GATE (TF) Textile 2022 Question Paper Solution | GATE/2022/TF/60

Question 60 (Textile Technology & Fibre Science)

Reduction clearing process relates to

(A)Reduction of a vat dye to impart substantivity to cellulosic fibres
(B)Reduction of a sulphur dye to impart water solubility
(C)Removal of excess disperse dye from the surface of polyester fibres
(D)Neutralisation of residual sodium hypochlorite on the bleached fabric
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Frequently Asked Questions | FAQs

What is vat dye ?

Vat dye is a type of dye that is insoluble in water and must be reduced to a soluble form before it can be applied to fabric. This process is called “vatting” and involves soaking the fabric in a reducing agent, such as sodium hydrosulfite, which makes the dye soluble. The fabric is then immersed in the vat of dye and exposed to air, which oxidizes the dye and fixes it to the fabric. Vat dyes are known for their high level of lightfastness, meaning that they are resistant to fading from exposure to light. They are also resistant to washing and rubbing, making them ideal for use on fabrics that will be subjected to wear and tear.

What is sulphur dye ?

Sulfur dye is a type of dye that is used for coloring cellulose fibers, such as cotton and rayon. It is known for its high level of brightness and its low cost, making it a popular choice for dyeing cotton fabric, particularly for mass-produced textiles such as sheets, towels, and clothing. Sulfur dyes are made by reacting sulfides with aromatic compounds, producing a range of colors from yellow to black. The dyeing process is relatively simple and straightforward, making it a cost-effective option for high volume textile production. However, sulfur dyes can be less colorfast than other types of dyes, meaning that they are more prone to fading or losing their brightness over time.

What is disperse dye ?

Disperse dye is a type of dye that is used to color synthetic fibers, such as polyester, nylon, and acrylic. Unlike natural fibers like cotton and wool, synthetic fibers do not have a natural affinity for dyes, so special dyes must be used to color them. Disperse dyes are specifically designed for use on synthetic fibers, and they work by forming very fine particles that are dispersed evenly throughout the fibers. This allows for a high degree of colorfastness and a deep, vibrant color that is resistant to fading. The dyeing process for synthetic fibers with disperse dyes typically involves heating the fibers in a solution of the dye and a dispersing agent, which helps to distribute the dye evenly and prevent clumping.

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