Abstract: The effects of transition metal oxides on the combustion properties of wood-flour/polyvinyl chloride (WF-PVC) composites were studied by cone calorimeter(CONE)and thermogravimetry analysis(TGA). The effects of transition metal oxides on the fire-retardant and smoke-suppressant properties of WF-PVC composites were discussed. It was found that the addition of transition metal oxides such as CuO、La₂O₃TiO₂ to WF-PVC improved the fire-retardant performance of the composites,while compared to the other two metal oxides,better fire-retardant properties was observed in CuO treated composite which had much lower heat release rate (HRR) and total heat release (THR). All these metal oxides promoted the yield of char residue,and the fire-retardant mechanism of the metal oxides was considered to be the condensed phase mechanism based on the analysis of effective heat of combustion (EHC) and HRR. Smoke production rate (SPR) and total smoke release(TSP) of the composites was decreased as a result of the addition of the transition metal oxides,especially CuO,which was more effective than the others in the flaming phase. TGA results showed that CuO、La₂O₃TiO₂ have different effects on the process of thermal degradation and decomposition of PVC/wood-flour compositions. At high temperature PVC and wood-flour interacted each other in the system of WF-PVC where PVC accelerated the degradation of wood flour while the yield of char resides was improved in the presence of wood-flour. The thermal degradation characteristics of WF-PVC composites more resembled PVC than wood flour.

Key words: cone calorimeter, wood-flour/polyvinyl chloride composites, transition metal oxides, fire-retardant, smoke-suppressant