As we all know, there are five main types of inks used for digital printing of textiles. Reactive, acidic, direct dispersion, sublimation and pigment inks. Each ink has its associated printing, curing and fixing methods. Except for pigments, all the above substances are fixed by chemical bonding with fabric fibers.
The purpose of this article is to understand how digital textile pigment inks are used with fabrics, and to understand the impact of all variables on the process. Before we start, let’s start with the quality standards of printed fabrics.
The performance of printed fabrics (by any means) is evaluated by several important criteria, such as color fastness, washing fastness, wet and dry rubbing fastness, perspiration fastness, hand feel and safety related to colorants and ink formulations. Let’s learn about the performance of digital textile pigment ink in these aspects. These inks have excellent color fastness to fading due to the use of pigments that are highly resistant to fading. The latest development of ink formulation provides highly reliable performance for washing fastness and dry and wet rubbing fastness. Pigment inks also provide excellent fastness to perspiration. The only drawback of pigment printed fabrics is that they have a slight touch or feel in the printed area.
Fix the pigment ink by bonding the pigment to the fabric. Pigment inks contain binders, usually polymer based compounds. In the fixation process, the polymer is heated to a certain temperature, plasticized (converted to semi-solid), and then formed a bond between the fabric fiber and the pigment particles in the ink. This creates a physical bond between the pigment particles and the fabric to some extent. This adhesive plays a key role in the performance of pigment inks. From ink stability, nozzle spray performance, preventing print head blockage to ensuring ink fastness on the fabric, with a minimum touch, it depends on the adhesive. Managing all this is a daunting challenge, which is why it is difficult to find a good pigment ink.
Interestingly, this combination process gives pigment inks some unique advantages. Most importantly, the curing process can be accomplished by heating the printed fabric. The right temperature for enough time is all you need to fix the ink to the fabric. This saves a lot of water for other printing technologies. In addition, even with mixed ingredients, you can use pigment ink to print on various fabrics. This opens up the possibility of printing blends digitally. In addition, pigment inks are widely used in some applications that do not want to treat fabrics after printing.
From the perspective of printing process, PFP fabric needs to be started. “PFP” or “prepared for print” fabrics are usually treated to remove various oils, waxes, sizing agents, etc. used in various stages of manufacturing. These chemicals interact and prevent the correct fixation of the ink. A large part of the industry precoats fabrics before printing. This is what the ideal printing process looks like.
The digital textile pigment ink should be able to print directly on the fabric without any pretreatment. This is an absolute fact, but it does not really explain the printed results. It would be interesting to understand the role of preconditioning. As you know, pigment inks are mainly used for printing on natural fiber fabrics. When printed directly on the fabric, the pigment particles are absorbed by the porous fibers of the fabric. Therefore, although the results look good when printing, they will fade once the printing is cured. This is the function of pretreatment.
Pretreatment chemicals depend on the chemical basis and perform various functions. They mainly help to keep the ink on the surface of the fabric. This prevents ink from being absorbed into the fibers. Keeping more ink on the fibers helps the ink produce bright colors. Some pretreatments go further, helping to improve the fixation of the ink on the fabric. So as to improve the ink washing, wet friction and dry running fastness. In addition, if the fabric is precoated, you can use less ink and print fewer times. This helps increase productivity and reduce ink costs.
I hope this article can clarify the working principle of digital textile pigment ink. If you are interested in learning more about our series of digital textile pigment inks, please feel free to contact Sublicool.