| It is difficult for meta-aramid to be colored to deep shade with aqueous medium because of its extremely high glass-transition temperature and high crystallinity and orientation degree.In this paper, dyeing characteristics of meta-aramid were investigated in supercritical carbon dioxide fluid by employing trichromatic disperse dyes and environmental and non-toxic carriers to achieve the better color depth and color fastness. The dyeing mechnism of meta-aramid was proposed in supercritical carbon dioxide fluid. In addition, the influence of supercritical carbon dioxide fluid on the dyeing performance of meta-aramid was also analyzed.Meta-aramid was treated in supercritical carbon dioxide fluid under the treatment conditions of 140°C and 60 min with different pressures. SEM/EDX experimental results of this study proved that, surface roughness and oxygen-containing polar groups of the meta-aramid fiber were increased with the rising of the treatment pressure. The C concentration was decreased from 69.64% to 65.41% while the N concentration was increased from 14.41% to 19.37%, but the change of N concentration was not significant. The contact angle against water was reduced significantly from 139.8° to 124.5°. The crystallinity of the meta-aramid samples was increased gradually due to the re-arrangements and re-crystallizations of the molecule chains generated. The water vaporization temperature and the thermal decomposition temperatures of the meta-aramid were improved with the increase of the treatment pressure. The breaking force, the tensile strength and the elongation at break for treated meta-aramid samples were also enhanced in comparison with that for the untreated samples, which was 1196.71 N to 1237.86 N, 48.43 MPa to 49.46 MPa, and 53.58% to58.61%, respectively. Moreover, there was no obvious change in the antistatic property of the meta-aramid samples.Using supercritical carbon dioxide fluid instead of water as solvent, dyeing of meta-aramid was investigated with C. I. Disperse Blue 79, C. I. Disperse Red 60 and C. I.Disperse Yellow 114. It was found that the swelling and plasticization effect of supercritical carbon dioxide fluid could lead to a decrease in Tg, thereby improving the dyeing performance of the meta-aramid to a certain degree. The dyed meta-aramid has a good color fastness. The fastness to washing and rubbing was rated at 4-5 and the light color fastness was rated 4.Meta-aramid was dyed in supercritical cabon dioxide fluid with the carriers of dimethyl terephthalate, CINDYE DNK and ethyl alcohol. The results showed that the dyeing performance of meta-aramid was improved significantly by adding carriers in supercritical cabon dioxide fluid. Comapred with the undyed meta-aramid, CINDYE DNK resulted in the biggest improvement for meta-aramid’s dyeing performance due to its similar structure to meta-aramid. Meta-aramid was dyed with C. I. Disperse Blue 79, C. I. Disperse Red 60 and C.I. Disperse Yellow 114 in supercritical cabon dioxide fluid by employing CINDYE DNK. The optimium color depth, which was higher than 4.5, of meta-aramid was obtained in supercritical cabon dioxide fluid with a temperature 140 °C, a pressure 30 MPa, a dyeing time70 min, a dye concentration 4.5%, a CO2 flow 50 g/min and a carrier concentration 80%. Themeta-aramid dyed in supercritical cabon dioxide fluid with CINDYE DNK has an excellent color fastness. The fastness to washing and rubbing were ratedat 4-5 and 5, respectively. The light color fastness was rated above 4. Furthermore, the dyeing models for meta-aramid in supercritical carbon dioxide fluid was proposed. The dyeing thermodynamics and kinetics of meta-aramid were also studied with CINDYE DNK. Accordingly, the rationality of the dyeing models for meta-aramid was validated in supercritical cabon dioxide fluid. |
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