Question

Which one is appropriate for the poly-ethyleneterephthalate?

• A. Softening temperature in the range of 30°C - 45°C
• B. $T_g$ is about 80°C
• C. Melting point is in the range of 400°C - 450°C
• D. $T_g$ of the crystalline zone is 80°C

Hint:

The $T_g$ of a material is the temperature below which it behaves as a brittle solid and above which it behaves as a soft, rubbery material.

Answer 1

The Correct Option is B

Step 1: Understanding Polyethylene Terephthalate (PET).
Polyethylene Terephthalate (PET) is a common thermoplastic polymer with well-defined thermal properties. The glass transition temperature ($T_g$) is one of the key thermal characteristics.

Step 2: Analysis of options.
- (A) Softening temperature in the range of 30°C - 45°C: This is too low for PET, as its $T_g$ is typically higher.
- (B) $T_g$ is about 80°C: The glass transition temperature for PET is around 80°C, which is the correct answer.
- (C) Melting point is in the range of 400°C - 450°C: PET has a high melting point, but this is not the $T_g$ value.
- (D) $T_g$ of the crystalline zone is 80°C: $T_g$ is not exclusive to the crystalline zone but applies to the material as a whole.

Step 3: Conclusion.
The correct answer is (B), as PET's $T_g$ is around 80°C, making it the appropriate choice.