Question

When the rate of cooling is increased during the solidification process, the glass transition temperature of a polymer \(\underline{\hspace{2cm}}\).

• A. decreases
• B. increases
• C. stays unaltered
• D. shows a non-monotonic dependence

Hint:

A faster cooling rate increases the glass transition temperature by restricting polymer chain mobility.

Answer 1

The Correct Option is B

The glass transition temperature (Tg) of a polymer increases when the cooling rate is increased during solidification. This occurs because faster cooling limits the mobility of the polymer chains, resulting in a more rigid structure and a higher Tg.

Step 1: Understand the relationship between cooling rate and Tg.
As the cooling rate increases, the polymer chains do not have enough time to move and arrange themselves into a more relaxed configuration, leading to a higher glass transition temperature. This is because the polymer remains in a less ordered state.

Step 2: Analyze the options.
- (A) decreases: This is incorrect because an increased cooling rate raises the Tg, not lowers it.
- (B) increases: This is correct because faster cooling increases the glass transition temperature.
- (C) stays unaltered: This is incorrect, as the Tg is affected by the cooling rate.
- (D) shows a non-monotonic dependence: This is incorrect, as the Tg typically increases with an increase in cooling rate.

Step 3: Conclusion.
The glass transition temperature increases with a faster cooling rate, as the polymer chains are restricted from rearranging into a relaxed state.

Final Answer: \text{(B) increases}