Describe how the structure of a thermosetting polymer makes it suitable for use in electrical plug casings, which must remain rigid and not melt when they become hot.

Cambridge International IGCSE Chemistry (0620) — 11.8 Polymers · Describe · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Electrical plug casings are made from thermosetting polymers. These casings must withstand the heat generated during normal use without softening or deforming.

Model answer (4 marks)

Thermosetting polymers contain cross‑links between chains, forming a permanent rigid network. The cross‑links prevent the chains from moving past one another, so the material does not soften or melt when heated. This heat‑resistant, rigid structure makes it suitable for electrical plug casings that must remain solid when they become hot.

Examiner tips

  • Use the word "cross‑links" and explain they lock chains in place
  • Mention that the network is permanent and prevents softening
  • Show that the material does not melt, only remains rigid
  • Link this property to safety in hot electrical applications

Common mistakes

  • Confusing thermosetting with thermoplastic behaviour
  • Forgetting to state that the network is permanent
  • Failing to mention that the material does not melt

Mark scheme (4 marks)

  1. Thermosetting polymers have cross-links between polymer chains
  2. The cross-links hold the structure permanently in a rigid network / prevent chains from moving
  3. The structure does not soften or melt when heated
  4. This rigid, heat-resistant structure makes it safe / suitable for use where heat is generated / as an electrical casing

Key terms in this question

thermosetting polymer

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