Research Of Different Preparation Methods And Application Properties Of Pendimethalin Microcapsules

Pesticide microcapsules have become one of the hotpots of pesticide formulation research in recent years due to the characteristics of safe use,controllable release,long duration and high utilization rate.In this paper,based on microencapsulation of Pendimethalin,the interfacial polymerization method was used to prepare Pendimethalin microcapsules in intermittent and continuous mode,and the release rate and application performance of Pendimethalin microcapsules were further regulated by the surfactant.The main research contents are as follows:1.Research on preparation and properties of Pendimethalin microcapsules: the organic solvent-free Pendimethalin microcapsules were prepared by interfacial polymerisation using Pendimethalin as core material,4,4-methylenediphenyl diisocyanate(MDI)and ethylenediamine(EDA)as wall materials.In addition,the formulation was screened and the process conditions were optimized.The results showed that when the core-wall ratio in the oil phase was 100:5,polyvinyl alcohol was used as protective colloid with 4%,and SP-27001 was used as emulsifier with 6% in the water phase,the shear emulsification was performed at 65℃and 10000 r/min for 120 s,and the curing process was performed at 65℃ and 400 r/min for 4 h,the prepared Pendimethalin microcapsules had smaller particle size,higher encapsulation rate,uniform size distribution,good dispersion and stability.The process of Pendimethalin being coated by the formed polyurea capsule was a physical process,and all the test indicators of formulation were in accordance with the standards.2.Research on preparation and properties of Pendimethalin microcapsules by microfluidic technology: based on interface polymerization method,the continuous preparation of Pendimethalin microcapsules in a microchannel equipment was carried out by microfluidic technology with Pendimethalin as core material,4,4-methylenediphenyl diisocyanate(MDI)and ethylenediamine(EDA)as wall material.The results showed that Pendimethalin microcapsules prepared under the optimal conditions had a smooth surface,rounded shape,good monodispersibility and thermal stability,and encapsulation efficiency was as high as96.7%.Besides,the particle size and surface morphology of Pendimethalin microcapsules could be regulated by changing the flow rate of the continuous phase and EDA aqueous solution,respectively.The results of sustained release experiment showed that the release rate of Pendimethalin from microcapsules decreased with the increase of the flow rate of EDA aqueous solution,which were mainly caused by the significant differences in the surface morphology of microcapsules.The herbicidal activity test results showed that the microcapsules released at the appropriate rate could effectively control most grass weeds and broad leaf weeds while maintaining relatively slow release,which possessed a longer duration and better herbicidal effect than commercial Pendimethalin emulsifiable concentrate.3.Regulation of release rate and application performance of Pendimethalin microcapsules:the release rate and interfacial properties of Pendimethalin microcapsules were regulated by three different types and concentrations of surfactants,and the herbicidal activity was further verified.Through qualitative observation and quantitative test,it could be seen that SY-A0018 could greatly improve the release rate of Pendimethalin microcapsules,and the main release phenomenon was crystal precipitation,accompanied by the appearance of liquid spots.Through the test of contact angle,spreading,static surface tension and dynamic surface tension,it was found that SP-4026 SJ and 408 were stronger than SY-A0018 in regulating interface properties,reducing surface tension,promoting the spreading and wetting of microcapsule formulation.The experimental results of indoor pot and field test showed that the actual control effect of Pendimethalin microcapsule with SY-A0018 added was the best.The results above further verified that surfactant could regulate the release rate and interface properties of Pendimethalin microcapsules,and finally realized the regulation of the herbicidal activity and other application properties of Pendimethalin microcapsules by this way.