| In recent years, the use of InkJet printers in numerous applications has increased dramatically. Such printers offer a low cost, high quality and comparatively noise-free option to other types of printers commonly used with computers. Many of the inks that have been used in the past with inlcjet printers are primarily comprised of dyes contained within organic or water-based carrier liquids. Although such inks may offer satisfactory performance in certain applications, the present trend is away from such systems, since such systems tend to produce images that lack of the light stability and durability required for outdoor and similarly demanding applications. In order to solve this problem, inks prepared by using pigments, instead of dyes, as colorants have been investigated.Quinacridone pigments have been known for a long time and have acquired great industrial importance for pigment coating materials. The dispersion of quinacridone pigments is one of the most difficult and crucial processes in the production of aqueous inks for inkjet textile printing. A colloid suspension with pigment particles dispersed in aqueous medium is thermodynamically unstable; thus, dispersant is normally used to stabilize the system.First of all, a series of polymers with different structures were chosen and synthesized. We present investigations on the adsorption of different types of water-soluble polymer on the surface of C. I. pigment Red 122 (quinacridone red pigment) particles. The polymer-coated particles are characterized by electrokinetic studies; sedimentation studies and rheology studies. The aim of the current work is to develop an appreciation of the interaction forces that arise in concentrated pigment dispersions due to the presence of polymer.In an electrokinetic experiment, a portion of the double layer is sheared off at a plane in the solution, which is called a slipping plane or a plane of the shear; the potential at this plane is termed the ζ-potential. Generally, it is a very useful method by measuring the ζ-potential of a disperse system to estimate the stability of this system according to its electric phenomenon. A higher absolute value of ζ-potential denotes a higher stability of the disperse system. The effects of the polymer concentration, pH and ionic strength of the system on the ζ-potential of pigment particles have been studied. The stability of quinacridone red pigment suspensions was compared through the ζ-potential measurement, when the pH (from 3 to 10) and the ionic strength (from 0 to 0.05 mol dm-3) of the system were varied over a wide range. Compared with P(AA-AM-DMDACC) and PVP polymer, SMA-NH4 polymer studied could give a considerable enhancement of the absolute ζ-potential value of the quinacridone pigment particles if the pH and the ionic strength of the system werewell controlled. The quinacridone pigment suspension maintained stable when the pH of the system was above 7 and the ionic strength of the system was below 0.001 mol dm-3. Charged quinacridone pigment particles were accomplished by SMA-NBU polymer adsorption, resulting in electrosteric stabilization.As for sedimentation studies, the stability of the quinacridone pigment suspensions is evaluated by comparing the absorbance of the top portion of the pigment suspension. A high absorbance indicates a high stability of the dispersion system, whereas a low absorbance indicates a settled state of the quinacridone pigment particles. The added SMA-NBU polymer could increase the stability of the suspension because of its electrosteric effect. With increasing the pH of the system, the system became stable under the basic condition. While with increasing the ionic strength of the system, the pigment particles started to settle. The added P(AA-AM-DMDACC) and PVP polymers had little effects to increase the stability of the suspension.The rheology of the concentrated dispersion is of considerable scientific and industrial interests and has been reviewed in a number of papers. Commonly, the shear yield stress (ry) is measured. The...
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