Thermal degradation study of fire resistive coating containing melamine polyphosphate and dipentaerythritol

A melamine polyphosphate (MPP)/dipentaerythritol (DPER) mixture was used as fire retardant additives for preparing waterborne intumescent fire resistive coating. The thermal degradation of the MPP/DPER mixture and of the coating was studied by TGA and FTIR. The resulting char of the coating was investigated by XPS, SEM and energy dispersive spectroscopy (EDS). The results showed that the thermal degradation behavior of the MPP/DPER mixture was similar to that of the coating. They decomposed to nonflammable gases, and formed intumescent char layer containing phosphorus oxide at high temperature. The EDS results proved that the resulting char was gradually oxidized with the temperature increase. The SEM micrographs showed that the average cell size of the char layers became bigger and the cell size distribution became wider as the temperature increased from 500 °C to 800 °C, and this non-uniform char layer could damage the fire protection of the coating.

► MPP/DPER mixture was used as fire retardant additives for preparing intumescent fire resistive coating.
► During the thermal decomposition at high temperature, the coating could release nonflammable gases, and formed intumescent char layer containing phosphorus oxide.
► The average cell size of the char layers became bigger and the cell size distribution became wider as the temperature increased from 500 °C to 800 °C, and this non-uniform char layer could damage the fire protection of the coating.
► With the temperature increase, the carbon content and nitrogen content of the char layers decreased, and the oxygen content increased, which indicated that the char layers were gradually oxidized at high temperature.