| More and more attention has been paid to Suspension Concentrate(SC)for its safety,efficiency and environmental compatibility.It has gradually become one of the main development directions of pesticide formulations in the 21 st century.However,because the pesticide suspension concentrate is thermodynamically unstable heterogeneous dispersion system,some stability problems such as particle aggregation,Ostwald ripening,water analysis were easy to occur during the storage of the products,so it was needed to study these problems from both theoretical and productive practice aspects,to guide the development of pesticide aqueous suspension formulations.Azoxystrobin is a new and efficient broad-spectrum fungicide,and its single dosage formlations include Wettable Powder(WP),Water Dispersible Granule(WDG),etc.,but the systematic discussion of the furmolations screening for azoxystrobin is rare.In this paper,a series of research methods were used to prepare the suspension concentrations of 250 g / L azoxystrobin and 325 g / L benzoazepine ·azoxystrobin,the stability of the samples above during the storage process was also studied.The contents and results of this paper are as follows:1?The wetting and dispersing agents of azoxystrobin suspension concentration were screened by flow point method and Zeta potential.The optimal amount added of wetting and dispersing agents were determined by viscosity method.On this basis,combined with changes of the average particle size,suspension rate,viscosity and other physical and chemical properties,the optimum formulation of 250 g / L azoxystrobin suspension concentration was determined and as follows: Azoxystrobin was 23.5%(w/w),SD-811 was 2.0 %(w/w),Xanthan gum was 0.2%(w/w),ethylene glycol was 4.0%(w/w),magnesium silicate was 1.0%(w/w),silicone defoamer was 0.1%,sodium benzoate was 0.1%,deionized water to make up.After heat storage(54±2?)for 14 d,the suspension rate was over 93.0%,the decomposition rate of less than 5.0%,the suspension rate in three times hard water was more than 85.0%,other indicators were in line with the requirements of pesticide suspension concentration.2?The rheological properties of the azoxystrobin aqueous suspension were tested.The results showed that the samples with the addition of the wetting and dispersing agents had good viscoelasticity.It was proved that the wetting and dispersing agent was adsorptted on the surface of pesticide particles to form a diffusion of electricdouble layer which provided electrostatic repulsion and spatial resistance,thereby maintaining its physical stability of samples.3?The suspension concentration of 325g/L benzoazepine ·azoxystrobin was prepared by orthogonal design method.The optimum formulation was as follows: benzoazepine was 11.3%(w/w),azoxystrobin was 17.8%(w/w),SD-206 was 2.0%(w/w),ethylene glycol was 4.0%(w/w),xanthan gum was 0.2%(w/w),magnesium silicate was 1.0%(w/w),silicone defoamer AFE-1410 was 0.2%(w/w),sodium benzoate was 0.1%(w/w),water to make up.The results of suspension rate,dispersibility,stability for heat storage showed that the indexes of the samples were in accordance with the standard requirements of the suspension concentrate.4?The growth of microparticles from different formulations was studied,and the results showed that the growth mechanism of pesticide particles in different systems was different.In general,particle aggregation and Ostwald ripening existed at the same time,but in different systems,the importance of the effect was different,the growth of granules can not be roughly only due to particle aggregation or Ostwald ripening. |
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