Abstract: A novel char agent and flame retardant, caged-phosphate (trimer) was compounded with microcapsulated red phosphorus (MRP) and melamine (ME) as intumescent flame-retardant (IFR), which was used to prepare flame-retarded polyoxymethylene (POM). The flame retardancy was studied through vertical burning experiment, limit oxygen index, and thermal gravimetric analysis (TGA). Char residue collected after vertical burning was characterized by Fourier transform infrared spectroscopy (FTIR). And the mechanical properties of FR-POM were also studied. The results showed that there was a good synergistic effect between trimer and MRP. The trimer/MRP/ME flame-retarded POM achieves UL 94 V-0 rating, and limit oxygen index was up to 29.4 % with the loading of 23 %.

Key words: flame retardant, polyoxymethylene, caged phosphate, microcapsulated red phosphorus, char formation