Effects of dolomite and intumescent flame retardant additions on thermal and combustion behaviors of rigid polyurethane foams

Weak thermal stability and low-burning resistance of the rigid polyurethane foams are the classic problems in the usage of them. Therefore, it is required to improve these problems of the foams while reducing the cost of production. This study investigated the effects of dolomite (DOL) and intumescent flame retardant (IFR) system on thermal and combustion behaviors of rigid polyurethane foams (RPUFs). For this purpose, DOL (5, 10, and 15 wt%) and DOL/IFR (5/5, 10/5, and 5/10 wt%) combinations were added into RPUFs. Thermogravimetric analyses were performed to investigate the thermal decompositions of the foams and the thermal conductivity measurements were performed to examine the effects of DOL and DOL/IFR additions on the thermal insulation properties of the foams. Cone calorimeter and UL 94 tests were performed to investigate the fire resistances of the foams. The test results showed that up to 15 wt% DOL could be incorporated into the rigid polyurethane foams as filler without any problems in the foam productions, and the thermal and the combustion behaviors of the foams were slightly enhanced. In addition, it was determined that IFR should be used to improve the thermal stability and the fire resistance of the DOL added foams. Among DOL/IFR combinations, 5 wt% DOL and 10 wt% IFR addition satisfied the best performance in terms of the thermal stability and the fire resistance with reducing the smoke, CO, CO2 and NO emissions. In general, the additions of DOL and IFR slightly increased the thermal conductivity coefficients of the foams.