Flame retardancy of wood-plastic composites by radiation-curing phosphorus-containing resins

Wood-plastic composites were prepared by impregnating softwood and tropical hardwood by a radiation-curing resin containing phosphorus or chlorine groups as flame retardant. Microscopic observations revealed that the heterogeneous impregnation depends on the density but also on the wood species and sample orientation. Physical properties (hardness, stiffness, conductivity, water content) of the unmodified woods and their resin-impregnated counterparts were examined and correlated with their densities. The flame retardancy was investigated by cone calorimeter tests. Although the incorporation of the resin is detrimental to the flame retardancy, the addition of phosphorus or chlorine groups allows a decrease in flammability. Phosphorus-containing resins limit the smoke release in comparison to chlorine-containing resin. Finally, the denser wood-plastic composites exhibit improved mechanical properties without increasing the flammability in comparison with their unmodified wood counterparts.