A novel phosphorous-nitrogen structure containing intumescent flame retardant, 4,4-diaminodiphenyl methane bi(2,2-dimethyl-1,3-propanediol) phosphoramidate (DBDPP) was synthesized and characterized. Thermal stability and flammability properties of ethylene vinyl-acetate copolymer rubber(EVM)/DBDPP composites were investigated by thermogravimetric analysis (TGA), limiting oxygen index (LOI) test and UL-94 measurement, respectively. The results showed that the addition of DBDPP enhanced the thermal stability and flame retardancy of EVM significantly. The weight of residues improved greatly with the addition of DBDPP. SEM investigations revealed that a strong charred layer was formed from EVM/DBDPP composites during combustion. It is confirmed that the char structure was a critical factor for flame retardancy of EVM rubber. (c) 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012