Effects of different types of flame-retardant treatment on the flame performance of polyurethane/wood-flour composites

To improve the flammability of foamed polyurethane/wood-flour composites (FWPC), ammonium polyphosphate (APP) was used as a flame retardant to modified FWPC. The effects of different flame treatment processes on flame performance, smoke suppression, thermal property, and surface micrographs of flame retardant FWPC were investigated. The results showed that FWPC with the addition or impregnation process both improved the combustion behaviors. Compared with the addition process, FWPC-impregnation (FWPC-I) had a lower total heat release (THR), lower peak heat release rate (PHRR), prolonged time to ignition (TTI), more residues, and better combustion safety. FWPC-I had the highest residual carbon rate reaching 39.98%. A flame-retardant layer containing the P-O group was formed in the residual carbon of FWPC-I. Although APP had negative effects on the physical properties of FWPC, it was an effective flame-retardant ability for foamed polyurethane/wood-flour composites.