Dyeing and Mechanical Properties of Cotton Fabrics Treated with Sodium Hydroxide/Liquid Ammonia and Liquid Ammonia/Sodium Hydroxide

Abstract

Desized and scoured cotton fabric is treated in a two-step process with sodium hydroxide/ liquid ammonia and liquid ammonia/sodium hydroxide to investigate the effect of the treat ment sequence. Crystallinity, moisture regain, water absorbency, dyeability, and KES mechan ical properties are measured. Despite a considerable decrease in crystallinity with both treatments, water absorbency decreases with NaOH/NH₃ and increases with NH₃/NaOH compared with the untreated fabric. Furthermore, the NaOH/NH₃ treatment decreases the early dyeing rate with CI Direct Blue 1, whereas the NH ₃/NaOH treatment increases the rate remarkably compared to the untreated fabric. Nevertheless, saturation dye uptake with the same dye increases with both treatments compared with the untreated. As a measure of fabric hand, shearing and bending hysteresis curves are obtained with a KES instrument. The shearing modulus and shearing hysteresis width of the NaOH/NH₃ treated fabric are much smaller than those of the NH3 treated fabric, while those of the NH₃/NaOH treated fabric are smaller compared with the NaOH treated fabric. From these results, it is clear that two-step processes such as NaOH/NH₃ and NH₃/NaOH are much more effective for softening hand than the NH3 and NaOH treatments independently.