Study On The Modification Of Ramie Fiber And Dyeabililty

Ramie, also called China grass, is one of the excellent textile material. It ismainly planted in China and other Asian countries. Ramie fiber, stripped from stem bastof the plant, has excellent properties such as high tensile strength, excellent thermalconductivity, coolness, ventilation function, moisture absorption, antibacterial functionand so on. The ramie fiber and ramie fabric are important industrial raw materials.There are lots of hydroxy groups in the molecule of ramie fiber. The hydroxy groupscan be combined with dye by covalent bond in the dyeing, play an important role in thedyeing process. However, the dyeability of ramie fiber is still poorer than the wool.Dyeing of ramie fiber with reactive dye was carried out under alkaline condition,therefore the reactive dye may hydrolyze and results in poor dye uptake. Besides, whenthe ramie fiber is immersed in dye bath, the presence of many negative charges on thesurface of fiber weakens the reaction affinity between the dye molecules and the fiber,because the negative charges may repulse the dye anion and decrease the substantivityof dye to fiber. In order to improve the uptake of ramie fiber, many electrolytes areadded in the solution in traditional dyeing process which results in the environmentalpollution.According to the existing problems in the dyeing process of ramie fiber,modification of ramie fiber is adopted to improve the dyeability. In this paper, severalworks have been done based on previous modification methods.A modification procedure for ramie fiber using 3-chloro-2-hydroxypropyltrimethylammonium chloride as a cationic agent and an alkali as a catalyst was developed in thispaper. The morphological and structural transformations of the fiber induced bymodification were determined by X-ray diffraction (XRD), differential scanningcalorimetry (DSC), and thermogravimetry analysis (TGA). The technology of thismodified method is simple, so it may have a good prospect of industrialization.The chelate molecule, ethylenediamine, was incorporated onto the surface of ramiefiber via sequential reactions of the hydroxyl groups on ramie fiber withepichlorohydrin followed by the chelating agent. The performance of the modifiedmaterial (CelNH) was characterized by Fourier transform infrared spectroscopy (FI-IR), X-ray diffraction (XRD), scanning electron micrographs (SEM), thermogravimetryanalysis (TGA), UV-Vis, and elemental analysis. The effects of ethylenediamineconcentration, reaction temperature and time on the modification degree are studied.The mechanism of dyeing of ramie fiber was studied with C.I. reactive red 2. Thepossible interaction forces of dye molecule and ramie fiber were electrostatic, van DerWaals, and/or hydrogen-bonding. After the fiber was modified with cationic agent, theZeta potential on the surface of ramie fiber decreases, which accelerates the closing rateof dye to the fiber. Meanwhile, dye may combine with the cationic groups through ioniclinkage.After modified with ethylenediamine, the dye molecules were fixed on fiber viacovalent bond, the dye uptake and color strength of modified fiber were improved.