Fibrillation tendency of cellulosic fibers-part 3. Effects of alkali pretreatment of lyocell fiber

The influences of pretreatments with different alkalis on the fibrillation tendency of lyocell fiber were investigated. The fibril number (FNpre) decreased after pretreatment in aqueous sodium hydroxide (NaOH) and potassium hydroxide (KOH) solutions at concentrations between 3.0 and 7.0 mol/l, and minimized at 5.0 mol/l. The water retention value of the fiber after the pretreatment (WRVpre) in NaOH and KOH at the concentration where the FNpre was minimized was 0.66 cm3/g. Contrarily, the FNpre with trimethylammonium hydroxide (TMAH) increases with increasing the concentration and weight loss. Analysis using scanning electron microscope suggested the uniform reorganization of the macrofibrils of the lyocell fiber treated with 5.0 mol/l of NaOH solution while the pretreatment in TMAH and LiOH led to the uneven reorganization, resulting in the acceleration of fibrillation. The results indicate that the fibrillation of lyocell fiber is retarded when the fiber structure is uniformly reorganized without the high loss of cellulose component.