Study On Synthesis Conditions Of Pyraclostrobin Polyurethane Microcapsules

Pyraclostrobin is a new broad-spectrum fungicide developed by Badiska Aniline and Soda Fabric,which can inhibit mitochondrial respiration.Pyraclostrobin has been used to control several destructive diseases caused by Alternaria,Septoria,Phytophthora,Rhizoctonia,Pythium,Aspergillus and Pseudomonas.Due to its high toxicity to aquatic organisms,The use of rice fields is very limited,so the use of microcapsule of Pyraclostrobin Therefore it is important to research.In this thesis,micro-capsule polyurethane suspension is prepared by cross-linked polymerization,the core of the capsule is pyraclostrobin,and the wall of the capsule is polyurethane.Discuss the effect of different solvents,type of emulsifier,quantity,curing temperature,stirring speed and time on the performance of the microcapsules.(1)By screening the influence of different emulsifiers on the stability of the emulsion,the nonionic emulsifier alkylphenol polyoxyethylene ether(NP-10)has the best emulsion stability.After six hours,there is no precipitation and no delamination.The optical microscope and laser particle size analyzer were used to investigate the correlation between the size distribution of the microcapsules and the amount of emulsifier.When the dosage is 4%,the diameter of the microcapsule particles is uniform and the distribution is best.(2)The PU segment is synthesized with isophorone diisocyanate(IPDI)and polyethylene glycol(PEG),and different types of curing agents(respectively 1,4-butanediol,glycerol,and triethanolamine)are used for chain extension.Obtain microcapsules with different properties.Through optical microscope,scanning electron microscope,laser particle size analyzer,ultraviolet spectrophotometer and other means,the morphology,particle size,drug loading,encapsulation efficiency and release performance of the microcapsules were analyzed,and the release kinetics was analyzed.The study found that the prepared microcapsules are all spherical,and the microcapsules prepared with triethanolamine as the chain extender are significantly better than 1,4-butanediol and glycerol in morphology(SEM),and the encapsulation efficiency and loading The amount of medicine is higher,84.2% and 21.5% respectively.The sustained-release kinetics study of the three types of microcapsules found that the microcapsules prepared from triethanolamine conform to the Rigter-peppas model,while the microcapsules prepared from 1,4-butanediol and glycerol conform to the firstorder kinetic model.(3)The effect of different molecular weight PEG as the soft segment on the properties of polyurethane microcapsules was studied.The results showed that the prepared polyurethane microcapsules were all spherical with good dispersion and no obvious agglomeration.As the molecular weight increases and the particle size increases,the encapsulation efficiency of PEG400 and PEG1500 has good drug loading(76.2% and 84.6%),while the sustained release performance of PEG400 is better.All four types of microcapsules conform to the first-order kinetic model.