Effects of a pretreatment with N‐methylmorpholine‐N‐oxide on the structures and properties of ramie

Abstract

To improve the dyeing properties of ramie, the ecofriendly organic solvent N-methylmorpholine-N-oxide (NMMO) was used to substitute sodium hydroxide as a ramie-fiber swelling solvent. Through padding and baking pretreatment, ramie fabric was modified by an NMMO aqueous solution. Ultraviolet-visible spectrophotometry, Fourier transform infrared spectroscopy, X-ray diffraction, and differential scanning calorimetry were used to investigate the effects of NMMO pretreatment on the structure of the ramie, whereas the color strength (K/S, where K is the light absorption coefficient and S is the scattering coefficient), adsorption isotherm, and dye uptake rate curve were measured to investigate the effects of NMMO pretreatment on the dyeing properties of the ramie. The results show that the ramie fiber experienced a limited and irreversible swelling because of the partial breakage of interhydrogen and intrahydrogen bonds of cellulose molecules in the amorphous area, but the crystal and chemical structure of the ramie fiber did not change obviously under the experimental conditions. The K/S value of the NMMO-modified ramie fabrics dyed with reactive dyes increased by about 100%, and the dye uptake increased by 27.88% compared to that of the raw sample, whereas the standard affinity and diffusion coefficient value of the reactive dyes on the NMMO-modified ramie fabric were higher than those of the raw ramie fabric.

Low Temperature Softening Modification of Ramie Fabrics

“…However, this method requires for a large consume of alkaline and may cause environment pollution. Many new modifications have been developed, such as N-methylmorpholine-N-oxide (NMMO) modification [6], enzymatic modification [7], and physical methods (singeing, shearing, sand washing, etc.) [8].…”