Experimental studies on thermal analysis and explosion characteristics of superfine polystyrene powders

Recently, various superfine powders have been used in a wide range of applications in industrial production, but the research on the flammability and explosion characteristics of the organic powder is still under development. In this study, the thermal behaviors of superfine polystyrene (PS) powders were studied by using thermogravimetric analysis (TG). The results showed that the thermal degradation of micro-PS occurred in a two-step process, and the TG and DTG curves shifted to the higher-temperature zone when the particle size increased. Dust explosion test device series (MIE-D 1.2- and 20-L spherical explosion test device) were adopted to analyze the influence of sample concentration, particle size and ignition delay on various flammability characteristics of superfine PS powders, including minimum ignition energy (MIE), maximum explosion pressure (P_max), maximum rate of pressure rise ((dP/dt)_max) and lower explosive limit (LEL). The results revealed that the MIEs of different samples with different sizes (3, 5, 10, 15 and 20 μm) were 7.54, 9.73, 13.11, 15.42 and 19.29 mJ, respectively, while the corresponding LELs were 10, 10, 15, 25 and 25 g m⁻³, respectively. These two parameters (MIE and LEL) that characterize the possibility of dust explosion decrease with decreasing the particle size. The powders with sizes of 3, 5, 10 and 20 μm have P_max values of 0.6406, 0.6277, 0.6066 and 0.5805 MPa, respectively, while the (dP/dt)_max values are 89.318, 85.634, 82.073 and 80.577 MPa s⁻¹, respectively. These two parameters (P_max and (dP/dt)_max) that characterize the severity of dust explosion increase with decreasing the particle size. This study shows the smaller the particle size, the higher the explosion possibility and higher the severity of superfine PS powders.