Preparation And Characterization Of Pla Modified Pu Microcapsules For Controlled Release Of Chloropyrifos

Overuse of pesticides due to their loss and degradation results in a large waste and serious ecological problems.Pesticides microcapsule of biodegradable materials is a feasible formulation to develop environment-friendly and efficient controlled-release delivery system.It can maximize the pesticide efficacy,achieve long-lasting insecticidal,reduce the use of organic solvents and pressure on the environment.The preparation of biodegradable pesticide microcapsules is a hot spot in the research of pesticide formulation.In this study,Polyurethane(PU)modified with polylactic acid(PLA)microcapsules were fabricated for controlled release of Chloropyrifos(Cp,one of the high usage solid phosphorous insecticides)via interfacial polymerization method using MDI50,N306,1,4-butanediol(BDO)and PLA serve as modifier.The preparation technology of microcapsules was determined by single factor experiment to evaluate the morphology,particle size and distribution of microcapsules,the encapsulation efficiency and loading content.The effects of solvent system,soft segment,pre-polymerization time,the concentration of wall materials,core/shell ratio,emulsifying speed,chain extend time,concentration of emulsifier on the formation of emulsion and microcapsules were studied,and characterized by FTIR,TG-DSC,SEM,GSD and HPLC.The release performance of these microcapsules were also studied.The results showed that spherical microcapsules were prepared using n-butyl acetate as solvent and polyether triol as soft segment,diameter of that were 1～10 μm.The encapsulation efficiency and loading content of microcapsules can reach up to 71.0%and 26.2%respectively under the optimum condition.FTIR indicated that PLA had successfully participated in the interfacial polymerization of polyurethane.And the thermal stability of polyurethane was improved due to the addition of PLA.According to the results of release experiments,the microcapsules exhibited a sustained release period above 60 days.The particle size,drug loadings and introduce of PLA influenced the release behavior of microcapsules.Combining PLA into the soft segment of PU has proved to improve the degradation of PU shell and accelerate the release of chlorpyrifos,changing the release mechanism to be the coupling of diffusion and corrosion.