GATE (TF) Textile 2014 Question Paper Solution | GATE/2014/TF/07

Question 07 (Textile Engineering & Fibre Science)

The DP of viscose fibre is approximately

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Frequently Asked Questions | FAQs

What is the degree of polymerization?

The degree of polymerization(DP) refers to the number of repeating units or monomers that are chemically bonded together to form a polymer chain. It is a measure of the size or length of a polymer chain, and it is often denoted by the symbol “n”.
The degree of polymerization is an important parameter that affects the properties of a polymer, such as its molecular weight, physical properties, and processing behavior.
In general, a higher degree of polymerization means a longer polymer chain with more repeating units, resulting in a higher molecular weight and a larger polymer size. Conversely, a lower degree of polymerization means a shorter polymer chain with fewer repeating units, resulting in a lower molecular weight and a smaller polymer size.

The degree of polymerization can be controlled during the polymerization process by adjusting various factors such as the concentration of monomers, the reaction time, the temperature, and the type of catalyst or initiator used. It can also be determined experimentally using techniques such as gel permeation chromatography (GPC) or by measuring the viscosity or other physical properties of the polymer.

The degree of polymerization is an important parameter in polymer science and engineering, as it can significantly influence the properties and performance of polymers in various applications, including plastics, fibers, coatings, adhesives, and more.

What is the polymer structure of viscose rayon?

Viscose rayon, also known as rayon or viscose, is a type of synthetic fiber that is derived from natural cellulose, typically from wood pulp. The polymer structure of viscose rayon is a linear polymer with a chemical structure that consists of repeating units of cellulose, which are linked together through covalent bonds.
The process of producing viscose rayon involves several steps. First, cellulose is chemically treated with caustic soda (sodium hydroxide) to form a compound called alkali cellulose. This alkali cellulose is then treated with carbon disulfide to form cellulose xanthate. The cellulose xanthate is dissolved in an aqueous solution, and this solution is then spun into a coagulating bath containing sulfuric acid, which regenerates the cellulose from the cellulose xanthate. The resulting regenerated cellulose is then washed, bleached, and further processed into viscose rayon fibers.

The polymer structure of viscose rayon is similar to that of natural cellulose, which is a linear polymer made up of repeating units of glucose linked together by β(1→4) glycosidic bonds. However, the chemical treatment during the production of viscose rayon introduces additional chemical groups, such as hydroxyl and ester groups, which can affect the properties of the fiber, such as its strength, flexibility, and solubility.

It’s worth noting that the structure of viscose rayon can vary depending on the specific manufacturing process, as different variations of viscose rayon, such as high-wet-modulus (HWM) rayon, high-tenacity rayon, and high-absorbency rayon, can have slightly different chemical structures and properties to suit different applications.

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