Preparation And Characterization Of Microcapsules Containing Avermectins And Chlorpyrifos

Due to the continuous enhancement of people’s awareness of environmental protection, lower pesticide toxicity, residual and safety, makes the traditional pesticide formulation such as:emulsifiable concentrate, powder, granule facing more and more using restrictions. Lower toxicity, properties of long-term release and environmental friendliness indicate the further development direction. Microcapsule technology is widely used in pharmaceutical area, in pesticide field it is just started, the commercialized products are also quite few. Compare whit traditional pesticide formulation, microcapsules have longer release period, higher rate of effective compound usage, lower rate of toxicity, decomposition and loss of active compound,.Avermectins has high killing activity of diptera, coleoptera, lepidoptera especially homoptera pests, but it has fast degradation by light. Chlorpyrifos is a new and effective organophosphorus pesticide without fumigation action, especially against nematode, but it has some side effects on human and animals, also with the unpleasant smell. If it is possible to make the tow pesticides as microcapsules with environmental friendly materials, it will not only increase the release date and also reduce the smell o and toxicity of pesticide.Based on the above, this thesis used a new cheap biodegradable material which was developed in1990s:poly butylene succinate (PBS) as the main loading material for pesticide microcapsules, and a widely used pharmaceutical material:poly lactic acid (PLA) as the modification material of PBS to encapsulate Avermectins and chlorpyrifos. Through the results of the effects on release date of preparation methods, screening of additives and formulations, material proportion, molar ratio of PBS and PLA, a better preparation system has been built. The main results were as follows:Microcapsules containing Avermectins based under the circumstance with preparation method of solvent evaporation, materials ratio of4:1, dichloromethane as organic solvent,3%PVA-1788as emulsifying agent, and the shearing speed of7000r/min, had clear and smooth surface, better dispersal condition, and the release date could last about30days.By this preparation system, used PLA as modification material to adjust the degradation rate of PBS by copolymerization to encapsulate Avermectins and chlorpyrifos under the mass ratio of1:29, also prepared the urea-formaldehyde(UF) resin microcapsules containing the same activities as comparing sample. The results showed that, the different mole ratio of PBS and PL A had a notable influence on degradation rate, whit increasing ratio of PLA the release date of microcapsules turned to be longer and longer, but it had insignificant effects on encapsulation and loading rates or diameters and dispersity. The average diameters were about5μm, the morphology, encapsulation and loading rates were much better than the microcapsules with loading material of UF. Considering the releasing properties and cost of loading materials, it is appropriate to set up the mole ratio of PBS and PLA as4:1-1:1, and the accumulation release dates were80%-90%, effective release period were35-42days.