**3.3. Zeta potential**

(B), showed a strong relationship between average particle size and light-transmission/ attenuance over the size range examined by both these approaches, as demonstrated by the

tributions obtained during these initial experiments, we were only able to demonstrate a cor‐ relation over a small size. The digital image method was developed further on account of its

**Figure 3.** (A) Pigment average particle size versus attenuance (D) using UV/Vis analysis. (B) Pigment average particle

There was a very interesting phenomenon of the particle size distribution of Pigment Red CI 170 with the increase of the cationic siloxane dispersant. In order to clearly describe the dis‐ tribution process of UMP in water, a experiment was proposed according to the principle of physical chemistry. UMP could not be well dispersed in water with the absence of disper‐ sant. Then, a small amount of dispersant was added into the system. Since the siloxane group of dispersant showed great affinity to the UMP, it tended to anchor on the surface of

Stability of aqueous UMP dispersion is referred to that colloidal properties such as Zeta po‐ tentials, viscosity, and storage stability will not change in certain period. It's an important performance of UMP dispersion. Disperse stability can be supported by two generally mechanisms: steric stabilization and charge stabilization. Steric stabilization is due to steric hindrance resulting from the adsorbed dispersing agent, the chains of which become solvat‐ ed in the liquid medium, thus creating an effective steric barrier that prevents the other par‐ ticles from approaching too close. Charge stabilization is due to electrical repulsion forces, which are the result of a charged electrical double layer surrounding the particles. The charged electrical double layer developed around the particles extends well into the liquid medium, and since all the particles are surrounded by the same charge (positive or nega‐

size versus light-transmission using image analysis

UMP particle.

**3.2. Disperse stability**

potential to allow parallel analysis of multiple samples from the same image [39].

values of the polynomial trend-line. Because the limited nature of the particle size dis‐

high R2

86 Eco-Friendly Textile Dyeing and Finishing

The Zeta potentials of UMP dispersion are analyzed to estimate their disperse stability. The stability of UMP dispersion determined by forces among the UMP particles. When the re‐ pulsive force is higher than attractive force, the UMP particles will stably disperse into the media. Otherwise, the UMP particles will arregate together. In the UMP dispersion with pol‐ ymer dispersant, the repulsion forces among particles produced by the adsorbed polymer include static-electronic and steric repulsion [40]. The former can be measured by the Zeta potentials, and the latter is closely connected with the thickness of adsorbed polymer layer. The studies on the change of Zeta potentials and thickness of adsorbed polymer layer after the addition of solvent are important in understanding the effects of solvent on the stability of UMP dispersion [35,41].

The dispersion mechanism may be interpreted with a pair of electricity layers principle. Al‐ though many cationic dispersants gathered on the UMP surface neighbourhood, the quiet balance of positive negative charge didn't change. The cation on the UMP surface adsorbed a great many anions. With cation gathering gradually on the UMP surface, a pair of electrici‐ ty layers formed. The particles stably existed in dispersion system for the electric charge re‐ jected function mutually. An optimum dispersant dosage would exist, which promoted the formation of double electricity layers [16,42].

#### **3.4. Color properties**

UMP particles which are dispersed finely in dispersions enhance the color depth of UMP dispersions (e.g. transmittance, chroma, and lightness) and improve color display perform‐ ance. The transmittances were enhanced with decreasing the mean size of dispersion (Figure 4). A color analysis program estimated the lightness (L\*) and chroma (C\*) from a spectrum of dispersion samples at a wavelength of 380 to 780 nm based on the L\*a\*b\* Color System and D65 light source. The finer sizes of UMP particles in dispersion resulted in the higher lightness (L\*) and chroma (C\*). Serious aggregation of UMP particles without a dispersant in the dispersion would be performed. Holding the supercritical fluid-assisted dispersion process at the supercritical region conduced to better dispersion [43].

**4. Dyeing properties**

priate for all spices.

fixation agents [48].

**4.1. Dyeing cotton fabric with UMP**

In order to improve the dyeability with UMP, the cationic pretreatment of fabric is used. It can introduce positively charged sites on cotton fabric. Without pigment modification, there are two inhibiting factors. Firstly, pigments are insoluble and have no affinity for cotton and, secondly, the surfaces of pigment particles are usually negatively charged. UMP dyeing has several noticeable advantages compared to dyes. This method is a short process, simple operation, saving energy consumption and low costs, and matching intui‐ tive easy color imitation, steady color hue, hiding power. Because UMP particles have no affinity for fibers, the UMP dyeing fibers does not exist the selective problem and is appro‐

Preparation, Characterization and Application of Ultra-Fine Modified Pigment in Textile Dyeing

http://dx.doi.org/10.5772/53489

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There are many reports on cationic modification of cotton. Karrer researched the cationic pretreatment to the cellulose fiber [44]. Guthrie studied the cationic pretreatment of cellulose fiber and dyed it with acidic dye [45]. The chemical modification of cotton to promote dyea‐ bility, light fastness and washing fastness has been researched by Cai [12]. Wang investigat‐ ed chemical modification of cotton to promote fiber dyeability [46]. Burkinshaw analysized cationic pretreatment of cellulose fiber to improve the dye reactivity [47]. Hauser examined the dyeing behavior of cotton that had been rendered cationic by reaction with 2,3-epoxy propyltrimethylammonium chloride and the result showed that excellent dye yields and color fastness properties were obtained without the use of electrolytes, multiple rinsings or

**Figure 5.** Effect of cationic reactant concentration on pigment exhaustion and the K/S value

**Figure 4.** The color analyses from the four representative samples of dispersions. (ο), Lightness; (•), chroma

Color properties are presented the color of the UMP dispersion. The absorbance of UMP hy‐ drous dispersion is slightly larger than that of containing organic solvents. The change is mainly attributed to the disparate polarities of the solutions. In these two solutions, while the polarity of solvent UMP dispersion, which contains more ethanol, is weaker. The color of UMP is aroused by the π→π\* energy transition when the chromophore groups are irradi‐ ated. The weak ionization of the UMP increases in a solution with high polarity (such as H2O), and the electric charge in the conjugated system can transport more easily, which leads to an increases in the absorbance. However, the maximum absorption wavelengths for both systems with or without solvent nearly remain the same. This indicates that the chro‐ mophore groups of the UMP are not damaged in the UMP dispersion containing organic solvent and the conjugated systems are essentially not altered, therefore, the color hue of the solvent UMP dispersion remains identical to that of the UMP hydrous dispersion [35].
