Ques. 1NEET (UG) 2022
Which statement regarding polymers is not correct?
- Elastomers have polymer chains held together by weak intermolecular forces
- Fibers possess high tensile strength
- Thermoplastic polymers are capable of repeatedly softening and hardening on heating and cooling respectively
- Thermosetting polymers are reusable
Answer
(4) Thermosetting polymers are reusable
Solution
As per NCERT, elastomers are rubber-like solids whose chains are held together by the weakest intermolecular forces, and fibres have strong intermolecular forces such as hydrogen bonds, which give them high tensile strength; so (1) and (2) are correct.
Thermoplastics are linear or slightly branched polymers that soften on heating and harden on cooling repeatedly, so (3) is also correct.
Thermosetting polymers, however, are cross-linked or heavily branched; on heating they undergo extensive cross-linking in moulds and become infusible, which is why they cannot be reused.
Statement (4) is not correct.
Answer: (4)
Out of syllabus