Abstract: Three caged phosphate (trimer) microparticles were mixed magnesium hydroxide (MH), aluminium hydroxide (ATH), and silicon dioxide, and formed three composite flame retardants. The trimer was also encapsulated with above inorganic substances, which formed three capsule flame retardants. The flame retardancy of the two types of flame retardants in epoxy resin(EP) was compared in terms of limiting oxygen index, vertical burning tests (UL94), and thermal gravimetric analysis (TGA). It showed that the function provided by the blends was better than that of the capsules. The epoxy resin loaded with 20 wt% flame retardant (17 %trimer and 3 % inorganic substance) gave rise to limiting oxygen index to 32 %, and UL94 reach V0 rating. Whereas those based on the same loading of capsules were only 24 % and UL94 V2.

Key words: flame retardancy, caged phosphate, inorganic flame retardant, microparticle, thermal resistance