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Modified curcumin, which has the advantages of low toxicity, high solubility, and little color change after modification, is very suitable for nonaqueous supercritical carbon dioxide cotton dyeing. However, the existing curcumin modification technology focuses on improving its solubility. Modified curcumin is directly adsorbed onto cotton fabrics, and the main interaction forces are van der Waals forces, which causes the poor fastness of modified curcumin to dyed cotton fabrics. In this study, reactive groups (hydroxyalkyls) were introduced into curcumin to enhance its fastness to cotton fabrics. The results showed that, similar to alkyl groups, hydroxyalkyl groups can enhance the color depth of dyed cotton fabrics by elevating the solubility of modified curcumin in supercritical carbon dioxide. The higher the solubility of modified curcumin in supercritical carbon dioxide was, the higher the K/S value of the dyed cotton fabric. Furthermore, the hydroxyl groups on the modified curcumin could form ether bonds with the hydroxyl groups on cotton fabrics. Therefore, the washing and rubbing fastness of hydroxyalkyl-curcumin-dyed cotton fabric was better than that of alkyl-curcumin-dyed cotton fabric.

The supercritical carbon dioxide (SC-CO2) dyeing technology is a green dyeing technology, and the usage of natural dye makes SC-CO2 dyeing technology safer and more environment-friendly. Nevertheless, after using natural dye in SC-CO2 dyeing, the color depth and fastness of dyed natural fabric are poor. In this study, alkyl and hydroxyalkyl groups were grafted onto alizarin, which is a natural dye, to elevate the color depths and fastness of alizarin-derivative-dyed natural fabric. The results demonstrate that the color depths of alkyl-alizarin-dyed and hydroxyalkyl-alizarin-dyed natural fabrics were increased. This has to do with the increase in the solubilities of alkyl alizarin and hydroxyalkyl alizarin in SC-CO2. The hydroxybutyl-alizarin-dyed wool displayed the best color depth (K/S value: 6.44). And the hydroxyalkyl-alizarin-dyed natural fabric showed good washing fastness and rubbing fastness (about 4–5 level), because that hydroxyalkyl alizarin could be linked by a covalent bond to the natural fabric.

Compared with traditional water dyeing, supercritical carbon dioxide (scCO2) dyeing is more environmentally benign. scCO2 is widely used as a green solvent in dyeing synthetic fibers. However, studies involving dyeing natural fibers in scCO2 are scarce. The commonly used methods result in corrosion of the dyeing equipment. Thus, the development of new special dyes suitable for scCO2 dyeing is necessary; in addition, insight into the dyeing mechanism is important in promoting the design and synthesis of dyes for wool fibers in scCO2. On the basis of our previous work, a possible dyeing mechanism in which the dyes exhibit hydrophobic interaction with keratins is proposed. The N═N bond twisting in azo dyes promotes the dyes embedding into the spaces of the alpha helices in proteins. According to the proposed mechanism, two new azo disperse dyes (azo thiazole-N(CH3)2 and azo thiazole-OCH3) were synthesized; these dyes enable the dyeing of wool fibers in scCO2. Meanwhile, the introduction of a succinimidyl est...

An obvious limitation of curcumin is its inability to achieve a deep color depth, which is caused by curcumin's low supercritical carbon dioxide solubility. In this study, alkyl groups (ethyl, butyl, hexyl or octyl) were introduced to curcumin to achieve better solubility and dyeing ability. The results showed that both the solubility and dyeing ability of curcumin increased after alkyl grafting. The best dyeing ability was achieved by using butyl curcumin to dye silk in the presence of dimethylsulfoxide (DMSO). This phenomenon is closely related not only to the high solubility of butyl curcumin but also to the increase in the silk specific surface area, resulting from the synergistic effects of supercritical carbon dioxide and dimethylsulfoxide.

The reason of color differences caused by different degree of esterification disperse dyes were investigated by disperse orange 30, disperse red 167:1, disperse blue 79:1 with different degree of esterification. The results showed that the changes of light absorbance abilities and melting points caused by ester groups had no obvious correlation with the color differences caused by ester groups. The changes in the solubilities and affinities caused by the ester groups were the fundamental reason for the changes in the dyeing properties of disperse orange 30, disperse red 167:1 and disperse blue 79:1. As a joint result of the decrease in solubilities and affinities, the dye sorption in polyethylene terephthalate of unesterified disperse orange 30, unesterified disperse red 167:1 and unesterified disperse blue 79:1 were reduced by 37.7%, 83.6% and 54.6%, respectively, compared with those of the corresponding completely esterified dyes.

In this paper, using carbon dioxide as a dyeing medium, some basic color and mechanical behaviour data for yak hairs were firstly obtained with different parameters. The effects of system temperature, pressure, time and depressurization rate on yak hairs were investigated in terms of the color strength, the short fiber content, the breaking strength and the elongation at break. The results indicated that the short fiber content of yak hairs was increased with the raising of system temperature, pressure, time as well as depressurization rate, while the breaking strength and the elongation at break of yak hairs were decreased with the increase of system temperature, time as well as depressurization rate. Moreover, supercritical carbon dioxide for the fracture mechanism of yak hairs was proposed based on the Bernoulli’s principle and Boyle’s Law.

As one of the most important coumarin-like dyes, disperse fluorescent Yellow 82 exhibits exceptionally large two-photon effects. Here, it was firstly introduced into the supercritical CO2 dyeing polyester fabrics in this work. Results of the present work showed that the dyeing parameters such as the dyeing time, pressure and temperature had remarkable influences on the color strength of fabrics. The optimized dyeing condition in supercritical CO2 dyeing has been proposed that the dyeing time was 60 min; the pressure was 25 MPa and the temperature was 120 °C. As a result, acceptable products were obtained with the wash and rub fastness rating at 5 or 4–5. The polyester fabrics dyed with fluorescent dyes can be satisfied for the requirement of manufacturing warning clothing. Importantly, the confocal microscopy imaging technology was successfully introduced into textile fields to observe the distribution and fluorescence intensity of disperse fluorescent Yellow 82 on polyester fabrics. As far as we know, this is the first report about supercritical CO2 dyeing polyester fabrics based on disperse fluorescent dyes. It will be very helpful for the further design of new fluorescent functional dyes suitable for supercritical CO2 dyeing technique.