A novel charring agent of poly(p-ethylene terephthalamide) (PETA) was synthesized by using terephthaloyl chloride and ethylenediamine through solution polycondesation at low temperature. The effect of the intumescent flame retardant (IFR) on ABS was studied. The IFR system was comprised of PETA for carbon sources and ammonium polyphosphate (APP) for acid sources. The results showed that PETA could be effective as a charring agent, the weight of residues improved greatly with the addition of IFR. When the content of APP was 25% and PETA was 12.5%, the limiting oxygen index (LOI) value of IFR-ABS system was found to be 33, and class V-0 of UL-94 test was passed. The microstructures observed by SEM indicated that the charring agent (PETA) could promote the formation of uniform and compact intumescent charred layers in IFR-ABS system after burning.
