In a previous article, we reported that oxygen low temperature plasma treatment of wool fibers increases both the dyeing rate and saturation dye exhaustion of acid dyes, despite increased electronegativity of the fiber surface with the treatment. In this article, wool and nylon 6 fabrics treated with oxygen, carbon tetrafluoride, and ammonia low temperature plasmas are dyed with several natural dyes, such as cochineal, Chinese cork tree, madder, and gromwell. The dyeing rate of the plasma-treated wool increases con siderably with cochineal, Chinese cork tree, and madder, but not with gromwell. How ever, the dyeing rate of nylon 6 with cochineal and Chinese cork tree is not changed by the plasma pretreatment. Furthermore, plasma-treated wool fabrics dyed with cochineal and Chinese cork tree have increased brightness compared with untreated wool.

In order to understand the dyeing behaviour of synthetic fibres in supercritical carbon dioxide, the solubility of some disperse dyes in supercritical fluid, as well as the rate of dyeing and the equilibrium adsorption of these dyes, have been studied. Dye solubility was measured by a dynamic analytic method at a range of pressure (7.5–25 MPa) and temperature (50–145 °C). The apparent rate of dyeing was measured and the dyeing isotherm was obtained by plotting the equilibrium dye adsorption against the equilibrium dyebath concentration. Linear isotherms were obtained when poly(ethylene terephthalate) samples were dyed with the disperse dyes. The mechanism of dyeing using supercritical carbon dioxide was discussed by considering the solubility, the dyeing rate and the dyeing isotherm.