---
title: "Thermosetting vs thermoplastics; polymers for ropes, utensils"
subject: "Engineering Chemistry"
chapter: 4
key: "semester_2/engineering_chemistry:thermo-nylon-teflon"
source: https://www.bctengineer.com/q/semester_2/engineering_chemistry/thermo-nylon-teflon
site: BCT Engineering
---

# Thermosetting vs thermoplastics; polymers for ropes, utensils

Engineering Chemistry · Chapter 4: Engineering Polymers

- Asked in: 2067 Chaitra, 2+3 marks
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_2/engineering_chemistry/thermo-nylon-teflon
- Whole chapter: https://www.bctengineer.com/md/semester_2/engineering_chemistry/chapter-4

## Question

Differentiate thermosetting and thermoplastics polymers. Write the name and the preparation of the organic polymers that are used for (i) Preparing ropes and socks (ii) Preparing non stick cooking utensils.

## Short answer

Thermoplastics soften on heating and can be remoulded; thermosets form permanent cross‑links. Nylon 6,6 (ropes/socks) is made by condensing hexamethylenediamine and adipic acid. Teflon (PTFE) for non‑stick utensils is produced by addition polymerisation of tetrafluoroethylene.

## Answer

#### Thermosetting vs thermoplastic 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 |

#### (i) Polymer for ropes and socks: Nylon 6,6
**Nylon 6,6** is a polyamide made by condensation polymerisation of hexamethylenediamine (6 carbons) and adipic acid (6 carbons) at about 250 °C under pressure:

n H₂N(CH₂)₆NH₂ + n HOOC(CH₂)₄COOH → [–NH(CH₂)₆NH–CO(CH₂)₄CO–]ₙ + 2n H₂O

The repeating unit has the amide (–CONH–) link. (Nylon 6 is made from caprolactam by ring-opening polymerisation.)

#### (ii) Polymer for non-stick cooking utensils: Teflon (PTFE)
**Teflon (PTFE, polytetrafluoroethylene)** is made by free-radical **addition polymerisation** of tetrafluoroethylene (TFE) using a persulphate initiator under pressure:

n CF₂=CF₂ → [–CF₂–CF₂–]ₙ

TFE itself is obtained by heating chlorodifluoromethane (CHClF₂) at 600–800 °C.

PTFE coating is non-stick because of the very low surface energy of the C–F bonds.

## Check yourself

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

1. Which polymer is used for ropes and socks and how is it made?
   A. Nylon 6,6, by condensation of hexamethylenediamine and adipic acid
   B. PTFE, by addition of CF2=CF2
   C. Bakelite, by condensation of phenol and HCHO
   D. PVC, by addition of vinyl chloride
   Answer: A. Nylon 6,6 is a polyamide with 2n H2O lost. (Key point: Polymer for ropes)

2. Which link is present in nylon 6,6?
   A. Ester –COO–
   B. Amide –CONH–
   C. Urethane –NH–CO–O–
   D. Ether –O–
   Answer: B. Diamine plus diacid gives amide links. (Key point: Link in nylon)

3. How is Teflon (PTFE) prepared?
   A. Condensation of phenol and HCHO
   B. Ring-opening of caprolactam
   C. Free-radical addition polymerisation of tetrafluoroethylene with persulphate under pressure
   D. Hydrolysis of silanes
   Answer: C. n CF2=CF2 gives [–CF2–CF2–]n. (Key point: Teflon)

4. Why is PTFE non-stick?
   A. It contains free OH groups that repel oil
   B. It is a conducting polymer
   C. It is highly cross-linked rubber
   D. The C–F bonds give a very low surface energy
   Answer: D. Low surface energy prevents food sticking. (Key point: Non-stick)

## 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
- [Thermoplastic vs thermosetting polymers; Bakelite, epoxy](https://www.bctengineer.com/question.md?key=semester_2%2Fengineering_chemistry%3Athermoplastic-thermosetting) — Engineering Chemistry, chapter 4
- [Biodegradable vs non-biodegradable polymers](https://www.bctengineer.com/question.md?key=semester_2%2Fengineering_chemistry%3Abiodeg-nonbiodeg-examples) — Engineering Chemistry, chapter 4, asked 2×
- [Non-biodegradable polymers and demerits](https://www.bctengineer.com/question.md?key=semester_2%2Fengineering_chemistry%3Anon-biodegradable) — Engineering Chemistry, chapter 4

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