Which of the following polymers is classified as a thermosetting plastic that cannot be repeatedly softened by heating once molded?

💡 Solution & Explanation

Bakelite is a synthetic thermosetting polymer formed by the condensation reaction of phenol and formaldehyde, creating extensive cross-linked networks that harden permanently upon heating. Polyethylene, polyvinyl chloride, and polystyrene are thermoplastic polymers that soften repeatedly when heated and harden upon cooling. Thermosetting resins are valued for their exceptional heat resistance and electrical insulation properties.