Preparation of sustained-release chlorpyrifos particles via the emulsification coacervation method and their sustained-release performance

MMA-HEMA-MAA ternary random copolymer (PA) and CaCl2 was used as carrier and precipitant, respectively, and emulsification coacervation was adopted to prepare sustained-release chlorpyrifos particles. The particle size, morphology, structure, and the sustained-released performance of the samples were characterized. Results showed that porous and random sustained-release chlorpyrifos particles piled up into small spherical particles. Hydrogen-bonding interactions between PA and chlorpyrifos molecules were observed, and chlorpyrifos was dispersed among the PA molecules as both crystal and noncrystal forms. Raising chlorpyrifos concentrations resulted in larger proportions of chlorpyrifos distributed in the crystalline state. Chlorpyrifos was loaded into the PA crosslinked network structure and the heat resistance of the pesticide was improved significantly. The sustained-release process of chlorpyrifos was controlled by Fick diffusion mechanism, and the release mechansim of the drug consisted with the Korsmeyer-Peppas kinetic equation.