Question 41 (Textile Technology & Fibre Science)
In a dye identification test, a dyed fabric is immersed in an aqueous alkaline solution of a reducing agent. The colour of the dyed fabric changes and some dye bleeds out in the solution. The correct combination of the fabric and dye is
| (A) | Wool and acid dye |
| (B) | Polyester and disperse dye |
| (C) | Cotton and vat dye |
| (D) | Acrylic and basic dye |
[Show Answer]
Option C is correct
Frequently Asked Questions | FAQs
What is acid dye ?
An acid dye is a type of dye that is applied to textiles and fibers using an acidic dye bath and is typically used to color animal fibers like wool, silk and feathers. Unlike basic dyes, which are typically water-soluble, acid dyes are typically anionic, meaning they have a negative charge, and they form a bond with the fibers through ionic and hydrogen bonding. Acid dyes are known for their bright and intense colors, excellent colorfastness, and ability to produce a wider range of colors than basic dyes.
What is disperse dye ?
Disperse dyes are a type of dye that are used to color synthetic fibers such as polyester, nylon, and cellulosic fibers. They are named “disperse” because they are insoluble in water and are dispersed in a liquid medium as very small particles. Disperse dyes are applied to the fibers in a dispersed form, usually in the form of an aqueous suspension, and then diffused into the fibers through heat treatment. They are known for their bright, intense colors, good lightfastness, and excellent wash fastness, making them a popular choice for dyeing a wide range of synthetic textiles and fibers.
What is vat dye ?
Vat dyes are a type of dye that are used to color a variety of natural and synthetic fibers. They are called “vat” dyes because they are initially insoluble in water and must be reduced to a soluble form by a chemical process known as reduction before they can be applied to the fibers. The process of reduction typically involves the addition of a reducing agent to the dye, causing it to undergo a change in chemical structure and become water-soluble. Once the vat dye has been reduced, it can be applied to the fibers and then oxidized to re-form the original, insoluble dye molecule, which is strongly bound to the fibers. Vat dyes are known for their deep, rich colors, high colorfastness, and excellent lightfastness.
What is basic dye ?
Basic dyes are a type of dye that are used to color a variety of natural and synthetic fibers. They are called “basic” dyes because they are water-soluble cationic dyes that have a positive charge. Basic dyes bond to the fibers through ionic interactions between the positive charge of the dye molecule and the negatively charged fibers. Basic dyes are known for their good solubility, brightness, and lightfastness, and they are commonly used to color cellulosic fibers like cotton, rayon, and paper, as well as some synthetic fibers like nylon. Basic dyes are also used in a variety of other applications, including dyeing of leather, silk, and wool.