GATE (TF) Textile 2014 Question Paper Solution | GATE/2014/TF/25

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Why is acid dye used for wool?

Acid dyes are commonly used for dyeing wool due to their affinity for protein-based fibers, such as wool, as well as their excellent wash-fastness and light-fastness properties. Acid dyes are water-soluble dyes that contain acidic groups, such as sulfonic acid or carboxylic acid, which allow them to form ionic bonds with the positively charged amino acid groups present in wool fibers. This results in strong and permanent dye bonds, which are resistant to washing and light exposure, making them suitable for use on wool, which is known for its excellent ability to absorb and retain dyes.

Here are some reasons why acid dyes are specifically used for wool:

Affinity for protein fibers: Acid dyes have a high affinity for protein-based fibers, such as wool, due to the presence of acidic groups in their molecular structure. These acidic groups readily form ionic bonds with the positively charged amino acid groups present in wool fibers, resulting in strong dye-fiber interactions and excellent color uptake.

Wash-fastness: Acid dyes exhibit excellent wash-fastness, meaning that the dye molecules remain firmly attached to the wool fibers even after repeated washing or exposure to water. This is important for maintaining the colorfastness of the dyed wool, as wool garments and textiles are often subjected to frequent washing.

Light-fastness: Acid dyes are also known for their good light-fastness properties, which means that the colors they produce are resistant to fading or changing when exposed to light. This is particularly important for wool, as wool garments and textiles are often exposed to sunlight or other sources of light, and need to retain their color vibrancy even with prolonged light exposure.
Wide color range: Acid dyes are available in a wide range of colors, including bright and vibrant shades, which makes them suitable for a variety of woolen applications, from fashion apparel to home textiles. The wide color range of acid dyes allows for creative and versatile dyeing possibilities, making them popular for wool dyeing.

Ease of application: Acid dyes are relatively easy to apply in the dyeing process, as they are water-soluble and can be readily dissolved in water to form a dye bath. They can be applied to wool fibers through various dyeing techniques, such as immersion dyeing, hand painting, or spray dyeing, making them versatile and convenient for wool dyeing processes.

It’s important to note that proper dyeing techniques, including appropriate dye selection, dye concentration, temperature, and dyeing time, as well as proper rinsing and finishing processes, are crucial for achieving desired colorfastness and durability in wool dyeing. Following the manufacturer’s instructions and recommendations, as well as good dyeing practices, is important for obtaining optimal results when using acid dyes for wool.

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