| Microencapsulation is an important technology of production in pesticide formulations. Comparing with conventional pesticide formulations, it has many advantages, such as extending of persistence, reducing of environmental pollution and toxicity, reducing the decomposition rate and good efficiency. In recent years, more and more attention is paid to it. Emamectin benzoate is a super-efficient, broad-spectrum, low toxicity, pollution-free insecticide and miticide,and widely used in pest control in agriculture. However,many factors such as ultraviolet radiation, air temperature and soil environmental can promote its decomposition,which limit the use of emamectin benzoate and efficacy. Emamectin benzoate microcapsules can avoid forenamed problems. In this study,Using formaldehyde and melamine as wall materials and emamectin benzoate-toluene as core material, microcapsules were prepared by in-situ polymerization. It was studied that how the factors: mass ratio of melamine to formaldehyde, wall material corresponding conditions, emulsifying, stirring ratio and time, pH value and temperature had an influence on the properties of microcapsules. Photodegradation of emamectin benzoate microcapsules was studied. Using different viscosity average molecular weight of hydroxyethyl cellulose as emulsifier, microcapsules containing emamectin benzoate are prepared by in-situ polymerization. The factors affecting the surface morphology, the particle size and distribution, the encapsulation efficiency and the drug loading was investigated, and the release properties were determined.Encapsulating parameters: Mass ratio of melamine to formaldehyde was 1 to 2, core to wall was 3 to 2, o/w emulsion of 5.0 gram toluene and 2.5 gram emamectin benzoate in HEC aqueous solution was prepared. Using 1% HEC as emulsifying agent, at the stirring ratio 1000r/min, acidifying for 70min, pH value was 5.0, keeping the temperature at 50℃for 2 hour, could prepare microcapsules with good surface morphology and uniform particle size range. Fourier-transform infrared spectroscopy (FT-IR) showed that emamectin benzoate had been encapsulated with wall material. The sustained-release characteristic was well by using UV spectrophotometer. The time of sustained-release could be up to 15 days. Photodegradation experiment showed that photodegradation was decreased. After irradiation by UV light,photodegradation ratio of emamectin benzoate technical material was 57.4%,and microcapisulazed emamectin benzoate was 21.5%.In these Microcapsules with different viscosity average molecular weight HEC, the morphology of the microcapsules made by small molecular weight hydroxyethyl cellulose was rule, dense and had no adhesion phenomenon. The microcapsules particle size and the size distribution increased with the viscosity average molecular weight of hydroxyethyl cellulose increasing. The average particle size of microcapsules was 5.70μm by using HEC with viscosity average molecular was 90000. Drug loading and encapsulation efficiency was significantly affected by using HEC with different viscosity average molecular. With the viscosity average molecular weight of hydroxyethyl cellulose increasing, the encapsulation efficiency and the drug loading were decreased. Microcapsules using viscosity average molecular was 90000 had the greatest encapsulation efficiency and drag loading,respectively 84.03% and 23.46%.It was showed that the release performance of the microcapsules which prepared by small molecular weight hydroxyethyl cellulose were better. Accumulative release rate of microcapsules using viscosity average molecular was 90000 and 250000 was better than microcapsules using viscosity average molecular was 720000 and 1300000.The results of field trial indicted emamectin benzoate 3%CS had good control effect. The results showed that the rapid effect of CS was less than EC.After using 14 days, controlled release properties of CS took effect. The control effect of CS was better than EC after 21 days. The suitable dosage of 3% emamectin benzoate CS was 6g/mu.
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