Release behavior of oxyfluorfen polyurea capsules prepared using PVA and kraft lignin as emulsifying agents and phytotoxicity study on paddy

Polyurea microcapsules containing oxyfluorfen herbicide were synthesized by interfacial polymerization reaction between toluene diisocyanate and ethylene diamine at various core to shell ratios using green solvent N-N-dimethyldecanamide as carrier medium and using biodegradable PVA203S and Kraft lignin grade (varying molecular weight) as the emulsifying agent. The study was done to understand the effect of stirring rate on preparing microcapsules and find out how the process conditions changed the attributes of microcapsules such as particle size distribution, encapsulation efficiency and release kinetics. The formation of capsules was confirmed by FT-IR, SEM and TGA. The study indicated that the encapsulation efficiency decreased with increasing core to shell ratio. The change in release kinetics was based on the stirring rate and was dependent on the pH of release medium. Particle size distribution was influenced by the agitation speed during formation of emulsion. Kraft lignins of varying molecular weight were used to synthesize the polyurea capsules. It was found that capsules with high molecular weight lignin showed slow and sustained release. Synthesized polyurea capsules was subjected to safety study on paddy crop and compared with commercially available oxyfluorfen and was found to be safe for use on paddy crop.