Dyeing performance of cotton fabrics with natural curcuminoid in supercritical carbon dioxide

From 1980s, a new process for dyeing textiles using supercritical carbon dioxide instead of water was developed. When compared with conventional wet dyeing processes, supercritical carbon dioxide dyeing processes have many essential advantages, as carbon dioxide is a benign, nonflammable, non-toxic and inexpensive solvent, and its supercritical state is easy to get (the critical point of carbon dioxide is at 31.1 ̊C and 7.38MPa); in addition, after the dyeing process it can be readily recycled.3 Moreover, the energy and timeconsuming dry procedure is also no longer needed as the dyeing process is water free.4 Therefore, as an innovational and clean dyeing technology, supercritical carbon dioxide dyeing processes are more environmentally friendly and economically attractive for the textile industry.5 To date, the coloration of synthetic fibers, such as polyethylene terephthalate (PET),6 polylactides,7 polyamide 6 and 66,8 with disperse dyes in supercritical carbon dioxide has achieved commercial requirements. But it is still difficult for the dyeing of cotton fabrics in supercritical carbon dioxide. The main reason lies in the facts that disperse dyes have low affinity to cotton fibers.