Which of the following polymers is not a thermoplastic polymer?

Thermoplastic polymers are linear or slightly branched long chain molecules capable of repeatedly softening on heating and hardening on cooling. Examples include polyethylene, polystyrene, and polyvinyls.

Thermosetting polymers are cross-linked or heavily branched molecules, which on heating undergo extensive cross-linking in moulds and again become infusible. These cannot be reused. Examples include bakelite and urea-formaldehyde resins.

Therefore, bakelite is a thermosetting polymer and not a thermoplastic polymer.

Answer: Bakelite