Effect of Novel Intumescent Retardant on Flame Retardancy of ABS

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.