hydrophobic polymer segment B Hydrophilic polymer segment 

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Materials Microencapsulated by In Situ Polymerization and Their Functionalities/ Applications... 

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