Answer: Set permanently on heating and cannot be reshaped.
- A Set permanently on heating and cannot be reshaped
- B Melt and flow freely on heating, like thermoplastics
- C Dissolve largely in water once cross-linked
- D Usually remain optically transparent after curing
Correct answer: A. Set permanently on heating and cannot be reshaped
Explanation: Thermosetting polymers (like Bakelite, epoxy) form irreversible cross-links on curing and cannot be remelted.
Addition polymerisation simply links monomers containing a double bond with nothing left over, while condensation polymerisation joins two different monomers through a reaction (often forming an ester or amide bond) that releases a small molecule like water at each step.
Concept context
Large molecules made of repeating monomer units. Covers addition and condensation polymerisation, natural and synthetic polymers (nylon, PVC, Bakelite, natural rubber), and their real-world industrial applications.