Flame retardancy of bitumen: A calorimetry study

Abstract

The article investigates the flame retardancy of bitumen for roofing applications using the mass loss calorimeter. Screening of the solid flame retardants, including expandable graphite, boron-based compounds, and silsesquioxanes, shows that they can provide high fire performance. Nevertheless, the settling of these compounds during hot storage stability tests does not permit using them for large-scale application (transportation of bitumen at high temperature). On the contrary, the incorporation of the commercial liquid flame retardant OP 920 (phosphoric acid alkyl ester) in bitumen enhances the reaction to fire of the bitumen, and the mixture is stable during hot storage test. Nanoparticles (organoclay and multiwall carbon nanotubes) have not been found to be appropriate flame retardants for bitumen, but they can be used as synergist with OP 920. Nevertheless, they are not suitable for practical applications because organoclay settles during hot storage tests. Only OP 920 among the evaluated flame retardants can be considered for roofing applications. It provides a very promising fire performance in polymer-modified bitumen and in roofing felts.