Eco-friendly Leather Dyeing using Ultrasound Technique

In this study, leather was dyed using ultrasound and conventional methods to investigate the influence of ultrasound on leather dyeing. Ultrasound is more effective than mechanical agitation in enhancing leather dyeing. Effects of various process parameters, such as, dyeing temperature, dyeing time and doses of dye on dyeing of leather in presence of ultrasound were investigated. Dyed leathers were characterized with scanning electron microscopy (SEM), photomicrographic analysis, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), etc. It was observed that percentage exhaustion of dye, dye uptake, dye penetration and diffusion coefficient were increased significantly in presence of ultrasound compared to those of dyeing in absence of ultrasound. Moreover, physical properties of the dyed leathers were also investigated. Color rub fastness, perspiration, tensile strength, etc. of dyed leather in presence of ultrasound were higher than that of without ultrasound. SEM analyses of the surface and cross section of the dyed leather showed that fiber structure was not affected by ultrasound. Photomicrographic analysis of cross-section of the dyed leather also showed a deeper penetration of dye in presence of ultrasound. Consequently, dye content in the spent liquor was decreased resulting in a lower environmental pollution.