Improving the flame retardancy of the polypropylene/aramid fiber composites by the introduction of decabromodiphenyl ethane and antimony trioxide

Our previous study showed that aramid fibers (AFs) could significantly enhance the mechanical properties of polypropylene (PP) composites; for example, the tensile strength of PP/AF composites with 30 wt % AF increased by 65.6%, whereas the Izod notched impact strength was almost five times that of pure PP. However, the fire performance of the PP/AF composites was not ideal. In this study, decabromodiphenyl ethane and antimony trioxide [Sb2O3; decabromodiphenyl ethane–antimony trioxide (D–S)] were introduced to improve the flame retardancy of PP/D–S/AF composites. Fourier transform infrared spectroscopy and scanning electron microscopy techniques were used to investigate the possible chemical reaction between the phosphate coupling agent and AFs. The mechanical properties of the PP composites were evaluated by tensile, flexural, and impact tests. The flame retardancy was characterized by limiting oxygen index and UL‐94 burning tests. The thermal properties of the PP composites was also investigated by combined thermogravimetry–differential thermal analysis. The results show that good interfacial adhesion between the fibers and the PP matrix was formed in the presence of the phosphate coupling agent. The flame retardancy and mechanical properties of the PP/D–S/AF composites were significantly improved by the incorporation of AFs and D–S. The sample containing 30 wt % D–S and 20 wt % AF reached V‐0 in the UL‐94 test. The maximal char residue of PP/D–S/AF was up to 15.5%, which was 115% higher than that of PP/D–S. A possible synergism of the flame retardancy between the AFs and D–S is proposed and discussed. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013