Poly- and cyclo- phosphazenes are recognised effective PIN flame retardants, but to date are not available as water soluble and permanent systems for textiles. Here a new cyclophosphazene was synthesised in a one-step process: hexa (allylamine) cyclotriphosphazene (CPZ). This was stable under acidic conditions and so could be applied to textiles in aquatic solutions. Soaking was followed by photo-induced grafting (UV cross-linking). CPZ was tested for PET, PA (polyamine 6.6), cotton and blends. A 10% loading of CPZ showed durability in washing, increased LOI (limiting oxygen index) and enabled to pass DIN 75,200 (automobile) and DIN 15,025 (PSA protective clothing) with cotton and with PA- and PET-cotton blends (not with PET or PA only). The treated textiles did not pass DIN 4102-1-B2 (construction). All fire tests were carried out after at least one wash cycle. The CPZ showed to effectively generate char (except with PET only) with formation of glassy phosphoroxinitrids. Further work is underway to compare the flame retardancy mechanism of different poly- and cyclo- phosphazenes.
“A Green Water-Soluble Cyclophosphazene as a Flame Retardant Finish for Textiles”, T. Mayer-Gall et al., Molecules 2019, 24, 3100; https://doi.org/10.3390/molecules24173100