Ammonium sulfamate flame retarded polyamide 6: Morphology and thermal degradation

The effect of ammonium sulfamate (AS) content on the flame retardancy of polyamide 6 (PA6) was studied. It is found that the limiting oxygen index (LOI) of PA6 increases with the increase of AS content and the flame retardancy of PA6 is significantly improved. The morphology of the residues after combustion was examined by means of scanning electron microscopy (SEM). SEM results show that AS facilitates the formation of the intumescent char layer with honeycomb-like structure, which inhibits the transfer of heat and mass, and thus improves the flame retardancy of PA6. The thermal degradation of AS flame retarded PA6 was studied by thermogravimetric analysis (TGA). The Kissinger method was applied to estimate the activation energy (Ea) of the degradation. The activation energy of the thermal degradation of PA6 decreases by adding AS, indicating that AS can promote the degradation of PA6.