Preparation And Characterization Of Melamine Formaldehyde Resin Propisochlor Capsule Suspension

Pesticide capsule suspension is regarded as a green environmentally friendly formulation.Propisochlor is a pre-emergent herbicide of the amide.The efficacy of propisochlor was influenced by the degradation and the drift risk.The preparation of pesticide capsule suspension by in situ polymerization of melamine formaldehyde resin has received sustained attention owing to its cost advantage,however,the particle size,encapsulation efficiency,loading capacity,release performance and thermal stability of the products are really difficult to control.Therefore,it's meaningful to conduct researches on the preparation of pesticide capsule suspension based on melamine formaldehyde resin.In the paper,the melamine formaldehyde polymer was used as the wall-forming materials,and the technical propisochlor was used as the core material.The microcapsule suspension was prepared by in-situ polymerization.The synthesize microcapsules were characterized by FTIR,SEM,UV,TGA and particle size analyzer.The preparation conditions were optimized in the process of preparation,and theoretical reference was provided for the industrial production of the melamine formaldehyde resin microcapsule suspension of propisochlor.The main results as follows:The molar ratio of melamine/formaldehyde(M/F)influences the structure of melamine formaldehyde resin.The microcapsules with different monomer ratios were characterized.The results showed that the surface morphology and encapsulation efficiency of the microcapsules were the best in the condition of 1/4.In the selective experiment of the type and amounts of emulsifier,the results showed that Tween80 has the best emulsifying effect to propisochlor,and the emulsion had best stability.When the quantity of emulsifier was 6%,the prepared microcapsules possessed the highest encapsulation efficiency(90.6%).The selecting experiment of shear speed.The results showed that the shear speed was set to D(19,000 rpm),the emulsion had best stability,and the microcapsules had a highly centralized particle size distribution and smaller particle size.In the curing temperature and curing time experiments,it was found that only under the curing temperature of 60?,the prepared microcapsule shell had the best mechanical elasticity and strength,and did not adhesion after drying and became powdery.Under the condition of curing time of 2 h,the prepared microcapsules had the highest encapsulation efficiency.The results of core/wall showed that the value of core/wall was 1/1,the prepared microcapsules had the smallest particle size,the narrowest distribution of particle size.The microcapsule surface was smooth and the microcapsules had no adhesion.FT-IR analysis of the prepolymer,wall material,microcapsule and propisochlor showed that the technical propisochlor was encapsulated by melamine formaldehyde resin perfectly.The thermogravimetric analysis of microcapsules showed that the core material was encapsulated by wall-forming materials and melamine formaldehyde resin had better thermal stability than technical propisochlor.The microcapsules had higher thermal stability.From the curve of the release of microcapsule based on melamine formaldehyde resin,the prepared microcapsules could be continuously released for one month,prolonging the persistence of propisochlor and achieving the purpose of controlled release effectively.