Anti‐solvent method synthesized phosphorylated microcapsules with flame retardancy and self‐healing analysis

Abstract

In this study, an anti‐solvent method is employed to encapsulate linseed oil (LO) into phosphorylated ethyl cellulose (P‐EC), successfully preparing microcapsules (LO@P‐EC). Scanning electron microscopy and Fourier transform infrared spectroscopy experimental results indicate the introduction of phosphoric groups into P‐EC, and the successful encapsulation of LO within the microcapsules, which are spherical with an average diameter of 145 μm. Hartmann tests reveal that the introduction of phosphate groups reduces the microcapsule flame propagation height by 43.75% and the average flame propagation speed by 55.67%. Thermodynamic analyses based on the Coats‐Redfern equation are performed to determine the changes in activation energy during thermal degradation. Furthermore, fitting analysis shows that the apparent activation energy of microcapsules with shell material of P‐EC significantly increases, confirming the evident thermodynamic inhibition of microcapsule deflagration by P‐EC. This is mainly attributed to the formation of a char structure by the P‐EC shell during combustion, which hinders the progress of the combustion reaction. When immersed in 3.5 wt% NaCl corrosive solution for 15 days, the microcapsule‐filled epoxy resin (LO@P‐EC/EP) coating exhibits excellent corrosion resistance, which is mainly attributed to the excellent self‐healing properties of the microcapsule core LO.