The addition of wood flour improves the mechanical properties of thermoplastics, but also increases theburning rate of neat plastics profoundly. To modify the flammability of wood-plastic composites (WPCs),various additive-typefire retardants such as ammonium polyphosphate (APP), melamine polyphosphate(MPP), and aluminum hydroxide were added to improve thefire performance of WPCs. Both UL94 flametests and cone calorimetry were used to evaluate the fire performance of WPCs, and the results provedthat the addition of 10 wt% APP lead to enhanced self-extinguishing properties. On the other hand,polypropylene with 30 wt% of APP did not achieve self-extinguish properties. The effective parameters inthe cone calorimetry test to give self-extinguishing properties were discussed by comparing the resultsof the burning tests. It was presumed that the most important parameters for self-extinguishing of WPCswas an average heat release rate at initial stage of burning. The effect offire retardants on the mechanicalproperties of WPCs was also investigated. The tensile strength and modulus of the composites decreasedwith the addition offire retardants
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