Preparation And Characterization Of Pesticide Sustained-release Microcapsules

Pirimiphos-methyl is a broad-spectrum and high-efficient organophosphorus pesticide,which is widely used to prevent and control of crop-storage pests and family-health pests.However,pirimiphos-methyl is volatile,sensitive to light and unstable under ultraviolet light.Microencapsulation of pirimiphos-methyl can help improve its stability and utilization,and reduce its inhalation toxicity,contact toxicity and phytotoxicity,thereby reducing its harm to humans and environment.Pirimiphos-methyl microcapsules with polyurethane as shell materials were successfully fabricated through the interfacial reaction between toluene diisocyanate(TDI)trimer and 1,4-butanediol.The particle size,morphology,pesticide loading,encapsulation efficiency,thermal stability and controlled release property of the microcapsules with different core wall ratio were analyzed by Fourier infrared spectroscopy,scanning electron microscopy,laser particle size analysis,high-performance liquid chromatography and so on.The results showed that pirimiphos-methyl was successfully encapsulated in polyurethane microcapsules and the microcapsules had regular spherical shapes and clean surface.The surface of the microcapsules became wrinkled and some small pores appeared when the core wall ratio increased to 15:6.The microcapsules could effectively protect pirimiphos-methyl against degradation at 35 ? and 45 ? for a long period.In addition,the microcapsules showed sustainable release for 40-80 hours in alcohol aqueous solution.Pirimiphos-methyl microcapsules with melamine resin as shell materials were successfully fabricated by in situ polymerization.The effects of pH and core wall ratio on the properties of microcapsules were fully investigated.The particle size,morphology,pesticide loading,encapsulation efficiency,thermal stability and controlled release property of the microcapsules were analyzed by Fourier transform infrared spectroscopy,scanning electron microscopy,laser particle size analyzer and high-performance liquid chromatography respectively.Results showed that when the pH of the reaction system is 5,microcapsules with regular sphere shapes and highest encapsulation rate can be obtained;The core wall of microcapsules ratio could affect the thermal stability of the microcapsules,the microcapsules could effectively protect pirimiphos-methyl against degradation at 35 ??45 ? and 55 ? when the pH of reaction system is 5 and the addition of melamine pre-polymer is greater than 14 g.In addition,the microcapsules showed sustainable release for 80-160 hours in alcohol aqueous solution.Pirimiphos-methyl microcapsules with silica as shell materials were successfully fabricated through interfacial hydrolysis and plycondensation of TEOS in O/W emulsion.The effects of sodium fluoride(NaF)and core wall ratio on microcapsules were investigated by Fourier infrared spectroscopy,scanning electron microscopy,laser particle size analysis,high-performance liquid chromatography and so on.The results showed that,the microcapsules have nearly spherical structure,considerable pesticide loading and entrapment efficiency when the amount of sodium fluoride is 0.2 g and the core wall ratio is within a certain range.The microcapsules can effectively protect pirimiphos-methyl against degradation at 35 ?,45 ? and 55 ?.In addition,the microcapsules showed sustainable release for 16 days in alcohol aqueous solution.