Preparation And Characterization Of The Pyraclostrobin Microcapsule Suspension Formulation

Microencapsulated pesticides not only have potential for prolong controlling release of pesticide aim at reducing pesticide residues in our environment, but also possess some advantages such as improving using efficiency, abating toxicity and harmfulness, reducing environment pollution.So in recent years, it have attracted quite a bit of pesticide fields attention.Pyraclostrobin have a very good market potential and broad application prospects because of its strong advantages, such as low toxicity, environmental protection and safety. Currently, there are various dosage forms of pyraclostrobin in the market, like emulsifiable concentrate, wettable powder, water dispersible granule except for the dosage form of pyraclostrobin microcapsule. So develop the pyraclostrobin microcapsule possessing environmental friendly, slow-release, excellent comprehensive properties becoming a development trend in the future market.In this study the microcapsule were prepared by using pyraclostrobin as core material and urea-formaldehyde resin as wall material by in situ polymerization method. The laboratory technology conditions,such as different types of solvents、different types of emulsifiers、different use level、reaction mechanism of SMA emulsifiers、pH of SMA emulsifiers 、mass of core/shell ratio and curing stage including the stirring speed、curing temperature 、curing time were main studied to obtain optimum choice.(1) According to the different boiling point of solvent, and the maximum solubility of pyraclostrobin was studied. Results indicated that toluene was the best choice.(2) By the scanning electron microscopy(SEM) micrograph, the effects of different types of emulsion on properties of microcapsule were investigated and found that a complex of Tween80 and SMA as emulsifiers were the best available option compared to single emulsifier of SDS or Tween80.(3) It was demonstrated the optimal amount of SMA and Tween80 compound emulsifiers was 4g by using laser particle size analyzer and optical microscopy, because the microcapsule prepared with uniform particle diameter,good dispersion and perfect morphology.(4) By the surface tension meter and viscosimeter The relationship between pH of SMA emulsifier and surface tension, viscosity of the emulsion were investigated and found the most suitable pH value of SMA was 5.5-6.(5) By ultraviolet spectrophotometer(UV), laser particle size analyzer, the effects of different mass of core/shell ratio on the properties of pyraclostrobin microcapsule were analyzed. Result indicated that when the mass of core/shell ratio of 1.2/1, preparation of microcapsule with high encapsulation efficiency and better particle size.(6)The effects of several encapsulating parameters in curing stage including the stirring speed, curing temperature, curing time were investigated by ultraviolet spectrophotometer(UV), laser particle size analyzer and optical microscopy. It had been found that curing temperature under 60 °C and at the stirring speed of 600r/min lasted 90 min will provide a good foundation for the preparation of microcapsule with high encapsulation efficiency,good morphology and mechanical strength.