Comparison of the thermal decomposition behavior of a non-fire retarded and a fire retarded flexible polyurethane foam with phosphorus and brominated additives

Thermogravimetric analysis was carried out to investigate the thermal decomposition behavior of a commercial fire retarded (FR) and a non-fire retarded (NFR) flexible polyurethane foam. The effects of the heating rate and the reaction atmosphere on the thermal decomposition process were studied at three different heating rates ranging from 5°C/min to 20°C/min in both nitrogen and air environment. Results from the time-of-flight secondary ion mass spectrometry (ToF SIMS) study revealed that the additives in the FR foam were phosphorus and brominated compounds. The measurements by means of colorimetric method further certified that the concentrations of phosphorus and bromine in the FR foam sample were 0.08 wt% and 1.4 wt% respectively. From the thermogravimetric (TG) and the derivative thermogravimetric (DTG) curves, it was seen that the thermal decomposition processes of both the FR and the NFR foams followed a two-step reaction in nitrogen. However, the thermal decomposition processes followed a three-step reaction in air. The thermal analysis results showed that the flame retardant additives of phosphorus and brominated compounds acted not only in the gas phase but also in the solid phase. Furthermore, the flame retardant additives decreased the thermal stability and increased the char formation in the temperature ranging from 300°C to 400°C, which commonly, is the temperature range for smoldering combustion in this kind of foam material. From the kinetic parameters estimated from the TG and the DTG curves, it was seen that the activation energies of the flexible polyurethane foams were very sensitive to the temperature and were also influenced significantly by the flame retardant additives.