Question 52 (Textile Engineering & Fibre Science)
Consider the following assertion [a] and reason [r] and choose the correct alternative from amongst A, B, C and D.
[a] In dyeing of polyester with disperse dyes, it is easier to obtain dark shades with solvent dyeing method than with aqueous dyeing method.
[r] The partition coefficient (D[f]/D[s]) of disperse dyes is much lower in aqueous medium than in a solvent.
|(A)||[a] is right and [r] is wrong|
|(B)||[a] is right and [r] is right|
|(C)||[a] is wrong and [r] is wrong|
|(D)||[a] is wrong and [r] is right|
Frequently Asked Questions | FAQs
What is meant by disperse dye?
Disperse dyes are a class of synthetic dyes that are insoluble in water and have low solubility in most organic solvents. They are typically used to dye synthetic fibers such as polyester, nylon, and acetate.
Disperse dyes are composed of small molecules that are able to penetrate the surface of the synthetic fibers and become dispersed within the fiber structure. The dyeing process typically involves heating the fiber and the disperse dye together in a solvent or carrier, such as water or an organic solvent, which helps to promote the penetration of the dye molecules into the fiber.
Disperse dyes are known for their high color strength, meaning they can produce vibrant and intense colors. They are also resistant to fading and washing, making them ideal for use in textiles that are exposed to sunlight or frequent washing. However, they may not be suitable for natural fibers such as cotton or wool, as the dye molecules are unable to penetrate the natural fiber structure.
What is partition coefficient?
Partition coefficient is a measure of how a solute distributes itself between two immiscible phases, typically a hydrophobic organic solvent and an aqueous phase. It is defined as the ratio of the concentration of a solute in one phase to its concentration in the other phase at equilibrium, when the two phases are in contact with each other.
The partition coefficient is a thermodynamic property that reflects the relative affinity of a solute for the two phases. It is influenced by factors such as the chemical nature of the solute and the solvent, temperature, and pressure. The partition coefficient is often used to predict the behavior of a solute in a specific system and to design separation processes, such as liquid-liquid extraction and chromatography.
In chemistry, the most commonly used partition coefficient is the octanol-water partition coefficient (Kow), which is the ratio of the concentration of a solute in octanol (a hydrophobic organic solvent) to its concentration in water at equilibrium. The Kow value can provide information on the lipophilicity (fat solubility) of a compound and can be used to predict its distribution in biological systems, such as its ability to cross cell membranes and accumulate in fatty tissues.