A Review on the Different Methods of Clearing Disperse Dyes from the Surface of the Dyed Polyester Fibre

The deposits of dispersed dyes on dyed polyester fibres are an important problem in polyester fibre dyeing that should be tackled properly. These dyes deteriorate the wash, rubbing, and sublimation fastness and the brightness of the dyed fibres, especially deep-dyed ones. Therefore, clearing these surface dyes is necessary. Conventionally, a reduction clearing process is used to remove the surface dyes, in which sodium dithionite, a reductant, and sodium hydroxide, an alkaline, are used. This process has a significant part in removing surface oligomers and auxiliaries, such as carriers. Unfortunately, this process is not environment friendly, and the derivatives of its chemicals are toxic to human health, and there are technological and economic issues associated with this process. In recent years, numerous research for removing surface dispersed dyes by alternative, less-pollutant, and more efficient processes have been proposed. These alternative processes include surfactants, enzymes, and other reductants, oxidative clearing, plasma, electrochemical methods, and the application of easily clearable synthesized dyes. Each of these proposed processes has its own pros and cons, and they have special needs. In the present review paper, various processes of clearing surface dispersed dyes from the dyed polyester fibres are investigated and compared with the traditional reduction-clearing process.</em>