Expandable graphite's versatility and synergy with carbon black and ammonium polyphosphate in improving antistatic and fire‐retardant properties of wood flour/polypropylene composites

This study investigated the antistatic and fire‐retardant properties of wood flour/polypropylene composites consisting of carbon black (CB), ammonium polyphosphate (APP), and expandable graphite (EG) through resistance meter measurement, cone calorimetry (CONE), thermogravimetric analysis (TGA), and scanning electron microscopy. Antistatic property testing confirmed a positive effect between CB and EG on discharging electrostatic charge. Electrostatic charge was thus considered able to be conducted between CB particles through EG, which acted as a bridge in the CB/EG ‐ treated composites. The results of CONE tests showed that EG significantly reduced the smoke release of the wood plastic composites (WPCs), including total smoke release (TSR), average specific extinction area (SEA), and production of carbon monoxide. During the WPCs burning process, a compound of EG and APP showed synergistic effects which decreased heat release and fixed the residual char. TGA results demonstrated that combining EG with APP, as opposed to using EG only, effectively increased the residual mass and decreases the initial thermal decomposition temperature of the WPCs. Addition of APP caused the wood flour char by catalyzing at a lower temperature, moreover, EG and APP displayed good synergistic effects on fire inhibition and smoke suppression. POLYM. COMPOS., 38:767–773, 2017. © 2015 Society of Plastics Engineers