Environmentally Friendly Polyurea Microcapsules of Pesticides by PVA Mediated Interfacial Polymerization
Microcapsules containing agrochemical pesticides used to control insects have attracted considerable interest for the last three decades in the search for reducing intrinsic toxicities, overconsumption, and ecological problems that have been caused generally by conventional pesticides. Biodegradable polyurea microcapsules containing pesticides such as ethyl parathion, benlate, and daconyl were prepared by the interfacial polymerization of polyisocyanate monomers with polyamines. In the process of microencapsulation with various emulsifying agents under the condition of high to medium concentration, polysulfonated emulsifiers such as lignosulfonate and styrenesulfonate sometimes failed to produce microcapsules because of random solidification of the aqueous mass leaving a serious problem of reproducibility. A protective colloid, polyvinylalcohol (PVA), was examined to prepare the stable high-concentrated emulsion under various conditions. Capsule slurry with 33% active ingredient was successfully obtained by the use of ca. 1% PVA as a protective colloid. In the case of the capsule with 42% active ingredient, the wall-forming reaction produced microcapsules, which turned out to be considerably coagulated or sometimes resulted in the failure of producing microcapsules. However, it was found that the mixed emulsifier of 10% of PVA and 90% of poly (sodium4-styrenesulfonate (PSS) produced stable emulsion and successfully led to microcapsules in high concentration under various conditions without any problems of reproducibility. The particle size distribution of the microcapsules was not much influenced by surfactants, and the size and distribution of the obtained microcapsules were directly affected by the agitation speed of emulsion.
Hyung Sun Kim, Yu Bao Li and Soo Wohn Lee
S. U. Paik "Environmentally Friendly Polyurea Microcapsules of Pesticides by PVA Mediated Interfacial Polymerization", Materials Science Forum, Vols. 510-511, pp. 678-681, 2006