Asian Journal ofChemistry

1. Asian Journal ofChemistry Vol. 19,No. I (2007), 187-194 Preparation and Characterization of Chemical Structure Composition of Polyurethane's l\licrocapsules Pesticides ABBAS AE:'.IADI Department ofScience,School ofCh~'1Iistry, Islamic A:ad University Karaj Branch, P.O. Box 31J35-313,Karaj, Iran .E-mail: abbas_ahmnd)_3957@yahoo.com Mictoencapsulation of pesticides lad other agrochemical com- pounds has been performed for sorr.cyears. In general, the object of producing such compositions h~ been to provide controlled releaseof the active in~redients and ;:articularlyto provide a release for longer term efficacy so that it is releasedover a period of time and is available throughout the effec::ve period. This is particularly significant for pesticides or other ing:edients,which are degraded or decomposedover a relatively sho~ ~riod of time or under certain environmental conditions. In generl1. microencapsulatedforms of pesticides are mostly produced by i::lerfacial polymerization and the microcapsule walls are formed frcm polymeric material. In this paper,we haveproduced the microca;:sulated form of chJoropyrifos (one of the high usagesolid phosphcrJs insecticides)and fenitroth- ion (one of the high usage liquid inse;:icides)in the lab and bench scale by use of interfacial polymer:z3tion by polyurethane. We changedsome of the conditions (tem;:crature,stirring rateand time) and found the better of them and also obtainedthe size of particles, the release of pesticides in a period of time, the graph of particle size distribution and the SEM images of particles. Key Words: Microencapsulation, ChJoropryros, Insecticide, Fenitrothion, Pesticide, Interfacial pol)1Derization. INTRODUCTION Controlled release polymeric systems are becoming increasingly important in a variety of agrochemicals like fertilizers, ins~cticides, fungicides and herbicides etc.. The macromolecular nature of these delivery systems allows for control of rate of ~elivery, mobility and period of effectiveness for biologically active components. The controlled release systems are better in enhancing the efficiency for application of agrochemicals2. Controlled release systems may be of two types: one in which the polymers are covalently bonded with the agrochemicals either as structural units along the black-bone or as pendant groups. Biological activity in these cases appears to be dependent upon cleavage of chemically labile bonds to release the free agrochemical or the active agenf. In the other agrochemical or any physiologically active agents are physically dissolved, adsorbed, entrapped or dispersed in a polymeric matrix. However, if the polymer