Abstract: A novel intumescent flame retardant (IFR), containing ammonium polyphosphate (APP) and poly(hexamethylene terephthalamide) (PA6T), was prepared for acrylonitrile-butadiene-styrene copolymer (ABS). It was found that when the contents of APP and PA6T were 25 % and 5 %, respectively, the limiting oxygen index of ABS/IFR system reached 29 %, but only UL-94 V-1 rating was passed. Thus, Al(H2PO2)3 was incorporated into ABS/APP/PA6T system as a synergistic agent. It was found that 2 % addition of Al(H2PO2)3 caused PA6T/APP/PA6T(70/23.3/4.7) to pass V-0 rating of UL-94 test. Meanwhile, the TG curves indicated that PA6T was effective as a charring agent and there was a synergistic reaction between PA6T and APP, which promoted the char formation of ABS/IFR system. The residual char after the limiting oxygen index test was characterized using Fourier transform infrared spectra. It showed that P-O-C bond was formed in the residual char, indicating the cross-linking reaction occurred. Furthermore, scanning electron microscopy revealed that both ABS/APP/PA6T(70/25/5) and PA6T/APP/PA6T/Al(H2PO2)3(70/23.3/4.7/2) formed uniform and compact intumescent charred layers.

Key words: acrylonitrile-butadiene-styrene copolymer, intumescent flame retardant, ammonium polyphosphate, poly(hexamethylene terephthalamide), combustion property