Interaction between magnesium hydroxide and microencapsulated red phosphorus in flame-retarded high-impact polystyrene composite

摘要

High-impact polystyrene (HIPS) flame retarded by magnesium hydroxide (MH) alone or in combination with microencapsulated red phosphorus (MRP) was prepared by melt compounding, and the interaction between MH and MRP was investigated by limiting oxygen index, UL-94 vertical burning test, cone calorimeter test, X-ray diffraction, thermal analysis, and scanning electron microscopy. Obvious synergism between MH and MRP on the flame retardancy of HIPS is found. The introduction of a small amount of MRP can accelerate the endothermic degradation of MH apparently at high temperature both in air and in nitrogen. Phosphoric acid (H3PO4) derivatives are produced in situ by the MH/MRP mixture upon thermal degradation in both atmospheres, which can act as char-forming agents and promote charring of the polymer upon burning. The burnt residue of the HIPS/MH/MRP composite is composed of a tiny amount of crystalline MgO, noncrystalline black char, and a series of noncrystalline phosphorus-containing magnesium phosphate compounds.