D-Panthenol (vitamin B5) is widely present in plants and animals, including in e.g. milk and soybean, and naturally contains both nitrogen and reactive OH groups. D-Panthenol was here reacted with phosphoric acid, without using solvents, to produce a phosphorus and nitrogen containing molecule: D-Panthenol-tri (methylphosphonic acid) (ADPTMPA). This was applied to 127 g/m2 cotton fabric in water, with dicyandiamide as a catalyst to accelerate grafting, then cured at 180°C, to reach 20 – 40% FR by weight. Wash durability was tested by 50 laundering cycles (at 50°C, 45 minutes). Limiting oxygen index was increased from 19 (untreated cotton) to 47 (before laundry cycles) and 36 (after washing) and peak heat release rate was reduced by over 90% (before washing). Carbon monoxide release rate was also significantly reduced. Whiteness and gas permeability of the treated cotton were maintained, but the breaking strength was reduced by 31 – 34%, probably as a consequence of the curing temperature, but this is considered not significant for fabric applications. The authors conclude that this bio-based N-P FR acts by releasing non-combustible gases and by char generation and offers good performance and wash durability.
“Renewable vitamin B5 reactive N–P flame retardant endows cotton with excellent fire resistance and durability”, C. Wan et al., Cellulose 2019 https://doi.org/10.1007/s10570-019-02886-z