The Synthesis and Application of Phosphorus-Nitrogen Flame Retardant Retanning Agent

In order to improve the fire resistance of leather to meet the higher fire-safety requirement, a phosphorus-nitrogen flame retardant retanning agent (M-THPS-U for short) was synthesized and used to treat leather. The vertical flame test, oxygen index test, smoke density, mechanical properties, thickness increase, and shrinkage temperature were used to evaluate the properties of M-THPS-U, and the dosage of M-THPS-U was optimized at the same time. Furthermore, the hide powder treated with M-THPS-U was used to study the flame resistance effect by thermogravimetry (TG) and microscopy. The results showed that the fire resistance of leather was improved obviously by using 5% of M-THPS-U. With the increase of M-THPS-U dosage, the mechanical properties dropped, but the fire resistance, thickness increase and shrinkage temperature of the leather raised. The TG results indicated that the fire retardant could promote the fire resistance of leather by accelerating leather fiber converting into char and decreasing the temperature at break down. In short, not only does M-THPS-U improve the fire resistance of leather, but it also has retanning and filling effects.