Study on Leather Modified with Nitrogen-Phosphorus Intumescent Flame Retardant in Fat Liquoring Process

Adding flame retardant into leather is an effective way to improve the flame resistance of leather products. In this paper, a Nitrogen-Phosphorus Intumescent (NPI) flame retardant was synthesized and then added to the fatliquoring process to modify leather. The effect of NPI flame retardant on the flame-retardant properties of leather was investigated using Limiting Oxygen Index (LOI), smoke density, vertical combustion, cone calorimeter tests, and SEM. The results revealed that LOI of leather modified with NPI flame retardant increased with the increase of flame retardant. The flame and flameless combustion time of the modified leather was effectively reduced. Compared with unmodified leather, HRR of the modified leather with 6% NPI flame retardant decreased from 80.32 MJ/m2 to 63.45 MJ/m2; the peak HRR dropped from 108.71 MJ/m2 to 77.23 MJ/m2. Moreover, the fire growth index of the modified leather with 6% NPI flame retardant is close to half of that of the unmodified sample. The results certified the enhancing effect of NPI flame retardant added in the fatliquoring process on flame retardancy of leather samples.