Heats of Dyeing of Direct Cotton Dyes on Cellulose: A New Thermodynamic Approach to the Determination of Activity of Direct Dyes in Cellulose

Abstract

Heats of dyeing of Chrysophenine G, Cl!lorazol Sky Blue I T , and Congo Red 011 cotton, viscose, and cul)raiiiiiioiiiiiiii rayon have been deterniinetl. It is shown that, except for the initial low concentration of adsorbed dye, the values of heat of dyeing remain more or less the same over a fairly wide range of concentration of adsorbed tlye, and that beyond a critical dye concentration, the values tend to decrease continuously lvlien the proportion of the adsorbed dye is increased. Values for the critical concentration of adsorbed dye beyond which the values of heat of dyeing tend to decrease agree closely with values for (lye adsorption at which niasiniuin voluine contraction in the substrate takes place, as observed from density ineasurenients, and also with values of dye concentrations where masiniuni estent of oxidation of cellulose takes place during catalytic oxitlation of the fiber substance by sodium hypochlorite iii presence of the dye. X ne\v tlierniodynaniic approach has been developed to express the activity of the dye in a cellulosic fiber substance in terms of the fraction of the total sites occupied at a particiilaistage of dyeing. Based on this thermodynaniic approach, affinity values of the three direct dyes for the three cellulosic fibers under different experiniental conditions Iiave I,een tletermineti ; the validity of the treatment is discussed.

Ionizable Groups in Fibers and Their Role in Dyeing. An Examination of the Sorption of Anionic Dyes by Cellulosic Fibers and Films

“…The data in suggest that the'dye-fiber interactions are extremely concentration dependent, increasing in magnitude as the dye concentration decreases. This is supported by independent evidence on the apparent heats of dyeing in these systems [3].…”

Changes in the intra- and inter-fibrillar structure of lyocell (TENCEL®) fibers caused by NaOH treatment

“…This may result in decreased accessibility to the functional groups in the amorphous region. As already stated the swelling pressure due to the alkaline solutions can have a large The increase in overall crystallinity is assumed to be responsible for the decreased moisture content (Ant-Wuorinen and Visapaa 1958; Daruwalla and D'Silva 1963). Cellulose II can form hydrates (C 6 H 10 O 5 Á 1/3H 2 O or C 6 H 10 O 5 Á 1/2H 2 O) on sorption of water vapor, but has no water in the unit cell.…”

“…The addition of salt to the dye bath reduces the electrostatic barrier and improves the substantivity, i.e. dye absorption to the fiber (Koh et al 2004;Daruwalla and D'Silva 1963).…”

The Influence of Different Electrolytes on the Interaction of Chlorazol Sky Blue FF with the Cotton Fiber Surface in Aqueous Solutions

“…Since the previous work [28] showed that much better agreement between ex- (The limiting co-area is defined here as the average surface area of cellulose per adsorbed dye anion for a given value of C~)' Thermodynamic values of standard affinity -AlA 0 for the adsorption processes were calculated from the isotherm data by using the following equation which is a modified form of Equation 1. where 9 = ~~ ~ The use of Equation 2 for calcu-[D lating affinities indicates that the activity of the adsorbed dye is defined by the term 1 e ~ [9,10,13] and the mean activity of dye present in the internal cellulose phase i, by the term [at];. If Equation 2 is valid, a plot of log 0 .…”