Study On The Dyeing Of Poly (Ethylene Terephthalate) And Polyamide Fibers In Supercritical Carbon Dioxide

The conventional dyeing process requires a large amount of water as a dyeing medium causes the emission of wastewater with various toxic chemical additives to the environment. The supercritical fluid dyeing (SFD) is a waterless dyeing process, in which supercritical carbon dioxide (SCCO2) is used as the dyeing medium and the emission of wastewater is avoided.This paper presents the properties of supercritical carbon dioxide (SCCO2) and provides an overview of the status of the research.The dyeing experiements of poly(ethylene terephthalate) and polyamide fibers in SCCO2 are carried out at different temperature (325K -416K), pressure (10MPa - 24MPa) and with different time (5 - 60 minutes). The effects of temperature, pressure and time have been investigated. The color fastness to washing and the color fastness to rubbing were tested, and the partition coefficients (Keq) of dyes between polymer phase and supercritical carbon dioxide phase were calculated from the equilibrium dye uptake and the solubilities of dyes in supercritical carbon dioxide.The dyed samples were evaluated using colorimetry and the extraction of dyes from the fabric, and the value of color deepness (K/S) was also measured.The amount of all dyes on the fabric rises with the increases of temperature and pressure, or with the increase of the density of the carbon dioxide.The partition coefficients (Keq) of dyes between polymer phase and supercritical carbon dioxide phase decreases with the rising temperature or with the rising density of the carbon dioxide.The result showed that the desired dyeing effect can be obtained in 20 to 30 minutes, under the pressure arranging from 16 to 18 MPa and at about 373 K for polyamide and 393 K for PET respectively. The color fastness to washing and the color fastness to rubbing is the same as that being dyed in the water.