Abstract: The expandable graphite (EG) and oxidized expandable graphite (OEG) were compounded with ammonium polyphosphate (APP)/magnesium hydroxide ［Mg(OH)2］ and APP/aluminum hydroxide ［Al(OH)3］ to prepare flameretardant polyurethane (PU) coating, respectively. The flameretardant properties of the composite coating were evaluated in terms of limiting oxygen index (LOI) and cone calorimeter tests. The results indicated that the presence of OEG led to a higher LOI compared with EG at the same particle size, whereas the peak heat release rate decreased dramatically. The morphology of residual char was investigated by scanning electron microscope, and the results revealed that the residual char was more integrated and compact for the composite coating containing OEG, and its expansion height was also improved.

Key words: expandable graphite, oxidation treatment, hydroxide, polyurethane coating, flame retardant property