A phosphorus-nitrogen flame retardant for cotton was synthesised and tested, showing good washability without formaldehyde release, maintaining self-extinguishing (125 g/m2 fabric) after 50 laundering cycles. Ammonium salt of tris˗(hydroxymethyl)˗ aminomethane˗penta(methylphosphonic acid) (ATPMPA) was synthesised in three steps, from the biological buffering agent tris˗(hydroxymethyl)˗aminomethane (THAM), urea, formaldehyde, phosphorus acid and phosphoric acid, then purified. Dicyandiamide was used as a catalyst to graft ATPMPA from aqueous solution onto the cotton at 14 – 26% by weight (3 hours at 70°C followed by 180°C for 6 minutes). The higher loading of ATPMPA increased LOI of cotton fabric from 18 to 44, and still 32 after 50 laundering cycles. The higher loading of ATPMPA reduced the breaking strength of the cotton by around 24%, possibly partly due to the baking at 180°C, but did not significantly deteriorate whiteness (12% decrease) and increased elasticity of the fabric.
“Synthesis of a phosphorus˗nitrogen flame retardant endowing cotton with high whiteness and washability”, C. Wan, Industrial Crops & Products 141 (2019) 111738 https://doi.org/10.1016/j.indcrop.2019.111738