Flammability and flame‐retardant mechanism of high density polyethylene/wood fiber/modified ammonium polyphosphate composite

Fabrication and characterization of a novel high density polyethylene/wood fiber/modified ammonium polyphosphate (HDPE/WF/MAPP) composite have been carried out. The flammability of the composite is characterized by the limiting oxygen index (LOI), vertical burning test (UL‐94), and cone calorimetry. The flame‐retardant mechanism is investigated by Fourier transform‐infrared (FT‐IR), X‐ray photoelectron spectroscopy (XPS), and scanning electronic micrograph (SEM).The results indicate that, with the optimum formulation, the LOI and UL‐94 of the HDPE/WF/MAPP composite are 38.0% and V‐0 rating, respectively. Comparing with HDPE/WF, the peak of heat release rate (PHRR) of the HDPE/WF/MAPP composite decreases from 432 to 166 kW m ⁻² , and total heat release (THR) decreases from 66 to 33 MJ m ⁻² . Cone calorimeter analysis suggest that the smoke production rate (SPR), total smoke production (TSP), mass loss rate (MLR), and time to ignition (TTI) of the HDPE/WF/MAPP system significantly decrease. In addition, the thermal stabilities of the composite are studied by thermo gravimetric analysis (TGA), which shows there are two stages decomposition during the thermal degradation process. With the addition of MAPP, char residue of the composite increase from 12.06% to 34.67%. The char residue containing P‐OH, P‐N‐C, P‐O‐P, P‐O‐C, and aryl groups can directly affect the flame retardance. The flexural modulus of the HDPE/WF/MAPP system is improved greatly in the presence of MAPP. POLYM. COMPOS., 39:1192–1199, 2018. © 2016 Society of Plastics Engineers