Dyeing properties of cotton fibres treated with liquid ammonia

Abstract

Both scoured and sodium hydroxide mercerised cotton fibres have been treated with liquid ammonia atndash33.4°C using commercial operating equipment and then the ammonia removed at 130°C in a hot drum. The moisture regain and water absorbency of the fibres treated with liquid ammonia were increased compared with values on untreated fibres, whereas both these parameters on mercerised cotton fibres were decreased by subsequent liquid ammonia treatment. The fibres were dyed with CI Direct Red 2 and CI Direct Blue 1. Liquid ammonia treatment of the scoured cotton fibres increased the rate of dyeing, equilibrium dye adsorption, standard affinity, heat of dyeing and change of entropy, while the dyeing properties of mercerised cotton were adversely affected by subsequent liquid ammonia treatment.

Cellulose mercerization: Use of amino acid‐glycerol ethers as wetting agents

“…Moisture regain as well as water absorbency are attributed to a swelling of mercerized cotton due to the interruption of hydrogen bonds of cellulose chains 1, 11, 21, 25…”

“…From Table III the following can be concluded: mercerization always results in an increase in K/S value directly related to the dye absorbed on the fiber (Kubelka–Munk law). This is attributed to the increase of the amorphous region with a simultaneous decrease in the crystallinity of cellulose fibrils that consequently permit the water‐soluble dyes to be incorporated into the cellulose structure 1, 5, 10, 11, 21. The presence of wetting agents, both conventional or nonconventional during the mercerization process, is advantageous with respect to the dye absorption.…”

“…A very old and effective finishing is mercerization, which is defined as the treatment of cellulose or cellulose polyester blends with caustic soda, ammonia, or ammonium salt concentrated solution 1, 4. Depending on the temperature, the work may last from a few minutes to several days at a time, with or without tension 1, 4–11. During this finishing, the fibers do not lose their identity, but some important changes take place, such as swelling, an increase of the amorphous region with a consequent decrease of the crystalline one, and a simultaneous change of the geometry of the crystallites from parallel cellulose I to antiparallel cellulose II 1, 12–18.…”

“…Moreover, when the mercerization process is taking place, an increase of tensile strength under tension is observed that may be due to an additional consolidation of weak points as well as the removal of fractions of cellulose with a very low degree of polymerization 21. The effect of all the above is an improvement in dye uptake,5, 9–11 in moisture regain and water absorbency,11 and sometimes in the fiber strength and the luster, depending mostly on the conditions of mercerization.…”

Effects of Dyeing Temperature and Molecular Structure on the Dye Affinity of Polyurethane Films containing Polyethylene Glycol Segments

“…The sorption isotherms were derived from the sorbed dye concentration, [D] f , and the dye concentration in the bath after dyeing, [D] s ; the former was determined by colorimetry after dissolving the films in DMF, while the latter was deduced from the initial concentration in the bath and [D] f . The thermodynamic parameters were calculated by applying the standard method for cellulose fiber systems interacting with direct dyes [7]. The effective volumes of the samples were calculated from the measured area swelling ratios of the …”