The Synthesis and Flame Retardance of a High Phosphorus-containing Unsaturated Polyester Resin

A high phosphorus-containing unsaturated polyester resin (P-UPR) was synthesized by a one-step or two-step method with dimethyl methylphosphonate (DMMP) as a reactive flame retardant. Phosphorus content in the cured P-UPR could be increased to 3.0 wt %, and a low amount of 15.0 wt % DMMP used in the reactants allowed P-UPR to achieve a UL94 V-0 rate. The incorporation of phosphorus into the UPR chain was confirmed by 31P NMR. The condensed phase flame-retardant mechanism of P-UPR was investigated by TG, SEM/EDS, and TG-FTIR.