GATE (TF) Textile 2010 Question Paper Solution | GATE/2010/TF/30

Thickeners are an essential component of printing paste used in textile printing. They are used to provide viscosity and to control the flow of the printing paste onto the fabric. There are several types of thickeners used in textile printing, but the choice of thickener depends on the type of printing process and the desired printing results. Some common types of thickeners suitable for textile printing are:
Sodium alginate: This is the most widely used thickener in textile printing, particularly for cotton and other cellulose fibers. Sodium alginate thickener is derived from seaweed and has excellent thickening properties, good color yield, and wash fastness. It is suitable for both hand screen printing and machine printing.
Guar gum: This thickener is derived from the seeds of the guar plant and is used for printing on cotton, silk, and other fibers. Guar gum thickener provides excellent viscosity and has good resistance to high temperatures. It is commonly used in reactive dye printing and discharge printing.
Carboxymethyl cellulose (CMC): CMC is a water-soluble thickener that provides good viscosity and stability to printing paste. It is used for printing on synthetic fibers such as polyester, nylon, and acrylic. CMC thickener is commonly used in digital printing, as it provides excellent color yield and sharpness.
Acrylic thickeners: These are synthetic thickeners that provide good stability and viscosity to printing paste. They are used for printing on a wide range of fibers, including cotton, silk, wool, and synthetic fibers. Acrylic thickeners have good resistance to high temperatures and are commonly used in pigment printing.
Polyvinyl alcohol (PVA): PVA is a water-soluble polymer that provides excellent viscosity

In pigment printing, a fixer is a chemical substance that is used to fix or bind the pigments onto the fabric surface. The function of the fixer in pigment printing is to improve the color fastness of the printed design by creating a strong bond between the pigment and the fabric.
Pigments used in textile printing are insoluble particles that are not able to penetrate into the fabric fibers, unlike dyes. Therefore, they need to be fixed on the fabric surface to prevent the pigments from rubbing off or washing out during use and laundering.
The fixer works by creating a chemical bond between the pigment and the fabric surface. It can react with the functional groups on the fabric surface to form covalent or ionic bonds, depending on the type of fixer used. This bond is strong enough to prevent the pigment from being removed from the fabric during washing or rubbing.
The fixer is typically applied to the printed fabric after the pigment has been applied. It is usually added to the printing paste or applied as a separate post-printing treatment. The fabric is then dried and cured at high temperatures to ensure that the pigment and fixer are fully bonded to the fabric.
The use of a fixer in pigment printing is essential for achieving good color fastness and durability of the printed design. Without a fixer, the pigments would not be able to bond effectively with the fabric and would be prone to fading and rubbing off, resulting in a poor-quality print.

For printing on nylon fabric, acid dyes are the most suitable coloring chemicals. Acid dyes are water-soluble dyes that are used to dye protein fibers such as wool, silk, and nylon. Nylon is a synthetic polyamide fiber that has similar chemical properties to protein fibers, and therefore acid dyes can be used to dye and print on nylon fabric.
Acid dyes contain acidic groups such as sulfonic, carboxylic, or phosphoric groups that make them water-soluble and allow them to bond with the nylon fibers through ionic bonds. The acidic groups on the dye molecules are attracted to the basic amine groups on the nylon fibers, resulting in a strong and permanent bond.
In addition to good affinity and bonding with nylon, acid dyes also offer excellent color fastness properties, such as lightfastness, wash fastness, and perspiration fastness. They can produce a wide range of vibrant and intense colors on nylon fabric.
There are various types of acid dyes available for nylon fabric printing, such as premetallized acid dyes, 1:2 metal complex acid dyes, and 1:1 metal complex acid dyes. The choice of dye type depends on the desired color, shade, and printing method used.
Overall, acid dyes are the best option for coloring nylon fabric due to their excellent affinity, bonding, and color fastness properties.

Thickeners are an essential component of the pigment printing paste used in textile printing. The function of the thickener in pigment printing is to provide viscosity to the printing paste and control the flow of the pigment onto the fabric surface.
Pigment printing involves applying insoluble pigment particles onto the fabric surface, which do not penetrate into the fabric fibers like dyes do. Pigment printing paste consists of pigment particles, binder, and thickener, which are mixed together to form a paste with the desired viscosity and rheological properties.
The thickener in the pigment printing paste is added to provide the necessary viscosity and stability to the paste. The thickener ensures that the pigment particles are evenly dispersed in the paste and do not settle down during printing. It also prevents the paste from flowing too quickly or dripping off the fabric surface, which can result in a poor-quality print.
The choice of thickener for pigment printing depends on the type of fabric, printing process, and desired printing results. Common types of thickeners used in pigment printing include natural thickeners like gum arabic, synthetic thickeners like acrylics, and cellulose-based thickeners like sodium alginate.
In addition to providing viscosity and stability, the thickener in pigment printing also affects the hand and feel of the printed fabric. A thickener with a high viscosity can result in a stiff and rough feel on the fabric surface, while a thinner paste with a low viscosity can produce a soft and smooth feel.
In summary, the function of the thickener in pigment printing is to provide viscosity and stability to the printing paste, control the flow of the pigment onto the fabric surface, and affect the hand and feel of the printed fabric.