The dyeing of polyester with disperse dyes has been practiced for the last 60 years. Nevertheless, the dyeing recipe is typically decided by experience based on dye house experts’ judgment. This study aims to provide a fundamental understanding of the overall polyester dyeing process, from dye uptake by fibre in a microscopic view, via analysis of the coloration of dyed product, to the operational optimization of the actual process. Through such an understanding, a better process for obtaining a product of the desired quality can be developed. For this, bench scale dyeing experiments were carried out in a specially designed dyeing tank and dye uptake by the fibre was monitored by dye solution sampling. The dye uptake rate was related to the structure and properties of polyester. Plastic...[ Read more ]

The dyeing of polyester with disperse dyes has been practiced for the last 60 years. Nevertheless, the dyeing recipe is typically decided by experience based on dye house experts’ judgment. This study aims to provide a fundamental understanding of the overall polyester dyeing process, from dye uptake by fibre in a microscopic view, via analysis of the coloration of dyed product, to the operational optimization of the actual process. Through such an understanding, a better process for obtaining a product of the desired quality can be developed. For this, bench scale dyeing experiments were carried out in a specially designed dyeing tank and dye uptake by the fibre was monitored by dye solution sampling. The dye uptake rate was related to the structure and properties of polyester. Plasticizing effect of one common carrier and solubilizing effect of surfactants were investigated individually. These effects on the dye uptake rate were related to the color evenness and the color of the final product based on the analysis on the final coloration in the CIE L*a*b* Colorspace. Similar monitoring system on dyeing cotton with reactive dyes was also carried out, showing the capability of the experimental setup for various situations. With the understanding on the impact of various effects on the quality of the dyed product, several schemes for process improvement have been proposed. For polyester dyeing, the duration at the highest temperature is reduced by 12 minutes, which is significant in energy saving. For cotton dyeing, the overall dye uptake is increased from 60% to 63%. The washing efficient is also improved, which helps saving one sixth of liquor in the washing process. These promising results prove that the experimental setup is capable of enhancing the dyeing process in a systemic way.