Question

Compared to Cotton, the special feature of Wool is

• A. Moisture Regain
• B. Density
• C. Tenacity
• D. DFE

Hint:

Remember the unique characteristics of wool: \[ \begin{aligned} &\bullet\ \text{Surface Scales} &\bullet\ \textbf{Directional Frictional Effect (DFE)} &\bullet\ \text{Felting Property} &\bullet\ \text{Excellent Elastic Recovery} &\bullet\ \text{High Moisture Regain} \end{aligned} \] A commonly asked objective question is: \[ \boxed{ \text{DFE} \Longrightarrow \text{Wool} \Longrightarrow \text{Felting} } \] The Directional Frictional Effect is considered the most distinguishing property of wool among natural textile fibres.

Answer 1

The Correct Option is D

Concept: Textile fibres possess different physical and mechanical properties depending upon their chemical composition and internal structure. Wool is a natural protein fibre obtained from the fleece of sheep and is distinguished from cotton by several unique characteristics. Some important properties of wool are:
• High elasticity and resilience.
• Excellent warmth due to trapped air.
• Good moisture absorption.
• Presence of surface scales.
• Directional Frictional Effect (DFE). Among these, the Directional Frictional Effect (DFE) is a unique property of wool and is responsible for its felting behaviour.

Step 1: Understand the Directional Frictional Effect (DFE).
The surface of wool fibres is covered with overlapping cuticle scales. These scales offer \[ \boxed{ \text{Different friction in the root-to-tip and tip-to-root directions.} } \] This phenomenon is known as the \[ \boxed{\text{Directional Frictional Effect (DFE).}} \] Due to DFE,
• Wool fibres tend to move more easily in one direction than the other.
• Fibres become interlocked during mechanical action.
• This causes the process known as felting. Thus, DFE is considered one of the most distinctive properties of wool.

Step 2: Examine each option.
Option (A): Moisture Regain Although wool has a higher moisture regain than cotton, moisture regain is not a unique property of wool because many natural fibres absorb moisture. \[ \boxed{\text{Incorrect}} \] Option (B): Density Density varies among fibres but is not the distinguishing characteristic of wool. \[ \boxed{\text{Incorrect}} \] Option (C): Tenacity Cotton generally possesses higher tenacity than wool. Therefore, tenacity is not the special feature of wool. \[ \boxed{\text{Incorrect}} \] Option (D): DFE Directional Frictional Effect is a unique property produced by the scaly surface structure of wool fibres. It is responsible for felting and shrinking during washing. Hence, \[ \boxed{\text{Correct}} \]

Step 3: Write the final answer.
The special feature of wool, compared to cotton, is \[ \boxed{\text{Directional Frictional Effect (DFE).}} \] Therefore, \[ \boxed{\text{Option (D) is the correct answer.}} \]