| Abstract: | The thermal decomposition of structurally related N–H and N,N′-disubstituted polyureas (Table I) and their mixtures with ammonium polyphosphate (APP) was investigated by thermogravimetry (TG) and direct pyrolysis in a mass spectrometer (MS). The N–H polyureas (IV–VI) undergo a quantitative depolymerization process with the formation of oligomers with amine and isocyanate end groups. In contrast, the thermal degradation of the N,N′-disubstituted polyureas (I–III) proceeds by a different mechanism as a function of their chemical structure. The addition of APP lowers the thermal stability of the N,N′-disubstituted polyureas, whereas that of the N–H polyureas is unaltered. However, our data show that APP does not change the nature of the pyrolytic products. The destabilizing effect of the additive can be attributed to the catalytic action of the acid species formed by its thermal decomposition. |
