Question

Mercerisation of Cotton fabrics will result in

• A. Decrease in Tensile strength and increase in Air-permeability
• B. Increase in Crease recovery angle and increase in Bending rigidity
• C. Increase in Drapability and decrease in Bending rigidity
• D. Increase in Tensile strength and decrease in Crease recovery angle

Hint:

Remember the major effects of mercerisation: \[ \begin{aligned} &\bullet\ \text{Higher Lustre} &\bullet\ \text{Better Dye Uptake} &\bullet\ \text{Higher Tensile Strength} &\bullet\ \textbf{Higher Drapability} &\bullet\ \textbf{Lower Bending Rigidity} &\bullet\ \text{Improved Dimensional Stability} \end{aligned} \] A useful memory trick is: \[ \boxed{ \text{Mercerisation} \Longrightarrow \text{Soft Fabric} \Longrightarrow \text{Better Drape} \Longrightarrow \text{Lower Bending Rigidity} } \] Mercerisation is one of the most frequently asked chemical finishing processes in textile engineering examinations.

Answer 1

The Correct Option is C

Concept: Mercerisation is a chemical treatment given to cotton fibres or fabrics using a concentrated solution of sodium hydroxide (\(\mathrm{NaOH}\)), generally under controlled tension. The process was discovered by John Mercer in 1844 and is widely used to improve the appearance and performance of cotton textiles. During mercerisation, the cotton fibres swell, their cross-section changes from a flattened ribbon-like shape to a nearly circular shape, and the internal molecular arrangement becomes more uniform. As a result, several physical properties of cotton are significantly improved.

Step 1: Effects of mercerisation on cotton.
Mercerisation produces the following improvements: \[ \begin{aligned} &\bullet\ \text{Increases lustre,} &\bullet\ \text{Improves dye absorption,} &\bullet\ \text{Increases tensile strength (under tension),} &\bullet\ \text{Improves dimensional stability,} &\bullet\ \text{Increases softness and flexibility,} &\bullet\ \text{Improves drapability.} \end{aligned} \] Since the fabric becomes softer and more flexible after treatment, its resistance to bending decreases. Therefore, \[ \boxed{ \text{Mercerisation} \Longrightarrow \text{Higher Drapability} \Longrightarrow \text{Lower Bending Rigidity} } \]

Step 2: Examine each option.
Option (A): Decrease in Tensile strength and increase in Air-permeability Mercerisation generally increases the tensile strength of cotton when carried out under tension. Hence this statement is incorrect. \[ \boxed{\text{Incorrect}} \] Option (B): Increase in Crease recovery angle and increase in Bending rigidity Although crease recovery may improve slightly after certain finishing treatments, mercerisation does not increase bending rigidity. \[ \boxed{\text{Incorrect}} \] Option (C): Increase in Drapability and decrease in Bending rigidity Mercerisation softens the fabric and improves its flexibility, thereby increasing drapability while reducing bending rigidity. \[ \boxed{\text{Correct}} \] Option (D): Increase in Tensile strength and decrease in Crease recovery angle Although tensile strength increases, mercerisation does not characteristically decrease the crease recovery angle. \[ \boxed{\text{Incorrect}} \]

Step 3: Write the final answer.
Hence, mercerisation of cotton fabrics results in \[ \boxed{ \text{Increase in Drapability and Decrease in Bending Rigidity.} } \] Therefore, \[ \boxed{\text{Option (C) is the correct answer.}} \]