A study of the physical strength of fenitrothion microcapsules

Fenitrothion, a widely used organophosphorous insecticide, was microencapsulated with polyurethane via an interfacial polymerization method, and the relationship between the formulation factors, such as mass median diameter (D) and wall thickness (T), and the physical strength of the microcapsules was studied. It was found that the larger the ratio DT, the smaller the pressure per capsule required to break 50% of microcapsules (P50). This result agreed with the theory of the destruction of an empty sphere with a thin wall. Moreover, the result obtained by the physical breaking test coincided with that obtained by the breaking test of microcapsules by cockroaches.