Effects of melamine polyphosphate on explosion characteristics and thermal pyrolysis behavior of polyamide 66 dust

Polyamide 66 (PA66) is widely used in the polymer market and there is a risk of dust explosion during processing and manufacturing. In this study, the explosion hazard of PA66 dust and the inerting effect of melamine polyphosphate (MPP) in PA66 dust were evaluated by testing the explosion characteristic parameters. The results showed that the maximum explosion pressure ( P max ), minimum ignition energy (MIE), and minimum ignition temperature (MIT) of PA66 dust were 5.6 bar, 48 mJ and 430 °C, respectively. No explosion occurred after the addition MPP reached 50 wt%. Moreover, the thermal pyrolysis behavior of the mixed dust was revealed by thermogravimetric analysis (TGA) and TG coupled with FTIR (TG-FTIR) analysis. The results showed that C 3 H 6 , produced during the pyrolysis of PA66, was the main combustible gas. However, the addition of MPP promoted the CO 2 production of PA66 and consumed a large amount of free radicals. It was also found that the polyphosphate from MPP decomposition chemically reacted with PA66, which reduced the decomposition temperature of PA66 and produced an extended carbon layer. These results are an important reference value for the prevention and control of dust explosions in polyamide. • The dust explosion hazard of polyamide 66 (PA66) was assessed. • Melamine polyphosphate could suppress the dust explosion of polyamide 66. • The combustible gas produced by the pyrolysis of PA66 dust was analyzed by TG-FTIR. • MPP promoted the thermal decomposition of PA66 and the formation of char. • The chemical reaction of MPP and PA66 promoted the production of CO 2 .