Flame-retardant rigid polyurethane foams prepared with amorphous sodium polyborate

Abstract

Highly flame-retardant rigid polyurethane (RPU) foams were prepared by vacuum impregnation or pressure impregnation of sodium polyborate (SPB) solution. The RPU foams (10 mm thickness, 134-690% SPB) endured the flame of a butane gas burner for 167-1144 s, and the backside temperatures remained below 45°C until penetration occurred. The heat releases from the RPU foams with 150 and 400% SPB in air in the cone calorimeter tests were 8.8 and 4.1 MJ/m 2, respectively. The analyses with thermogravimetry, differential scanning calorimetry, and scanning electron microscopy indicated the flame-retardant mechanism, in which the SPB foam and the formed char layer together insulated the inside from oxygen gas and heat. © 2011 Wiley Periodicals, Inc.