Non-halogenated flame-retardant additive from Amazon mineral waste

Abstract

Halogenated flame-retardant additives typically release toxic gases during combustion, which has led to the search for substitutes. In an attempt to avoid this harmful effect on human health, the aim of this study was to investigate using a hydroxide-rich mineral waste to formulate a polymer matrix composite. The waste is rich in gibbsite “Al(OH)3”, goethite “FeO(OH)” and kaolinite “Al2Si2O5(OH)4”, which, once heated, release water at ∼ 270, ∼ 350 and ∼ 500 °C, respectively. This waste is derived from processing metallurgical bauxite and is discarded in large amounts in northern Brazil. The retardancy effects of this bauxite waste were investigated for production of unsaturated polyester resin (UPR) matrix composites with varying contents 10–30% of waste. The mechanical properties were also evaluated and it was noticed that the increasing the amount of filler decrease tensile strength of composites. The flammability tests revealed that the waste significantly retarded flame propagation in the polyester and the rate burning in these composites were as effective as the rate burning of the composites containing the reference material (RM). Lastly, the gibbsite-kaolinite-goethite inorganic material, which is now considered only as waste, has the potential to become a sustainable coproduct of the bauxite industry and economical raw material (flame-retardant filler) for the production of polymer-matrix composites.

Keywords

• Mineral waste
• Retardancy
• Composite