Phytic acid (a natural organophosphate) with ammonia gave a washable phosphorus nitrogen fire safety treatment for wool. Phytic acid (PA) is a phosphorus-rich organic molecule found widely in plant seeds, where it is a natural phosphorus nutrient store. PA was reacted with ammonia solution (which can be also bio-based by stripping of e.g. digestate or manure), then covalently reacted onto wool fibres at 90°C using dicyandiamide as catalyst (reaction of the phosphate group of PA with OH groups on wool fibres), followed by drying at up to 160°C, then washing). The treatment increased LOI from 24 to 32, and the treated wool fabric (125 g/m2) achieved B1 in the vertical burn test GB/T 5455 (char length reduced from 30 to 10 cm) and was self-extinguishing, including after 15 wash cycles. Maximum smoke density was reduced by 14%. Tensile strength of the fibres was increased. The ammonia phytic acid is considered to improve fire safety by generating highly graphitised aromatic char.
“Covalent flame-retardant functionalization of wool fabric using ammonium phytate with improved washing durability”, X-W. Cheng et al., Industrial Crops & Products 187 (2022) 115332 https://doi.org/10.1016/j.indcrop.2022.115332