Casein phosphopeptide-metal salts combination: A novel route for imparting the durable flame retardancy to silk

The environmentally sound flame retardant (FR) treatment of textiles is the hot spot research in the processing of textiles. In this work, the combined treatment of casein phosphopeptide (CPP) and ferrous and titanium sulfates was applied to prepare the wash-resistant FR silk fabric. The complexation of CPP and metal ions was confirmed by Fourier transform infrared spectral analysis. The FR capability of the CPP and metal ions treated fabrics was demonstrated by two combustion methods. The fabrics obtained by treatment of 10 g/L CPP followed by mordanting of 4 g/L ferrous and titanium sulfates had a limiting oxygen index of 27.8% and 28.0%, respectively, and after vertical burning their residual char length was less than 15 cm even after 20 repeated washings. The increased thermal stability at high temperatures and good charring ability of the treated fabrics contributed to their FR capability. Interestingly, the CPP and ferrous sulfate treated fabric displayed a brilliant yellow color with good washing and rubbing fastness.