---
title: "Thermoplastic vs thermosetting polymers; Bakelite, epoxy"
subject: "Engineering Chemistry"
chapter: 4
key: "semester_2/engineering_chemistry:thermoplastic-thermosetting"
source: https://www.bctengineer.com/q/semester_2/engineering_chemistry/thermoplastic-thermosetting
site: BCT Engineering
---

# Thermoplastic vs thermosetting polymers; Bakelite, epoxy

Engineering Chemistry · Chapter 4: Engineering Polymers

- Asked in: 2070 Magh, 3+2 marks
- Video: [Thermosets and Thermoplastics](https://www.youtube.com/watch?v=lNS7TwWmlrg) — Fantastic Plastics!
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_2/engineering_chemistry/thermoplastic-thermosetting
- Whole chapter: https://www.bctengineer.com/md/semester_2/engineering_chemistry/chapter-4

## Question

How do thermoplastic polymers differ from thermosetting polymers? Give the applications of Bakelite and Epoxy resins.

## Short answer

Thermoplastics soften on heating and can be remoulded; thermosets harden permanently and cannot be reshaped. Bakelite: electrical switches, handles. Epoxy resins: adhesives, coatings, glass-reinforced laminates.

## Answer

#### Thermoplastic vs thermosetting polymers
| Point | Thermoplastic | Thermosetting |
|---|---|---|
| Structure | Linear or slightly branched chains | Cross-linked 3-D network |
| Effect of heat | Softens on heating, hardens on cooling (reversible) | Sets permanently on heating; does not soften again |
| Moulding | Can be remoulded and recycled | Cannot be remoulded |
| Solubility | Soluble in some organic solvents | Insoluble and infusible |
| Mechanical nature | Soft, flexible, less strong | Hard, rigid, strong, brittle |
| Examples | Polyethylene, PVC, nylon, polystyrene | Bakelite, epoxy resin, melamine–formaldehyde |

#### Applications of Bakelite
Bakelite is hard, rigid, heat resistant, a good electrical insulator, and does not soften on reheating. Uses:
- Electrical switches, plugs, sockets, switch-boards and insulating parts of computers and appliances.
- Handles of cookers, pans and irons.
- Laminates (e.g. phenolic printed circuit boards), brake linings, and adhesive for plywood.
- Telephone cases, radio cabinets, billiard balls, gears and bearings.

#### Applications of epoxy resins
- Strong adhesives (Araldite) for metal, glass and ceramics.
- Surface coatings, paints and protective linings for tanks and pipes.
- Electrical insulation and potting of electronic components; glass-epoxy laminates for printed circuit boards.
- Matrix of fibre-reinforced composites (aircraft, boats, sports goods).
- Flooring, castings, moulds and tools.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. How does the structure of thermoplastics differ from thermosetting polymers?
   A. Thermoplastics are linear/slightly branched; thermosets are cross-linked 3-D networks
   B. Thermoplastics are cross-linked; thermosets are linear
   C. Both are 3-D networks
   D. Both are linear but differ in colour
   Answer: A. Linear chains soften on heating; cross-linked networks set permanently. (Key point: Structure)

2. Which statement about reheating is correct?
   A. Thermosets can be remoulded and recycled; thermoplastics cannot
   B. Thermoplastics soften and can be remoulded; thermosets do not soften again
   C. Both soften reversibly
   D. Neither is affected by heat
   Answer: B. Thermoplastic softening is reversible; thermosetting cure is permanent. (Key point: Effect of heat)

3. Which set contains only thermosetting polymers?
   A. Polyethylene, PVC, nylon
   B. Bakelite, polystyrene, PVC
   C. Bakelite, epoxy resin, melamine–formaldehyde
   D. Nylon, epoxy, polyethylene
   Answer: C. Bakelite, epoxy and melamine–formaldehyde are thermosets; polyethylene, PVC, nylon are thermoplastics. (Key point: Examples)

4. Which property makes Bakelite suitable for switches, plugs and cooker handles?
   A. It is soft and conducts electricity
   B. It melts easily for recycling
   C. It is a biodegradable fibre
   D. It is hard, heat resistant and a good electrical insulator
   Answer: D. Bakelite is rigid, does not soften on reheating and insulates electrically. (Key point: Bakelite use)

## Related in Engineering Chemistry

- [Thermosetting vs thermoplastics; Bakelite](https://www.bctengineer.com/question.md?key=semester_2%2Fengineering_chemistry%3Athermosetting-bakelite) — Engineering Chemistry, chapter 4
- [Thermosetting vs thermoplastics; polymers for ropes, utensils](https://www.bctengineer.com/question.md?key=semester_2%2Fengineering_chemistry%3Athermo-nylon-teflon) — Engineering Chemistry, chapter 4
- [Biodegradable polymers; epoxy resin and polystyrene](https://www.bctengineer.com/question.md?key=semester_2%2Fengineering_chemistry%3Abiodeg-epoxy-polystyrene) — Engineering Chemistry, chapter 4
- [Thermosetting polymer; uses of epoxy resin](https://www.bctengineer.com/question.md?key=semester_2%2Fengineering_chemistry%3Athermosetting-epoxy-uses) — Engineering Chemistry, chapter 4
- [Monomers of polyurethane, nylon 6,6, Bakelite, epoxy](https://www.bctengineer.com/question.md?key=semester_2%2Fengineering_chemistry%3Amonomers-polymers) — Engineering Chemistry, chapter 4
- [Preparation and applications of Bakelite, polyurethanes](https://www.bctengineer.com/question.md?key=semester_2%2Fengineering_chemistry%3Abakelite-polyurethane-prep) — Engineering Chemistry, chapter 4