Durability and performance of wood flour/polyethylene composites containing fire retardants after weathering via ASTM D2565

Wood–plastic composites are composite materials consisting of wood particles, thermoplastic polymer, and small amounts of other performance additives to increase performance in exterior construction applications such as decking and siding. Three best-performing fire retardants, determined from a previous study, which were brominated, magnesium hydroxide, and ammonium polyphosphate, were selected for this weathering study and more detailed analysis with color analysis, thermogravimetric analysis/differential scanning calorimetry, and the cone calorimeter. With the rapid surface heating condition at cone calorimeter irradiance of 50 kW m−2, modest surface leaching of fire retardant was detected as caused by weathering via increased first peak heat-release rate and reduced time to ignition values. Otherwise, the weathering had minimal effect on the remaining heat-release rate profile, and results confirmed ammonium polyphosphate as top performing fire retardant, even better than Ipe wood, with magnesium hydroxide and brominated slightly worse than Ipe. This suggests that 35% high-density polyethylene content reduced fire retardant bulk leaching.