Supercritical CO2 Dyeing of Ramie Fiber with Disperse Dye

Dyeing of ramie fiber with C.I. disperse red 74 (DR74) at the temperatures from 343.15 to 403.15 K and under the pressures of 12-20 MPa has been thoroughly investigated using supercritical carbon dioxide (scCO2) as a solvent. Ramie fiber was first treated with alkali and then with benzoyl chloride to improve the affinity and interaction between disperse dye and ramie fiber. The morphological and structure transformations in fiber induced by pretreatment were determined by a Fourier transform infrared spectrometer (FT-IR), X-ray diffraction (XRD), scanning electro-microscopy (SEM), differential scanning calorimetry (DSC), and thermogravimetry analysis (TGA). The modification of ramie fiber with benzoyl chloride was characterized by a degree of substitution (DS). The damage to ramie fiber caused by pretreatment and scCO2 dyeing was determined by stress-strain measurements. The color strength of the fiber was evaluated by K/S measurements. The dyeing effects have been studied by means of time, pressure, temperature, and concentration of dye.