Preparation And Characterization Of Metolachlor Polyurea Microcapsule Suspension

Metolachlor is an amide herbicide.Its efficacy in farmland is easily affected by natural conditions such as sunlight,water and temperature,and its persistence is short.In this paper,the metolachlor was used as the core material,and the polyurea prepared from toluene 2-4 diisocyanate and EDA was used as the wall material.It is difficult to control the drug loading,release performance,appearance and thermal stability.This article discusses the effects of emulsifier types and dosage,emulsification stirring speed,curing time,curing temperature and ratio of core material to wall material on the methachlor-polyurea microcapsules.The scanning electron microscope,Fourier transform infrared spectrometer,ultraviolet spectrophotometer,and differential thermal analyzer were used to characterize the metolachlor polyurea microcapsules.The effects of different preparation conditions on the encapsulation efficiency,particle size and distribution,surface morphology and thermal stability of polyurea microcapsules were studied.On the one hand,the microcapsules are prepared by interfacial polymerization using metolachlor as the core material and polyurea prepared from toluene 2-4 diisocyanate and EDA as the wall material.In the amount experiment,when the styrene maleic anhydride copolymer was used as the emulsifier,and the amount was 4%,the prepared metolachlor microcapsule emulsion state was uniform and stable,and its encapsulation rate reached the maximum.The particle size of the polyurea microcapsules prepared at 2000 rpm was the smallest(9.42 μm).When the curing time is 2 h and the curing temperature is 50℃,the polyurea microcapsules are dried into a white powder without sticking.Under the light microscope,the metolachlor polyurea microcapsules are spherical without broken microcapsules.The size is relatively uniform and spherical,and the prepared polyurea microcapsules have high encapsulation efficiency and drug loading capacity.When the ratio of the core material to the wall material is 2/3,the particle size of the polyurea microcapsules is relatively uniform under the scanning electron microscope,which is spherical and has no dents or wrinkles on the surface.The distribution is narrow and the encapsulation rate is good(84.53%).On the other hand,urea was used in place of polyamine to modify the prepared metolachlor polyurea microcapsules,and the dense polyurea microcapsules were prepared.Urea,EDA and DETA were used in this paper.Metolachlor polyurea microcapsules were prepared from three water-soluble monomers and characterized by infrared spectrum analyzer,laser particle size distribution analyzer,differential thermal analyzer,ultraviolet spectrophotometer,and scanning electron microscope.The results show that polyurea microcapsules prepared using urea have the smallest particle size and excellent encapsulation efficiency.In addition,urea microcapsules have good compactness and thermal stability,and are scanned by SEM.The surface of urea microcapsules was observed under an electron microscope to be smooth,without cracking,and almost spherical.The results show that microcapsules prepared with urea have better heat storage properties and physical and chemical properties.