---
title: "Polystyrene and PTFE preparation and applications"
subject: "Engineering Chemistry"
chapter: 4
key: "semester_2/engineering_chemistry:polystyrene-ptfe"
source: https://www.bctengineer.com/q/semester_2/engineering_chemistry/polystyrene-ptfe
site: BCT Engineering
---

# Polystyrene and PTFE preparation and applications

Engineering Chemistry · Chapter 4: Engineering Polymers

- Asked in: 2071 Magh, 2.5+2.5 marks
- Video: [Addition Polymers Crash Course: HDPE, LDPE, PVC, Polystyrene and PTFE // HSC Chemistry](https://www.youtube.com/watch?v=8jjPDZxbbe4) — Science Ready
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_2/engineering_chemistry/polystyrene-ptfe
- Whole chapter: https://www.bctengineer.com/md/semester_2/engineering_chemistry/chapter-4

## Question

What are polystyrene and PTFE? How can they be prepared? What are the main reasons for their wide range of applications?

## Short answer

Polystyrene is an addition polymer of styrene, prepared by free-radical polymerization; it is rigid, transparent, cheap, and used for packaging, cups, and insulation. PTFE is the addition polymer of tetrafluoroethylene, prepared under pressure; it is chemically inert, heat-resistant, low-friction, and used for non-stick cookware, gaskets, and wire insulation.

## Answer

**Polystyrene** (PS) is an addition polymer of styrene (vinylbenzene), C₆H₅CH=CH₂. **PTFE** (Teflon) is the addition polymer of tetrafluoroethylene, CF₂=CF₂.

**Preparation**
- Polystyrene: free-radical polymerisation of styrene with benzoyl peroxide as initiator, in bulk, solution or suspension at about 80–100 °C:
  n C₆H₅CH=CH₂ → [–CH(C₆H₅)–CH₂–]ₙ
- PTFE: n CF₂=CF₂ → [–CF₂–CF₂–]ₙ using ammonium persulphate initiator under pressure.

**Reasons for wide applications**
- *Polystyrene:* rigid, transparent, light, cheap, easy to mould, good electrical insulator and moisture resistant. Used for packaging, disposable cups, toys, CD cases, appliance housings, and expanded form (thermocol) for insulation and cushioning.
- *PTFE:* extremely inert to chemicals, stable to heat (up to 260 °C), very low friction, non-stick and a superb electrical insulator. Used for non-stick cookware, gaskets, bearings, wire insulation and chemical plant lining.

## Check yourself

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

1. How is polystyrene prepared?
   A. Free-radical polymerisation of styrene with benzoyl peroxide
   B. Condensation of phenol
   C. Ring-opening
   D. Using persulphate on TFE
   Answer: A. Styrene with benzoyl peroxide at about 80-100 C. (Key point: Polystyrene preparation)

2. PTFE is made from which monomer?
   A. CF2=CF2
   B. C6H5CH=CH2
   C. CH2=CHCl
   D. HCHO
   Answer: A. n CF2=CF2 gives PTFE with persulphate initiator under pressure. (Key point: PTFE preparation)

3. What is thermocol?
   A. Expanded polystyrene used for insulation and cushioning
   B. PTFE foam
   C. Bakelite sheet
   D. Nylon fibre
   Answer: A. Expanded form of polystyrene. (Key point: Expanded polystyrene)

4. Which property explains PTFE use in non-stick cookware?
   A. Very low friction and chemical inertness
   B. High friction
   C. Solubility
   D. Brittleness
   Answer: A. Inert, heat stable to 260 C and non-stick. (Key point: PTFE reason)

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