Experimental study on the burning behaviors of three typical thermoplastic materials liquid pool fire with different mass feeding rates

Nowadays, thermoplastic materials, which represent a risk of the high melt flow fire spread, are widely used in construction industry. The flow of thermoplastic’s melt drips will accelerate the downward flame spread and fall into the pool fires which appears at the foot of the wall fires. Fire will develop to larger and larger soon because of the wall fires and pool fires mutual enhancement mechanism. In this paper, a new experimental setup is used to quantitatively analyze the burning characteristics of pool fires at different steady mass feeding rates. PP (polypropylene), PE (polyethylene) and PS (polystyrene) thermoplastic polymers are selected as test materials and were heated to be the molten phase by electric heater. N2 gas is continuously injected into the chamber to avoid a sudden ignition. The characteristics parameters including dripping rate, flowing rate of hot molten liquids, burning rate and radiant flux of flowing pool fires are analyzed. The experiment results preliminarily suggest that the hot molten liquids induced by PP polymers are easier to drop and flow than that by PE and PS. Therefore, PP materials may be more dangerous for their faster pool fires flowing rate on the floor. Meanwhile, the burning rate of pool fires induced by PS is higher than that by PE and PP, although the dripping rate and flowing rate of PS is the slowest for its large viscosity. For larger mass feeding rates, the dripping rate of three hot molten drips becomes faster. It also indicates that the experimental process of surface tension flow and the flame front of pool fires do not coincide with melt flow front for PP and PE at different mass feeding rates. Specifically, the flame front of pool fires induced by molten PP or PE polymers is slower than the forward movement of the hot molten liquids. The reason for these combustion characteristics of molten thermoplastic polymers that mentioned above may be related to viscosity and structures of thermoplastics, as well as the pyrolysis process of different thermoplastics.