Thermal degradation and flame retardancy of a novel methacrylated phenolic melamine used for UV curable flame retardant coatings

Methacrylated phenolic melamine (MAPM) was synthesized as a flame retardant multifunctional oligomer for UV curable systems, and characterized by FTIR, 1H NMR and elemental analysis. A series of formulations was prepared based on MAPM and a commercial UV curable epoxy acrylate EB600. Their thermal behaviours were investigated by thermogravimetric analysis, indicating that MAPM had no effect on the char formation of EB600. The flammability was monitored by the limiting oxygen index (LOI); the LOI value of EB600 increased from 21.5 for pure EB600 to 26.5 for the blend containing 50% MAPM addition. The “composite bar test” result showed that the vapour phase action flame retardant mechanism was the dominant mode for MAPM. The thermal degradation mechanism of MAPM was investigated by in situ FTIR, DP-MS and elemental analysis. The results showed that MAPM first degraded to form melamine at around 300 °C, which would further undergo condensation on heating with elimination of ammonia. Nitrogen underwent about 19% conversion to the residue and 81% had vapourized below 500 °C.