A phosphorus and nitrogen polymer, poly(piperazinyl phosphamide) (PPMA) was synthesised by a one-step reaction by progressively combining acetonitrile, piperazine, trimethylamine and phosphorus oxychloride. The resulting polymer was tested as a flame retardant in EVA (ethylene vinyl acetate) with APP (ammonium polyphosphate).
PPMA alone generated over 45% char residue in air at 600°C. EVA with 25% APP and 5.5% PPMA achieved UL94-V0 (3.2mm). The PPMA polymer showed very efficient char production and flame retardancy was improved by synergy with APP, in that APP delayed the breaking of the carbon – nitrogen bond in the PPMA polymer. In a previous paper, a similar N-P polymer, piperazine-modified ammonium polyphosphate PA-APP was shown to be an effective PIN flame retardant in polypropylene, achieving UL94-V0 (3.2 mm).
“Poly(piperazinyl phosphamide): a novel highly efficient charring agent for an EVA/APP intumescent flame retardant system”, L-P. Dong et al., RSC Advances 2016, 6, 30436–30444 https://dx.doi.org/10.1039/c6ra00164e
“An Efficient Mono-Component Polymeric Intumescent Flame Retardant for Polypropylene: Preparation and Application”, Z-B. Shao et al., ACS Applied Materials & Interfaces, 2014, 6, 7363−7370 https://dx.doi.org/10.1021/am500789q