Studies On The Pesticide Microcapsule Based On The Biodegradable Material Carrier

With increasing environmental awareness of people and constant attention to food security, higher demand on toxicity, security and residueal effect of pesticide is proposed.Thus, toxicity reduction and environmental compatibility of pesticide become hot spot of current pesticide application research.Chlorpyrifos is one of the broad-spectrum organophosphorus insecticide with medium toxicity and also one of the top five insecticides used worldwide. With disadvantages of easy photolysis, short residual activity and phytotoxicity to sensitive crops, wide attention has been aroused on improvement of chlorpyrifos residual activity and utilization rate as well as reduction of its environmental risk and photolysis.With favourable biocompatibility, biodegradability and innocuity, aliphatic polycarbonate and polylactic acid have become one of the wide concerned carrier materials of controlled release formulations and been used widely medicine field.Therefore, relevant research on degradable chlorpyrifos controlled release formulation is undoubtedly hot spot and leading edge of pesticide preparation process.With aliphatic polycarbonate and polylactic acid as carrier and microcapsule technology, controlled release of chlorpyrifos was realized in this study.In this paper, relevant study on synthesis of poly(propylene carbonate), preparation of PPC-chlorpyrifos microcapsule and effect of polylactic acid with different molecular weight on microcapsule performance were conducted.The main results were as follows:With CO2as raw material, double metal cyanide complexes (DMC) as catalyst, bipolymer of CO2and epoxypropane was synthesized by anion coordination method.The structure of PPC was characterized by FT-IR,1H-NMR and13C-NMR, then its degradation character was determined simulated soil environment eaperiment. Molecular structure of PPC was confiemed through analysis of FT-IR,1H-NMR and13C-NMR, and PPC was mainly jointed by H-T syndeton. The degradation test showed that PPC was biodegradable and SEM observation showed that many micropores appeared when PPC was degraded in soil mineral salt solution for8weeks.With PVA-1788as stabilizer, PPC-chlorpyrifos microcapsule was prepared by emulsion solvent volatilization method.Chlorpyrifos microcapsule was charactered by scanning electron microscope,optical microscope,high performance liquid chromatography,wide angle X-ray diffraction and laser zetasizer.The results showed that PPC-chlorpyrifos microcapsule sphere was regular and the surface was smooth.Average particle diameter was7.3μm and druglording rate and encapsulate rate were respectively16.75%,89.34%.Study on release effect showed that PPC-chlorpyrifos microcapsule had significant controlled-release effect and release of chlorpyrifos could be divided into early rapid-release stage and later controlled-release stage.PPC had the potential to become a new carrier material for controlled release, which provided basis for application of biodegradable material.With three Poly-D,L-lactide acid (PDLLA) of different molecular weight as capsule material, PVA-1788as stabilizer, PDLLA-chlorpyrifos microcapsule was prepared by emulsion solvent volatilization method.Performance of PDLLA-chlorpyrifos microcapsule was charactered by scanning electron microscope,optical microscope,high performance liquid chromatography and laser zetasizer. Simultaneously, controlled-release character of PDLLA-chlorpyrifos microcapsule was probed by column chromatography.The results showed that when concentration of PVA-1788was1.25%, volumn ratio of continuous phase and organic phase was4.5, weight ratio of PDLLA and chlorpyrifos was2:1, microcapsule with regular sphere and small diameter could be obtained.Molecular weight of PDLLA had no significant effect on appearance, diameter,distribution, druglording rate and encapsulate rate of microcapsule.Study on microcapsule release effect showed that all three PDLLA microcapsules had significant controlled-release effect.Accumilated release of PDLLA1, PDLLA2and PDLLA319day later were respectively65.64%,88.76%and76.74%, among which PDLLA1-chlorpyrifos microcapsule with lower molecular weight had the fastest releasing speed.