Question

Which statement regarding polymers is not correct?

• A. Elastomers have polymer chains held together by weak intermolecular forces.
• B. Fibers possess high tensile strength.
• C. Thermoplastic polymers are capable of repeatedly softening and hardening on heating and cooling respectively.
• D. Thermosetting polymers are reusable.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Polymers are classified into four main categories based on their mechanical properties and the nature of intermolecular forces: Elastomers, Fibers, Thermoplastics, and Thermosetting polymers.
Step 2: Detailed Explanation:
Evaluation of Option (1):
Elastomers (like rubber) have weak intermolecular forces (Van der Waals forces). This allows the chains to be stretched easily and return to their original shape when the force is removed.
The statement is correct.

Evaluation of Option (2):
Fibers (like Nylon-6,6 or Terylene) have strong intermolecular forces such as hydrogen bonding or dipole-dipole interactions. This leads to high tensile strength and high modulus.
The statement is correct.

Evaluation of Option (3):
Thermoplastic polymers (like Polythene or PVC) have forces of intermediate strength. They soften on heating and harden on cooling. This process is physical and can be repeated many times.
The statement is correct.

Evaluation of Option (4):
Thermosetting polymers (like Bakelite or Melamine) undergo extensive cross-linking in the mold during heating. This creates a rigid 3D network. Once set, they cannot be melted or remolded by heating again. They decompose rather than soften. Therefore, they are not reusable.
The statement is incorrect.
Step 3: Final Answer:
The incorrect statement is (4).