Phosphoramidate-Containing Flame-Retardant Flexible Polyurethane Foams

In this study, we have investigated the structure–flame-retardant (FR) efficacy relationships of phosphoramidates (PRs) on flexible polyurethane foam (FPUF). FPUFs that contain model monosubstituted secondary PRs, monosubstituted tertiary PRs, and trisubstituted secondary PRs were prepared and evaluated for FR efficacy and thermal decomposition characteristics. The fire test results indicate that methyl ester PRs exhibit better FR behavior, compared to analogous phenyl ester derivatives at equal weight percentage in polyurethane (PU) foams. Within the same class of PRs, the monoallyl derivatives exhibited the highest level of flame retardancy. The multiallyl PR derivatives did not offer any advantage, in terms of improved flame retardancy. Evolved gas analysis from the thermal degradation of PU foams indicates that the PRs are volatilized in the first stage of thermal decomposition and are primarily active in the gas phase with the exception of the triallyl-PR derivative, which is primarily active in the condensed phase.