| Fosthiazate is a kind of pesticide with significant control effect on root-knot nematodes.It still has problems of short duration,improper operation will inhibit crop growth or burning seedlings,and long-term use will easily cause pest resistance.Microencapsulation and compounding of pesticides can avoid their shortcomings.Based on this,this article prepared 4% fosthiazate microcapsule suspension and 5%avermectin and fosthiazate complex microcapsule suspension by interfacial polymerization method,prepared 10% avermectin and fosthiazate complex microcapsule by solvent evaporation method.Based on the particle size and encapsulation rate,the effects of factors such as shear rate,shear time,emulsifier,dispersant,and amount of wall materials were investigated to optimize the preparation process of microcapsules.The microcapsules were characterized by particle size distribution,optical microscope,scanning electron microscopy,infrared spectroscopy,encapsulation rate and drug loading.At the same time,the paper also studied the microcapsules’ suspension rate,slow release,photodegradation and other properties.The work of this paper is summarized as follows:1.4% fosthiazate microcapsule suspension :4% fosthiazate microcapsule suspension was prepared by interfacial polymerization.The experimental results showed that:(1).With Nong Ru 600~# as the emulsifier and NNO as the dispersant,the prepared microcapsules had uniform particle size and good dispersion;(2).Ethylenediamine is selected as the polymerization monomer for TDI,and the encapsulation efficiency of the obtained microcapsules is higher than that of ethylene glycol and polyethylene glycol 600,and the morphology is better;(3).The ratio of the best reacting substance of ethylenediamine and TDI is 1:1;(4).Under the shear condition of 19000/5.5(rpm/min),the core wall ratio varied from 3:2 to 2:3,and the encapsulation ratechanged from 26.80 to 77.97%;(5).As the shearing time is longer and the shearing speed is higher,the particle size of the microcapsules can be smaller,and the microencapsulation rate is reduced;(6).The sustained release of microcapsules is slower than that of the original fosthiazate and 20% fosthiazate water emulsion.Slow release performance is affected by factors such as different particle size,different core wall ratio,different pH,etc.(7).Compared with 85% fosthiazate original drug and20% fosthiazate water emulsion,4% fosthiazate microcapsule suspension has better UV shielding performance.2.5% avermectin and fosthiazate complex microcapsule suspension:With fosthiazate and avermectin as core materials,toluene diisocyanate(TDI)and ethylene diamine as reaction monomers,xylene as solvent,NongRu 600~# as emulsifier,NNO as dispersant,and 5% avermectin and fosthiazate complex microcapsule suspension was prepared by interfacial polymerization method.The results show that:(1).The average particle size of the microcapsule is 6.095 μm,which is nearly spherical,indicating smoothness.The encapsulation rates of avermectin and fosthiazate reach 99.51% and 80.86%,respectively,and the drug loading is 1.03% And 4.02%,the suspension rate is 85.43% and 97.74%;(2).Compared with 85% fosthiazate original drug,20% fosthiazate water emulsion,1.8%avermectin EC and 3% avermectin water emulsion,the complex microcapsules have better sustained-release performance and UV shielding properties.3.10% avermectin and fosthiazate complex microcapsules:Using solvent volatilization method,with particle size and encapsulation rate as the main indicators,optimize the experimental conditions,and characterize by particle size distribution,SEM,infrared spectroscopy,10% avermectin and fosthiazate complex microcapsules were prepared,And the slow release and photodegradation experiments of the microcapsule were investigated.(1).The experimental optimization conditions are determined as follows: shear speed is 8500 rpm,shear time 3.5 min,2% PVA,core wall ratio 1: 5.5,1.5% NaCl,45 mL dichloromethane.The experimental results show that the average particle size of the optimized avermectin and fosthiazate complex microcapsules is 16.75 μm,and the encapsulationrates of fosthiazate and avermectin in the microcapsules are 60.37% and 98.71%.The drug loading was 7.29% and 3.43%;(2).Compared with 85% fosthiazate original medicine and 20% fosthiazate water emulsion,1.8% avermectin emulsifiable concentrate and 3% avermectin aqueous emulsion,the compound microcapsules have better release performance and UV shielding properties. |
