Thermal degradation of cellulose acetate in presence of bis-phosphoramidates

Novel bis-phosphoramidate compounds phosphoramidic acid, 1,2-ethanediylbis-, tetraethylester (PAEDBTEE) and phosphoramidic acid, 1,4-piperazinediylbis-, tetraethylester (PAPDBTEE) were synthesized as potential flame retardants. Films of cellulose acetate (CA) were prepared by addition of these compounds as flame retardants. The burning tests such as limiting oxygen index and small scale fire test showed improved flame protection of CA in presence of these bis-phosphoramidates. Thermal decomposition studies carried out using pyrolysis combustion flow calorimetry (PCFC) and thermal gravimetric analyzer showed that addition of bis-phosphoramidate increased the peak heat release rates and char content but decreased the total heat of combustion. Further analysis performed using evolved gas analysis techniques such as thermo gravimetric analyzer–Fourier transform infrared spectroscopy (TGA–FTIR) and pyrolysis gas chromatography mass spectrometry (Py-GC–MS) provided insights into the decomposition pathways of cellulose in presence of these additives. The novel compounds were tested for toxicity using Microtox test and were found to be relatively less toxic as compared to phenol and a commercially available flame retardant.