Characterization of Microcapsules Prepared by Interfacial Polycondensation of Methylene Bis(phenyl isocyanate) with Hexamethylene Diamine

Polyurea microcapsules containing 2-chloro-N-(2,6-diethylphenyl)-N-(methoxymethyl)acetamide as the active agent were prepared by the method of interfacial polycondensation with methylene bis(phenyl isocyanate) as the multifunctional isocyanate, hexamethylene diamine as the diamine, and anionic sodium lignin sulphonate as the emulsifying agent . Thermal stability of the microcapsules was investigated with a thermogravimetric analyzer coupled to a mass spectrometer and surface topography of the micro-capsules was investigated with atomic farce microscopy. The release behaviour of the microcapsules was studied by extraction in deionized water or calcium chloride aqueous solution, drying under ambient conditions, and examining with scanning electron microscopy. Results indicate that as calcium chloride is added to the aqueous suspension of microcapsules containing anionic sodium lignin sulphonate as the surfactant, a gel phase is formed. This gel phase encompasses the microcapsules and increases the stability and modifies the release behaviour of the microcapsules.