Thermal characterization of ammonium starch phosphate carbamates for potential applications as bio-based flame-retardants.

The thermal degradation of ammonium starch phosphate carbamates (SPC) with varying degrees of substitution (DS) was analyzed using differential scanning calorimetry and thermogravimetry coupled with Fourier-transformed infrared spectroscopy. The data were analyzed with regard to the structural features of SPC and with respect to its potential flame-retardant properties. It became obvious that charring of SPC and polyphosphate formation in the condensed phase increased significantly in case of rising DS of SPC. Correspondingly, temperature mass losses and amounts of evolved decomposition products decreased noticeably in comparison with native starch. Activation temperatures of SPC markedly decreased with increasing DS and were considerably lower than decomposition temperatures of native starch. As a byproduct of SPC degradation ammonia was identified which contributes as inert gas to flame extinguishment. The results suggest that SPC represent promising candidates for a new generation of sustainable and environmentally friendly flame-retardants based on renewable resources.