Question

Cellulosic textiles can be permanently heat set (Assertion A). Heat setting can be performed on thermoplastic polymers which when heated under strictly controlled temperatures soften and can be made to take any shape. When cooled, they will retain the desired shape of configuration (Reason R).

• A. Both (A) and (R) are correct and (R) is the correct explanation of (A)
• B. Both (A) and (R) are correct but (R) is not the correct explanation of (A)
• C. (A) is correct but (R) is not correct
• D. (A) is not correct but (R) is correct

Hint:

Always ensure that the reason and assertion are directly related when evaluating such questions.

Answer 1

The Correct Option is C

Step 1: Concept
Heat setting in textiles involves subjecting the fabric to heat and pressure to permanently alter its shape or dimensions. This process can be applied to both cellulosic and thermoplastic polymers.

Step 2: Meaning
Assertion A: Cellulosic textiles can be permanently heat set. Reason R: Heat setting on thermoplastic polymers involves softening the material under controlled temperatures, allowing it to take a new shape that is retained upon cooling.

Step 3: Analysis
1. Cellulosic Textiles and Heat Setting: - Cellulosic textiles are primarily made from natural fibers like cotton or rayon. - These materials do not typically undergo heat setting in the same way as thermoplastics because they do not soften when heated to the temperatures required for such a process. 2. Thermoplastic Polymers and Heat Setting: - Thermoplastic polymers, such as polyethylene or polypropylene, can be permanently shaped by heating them to their melting point. - When cooled, these materials retain the new shape due to molecular rearrangement at the molecular level. 3. Evaluation of Assertion A and Reason R: - The assertion states that cellulosic textiles can be heat set permanently. This is generally not true for most cellulosic fibers as they do not soften or change their structure in the same way thermoplastics do. - The reason explains a process applicable to thermoplastic polymers, which does not directly apply to cellulosic textiles.

Step 4: Conclusion
The assertion about cellulosic textiles being permanently heat set is incorrect. However, the explanation provided for thermoplastic polymers (reason R) is accurate but not relevant to cellulosic textiles. Final Answer: (C)