Sustained-release Kinetics and Preparation Process Optimization of Chlorpyrifos/Urea-formaldehyde Resin Microcapsules

With people's increasing awareness of environmental protection and health, low efficiency, large dosage and residual problems caused by widespread use of pesticides were concerned extensively. Pesticide microcapsules has shown lots of benefits to help improve the utilization rate of pesticide and achieve other aims as well. Using urea-formaldehyde resin as wall material and chlorpyrifos (CPS) as core, the chlorpyrifos/urea formaldehyde resin microcapsules (CPS/UFMCs) was fabricated by in-situ polymerization. The effects of emulsifier sorts and dosage, pH, acidification time on particle size and distribution of chlorpyrifos/urea-formaldehyde microcapsules (CPS/UFMCs) were studied, and the optimal process of CPS/UFMCs preparation was obtained. Moreover, the release performance and kinetics of the CPS/UFMCs prepared by optimal process was carried out to further investigate the loading capacity of microcapsules, encapsulation efficiency and release kinetics. The results showed that CPS/UFMCs had a narrow particle size distribution and a small average size with 3wt% sodium dodecyl sulfate(SDS) as emulsifier, the acidification time of 90 min, pH of 2.5, core/wall ratio of 1:3 and curing temperature of 60℃. In addition, the average size of CPS/UFMCs prepared with the optimization process was around 113 μm. Meanwhile, the CPS/UFMCs showed excellent loading performance with more than 62% CPS encapsulated and the CPS loading rate was more than 53%. Moreover, the investigation of release performance showed the chlorpyrifos was released sustainably from the CPS/UFMCs, and more than 90% of the CPS encapsulated was released within 10 days. Subsequently, the release kinetics was analyzed following mathematical models of Korsmeyer-Peppas equation and Higuchi equation. In the kinetic study, the results showed that the release process of CPS/UFMCs followed a Fick diffusion mechanism. Generally, the prepared CPS/UFMCs shows high drug loading, efficient encapsulation and excellent release performance, and can be further developed as a new type of pesticide formulation, which can provide theoretical support and practical reference for the development of new formulations of sustained-release pesticide. © 2018, Materials Review Magazine. All right reserved.