SYNERGISTIC EFFECTS OF NOVOLAC-BASED CHAR FORMER WITH A PHOSPHORUS/NITROGEN-CONTAINING FLAME RETARDANT IN POLYAMIDE 6

The synergistic effect of phosphorus oxynitride (PON) with a novolac-based char former modified by salification (NA-metal salt) on the flame retardance of polyamide 6 (PA6) was investigated. For this purpose, various flame-retardant PA6 systems were melt-compounded with PON, PON/NA, PON/NA-V2O5 and PON/NA-Fe2O3, and their flame retardance was evaluated by measuring the limiting oxygen index (LOI) values and UL-94 vertical burning ratings. The results showed that, compared with the PA6/PON/NA system, the combination of two char formers (NA-V2O5, NA-Fe2O3) with PON could obviously improve the char formation and flame retardance of PA6. The flame retardance and cone calorimetric analyses showed the stronger synergism as well as the better flame retardant performance of PON/NA-Fe2O3 flame retardant system. The effects of different char formers on the flame retardance and thermal stability of this system were also discussed.