Waste-derived carbonaceous filler from calcium carbide furnace dust for modifying the fire behavior of polypropylene composites

With the increasing interest in industrial waste recycling, this study prepared a waste-derived carbonaceous filler (HCCFD) from calcium carbide furnace dust and incorporated it into polypropylene (PP) to modify its fire behavior. The PP composite containing 10 wt% HCCFD exhibited an increased LOI value of 23.5% and achieved a UL-94 V-2 rating. Cone calorimetry indicated that, compared with neat PP, the peak heat release rate and peak smoke production rate decreased by 6.9% and 6.5%, respectively. Mechanism analysis suggested that HCCFD promoted char formation mainly in the early combustion stage, contributing to the generation of a carbonaceous layer with a certain degree of graphitic structure. This layer may provide a temporary barrier effect against heat and oxygen transfer, thereby delaying combustion and reducing the peak heat and smoke release. However, the observed increases in total heat release and total smoke production indicate that HCCFD does not reduce the overall fire load or total smoke hazard, and its flame-retardant effect is therefore limited primarily to the early combustion stage rather than the entire burning process. Overall, this work provides a potential approach for the resource utilization of calcium carbide furnace dust in flame-retardant polymer systems.