Novel Nitrogen–Phosphorus Flame Retardant Based on Phosphonamidate: Thermal Stability and Flame Retardancy

[Image: see text] A novel nitrogen–phosphorus flame retardant (P–N FR) based on phosphonamidate, dimethyl N,N′-1,3-phenylenebis(P-methylphosphonamidate) (DMPMP), was successfully synthesized and its flame-retarding performances and thermal degradation were compared with those of other P–N FRs and a phosphorus-based FR such as resorcinol bis(diphenyl phosphate) (RDP). DMPMP was applied to acrylonitrile–butadiene–styrene (ABS) and ethylene–vinyl acetate (EVA) to investigate the factors governing the flame-retarding behaviors of P–N FRs which would make them efficient for noncharrable polymers. V-0 ratings were achieved at 20 wt % loading of DMPMP for ABS and at a much lesser amount of DMPMP loading (10 wt %) for EVA. Meanwhile, no rating and V-2 were achieved even at 20–30 wt % loading of other P–N FRs or RDP for ABS and EVA, respectively. The results from thermogravimetric analysis, Fourier transform infrared, and UL-94V indicated that DMPMP is a highly efficient FR and acts mainly in a gas-phase flame-retarding mode of action. The condensed phase of DMPMP also contributed to the flame retardancy property through −NH– groups which tendentiously generate a nitrogen–phosphorus-rich residue because of the intermolecular coupling transesterification reaction. These results demonstrated the assumption that DMPMP has a high P content and good hydrostability, which exhibits good flame retardancy for noncharrable polymers such as ABS and EVA.