| Abstract: | The combustion performance of polyamide 6 (PA 6) and poly(butylene terephthalate) (PBT), both fire retarded by phosphorus oxynitride (PON), was studied by oxygen index (OI) and Underwriters Laboratory UL94 tests. It was shown that either PON alone or in combination with different co-additives is efficient in PA 6 and much less active in PBT. Thermogravimetric experiments provided evidence that PON promotes charring in both PA 6 and PBT. The mechanism of the char formation from PA 6 and PBT in the presence of PON was discussed on the basis of IR studies of solid residues produced in the thermal decomposition. The effective fire retardant action of PON in PA 6 is related to the interaction with the polymer to produce char, whereas the less effective activity of PON in PBT is related to the unfavorable acceleration of the evolution of combustible aliphatic fragments. |
