Developed compound flame retardant for bitumen based on thermal properties of four components

Abstract

Bitumen produces a lot of harmful gaseous products and heat at high temperature, endangering human health and ecological environments. To develop an efficient compound flame retardant (FR) for suppressing thermal decomposition and volatile release of bitumen, the suppressing effects of matched halogen-free FR for each bituminous component was first discussed, and then a compositional formulation was proposed to develop a new compound FR for bitumen, suppressing bituminous thermal decomposition and volatile release. Results indicated that the matched FR inhibited endothermic and exothermic reactions, lowered the thermal decomposition rate, and retarded the whole thermal decomposition progress of each component. Also, the dynamic release process of emitted volatiles from each component was suppressed by the selected FR. The release amount of main volatiles was decreased, but CO2 and H2O were still main gaseous products from each bituminous component. Additionally, the superimposed and voidless barrier layer was generated owing to the synergic effects of matched FRs. It suppressed the volatilization and thermal decomposition of flammable volatiles, and hindered the heat transfer and oxygen supply, improving the thermal stability of each component. Added hydroxide FRs showed comprehensive effects of cooling, dilution, adsorption and neutralization, and the generated active oxide facilitated the intumescent layer of expandable graphite to be carbonized. The selected FR played flame retarding and smoke suppressing roles on thermal decomposition of each component. Finally, the compositional formulation of compound FR was proposed to develop a new compound FR for bituminous materials based on the suppression of matched FR on each bituminous component. The developed compound FR efficiently suppressed bituminous thermal decomposition, and lowered the release amount of harmful volatiles and heat when exposed to high temperature.