The Microencapsulation Of Three Different Pesticides And Research Of Their Controlled Release Properties

In this paper，three different pesticide delivery systems which contain Allyl isothiocyanate,chlorpyrifos, and thiamethoxam were built. According to the different physical and chemical propertiesof the active ingredients and different preparation process, the most appropriate conditions should bechoosed to prepare their microcapsule suspension. Some methods were used to Characterize themicrocapsules. The morphology and size distribution was detected by optical microscopy, laser particlesize analyzer respectively while IR spectra for the parcels and the adsorption state,and so on.Preparation conditions were optimized while building a pesticide delivery systems and their applicationperformance, slow release behaviors were also studied preliminary.1.Allyl isothiocyanate: using α-cyano-ethyl acrylate as capsule wall material, the Allylisothiocyanate microcapsule suspension was prepared by interfacial polymerization. The reaction canhappen at room temperature. The microcapsules made are round and uniform. Its sustained-releasecurve showed that the formulation of AITC CS has a significant persistence compared to the AITCtechnical. The microcapsule method applies to some volatile substances. Its preparation processoptimization test results: ethyl acetate as an organic dispersion medium selected Tween80as theaqueous phase emulsifier, while the oil phase adding an appropriate amount of emulsifier5030canensure the formation of microcapsules granules small; by orthogonal experiments, the AITC: theECA-use ratio5:1, the AITC: ethyl acetate-use ratio5:1, oil and water parcels1:1were the best ratiowhich can make sure high encapsulation rate and drug loading.2. Chlorpyrifos: the test used mulsion polymerization, methyl methacrylate as the capsule materialto construct the chlorpyrifos delivery systems. The different polymerization temperature were designedin order to study the affect on the mean diameter of microcapsule, and thus to study the influence ofparticle size on the release profile of the chlorpyrifos microcapsules. A qualified delivery systems, onthe one hand, the parcels must have a enough encapsule rate and drug loading to ensure theeffectiveness of drug delivery systems, on the other hand reported to ensure that the initial quantity ofadministration achieved to control pests and diseases in the dose needed. The results showed that: underthe test conditions, the formation of microcapsules morphology regular, encapsule rate and drug loadingare higher. Under the premise of maintaining the other conditions remain unchanged, to consider theinfluence of polymerization temperature on the microcapsules.The morphology and size distribution ofmicrocapsules were observed using optical microscopy and laser particle size analyzer. IRcharacterization results also show that under this conditions, chlorpyrifos has been wrapped in thecapsule material. Polymerization temperature of70°C and80°C, the average particle size of themicrocapsule suspension were3.75μm and5μm, encapsule rates were85%and87%, drug loading were24%and22.8%, respectively. Controling the polymerization temperature, the particle size of themicrocapsules formed by the polymerization temperature of70°C smaller than the polymerizationtemperature of80°C.The formation of microcapsules response to sustained-release curve is70°C polymerization temperature compared with80℃polymerization temperature,the release is faster.3. Thiamethoxam: Build thiamethoxam controlled release delivery systems in the same way withthe third chapter.Study the impact of sodium alginate on the formation of physical and chemicalproperties of the microcapsule suspension, the impact on the final release mechanism. The resultsshowed that: the adding of hydrophilic substances sodium alginate make the the viscosity of the entiresystem larger, and ultimately impacts the diameter of the microcapsules; the hydrophilic materialalginate make the system have rheological properties, the likely reason is that part of sodium alginate isin the aqueous medium outside the microcapsules, increasing the viscosity of the system; releasekinetics show that, the two thiamethoxam controlled release system,compared with the thanthiamethoxam technical, have significantly controlled release effect. But by adding sodium alginate therelease curves have significant differences which can be speculated that the sustained releasemechanism of the two microcapsule suspension wre different..Leaching experiment or semi-permeablemembrane release test all show that the sustained release curves of thiamethoxam by adding sodiumalginate microcapsule suspension below a curve of another controlled-release system, through a periodof time. after their release, will be higher than the curve of the controlled-release system withoutalginate. This shows that by adding sodium alginate, the structure of the capsule material were changed,parts of sodium alginate may be aggregated into the capsule wall material (methyl methacrylate) andbecome part of the capsule wall material.In addition, surface modification to achieve the controlledrelease microcapsule suspension and further research is needed.