Supercritical Carbon Dioxide Dyeing of Cellulosic Woven Textiles using Madder Dye and Gallnut Mordant.

Supercritical carbon dioxide (scCO2) dyeing technology can be identified as a disruptive innovation in the textile industry for dyeing synthetics. However, the usage of this technology for cellulosic fabrics is still in the research stage with an area of opportunity for improvements. This thesis explores the ability of using scCO2 dyeing technology for dyeing two cellulosic fibers, cotton and modal with a naturally derived dye, Madder (Rubia Tinctorum L.). The work was carried out to find the effect of dyeing time, temperature as well as a naturally derived mordant, Gallnut (Quercus Infectoria) and water in the fabric on the dye uptake, levelness, and fixation. A woven fabric with 50/50 cotton/modal content was dyed using a static scCO2 dyeing system using madder, gallnut, water as the only inputs in varied parameter combinations and the dyed samples were measured for color before and after washing to calculate for the dye uptake, levelness and fixation. A pH evaluation of the dye and fastness evaluation of the washed sample were also conducted for further analysis. The key findings specific to this work were identified as firstly, high pH sensitivity of the dye resulting in the omission of measuring K/S data ratio for the calculation of fixation after washing. Secondly, the positive relationship of the water to the dye uptake but the negative relationship to the levelness. Thirdly, the higher dye uptake of cotton compared to modal. Lastly, the comparability of color fastness results of the fabric to the results reported in contemporary studies. This work implies the possibility of the usage of natural dyes in cellulosic dyeing with scCO2 dyeing technology.