“Phosphorus tailings” – waste generated in large quantities by phosphate rock mining (in this study, from Tiaoshuihe phosphate mine, Hubei Sanning Mining, China) were tested as a flame retardant, at 2.5 – 10% loading, with 15 – 25% aluminium hypophosphite, in TPU (thermoplastic polyurethane). The tailings contain calcium-, phosphorus-, silicon-, magnesium-, iron- and aluminium- minerals. The phosphorus tailings were first surface modified with ammonium and silane coupling agent to improve polymer compatibility. Peak heat release and peak smoke release were significantly reduced, further than achieved by aluminium hypophosphite alone, down to 9% and 34% of values for neat TPU. The authors conclude that surface-modified phosphorus tailings and aluminium hypophosphite act synergistically to improve fire performance of TPU, and that this could represent a valorisation route for this waste material. Pinfa notes however that possible implications of contaminants in the phosphorus tailings should be assessed (e.g. heavy metals).
“Synergistic effect between phosphorus tailings and aluminium hypophosphite in flame‐retardant thermoplastic polyurethane composites”, Q. Zhou et al., Polym Adv Technol. 2019;1–8. https://doi.org/10.1002/pat.4695