Preparation of microencapsulated nitrogen‑phosphorus‑silicon flame retardant and its effect on high impact polystyrene flame retardancy

High-impact polystyrene is a widely-used construction material due to its superior comprehensive performance, but its susceptibility to fire can lead to the production of toxic and harmful gases. To address this issue, a novel, environmentally-friendly microencapsulated nitrogen‑phosphorus‑silicon flame retardant for high-impact polystyrene was prepared in this study. SiO 2 , produced by the hydrolysis condensation of tetraethyl orthosilicate , was used as the wall material, while melamine cyanurate was used as the core material. The microencapsulated nitrogen‑phosphorus‑silicon flame retardant was compounded with high-impact polystyrene and aluminum hypophosphite , and the composites were evaluated for their performance in terms of fire behavior, thermal stability, and morphology of the resulting carbon residues. When melamine cyanurate@SiO 2 and aluminum hypophosphite were added in a 1:4 ratio, the UL-94 rating of L5 reached V -0, and the LOI value increased to 27.0%. The conical calorimeter test results showed that the peak heat release rate of the L5 composite decreased by 78.7% compared to pure HIPS, and the corresponding total heat release rate decreased by 45.7%. Thermogravimetric analysis results illustrated that the amount of carbon residue increased significantly, from 2.46% to 22.26% of pure high-impact polystyrene. These findings indicate that the prepared microencapsulated nitrogen‑phosphorus‑silicon flame retardant is multifunctional, highly efficient, and can be applied to high-impact polystyrene.