Metal-free Dyeing of Cotton Fabric Using Mangrove Bark Polyphenols via Azoic Dyeing

This study proposed a novel azoic dyeing method, in which mangrove bark extract was used as the colorant. This approach eliminates the use of toxic metallic mordants. Polyphenols from mangrove bark were selected as the natural coupling component. These were applied to cotton fabric using an exhaust method, then reacted with diazonium salt prepared from a powerful primary aromatic amine (p-nitroaniline). Four concentrations of p-nitroaniline were tested from 0.5-7 % owf, produced a range of shades from pale to dark. The study confirmed that fabric was effectively and efficiently dyed with a high degree of color yield. Azoic dyeing produced a uniform bright yellow shade, with homogeneous penetration of the dye molecules. An extended range of plant materials were then investigated, and a significant correlation was found between the total phenolic content of the plant materials and the K/S of the dyed cotton. This confirmed that the proposed method can be used to fix natural dye to a cotton substrate, as long as the plant extract contained polyphenol. The colorimetric properties (L* a* b*, and K/S) of the dyed fabric were compared with those produced by traditional mordants (AlK(SO4)2 and FeSO4). The formation of azo linkages on the fabric was confirmed by ATR FTIR. Color fastness to washing and dry crock fastness were found to be acceptable, though the wet crock fastness and light fastness were low, due to the formation of surface dye on the fibers.