Phytic acid (see above) was tested as a bio-based PIN flame retardant with titanium oxide nanoparticles as a synergist and BTCA (a polycarboxylic acid) for crosslinking, on silk crepe fabric (52 g/m2).
Application was by 2 x 10 minute immersion / padding, curing at 160°C, rinsing and drying. Peak heat release rate of the silk fabric was reduced by >50% and LOI (see above) increased from 25% to 37%. Issues noted are that the flame retardancy tends to be progressively lost with washing (not durable beyond 25-30 laundry cycles), yellowing of the silk and a small loss of softness.
“Improvement of flame retardancy of silk fabric by bio-based phytic acid, nano-TiO2, and polycarboxylic acid”, X-W. Cheng et al., Progress in Organic Coatings 112 (2017) 18–26 http://dx.doi.org/10.1016/j.porgcoat.2017.06.025