Guanidine, a biological molecule, was reacted with ammonium and phosphorus to produce a durable, reactive FR for cotton. Guanidine is found in urine, and can be produced by the degradation of guanine (from DNA/RNA) or synthetically. Guanidine acetic acid was reacted with phosphorus acid, formaldehyde and then urea to produce a molecule with high P and N content (AGATMPA), which could be reacted with cotton fabric using dicyanamide as a catalyst by soaking in solution and curing at 180°C for 5 minutes, before rinsing and drying. This treatment showed to be effective in improving fire resistance: LOI of virgin cotton 19%, LOI with 15% wt. AGATMPA 40%, no after-flame nor after-glow. After 30 wash cycles, the LOI (15% wt. AGATMPA) was reduced to 29% and the FR treatment is considered durable. The FR action is considered to be due to generation of a carbonised char layer, release of ammonia which dilutes fire gases and cooling by release of water from carbonisation.
“A novel guanidine ammonium phosphate for preparation of a reactive durable flame retardant for cotton fabric”, C. Wan et al. Cellulose volume 27, pages3469–3483 (2020) https://doi.org/10.1007/s10570-020-03003-1