Preparation And Characterization Of Melamine Formaldehyde Resin Pyraclostrobin Capsule Suspension

Capsule suspensions have the following advantages over conventional formulations of pesticide,such as controlled release,high utilization,long effective duration,low toxicity,effective components stability,safe to user and environment,etc.The use of conventional dosage forms of pesticide,especially emulsifiable concentrates,cause a large amount of organic solvents to enter the environment,and resulted in environment pollution and resource waste.Microencapsulation of pesticides has a very important significance.This paper studied the preparation of capsule suspension of melamine formaldehyde containing pyraclostrobin using melamine formaldehyde resin as the wall material,pyraclostrobin as the core material via in situ polymerization method,and its preparation conditions have been further optimized.Which will provide theoretical guidance for microencapsulation of pyraclostrobin and other pesticides,and main contents is as the following aspect:1.Selected a variety of organic solvents as the core material alternative solvent and prepared capsule suspension of pyraclostrobin,respectively.Methylbenzene was chosen as final solvent of pyraclostrobin by comparing the particle size and distribution of microcapsules.2.The molar ratio of formaldehyde / melamine(F/M)screening and through the microcapsule particle size and distribution and microcapsule morphology selected the best molar ratio,the final determination of molar ratio of F/M is 3-3.5 and the prepared microcapsule particle size distribution is concentrated,the capsule appearance is good.3.By comparing the effect of different emulsifiers on the emulsification of pyraclostrobin and the amount of pyraclostrobin on the microcapsules,the optimum emulsifier Tween 80 was determined,which was 4%.4.The shear rate can have an effect on the particle size of the microcapsules.Experiments show that when the shear rate is 16000 rpm,the size of the obtained microcapsules is uniform.5.Curing time and curing temperature can seriously affect the capsule wall formation of microcapsules and screen the curing time and curing temperature,respectively.The results show that the microcapsule wall has good mechanical strength when the curing temperature is 60?;and the encapsulation efficiency of the prepared microcapsules is high when the curing time is 120 min.6.By comparing the effect of different wall-to-core ratio on the microcapsules,the optimal ratio of wall material to core material is 1.7.The prepared microcapsules were characterized by scanning electron microscopy,laser particle size analyzer,Fourier transform infrared spectroscopy,UV spectrophotometer,Thermogravimetric Analysis.The results show that the melamine-formaldehyde resin can be coated with pyraclostrobin well,and the obtained microcapsules have good external morphology,concentrated particle size distribution,high encapsulation efficiency and good thermal stability.8.The release experiment of the microcapsules in water shows that the microcapsules can release continuously for about 20 days.In the water can be slowly released.