Which of the following is an example of a heavily cross-linked polymer?
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → Melamine
In a cross-linked (network) polymer, the long chains are joined to one another by strong bonds in three dimensions. Such polymers are hard and rigid, and once set they do not soften on heating, so they are thermosetting plastics.
Why the other options are incorrect
Option (2) Polythene — Incorrect. Its chains are linear or branched, not joined to one another; it softens on heating (thermoplastic).
Option (3) Nylon — Incorrect. A synthetic fibre made of long linear chains (a polyamide).
Option (4) Polyester — Incorrect. A synthetic fibre such as terylene, also made of linear chains.