Evaluation of Different Flame Retardant Combinations for Core/Shell Structured Wood-Plastic Composites by Using a Cone Calorimeter

Abstract

The fire retardancy of coextruded wood-plastic composites (WPCs) containing melamine, ammonium polyphosphate (APP), natural graphite, expandable graphite and carbon nanotubes (CNTs) in the shell layer was characterized with a cone calorimeter test. A coextruded composite manufactured without any fire retardant (FR) in the shell layer was used as a reference. The incorporation of different combinations of FRs in the shell layers of WPCs reduced the peak heat release rate by 3-43%, depending on the FR combination. Other studied parameters, such as ignition time, total heat release and mass loss rate were improved after FR systems loading. The best improvement of flammability characteristics was observed with melamine/natural graphite combinations, whereas the melamine/expandable graphite system resulted only in slight improvement of the studied parameters. However, it should be noted that the amount of expandable graphite loading was 2-4 times lower than the amount of natural graphite loadings. Incorporation of 2 wt.% CNTs in the shell layer did not show any significant improvement in the studied parameters. The total smoke release and carbon monoxide production were increased with melamine/APP loading in the shell layer.