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Wool pretreated with dimethyl sulfoxide (DMSO) was characterized and its dyeing behavior in non-aqueous green solvents was investigated. Reactive dyeing of wool in deep shades is challenging because the mandatory alkaline aftertreatment to match the fastness of mordant dyes inevitably causes damage to wool keratin. The current study showed that the colorfastness-integrity dilemma could be solved by replacing water with organic solvents as the dyeing medium. Covalent fixation is predominantly favored in solvent dyeing so that excellent colorfastness is achievable at any given shade without alkali aftertreatment. Compared with aqueous dyeing, solvent dyeing was found to give 30% higher covalent fixation on average, which translated to better colorfastness (0.5–1 grade) at higher color depth (Δ K/ S = 1.3–4.9). In addition, scanning electron microscopy, X-ray diffraction and attenuated total reflection-infrared spectroscopy results indicated that DMSO pretreatment induced morphological and structural changes of wool in favor of dyeability. The findings are crucial to the phasing-out of metal-containing dyes for eco-friendly wool dyeing.

The nanoclay, montmorillonite, and some modified nanoclays were used as sorbents for nonionic, anionic and cationic dyes. From the sorption differences among the different dye and clay structures, both chemical and morphological, the sorption forces that played important roles were identified. The nanoclay could easily have a sorption capacity of more than 600 mg sorbate per gram of sorbent at a liquor-to-sorbent ratio of 100 to 1. Furthermore, it could have a sorption of 90% at an initial dye concentration of 6 g/L, or 60% based on the weight of the sorbent, indicating an extremely high dye affinity. This study showed that with certain modifications the nanoclay, montmorillonite, could easily become an excellent sorbent for anionic, cationic and nonionic dyes.

Cotton fabric inkjet printing with acid dyes is investigated using quaternary ammonium (choline chloride (cc)) and two crosslinking agents (DMDHEU and BTCA) to examine dye uptake. The concentrations of chemicals, the finishing conditions, and the inkjet printing processes are explored. With the aid of crosslinkers, acid inks can be used satisfactorily on cotton. Adding CC to the crosslinkers improves acid dye uptake only slightly more than using the crosslinking agent alone. A disadvantage of cc is that the loose dye stains onto white unprinted areas during laundering. The main function of crosslinkers is not only to chemically link the dye to cellulose, but also to form a crosslinked network to block the entrance of the fiber pores where dye molecules have previously penetrated.

One concern associated with wet-on-wet processing is the changing chemical concentration in the pad bath. After processing for several hundred yards or so, chemical add-on considerably decreases, resulting in poor performance properties of finished goods or decreased shade depth. To obtain a constant bath concentration and add-on, an appropriate initial concentration and a reconstitution stream with higher concentration than the initial concentration should be used. The validity of a mathematical model relating parameters in wet-on-wet padding is proven by experimental data from both laboratory and production scales. Using that model, changes in pad bath concentration can be quantitatively described. For given processing conditions and add-on requirements, an initial pad concentration and a different reconstitution concentration can be obtained from the model to assure a constant add-on from the beginning to the end of the wet-on-wet process.

The modified Donnan model, which considers the dye distribution coefficient as a function of salt concentration and property in the dyebath, is used to describe the dyeing behavior of wool with acid dyes and different kinds of salts. This modification is based on the understanding that salt anions are either kosmotropes (water-structure maker) or chaotropes (water-structure breaker). They affect the free energy of the dyebath through their influence on water structures. As is well known, adding salt to the dyebath decreases dye sorption due to its reduction of ionic attraction between negatively charged acid dyes and positively charged wool fibers. However, adding some salts such as sulfate and dihydrogen phosphate can increase dye sorption if the salt concentration is high. This phenomenon cannot be explained by the classic theory of salt functions in dyeing. The modified Donnan model is used to explain quantitatively both the de crease and increase of acid dye sorption on wool with increasing salt concentration.

Traditional anionic dyeing of cotton requires large amounts of salt to assist dye sorption. This paper reports a method of using trimethylolmelamine (TMM), a com mon durable press finish, to treat cotton for dyeing. TMM pretreated cotton has re markably improved affinity for anionic dyes and no longer needs the assistance of salt in the dyebath. Furthermore, effluents from such processes contain much less dye than effluents from ordinary salt-assisted dyeings. This technology not only increases the efficiency of dyeing without salt, it also considerably decreases the burden of effluent treatment. By this method, cotton can also be dyed with acid dyes.

Frontal analysis gives retention volumes of basic dyes on acrylic fabric, rolled and inserted into a liquid chromatography column. The retention volumes indicate differences in adsorption and therefore in compatibilities of standard dye mixtures. A simple and useful relation, Cv = Cvo + mR - Cv,0, results where m is a parameter fitted to the data, Cv0 is the compatibility difference between Cvo and Cv when R = 0 ( i.e., elution times are identical), and Cvo is the compatibility of one of the two dyes in the mixture. Hence, a new approach is proposed that not only allows determination of Cv using frontal analysis with an LC apparatus, but also defines compatibility in an objective manner as a continuous function.

Direct dye adsorption isotherms have been obtained using a rolled cotton fabric stationary phase in a liquid chromatography column. Both frontal analysis and minor disturbance methods were tested. The minor disturbance method was not useful due to the slow rate of dye equilibration relative to the velocity of the pulse of dye passed through the fabric column. In comparison, the frontal analysis technique gave results similar to those obtained with standard equilibrium adsorption measurements in a beaker. This method permits determination of whole fabric dye sorption using liquid chromatography instrumentation in a manner that yields facile and quantitative measures of dye compatibility, as described in Part II of this paper.

A novel rolled stationary phase using whole fabric has been developed for liquid chromatography. This paper describes the column and its properties and use in characterizing pore volumes of the whole fabric. The logistic model gives a good fit of the measured void volume data obtained by size exclusion chromatography. With the help of this function, both pore size and surface area distribution of cotton and ramie fabrics can be obtained. The relationship between pore shape and surface area is discussed. Cotton has 100 to 200% more void volume and surface area than ramie (for all sizes of pores). Increasing the temperature from 30 to 60°C does not significantly influence either the total void volume or surface area of cotton and ramie. The void volume and surface area of cotton as determined by this rolled fabric column method are comparable to previously reported data.

Concentration of water soluble direct, acid, basic, and reactive dyes occurs when dilute solutions are frozen at a temperature below the melting point and above the eutectic point of the solution. When freezing is done in still solution, a concentration of up to 500% is achieved in one step, with the dye solution collecting in an oblately spheroidal liquid pocket surrounded by clear ice containing voids, formed from air pockets, radiating outward. Three repetitive freezing cycles concentrate the dye 13,000%. The higher the water solubility of the dye, the lower the ability to concentrate during freezing. The freezing rate of four acid and direct dyes had no close relationship with the size of the dyes studied. Over a larger molecular weight range, an effect was observed for other kinds of molecules. Freeze concentration of salt solution (MW = 58.5 ) gives almost a 700% concentration, detergent solution (sodium dodecyl sulfate, MW = 288.4) gives 400%, and bovine serum albumin, a large water soluble macro molecule (MW = 66,200), gives 160%. A theory is presented suggesting that the concentration effect and the formation of the central sphere are consistent with min imizing of the free energy of the overall system. This simple technique may find application in the concentration of heat sensitive, labile dyes for analytical purposes, as well as in the recovery of dyes and other chemicals on a bench scale.