THERMAL DEGRADATION AND SMOKE PRODUCTION DURING COMBUSTION FOR INTUMESCENT FLAME RETARDANT RIGID POLYURETHANE FOAMS

The thermal degradation behavior and combustion of rigid polyurethane foams (RPUF) with expandable graphite (EG) and ammonium polyphosphate (APP) were investigated by thermal gravimetric analysis (TG), X-ray photoelectron spectroscopy (XPS), limiting oxygen index (LOI) and smoke density test. On this basis, the effect of EG/APP on the combustion of RPUF/tris (beta-chloroisopropyl) phosphate (TCPP) composites was studied by CONE calorimeter. The results showed that the interaction between EG and APP led to lower weight loss rate of EG/APP at high temperatures and a significant increase of char residue at 800 degrees C. The char formation between EG/APP and RPUF could be mainly contributed by APP. Compared with RPUF, the LOI of RPUF/EG/APP increased from 19.8% to 35.4% and the smoke density changed little. Compared with the RPUF/EG, RPUF/APP and RPUF/EG/APP, the more the amount and the higher thermal oxidation resistance of char residue,the higher the LOI is; the more compact of the residue surface, the lower the smoke released is. It was found that the heat release, smoke production rate and CO release rate of RPUF/TCPP were decreased significantly by the addition of EG/APP. The results embodied the advantages of a combination of chemical and physical intumescent flame retardants in the EG/APP system.