Cationic modification of ramie fibers in liquid ammonia

Anhydrous liquid ammonia was used as a solvent for the cationic modification of ramie fiber using 2, 3-epoxypropytrimethylammonium chloride (EPTAC). The processing parameters, including treatment temperature, treatment time, concentration of EPTAC, and concentration of NaOH were schematically investigated in order to control the properties of the fibers. The optimum parameters for cationic modification in liquid ammonia were analyzed through zeta potential measurement. The modified fibers were dyed in different conditions after modification, and the dyeing behaviors such as exhaustion and fixation properties were carefully examined. The modified fiber in liquid ammonia consisted of a higher number of cationic groups on the fibers compared to the fibers modified in water. The cationization reaction in liquid ammonia significantly decreased the crystallinity and the crystallite orientation of the resultant fibers. The decreased crystallinity slightly decreased the thermal resistance and tensile strength but increased the elongation ability of the fibers. The liquid ammonia cationic modification process turned the appearance of fibers from rough to smooth and lustrous due to swelling of fibers in the solvent. The exhaustion, fixation and wash fastness property of the fibers were improved after the cationic modification in liquid ammonia.