Enhanced flame retardancy and smoke suppression of polypropylene by incorporating zinc oxide nanowires

Abstract

In this work, zinc oxide (ZnO) nanowires were prepared via hydrothermal method. They were added into polypropylene (PP) with different mass fractions by melt blending method. Thermal stability of ZnO nanowires/PP nanocomposites was investigated through thermogravimetric analysis (TGA). The flame retardant and smoke suppression performances of the nanocomposites were characterized by microscale combustion calorimeter (MCC) and smoke density tester, respectively. The results showed that the prepared ZnO nanowires/PP nanocomposites possessed good thermal stability, flame retardant and smoke suppression performances. With the 30 wt% addition of ZnO nanowires, the onset degradation temperature (T_d5) and maximum weight loss temperature (T_max) of nanocomposite were increased by 34.6 °C and 20.8 °C compared to pure PP. The peak heat release rate (PHRR) and total heat release (THR) of nanocomposite were decreased by 36.0% and 37.8% in comparison to pure PP. Moreover, the maximum smoke density (MSD) of nanocomposites was reduced by 53.9% compared to pure PP. Lastly, the flame retardant and smoke suppression mechanisms of ZnO nanowires were analyzed according to the morphology of the char layer and calculation of activation energy.

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